Composite material application for liquid rocket engines

NASA Technical Reports Server (NTRS)

Heubner, S. W.

1982-01-01

With increasing emphasis on improving engine thrust-to-weight ratios to provide improved payload capabilities, weight reductions achievable by the use of composites have become attractive. Of primary significance is the weight reduction offered by composites, although high temperature properties and cost reduction were also considered. The potential for application of composites to components of Earth-to-orbit hydrocarbon engines and orbit-to-orbit LOX/H2 engines was assessed. The components most likely to benefit from the application of composites were identified, as were the critical technology areas where developed would be required. Recommendations were made and a program outlined for the design, fabrication, and demonstration of specific engine components.

Probing Ligand Effects on the Redox Energies of [4Fe-4S] Clusters Using Broken-Symmetry Density Functional Theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Niu, Shuqiang; Ichiye, Toshiko

A central issue in understanding redox properties of iron-sulfur proteins is determining the factors that tune the reduction potentials of the Fe-S clusters. Recently, Solomon and coworkers have shown that the Fe-S bond covalency of protein analogs measured by %L, the percent ligand character of the Fe 3d orbitals, from ligand K-edge X-ray absorption spectroscopy (XAS) correlates with the electrochemical redox potentials. Also, Wang and coworkers have measured electron detachment energies for iron-sulfur clusters without environmental perturbations by gas-phase photoelectron spectroscopy (PES). Here the correlations of the ligand character with redox energy and %L character are examined in [Fe₄S₄L₄]2⁻ clustersmore » with different ligands by broken symmetry density functional theory (BS-DFT) calculations using the B3LYP functional together with PES and XAS experimental results. These gas-phase studies assess ligand effects independently of environmental perturbations and thus provide essential information for computational studies of iron-sulfur proteins. The B3LYP oxidation energies agree well with PES data, and the %L character obtained from natural bond orbital analysis correlates with XAS values, although it systematically underestimates them because of basis set effects. The results show that stronger electron-donating terminal ligands increase %Lt, the percent ligand character from terminal ligands, but decrease %Sb, the percent ligand character from the bridging sulfurs. Because the oxidized orbital has significant Fe-Lt antibonding character, the oxidation energy correlates well with %Lt. However, because the reduced orbital has varying contributions of both Fe-Lt and Fe-Sb antibonding character, the reduction energy does not correlate with either %Lt or %Sb. Overall, BSDFT calculations together with XAS and PES experiments can unravel the complex underlying factors in the redox energy and chemical bonding of the [4Fe-4S] clusters in iron-sulfur proteins.« less

Low-Cost Propellant Launch to LEO from a Tethered Balloon - Economic and Thermal Analysis

NASA Technical Reports Server (NTRS)

Wilcox, Brian H.; Schneider, Evan G.; Vaughan, David A.; Hall, Jeffrey L.

2010-01-01

This paper provides new analysis of the economics of low-cost propellant launch coupled with dry hardware re-use, and of the thermal control of the liquid hydrogen once on-orbit. One conclusion is that this approach enables an overall reduction in the cost-permission by as much as a factor of five as compared to current approaches for human exploration of the moon, Mars, and near-Earth asteroids.

Comparison of Low Earth Orbit and Geosynchronous Earth Orbits

NASA Technical Reports Server (NTRS)

Drummond, J. E.

1980-01-01

The technological, environmental, social, and political ramifications of low Earth orbits as compared to geosynchronous Earth orbits for the solar power satellite (SPS) are assessed. The capital cost of the transmitting facilities is dependent on the areas of the antenna and rectenna relative to the requirement of high efficiency power transmission. The salient features of a low orbit Earth orbits are discussed in terms of cost reduction efforts.

Aerodynamic investigations into various low speed L/D improvement devices on the 140A/B space shuttle orbiter configuration in the Rockwell International low speed wind tunnel (OA86)

NASA Technical Reports Server (NTRS)

Mennell, R. C.

1974-01-01

Tests were conducted to investigate various base drag reduction techniques in an attempt to improve Orbiter lift-to-drag ratios and to calculate sting interference effects on the Orbiter aerodynamic characteristics. Test conditions and facilites, and model dimensional data are presented along with the data reduction guidelines and data set/run number collation used for the studies. Aerodynamic force and moment data and the results of stability and control tests are also given.

Element Specific Spin and Orbital Moments in Fe1-x Vx Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Y.; Scheck, C; Bailey, W

2009-01-01

We present transmission-mode X-ray magnetic circular dichroism (XMCD) measurements of element-specific magnetic moments for Fe and V at the L2,3 edges in polycrystalline Fe1-xVx ultrathin films. We find that the orbital-to-spin moment ratio of Fe does not change within experimental error. The V XMCD is not very informative, and a nearly pure-spin type V impurity moment ({approx}1.0 {mu}{sub B}/atom, antiparallel to the Fe host moment) is assumed to match known magnetization data. Data are further reduced to a two-sublattice model and found to be compatible with known spectroscopic splitting g-factor data in the alloy. The results confirm that the verymore » low Gilbert damping, attained through the introduction of V into epitaxial Fe1-xVx films and found by ferromagnetic resonance (FMR), does not result from the reduction of orbital moment content in the alloy.« less

Flood warnings, flood disaster assessments, and flood hazard reduction: the roles of orbital remote sensing

NASA Technical Reports Server (NTRS)

Brakenridge, G. R.; Anderson, E.; Nghiem, S. V.; Caquard, S.; Shabaneh, T. B.

2003-01-01

Orbital remote sensing of the Earth is now poised to make three fundamental contributions towards reducing the detrimental effects of extreme floods. Effective Flood warning requires frequent radar observation of the Earth's surface through cloud cover. In contrast, both optical and radar wavelengths will increasingly be used for disaster assessment and hazard reduction.

Endoscopic transnasal approach for the treatment of isolated medial orbital blow-out fractures: a prospective study of preoperative and postoperative orbital volume change.

PubMed

Kim, KyoungHoon; Song, KyeongHo; Choi, SooJong; Bae, YongChan; Choi, ChiWon; Oh, HeungChan; Lee, JaeWoo; Nam, SuBong

2012-02-01

Endoscopic transnasal reduction is a safe and effective technique for the treatment of blow-out fractures of the medial orbital wall. However, because this approach does not use rigid permanent material for reconstruction of the fractured medial orbital wall, some degree of herniation of the orbital contents may occur after the intraethmoidal packing material is removed. The purpose of this study was to evaluate the change in orbital volume in patients with medial orbital wall fractures treated through an endoscopic transnasal approach. This study was a prospective analysis that includes 20 patients who underwent endoscopic transnasal reduction of medial orbital wall fractures between April 2007 and December 2008. Computer-assisted orbital volume measurements were made using axial computed tomography. The mean (standard deviation [SD]) volume increase was 2.00 (0.92) cm(3) and the mean (SD) dimension of the fractured orbital wall was 2.76 (0.83) cm(2). After endoscopic surgery, an average (SD) volume decrease of 2.15 (0.91) cm(3) was achieved with ethmoid sinus packing. After removal of the packing materials, 1.14 (0.78) cm(3) increase of the orbital volume was observed. The dimension of the orbital wall fracture significantly correlated with the increased preoperative orbital volume (P = 0.002, r = 0.609); the preoperative increase in the orbital volume also significantly correlated with volume relapse after removal of the packing (P = 0.023, r = 0.452). These findings suggest that in broad orbital wall fractures, reconstruction of the orbital wall by rigid materials or prolongation of the packing period should be considered, because orbital volume can increase again after packing removal, and may thus lead to postoperative complications.

Reusable aerospace system with horizontal take-off

NASA Astrophysics Data System (ADS)

Lozino-Lozinskii, G. E.; Shkadov, L. M.; Plokhikh, V. P.

1990-10-01

An aerospace system (ASS) concept aiming at cost reductions for launching facilities, reduction of ground preparations for start and launch phases, flexibility of use, international inspection of space systems, and emergency rescue operations is presented. The concept suggests the utilization of an AN-225 subsonic carrier aircraft capable of carrying up to 250 ton of the external load, external fuel tank, and orbital spacecraft. It includes a horizontal take-off, full reusable or single-use system, orbital aircraft with hypersonic characteristics, the use of an air-breathing jet engine on the first stage of launch, and the utilization of advanced structural materials. Among possible applications for ASS are satellite launches into low supporting orbits, suborbital cargo and passenger flights, scientific and economic missions, and the technical servicing of orbital vehicles and stations.

Residual diplopia in treated orbital bone fractures

PubMed Central

Balaji, S. M.

2013-01-01

Background: Residual diplopia (RD) is the main post-treatment complication of orbital bone fracture (OBF) reduction. The cause of RD is varied and often related to the degree of inflammation, surgical timing, graft requirement, and trauma to orbital musculature, fat, as well as nerves. The exact prevalence of these and the influence of these factors on RD is not widely reported in literature. Materials and Methods: This retrospective study was conducted from January 1, 2000 through December 31, 2011. Sixty nine patients fulfilling inclusion and exclusion criteria were enrolled in this study. The nature of the defect causing RD was identified. Demographics, nature of initial OBF, extent and type of treatment, and grafts were noted. Corrective surgeries were performed. Data entry and analysis were performed using SPSS. Descriptive statistics and Chi square tests were employed. P value ≤ 0.05 was taken as significant. Results: Inferior rectus muscle (71%) and other periorbital musculature (56.5%) was entrapped, leading to RD. Globe position abnormalities was observed in 52.1% of cases. Degree of inflammation, types of grafts (P = 0.000) were significantly related. Discussion: Preoperative swelling, musculature inflammation, and graft placement significantly influenced the surgical outcome of OBF. RD is related to these factors. Adequate control with OBF healing and remodeling needs to be considered while timing OBF. Author's modification with mesh and cartilage in secondary corrective surgery for RD provided an effective solution for immediate intervention. PMID:23662258

Laser-boosted lightcraft technology demonstrator

NASA Technical Reports Server (NTRS)

Antonison, M.; Myrabo, Leik; Chen, S.; Decusatis, C.; Kusche, K.; Minucci, M.; Moder, J.; Morales, C.; Nelson, C.; Richard, J.

1989-01-01

The ultimate goal for this NASA/USRA-sponsored 'Apollo Lightcraft Project' is to develop a revolutionary manned launch vehicle technology that can potentially reduce payload transport costs by a factor of 1000 below the space shuttle orbiter. The Rensellaer design team proposes to utilize advanced, highly energetic, beamed-energy sources (laser, microwave) and innovative combined-cycle (airbreathing/rocket) engines to accomplish this goal. This year's effort, the detailed description and performance analysis of an unmanned 1.4-m Lightcraft Technology Demonstrator (LTD) drone, is presented. The novel launch system employs a 100-MW-class ground-based laser to transmit power directly to an advanced combined-cycle engine that propels the 120-kg LTD to orbit, with a mass ratio of two. The single-stage-to-orbit (SSTO) LTD machine then becomes an autonomous sensor satellite that can deliver precise, high-quality information typical of today's large orbital platforms. The dominant motivation behind this study is to provide an example of how laser propulsion and its low launch costs can induce a comparable order-of-magnitude reduction in sensor satellite packaging costs. The issue is simply one of production technology for future, survivable SSTO aerospace vehicles that intimately share both laser propulsion engine and satellite functional hardware. A mass production cost goal of 10(exp 3)/kg for the LTD vehicle is probably realizable.

Changes in peripapillary blood vessel density in Graves' orbitopathy after orbital decompression surgery as measured by optical coherence tomography angiography.

PubMed

Lewis, Kyle T; Bullock, John R; Drumright, Ryan T; Olsen, Matthew J; Penman, Alan D

2018-03-08

The purpose is to evaluate the utility of optical coherence tomography (OCT) angiography in the evaluation of Graves' orbitopathy (GO) and response to orbital decompression in patients with and without dysthyroid optic neuropathy (DON). This was a single-center, prospective case series in a cohort of 12 patients (24 orbits) with GO and ±DON, (6 orbits) who underwent bilateral orbital decompression. All patients underwent pre- and postoperative OCT angiography of the peripapillary area. Vessel density indices were calculated in a 4.5 mm × 4.5 mm ellipsoid centered on the optic disk using split-spectrum amplitude decorrelation angiography algorithm, producing the vessel density measurements. Mean change in vessel density indices was compared between pre- and postoperative sessions and between patients with and without DON. Patient 1, a 34-year-old male with GO and unilateral DON OD, showed a significant reduction in blood vessel density indices oculus dexter (OD) (DON eye) after decompression while a more modest reduction was found oculus sinister (OS) with the greatest change noted intrapapillary. Patient 2, a 50-year-old male with DON OU, showed worsening neuropathy following decompression OD that was confirmed by angiographic density indices. Patient 3, a 55-year-female with DON, showed a reduction in blood vessel density OD and increased density OS. Patients without DON showed overall less impressive changes in indices as compared to those with DON. Using OCT angiography, response to surgical treatment in GO orbits, more so in orbits with DON, can be demonstrated and quantified using vessel density indices with reproducibility.

Luxation of eyeball following trauma: novel simple treatment.

PubMed

Osman, Essam A; Al-Akeely, Adel

2014-07-01

Luxation of the eye globe is a rare occasion but it carries a risk of threat to permanent vision loss especially when associated with very high intraocular pressure. Appropriate intervention should be undertaken instantly. Predisposing factors include; eyes as in shallow orbital sockets, floppy eyelid syndrome, and exophthalmos. Prompt reduction results in restoration of full anatomical and visual recovery in otherwise healthy eyes. We report a case of globe luxation following trauma by door handle in a 65-year-old female, who recovered completely after reposition of the globe using Desmarres Lid Retractors.

Orbital Payload Reductions Resulting from Booster and Trajectory Modifications for Recovery of a Large Rocket Booster

NASA Technical Reports Server (NTRS)

Levin, Alan D.; Hopkins, Edward J.

1961-01-01

An analysis was made to determine the reduction in payload for a 300 nautical mile orbit resulting from the addition of inert weight, representing recovery gear, to the first-stage booster of a three-stage rocket vehicle. The values of added inert weight investigated ranged from 0 to 18 percent of gross weight at lift off. The study also included the effects on the payload in orbit and the distance from the launch site at burnout and at impact caused by variation in the vertical rise time before the programmed tilt. The vertical rise times investigated ranged from 16-7 to 100 percent of booster burning time. For a vertical rise of 16.7 percent of booster burning time it was found that a 50-percent increase in the weight of the empty booster resulted in only a 10-percent reduction of the payload in orbit. For no added booster weight, increasing vertical rise time from 16-7 to 100 percent of booster burning time (so that the spent booster would impact in the launch area) reduced the payload by 37 percent. Increasing the vertical rise time from 16-7 to 50 percent of booster burning time resulted in about a 15-percent reduction in the impact distance, and for vertical rise times greater than 50-percent the impact distance decreased rapidly.

Key issues in space nuclear power challenges for the future

NASA Technical Reports Server (NTRS)

Brandhorst, Henry W., Jr.

1991-01-01

The future appears rich in missions that will extend the frontiers of knowledge, human presence in space, and opportunities for profitable commerce. Key to the success of these ventures is the availability of plentiful, cost effective electric power and assured, low cost access to space. While forecasts of space power needs are problematic, an assessment of future needs based on terrestrial experience has been made. These needs fall into three broad categories: survival, self sufficiency, and industrialization. The cost of delivering payloads to orbital locations from LEO to Mars has been determined and future launch cost reductions projected. From these factors, then, projections of the performance necessary for future solar and nuclear space power options has been made. These goals are largely dependent upon orbital location and energy storage needs. Finally the cost of present space power systems has been determined and projections made for future systems.

Key issues in space nuclear power

NASA Technical Reports Server (NTRS)

Brandhorst, Henry W.

1991-01-01

The future appears rich in missions that will extend the frontiers of knowledge, human presence in space, and opportunities for profitable commerce. Key to the success of these ventures is the availability of plentiful, cost effective electric power and assured, low cost access to space. While forecasts of space power needs are problematic, an assessment of future needs based on terrestrial experience has been made. These needs fall into three broad categories: survival, self sufficiency, and industrialization. The cost of delivering payloads to orbital locations from LEO to Mars has been determined and future launch cost reductions projected. From these factors, then, projections of the performance necessary for future solar and nuclear space power options has been made. These goals are largely dependent upon orbital location and energy storage needs. Finally the cost of present space power systems has been determined and projections made for future systems.

Structures and materials technology issues for reusable launch vehicles

NASA Technical Reports Server (NTRS)

Dixon, S. C.; Tenney, D. R.; Rummler, D. R.; Wieting, A. R.; Bader, R. M.

1985-01-01

Projected space missions for both civil and defense needs require significant improvements in structures and materials technology for reusable launch vehicles: reductions in structural weight compared to the Space Shuttle Orbiter of up to 25% or more, a possible factor of 5 or more increase in mission life, increases in maximum use temperature of the external surface, reusable containment of cryogenic hydrogen and oxygen, significant reductions in operational costs, and possibly less lead time between technology readiness and initial operational capability. In addition, there is increasing interest in hypersonic airbreathing propulsion for launch and transmospheric vehicles, and such systems require regeneratively cooled structure. The technology issues are addressed, giving brief assessments of the state-of-the-art and proposed activities to meet the technology requirements in a timely manner.

Modified lateral orbital wall decompression in Graves' orbitopathy using computer-assisted planning.

PubMed

Spalthoff, S; Jehn, P; Zimmerer, R; Rana, M; Gellrich, N-C; Dittmann, J

2018-02-01

Graves' orbitopathy, a condition seen in the autoimmune syndrome Graves' disease, affects the fatty tissue and muscles inside the orbit. Graves' orbitopathy is associated with increasing exophthalmos and sometimes leads to compressive dysthyroid optic neuropathy, resulting in progressive vision loss. Dysthyroid compressive optic neuropathy, functional problems, and cosmetic problems are the main indications for surgical decompression of the orbit, especially if conservative treatment has not led to a reduction in symptoms. Many surgical techniques are described in the literature. This article presents a modification of the lateral orbital wall osteotomy, involving the rotation and reduction of the osteotomized bone segment using preoperative planning, intraoperative computed navigation, and piezoelectric surgery. This new method combines the advantages of different techniques and appears to be a valid approach to the treatment of severe cases of Graves' orbitopathy. Copyright © 2017 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Europa Planetary Protection for Juno Jupiter Orbiter

NASA Technical Reports Server (NTRS)

Bernard, Douglas E.; Abelson, Robert D.; Johannesen, Jennie R.; Lam, Try; McAlpine, William J.; Newlin, Laura E.

2010-01-01

NASA's Juno mission launched in 2011 and will explore the Jupiter system starting in 2016. Juno's suite of instruments is designed to investigate the atmosphere, gravitational fields, magnetic fields, and auroral regions. Its low perijove polar orbit will allow it to explore portions of the Jovian environment never before visited. While the Juno mission is not orbiting or flying close to Europa or the other Galilean satellites, planetary protection requirements for avoiding the contamination of Europa have been taken into account in the Juno mission design.The science mission is designed to conclude with a deorbit burn that disposes of the spacecraft in Jupiter's atmosphere. Compliance with planetary protection requirements is verified through a set of analyses including analysis of initial bioburden, analysis of the effect of bioburden reduction due to the space and Jovian radiation environments, probabilistic risk assessment of successful deorbit, Monte-Carlo orbit propagation, and bioburden reduction in the event of impact with an icy body.

Performance trade studies of a solar electric orbit transfer mission

NASA Astrophysics Data System (ADS)

Sutton, D. M.; McLain, M. G.; Kechichian, J. A.

An analysis of several electric orbit transfer trade studies investigating the performance of a solar-powered electric orbit transfer vehicle (EOTV) is presented. One trade illustrates how the greatest payload capability for time-of-flight constrained transfers can be obtained by optimizing specific impulse. Various methods of reducing the accumulated fluence of charged particles during transit are evaluated in a second trade study. The reduction in fluence obtained by shaping the trajectory to avoid high radiation flux density regions is compared with reductions obtained by using a hybrid chemical/electric vehicle, by additional radiation-protective coverslide material added to the solar array, and by increasing the power of the vehicle. It is shown that a trajectory shaped to minimize fluence may be an advantage to the complete EOTV design. A final trade study shows how park orbit altitude influences the initial thrust-to-drag ratio of an EOTV.

Analyses of solar viewing time, beta angle, and doppler shift for solar observations from the space shuttle

NASA Technical Reports Server (NTRS)

Brandon, J. P.

1972-01-01

Studies of solar physics phenomena are aided by the ability to observe the sun from earth orbit without periodic occultation. Charts are presented for the selection of suitable orbits about the earth at which a spacecraft is continuously illuminated through a period of a few days. Selection of the orbits considers the reduction of Doppler shift and wavefront attenuation due to relative orbital velocity and residual earth atmosphere.

GEODYN operations description, volume 3. [computer program for estimation of orbit and geodetic parameters

NASA Technical Reports Server (NTRS)

Martin, T. V.; Mullins, N. E.

1972-01-01

The operating and set-up procedures for the multi-satellite, multi-arc GEODYN- Orbit Determination program are described. All system output is analyzed. The GEODYN Program is the nucleus of the entire GEODYN system. It is a definitive orbit and geodetic parameter estimation program capable of simultaneously processing observations from multiple arcs of multiple satellites. GEODYN has two modes of operation: (1) the data reduction mode and (2) the orbit generation mode.

Giant onsite electronic entropy enhances the performance of ceria for water splitting.

PubMed

Naghavi, S Shahab; Emery, Antoine A; Hansen, Heine A; Zhou, Fei; Ozolins, Vidvuds; Wolverton, Chris

2017-08-18

Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has been the focus of most previous work. Here we report a different source of entropy, the onsite electronic configurational entropy, arising from coupling between orbital and spin angular momenta in lanthanide f orbitals. We find that onsite electronic configurational entropy is sizable in all lanthanides, and reaches a maximum value of ≈4.7 k B per oxygen vacancy for Ce 4+ /Ce 3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions.Solid-state entropy of reduction increases the thermodynamic efficiency of ceria for two-step thermochemical water splitting. Here, the authors report a large and different source of entropy, the onsite electronic configurational entropy arising from coupling between orbital and spin angular momenta in f orbitals.

Space Shuttle Solid Rocket Booster Lightweight Recovery System

NASA Technical Reports Server (NTRS)

Wolf, Dean; Runkle, Roy E.

1995-01-01

The cancellation of the Advanced Solid Rocket Booster Project and the earth-to-orbit payload requirements for the Space Station dictated that the National Aeronautics and Space Administration (NASA) look at performance enhancements from all Space Transportation System (STS) elements (Orbiter Project, Space Shuttle Main Engine Project, External Tank Project, Solid Rocket Motor Project, & Solid Rocket Booster Project). The manifest for launching of Space Station components indicated that an additional 12-13000 pound lift capability was required on 10 missions and 15-20,000 pound additional lift capability is required on two missions. Trade studies conducted by all STS elements indicate that by deleting the parachute Recovery System (and associated hardware) from the Solid Rocket Boosters (SRBS) and going to a lightweight External Tank (ET) the 20,000 pound additional lift capability can be realized for the two missions. The deletion of the parachute Recovery System means the loss of four SRBs and this option is two expensive (loss of reusable hardware) to be used on the other 10 Space Station missions. Accordingly, each STS element looked at potential methods of weight savings, increased performance, etc. As the SRB and ET projects are non-propulsive (i.e. does not have launch thrust elements) their only contribution to overall payload enhancement can be achieved by the saving of weight while maintaining adequate safety factors and margins. The enhancement factor for the SRB project is 1:10. That is for each 10 pounds saved on the two SRBS; approximately 1 additional pound of payload in the orbiter bay can be placed into orbit. The SRB project decided early that the SRB recovery system was a prime candidate for weight reduction as it was designed in the early 1970s and weight optimization had never been a primary criteria.

Noise and Dissipation on Coadjoint Orbits

NASA Astrophysics Data System (ADS)

Arnaudon, Alexis; De Castro, Alex L.; Holm, Darryl D.

2018-02-01

We derive and study stochastic dissipative dynamics on coadjoint orbits by incorporating noise and dissipation into mechanical systems arising from the theory of reduction by symmetry, including a semidirect product extension. Random attractors are found for this general class of systems when the Lie algebra is semi-simple, provided the top Lyapunov exponent is positive. We study in details two canonical examples, the free rigid body and the heavy top, whose stochastic integrable reductions are found and numerical simulations of their random attractors are shown.

User's guide to the UTIL-ODRC tape processing program. [for the Orbital Data Reduction Center

NASA Technical Reports Server (NTRS)

Juba, S. M. (Principal Investigator)

1981-01-01

The UTIL-ODRC computer compatible tape processing program, its input/output requirements, and its interface with the EXEC 8 operating system are described. It is a multipurpose orbital data reduction center (ODRC) tape processing program enabling the user to create either exact duplicate tapes and/or tapes in SINDA/HISTRY format. Input data elements for PRAMPT/FLOPLT and/or BATCH PLOT programs, a temperature summary, and a printed summary can also be produced.

Evaluation of minimum coverage size and orbital accuracy at different orbital regimes for one order of magnitude reduction of the catastrophic collision risk

NASA Astrophysics Data System (ADS)

Sánchez-Ortiz, Noelia; Domínguez-González, Raúl; Krag, Holger

2015-03-01

One of the main objectives of Space Surveillance and Tracking (SST) systems is to support space collision avoidance activities. This collision avoidance capability aims to significantly reduce the catastrophic collision risk of space objects. In particular, for the case of the future European SST, the objective is translated into a risk reduction of one order of magnitude whilst keeping a low number of false alarm events. In order to translate this aim into system requirements, an evaluation of the current catastrophic collision risk for different orbital regimes is addressed. The reduction of such risk depends on the amount of catalogued objects (coverage) and the knowledge of the associated orbits in the catalogue (accuracy). This paper presents an analysis of the impact of those two aspects in the capability to reduce the catastrophic collision risk at some orbital regimes. A reliable collision avoidance support depends on the accuracy of the predicted miss-events. The assessment of possible conjunctions is normally done by computing the estimated miss-distances between objects (which is compared with a defined distance threshold) or by computing the associated collision risk (which is compared with the corresponding accepted collision probability level). This second method is normally recommended because it takes into account the reliability of the orbits and allows reducing false alarm events. The collision risk depends on the estimated miss-distance, the object sizes and the accuracy of the two orbits at the time of event. This accuracy depends on the error of the orbits at the orbit determination epoch and the error derived from the propagation from that epoch up to the time of event. The modified DRAMA ARES (Domínguez-González et al., 2012, 2013a,b; Gelhaus et al., 2014) provides information on the expected number of encounters for a given mission and year. It also provides information on the capacity to reduce the risk of collision by means of avoidance manoeuvres as a function of the accepted collision probability level and the cataloguing performance of the surveillance system (determined by the limiting coverage size-altitude function and the orbital data accuracy). The assessment of avoidance strategies takes into account statistical models of the space object environment, as provided by ESA's MASTER-2009 model, and a mathematical framework for the collision risk estimation as used in satellite operations. In this papers, results are provided for some orbit types, covering different orbital regimes. The analysis is done for different cataloguing capacity levels (accuracy and coverage), concluding that 5 cm are to be covered at LEO for diminishing the catastrophic collision risk by one order of magnitude. For MEO and GEO regime, coverage down to 40 and 100 cm respectively allow similar reduction of risk.

Singular reduction of resonant Hamiltonians

NASA Astrophysics Data System (ADS)

Meyer, Kenneth R.; Palacián, Jesús F.; Yanguas, Patricia

2018-06-01

We investigate the dynamics of resonant Hamiltonians with n degrees of freedom to which we attach a small perturbation. Our study is based on the geometric interpretation of singular reduction theory. The flow of the Hamiltonian vector field is reconstructed from the cross sections corresponding to an approximation of this vector field in an energy surface. This approximate system is also built using normal forms and applying reduction theory obtaining the reduced Hamiltonian that is defined on the orbit space. Generically, the reduction is of singular character and we classify the singularities in the orbit space, getting three different types of singular points. A critical point of the reduced Hamiltonian corresponds to a family of periodic solutions in the full system whose characteristic multipliers are approximated accordingly to the nature of the critical point.

Local distortion and EPR parameters of copper(II) in borate glasses

NASA Astrophysics Data System (ADS)

Kuang, Min-Quan; Wang, Li-Dan; Duan, Shu-Kai

2017-12-01

The EPR parameters (g and A tensors) of the paramagnetic Cu2+ sites in CaB4O7, LiCaBO3, Li2B4O7, KLiB4O7 glasses are well explained by utilizing the fourth-order perturbation formulas for 3 d9 ions in the tetragonally elongated octahedral [CuO6]10- clusters. The magnitude of the local distortion for the [CuO6]10- clusters suffering the Jahn-Teller effect is denoted by the relative elongation ratio ρ which is proportional to the ratio Δg///Δg⊥ (Δg//= g//-gs and Δg⊥ = g⊥-gs). The g isotropies giso (=(g//+2g⊥)/3) undergo an linear increase with the decline of the covalecny of the glass systems (i.e., the augment of the orbital reduction factor k). The signs of the hyperfine structure constants are determined by computing the quantitative contributions arising from the isotropic and anisotropic copper 3d-3s (4s) orbital admixtures indicated by the core polarization constant κ and the reduction factor H, respectively. The above correlations are proved to be available for analogous borate glasses doping with copper ions, e.g., MRbB4O7 (M = Li, Na and K), 90M2B4O7·9PbO·CuO (M = Li, Na and K), 10MO·30ZnO·60B2O3 (M = Mg, Ca and Sr) and xLi2O·(30-x)Na2O·69.5B2O3 (5 ≤ x ≤ 25 mol%), and all the results are discussed.

GEODYN system description, volume 1. [computer program for estimation of orbit and geodetic parameters

NASA Technical Reports Server (NTRS)

Chin, M. M.; Goad, C. C.; Martin, T. V.

1972-01-01

A computer program for the estimation of orbit and geodetic parameters is presented. The areas in which the program is operational are defined. The specific uses of the program are given as: (1) determination of definitive orbits, (2) tracking instrument calibration, (3) satellite operational predictions, and (4) geodetic parameter estimation. The relationship between the various elements in the solution of the orbit and geodetic parameter estimation problem is analyzed. The solution of the problems corresponds to the orbit generation mode in the first case and to the data reduction mode in the second case.

Reduction of Sodium in the NASA Space Food System

NASA Technical Reports Server (NTRS)

Kloeris, Vickie L.

2010-01-01

Excessive sodium content of the average American diet is an issue that is gaining more and more attention due to the implications for chronic disease and thus health care costs. The typical astronaut or cosmonaut dining on the International Space Station (ISS) is consuming even more sodium per day than the average American due to the lack of refrigeration for food and the limited amount of fresh food in the diet. NASA has known for many years that the high sodium in the on orbit diet is an exacerbating factor for the bone loss that occurs in all crew members in microgravity. However, bone loss is reversed upon return to earth normal gravity. After ten years of having US crewmembers on ISS, additional medical issues have emerged in some long duration ISS crewmembers that are not necessarily being reversed upon return to earth. While it is not necessarily thought that the high sodium content of the diet is the cause of these issues, it is thought that reducing sodium intake could potentially help alleviate some of the on orbit symptoms. Thus, there is an urgent focus on sodium reduction in space food. This paper will discuss the strategies and progress of an on-going project at NASA to reformulate the US space food system to reduce the sodium content.

Research on the impact factors of GRACE precise orbit determination by dynamic method

NASA Astrophysics Data System (ADS)

Guo, Nan-nan; Zhou, Xu-hua; Li, Kai; Wu, Bin

2018-07-01

With the successful use of GPS-only-based POD (precise orbit determination), more and more satellites carry onboard GPS receivers to support their orbit accuracy requirements. It provides continuous GPS observations in high precision, and becomes an indispensable way to obtain the orbit of LEO satellites. Precise orbit determination of LEO satellites plays an important role for the application of LEO satellites. Numerous factors should be considered in the POD processing. In this paper, several factors that impact precise orbit determination are analyzed, namely the satellite altitude, the time-variable earth's gravity field, the GPS satellite clock error and accelerometer observation. The GRACE satellites provide ideal platform to study the performance of factors for precise orbit determination using zero-difference GPS data. These factors are quantitatively analyzed on affecting the accuracy of dynamic orbit using GRACE observations from 2005 to 2011 by SHORDE software. The study indicates that: (1) with the altitude of the GRACE satellite is lowered from 480 km to 460 km in seven years, the 3D (three-dimension) position accuracy of GRACE satellite orbit is about 3˜4 cm based on long spans data; (2) the accelerometer data improves the 3D position accuracy of GRACE in about 1 cm; (3) the accuracy of zero-difference dynamic orbit is about 6 cm with the GPS satellite clock error products in 5 min sampling interval and can be raised to 4 cm, if the GPS satellite clock error products with 30 s sampling interval can be adopted. (4) the time-variable part of earth gravity field model improves the 3D position accuracy of GRACE in about 0.5˜1.5 cm. Based on this study, we quantitatively analyze the factors that affect precise orbit determination of LEO satellites. This study plays an important role to improve the accuracy of LEO satellites orbit determination.

Results after En Bloc Lateral Wall Decompression Surgery with Orbital Fat Resection in 111 Patients with Graves' Orbitopathy

PubMed Central

Fichter, Nicole; Guthoff, Rudolf F.

2015-01-01

Purpose. To evaluate the effect of en bloc lateral wall decompression with additional orbital fat resection in terms of exophthalmos reduction and complications. Methods. A retrospective, noncomparative case series study from 1999 to 2011 (chart review) in Graves' orbitopathy (GO) patients. The standardized surgical technique involved removal of the lateral orbital wall including the orbital rim via a lid crease approach combined with additional orbital fat resection. Exophthalmos, diplopia, retrobulbar pressure sensation, and complications were analyzed pre- and postoperatively. Results. A total of 111 patients (164 orbits) with follow-up >3 months were analysed. Mean exophthalmos reduction was 3.05mm and preoperative orbital pressure sensation resolved or improved in all patients. Visual acuity improved significantly in patients undergoing surgery for rehabilitative or vision threatening purposes. Preoperative diplopia improved in 10 patients (9.0%) but worsened in 5 patients (4.5%), necessitating surgical correction in 3 patients. There were no significant complications; however, one patient had slight hollowing of the temporalis muscle around the scar that did not necessitate revision, and another patient with a circumscribed retraction of the scar itself underwent surgical correction. Conclusions. The study confirms the efficiency of en bloc lateral wall decompression in GO in a large series of patients, highlighting the low risk of disturbance of binocular functions and of cosmetic blemish in the temporal midface region. PMID:26221142

First-order analytic propagation of satellites in the exponential atmosphere of an oblate planet

NASA Astrophysics Data System (ADS)

Martinusi, Vladimir; Dell'Elce, Lamberto; Kerschen, Gaëtan

2017-04-01

The paper offers the fully analytic solution to the motion of a satellite orbiting under the influence of the two major perturbations, due to the oblateness and the atmospheric drag. The solution is presented in a time-explicit form, and takes into account an exponential distribution of the atmospheric density, an assumption that is reasonably close to reality. The approach involves two essential steps. The first one concerns a new approximate mathematical model that admits a closed-form solution with respect to a set of new variables. The second step is the determination of an infinitesimal contact transformation that allows to navigate between the new and the original variables. This contact transformation is obtained in exact form, and afterwards a Taylor series approximation is proposed in order to make all the computations explicit. The aforementioned transformation accommodates both perturbations, improving the accuracy of the orbit predictions by one order of magnitude with respect to the case when the atmospheric drag is absent from the transformation. Numerical simulations are performed for a low Earth orbit starting at an altitude of 350 km, and they show that the incorporation of drag terms into the contact transformation generates an error reduction by a factor of 7 in the position vector. The proposed method aims at improving the accuracy of analytic orbit propagation and transforming it into a viable alternative to the computationally intensive numerical methods.

Orbital trim by velocity factoring with applications to the Viking mission.

NASA Technical Reports Server (NTRS)

Kibler, J. F.; Green, R. N.; Young, G. R.

1972-01-01

An orbital trim technique has been developed to satisfy terminal rendezvous and intermediate timing constraints for planetary missions involving orbital operations. The technique utilizes a time-open two-impulse transfer from a specified initial orbit to a final orbit which satisfies all geometrical constraints. Each of the two impulses may then be factored, or split, into two or more vectorially equivalent impulses. The periods of the resulting intermediate orbits may be varied along with the number of revolutions in each orbit to satisfy the intermediate and final timing constraints. Factors in the range 0 to 1 result in rendezvous at the same cost as that of the two-impulse transfer. The technique is applied to the Viking mission to Mars although a similar procedure could be utilized for rendezvous operations about any planet.

CORRIGENDUM: Supersymmetric Kaluza-Klein reductions of M-waves and MKK-monopoles

NASA Astrophysics Data System (ADS)

Figueroa-O'Farrill, J.; Simón, J.

2004-01-01

In this paper we classified the smooth supersymmetric Kaluza-Klein reductions of the purely gravitational half-BPS backgrounds of M-theory: the purely gravitational plane wave and the Kaluza-Klein monopole. The analysis of the Kaluza-Klein monopole yielded seven possible Kaluza-Klein reductions labelled (A)-(G). In truth, we failed to discard two of the reductions: those labelled (F) and (G). These reductions fail to be smooth due to the fact that the orbits of the Killing vector effecting the reduction have different topological type: at those points where the null rotation component vanishes, the orbits are circles, whereas at the other points they are diffeomorphic to the real line. In other words, although the action is free, some points (corresponding to the circular orbits) possess nontrivial stabilizers: namely the infinite cyclic subgroup generated by the period. A similar argument has already been used in [1] to discard one of the possible reductions of the M2 brane. Even though the discarded reductions exist, and some of them can even be supersymmetric, one of the purposes of the paper was to present a full classification of smooth reductions of the purely gravitational half-BPS backgrounds of M-theory. As a result the following changes must be made. At the very end of section 3.2, the two cases (F) and (G) must be deleted. In section 3.3, the paragraphs discussing the supersymmetry of these reductions should be omitted. Similarly the entries in table 7 which are in parentheses should also be omitted. In section 3.4, the parameter β in the expression for λ in the unnumbered equation preceding (3.14) should be put to zero, with the corresponding change in equation (3.14). Finally the entry in table10 containing the nullbrane (N) disappears. References [1] Figueroa-O'Farrill J and SimA~3n J 2002 Supersymmetric Kaluza-Klein reductions of M2 and M5-branes Adv. Theor. Math. Phys. 6 703-93 (Preprint hep-th/0208107)

Factors affecting frequency and orbit utilization by high power transmission satellite systems.

NASA Technical Reports Server (NTRS)

Kuhns, P. W.; Miller, E. F.; O'Malley, T. A.

1972-01-01

The factors affecting the sharing of the geostationary orbit by high power (primarily television) satellite systems having the same or adjacent coverage areas and by satellites occupying the same orbit segment are examined and examples using the results of computer computations are given. The factors considered include: required protection ratio, receiver antenna patterns, relative transmitter power, transmitter antenna patterns, satellite grouping, and coverage pattern overlap. The results presented indicate the limits of system characteristics and orbit deployment which can result from mixing systems.

Factors affecting frequency and orbit utilization by high power transmission satellite systems

NASA Technical Reports Server (NTRS)

Kuhns, P. W.; Miller, E. F.; Malley, T. A.

1972-01-01

The factors affecting the sharing of the geostationary orbit by high power (primarily television) satellite systems having the same or adjacent coverage areas and by satellites occupying the same orbit segment are examined and examples using the results of computer computations are given. The factors considered include: required protection ratio, receiver antenna patterns, relative transmitter power, transmitter antenna patterns, satellite grouping, and coverage pattern overlap. The results presented indicated the limits of system characteristics and orbit deployment which can result from mixing systems.

Stability and control flight test results of the space transportation system's orbiter

NASA Technical Reports Server (NTRS)

Culp, M. A.; Cooke, D. R.

1982-01-01

Flight testing of the Space Shuttle Orbiter is in progress and current results of the post-flight aerodynamic analyses are discussed. The purpose of these analyses is to reduce the pre-flight aerodynamic uncertainties, thereby leading to operational certification of the Orbiter flight envelope relative to the integrated airframe and flight control system. Primary data reduction is accomplished with a well documented maximum likelihood system identification techniques.

Luxation of Eye ball following trauma: Novel simple treatment

PubMed Central

Osman, Essam A.; Al-Akeely, Adel

2014-01-01

Luxation of the eye globe is a rare occasion but it carries a risk of threat to permanent vision loss especially when associated with very high intraocular pressure. Appropriate intervention should be undertaken instantly. Predisposing factors include; eyes as in shallow orbital sockets, floppy eyelid syndrome, and exophthalmos. Prompt reduction results in restoration of full anatomical and visual recovery in otherwise healthy eyes. We report a case of globe luxation following trauma by door handle in a 65-year-old female, who recovered completely after reposition of the globe using Desmarres Lid Retractors. PMID:25116777

[Development of ocular motility following modified 3-wall decompression of the orbita in endocrine orbitopathy for functional and rehabilitative indication].

PubMed

Grenzebach, Ulrike H; Schnorbus, Ulrike; Büchner, Thomas; Busse, Holger; Stoll, Wolfgang

2003-05-01

Permanent visual damage due to an increase in volume of the orbital contents may be the result of the failure of conservative therapeutic concepts in the treatment of endocrine orbitopathy. Considerable progress has been achieved in developing successful orbital decompression techniques with regard to functional and cosmetic outcome. Decompression techniques with resection of the bony orbital walls are adequate tools in restoring visual acuity and reducing exophthalmus. A considerable degree of deterioration of motility disorders has been described in the literature depending on the techniques being used. The purpose of this study was to investigate whether a modified technique of 3-wall orbital decompression with preservation of a medial part of the periorbital tissue to support the medial rectus muscle, is able to reduce the postoperative risk of diplopia. A modified technique of orbital 3-wall decompression with resection of the medial orbital wall, the medial orbital floor and the floor of the frontal sinus has been used in patients with compressive optic neuropathy (n = 20) and for cosmetic reasons (n = 7) in cases of uni- or bilateral proptosis. Analysis of the results was performed concerning visual outcome, exophthalmus reduction and development of horizontal and vertical motility changes. In all cases of optic neuropathy improvement of visual function at an average of 4.63 +/- 4.5 lines could be achieved. Exophthalmus reduction was 3.2 +/- 2.4 mm in the functional group and 3.9 +/- 1.7 mm in the rehabilitative group. In this group motility of the medial rectus muscle remained unaffected except in one eye. In the functional group motility deterioration was observed in 62 %. The modified 3-wall decompression technique with preservation of a medial periorbital tissue strip is an adequate alternative technique in the therapy of optic neuropathy and exophthalmus reduction in endocrine orbitopathy with a low risk of postoperative motility disorders.

KSC-98pc1164

NASA Image and Video Library

1998-09-28

The orbiter Atlantis is towed away from the Shuttle Landing Facility after returning home from California atop its Shuttle Carrier Aircraft. The orbiter spent 10 months in Palmdale undergoing extensive inspections and modifications in the orbiter processing facility there. The modifications included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

On Adopting a Proactive Approach to the Disposition of Mars Orbiters

NASA Astrophysics Data System (ADS)

Rummel, John; Shotwell, Robert; Price, Hoppy

2016-07-01

There are currently three U.S. orbiters at Mars plus two orbiters from other nations. At the end of each mission, it is desirable to dispose of the vehicle in a condition where it would present no hazard to other orbiters and to potential future crewed vehicles, while meeting planetary protection constraints. There is currently no way to accurately track and confirm positions of these orbiters after they are no longer being actively tracked from Earth, and due to the extremely "bumpy" nature of the Martian gravity field the position of these vehicles rapidly becomes unknowable . The current COSPAR Planetary Protection Policy for Mars includes a throwback to an earlier era of planetary exploration. The Policy's provisions for the disposition of Mars orbiters includes an option "to meet orbital lifetime requirements" of 20 years (at 99% probability) and 50 years (at 95% probability) after launch (which we will call option 1), or option 2, requiring total (surface, mated, and encapsulated) bioburden levels of ≤ 5 x 10 ^{5} spores - which may be discounted by the number of spores thought to be destroyed during the eventual deorbit of the spacecraft. Reference to DeVincenzi et al (1996) illustrates that the current orbital lifetime requirements in option 1 are directly tied to the notion of a "period of exploration," rather than to any explicit expectation of bioload reduction. Under the current regime, all orbiters comply with option 1, orbital lifetime, or option 2, prior to launch, which generally includes an approved bioburden reduction program prior to launch. As part of option 2, a break up/burn up analysis is also performed, covering the event of an uncontrolled re-entry at arrival or during the orbital mission itself. It has been suggested that we should be seeing an increasing tempo of Mars operations, with an emphasis on making maximum use of communications orbiters in particular. It can be shown that for many orbiters, deorbiting can take quite a bit less delta-V than orbit raising (e.g., to >500 km) to extend their lifetime, so deorbiting (with an attendant focus on increasing burnup and breakup to limit microbial contamination) could provide for possibly years more relay support, as well as a more explicit step for bioburden reduction. Deorbiting can also provide for a more positive termination, eliminates future risk of orbital debris generation around Mars, and ends the possibility of re-entering in an uncontrolled fashion and uncontrolled location later. This paper lays out the issues and options associated with an emphasis on option 2 as the preferred orbiter disposal strategy for Category III missions to Mars. The expectation is that valuable orbits can be better protected for future explorers, and that controls over the contamination of Mars by orbiters can be improved if COSPAR adopts this re-emphasis on behalf of the agencies which are now planning future missions to Mar. Ref. DeVincenzi, D. L., P. D. Stabekis, and J. Barengoltz, Refinement of planetary protection policy for Mars missions, Adv. Space Res. 18: 311-316, 1996.

Orbit orientation in didelphid marsupials (Didelphimorphia: Didelphidae)

PubMed Central

Pilatti, Patricia

2017-01-01

Abstract Usually considered a morphologically conservative group, didelphid marsupials present considerable variation in ecology and body size, some of which were shown to relate to morphological structures. Thus, changes on orbit morphology are likely and could be related to that variation. We calculated orbit orientation in 873 specimens of 16 Didelphidae genera yielding estimates of orbits convergence (their position relative to midsagittal line) and verticality (their position relative to frontal plane). We then compared similarities in these variables across taxa to ecological, morphological and phylogenetic data to evaluate the influencing factors on orbit orientation in didelphids. We found an inverse relation between convergence and verticality. Didelphids orbits have low verticality but are highly convergent, yet orbit orientation differs significantly between taxa, and that variation is related to morphological aspects of the cranium. Rostral variables are the only morphological features correlated with orbit orientation: increasing snout length yields more convergent orbits, whereas increase on snout breadth imply in more vertical orbits. Size and encephalization quotients are uncorrelated with orbit orientation. Among ecological data, diet showed significant correlation whereas locomotion is the factor that less affects the position of orbits. Phylogeny is uncorrelated to any orbital parameters measured. Ecological factors seemingly play a more important role on orbit orientation than previously expected, and differentiation on orbit orientation seems to be more functional than inherited. Thus, despite the apparent homogeneity on didelphid morphology, there is subtle morphological variability that may be directly related to feeding behavior. PMID:29492000

Reduction of the virtual space for coupled-cluster excitation energies of large molecules and embedded systems

PubMed Central

Send, Robert; Kaila, Ville R. I.; Sundholm, Dage

2011-01-01

We investigate how the reduction of the virtual space affects coupled-cluster excitation energies at the approximate singles and doubles coupled-cluster level (CC2). In this reduced-virtual-space (RVS) approach, all virtual orbitals above a certain energy threshold are omitted in the correlation calculation. The effects of the RVS approach are assessed by calculations on the two lowest excitation energies of 11 biochromophores using different sizes of the virtual space. Our set of biochromophores consists of common model systems for the chromophores of the photoactive yellow protein, the green fluorescent protein, and rhodopsin. The RVS calculations show that most of the high-lying virtual orbitals can be neglected without significantly affecting the accuracy of the obtained excitation energies. Omitting all virtual orbitals above 50 eV in the correlation calculation introduces errors in the excitation energies that are smaller than 0.1 eV . By using a RVS energy threshold of 50 eV , the CC2 calculations using triple-ζ basis sets (TZVP) on protonated Schiff base retinal are accelerated by a factor of 6. We demonstrate the applicability of the RVS approach by performing CC2∕TZVP calculations on the lowest singlet excitation energy of a rhodopsin model consisting of 165 atoms using RVS thresholds between 20 eV and 120 eV. The calculations on the rhodopsin model show that the RVS errors determined in the gas-phase are a very good approximation to the RVS errors in the protein environment. The RVS approach thus renders purely quantum mechanical treatments of chromophores in protein environments feasible and offers an ab initio alternative to quantum mechanics∕molecular mechanics separation schemes. PMID:21663351

Reduced-cost linear-response CC2 method based on natural orbitals and natural auxiliary functions

PubMed Central

Mester, Dávid

2017-01-01

A reduced-cost density fitting (DF) linear-response second-order coupled-cluster (CC2) method has been developed for the evaluation of excitation energies. The method is based on the simultaneous truncation of the molecular orbital (MO) basis and the auxiliary basis set used for the DF approximation. For the reduction of the size of the MO basis, state-specific natural orbitals (NOs) are constructed for each excited state using the average of the second-order Møller–Plesset (MP2) and the corresponding configuration interaction singles with perturbative doubles [CIS(D)] density matrices. After removing the NOs of low occupation number, natural auxiliary functions (NAFs) are constructed [M. Kállay, J. Chem. Phys. 141, 244113 (2014)], and the NAF basis is also truncated. Our results show that, for a triple-zeta basis set, about 60% of the virtual MOs can be dropped, while the size of the fitting basis can be reduced by a factor of five. This results in a dramatic reduction of the computational costs of the solution of the CC2 equations, which are in our approach about as expensive as the evaluation of the MP2 and CIS(D) density matrices. All in all, an average speedup of more than an order of magnitude can be achieved at the expense of a mean absolute error of 0.02 eV in the calculated excitation energies compared to the canonical CC2 results. Our benchmark calculations demonstrate that the new approach enables the efficient computation of CC2 excitation energies for excited states of all types of medium-sized molecules composed of up to 100 atoms with triple-zeta quality basis sets. PMID:28527453

Reduction of the virtual space for coupled-cluster excitation energies of large molecules and embedded systems.

PubMed

Send, Robert; Kaila, Ville R I; Sundholm, Dage

2011-06-07

We investigate how the reduction of the virtual space affects coupled-cluster excitation energies at the approximate singles and doubles coupled-cluster level (CC2). In this reduced-virtual-space (RVS) approach, all virtual orbitals above a certain energy threshold are omitted in the correlation calculation. The effects of the RVS approach are assessed by calculations on the two lowest excitation energies of 11 biochromophores using different sizes of the virtual space. Our set of biochromophores consists of common model systems for the chromophores of the photoactive yellow protein, the green fluorescent protein, and rhodopsin. The RVS calculations show that most of the high-lying virtual orbitals can be neglected without significantly affecting the accuracy of the obtained excitation energies. Omitting all virtual orbitals above 50 eV in the correlation calculation introduces errors in the excitation energies that are smaller than 0.1 eV. By using a RVS energy threshold of 50 eV, the CC2 calculations using triple-ζ basis sets (TZVP) on protonated Schiff base retinal are accelerated by a factor of 6. We demonstrate the applicability of the RVS approach by performing CC2/TZVP calculations on the lowest singlet excitation energy of a rhodopsin model consisting of 165 atoms using RVS thresholds between 20 eV and 120 eV. The calculations on the rhodopsin model show that the RVS errors determined in the gas-phase are a very good approximation to the RVS errors in the protein environment. The RVS approach thus renders purely quantum mechanical treatments of chromophores in protein environments feasible and offers an ab initio alternative to quantum mechanics/molecular mechanics separation schemes. © 2011 American Institute of Physics

A white paper: Operational efficiency. New approaches to future propulsion systems

NASA Technical Reports Server (NTRS)

Rhodes, Russel; Wong, George

1991-01-01

Advanced launch systems for the next generation of space transportation systems (1995 to 2010) must deliver large payloads (125,000 to 500,000 lbs) to low earth orbit (LEO) at one tenth of today's cost, or 300 to 400 $/lb of payload. This cost represents an order of magnitude reduction from the Titan unmanned vehicle cost of delivering payload to orbit. To achieve this sizable reduction, the operations cost as well as the engine cost must both be lower than current engine system. The Advanced Launch System (ALS) is studying advanced engine designs, such as the Space Transportation Main Engine (STME), which has achieved notable reduction in cost. The results are presented of a current study wherein another level of cost reduction can be achieved by designing the propulsion module utilizing these advanced engines for enhanced operations efficiency and reduced operations cost.

The Gravity Probe B `Niobium bird' experiment: Verifying the data reduction scheme for estimating the relativistic precession of Earth-orbiting gyroscopes

NASA Technical Reports Server (NTRS)

Uemaatsu, Hirohiko; Parkinson, Bradford W.; Lockhart, James M.; Muhlfelder, Barry

1993-01-01

Gravity Probe B (GP-B) is a relatively gyroscope experiment begun at Stanford University in 1960 and supported by NASA since 1963. This experiment will check, for the first time, the relativistic precession of an Earth-orbiting gyroscope that was predicted by Einstein's General Theory of Relativity, to an accuracy of 1 milliarcsecond per year or better. A drag-free satellite will carry four gyroscopes in a polar orbit to observe their relativistic precession. The primary sensor for measuring the direction of gyroscope spin axis is the SQUID (superconducting quantum interference device) magnetometer. The data reduction scheme designed for the GP-B program processes the signal from the SQUID magnetometer and estimates the relativistic precession rates. We formulated the data reduction scheme and designed the Niobium bird experiment to verify the performance of the data reduction scheme experimentally with an actual SQUID magnetometer within the test loop. This paper reports the results from the first phase of the Niobium bird experiment, which used a commercially available SQUID magnetometer as its primary sensor, and adresses the issues they raised. The first phase resulted in a large, temperature-dependent bias drift in the insensitive design and a temperature regulation scheme.

Predicting Major Bleeding in Ischemic Stroke Patients With Atrial Fibrillation.

PubMed

Hilkens, Nina A; Algra, Ale; Greving, Jacoba P

2017-11-01

Performance of risk scores for major bleeding in patients with atrial fibrillation and a previous transient ischemic attack or ischemic stroke is not well established. We aimed to validate risk scores for major bleeding in patients with atrial fibrillation treated with oral anticoagulants after cerebral ischemia and explore the net benefit of oral anticoagulants among bleeding risk categories. We analyzed 3623 patients with a history of transient ischemic attack or stroke included in the RE-LY trial (Randomized Evaluation of Long-Term Anticoagulation Therapy). We assessed performance of HEMORR 2 HAGES (hepatic or renal disease, ethanol abuse, malignancy, older age, reduced platelet count or function, hypertension [uncontrolled], anemia, genetic factors, excessive fall risk, and stroke), Shireman, HAS-BLED (hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly, drugs/alcohol concomitantly), ATRIA (Anticoagulation and Risk Factors in Atrial Fibrillation), and ORBIT scores (older age, reduced haemoglobin/haematocrit/history of anaemia, bleeding history, insufficient kidney function, and treatment with antiplatelet) with C statistics and calibration plots. Net benefit of oral anticoagulants was explored by comparing risk reduction in ischemic stroke with risk increase in major bleedings on warfarin. During 6922 person-years of follow-up, 266 patients experienced a major bleed (3.8 per 100 person-years). C statistics ranged from 0.62 (Shireman) to 0.67 (ATRIA). Calibration was poor for ATRIA and moderate for other models. The reduction in recurrent ischemic strokes on warfarin was larger than the increase in major bleeding risk, irrespective of bleeding risk category. Performance of prediction models for major bleeding in patients with cerebral ischemia and atrial fibrillation is modest but comparable with performance in patients with only atrial fibrillation. Bleeding risk scores cannot guide treatment decisions for oral anticoagulants but may still be useful to identify modifiable risk factors for bleeding. Clinical usefulness may be best for ORBIT, which is based on a limited number of easily obtainable variables and showed reasonable performance. © 2017 American Heart Association, Inc.

Propellantless Propulsion Technologies for In-Space Transportation

NASA Technical Reports Server (NTRS)

Johnson, Les; Cook, Stephen (Technical Monitor)

2001-01-01

In order to implement the ambitious science and exploration missions planned over the next several decades, improvements in in-space transportation and propulsion technologies must be achieved. For robotic exploration and science missions, increased efficiencies of future propulsion systems are critical to reduce overall life-cycle costs. Future missions will require 2 to 3 times more total change in velocity over their mission lives than the NASA Solar Electric Technology Application Readiness (NSTAR) demonstration on the Deep Space 1 mission. Rendezvous and return missions will require similar investments in in-space propulsion systems. New opportunities to explore beyond the outer planets and to the stars will require unparalleled technology advancement and innovation. The Advanced Space Transportation Program (ASTP) is investing in technologies to achieve a factor of 10 reduction in the cost of Earth orbital transportation and a factor of 2 or 3 reduction in propulsion system mass and travel time for planetary missions within the next 15 years. Since more than 70% of projected launches over the next 10 years will require propulsion systems capable of attaining destinations beyond Low Earth Orbit, investment in in-space technologies will benefit a large percentage of future missions. Some of the most promising technologies for achieving these goals use the environment of space itself for energy and propulsion and are generically called, "propellantless" because they do not require on-board fuel to achieve thrust. An overview of the state-of-the-art in propellantless propulsion technologies such as solar and plasma sails, electrodynamic and momentum transfer tethers, and aeroassist and aerocapture will be described. Results of recent earth-based technology demonstrations and space tests will also be discussed.

What is the Main Potential Factor Influencing Ocular Protrusion?

PubMed

Li, Yinwei; Su, Yun; Song, Xuefei; Zhou, Huifang; Fan, Xianqun

2017-01-05

BACKGROUND The aim of the present study was to establish the normal-range orbital parameters and to explore the relationships between ocular protrusion and various orbital morphological factors. MATERIAL AND METHODS A retrospective, non-comparative case series was conducted from January 2014 to December 2015. We recruited 56 subjects (112 orbits), including 27 males (21 to 87 years of age) and 29 females (22 to 88 years of age) in this study. Nine length measurements, 2 angle measurements, and 2 volume measurements of various aspects of the orbit were obtained using Mimics v18.0 software. The data were collected manually using a 3D measurement technique. Statistical analyses using t tests and Pearson's correlation analyses were performed to evaluate the differences and relationships between the parameters, respectively. RESULTS Ocular protrusion in both sexes was closely related to the following values: orbital soft tissue volume (OSTV) (males: r=0.61, p<0.001; females: r=0.39, p=0.003), orbital soft tissue volume/bony orbital volume (OSTV/BOV) (males: r=0.90, p<0.001; females: r=0.87, p<0.001), orbital width (males: r=0.40, p=0.003; females: r=0.53, p<0.001), orbital height (males: r=0.29, p=0.038; females: r=0.45, p<0.001), and globe diameter (males: r=0.52, p<0.001; females: r=0.48, p<0.001). No differences were found between the right and left orbits. CONCLUSIONS The study provides insight into the potential factors that influence ocular protrusion, which include the OSTV/BOV ratio, the shape of the orbital aperture, and the ocular axial length. The results of orbital surgery can be made more predictable by accounting for these 3 factors. The database and regression formula might provide support for surgical planning in the future.

GEODYN system support program, volume 4. [computer program for trajectory analysis of artificial satellites

NASA Technical Reports Server (NTRS)

Mullins, N. E.

1972-01-01

The GEODYN Orbit Determination and Geodetic Parameter Estimation System consists of a set of computer programs designed to determine and analyze definitive satellite orbits and their associated geodetic and measurement parameters. This manual describes the Support Programs used by the GEODYN System. The mathematics and programming descriptions are detailed. The operational procedures of each program are presented. GEODYN ancillary analysis programs may be grouped into three different categories: (1) orbit comparison - DELTA (2) data analysis using reference orbits - GEORGE, and (3) pass geometry computations - GROUNDTRACK. All of the above three programs use one or more tapes written by the GEODYN program in either a data reduction or orbit generator run.

KSC-98pc1165

NASA Image and Video Library

1998-09-28

The orbiter Atlantis, being towed from the Shuttle Landing Facility, is reflected in waters from the Banana Creek next to the towway. The orbiter spent 10 months in Palmdale, CA, undergoing extensive inspections and modifications in the orbiter processing facility there. The modifications included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

CallFUSE Version 3: A Data Reduction Pipeline for the Far Ultraviolet Spectroscopic Explorer

DTIC Science & Technology

2007-05-01

Earth orbit with an inclination of 25 to the equator and an approximately 100 minute orbital period. Data obtained with the instrument are reduced...throughout the mis- sion reveal that the gratings’ orbital motion depends on three parameters: beta angle (the angle between the target and the anti- Sun ...University, Bal- timore, MD; wvd@pha.jhu.edu. 3 Space Telescope Science Institute, ESS/SSG, Baltimore, MD. 4 Current address: Earth Orientation Department

STS-1 Pogo analysis

NASA Technical Reports Server (NTRS)

1981-01-01

Some of the pogo related data from STS-1 are documented. The measurements and data reduction are described. In the data analysis reference is made to FRF and single engine test results. The measurements are classified under major project elements of the space shuttle main engine, the external tank, and the orbiter. The subsystems are structural dynamics and main propulsion. Data were recorded onboard the orbiter with a minimum response rate of 1.5 to 50 Hz. The wideband, 14 track recorder was used, and the data required demultiplexing before reduction. The flight phase of interest was from liftoff through main engine cutoff.

Methods to Improve the Maintenance of the Earth Catalog of Satellites During Severe Solar Storms

NASA Technical Reports Server (NTRS)

Wilkin, Paul G.; Tolson, Robert H.

1998-01-01

The objective of this thesis is to investigate methods to improve the ability to maintain the inventory of orbital elements of Earth satellites during periods of atmospheric disturbance brought on by severe solar activity. Existing techniques do not account for such atmospheric dynamics, resulting in tracking errors of several seconds in predicted crossing time. Two techniques are examined to reduce of these tracking errors. First, density predicted from various atmospheric models is fit to the orbital decay rate for a number of satellites. An orbital decay model is then developed that could be used to reduce tracking errors by accounting for atmospheric changes. The second approach utilizes a Kalman filter to estimate the orbital decay rate of a satellite after every observation. The new information is used to predict the next observation. Results from the first approach demonstrated the feasibility of building an orbital decay model based on predicted atmospheric density. Correlation of atmospheric density to orbital decay was as high as 0.88. However, it is clear that contemporary: atmospheric models need further improvement in modeling density perturbations polar region brought on by solar activity. The second approach resulted in a dramatic reduction in tracking errors for certain satellites during severe solar Storms. For example, in the limited cases studied, the reduction in tracking errors ranged from 79 to 25 percent.

[Orbital decompression in Grave's disease: comparison of techniques].

PubMed

Sellari-Franceschini, S; Berrettini, S; Forli, F; Bartalena, L; Marcocci, C; Tanda, M L; Nardi, M; Lepri, A; Pinchera, A

1999-12-01

Grave's ophthalmopathy is an inflammatory, autoimmune disorder often associated with Grave's disease. The inflammatory infiltration involves the retrobulbar fatty tissue and the extrinsic eye muscles, causing proptosis, extraocular muscle dysfunction and often diplopia. Orbital decompression is an effective treatment in such cases, particularly when resistant to drugs and external radiation therapy. This work compares the results of orbital decompression performed by removing: a) the medial and lateral walls (Mourits technique) in 10 patients (19 orbits) and b) the medial and lower walls (Walsh-Ogura technique) in 17 patients (31 orbits). The results show that removing the floor of the orbit enables better reduction of proptosis but more easily leads to post-operative diplopia. Thus it proves necessary to combine the two techniques, modifying the surgical approach on a case-by-case basis.

Space shuttle: Static stability and control investigation of NR/GD delta wing booster (B-20) and delta wing orbiter (134D), volume 4

NASA Technical Reports Server (NTRS)

Allen, E. C., Jr.; Eder, F. W.

1972-01-01

Test results of booster and orbiter models of various component buildup configurations are reported. Dataset Collation Sheets, which give a complete summary of the configurations, are presented along with a description of the test facility. Data reduction procedures are described.

The self-calibration method for multiple systems at the CHARA Array

NASA Astrophysics Data System (ADS)

O'Brien, David

The self-calibration method, a new interferometric technique at the CHARA Array, has been used to derive orbits for several spectroscopic binaries. This method uses the wide component of a hierarchical triple system to calibrate visibility measurements of the triple's close binary system. At certain baselines and separations, the calibrator in one of these systems can be observed quasi-simultaneously with the target. Depending on the orientation of the CHARA observation baseline relative to the orientation of the wide orbit of the triple system, separated fringe packets may be observed. A sophisticated observing scheme must be put in place to ensure the existence of separated fringe packets on nights of observation. Prior to the onset of this project, the reduction of separated fringe packet data had never included the goal of deriving visibilities for both fringe packets, so new data reduction software has been written. Visibilities obtained with separated fringe packet data for the target close binary are run through both Monte Carlo simulations and grid search programs in order to determine the best-fit orbital elements of the close binary. Several targets have been observed in this fashion, and orbits have been derived for seven targets, including three new orbits. Derivation of the orbit of the close pair in a triple system allows for the calculation of the mutual inclination, which is the angle between the planes of the wide and close orbit. Knowledge of this quantity may give insight into the formation processes that create multiple star systems. INDEX WORDS: Long-baseline interferometry, Self calibration, Separated fringe packets, Triple systems, Close binaries, Multiple systems, Orbital parameters, Near-infrared interferometry

An investigation of drag reduction fairings on the space shuttle vehicle 5 configuration (model 74-OTS) in the MSFC 14 inch trisonic wind tunnel (FA14)

NASA Technical Reports Server (NTRS)

Ramsey, P. E.

1976-01-01

An experimental investigation was conducted in the MSFC 14-inch TWT (FA14, TWT 600) to determine the static stability and drag on a 0.004 scale model of the shuttle ascent configuration. The primary objective was to study the possibility of reducing the launch vehicle drag by using Orbiter/ET/SRB fairings, streamlined orbiter fore and aft attach structures, SRB and ET alternative nose configurations, and devices for modifying the flow between the orbiter and ET. The secondary objective was to determine the longitudinal and directional characteristics of the ascent configuration with the most promising of the drag reduction devices installed. Data were obtained for a Mach number range of 0.6 through 4.96 and angles of attack from -5 through 5 degrees at zero degrees side slip angle.

KSC-98pc1166

NASA Image and Video Library

1998-09-28

The orbiter Atlantis, being towed from the Shuttle Landing Facility toward the Vehicle Assembly Building (VAB) , intersects the morning sun's rays. In the background, to the right of the VAB, are the Orbiter Processing Facility 1 and 2. Atlantis spent 10 months in Palmdale, CA, undergoing extensive inspections and modifications in the orbiter processing facility there. The modifications included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. Atlantis will undergo preparations at KSC in Orbiter Processing Facility 2 for its planned flight in June 1999

Time-free transfers between libration-point orbits in the elliptic restricted problem

NASA Astrophysics Data System (ADS)

Howell, K. C.; Hiday-Johnston, L. A.

This work is part of a larger research effort directed toward the formulation of a strategy to design optimal time-free impulsive transfers between three-dimensional libration-point orbits in the vicinity of the interior LI libration point of the Sun-Earth/Moon barycenter system. Inferior transfers that move a spacecraft from a large halo orbit to a smaller halo orbit are considered here. Primer vector theory is applied to non-optimal impulsive trajectories in the elliptic restricted three-body problem in order to establish whether the implementation of a coast in the initial orbit, a coast in the final orbit, or dual coasts accomplishes a reduction in fuel expenditure. The addition of interior impulses is also considered. Results indicate that a substantial savings in fuel can be achieved by the allowance for coastal periods on the specified libration-point orbits. The resulting time-free inferior transfers are compared to time-free superior transfers between halo orbits of equal z-amplitude separation.

Time-free transfers between libration-point orbits in the elliptic restricted problem

NASA Astrophysics Data System (ADS)

Howell, K. C.; Hiday, L. A.

1992-08-01

This work is directed toward the formulation of a strategy to design optimal time-free impulsive transfers between 3D libration-point orbits in the vicinity of the interior L1 libration point of the sun-earth/moon barycenter system. Inferior transfers that move a spacecraft from a large halo orbit to a smaller halo orbit are considered here. Primer vector theory is applied to nonoptimal impulsive trajectories in the elliptic restricted three-body problem in order to establish whether the implementation of a coast in the initial orbit, a coast in the final orbit, or dual coasts accomplishes a reduction in fuel expenditure. The addition of interior impulses is also considered. Results indicate that a substantial savings in fuel can be achieved by the allowance for coastal periods on the specified libration-point orbits. The resulting time-free inferior transfers are compared to time-free superior transfers between halo orbits of equal z-amplitude separation.

Expression of Vascular Endothelial Growth Factor Receptors in Benign Vascular Lesions of the Orbit: A Case Series.

PubMed

Atchison, Elizabeth A; Garrity, James A; Castillo, Francisco; Engman, Steven J; Couch, Steven M; Salomão, Diva R

2016-01-01

Vascular lesions of the orbit, although not malignant, can cause morbidity because of their location near critical structures in the orbit. For the same reason, they can be challenging to remove surgically. Anti-vascular endothelial growth factor (VEGF) drugs are increasingly being used to treat diseases with prominent angiogenesis. Our study aimed to determine to what extent VEGF receptors and their subtypes are expressed on selected vascular lesions of the orbit. Retrospective case series of all orbital vascular lesions removed by one of the authors (JAG) at the Mayo Clinic. A total of 52 patients who underwent removal of vascular orbital lesions. The pathology specimens from the patients were retrieved, their pathologic diagnosis was confirmed, demographic and clinical information were gathered, and sections from vascular tumors were stained with vascular endothelial growth factor receptor (VEGFR), vascular endothelial growth factor receptor type 1 (VEGFR1), vascular endothelial growth factor receptor type 2 (VEGFR2), and vascular endothelial growth factor receptor type 3 (VEGFR3). The existence and pattern of staining with VEGF and its subtypes on these lesions. There were 28 specimens of venous malformations, 4 capillary hemangiomas, 7 lymphatic malformations, and 6 lymphaticovenous malformations. All samples stained with VEGF, 55% stained with VEGFR1, 98% stained with VEGFR2, and 96% stained with VEGFR3. Most (94%) of the VEGFR2 staining was diffuse. Most orbital vascular lesions express VEGF receptors, which may suggest a future target for nonsurgical treatment. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Venus gravity: Summary and coming events

NASA Technical Reports Server (NTRS)

Sjogren, W. L.

1992-01-01

The first significant dataset to provide local measures of venusian gravity field variations was that acquired from the Pioneer Venus Orbiter (PVO) during the 1979-1981 period. These observations were S-band Doppler radio signals from the orbiting spacecraft received at Earth-based tracking stations. Early reductions of these data were performed using two quite different techniques. Estimates of the classical spherical harmonics were made to various degrees and orders up to 10. At that time, solutions of much higher degree and order were very difficult due to computer limitations. These reductions, because of low degree and order, revealed only the most prominent features with poor spatial resolution and very reduced peak amplitudes.

Refinement of planetary protection policy for Mars missions

NASA Technical Reports Server (NTRS)

DeVincenzi, D. L.; Stabekis, P.; Barengoltz, J.

1996-01-01

Under existing COSPAR policy adopted in 1984, missions to Mars (landers, probes, and some orbiters) are designated as Category IV missions. As such, the procedures for implementing planetary protection requirements could include trajectory biasing, cleanrooms, bioload reduction, sterilization of hardware, and bioshields. In 1992, a U.S. National Research Council study recommended that controls on forward contamination of Mars be tied to specific mission objectives. The report recommended that Mars landers with life detection instruments be subject to at least Viking-level sterilization procedures for bioload reduction, while spacecraft (including orbiters) without life detection instruments be subject to at least Viking-level pre-sterilization procedures for bioload reduction but need not be sterilized. In light of this, it is proposed that the current policy's Category IV and its planetary protection requirements be divided into two sub-categories as follows: Category IVa, for missions comprising landers and probes without life detection experiments, which will meet a specified bioburden limit for exposed surfaces, and Category IVb, for landers and probes with life detection experiments, which will require sterilization of landed systems. In addition, Category III orbiter mission specifications are expanded to be consistent with these recommendations.

Probability of coincidental similarity among the orbits of small bodies - I. Pairing

NASA Astrophysics Data System (ADS)

Jopek, Tadeusz Jan; Bronikowska, Małgorzata

2017-09-01

Probability of coincidental clustering among orbits of comets, asteroids and meteoroids depends on many factors like: the size of the orbital sample searched for clusters or the size of the identified group, it is different for groups of 2,3,4,… members. Probability of coincidental clustering is assessed by the numerical simulation, therefore, it depends also on the method used for the synthetic orbits generation. We have tested the impact of some of these factors. For a given size of the orbital sample we have assessed probability of random pairing among several orbital populations of different sizes. We have found how these probabilities vary with the size of the orbital samples. Finally, keeping fixed size of the orbital sample we have shown that the probability of random pairing can be significantly different for the orbital samples obtained by different observation techniques. Also for the user convenience we have obtained several formulae which, for given size of the orbital sample can be used to calculate the similarity threshold corresponding to the small value of the probability of coincidental similarity among two orbits.

Modification of an impulse-factoring orbital transfer technique to account for orbit determination and maneuver execution errors

NASA Technical Reports Server (NTRS)

Kibler, J. F.; Green, R. N.; Young, G. R.; Kelly, M. G.

1974-01-01

A method has previously been developed to satisfy terminal rendezvous and intermediate timing constraints for planetary missions involving orbital operations. The method uses impulse factoring in which a two-impulse transfer is divided into three or four impulses which add one or two intermediate orbits. The periods of the intermediate orbits and the number of revolutions in each orbit are varied to satisfy timing constraints. Techniques are developed to retarget the orbital transfer in the presence of orbit-determination and maneuver-execution errors. Sample results indicate that the nominal transfer can be retargeted with little change in either the magnitude (Delta V) or location of the individual impulses. Additonally, the total Delta V required for the retargeted transfer is little different from that required for the nominal transfer. A digital computer program developed to implement the techniques is described.

Research study: STS-1 Orbiter Descent

NASA Technical Reports Server (NTRS)

Hickey, J. S.

1981-01-01

The conversion of STS-1 orbiter descent data from AVE-SESAME contact programs to the REEDA system and the reduction of raw radiosonde data is summarized. A first difference program, contact data program, plot data program, and 30 second data program were developed. Six radiosonde soundings were taken. An example of the outputs of each of the programs is presented.

Precise Orbit Determination for GEOSAT Follow-On Using Satellite Laser Ranging Data and Intermission Altimeter Crossovers

NASA Technical Reports Server (NTRS)

Lemoine, Frank G.; Rowlands, David D.; Luthcke, Scott B.; Zelensky, Nikita P.; Chinn, Douglas S.; Pavlis, Despina E.; Marr, Gregory

2001-01-01

The US Navy's GEOSAT Follow-On Spacecraft was launched on February 10, 1998 with the primary objective of the mission to map the oceans using a radar altimeter. Following an extensive set of calibration campaigns in 1999 and 2000, the US Navy formally accepted delivery of the satellite on November 29, 2000. Satellite laser ranging (SLR) and Doppler (Tranet-style) beacons track the spacecraft. Although limited amounts of GPS data were obtained, the primary mode of tracking remains satellite laser ranging. The GFO altimeter measurements are highly precise, with orbit error the largest component in the error budget. We have tuned the non-conservative force model for GFO and the gravity model using SLR, Doppler and altimeter crossover data sampled over one year. Gravity covariance projections to 70x70 show the radial orbit error on GEOSAT was reduced from 2.6 cm in EGM96 to 1.3 cm with the addition of SLR, GFO/GFO and TOPEX/GFO crossover data. Evaluation of the gravity fields using SLR and crossover data support the covariance projections and also show a dramatic reduction in geographically-correlated error for the tuned fields. In this paper, we report on progress in orbit determination for GFO using GFO/GFO and TOPEX/GFO altimeter crossovers. We will discuss improvements in satellite force modeling and orbit determination strategy, which allows reduction in GFO radial orbit error from 10-15 cm to better than 5 cm.

Interaction Mode and Regioselectivity in Vitamin B12-Dependent Dehalogenation of Aryl Halides by Dehalococcoides mccartyi Strain CBDB1.

PubMed

Zhang, Shangwei; Adrian, Lorenz; Schüürmann, Gerrit

2018-02-20

The bacterium Dehalococcoides, strain CBDB1, transforms aromatic halides through reductive dehalogenation. So far, however, the structures of its vitamin B 12 -containing dehalogenases are unknown, hampering clarification of the catalytic mechanism and substrate specificity as basis for targeted remediation strategies. This study employs a quantum chemical donor-acceptor approach for the Co(I)-substrate electron transfer. Computational characterization of the substrate electron affinity at carbon-halogen bonds enables discriminating aromatic halides ready for dehalogenation by strain CBDB1 (active substrates) from nondehalogenated (inactive) counterparts with 92% accuracy, covering 86 of 93 bromobenzenes, chlorobenzenes, chlorophenols, chloroanilines, polychlorinated biphenyls, and dibenzo-p-dioxins. Moreover, experimental regioselectivity is predicted with 78% accuracy by a site-specific parameter encoding the overlap potential between the Co(I) HOMO (highest occupied molecular orbital) and the lowest-energy unoccupied sigma-symmetry substrate MO (σ*), and the observed dehalogenation pathways are rationalized with a success rate of 81%. Molecular orbital analysis reveals that the most reactive unoccupied sigma-symmetry orbital of carbon-attached halogen X (σ C-X * ) mediates its reductive cleavage. The discussion includes predictions for untested substrates, thus providing opportunities for targeted experimental investigations. Overall, the presently introduced orbital interaction model supports the view that with bacterial strain CBDB1, an inner-sphere electron transfer from the supernucleophile B 12 Co(I) to the halogen substituent of the aromatic halide is likely to represent the rate-determining step of the reductive dehalogenation.

OARE flight maneuvers and calibration measurements on STS-58

NASA Technical Reports Server (NTRS)

Blanchard, Robert C.; Nicholson, John Y.; Ritter, James R.; Larman, Kevin T.

1994-01-01

The Orbital Acceleration Research Experiment (OARE), which has flown on STS-40, STS-50, and STS-58, contains a three axis accelerometer with a single, nonpendulous, electrostatically suspended proofmass which can resolve accelerations to the nano-g level. The experiment also contains a full calibration station to permit in situ bias and scale factor calibration. This on-orbit calibration capability eliminates the large uncertainty of ground-based calibrations encountered with accelerometers flown in the past on the orbiter, thus providing absolute acceleration measurement accuracy heretofore unachievable. This is the first time accelerometer scale factor measurements have been performed on orbit. A detailed analysis of the calibration process is given along with results of the calibration factors from the on-orbit OARE flight measurements on STS-58. In addition, the analysis of OARE flight maneuver data used to validate the scale factor measurements in the sensor's most sensitive range is also presented. Estimates on calibration uncertainties are discussed. This provides bounds on the STS-58 absolute acceleration measurements for future applications.

Development of New Open-Shell Perturbation and Coupled-Cluster Theories Based on Symmetric Spin Orbitals

NASA Technical Reports Server (NTRS)

Lee, Timothy J.; Arnold, James O. (Technical Monitor)

1994-01-01

A new spin orbital basis is employed in the development of efficient open-shell coupled-cluster and perturbation theories that are based on a restricted Hartree-Fock (RHF) reference function. The spin orbital basis differs from the standard one in the spin functions that are associated with the singly occupied spatial orbital. The occupied orbital (in the spin orbital basis) is assigned the delta(+) = 1/square root of 2(alpha+Beta) spin function while the unoccupied orbital is assigned the delta(-) = 1/square root of 2(alpha-Beta) spin function. The doubly occupied and unoccupied orbitals (in the reference function) are assigned the standard alpha and Beta spin functions. The coupled-cluster and perturbation theory wave functions based on this set of "symmetric spin orbitals" exhibit much more symmetry than those based on the standard spin orbital basis. This, together with interacting space arguments, leads to a dramatic reduction in the computational cost for both coupled-cluster and perturbation theory. Additionally, perturbation theory based on "symmetric spin orbitals" obeys Brillouin's theorem provided that spin and spatial excitations are both considered. Other properties of the coupled-cluster and perturbation theory wave functions and models will be discussed.

Photoinduced Hund excitons in the breakdown of a two-orbital Mott insulator

NASA Astrophysics Data System (ADS)

Rincón, Julián; Dagotto, Elbio; Feiguin, Adrian E.

2018-06-01

We study the photoinduced breakdown of a two-orbital Mott insulator and resulting metallic state. Using time-dependent density matrix renormalization group, we scrutinize the real-time dynamics of the half-filled two-orbital Hubbard model interacting with a resonant radiation field pulse. The breakdown, caused by production of doublon-holon pairs, is enhanced by Hund's exchange, which dynamically activates large orbital fluctuations. The melting of the Mott insulator is accompanied by a high to low spin transition with a concomitant reduction of antiferromagnetic spin fluctuations. Most notably, the overall time response is driven by the photogeneration of excitons with orbital character that are stabilized by Hund's coupling. These unconventional "Hund excitons" correspond to bound spin-singlet orbital-triplet doublon-holon pairs. We study exciton properties such as bandwidth, binding potential, and size within a semiclassical approach. The photometallic state results from a coexistence of Hund excitons and doublon-holon plasma.

Pressure loads and aerodynamic force information for the -89A space shuttle orbiter configuration, volume 2

NASA Technical Reports Server (NTRS)

Mennell, R. C.

1973-01-01

Experimental aerodynamic investigations were conducted in a low speed wind tunnel on an 0.0405 scale representation of the 89A light weight Space Shuttle Orbiter to obtain pressure loads data in the presence of the ground for orbiter structural strength analysis. The model and the facility are described, and data reduction is outlined. Tables are included for data set/run number collation, data set/component collation, model component description, and pressure tap locations by series number. Tabulated force and pressure source data are presented.

A pair natural orbital implementation of the coupled cluster model CC2 for excitation energies.

PubMed

Helmich, Benjamin; Hättig, Christof

2013-08-28

We demonstrate how to extend the pair natural orbital (PNO) methodology for excited states, presented in a previous work for the perturbative doubles correction to configuration interaction singles (CIS(D)), to iterative coupled cluster methods such as the approximate singles and doubles model CC2. The original O(N(5)) scaling of the PNO construction is reduced by using orbital-specific virtuals (OSVs) as an intermediate step without spoiling the initial accuracy of the PNO method. Furthermore, a slower error convergence for charge-transfer states is analyzed and resolved by a numerical Laplace transformation during the PNO construction, so that an equally accurate treatment of local and charge-transfer excitations is achieved. With state-specific truncated PNO expansions, the eigenvalue problem is solved by combining the Davidson algorithm with deflation to project out roots that have already been determined and an automated refresh with a generation of new PNOs to achieve self-consistency of the PNO space. For a large test set, we found that truncation errors for PNO-CC2 excitation energies are only slightly larger than for PNO-CIS(D). The computational efficiency of PNO-CC2 is demonstrated for a large organic dye, where a reduction of the doubles space by a factor of more than 1000 is obtained compared to the canonical calculation. A compression of the doubles space by a factor 30 is achieved by a unified OSV space only. Moreover, calculations with the still preliminary PNO-CC2 implementation on a series of glycine oligomers revealed an early break even point with a canonical RI-CC2 implementation between 100 and 300 basis functions.

Orbital selective directional conductor in the two-orbital Hubbard model

DOE PAGES

Mukherjee, Anamitra; Patel, Niravkumar D.; Moreo, Adriana; ...

2016-02-29

Recently, we employed a developed many-body technique that allows for the incorporation of thermal effects, the rich phase diagram of a two-dimensional two-orbital (degenerate d xz and d yz) Hubbard model is presented varying temperature and the repulsion U. The main result is the finding at intermediate U of an antiferromagnetic orbital selective state where an effective dimensional reduction renders one direction insulating and the other metallic. Possible realizations of this state are discussed. Additionally, we also study nematicity above the N eel temperature. After a careful finite-size scaling analysis, the nematicity temperature window appears to survive in the bulkmore » limit, although it is very narrow.« less

The crucial role of the Green Sahara in damping ENSO variability during the Holocene

NASA Astrophysics Data System (ADS)

Pausata, Francesco S. R.; Zhang, Qiong; Muschitiello, Francesco; Stager, Curt

2016-04-01

Several paleoclimate records show that the ENSO variability may have been remarkably smaller during the mid Holocene (MH) relative to today; however, MH model simulations in which only the orbital forcing is taken into account are not able to fully capture the magnitude of this change. We use a fully coupled simulation for 6000 yr BP (MH) in which we prescribed not only the MH orbital forcing but also Saharan vegetation and reduced dust concentrations. By performing a set of idealized experiments in which each forcing is changed in turn, we show that when accounting for both vegetated Sahara and reduced dust concentrations, the amplitude of the ENSO cycle and its variability are remarkably reduced (~25%) compared to case when only the orbital forcing is prescribed (only 7%). The changes in ENSO behavior are accompanied by damping of the Atlantic El Niño variability (almost 50%). The simulated changes in equatorial variability are connected to the momentous strengthening of the WAM monsoon, which extents all the way to the northernmost part of the Sahara desert. Such changes in the WAM and in the atmospheric circulation over the equatorial Atlantic led to a reduction of the Atlantic El Niño variability and affect ENSO behavior through the atmospheric circulation bridge between the Atlantic and the Pacific. Hence, our results suggest orbital forcing is likely not the only forcing at play behind the changes in ENSO behavior and point to the changes over equatorial Atlantic connected to the Sahara greening as a crucial factor in altering the ENSO spatiotemporal characteristic during the MH.

Obesity Reduction Black Intervention Trial (ORBIT): Design and Baseline Characteristics

PubMed Central

Stolley, Melinda; Schiffer, Linda; Sharp, Lisa; Singh, Vicky; Van Horn, Linda; Dyer, Alan

2008-01-01

Abstract Background Obesity is associated with many chronic diseases, and weight loss can reduce the risk of developing these diseases. Obesity is highly prevalent among Black women, but weight loss treatment for black women has been understudied until recently. The Obesity Reduction black Intervention Trial (ORBIT) is a randomized controlled trial designed to assess the efficacy of a culturally proficient weight loss and weight loss maintenance program for black women. This paper describes the design of the trial, the intervention, and baseline characteristics of the participants. Methods Two hundred thirteen obese black women aged 30–65 years were randomized to the intervention group or a general health control group. The intervention consists of a 6-month weight loss program followed by a 1-year maintenance program. Weight, dietary intake, and energy expenditure are measured at baseline, 6 months, and 18 months. Results More than 40% of participants had a baseline body mass index (BMI) >40 kg/m2 (class III obesity). Intake of fat and saturated fat was higher and consumption of fruit, vegetables, and fiber was lower than currently recommended guidelines. Self-reported moderate to vigorous physical activity was high (median 85 min/day). However, objectively measured physical activity among a subgroup of participants was lower (median 15 min/day). Conclusions Weight loss among obese black women has received inadequate attention in relation to the magnitude of the problem. Factors that contribute to successful weight loss and more importantly, weight loss maintenance need to be identified. PMID:18774895

Orbital exenteration after transarterial embolization in a patient with Wyburn-Mason syndrome: pathological findings.

PubMed

Matsuo, Toshihiko; Yanai, Hiroyuki; Sugiu, Kenji; Tominaga, Susumu; Kimata, Yoshihiro

2008-01-01

We present the pathological findings at orbital exenteration in a patient with Wyburn-Mason syndrome who underwent transarterial embolization. A 31-year-old man with a 10-year history of gradual exacerbation of left exophthalmos and left cheek swelling was found to have facial and orbital arteriovenous malformations on the left side. There was no vascular malformation in the brain. The feeding arteries derived from the left internal maxillary artery, facial artery, and ophthalmic artery. He underwent several courses of transarterial embolization of the feeding arteries from the left internal maxillary artery and then from the facial artery, resulting in no reduction of the arteriovenous malformation. He finally elected to undergo ophthalmic artery embolization in the expectation of a reduction and with the understanding that he would lose sight in his left eye. Two years later, he requested lid-sparing orbital exenteration and reconstruction with cutaneous flap transfer and prosthesis for cosmetic reasons. Pathologically, orbital vascular channels of varying sizes were filled with embolizing glue and had degenerating vascular wall cells surrounded by inflammatory cell infiltration. The central retinal artery in the optic nerve was also filled with the embolizing glue, and the retina lost the ganglion cell layer and inner nuclear layer but maintained the outer nuclear layer and outer segments. Marked anastomoses and hence incomplete embolization among the feeding arteries of facial and orbital vascular malformations in Wyburn-Mason syndrome do not respond well to attempts at feeding vessel embolization, which result in unsuccessful closure of the malformation.

The Effect of Host Star Spectral Energy Distribution and Ice-Albedo Feedback on the Climate of Extrasolar Planets

PubMed Central

Meadows, Victoria S.; Bitz, Cecilia M.; Pierrehumbert, Raymond T.; Joshi, Manoj M.; Robinson, Tyler D.

2013-01-01

Abstract Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO2 (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO2 in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice coverage. The surface ice-albedo feedback effect becomes less important at the outer edge of the habitable zone, where atmospheric CO2 could be expected to be high such that it maintains clement conditions for surface liquid water. We showed that ∼3–10 bar of CO2 will entirely mask the climatic effect of ice and snow, leaving the outer limits of the habitable zone unaffected by the spectral dependence of water ice and snow albedo. However, less CO2 is needed to maintain open water for a planet orbiting an M-dwarf star than would be the case for hotter main-sequence stars. Key Words: Extrasolar planets—M stars—Habitable zone—Snowball Earth. Astrobiology 13, 715–739. PMID:23855332

The effect of host star spectral energy distribution and ice-albedo feedback on the climate of extrasolar planets.

PubMed

Shields, Aomawa L; Meadows, Victoria S; Bitz, Cecilia M; Pierrehumbert, Raymond T; Joshi, Manoj M; Robinson, Tyler D

2013-08-01

Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice coverage. The surface ice-albedo feedback effect becomes less important at the outer edge of the habitable zone, where atmospheric CO(2) could be expected to be high such that it maintains clement conditions for surface liquid water. We showed that ∼3-10 bar of CO(2) will entirely mask the climatic effect of ice and snow, leaving the outer limits of the habitable zone unaffected by the spectral dependence of water ice and snow albedo. However, less CO(2) is needed to maintain open water for a planet orbiting an M-dwarf star than would be the case for hotter main-sequence stars.

Time-fixed rendezvous by impulse factoring with an intermediate timing constraint. [for transfer orbits

NASA Technical Reports Server (NTRS)

Green, R. N.; Kibler, J. F.; Young, G. R.

1974-01-01

A method is presented for factoring a two-impulse orbital transfer into a three- or four-impulse transfer which solves the rendezvous problem and satisfies an intermediate timing constraint. Both the time of rendezvous and the intermediate time of a alinement are formulated as any element of a finite sequence of times. These times are integer multiples of a constant plus an additive constant. The rendezvous condition is an equality constraint, whereas the intermediate alinement is an inequality constraint. The two timing constraints are satisfied by factoring the impulses into collinear parts that vectorially sum to the original impulse and by varying the resultant period differences and the number of revolutions in each orbit. Five different types of solutions arise by considering factoring either or both of the two impulses into two or three parts with a limit for four total impulses. The impulse-factoring technique may be applied to any two-impulse transfer which has distinct orbital periods.

Initial On-Orbit Radiometric Calibration of the Suomi NPP VIIRS Reflective Solar Bands

NASA Technical Reports Server (NTRS)

Lei, Ning; Wang, Zhipeng; Fulbright, Jon; Lee, Shihyan; McIntire, Jeff; Chiang, Vincent; Xiong, Jack

2012-01-01

The on-orbit radiometric response calibration of the VISible/Near InfraRed (VISNIR) and the Short-Wave InfraRed (SWIR) bands of the Visible/Infrared Imager/Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (NPP) satellite is carried out through a Solar Diffuser (SD). The transmittance of the SD screen and the SD's Bidirectional Reflectance Distribution Function (BRDF) are measured before launch and tabulated, allowing the VIIRS sensor aperture spectral radiance to be accurately determined. The radiometric response of a detector is described by a quadratic polynomial of the detector?s digital number (dn). The coefficients were determined before launch. Once on orbit, the coefficients are assumed to change by a common factor: the F-factor. The radiance scattered from the SD allows the determination of the F-factor. In this Proceeding, we describe the methodology and the associated algorithms in the determination of the F-factors and discuss the results.

Lateral orbitotomy for treatment of an orbital abscess in a dog.

PubMed

Vallefuoco, R; Molas, C; Moissonnier, P; Chahory, S

2014-10-01

A two-year-old Jack Russell terrier was diagnosed with a retrobulbar abscess and orbital cellulitis. The diagnosis was confirmed by ultrasound, magnetic resonance imaging examination and ultrasound-guided fine-needle aspiration. Transoral ventral drainage was attempted but was unsuccessful. The abscess was successfully treated by open drainage through a lateral orbitotomy. Despite the exposure of the orbital structures, the orbital soft tissues healed by second intention without further complications. The open drainage was well tolerated and resulted in immediate reduction of inflammation and pain, allowing a quick recovery. This report describes the diagnosis and, surgical management and the long-term (3 years) follow-up of an unusual case of orbital abscess associated with diffuse periorbital cellulitis successfully treated by open drainage through a lateral orbitotomy. © 2014 British Small Animal Veterinary Association.

Sentinel-1A - First precise orbit determination results

NASA Astrophysics Data System (ADS)

Peter, H.; Jäggi, A.; Fernández, J.; Escobar, D.; Ayuga, F.; Arnold, D.; Wermuth, M.; Hackel, S.; Otten, M.; Simons, W.; Visser, P.; Hugentobler, U.; Féménias, P.

2017-09-01

Sentinel-1A is the first satellite of the European Copernicus programme. Equipped with a Synthetic Aperture Radar (SAR) instrument the satellite was launched on April 3, 2014. Operational since October 2014 the satellite delivers valuable data for more than two years. The orbit accuracy requirements are given as 5 cm in 3D. In order to fulfill this stringent requirement the precise orbit determination (POD) is based on the dual-frequency GPS observations delivered by an eight-channel GPS receiver. The Copernicus POD (CPOD) Service is in charge of providing the orbital and auxiliary products required by the PDGS (Payload Data Ground Segment). External orbit validation is regularly performed by comparing the CPOD Service orbits to orbit solutions provided by POD expert members of the Copernicus POD Quality Working Group (QWG). The orbit comparisons revealed systematic orbit offsets mainly in radial direction (approx. 3 cm). Although no independent observation technique (e.g. DORIS, SLR) is available to validate the GPS-derived orbit solutions, comparisons between the different antenna phase center variations and different reduced-dynamic orbit determination approaches used in the various software packages helped to detect the cause of the systematic offset. An error in the given geometry information about the satellite has been found. After correction of the geometry the orbit validation shows a significant reduction of the radial offset to below 5 mm. The 5 cm orbit accuracy requirement in 3D is fulfilled according to the results of the orbit comparisons between the different orbit solutions from the QWG.

Evaluation of Spin Hamiltonian Parameters and Local Structure of Cu2+-doped Ion in xK2SO4-(50 - x)Na2SO4-50ZnSO4 Glasses with Various K2SO4 Concentrations

NASA Astrophysics Data System (ADS)

Ding, Ch.-Ch.; Wu, Sh.-Y.; Xu, Y.-Q.; Zhang, L.-J.; He, J.-J.

2018-03-01

The spin Hamiltonian parameters (SHPs), i.e., g factors and hyperfine structure constants, and local structures are theoretically studied by analyzing tetragonally elongated 3d9 clusters for Cu2+ in xK2SO4-(50 - x)Na2SO4-50ZnSO4 glasses with various K2SO4 concentrations x. The concentration dependences of the SHPs are attributed to the parabolic decreases of the cubic field parameter Dq, orbital reduction factor k, relative tetragonal elongation ratio τ, and core polarization constant κ with x. The [CuO6]10- clusters are found to undergo significant elongations of about 17% due to the Jahn-Teller effect. The calculated cubic field splittings and the SHPs at various concentrations agree well with the experimental data.

Precise Tracking of the Magellan and Pioneer Venus Orbiters by Same-Beam Interferometry. Part 2: Orbit Determination Analysis

NASA Technical Reports Server (NTRS)

Folkner, W. M.; Border, J. S.; Nandi, S.; Zukor, K. S.

1993-01-01

A new radio metric positioning technique has demonstrated improved orbit determination accuracy for the Magellan and Pioneer Venus Orbiter orbiters. The new technique, known as Same-Beam Interferometry (SBI), is applicable to the positioning of multiple planetary rovers, landers, and orbiters which may simultaneously be observed in the same beamwidth of Earth-based radio antennas. Measurements of carrier phase are differenced between spacecraft and between receiving stations to determine the plane-of-sky components of the separation vector(s) between the spacecraft. The SBI measurements complement the information contained in line-of-sight Doppler measurements, leading to improved orbit determination accuracy. Orbit determination solutions have been obtained for a number of 48-hour data arcs using combinations of Doppler, differenced-Doppler, and SBI data acquired in the spring of 1991. Orbit determination accuracy is assessed by comparing orbit solutions from adjacent data arcs. The orbit solution differences are shown to agree with expected orbit determination uncertainties. The results from this demonstration show that the orbit determination accuracy for Magellan obtained by using Doppler plus SBI data is better than the accuracy achieved using Doppler plus differenced-Doppler by a factor of four and better than the accuracy achieved using only Doppler by a factor of eighteen. The orbit determination accuracy for Pioneer Venus Orbiter using Doppler plus SBI data is better than the accuracy using only Doppler data by 30 percent.

Sensitivity of Pliocene ice sheets to orbital forcing

USGS Publications Warehouse

Dolan, A.M.; Haywood, A.M.; Hill, D.J.; Dowsett, H.J.; Hunter, S.J.; Lunt, D.J.; Pickering, S.J.

2011-01-01

The stability of the Earth's major ice sheets is a critical uncertainty in predictions of future climate and sea level change. One method of investigating the behaviour of the Greenland and the Antarctic ice sheets in a warmer-than-modern climate is to look back at past warm periods of Earth history, for example the Pliocene. This paper presents climate and ice sheet modelling results for the mid-Pliocene warm period (mPWP; 3.3 to 3.0 million years ago), which has been identified as a key interval for understanding warmer-than-modern climates (Jansen et al., 2007). Using boundary conditions supplied by the United States Geological Survey PRISM Group (Pliocene Research, Interpretation and Synoptic Mapping), the Hadley Centre coupled ocean–atmosphere climate model (HadCM3) and the British Antarctic Survey Ice Sheet Model (BASISM), we show large reductions in the Greenland and East Antarctic Ice Sheets (GrIS and EAIS) compared to modern in standard mPWP experiments. We also present the first results illustrating the variability of the ice sheets due to realistic orbital forcing during the mid-Pliocene. While GrIS volumes are lower than modern under even the most extreme (cold) mid-Pliocene orbit (losing at least 35% of its ice mass), the EAIS can both grow and shrink, losing up to 20% or gaining up to 10% of its present-day volume. The changes in ice sheet volume incurred by altering orbital forcing alone means that global sea level can vary by more than 25 m during the mid-Pliocene. However, we have also shown that the response of the ice sheets to mPWP orbital hemispheric forcing can be in anti-phase, whereby the greatest reductions in EAIS volume are concurrent with the smallest reductions of the GrIS. If this anti-phase relationship is in operation throughout the mPWP, then the total eustatic sea level response would be dampened compared to the ice sheet fluctuations that are theoretically possible. This suggests that maximum eustatic sea level rise does not correspond to orbital maxima, but occurs at times where the anti-phasing of Northern and Southern Hemisphere ice sheet retreat is minimised.

Photovoltaic solar array technology required for three wide scale generating systems for terrestrial applications: rooftop, solar farm, and satellite

NASA Technical Reports Server (NTRS)

Berman, P. A.

1972-01-01

Three major options for wide-scale generation of photovoltaic energy for terrestrial use are considered: (1) rooftop array, (2) solar farm, and (3) satellite station. The rooftop array would use solar cell arrays on the roofs of residential or commercial buildings; the solar farm would consist of large ground-based arrays, probably in arid areas with high insolation; and the satellite station would consist of an orbiting solar array, many square kilometers in area. The technology advancement requirements necessary for each option are discussed, including cost reduction of solar cells and arrays, weight reduction, resistance to environmental factors, reliability, and fabrication capability, including the availability of raw materials. The majority of the technology advancement requirements are applicable to all three options, making possible a flexible basic approach regardless of the options that may eventually be chosen. No conclusions are drawn as to which option is most advantageous, since the feasibility of each option depends on the success achieved in the technology advancement requirements specified.

Cryogenic Boil-Off Reduction System Testing

NASA Technical Reports Server (NTRS)

Plachta, David W.; Johnson, Wesley L.; Feller, Jeffery

2014-01-01

The Cryogenic Boil-Off Reduction System was tested with LH2 and LOX in a vacuum chamber to simulate space vacuum and the temperatures of low Earth orbit. Testing was successful and results validated the scaling study model that predicts active cooling reduces upper stage cryogenic propulsion mass for loiter periods greater than 2 weeks.

Orbital motion (3rd revised and enlarged edition)

NASA Astrophysics Data System (ADS)

Roy, A. E.

The fundamental principles of celestial mechanics are discussed in an introduction for students of astronomy, aerospace engineering, and geography. Chapters are devoted to the dynamic structure of the universe, coordinate and timekeeping systems, the reduction of observational data, the two-body problem, the many-body problem, general and special perturbations, and the stability and evolution of the solar system. Consideration is given to lunar theory, artificial satellites, rocket dynamics and transfer orbits, interplanetary and lunar trajectories, orbit determination and interplanetary navigation, binaries and other few-body systems, and many-body systems of stars. Diagrams, graphs, tables, and problems with solutions are provided.

Optimization of the rocket mode trajectory in a rocket based combined cycle (RBCC) engine powered SSTO vehicle

NASA Astrophysics Data System (ADS)

Foster, Richard W.

1989-07-01

The application of rocket-based combined cycle (RBCC) engines to booster-stage propulsion, in combination with all-rocket second stages in orbital-ascent missions, has been studied since the mid-1960s; attention is presently given to the case of the 'ejector scramjet' RBCC configuration's application to SSTO vehicles. While total mass delivered to initial orbit is optimized at Mach 20, payload delivery capability to initial orbit optimizes at Mach 17, primarily due to the reduction of hydrogen fuel tankage structure, insulation, and thermal protection system weights.

Space Shuttle Orbiter windshield bird impact analysis

NASA Technical Reports Server (NTRS)

Edelstein, Karen S.; Mccarty, Robert E.

1988-01-01

The NASA Space Shuttle Orbiter's windshield employs three glass panes separated by air gaps. The brittleness of the glass offers much less birdstrike energy-absorption capability than the laminated polycarbonate windshields of more conventional aircraft; attention must accordingly be given to the risk of catastrophic bird impact, and to methods of strike prevention that address bird populations around landing sites rather than the modification of the window's design. Bird populations' direct reduction, as well as careful scheduling of Orbiter landing times, are suggested as viable alternatives. The question of birdstrike-resistant glass windshield design for hypersonic aerospacecraft is discussed.

Orbital transfer vehicle launch operations study. Volume 2: Detailed summary

NASA Technical Reports Server (NTRS)

1986-01-01

A series of Operational Design Drivers were identified. Several of these could have significant impact(s) on program costs. These recommendations, for example, include such items as: complete factory assembly and checkout prior to shipment to the ground launch site to make significant reductions in time required at the launch site as well as overall manpower required to do this work; minimize use of nonstandard equipment when orbiter provided equipment is available; and require commonality (or interchangeability) of subsystem equipment elements that are common to the space station, Orbit Maneuvering Vehicles, and/or Orbit Transfer Vehicles. Several additional items were identified that will require a significant amount of management attention (and direction) to resolve. Key elements of the space based processing plans are discussed.

New Propulsion Technologies For Exploration of the Solar System and Beyond

NASA Technical Reports Server (NTRS)

Johnson, Les; Cook, Stephen (Technical Monitor)

2001-01-01

In order to implement the ambitious science and exploration missions planned over the next several decades, improvements in in-space transportation and propulsion technologies must be achieved. For robotic exploration and science missions, increased efficiencies of future propulsion systems are critical to reduce overall life-cycle costs. Future missions will require 2 to 3 times more total change in velocity over their mission lives than the NASA Solar Electric Technology Application Readiness (NSTAR) demonstration on the Deep Space 1 mission. Rendezvous and return missions will require similar investments in in-space propulsion systems. New opportunities to explore beyond the outer planets and to the stars will require unparalleled technology advancement and innovation. The Advanced Space Transportation Program (ASTP) is investing in technologies to achieve a factor of 10 reduction in the cost of Earth orbital transportation and a factor of 2 reduction in propulsion system mass and travel time for planetary missions within the next 15 years. Since more than 70% of projected launches over the next 10 years will require propulsion systems capable of attaining destinations beyond Low Earth Orbit, investment in in-space technologies will benefit a large percentage of future missions. The ASTP technology portfolio includes many advanced propulsion systems. From the next generation ion propulsion system operating in the 5 - 10 kW range, to fission-powered multi-kilowatt systems, substantial advances in spacecraft propulsion performance are anticipated. Some of the most promising technologies for achieving these goals use the environment of space itself for energy and propulsion and are generically called, "propellantless" because they do not require on-board fuel to achieve thrust. An overview of the state-of-the-art in propellantless propulsion technologies such as solar and plasma sails, electrodynamic and momentum transfer tethers, and aeroassist and aerocapture will also be described. Results of recent earth-based technology demonstrations and space tests for many of these new propulsion technologies will be discussed.

Dimensionality Control of d-orbital Occupation in Oxide Superlattices

PubMed Central

Jeong, Da Woon; Choi, Woo Seok; Okamoto, Satoshi; Kim, Jae–Young; Kim, Kyung Wan; Moon, Soon Jae; Cho, Deok–Yong; Lee, Ho Nyung; Noh, Tae Won

2014-01-01

Manipulating the orbital state in a strongly correlated electron system is of fundamental and technological importance for exploring and developing novel electronic phases. Here, we report an unambiguous demonstration of orbital occupancy control between t2g and eg multiplets in quasi-two-dimensional transition metal oxide superlattices (SLs) composed of a Mott insulator LaCoO3 and a band insulator LaAlO3. As the LaCoO3 sublayer thickness approaches its fundamental limit (i.e. one unit-cell-thick), the electronic state of the SLs changed from a Mott insulator, in which both t2g and eg orbitals are partially filled, to a band insulator by completely filling (emptying) the t2g (eg) orbitals. We found the reduction of dimensionality has a profound effect on the electronic structure evolution, which is, whereas, insensitive to the epitaxial strain. The remarkable orbital controllability shown here offers a promising pathway for novel applications such as catalysis and photovoltaics, where the energy of d level is an essential parameter. PMID:25134975

Photoinduced Hund excitons in the breakdown of a two-orbital Mott insulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rincon, Julian; Dagotto, Elbio R.; Feiguin, Adrian E.

We study the photoinduced breakdown of a two-orbital Mott insulator and resulting metallic state. Using time-dependent density matrix renormalization group, we scrutinize the real-time dynamics of the half-filled two-orbital Hubbard model interacting with a resonant radiation field pulse. The breakdown, caused by production of doublon-holon pairs, is enhanced by Hund's exchange, which dynamically activates large orbital fluctuations. The melting of the Mott insulator is accompanied by a high to low spin transition with a concomitant reduction of antiferromagnetic spin fluctuations. Most notably, the overall time response is driven by the photogeneration of excitons with orbital character that are stabilized bymore » Hund's coupling. These unconventional “Hund excitons” correspond to bound spin-singlet orbital-triplet doublon-holon pairs. We study exciton properties such as bandwidth, binding potential, and size within a semiclassical approach. In conclusion, the photometallic state results from a coexistence of Hund excitons and doublon-holon plasma.« less

Photoinduced Hund excitons in the breakdown of a two-orbital Mott insulator

DOE PAGES

Rincon, Julian; Dagotto, Elbio R.; Feiguin, Adrian E.

2018-06-05

We study the photoinduced breakdown of a two-orbital Mott insulator and resulting metallic state. Using time-dependent density matrix renormalization group, we scrutinize the real-time dynamics of the half-filled two-orbital Hubbard model interacting with a resonant radiation field pulse. The breakdown, caused by production of doublon-holon pairs, is enhanced by Hund's exchange, which dynamically activates large orbital fluctuations. The melting of the Mott insulator is accompanied by a high to low spin transition with a concomitant reduction of antiferromagnetic spin fluctuations. Most notably, the overall time response is driven by the photogeneration of excitons with orbital character that are stabilized bymore » Hund's coupling. These unconventional “Hund excitons” correspond to bound spin-singlet orbital-triplet doublon-holon pairs. We study exciton properties such as bandwidth, binding potential, and size within a semiclassical approach. In conclusion, the photometallic state results from a coexistence of Hund excitons and doublon-holon plasma.« less

Is It Time for Space Debris Reduction Capabilities?

DTIC Science & Technology

2009-04-01

The original document contains color images . 14. ABSTRACT For over 50 years, space-faring nations have launched objects into space, resulting in...have seen an increased risk of collision. Most debris resides in low earth orbit (the satellite freeway where bulk of imaging satellites reside... imaging , radar, etc). The close proximity to the Earth allows for images and photographs to be captured in greater detail than higher orbits

Treatment of traumatic infra orbital nerve paresthesia

PubMed Central

Lone, Parveen Akhter; Singh, R. K.; Pal, U. S.

2012-01-01

This study was done to find out the role of topiramate therapy in infraorbital nerve paresthesia after miniplate fixation in zygomatic complxex fractures. A total 2 cases of unilateral zygomatic complex fracture, 2-3 weeks old with infra orbital nerve paresthesia were slected. Open reduction and plating was done in frontozygomaticregion. Antiepileptic drug tab topiramate was given in therapeutic doses and dose was increased slowly until functional recovery was noticed. PMID:23833503

Adsorption-induced symmetry reduction of metal-phthalocyanines studied by vibrational spectroscopy

NASA Astrophysics Data System (ADS)

Sforzini, J.; Bocquet, F. C.; Tautz, F. S.

2017-10-01

We investigate the vibrational properties of Pt- and Pd-phthalocyanine (PtPc and PdPc) molecules on Ag(111) with high-resolution electron energy loss spectroscopy (HREELS). In the monolayer regime, both molecules exhibit long-range order. The vibrational spectra prove a flat adsorption geometry. The redshift of specific vibrational modes suggests a moderate interaction of the molecules with the substrate. The presence of asymmetric vibrational peaks indicates an interfacial dynamical charge transfer (IDCT). The molecular orbital that is involved in IDCT is the former Eg lowest unoccupied molecular orbital (LUMO) of the molecules that becomes partially occupied upon adsorption. A group-theoretical analysis of the IDCT modes, based on calculated vibrational frequencies and line shape fits, provides proof for the reduction of the symmetry of the molecule-substrate complex from fourfold D4 h to C2 v(σv) , Cs(σv) , or C2 and the ensuing lifting of the degeneracy of the former LUMO of the molecule. The vibration-based analysis of orbital degeneracies, as carried out here for PtPc/Ag(111) and PdPc/Ag(111), is particularly useful whenever the presence of multiple molecular in-plane orientations at the interface makes the analysis of orbital degeneracies with angle-resolved photoemission spectroscopy difficult.

Piezosurgery for orbital decompression surgery in thyroid associated orbitopathy.

PubMed

Ponto, Katharina A; Zwiener, Isabella; Al-Nawas, Bilal; Kahaly, George J; Otto, Anna F; Karbach, Julia; Pfeiffer, Norbert; Pitz, Susanne

2014-12-01

The purpose of this study was to assess a piezosurgical device as a novel tool for bony orbital decompression surgery. At a multidisciplinary orbital center, 62 surgeries were performed in 40 patients with thyroid associated orbitopathy (TAO). Within this retrospective case-series, we analyzed the medical records of these consecutive unselected patients. The reduction of proptosis was the main outcome measure. Indications for a two (n = 27, 44%) or three wall (35, 56%) decompression surgery were proptosis (n = 50 orbits, 81%) and optic neuropathy (n = 12, 19%). Piezosurgery enabled precise bone cuts without intraoperative complications. Proptosis decreased from 23.6 ± 2.8 mm (SD) by 3 mm (95% CI: -3.6 to -2.5 mm) after surgery and stayed stable at 3 months (-3 mm, 95% CI: -3.61 to -2.5 mm, p < 0.001, respectively). The effect was higher in those with preoperatively higher values (>24 mm versus ≤ 24 mm: -3.4 mm versus -2.81 mm before discharge from hospital and -4.1 mm versus -2.1 mm at 3 months: p < 0.001, respectively). After a mean long-term follow-up period of 14.6 ± 10.4 months proptosis decreased by further -0.7 ± 2.0 mm (p < 0.001). Signs of optic nerve compression improved after surgery. Infraorbital hypesthesia was present in 11 of 21 (52%) orbits 3 months after surgery. The piezosurgical device is a useful tool for orbital decompression surgery in TAO. By cutting bone selectively, it is precise and reduces the invasiveness of surgery. Nevertheless, no improvement in outcome or reduction in morbidity over conventional techniques has been shown so far. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

The multifacet graphically contracted function method. II. A general procedure for the parameterization of orthogonal matrices and its application to arc factors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shepard, Ron; Brozell, Scott R.; Gidofalvi, Gergely

2014-08-14

Practical algorithms are presented for the parameterization of orthogonal matrices Q ∈ R {sup m×n} in terms of the minimal number of essential parameters (φ). Both square n = m and rectangular n < m situations are examined. Two separate kinds of parameterizations are considered, one in which the individual columns of Q are distinct, and the other in which only Span(Q) is significant. The latter is relevant to chemical applications such as the representation of the arc factors in the multifacet graphically contracted function method and the representation of orbital coefficients in SCF and DFT methods. The parameterizations aremore » represented formally using products of elementary Householder reflector matrices. Standard mathematical libraries, such as LAPACK, may be used to perform the basic low-level factorization, reduction, and other algebraic operations. Some care must be taken with the choice of phase factors in order to ensure stability and continuity. The transformation of gradient arrays between the Q and (φ) parameterizations is also considered. Operation counts for all factorizations and transformations are determined. Numerical results are presented which demonstrate the robustness, stability, and accuracy of these algorithms.« less

Association of Clinical Response and Long-term Outcome Among Patients With Biopsied Orbital Pseudotumor Receiving Modern Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prabhu, Roshan S., E-mail: rprabhu@emory.edu; Kandula, Shravan; Liebman, Lang

2013-03-01

Purpose: To retrospectively evaluate institutional outcomes for patients treated with modern radiation therapy (RT) for biopsied orbital pseudotumor (OP). Methods and Materials: Twenty patients (26 affected orbits) with OP were treated with RT between January 2002 and December 2011. All patients underwent biopsy with histopathologic exclusion of other disease processes. Sixteen patients (80%) were treated with intensity modulated RT, 3 (15%) with opposed lateral beams, and 1 (5%) with electrons. Median RT dose was 27 Gy (range 25.2-30.6 Gy). Response to RT was evaluated at 4 months post-RT. Partial response (PR) was defined as improvement in orbital symptoms without anmore » increase in steroid dose. Complete response (CR) 1 and CR 2 were defined as complete resolution of orbital symptoms with reduction in steroid dose (CR 1) or complete tapering of steroids (CR 2). The median follow-up period was 18.6 months (range 4-81.6 months). Results: Seventeen patients (85%) demonstrated response to RT, with 7 (35%), 1 (5%), and 9 (45%) achieving a PR, CR 1, and CR 2, respectively. Of the 17 patients who had ≥PR at 4 months post-RT, 6 (35%) experienced recurrence of symptoms. Age (>46 years vs ≤46 years, P=.04) and clinical response to RT (CR 2 vs CR 1/PR, P=.05) were significantly associated with pseudotumor recurrence. Long-term complications were seen in 7 patients (35%), including 4 with cataract formation, 1 with chronic dry eye, 1 with enophthalmos, and 1 with keratopathy. Conclusions: RT is an effective treatment for improving symptoms and tapering steroids in patients with a biopsy supported diagnosis of OP. Older age and complete response to RT were associated with a significantly reduced probability of symptom recurrence. The observed late complications may be related to RT, chronic use of steroids/immunosuppressants, medical comorbidities, or combination of factors.« less

Reduced Inferior and Orbital Frontal Thickness in Adolescent Bulimia Nervosa Persists Over Two-Year Follow-Up.

PubMed

Cyr, Marilyn; Kopala-Sibley, Daniel C; Lee, Seonjoo; Chen, Chen; Stefan, Mihaela; Fontaine, Martine; Terranova, Kate; Berner, Laura A; Marsh, Rachel

2017-10-01

Cross-sectional data suggest functional and anatomical disturbances in inferior and orbital frontal regions in bulimia nervosa (BN). Using longitudinal data, we investigated whether reduced cortical thickness (CT) in these regions arises early and persists over adolescence in BN, independent of symptom remission, and whether CT reductions are markers of BN symptoms. A total of 33 adolescent females with BN symptoms (BN or other specified feeding or eating disorder) and 28 healthy adolescents participated in this study. Anatomical magnetic resonance imaging and clinical data were acquired at 3 time points within 2-year intervals over adolescence, with 31% average attrition between assessments. Using a region-of-interest approach, we assessed group differences in CT at baseline and over time, and tested whether between- and within-subject variations in CT were associated with the frequency of BN symptoms. Reduced CT in the right inferior frontal gyrus persisted over adolescence in BN compared to healthy adolescents, even in those who achieved full or partial remission. Within the BN group, between-subject variations in CT in the inferior and orbital frontal regions were inversely associated with specific BN symptoms, suggesting, on average over time, greater CT reductions in individuals with more frequent BN symptoms. Reduced CT in inferior frontal regions may contribute to illness persistence into adulthood. Reductions in the thickness of the inferior and orbital frontal regions may be markers of specific BN symptoms. Because our sample size precluded correcting for multiple comparisons, these findings should be replicated in a larger sample. Future study of functional changes in associated fronto-striatal circuits could identify potential circuit-based intervention targets. Copyright © 2017 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

New orbit recalculations of comet C/1890 F1 Brooks and its dynamical evolution

NASA Astrophysics Data System (ADS)

Królikowska, Małgorzata; Dybczyński, Piotr A.

2016-08-01

C/1890 F1 Brooks belongs to a group of 19 comets used by Jan Oort to support his famous hypothesis on the existence of a spherical cloud containing hundreds of billions of comets with orbits of semi-major axes between 50 000 and 150 000 au. Comet Brooks stands out from this group because of a long series of astrometric observations as well as a nearly 2-yr-long observational arc. Rich observational material makes this comet an ideal target for testing the rationality of an effort to recalculate astrometric positions on the basis of original (comet-star) measurements using modern star catalogues. This paper presents the results of such a new analysis based on two different methods: (I) automatic re-reduction based on cometary positions and the (comet-star) measurements and (II) partially automatic re-reduction based on the contemporary data for the reference stars originally used. We show that both methods offer a significant reduction in the uncertainty of orbital elements. Based on the most preferred orbital solution, the dynamical evolution of comet Brooks during three consecutive perihelion passages is discussed. We conclude that C/1890 F1 is a dynamically old comet that passed the Sun at a distance below 5 au during its previous perihelion passage. Furthermore, its next perihelion passage will be a little closer than during the 1890-1892 apparition. C/1890 F1 is interesting also because it suffered extremely small planetary perturbations when it travelled through the planetary zone. Therefore, in the next passage through perihelion, it will once again be a comet from the Oort spike.

Radial orbit error reduction and sea surface topography determination using satellite altimetry

NASA Technical Reports Server (NTRS)

Engelis, Theodossios

1987-01-01

A method is presented in satellite altimetry that attempts to simultaneously determine the geoid and sea surface topography with minimum wavelengths of about 500 km and to reduce the radial orbit error caused by geopotential errors. The modeling of the radial orbit error is made using the linearized Lagrangian perturbation theory. Secular and second order effects are also included. After a rather extensive validation of the linearized equations, alternative expressions of the radial orbit error are derived. Numerical estimates for the radial orbit error and geoid undulation error are computed using the differences of two geopotential models as potential coefficient errors, for a SEASAT orbit. To provide statistical estimates of the radial distances and the geoid, a covariance propagation is made based on the full geopotential covariance. Accuracy estimates for the SEASAT orbits are given which agree quite well with already published results. Observation equations are develped using sea surface heights and crossover discrepancies as observables. A minimum variance solution with prior information provides estimates of parameters representing the sea surface topography and corrections to the gravity field that is used for the orbit generation. The simulation results show that the method can be used to effectively reduce the radial orbit error and recover the sea surface topography.

Mars sample return mission architectures utilizing low thrust propulsion

NASA Astrophysics Data System (ADS)

Derz, Uwe; Seboldt, Wolfgang

2012-08-01

The Mars sample return mission is a flagship mission within ESA's Aurora program and envisioned to take place in the timeframe of 2020-2025. Previous studies developed a mission architecture consisting of two elements, an orbiter and a lander, each utilizing chemical propulsion and a heavy launcher like Ariane 5 ECA. The lander transports an ascent vehicle to the surface of Mars. The orbiter performs a separate impulsive transfer to Mars, conducts a rendezvous in Mars orbit with the sample container, delivered by the ascent vehicle, and returns the samples back to Earth in a small Earth entry capsule. Because the launch of the heavy orbiter by Ariane 5 ECA makes an Earth swing by mandatory for the trans-Mars injection, its total mission time amounts to about 1460 days. The present study takes a fresh look at the subject and conducts a more general mission and system analysis of the space transportation elements including electric propulsion for the transfer. Therefore, detailed spacecraft models for orbiters, landers and ascent vehicles are developed. Based on that, trajectory calculations and optimizations of interplanetary transfers, Mars entries, descents and landings as well as Mars ascents are carried out. The results of the system analysis identified electric propulsion for the orbiter as most beneficial in terms of launch mass, leading to a reduction of launch vehicle requirements and enabling a launch by a Soyuz-Fregat into GTO. Such a sample return mission could be conducted within 1150-1250 days. Concerning the lander, a separate launch in combination with electric propulsion leads to a significant reduction of launch vehicle requirements, but also requires a large number of engines and correspondingly a large power system. Therefore, a lander performing a separate chemical transfer could possibly be more advantageous. Alternatively, a second possible mission architecture has been developed, requiring only one heavy launch vehicle (e.g., Proton). In that case the lander is transported piggyback by the electrically propelled orbiter.

An assessment of gravity model improvements using TOPEX/Poseidon TDRSS observations

NASA Technical Reports Server (NTRS)

Putney, B. H.; Teles, J.; Eddy, W. F.; Klosko, S. M.

1992-01-01

The contribution of TOPEX/Poseidon (T/P) TDRSS data to geopotential model recovery is assessed. Simulated TDRSS one-way and Bilateration Ranging Transponder System (BRTS) observations have been generated and orbitally reduced to form normal equations for geopotential parameters. These normals have been combined with those of the latest prelaunch T/P gravity model solution using data from over 30 satellites. A study of the resulting solution error covariance shows that TDRSS can make important contributions to geopotential recovery, especially for improving T/P specific effects like those arising from orbital resonance. It is argued that future effort is desirable both to establish TDRSS orbit determination limits in a reference frame compatible with that used for the precise laser/DORIS orbits, and the reduction of these TDRSS data for geopotential recovery.

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

DOE PAGES

Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; ...

2014-10-08

Here, the hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We concludemore » that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring.« less

Role of pendant proton relays and proton-coupled electron transfer on the hydrogen evolution reaction by nickel hangman porphyrins

PubMed Central

Bediako, D. Kwabena; Solis, Brian H.; Dogutan, Dilek K.; Roubelakis, Manolis M.; Maher, Andrew G.; Lee, Chang Hoon; Chambers, Matthew B.; Hammes-Schiffer, Sharon; Nocera, Daniel G.

2014-01-01

The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the hydrogen evolution reaction (HER). We now show improved HER activity of Ni compared with Co hangman porphyrins. Cyclic voltammogram data and simulations, together with computational studies using density functional theory, implicate a shift in electrokinetic zone between Co and Ni hangman porphyrins due to a change in the PCET mechanism. Unlike the Co hangman porphyrin, the Ni hangman porphyrin does not require reduction to the formally metal(0) species before protonation by weak acids in acetonitrile. We conclude that protonation likely occurs at the Ni(I) state followed by reduction, in a stepwise proton transfer–electron transfer pathway. Spectroelectrochemical and computational studies reveal that upon reduction of the Ni(II) compound, the first electron is transferred to a metal-based orbital, whereas the second electron is transferred to a molecular orbital on the porphyrin ring. PMID:25298534

Structure factors for tunneling ionization rates of molecules: General Hartree-Fock-based integral representation

NASA Astrophysics Data System (ADS)

Madsen, Lars Bojer; Jensen, Frank; Dnestryan, Andrey I.; Tolstikhin, Oleg I.

2017-07-01

In the leading-order approximation of the weak-field asymptotic theory (WFAT), the dependence of the tunneling ionization rate of a molecule in an electric field on its orientation with respect to the field is determined by the structure factor of the ionizing molecular orbital. The WFAT yields an expression for the structure factor in terms of a local property of the orbital in the asymptotic region. However, in general quantum chemistry approaches molecular orbitals are expanded in a Gaussian basis which does not reproduce their asymptotic behavior correctly. This hinders the application of the WFAT to polyatomic molecules, which are attracting increasing interest in strong-field physics. Recently, an integral-equation approach to the WFAT for tunneling ionization of one electron from an arbitrary potential has been developed. The structure factor is expressed in an integral form as a matrix element involving the ionizing orbital. The integral is not sensitive to the asymptotic behavior of the orbital, which resolves the difficulty mentioned above. Here, we extend the integral representation for the structure factor to many-electron systems treated within the Hartree-Fock method and show how it can be implemented on the basis of standard quantum chemistry software packages. We validate the methodology by considering noble-gas atoms and the CO molecule, for which accurate structure factors exist in the literature. We also present benchmark results for CO2 and for NH3 in the pyramidal and planar geometries.

The impact of suction drainage on orbital compartment syndrome after craniofacial surgery.

PubMed

Fenzl, Carlton R; Golio, Dominick

2014-07-01

Postoperative orbital compartment syndrome is a potentially blinding complication of surgery in the orbital region. We describe the technique of orbital drain placement as a method of preventing vision loss resulting from orbital compartment syndrome. We present a retrospective case series of 29 patients who underwent orbital fracture, facial fracture, and orbital implant removal from 7/4/2008 to 5/3/2013 by the same craniofacial surgeon. An orbital drain was placed in each patient. The drainage was recorded daily until drain removal. Criteria for removal included less than or equal to 5 mL of drainage in 24 hours. Of the 29 patients included in this study, 21 were men and 8 were women. Ages ranged from 17 to 67 years. The postoperative drainage ranged from less than 1 mL to 71 mL of serosanguinous fluid. All drains were removed between the first and sixth postoperative days. No postoperative visual loss, infections, or additional antibiotics were recorded with follow-up reaching as far as 40 months. Postoperative orbital compartment syndrome is a dangerous complication of surgery in the orbital region. Its rapid onset necessitates immediate intervention to prevent permanent vision loss. Morphologic changes to the optic nerve as well as reductions in electroretinogram a- and b-wave amplitudes have been demonstrated with as little as 7 mL of fluid accumulation. Intraoperative orbital drain placement should be considered in all patients undergoing surgery in the orbital region as a preventative measure.

Deployment and Intelligent Nanosatellite Operations Colorado Final Technical Report

DTIC Science & Technology

2006-09-28

environmental factors will cause disturbance torques during orbit around the Earth . These factors are solar radiation pressure from the sun , aerodynamic...software. The 3- axis sensing of the magnetometer allows a vector the B- field of the Earth to be sensed. Geopack 2003 then can be utilized with the orbit ...gradient torque can be represented as the following: g, ; 3wo21 Eq. 2-11 where ow is the angular velocity of the spacecraft as it orbits the earth . DINO’s

Orbital manifestations in patients with acquired immunodeficiency syndrome.

PubMed

Sodhi, Punita Kumari

2014-01-01

The orbital manifestations of acquired immunodeficiency syndrome(AIDS) are uncommon. To provide a review of orbital manifestations of AIDS, the predisposing factors, investigations, treatment and outcome. Meticulous and systematic literature search of Pubmed to identify manuscripts describing orbital manifestations of AIDS was done and the articles were reviewed.The keywords used in the search were “orbit and AIDS”, “HIV positive and orbit”,“orbit manifestations in AIDS”, “orbital disease and AIDS” and “orbital infections and AIDS”. The orbital involvement in AIDS may present with opportunistic infections from organisms like fungi, viruses, bacteria and protozoa or with malignancies like Kaposi’s sarcoma, squamous cell carcinoma, smooth muscle cell tumors and lymphoma.The predisposing factors for orbital involvement in AIDS are low CD4+ cell count and the immunosuppressive states like diabetes, diabetic ketoacidosis, intravenous drug abuse and neutropenia. A patient may present with fever, headache, nausea, vomiting,decreased vision, ocular pain, and, in cases of mass formation, there is periorbital swelling, axial proptosis, globe displacement and swollen optic disc. Radiologically,mass formation, orbital bony destruction, and spread of disease to contiguous structures including the central nervous system may be seen. The medical management includes therapy for infection and HIV-1 protease inhibitors (highly active antiretroviral therapy)to suppress HIV-1 replication. For tumors, radical surgery including debulking followed by postoperative radiotherapy is generally needed. Orbital involvements with AIDS in any form, infective or malignancy, causes significant morbidity and mortality and should be diagnosed and managed as early as possible.

The moduli space of vacua of $$ \\mathcal{N}=2 $$ class $$ \\mathcal{S} $$ theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Dan; Yonekura, Kazuya

We develop a systematic method to describe the moduli space of vacua of four dimensional N=2 class S theories including Coulomb branch, Higgs branch and mixed branches. In particular, we determine the Higgs and mixed branch roots, and the dimensions of the Coulomb and Higgs components of mixed branches. They are derived by using generalized Hitchin’s equations obtained from twisted compactification of 5d maximal Super-Yang-Mills, with local degrees of freedom at punctures given by (nilpotent) orbits. The crucial thing is the holomorphic factorization of the Seiberg-Witten curve and reduction of singularity at punctures. We illustrate our method by many examplesmore » including N=2 SQCD, T N theory and Argyres-Douglas theories.« less

Revision to Planetary Protection Policy for Mars Missions

NASA Technical Reports Server (NTRS)

DeVincenzi, D. L.; Stabekis, P.; Barengoltz, J.; Morrison, David (Technical Monitor)

1994-01-01

Under existing COSPAR policy adopted in 1984, missions to Mars (landers, probes, and some orbiters) are designated as Category IV missions. As such, the procedures for implementing planetary protection requirements could include trajectory biasing, cleanrooms, bioload reduction, sterilization of hardware, and bioshields, i. e. requirements could be similar to Viking. However, in 1992, a U. S. National Academy of Sciences study recommended that controls on forward contamination of Mars be tied to specific mission objectives. The report recommended that Mars landers with life detection instruments be subject to at least Viking-level sterilization procedures for bioload reduction, while spacecraft (including orbiters) without life detection instruments be subject to at least Viking-level pre sterilization procedures for bioload reduction but need not be sterilized. In light of this, it is proposed that the current policy's Category IV missions and their planetary protection requirements be divided into two subcategories as follows: Category IV A, for missions comprising landers and probes without life detection experiments and some orbiters, which will meet a specified bioburden limit for exposed surfaces; Category IV B, for landers and probes with life detection experiments, which will require complete system sterilization. For Category IV A missions, bioburden specifications will be proposed and implementing procedures discussed. A resolution will be proposed to modify the existing COSPAR policy to reflect these changes. Similar specifications, procedures, and resolution for Category IV B missions will be the subject of a later study.

Improved definition of crustal magnetic anomalies for MAGSAT data

NASA Technical Reports Server (NTRS)

Brown, R. D.; Frawley, J. F.; Davis, W. M.; Ray, R. D.; Didwall, E.; Regan, R. D. (Principal Investigator)

1982-01-01

The routine correction of MAGSAT vector magnetometer data for external field effects such as the ring current and the daily variation by filtering long wavelength harmonics from the data is described. Separation of fields due to low altitude sources from those caused by high altitude sources is affected by means of dual harmonic expansions in the solution of Dirichlet's problem. This regression/harmonic filter procedure is applied on an orbit by orbit basis, and initial tests on MAGSAT data from orbit 1176 show reduction in external field residuals by 24.33 nT RMS in the horizontal component, and 10.95 nT RMS in the radial component.

Relativistic corrections to the form factors of Bc into P-wave orbitally excited charmonium

NASA Astrophysics Data System (ADS)

Zhu, Ruilin

2018-06-01

We investigated the form factors of the Bc meson into P-wave orbitally excited charmonium using the nonrelativistic QCD effective theory. Through the analytic computation, the next-to-leading order relativistic corrections to the form factors were obtained, and the asymptotic expressions were studied in the infinite bottom quark mass limit. Employing the general form factors, we discussed the exclusive decays of the Bc meson into P-wave orbitally excited charmonium and a light meson. We found that the relativistic corrections lead to a large correction for the form factors, which makes the branching ratios of the decay channels B (Bc ± →χcJ (hc) +π± (K±)) larger. These results are useful for the phenomenological analysis of the Bc meson decays into P-wave charmonium, which shall be tested in the LHCb experiments.

A Real-Time Robust Method to Detect BeiDou GEO/IGSO Orbital Maneuvers

PubMed Central

Huang, Guanwen; Qin, Zhiwei; Zhang, Qin; Wang, Le; Yan, Xingyuan; Fan, Lihong; Wang, Xiaolei

2017-01-01

The frequent maneuvering of BeiDou Geostationary Orbit (GEO) and Inclined Geosynchronous Orbit (IGSO) satellites affects the availability of real-time orbit, and decreases the accuracy and performance of positioning, navigation and time (PNT) services. BeiDou satellite maneuver information cannot be obtained by common users. BeiDou broadcast ephemeris is the only indicator of the health status of satellites, which are broadcast on an hourly basis, easily leading to ineffective observations. Sometimes, identification errors of satellite abnormity also appear in the broadcast ephemeris. This study presents a real-time robust detection method for a satellite orbital maneuver with high frequency and high reliability. By using the broadcast ephemeris and pseudo-range observations, the time discrimination factor and the satellite identification factor were defined and used for the real-time detection of start time and the pseudo-random noise code (PRN) of satellites was used for orbital maneuvers. Data from a Multi-GNSS Experiment (MGEX) was collected and analyzed. The results show that the start time and the PRN of the satellite orbital maneuver could be detected accurately in real time. In addition, abnormal start times and satellite abnormities caused by non-maneuver factors also could be detected using the proposed method. The new method not only improves the utilization of observations for users with the data effective for about 92 min, but also promotes the reliability of real-time PNT services. PMID:29186058

A Real-Time Robust Method to Detect BeiDou GEO/IGSO Orbital Maneuvers.

PubMed

Huang, Guanwen; Qin, Zhiwei; Zhang, Qin; Wang, Le; Yan, Xingyuan; Fan, Lihong; Wang, Xiaolei

2017-11-29

The frequent maneuvering of BeiDou Geostationary Orbit (GEO) and Inclined Geosynchronous Orbit (IGSO) satellites affects the availability of real-time orbit, and decreases the accuracy and performance of positioning, navigation and time (PNT) services. BeiDou satellite maneuver information cannot be obtained by common users. BeiDou broadcast ephemeris is the only indicator of the health status of satellites, which are broadcast on an hourly basis, easily leading to ineffective observations. Sometimes, identification errors of satellite abnormity also appear in the broadcast ephemeris. This study presents a real-time robust detection method for a satellite orbital maneuver with high frequency and high reliability. By using the broadcast ephemeris and pseudo-range observations, the time discrimination factor and the satellite identification factor were defined and used for the real-time detection of start time and the pseudo-random noise code (PRN) of satellites was used for orbital maneuvers. Data from a Multi-GNSS Experiment (MGEX) was collected and analyzed. The results show that the start time and the PRN of the satellite orbital maneuver could be detected accurately in real time. In addition, abnormal start times and satellite abnormities caused by non-maneuver factors also could be detected using the proposed method. The new method not only improves the utilization of observations for users with the data effective for about 92 min, but also promotes the reliability of real-time PNT services.

Coupled s-p-d Exchange in Facet-Controlled Pd 3 Pb Tripods Enhances Oxygen Reduction Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bu, Lingzheng; Shao, Qi; Pi, Yecan

Efficient oxygen reduction reaction (ORR) catalysts are the key in developing high-performance fuel cells. Palladium (Pd) is a promising catalyst system for ORR with its potential to replace platinum (Pt), however it usually exhibits lower activity than Pt. Herein, we report a class of ordered Pd3Pb tripods (TPs) with dominated {110} facets that show extremely high ORR performance in alkaline medium. Totally different from the well-known knowledge that excellent ORR activity of Pt catalyst is caused by its partially-filled d-orbital, our first principle calculations suggest that the strong charge exchange between Pd-4d and Pb-(sp) orbitals on Pd3Pb TPs {110} facetmore » results in the Pd-Pb local bonding unit with the orbital configuration similar to Pt. Consequently, the Pd3Pb TPs exhibit much higher ORR activities than commercial Pt/C and commercial Pd/C. The Pd3Pb TPs are rather endurable and sustain over 20,000 potential cycles with negligible structural and compositional changes.« less

Coupled s-p-d Exchange in Facet-Controlled Pd 3 Pb Tripods Enhances Oxygen Reduction Catalysis

DOE PAGES

Bu, Lingzheng; Shao, Qi; Pi, Yecan; ...

2018-02-01

Efficient oxygen reduction reaction (ORR) catalysts are the key in developing high-performance fuel cells. Palladium (Pd) is a promising catalyst system for ORR with its potential to replace platinum (Pt), however it usually exhibits lower activity than Pt. Herein, we report a class of ordered Pd3Pb tripods (TPs) with dominated {110} facets that show extremely high ORR performance in alkaline medium. Totally different from the well-known knowledge that excellent ORR activity of Pt catalyst is caused by its partially-filled d-orbital, our first principle calculations suggest that the strong charge exchange between Pd-4d and Pb-(sp) orbitals on Pd3Pb TPs {110} facetmore » results in the Pd-Pb local bonding unit with the orbital configuration similar to Pt. Consequently, the Pd3Pb TPs exhibit much higher ORR activities than commercial Pt/C and commercial Pd/C. The Pd3Pb TPs are rather endurable and sustain over 20,000 potential cycles with negligible structural and compositional changes.« less

Pathogenesis of ophthalmopathy in autoimmune thyroid disease.

PubMed

Heufelder, A E

2000-01-01

What causes GO is still a mystery, but the disease process results from a complex interplay of genetic and environmental factors. Genes such as those for HLA genes may determine a patient's susceptibility to the disease and its severity, but environmental factors, often unknown, may determine its course. Once established, the chronic inflammatory process within the orbital tissues appears to take on a momentum of its own. Given our current state of knowledge, the following working scheme for the pathogenesis of GO can be proposed (Fig. 1): On the background of a permissive immunogenetic milieu, circulating T cells in patients with GD, directed against certain antigens on thyroid follicular cells, recognize antigenic epitopes that are shared by tissues contained in the orbital space. Of the cell types residing in these tissues, preadipocytes and fibroblasts, most likely act as target and effector cells of the orbital immune process, respectively. This includes preadipocyte fibroblasts present in the perimysium of extraocular muscles, which do not appear to be immunologically different from those located in the orbital connective tissue. Orbital preadipocyte fibroblasts may be stimulated by unknown circulating or locally produced factors to differentiate into mature adipocytes that express increased levels of TSHr. How autoreactive T cells escape deletion and control by the immune system and come to be directed against a self-antigen presented by cells residing in the thyroid gland and extrathyroidal locations, is still unknown. Proliferation and expansion of autoreactive T cell clones may be due to mimicry of a host antigen by a microorganism, but this remains speculative. T cell recruitment into the orbital tissues is facilitated by certain chemokines and cytokines, which help to attract T cells by stimulating the expression of certain adhesion molecules (e.g., ICAM-1, VCAM-1, CD44) in vascular endothelium and connective tissue cells. These adhesion receptors are known to also play an important costimulatory role by activating T cells and facilitating antigen recognition, which amplifies the cellular immune process. Analysis of variable region genes of T cell antigen receptors in orbital T cells of patients with active GO has revealed their restricted TcR V gene usage, suggesting that antigen-driven selection and/or expansion of specific T cells may occur early in the evolution of GO. T cells and macrophages populating the orbital space are known to synthesize and release a [figure: see text] number of cytokines (most likely a Th1-type spectrum) into the surrounding tissue. Cytokines, oxygen free radicals and fibrogenic growth factors, released both from infiltrating inflammatory and residential cells, act upon orbital preadipocytes in a paracrine and autocrine manner to stimulate adipogenesis, fibroblast proliferation, glycosaminoglycan synthesis, and the expression of immunomodulatory molecules. Smoking, a well-known aggravating factor in GO, may aggravate tissue hypoxia and exert important immunomodulatory effects. The long held hypothesis of a thyroid cross-reactive antigen within the orbital tissues has recently gained significant support by an animal model of GO, and by in vitro and ex vivo studies. If confirmed in immunological studies, these data may well explain the localized infiltration of the orbital tissues by autoreactive lymphocytes that share intriguing molecular features with intrathyroidal lymphocytes. Local release of particular cytokines, TSHr-directed antibodies, or other factors might further enhance adipogenesis, glycosaminoglycan synthesis and expression of immunomodulatory proteins within the orbit. Other factors, including inflammatory cytokines, might act as counterbalancing inhibitors of these effects. However, if the net effect of these changes is to increase the volume of the fatty connective tissues within the orbit, then proptosis, extraocular muscle dysfunction, and periorbital congestion will ensue. Whether this hypothetical sequence of events will finally explain the involvement of the orbit in GD is unknown. Future studies will be aimed at identifying factors that might modulate adipogenesis in orbital cells and clarifying the link between adipogenesis and TSHr expression in the orbit. Taken together, a number of important details in the complex pathogenesis of GO have been resolved in recent years, but many challenges are still ahead. Elucidation of the primary antigen and how it is recognized by the immune system will be key issues.

Lunar lander stage requirements based on the Civil Needs Data Base

NASA Technical Reports Server (NTRS)

Mulqueen, John A.

1992-01-01

This paper examines the lunar lander stages that will be necessary for the future exploration and development of the Moon. Lunar lander stage sizing is discussed based on the projected lunar payloads listed in the Civil Needs Data Base. Factors that will influence the lander stage design are identified and discussed. Some of these factors are (1) lunar orbiting and lunar surface lander bases; (2) implications of direct landing trajectories and landing from a parking orbit; (3) implications of landing site and parking orbit; (4) implications of landing site and parking orbit selection; (5) the use of expendable and reusable lander stages; and (6) the descent/ascent trajectories. Data relating the lunar lander stage design requirements to each of the above factors and others are presented in parametric form. These data will provide useful design data that will be applicable to future mission model modifications and design studies.

Ecomorphology of orbit orientation and the adaptive significance of binocular vision in primates and other mammals.

PubMed

Heesy, Christopher P

2008-01-01

Primates are characterized by forward-facing, or convergent, orbits and associated binocular field overlap. Hypotheses explaining the adaptive significance of these traits often relate to ecological factors, such as arboreality, nocturnal visual predation, or saltatory locomotion in a complex nocturnal, arboreal environment. This study re-examines the ecological factors that are associated with high orbit convergence in mammals. Orbit orientation data were collected for 321 extant taxa from sixteen orders of metatherian (marsupial) and eutherian mammals. These taxa were coded for activity pattern, degree of faunivory, and substrate preference. Results demonstrate that nocturnal and cathemeral mammals have significantly more convergent orbits than diurnal taxa, both within and across orders. Faunivorous eutherians (both nocturnal and diurnal) have higher mean orbit convergence than opportunistically foraging or non-faunivorous taxa. However, substrate preference is not associated with higher orbit convergence and, by extension, greater binocular visual field overlap. These results are consistent with the hypothesis that mammalian predators evolved higher orbit convergence, binocular vision, and stereopsis to counter camouflage in prey inhabiting a nocturnal environment. Strepsirhine primates have a range of orbit convergence values similar to nocturnal or cathemeral predatory non-primate mammals. These data are entirely consistent with the nocturnal visual predation hypothesis of primate origins. (c) 2007 S. Karger AG, Basel.

Regional climate and vegetation response to orbital forcing within the mid-Pliocene Warm Period: A study using HadCM3

NASA Astrophysics Data System (ADS)

Prescott, C. L.; Dolan, A. M.; Haywood, A. M.; Hunter, S. J.; Tindall, J. C.

2018-02-01

Regional climate and environmental variability in response to orbital forcing during interglacial events within the mid-Piacenzian (Pliocene) Warm Period (mPWP; 3.264-3.025 Ma) has been rarely studied using climate and vegetation models. Here we use climate and vegetation model simulations to predict changes in regional vegetation patterns in response to orbital forcing for four different interglacial events within the mPWP (Marine Isotope Stages (MIS) G17, K1, KM3 and KM5c). The efficacy of model-predicted changes in regional vegetation is assessed by reference to selected high temporal resolution palaeobotanical studies that are theoretically capable of discerning vegetation patterns for the selected interglacial stages. Annual mean surface air temperatures for the studied interglacials are between 0.4 °C to 0.7 °C higher than a comparable Pliocene experiment using modern orbital parameters. Increased spring/summer and reduced autumn/winter insolation in the Northern Hemisphere during MIS G17, K1 and KM3 enhances seasonality in surface air temperature. The two most robust and notable regional responses to this in vegetation cover occur in North America and continental Eurasia, where forests are replaced by more open-types of vegetation (grasslands and shrubland). In these regions our model results appear to be inconsistent with local palaeobotanical data. The orbitally driven changes in seasonal temperature and precipitation lead to a 30% annual reduction in available deep soil moisture (2.0 m from surface), a critical parameter for forest growth, and subsequent reduction in the geographical coverage of forest-type vegetation; a phenomenon not seen in comparable simulations of Pliocene climate and vegetation run with a modern orbital configuration. Our results demonstrate the importance of examining model performance under a range of realistic orbital forcing scenarios within any defined time interval (e.g. mPWP). Additional orbitally resolved records of regional vegetation are needed to further examine the validity of model-predicted regional climate and vegetation responses in greater detail.

[Multi-wall orbital decompression for disfiguring proptosis in patients with mild or moderate thyroid eye disease].

PubMed

Wang, Y; Yang, N; Li, Y Y; Xiao, L H

2017-02-11

Objective: To evaluate the efficacy of orbital decompression by transconjunctival medial and inferior wall combined transpalpebral lateral wall for disfiguring proptosis with mild or moderate thyroid eye disease (TED). Methods: It is a retrospective case series study. The clinical data of 18 TED cases (28 orbits) between Dec 2013 and Dec 2015 at the Institute of Orbital Diseases of the General Hospital of the Armed Police were reviewed. All the patients underwent mulit-wall orbital decompression to relieve remarkable proptosis, widen eyelid fissure, and swollen eyelid. 1. Hertel value was 14-23 mm or over 2-7 mm than contralateral eye; 2.Orbitalpathy has been inactive with normal thyroid function for at least 6 months; 3.Orbital pressure is normal or (+). Clinical outcomes were recorded including best-corrected visual acuity, exophthalmometry, margin-to-central distance of upper and lower lids, diplopia, and CT scans before and 3 months after surgery. Results: The mean protosis of pre-and postoperation were (19.2±2.3) mm and (14.7±1.4) mm with mean reduction was (4.6±1.7) mm ( t= 14.08, P< 0.01). Margin-to-central distance of the upperlid of pre- and postoperation were (5.1±1.2) mm and (4.9±1.3) mm with mean reduction was (0.2±0.5) mm ( t= 1.73, P= 0.095). Margin-to-central distance of the lowerlid of pre-and postoperation were (5.9±0.9) mm and 4.3±0.7 mm with mean reduction was (1.6±0.8) mm ( t= 10.09, P< 0.01). The difference of bilateral exophthalmos after surgery is 0-2.5 mm (media n= 1 mm). None of the patients showed new-onset diplopia at primary gaze and two patient showed surrounding gaze diplopia postoperatively. Two patients with diplopia relieved after surgery ( Z= 743.00, P= 0.458). Conclusions: Transconjunctival and transpalpebral medial, inferior, and lateral walls decompression with a hidden incision was a controllable, safe, effective technique with minimal complications in relieving not only mild, moderate proptosis, but also retraction of lowerlid, and swollen eyelids. (Chin J Ophthalmol, 2017, 53: 128-135) .

An Optimized Method to Detect BDS Satellites' Orbit Maneuvering and Anomalies in Real-Time.

PubMed

Huang, Guanwen; Qin, Zhiwei; Zhang, Qin; Wang, Le; Yan, Xingyuan; Wang, Xiaolei

2018-02-28

The orbital maneuvers of Global Navigation Satellite System (GNSS) Constellations will decrease the performance and accuracy of positioning, navigation, and timing (PNT). Because satellites in the Chinese BeiDou Navigation Satellite System (BDS) are in Geostationary Orbit (GEO) and Inclined Geosynchronous Orbit (IGSO), maneuvers occur more frequently. Also, the precise start moment of the BDS satellites' orbit maneuvering cannot be obtained by common users. This paper presented an improved real-time detecting method for BDS satellites' orbit maneuvering and anomalies with higher timeliness and higher accuracy. The main contributions to this improvement are as follows: (1) instead of the previous two-steps method, a new one-step method with higher accuracy is proposed to determine the start moment and the pseudo random noise code (PRN) of the satellite orbit maneuvering in that time; (2) BDS Medium Earth Orbit (MEO) orbital maneuvers are firstly detected according to the proposed selection strategy for the stations; and (3) the classified non-maneuvering anomalies are detected by a new median robust method using the weak anomaly detection factor and the strong anomaly detection factor. The data from the Multi-GNSS Experiment (MGEX) in 2017 was used for experimental analysis. The experimental results and analysis showed that the start moment of orbital maneuvers and the period of non-maneuver anomalies can be determined more accurately in real-time. When orbital maneuvers and anomalies occur, the proposed method improved the data utilization for 91 and 95 min in 2017.

An Optimized Method to Detect BDS Satellites’ Orbit Maneuvering and Anomalies in Real-Time

PubMed Central

Huang, Guanwen; Qin, Zhiwei; Zhang, Qin; Wang, Le; Yan, Xingyuan; Wang, Xiaolei

2018-01-01

The orbital maneuvers of Global Navigation Satellite System (GNSS) Constellations will decrease the performance and accuracy of positioning, navigation, and timing (PNT). Because satellites in the Chinese BeiDou Navigation Satellite System (BDS) are in Geostationary Orbit (GEO) and Inclined Geosynchronous Orbit (IGSO), maneuvers occur more frequently. Also, the precise start moment of the BDS satellites’ orbit maneuvering cannot be obtained by common users. This paper presented an improved real-time detecting method for BDS satellites’ orbit maneuvering and anomalies with higher timeliness and higher accuracy. The main contributions to this improvement are as follows: (1) instead of the previous two-steps method, a new one-step method with higher accuracy is proposed to determine the start moment and the pseudo random noise code (PRN) of the satellite orbit maneuvering in that time; (2) BDS Medium Earth Orbit (MEO) orbital maneuvers are firstly detected according to the proposed selection strategy for the stations; and (3) the classified non-maneuvering anomalies are detected by a new median robust method using the weak anomaly detection factor and the strong anomaly detection factor. The data from the Multi-GNSS Experiment (MGEX) in 2017 was used for experimental analysis. The experimental results and analysis showed that the start moment of orbital maneuvers and the period of non-maneuver anomalies can be determined more accurately in real-time. When orbital maneuvers and anomalies occur, the proposed method improved the data utilization for 91 and 95 min in 2017. PMID:29495638

Degradation of the Adhesive Properties of MD-944 Diode Tape by Simulated Low Earth Orbit Environmental Factors

NASA Technical Reports Server (NTRS)

Albyn, K.; Finckenor, M.

2006-01-01

The International Space Station (ISS) solar arrays utilize MD-944 diode tape with silicone pressure-sensitive adhesive to protect the underlying diodes and also provide a high-emittance surface. On-orbit, the silicone adhesive will be exposed and ultimately convert to a glass-like silicate due to atomic oxygen (AO). The current operational plan is to retract ISS solar array P6 and leave it stored under load for a long duration (6 mo or more). The exposed silicone adhesive must not cause the solar array to stick to itself or cause the solar array to fail during redeployment. The Environmental Effects Branch at Marshall Space Flight Center, under direction from the ISS Program Office Environments Team, performed simulated space environment exposures with 5-eV AO, near ultraviolet radiation and ionizing radiation. The exposed diode tape samples were put under preload and then the resulting blocking force was measured using a tensile test machine. Test results indicate that high-energy AO, ultraviolet radiation, and electron ionizing radiation exposure all reduce the blocking force for a silicone-to-silicone bond. AO exposure produces the most significant reduction in blocking force

Effects of Orbital Lifetime Reduction on the Long-Term Earth Satellite Population as Modeled by EVOLVE 4.0

NASA Technical Reports Server (NTRS)

Krisko, Paula H.; Opiela, John N.; Liou, Jer-Chyi; Anz-Meador, Phillip D.; Theall, Jeffrey R.

1999-01-01

The latest update of the NASA orbital debris environment model, EVOLVE 4.0, has been used to study the effect of various proposed debris mitigation measures, including the NASA 25-year guideline. EVOLVE 4.0, which includes updates of the NASA breakup, solar activity, and the orbit propagator models, a GEO analysis option, and non-fragmentation debris source models, allows for the statistical modeling and predicted growth of the particle population >1 mm in characteristic length in LEO and GEO orbits. The initial implementation of this &odel has been to study the sensitivity of the overall LEO debris environment to mitigation measures designed to limit the lifetime of intact objects in LEO orbits. The mitigation measures test matrix for this study included several commonly accepted testing schemes, i.e., the variance of the maximum LEO lifetime from 10 to 50 years, the date of the initial implementation of this policy, the shut off of all explosions at some specified date, and the inclusion of disposal orbits. All are timely studies in that all scenarios have been suggested by researchers and satellite operators as options for the removal of debris from LEO orbits.

Precision GPS ephemerides and baselines

NASA Technical Reports Server (NTRS)

1991-01-01

Based on the research, the area of precise ephemerides for GPS satellites, the following observations can be made pertaining to the status and future work needed regarding orbit accuracy. There are several aspects which need to be addressed in discussing determination of precise orbits, such as force models, kinematic models, measurement models, data reduction/estimation methods, etc. Although each one of these aspects was studied at CSR in research efforts, only points pertaining to the force modeling aspect are addressed.

Orbital synchronization capture of two binaries emitting gravitational waves

NASA Astrophysics Data System (ADS)

Seto, Naoki

2018-03-01

We study the possibility of orbital synchronization capture for a hierarchical quadrupole stellar system composed by two binaries emitting gravitational waves. Based on a simple model including the mass transfer for white dwarf binaries, we find that the capture might be realized for inter-binary distances less than their gravitational wavelength. We also discuss related intriguing phenomena such as a parasitic relation between the coupled white dwarf binaries and significant reductions of gravitational and electromagnetic radiations.

The Actual Mass of the Object Orbiting Epsilon Eridani

NASA Astrophysics Data System (ADS)

Gatewood, G.

2000-10-01

We have tested our 112 Multichannel Astrometric Photometer (MAP) (Gatewood 1987, AJ 94, 213) observations (beginning in 1988) of Epsilon Eridani against the orbital elements provided to us by W. Cochran (private communication). The reduction algorithm is detailed most recently by Gatewood, Han, and Black (2000 ApJ Letters, in press). The seven year period is clearly shown in a variance vs trial periods plot. Although it is near the limit of the current instrument, the astrometric orbital motion is apparent in the residuals to a standard derivation of the star's proper motion and parallax. The astrometric orbital parameters derived by forcing the spectroscopic elements are: semimajor axis = 1.51 +/- 0.44 mas, node of the orbit on the sky = 120 +/- 28 deg, inclination out of the plane of the sky = 46 +/- 17 deg, actual mass = 1.2 +/- 0.33 times that of Jupiter. Our study confirms this object (this is not a minimum mass) as the nearest extrasolar Jupiter mass companion to our solar system. In view of its large orbital eccentricity, however, its exact nature remains unclear.

Spacecraft flight simulation: A human factors investigation into the man-machine interface between an astronaut and a spacecraft performing docking maneuvers and other proximity operations

NASA Technical Reports Server (NTRS)

Brody, Adam R.

1988-01-01

The anticipated increase in rendezvous and docking activities in the various space programs in the Space Station era necessitates a renewed interest in manual docking procedures. Ten test subjects participated in computer simulated docking missions in which the influence of initial velocity was examined. All missions started from a resting position of 304.8 meters (1000 feet) along the space station's +V-bar axis. Test subjects controlled their vehicle with a translational hand controller and digital auto pilot which are both virtually identical to their space shuttle counterparts. While the 0.1 percent rule (range rate is equal to 0.1 percent of the range) used by space shuttle pilots is comfortably safe, it is revealed to be extremely inefficient in terms of time and not justifiable in terms of marginal safety. Time is worth money, not only because of training and launch costs, but because the sooner a pilot and spacecraft return from a mission, the sooner they can begin the next one. Inexperienced test subjects reduced the costs of simulated docking by close to a factor of 2 and achieved safe dockings in less than 4 percent of the time the baseline approach would entail. This reduction in time can be used to save lives in the event of an accident on orbit, and can tremendously reduce docking costs if fuel is produced from waste water on orbit.

Factorization and resummation: A new paradigm to improve gravitational wave amplitudes. II. The higher multipolar modes

NASA Astrophysics Data System (ADS)

Messina, Francesco; Maldarella, Alberto; Nagar, Alessandro

2018-04-01

The factorization and resummation approach of Nagar and Shah [Phys. Rev. D 94, 104017 (2016), 10.1103/PhysRevD.94.104017], designed to improve the strong-field behavior of the post-Newtonian (PN) residual waveform amplitudes fℓm's entering the effective-one-body, circularized, gravitational waveform for spinning coalescing binaries, is improved and generalized here to all multipoles up to ℓ=6 . For a test particle orbiting a Kerr black hole, each multipolar amplitude is truncated at relative 6 PN order, both for the orbital (nonspinning) and spin factors. By taking a certain Padé approximant (typically the P24 one) of the orbital factor in conjunction with the inverse Taylor (iResum) representation of the spin factor, it is possible to push the analytical/numerical agreement of the energy flux at the level of 5% at the last-stable orbit for a quasimaximally spinning black hole with dimensionless spin parameter +0.99 . When the procedure is generalized to comparable-mass binaries, each orbital factor is kept at relative 3+3 PN order; i.e., the globally 3 PN-accurate comparable-mass terms are hybridized with higher-PN test-particle terms up to 6 PN relative order in each mode. The same Padé resummation is used for continuity. By contrast, the spin factor is only kept at the highest comparable-mass PN order currently available. We illustrate that the consistency between different truncations in the spin content of the waveform amplitudes is more marked in the resummed case than when using the standard Taylor-expanded form of Pan et al. [Phys. Rev. D 83, 064003 (2011), 10.1103/PhysRevD.83.064003]. We finally introduce a method to consistently hybridize comparable-mass and test-particle information also in the presence of spin (including the spin of the particle), discussing it explicitly for the ℓ=m =2 spin-orbit and spin-square terms. The improved, factorized and resummed, multipolar waveform amplitudes presented here are expected to set a new standard for effective one body-based gravitational waveform models.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kikuchi, Akihiro; Higuchi, Arika; Ida, Shigeru, E-mail: kikuchi.a@geo.titech.ac.jp, E-mail: higuchia@geo.titech.ac.jp, E-mail: ida@elsi.jp

Recently, gas giant planets in nearly circular orbits with large semimajor axes (a ∼ 30-1000 AU) have been detected by direct imaging. We have investigated orbital evolution in a formation scenario for such planets, based on a core accretion model. (1) Icy cores accrete from planetesimals at ≲ 30 AU, (2) they are scattered outward by an emerging nearby gas giant to acquire highly eccentric orbits, and (3) their orbits are circularized through the accretion of disk gas in outer regions, where they spend most of their time. We analytically derived equations to describe the orbital circularization through gas accretion.more » Numerical integrations of these equations show that the eccentricity decreases by a factor of more than 5 while the planetary mass increases by a factor of 10. Because runaway gas accretion increases planetary mass by ∼10-300, the orbits are sufficiently circularized. On the other hand, a is reduced at most only by a factor of two, leaving the planets in the outer regions. If the relative velocity damping by shock is considered, the circularization slows down, but is still efficient enough. Therefore, this scenario potentially accounts for the formation of observed distant jupiters in nearly circular orbits. If the apocenter distances of the scattered cores are larger than the disk sizes, their a shrink to a quarter of the disk sizes; the a-distribution of distant giants could reflect the outer edges of the disks in a similar way that those of hot jupiters may reflect inner edges.« less

Fronto-orbital feminization technique. A surgical strategy using fronto-orbital burring with or without eggshell technique to optimize the risk/benefit ratio.

PubMed

Villepelet, A; Jafari, A; Baujat, B

2018-05-04

The demand for facial feminization is increasing in transsexual patients. Masculine foreheads present extensive supraorbital bossing with a more acute glabellar angle, whereas female foreheads show softer features. The aim of this article is to describe our surgical technique for fronto-orbital feminization. The mask-lift technique is an upper face-lift. It provides rejuvenation by correcting collapsed features, and fronto-orbital feminization through burring of orbital rims and lateral canthopexies. Depending on the size of the frontal sinus and the thickness of its anterior wall, frontal remodeling is achieved using simple burring or by means of the eggshell technique. Orbital remodeling comprises a superolateral orbital opening, a reduction of ridges and a trough at the lateral orbital rim to support the lateral canthopexy. Frontal, corrugator and procerus myectomies, plus minimal scalp excision, complete the surgery. Our technique results in significant, natural-looking feminization. No complications were observed in our series of patients. The eggshell technique is an alternative to bone flap on over-pneumatized sinus. Fronto-orbital feminization fits into a wider surgical strategy. It can be associated to rhinoplasty, genioplasty, mandibular angle remodeling, face lift and laryngoplasty. Achieving facial feminization in 2 or 3 stages improves psychological and physiological tolerance. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

A Model for Space Shuttle Orbiter Tire Side Forces Based on NASA Landing Systems Research Aircraft Test Results

NASA Technical Reports Server (NTRS)

Carter, John F.; Nagy, Christopher J.; Barnicki, Joseph S.

1997-01-01

Forces generated by the Space Shuttle orbiter tire under varying vertical load, slip angle, speed, and surface conditions were measured using the Landing System Research Aircraft (LSRA). Resulting data were used to calculate a mathematical model for predicting tire forces in orbiter simulations. Tire side and drag forces experienced by an orbiter tire are cataloged as a function of vertical load and slip angle. The mathematical model is compared to existing tire force models for the Space Shuttle orbiter. This report describes the LSRA and a typical test sequence. Testing methods, data reduction, and error analysis are presented. The LSRA testing was conducted on concrete and lakebed runways at the Edwards Air Force Flight Test Center and on concrete runways at the Kennedy Space Center (KSC). Wet runway tire force tests were performed on test strips made at the KSC using different surfacing techniques. Data were corrected for ply steer forces and conicity.

Probing Transient Valence Orbital Changes with Picosecond Valence-to-Core X-ray Emission Spectroscopy

DOE PAGES

March, Anne Marie; Assefa, Tadesse A.; Boemer, Christina; ...

2017-01-17

Here we probe the dynamics of valence electrons in photoexcited [Fe(terpy) 2] 2+ in solution to gain deeper insight into the Fe-ligand bond changes. We use hard X-ray emission spectroscopy (XES), which combines element specificity and high penetration with sensitivity to orbital structure, making it a powerful technique for molecular studies in a wide variety of environments. A picosecond-time-resolved measurement of the complete Is X-ray emission spectrum captures the transient photoinduced changes and includes the weak valence-to-core (vtc) emission lines that correspond to transitions from occupied valence orbitals to the nascent core-hole. Vtc-XES offers particular insight into the molecular orbitalsmore » directly involved in the light-driven dynamics; a change in the metal-ligand orbital overlap results in an intensity reduction and a blue energy shift in agreement with our theoretical calculations and more subtle features at the highest energies reflect changes in the frontier orbital populations.« less

Probing Transient Valence Orbital Changes with Picosecond Valence-to-Core X-ray Emission Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

March, Anne Marie; Assefa, Tadesse A.; Boemer, Christina

Here we probe the dynamics of valence electrons in photoexcited [Fe(terpy) 2] 2+ in solution to gain deeper insight into the Fe-ligand bond changes. We use hard X-ray emission spectroscopy (XES), which combines element specificity and high penetration with sensitivity to orbital structure, making it a powerful technique for molecular studies in a wide variety of environments. A picosecond-time-resolved measurement of the complete Is X-ray emission spectrum captures the transient photoinduced changes and includes the weak valence-to-core (vtc) emission lines that correspond to transitions from occupied valence orbitals to the nascent core-hole. Vtc-XES offers particular insight into the molecular orbitalsmore » directly involved in the light-driven dynamics; a change in the metal-ligand orbital overlap results in an intensity reduction and a blue energy shift in agreement with our theoretical calculations and more subtle features at the highest energies reflect changes in the frontier orbital populations.« less

Resolution and Orbit Reconstruction of Spectroscopic Binary Stars with the Palomar Testbed Interferometer

NASA Astrophysics Data System (ADS)

Boden, A. F.; Lane, B. F.; Creech-Eakman, M. J.; Queloz, D.; Koresko, C. D.

2000-05-01

The Palomar Testbed Interferometer (PTI) is a long-baseline near-infrared interferometer located at Palomar Observatory. For the past several years we have had an ongoing program of resolving and reconstructing the visual and physical orbits of spectroscopic binary stars with PTI, with the goal of obtaining precise dynamical mass estimates and other physical parameters. We will present a number of new visual and physical orbit determinations derived from integrated reductions of PTI visibility and archival and new spectroscopic radial velocity data. The systems for which we will discuss our orbit models are: iota Pegasi (HD 210027), 64 Psc (HD 4676), 12 Boo (HD 123999), 75 Cnc (HD 78418), 47 And (HD 8374), HD 205539, BY Draconis (HDE 234677), and 3 Boo (HD 120064), and 3 Boo (HD 120064). All of these systems are double-lined binary systems (SB2), and integrated astrometric/radial velocity orbit modeling provides precise fundamental parameters (mass, luminosity) and system distance determinations comparable with Hipparcos precisions.

IUS prerelease alignment

NASA Technical Reports Server (NTRS)

Evans, F. A.

1978-01-01

Space shuttle orbiter/IUS alignment transfer was evaluated. Although the orbiter alignment accuracy was originally believed to be the major contributor to the overall alignment transfer error, it was shown that orbiter alignment accuracy is not a factor affecting IUS alignment accuracy, if certain procedures are followed. Results are reported of alignment transfer accuracy analysis.

Selecting a launch vehicle : what factors do commercial satellite customers consider? : second quarter 2001 Quarterly Report Topic

DOT National Transportation Integrated Search

2001-01-01

Commercial satellite owners and operators clearly have the luxury of choice when it comes to selecting a launch vehicle to transport their assets into orbit. Whether the final destination is low-earth orbit (LEO), geostationary orbit (GEO), or somewh...

Definitive treatment of the negative vector orbit.

PubMed

Mommaerts, Maurice Y

2018-05-09

In a negative vector orbit, the most anterior globe portion protrudes past the malar eminence. As bulging eyes are considered unaesthetic, patients usually seek correction. However, most current correction techniques produce suboptimal results. Here, we present a surgical technique that sets back the globe and protrudes the malar bone using an intraoral approach. All five patients (aged 17-41 years) in our case series reported being satisfied with the improvement achieved using this technique. Based on our experience, a transoral approach to malar augmentation by valgisation osteotomy may address the bulging eyes aspect through transantral orbital fat reduction in select cases. Copyright © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

Lunar gravity derived from long-period satellite motion, a proposed method

NASA Technical Reports Server (NTRS)

Ferrari, A. J.

1971-01-01

A method was devised to determine the spherical harmonic coefficients of the lunar gravity field. The method consists of a two-step data reduction and estimation process. Pseudo-Doppler data were generated simulating two different lunar orbits. The analysis included the perturbing effects of the L1 lunar gravity field, the earth, the sun, and solar radiation pressure. Orbit determinations were performed on these data and long-period orbital elements were obtained. The Kepler element rates from these solutions were used to recover L1 lunar gravity coefficients. Overall results of the experiment show that lunar gravity coefficients can be accurately determined and that the method is dynamically consistent with long-period perturbation theory.

Enhanced solar energy options using earth-orbiting mirrors

NASA Technical Reports Server (NTRS)

Gilbreath, W. P.; Billman, K. W.; Bowen, S. W.

1978-01-01

A system of orbiting space reflectors is described, analyzed, and shown to economically provide nearly continuous insolation to preselected ground sites, producing benefits hitherto lacking in conventional solar farms and leading to large reductions in energy costs for such installations. Free-flying planar mirrors of about 1 sq km are shown to be optimum and can be made at under 10 g/sq m of surface, thus minimizing material needs and space transportation costs. Models are developed for both the design of such mirrors and for the analysis of expected ground insolation as a function of orbital parameters, time, and site location. Various applications (agricultural, solar-electric production, weather enhancement, etc.) are described.

KSC-98pc1160

NASA Image and Video Library

1998-09-27

KENNEDY SPACE CENTER, FLA. -- The Shuttle Carrier Aircraft with orbiter Atlantis on top touches down at the Shuttle Landing Facility. Atlantis returns home after a 10-month stay in the Palmdale, CA, orbiter processing facility undergoing extensive inspections and modifications. They included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. The flight from Palmdale included a fueling stop in Ft. Hood, TX, and overnight stay at Ft. Campbell, KY. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

KSC-98pc1167

NASA Image and Video Library

1998-09-28

Seen from behind, the orbiter Atlantis approaches the entrance of Orbiter Processing Facility 2 (OPF-2) where it will undergo preparations for its planned flight in June 1999. Atlantis spent 10 months in Palmdale, CA, undergoing extensive inspections and modifications in the orbiter processing facility there. The modifications included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. OPF-2 consists of a 2,700-square-meter (29,000 square ft.) high bay. The building measures 29 meters (95 ft). high, 121 meters (397 ft.) long and 71 meters (233 ft.) wide

KSC-98pc1161

NASA Image and Video Library

1998-09-27

KENNEDY SPACE CENTER, FLA. -- The Shuttle Carrier Aircraft gently lands its piggyback cargo orbiter Atlantis at the Shuttle Landing Facility. Atlantis returns home after a 10-month stay in the Palmdale, CA, orbiter processing facility undergoing extensive inspections and modifications. They included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. The flight from Palmdale included a fueling stop in Ft. Hood, TX, and overnight stay at Ft. Campbell, KY. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

KSC-98pc1159

NASA Image and Video Library

1998-09-27

KENNEDY SPACE CENTER, FLA. -- The Shuttle Carrier Aircraft with orbiter Atlantis on top arrives at the Shuttle Landing Facility. Atlantis returns home after a 10-month stay in the Palmdale, CA, orbiter processing facility undergoing extensive inspections and modifications. They included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. The flight from Palmdale included a fueling stop in Ft. Hood, TX, and overnight stay at Ft. Campbell, KY. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

KSC-98pc1168

NASA Image and Video Library

1998-09-28

Seen from behind, the orbiter Atlantis moves into the Orbiter Processing Facility 2 (OPF-2) where it will undergo preparations for its planned flight in June 1999. Atlantis spent 10 months in Palmdale, CA, undergoing extensive inspections and modifications in the orbiter processing facility there. The modifications included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. OPF-2 consists of two 2,700-square-meter (29,000 square feet) high bays. It measures 29 meters (95 ft). high, 121 meters (397 ft) long and 71 meters (233 ft) wide

Propulsion Options for the LISA Mission

NASA Technical Reports Server (NTRS)

Cardiff, Eric H.; Marr, Gregory C.

2004-01-01

The LISA mission is a constellation of three spacecraft operating at 1 AU from the Sun in a position trailing the Earth. After launch, a propulsion module provides the AV necessary to reach this operational orbit, and separates from the spacecraft. A second propulsion system integrated with the spacecraft maintains the operational orbit and reduces nongravitational disturbances on the instruments. Both chemical and electrical propulsion systems were considered for the propulsion module, and this trade is presented to show the possible benefits of an EP system. Several options for the orbit maintenance and disturbance reduction system are also briefly discussed, along with several important requirements that suggest the use of a FEEP thruster system.

Collision probability at low altitudes resulting from elliptical orbits

NASA Technical Reports Server (NTRS)

Kessler, Donald J.

1990-01-01

The probability of collision between a spacecraft and another object is calculated for various altitude and orbit conditions, and factors affecting the probability are discussed. It is shown that a collision can only occur when the spacecraft is located at an altitude which is between the perigee and apogee altitudes of the object and that the probability per unit time is largest when the orbit of the object is nearly circular. However, at low altitudes, the atmospheric drag causes changes with time of the perigee and the apogee, such that circular orbits have a much shorter lifetime than many of the elliptical orbits. Thus, when the collision probability is integrated over the lifetime of the orbiting object, some elliptical orbits are found to have much higher total collision probability than circular orbits. Rocket bodies used to boost payloads from low earth orbit to geosynchronous orbit are an example of objects in these elliptical orbits.

Backgrounds, radiation damage, and spacecraft orbits

NASA Astrophysics Data System (ADS)

Grant, Catherine E.; Miller, Eric D.; Bautz, Mark W.

2017-08-01

The scientific utility of any space-based observatory can be limited by the on-orbit charged particle background and the radiation-induced damage. All existing and proposed missions have had to make choices about orbit selection, trading off the radiation environment against other factors. We present simulations from ESA’s SPace ENVironment Information System (SPENVIS) of the radiation environment for spacecraft in a variety of orbits, from Low Earth Orbit (LEO) at multiple inclinations to High Earth Orbit (HEO) to Earth-Sun L2 orbit. We summarize how different orbits change the charged particle background and the radiation damage to the instrument. We also discuss the limitations of SPENVIS simulations, particularly outside the Earth’s trapped radiation and point to new resources attempting to address those limitations.

Basic research for the geodynamics program

NASA Technical Reports Server (NTRS)

1983-01-01

Laser systems deployed in satellite tracking were upgraded to accuracy levels where biases from systematic unmodelled effects constitute the basic factor that prohibits extraction of the full amount of information contained in the observations. Taking into consideration that the quality of the instrument advances at a faster pace compared to the understanding and modeling of the physical processes involved, one can foresee that in the near future when all lasers are replaced with third generation ones the limiting factor for the estimated accuracies will be the aforementioned biases. Therefore, for the reduction of the observations, methods should be deployed in such a way that the effect of the biases will be kept well below the noise level. Such a method was proposed and studied. This method consists of using the observed part of the satellite pass and converting the laser ranges into range differences in hopes that they will be less affected by biases in the orbital models, the reference system, and the observations themselves.

Foot Reaction Forces during Long Duration Space Flight

NASA Technical Reports Server (NTRS)

Gopalakrishnan, R.; Rice, A. J.; Genc, K. O.; Maender, C. C.; Kuklis, M. M.; Humphreys, B.; Cavanagh, P. R.

2008-01-01

Musculoskeletal changes, particularly in the lower extremities, are an established consequence of long-duration space flight despite exercise countermeasures. It is widely believed that disuse and reduction in load bearing are key to these physiological changes, but no quantitative data characterizing the on-orbit movement environments currently exist. Here we present data from the Foot Experiment (E318) regarding astronaut activity on the ground and on-orbit during typical days from 4 International Space Station (ISS) crew members who flew during increments 6, 8, 11, and 12.

Low-Earth orbit satellite servicing economics

NASA Technical Reports Server (NTRS)

Davis, R. F.; Cepollina, F. J.

1982-01-01

Servicing economics of low Earth orbit satellites were studied. The following topics are examined: the economic importance of the repair missions; comparison of mission cost as opposed to satellite modulation transfer functions over a 10 year period; the effect of satellite flight rate change due to changes in satellite failure rate; estimated satellite cost reduction with shuttle operation projects from the 1960's to the 1970's; design objectives of the multimission modular spacecraft; and the economic importance of the repair mission.

Mars Reconnaissance Orbiter Navigation During the Primary Science Phase

NASA Technical Reports Server (NTRS)

Highsmith, Dolan; You, Tung-Han; Demcak, Stuart; Graat, Eric; Higa, Earl; Long, Stacia; Bhat, Ram; Mottinger, Neil; Halsell, Allen; Peralta, Fernando

2008-01-01

The Mars Reconnaissance Orbiter began science operations in November 2006, with a suite of seven instruments and investigations, some of which required navigation accuracies much better than previous Mars missions. This paper describes the driving performance requirements levied on Navigation and how well those requirements have been met thus far. Trending analyses that have a direct impact on the Navigation performance, such as atmospheric bias determination, are covered in detail, as well as dynamic models, estimation strategy, tracking data reduction techniques, and residual noise.

Techniques for increasing the efficiency of Earth gravity calculations for precision orbit determination

NASA Technical Reports Server (NTRS)

Smith, R. L.; Lyubomirsky, A. S.

1981-01-01

Two techniques were analyzed. The first is a representation using Chebyshev expansions in three-dimensional cells. The second technique employs a temporary file for storing the components of the nonspherical gravity force. Computer storage requirements and relative CPU time requirements are presented. The Chebyshev gravity representation can provide a significant reduction in CPU time in precision orbit calculations, but at the cost of a large amount of direct-access storage space, which is required for a global model.

Space Human Factors: Research to Application

NASA Technical Reports Server (NTRS)

Woolford, Barbara

2008-01-01

Human Factors has been instrumental in preventing potential on-orbit hazards and increasing overall crew safety. Poor performance & operational learning curves on-orbit are mitigated. Human-centered design is applied to optimize design and minimize potentially hazardous conditions, especially with larger crew sizes and habitat constraints. Lunar and Mars requirements and design developments are enhanced, based on ISS Lessons Learned.

Theoretical studies of the local structures and spin Hamiltonian parameters for Cu2+ in alkaline earth alumino borate glasses

NASA Astrophysics Data System (ADS)

Guo, Jia-Xing; Wu, Shao-Yi; Kuang, Min-Quan; Peng, Li; Wu, Li-Na

2018-01-01

The local structures and spin Hamiltonian parameters are theoretically studied for Cu2+ in alkaline earth alumino borate (XAB, X = Mg, Ca and Sr) glasses by using the perturbation calculations for tetragonally elongated octahedral 3d9 groups. The [CuO6]10- groups are subject to the large relative tetragonal elongation ratios of 15.4%, 13.4% and 13.0% for MgAB, CaAB and SrAB glasses, respectively, arising from the Jahn-Teller effect. The decreasing cubic field parameter Dq, orbital reduction factor k and relative elongation ratio with the increase of the radius of alkaline earth ion X from Mg to Ca or Sr are analyzed for the studied systems in a uniform way.

The Laplace transformed divide-expand-consolidate resolution of the identity second-order Møller-Plesset perturbation (DEC-LT-RIMP2) theory method

NASA Astrophysics Data System (ADS)

Kjærgaard, Thomas

2017-01-01

The divide-expand-consolidate resolution of the identity second-order Møller-Plesset perturbation (DEC-RI-MP2) theory method introduced in Baudin et al. [J. Chem. Phys. 144, 054102 (2016)] is significantly improved by introducing the Laplace transform of the orbital energy denominator in order to construct the double amplitudes directly in the local basis. Furthermore, this paper introduces the auxiliary reduction procedure, which reduces the set of the auxiliary functions employed in the individual fragments. The resulting Laplace transformed divide-expand-consolidate resolution of the identity second-order Møller-Plesset perturbation method is applied to the insulin molecule where we obtain a factor 9.5 speedup compared to the DEC-RI-MP2 method.

Usage of pre-flight data in short rendezvous mission of Soyuz-TMA spacecrafts

NASA Astrophysics Data System (ADS)

Murtazin, Rafail; Petrov, Nikolay

2014-01-01

The paper describes the reduction of the vehicle autonomous flight duration before docking to the ISS. The Russian Soyuz-TMA spacecraft dock to the ISS two days after launch. Due to the limited volume inside Soyuz-TMA the reduction of time until docking to the ISS is very important, since the long stay of the cosmonauts in the limited volume adds to the strain of the space flight. In the previous papers of the authors it was shown that the existing capabilities of Soyuz-TMA, the ISS and the ground control loop make it possible to transfer to the five-orbit rendezvous profile. However, the analysis of the cosmonauts' schedule on the launch day shows that its duration is at the allowable limit and that is why it is necessary to find a way to further reduce the flight duration of Soyuz-TMA before docking to less than five orbits. In a traditional rendezvous profile, the calculation of rendezvous burns begins only after determination of the actual vehicle insertion orbit. The paper describes an approach in which the first two rendezvous burns are performed as soon as the spacecraft reaches the reference orbit and the values of the burns are calculated prior to the launch based on the pre-flight data for the nominal insertion. This approach decreases the duration of the rendezvous by one orbit. The demonstration flight of a Progress vehicle using the proposed profile was implemented on August 1, 2012 and completely confirmed the correctness of the imbedded principles. The paper considers the possible improvements of the proposed approach and recovery from the contingencies.

System technology analysis of aeroassisted orbital transfer vehicles - Moderate lift/drag

NASA Technical Reports Server (NTRS)

Florence, D. E.; Fischer, G.

1983-01-01

The utilization of procedures involving aerodynamic braking and/or aerodynamic maneuvering on return from higher altitude orbits to low-earth orbit makes it possible to realize significant performance benefits. The present study is concerned with a number of mission scenarios for Aeroassisted Orbital Transfer Vehicles (AOTV) and the impact of potential technology advances in the performance enhancement of the class of AOTV's having a hypersonic lift to drag ratio (L/D) of 0.75 to 1.5. It is found that the synergistic combination of a hypersonic L/D of 1.2, an advanced cryopropelled engine, and an LH2 drop tank (1-1/2 stage) leads to a single 65,000 pound shuttle, two-man geosynchronous mission with 2100 pounds of useful paylod. Additional payload enhancement is possible with AOTV dry weight reductions due to technology advances in the areas of vehicle structures and thermal protection systems and other subsystems.

An information theory approach for evaluating earth radiation budget (ERB) measurements - Nonuniform sampling of diurnal longwave flux variations

NASA Technical Reports Server (NTRS)

Halyo, Nesim; Direskeneli, Haldun; Barkstrom, Bruce R.

1991-01-01

Satellite measurements are subject to a wide range of uncertainties due to their temporal, spatial, and directional sampling characteristics. An information-theory approach is suggested to examine the nonuniform temporal sampling of ERB measurements. The information (i.e., its entropy or uncertainty) before and after the measurements is determined, and information gain (IG) is defined as a reduction in the uncertainties involved. A stochastic model for the diurnal outgoing flux variations that affect the ERB is developed. Using Gaussian distributions for the a priori and measured radiant exitance fields, the IG is obtained by computing the a posteriori covariance. The IG for the monthly outgoing flux measurements is examined for different orbital parameters and orbital tracks, using the Earth Observing System orbital parameters as specific examples. Variations in IG due to changes in the orbit's inclination angle and the initial ascending node local time are investigated.

Planetary protection implementation on Mars Reconnaissance Orbiter mission

NASA Astrophysics Data System (ADS)

Barengoltz, J.; Witte, J.

2008-09-01

In August 2005 NASA launched a large orbiting science observatory, the Mars Reconnaissance Orbiter (MRO), for what is scheduled to be a 5.4-year mission. High resolution imaging of the surface is a principal goal of the mission. One consequence of this goal however is the need for a low science orbit. Unfortunately this orbit fails the required 20-year orbit life set in NASA Planetary Protection (PP) requirements [NASA. Planetary protection provisions for robotic extraterrestrial missions, NASA procedural requirements NPR 8020.12C, NASA HQ, Washington, DC, April 2005.]. So rather than sacrifice the science goals of the mission by raising the science orbit, the MRO Project chose to be the first orbiter to pursue the bio-burden reduction approach. Cleaning alone for a large orbiter like MRO is insufficient to achieve the bio-burden threshold requirement in NASA PP requirements. The burden requirement for an orbiter includes spores encapsulated in non-metallic materials and trapped in joints, as well as located on all internal and external surfaces (the total spore burden). Total burden estimates are dominated by the mated and encapsulated burden. The encapsulated burden cannot be cleaned. The total burden of a smaller orbiter (e.g., Mars Odyssey) likely could not have met the requirement by cleaning; for the large MRO it is clearly impossible. Of course, a system-level partial sterilization, with its attendant costs and system design issues, could have been employed. In the approach taken by the MRO Project, hardware which will burn up (completely vaporize or ablate) before reaching the surface or will at least attain high temperature (500 °C for 0.5 s or more) due to entry heating was exempt from burden accounting. Thus the bio-burden estimate was reduced. Lockheed Martin engineers developed a process to perform what is called breakup and burn-up (B&B) analysis.Lockheed Martin Corporation.2 The use of the B&B analysis to comply with the spore burden requirement is the main subject of this article. However, several components aboard the orbiter were predicted to fail the minimum time at temperature requirements (or could not conservatively be shown to meet the conditions). An implementation plan was generated to address the highest contributors to the bio-burden assessment that fail to meet the requirements. The spore burden for these components was estimated by direct and proxy burden assays, NASA PP specifications, and dry heat microbial reduction, as appropriate. Items on the orbiter that required rework during assembly were also individually assessed. MRO met the spore burden requirement based on the B&B analysis, the MRO Planetary Protection Implementation Plan, and verification by the NASA Planetary Protection Officer’s (PPO) independent assays. The compliance was documented in the MRO PP Pre-Launch Report. MRO was approved for flight by the NASA PPO.

A Stable, Narrow-Gap Oxyfluoride Photocatalyst for Visible-Light Hydrogen Evolution and Carbon Dioxide Reduction.

PubMed

Kuriki, Ryo; Ichibha, Tom; Hongo, Kenta; Lu, Daling; Maezono, Ryo; Kageyama, Hiroshi; Ishitani, Osamu; Oka, Kengo; Maeda, Kazuhiko

2018-05-30

Mixed anion compounds such as oxynitrides and oxychalcogenides are recognized as potential candidates of visible-light-driven photocatalysts since, as compared with oxygen 2p orbitals, p orbitals of less electronegative anion (e.g., N 3- , S 2- ) can form a valence band that has more negative potential. In this regard, oxyfluorides appear unsuitable because of the higher electronegativity of fluorine. Here we show an exceptional case, an anion-ordered pyrochlore oxyfluoride Pb 2 Ti 2 O 5.4 F 1.2 that has a small band gap (ca. 2.4 eV). With suitable modification of Pb 2 Ti 2 O 5.4 F 1.2 by promoters such as platinum nanoparticles and a binuclear ruthenium(II) complex, Pb 2 Ti 2 O 5.4 F 1.2 worked as a stable photocatalyst for visible-light-driven H 2 evolution and CO 2 reduction. Density functional theory calculations have revealed that the unprecedented visible-light-response of Pb 2 Ti 2 O 5.4 F 1.2 arises from strong interaction between Pb-6s and O-2p orbitals, which is enabled by a short Pb-O bond in the pyrochlore lattice due to the fluorine substitution.

Investigation of very high energy rockets for future SSTO vehicles

NASA Astrophysics Data System (ADS)

Froning, H. D., Jr.

1989-04-01

Several new propulsion possibilities are being explored in the U.S.A. which might significantly increase the amount of payload that can be propelled into orbit for a given launch vehicle weight. As such, they might enable significant reduction in the future cost of transportation between earth and space. One possibility is the combustion of matter that is in an excited atomic or molecular state. Another possibility is the annihilation of matter by means of anti-matter (by matter with identical mass and opposite electrical charge). And if an appreciable fraction of the energies released by either of these processes could be converted into the useful kinetic energy of a rocket's exhaust, a 2-6-fold increase in its specific impulse might be achieved. This paper shows that a 2-6-fold increase in rocket specific impulse might enable a 4-12-fold reduction in aerospace vehicle weight. It also shows that the specific impulse potential of excited matter or anti-matter fuels might enable transport of heavy payloads into earth orbit by means of single-stage-to-orbit vehicles that would be no heavier than current commercial airline jets.

High-pressure insulator-to-metal transition in Sr3Ir2O7 studied by x-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Donnerer, C.; Sala, M. Moretti; Pascarelli, S.; Rosa, A. D.; Andreev, S. N.; Mazurenko, V. V.; Irifune, T.; Hunter, E. C.; Perry, R. S.; McMorrow, D. F.

2018-01-01

High-pressure x-ray absorption spectroscopy was performed at the Ir L3 and L2 absorption edges of Sr3Ir2O7 . The branching ratio of white-line intensities continuously decreases with pressure, reflecting a reduction in the angular part of the expectation value of the spin-orbit coupling operator, 〈L .S 〉 . Up to the high-pressure structural transition at 53 GPa, this behavior can be explained within a single-ion model, where pressure increases the strength of the cubic crystal field, which suppresses the spin-orbit induced hybridization of Jeff=3 /2 and eg levels. We observe a further reduction of the branching ratio above the structural transition, which cannot be explained within a single-ion model of spin-orbit coupling and cubic crystal fields. This change in 〈L .S 〉 in the high-pressure, metallic phase of Sr3Ir2O7 could arise from noncubic crystal fields or a bandwidth-driven hybridization of Jeff=1 /2 ,3 /2 states and suggests that the electronic ground state significantly deviates from the Jeff=1 /2 limit.

NASA's Orbital Space Plane Risk Reduction Strategy

NASA Technical Reports Server (NTRS)

Dumbacher, Dan

2003-01-01

This paper documents the transformation of NASA s Space Launch Initiative (SLI) Second Generation Reusable Launch Vehicle Program under the revised Integrated Space Transportation Plan, announced November 2002. Outlining the technology development approach followed by the original SLI, this paper gives insight into the current risk-reduction strategy that will enable confident development of the Nation s first orbital space plane (OSP). The OSP will perform an astronaut and contingency cargo transportation function, with an early crew rescue capability, thus enabling increased crew size and enhanced science operations aboard the International Space Station. The OSP design chosen for full-scale development will take advantage of the latest innovations American industry has to offer. The OSP Program identifies critical technologies that must be advanced to field a safe, reliable, affordable space transportation system for U.S. access to the Station and low-Earth orbit. OSP flight demonstrators will test crew safety features, validate autonomous operations, and mature thermal protection systems. Additional enabling technologies may be identified during the OSP design process as part of an overall risk-management strategy. The OSP Program uses a comprehensive and evolutionary systems acquisition approach, while applying appropriate lessons learned.

Origin of orbital debris impacts on LDEF's trailing surfaces

NASA Technical Reports Server (NTRS)

Kessler, Donald J.

1993-01-01

A model was developed to determine the origin of orbital impacts measured on the training surfaces of LDEF. The model calculates the expected debris impact crater distribution around LDEF as a function of debris orbital parameters. The results show that only highly elliptical, low inclination orbits could be responsible for these impacts. The most common objects left in this type of orbit are orbital transfer stages used by the U.S. and ESA to place payloads into geosynchronous orbit. Objects in this type of orbit are difficult to catalog by the U.S. Space Command; consequently there are independent reasons to believe that the catalog does not adequately represent this population. This analysis concludes that the relative number of cataloged objects with highly elliptical, low inclination orbits must be increased by a factor of 20 to be consistent with the LDEF data.

From Measure Zero to Measure Hero: Periodic Kerr Orbits and Gravitational Wave Physics

NASA Astrophysics Data System (ADS)

Perez-Giz, Gabriel

2011-12-01

A direct observational detection of gravitational waves -- perhaps the most fundamental prediction of a theory of curved spacetime -- looms close at hand. Stellar mass compact objects spiraling into supermassive black holes have received particular attention as sources of gravitational waves detectable by space-based gravitational wave observatories. A well-established approach models such an extreme mass ratio inspirals (EMRI) as an adiabatic progression through a series of Kerr geodesics. Thus, the direct detection of gravitational radiation from EMRIs and the extraction of astrophysical information from those waveforms require a thorough knowledge of the underlying geodesic dynamics. This dissertation adopts a dynamical systems approach to the study of Kerr orbits, beginning with equatorial orbits. We deduce a topological taxonomy of orbits that hinges on a correspondence between periodic orbits and rational numbers. The taxonomy defines the entire dynamics, including aperiodic motion, since every orbit is in or near the periodic set. A remarkable implication of this periodic orbit taxonomy is that the simple precessing ellipse familiar from planetary orbits is not allowed in the strong-field regime. Instead, eccentric orbits trace out precessions of multi-leaf clovers in the final stages of inspiral. Furthermore, for any black hole, there is some orbital angular momentum value in the strong-field regime below which zoom-whirl behavior becomes unavoidable. We then generalize the taxonomy to help identify nonequatorial orbits whose radial and polar frequencies are rationally related, or in resonance. The thesis culminates by describing how those resonant orbits can be leveraged for an order of magnitude or more reduction in the computational cost of adiabatic order EMRI trajectories, which are so prohibitively expensive that no such relativistically correct inspirals have been generated to date.

Orbit-product representation and correction of Gaussian belief propagation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Jason K; Chertkov, Michael; Chernyak, Vladimir

We present a new interpretation of Gaussian belief propagation (GaBP) based on the 'zeta function' representation of the determinant as a product over orbits of a graph. We show that GaBP captures back-tracking orbits of the graph and consider how to correct this estimate by accounting for non-backtracking orbits. We show that the product over non-backtracking orbits may be interpreted as the determinant of the non-backtracking adjacency matrix of the graph with edge weights based on the solution of GaBP. An efficient method is proposed to compute a truncated correction factor including all non-backtracking orbits up to a specified length.

Payload/orbiter contamination control requirement study

NASA Technical Reports Server (NTRS)

Bareiss, L. E.; Rantanen, R. O.; Ress, E. B.

1974-01-01

A study was conducted to determine and quantify the expected particulate and molecular on-orbit contaminant environment for selected space shuttle payloads as a result of major shuttle orbiter contamination sources. Individual payload susceptibilities to contamination are reviewed. The risk of payload degradation is identified and preliminary recommendations are provided concerning the limiting factors which may depend on operational activities associated with the payload/orbiter interface or upon independent payload functional activities. A basic computer model of the space shuttle orbiter which includes a representative payload configuration is developed. The major orbiter contamination sources, locations, and flux characteristics based upon available data have been defined and modeled.

Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.

PubMed

Carter, Joshua A; Agol, Eric; Chaplin, William J; Basu, Sarbani; Bedding, Timothy R; Buchhave, Lars A; Christensen-Dalsgaard, Jørgen; Deck, Katherine M; Elsworth, Yvonne; Fabrycky, Daniel C; Ford, Eric B; Fortney, Jonathan J; Hale, Steven J; Handberg, Rasmus; Hekker, Saskia; Holman, Matthew J; Huber, Daniel; Karoff, Christopher; Kawaler, Steven D; Kjeldsen, Hans; Lissauer, Jack J; Lopez, Eric D; Lund, Mikkel N; Lundkvist, Mia; Metcalfe, Travis S; Miglio, Andrea; Rogers, Leslie A; Stello, Dennis; Borucki, William J; Bryson, Steve; Christiansen, Jessie L; Cochran, William D; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer; Howard, Andrew W; Jenkins, Jon M; Klaus, Todd; Koch, David G; Latham, David W; MacQueen, Phillip J; Sasselov, Dimitar; Steffen, Jason H; Twicken, Joseph D; Winn, Joshua N

2012-08-03

In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.

Vigilance problems in orbiter processing

NASA Technical Reports Server (NTRS)

Swart, William W.; Safford, Robert R.; Kennedy, David B.; Yadi, Bert A.; Barth, Timothy S.

1993-01-01

A pilot experiment was done to determine what factors influence potential performance errors related to vigilance in Orbiter processing activities. The selected activities include post flight inspection for burned gap filler material and pre-rollout inspection for tile processing shim material. It was determined that the primary factors related to performance decrement were the color of the target and the difficulty of the target presentation.

Impulsive time-free transfers between halo orbits

NASA Astrophysics Data System (ADS)

Hiday, L. A.; Howell, K. C.

1992-08-01

A methodology is developed to design optimal time-free impulsive transfers between three-dimensional halo orbits in the vicinity of the interior L1 libration point of the sun-earth/moon barycenter system. The transfer trajectories are optimal in the sense that the total characteristics velocity required to implement the transfer exhibits a local minimum. Criteria are established whereby the implementation of a coast in the initial orbit, a coast in the final orbit, or dual coasts accomplishes a reduction in fuel expenditure. The optimality of a reference two-impulse transfer can be determined by examining the slope at the endpoints of a plot of the magnitude of the primer vector on the reference trajectory. If the initial and final slopes of the primer magnitude are zero, the transfer trajectory is optimal; otherwise, the execution of coasts is warranted. The optimal time of flight on the time-free transfer, and consequently, the departure and arrival locations on the halo orbits are determined by the unconstrained minimization of a function of two variables using a multivariable search technique. Results indicate that the cost can be substantially diminished by the allowance for coasts in the initial and final libration-point orbits.

Impulsive Time-Free Transfers Between Halo Orbits

NASA Astrophysics Data System (ADS)

Hiday-Johnston, L. A.; Howell, K. C.

1996-12-01

A methodology is developed to design optimal time-free impulsive transfers between three-dimensional halo orbits in the vicinity of the interior L 1 libration point of the Sun-Earth/Moon barycenter system. The transfer trajectories are optimal in the sense that the total characteristic velocity required to implement the transfer exhibits a local minimum. Criteria are established whereby the implementation of a coast in the initial orbit, a coast in the final orbit, or dual coasts accomplishes a reduction in fuel expenditure. The optimality of a reference two-impulse transfer can be determined by examining the slope at the endpoints of a plot of the magnitude of the primer vector on the reference trajectory. If the initial and final slopes of the primer magnitude are zero, the transfer trajectory is optimal; otherwise, the execution of coasts is warranted. The optimal time of flight on the time-free transfer, and consequently, the departure and arrival locations on the halo orbits are determined by the unconstrained minimization of a function of two variables using a multivariable search technique. Results indicate that the cost can be substantially diminished by the allowance for coasts in the initial and final libration-point orbits.

In Situ Splitting of a Rib Bone Graft for Reconstruction of Orbital Floor and Medial Wall.

PubMed

Uemura, Tetsuji; Yanai, Tetsu; Yasuta, Masato; Harada, Yoshimi; Morikawa, Aya; Watanabe, Hidetaka; Kurokawa, Masato

2017-06-01

In situ splitting of rib bone graft was conducted in 22 patients for the repair of orbital fracture with no other complicating fractures. A bone graft was harvested from the sixth or seventh rib in the right side. The repair of the orbital floor and medial wall was successful in all the cases. Ten patients had bone grafting to the orbital floor, eight had it done onto medial wall, and 4 onto both floor and wall after reduction. The mean length of in situ rib bone graft was 40.9 mm (range, 20-70 mm), the mean width of these was 14.9 mm (range, 8-20 mm). The bone grafting was done by one leaf for 15 cases and two leafs for 7 cases in size of defects. The technique of in situ splitting of a rib bone graft for the repair of the orbital floor and medial wall is a simple and safe procedure, easily taking out the in situ splitting of a rib, and less pain in donor site. It has proved to be an optimal choice in craniofacial reconstruction, especially the defects of orbital floor and medial wall.

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

PubMed Central

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; Orikasa, Yuki; Callewaert, Vincent; Kaprzyk, Staszek; Itou, Masayoshi; Yamamoto, Kentaro; Yamada, Ryota; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi; Bansil, Arun

2017-01-01

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. We show that inelastic scattering spectroscopy using high-energy x-ray photons (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials. PMID:28845452

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering.

PubMed

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; Orikasa, Yuki; Callewaert, Vincent; Kaprzyk, Staszek; Itou, Masayoshi; Yamamoto, Kentaro; Yamada, Ryota; Uchimoto, Yoshiharu; Sakurai, Yoshiharu; Sakurai, Hiroshi; Bansil, Arun

2017-08-01

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. We show that inelastic scattering spectroscopy using high-energy x-ray photons (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO 4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.

Elastic issues and vibration reduction in a tethered deorbiting mission

NASA Astrophysics Data System (ADS)

Sabatini, Marco; Gasbarri, Paolo; Palmerini, Giovanni B.

2016-05-01

Recently proposed mission concepts involving harpoons or nets to capture and de-orbit debris represent an interesting application of the tethered systems, where the orbiting bodies are connected by a flexible link. These systems present a complex behavior, as flexible characteristics combine with orbital dynamics. The focus of the paper is on the dynamic behavior of the tethered system in the final phase of the de-orbiting mission, when a powerful apogee motor is used to change the debris orbit. The thrust action introduces significant issues, as elastic waves propagate along the tether, and the relevant oscillations couple with the orbital dynamics. Input shaping techniques are proposed to limit or cancel these oscillations. However, the performance of these techniques drops when non-ideal scenarios are considered. In particular, an initially slack tether is a serious issue that must be solved if acceptably low oscillations of the tether are to be obtained. Three strategies are proposed and discussed in this paper to remove the slack condition: a natural drift of the chaser by means of a single impulse, a controlled maneuver for precisely adjusting the relative distance between chaser spacecraft and debris, and a retrieval mechanism for changing the tether length.

The Application of GIM in Precise Orbit Determination for LEO Satellites with Single-Frequency GPS Measurements

NASA Astrophysics Data System (ADS)

Peng, Dong-ju; Wu, Bin

2012-10-01

With the precise GPS ephemeris and clock error available, the iono- spheric delay is left as the dominant error source in the single-frequency GPS data. Thus, the removal of ionospheric effects is a ma jor prerequisite for an improved orbit reconstruction of LEO satellites based on the single-frequency GPS data. In this paper, the use of Global Ionospheric Maps (GIM) in kine- matic and dynamic orbit determinations for LEO satellites with single-frequency GPS pseudorange measurements is discussed first, and then, estimating the iono- spheric scale factor to remove the ionospheric effects from the C/A-code pseu- dorange measurements for both kinematic and dynamic orbit determinations is addressed. As it is known that the ionospheric delay of space-borne GPS sig- nals is strongly dependent on the orbit altitudes of LEO satellites, we select the real C/A-code pseudorange measurement data of the CHAMP, GRACE, TerraSAR-X and SAC-C satellites with altitudes between 300 km and 800 km as sample data in this paper. It is demonstrated that the approach to eliminating ionospheric effects in C/A-code pseudorange measurements by estimating the ionospheric scale factor is highly effective. Employing this approach, the accu- racy of both kinematic and dynamic orbits can be improved notably. Among those five LEO satellites, CHAMP with the lowest orbit altitude has the most remarkable improvements in orbit accuracy, which are 55.6% and 47.6% for kine- matic and dynamic orbits, respectively. SAC-C with the highest orbit altitude has the least improvements in orbit accuracy accordingly, which are 47.8% and 38.2%, respectively.

Systems analysis of solid fuel nuclear engines in cislunar space

NASA Astrophysics Data System (ADS)

Thomas, U.; Koelle, H. H.; Balzer-Sieb, R.; Bernau, D.; Czarnitzki, J.; Floete, A.; Goericke, D.; Lindenthal, A.; Protsch, R.; Teschner, O.

1984-12-01

The use of nuclear engines in cislunar space was studied and the restrictions imposed on nuclear ferries by the chemical Earth to lower Earth orbit (LEO) transportation system were analyzed. The operating conditions are best met by tungsten-water-moderated reactors due to a high specific impulse and long durability. Specific transportation cost for LEO to geostationary orbit (GEO) and LEO to lunar orbit flights were calculated for a transportation system life of 50 yr. Average transportation costs are estimated to be 141 $/kg. No difference is made for both routes. An additional analysis of smaller and larger flight units shows only small cost reductions by employing larger ferries but a significant cost increase in case smaller flight units are used.

KSC-98pc1162

NASA Image and Video Library

1998-09-27

KENNEDY SPACE CENTER, FLA. -- The Shuttle Carrier Aircraft rolls to a stop with its piggyback cargo orbiter Atlantis at the Shuttle Landing Facility. In the background is the Vehicle Assembly Building. Atlantis returns home after a 10-month stay in the Palmdale, CA, orbiter processing facility undergoing extensive inspections and modifications. They included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. The flight from Palmdale included a fueling stop in Ft. Hood, TX, and overnight stay at Ft. Campbell, KY. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

KSC-98pc1163

NASA Image and Video Library

1998-09-27

KENNEDY SPACE CENTER, FLA. -- Stairs are rolled to the forward opening of the Shuttle Carrier Aircraft with its piggyback cargo, the orbiter Atlantis after it rolls to a stop at the Shuttle Landing Facility. Atlantis returns home after a 10-month stay in the Palmdale, CA, orbiter processing facility undergoing extensive inspections and modifications. They included several upgrades enabling it to support International Space Station missions, such as adding an external airlock for ISS docking missions and installing thinner, lighter thermal protection blankets for weight reduction which will allow it to haul heavier cargo. The flight from Palmdale included a fueling stop in Ft. Hood, TX, and overnight stay at Ft. Campbell, KY. Atlantis will undergo preparations in the Orbiter Processing Facility at KSC for its planned flight in June 1999

Model and on-orbit study of the International space station contamination processes by jets of its orientation thrusters

NASA Astrophysics Data System (ADS)

Yarygin, V. N.; Gerasimov, Yu I.; Krylov, A. N.; Prikhodko, V. G.; Skorovarov, A. Yu; Yarygin, I. V.

2017-11-01

The main objective of this paper is to describe the current state of research for the problem of the International Space Station contamination by plumes of its orientation thrusters. Results of experiments carried out at the Institute of Thermophysics SB RAS modeling space vehicles orientation thruster’s plumes are presented and experimental setup is discussed. A novel approach to reduction of contamination by thrusters with the help of special gas-dynamic protective devices mounted at the exit part of the nozzle is suggested. The description and results of on-orbit experiment at the International Space Station are given. Results show good agreement for model and on-orbit experiments validating our approach.

Mars atmospheric opacity effects observed in the Northern Hemisphere by Viking orbiter imaging

NASA Technical Reports Server (NTRS)

Thorpe, T. E.

1981-01-01

Viking orbiter television camera observations of Mars contrasts show variations of atmospheric opacity in the Southern Hemisphere. The study is extended into the Northern Hemisphere, over a longer time period, and results in a detailed description of photometric changes at the lander sites, as seen from orbit. During the period of January 1977 to April 1978, a series of four storms at 202 deg, 264 deg, 40 deg and 86 deg latitudes have provided photometric changes and planetwide aerosol distributions for 18 months. It is found that the large, forward-scattering particles did not enter the atmosphere at the storm's onsets. A reduction of atmospheric transmission by over 20% at visual wavelengths remained for nearly one Martian year.

Power Extension Package (PEP) system definition extension, orbital service module systems analysis study. Volume 2: PEP

NASA Technical Reports Server (NTRS)

1979-01-01

User power, duration, and orbit requirements, which were the prime factors influencing power extension package (PEP) design, are discussed. A representative configuration of the PEP concept is presented and the major elements of the system are described as well as the PEP-to-Orbiter and remote manipulator interface provisions.

Theoretical studies of superconductivity in doped BaCoSO

NASA Astrophysics Data System (ADS)

Qin, Shengshan; Li, Yinxiang; Zhang, Qiang; Le, Congcong; Hu, Jiangping

2018-06-01

We investigate superconductivity that may exist in the doped BaCoSO, a multi-orbital Mott insulator with a strong antiferromagnetic ground state. The superconductivity is studied in both t-J type and Hubbard type multi-orbital models by mean field approach and random phase approximation (RPA) analysis. Even if there is no C 4 rotational symmetry, it is found that the system still carries a d-wave like pairing symmetry state with gapless nodes and sign changed superconducting order parameters on Fermi surfaces. The results are largely doping insensitive. In this superconducting state, the three {t_{{2_g}}} orbitals have very different superconducting form factors in momentum space. In particular, the intra-orbital pairing of the {d_{{x^2} - {y^2}}} orbital has an s-wave like pairing form factor. The two methods also predict very different pairing strength on different parts of Fermi surfaces. These results suggest that BaCoSO and related materials can be a new ground to test and establish fundamental principles for unconventional high temperature superconductivity.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naghavi, S. Shahab; Emery, Antoine A.; Hansen, Heine A.

Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has been the focus of most previous work. Here we report a different source of entropy, the onsite electronic configurational entropy, arising from coupling between orbital and spin angular momenta in lanthanide f orbitals. We find that onsite electronic configurational entropy is sizable in all lanthanides, and reaches a maximum value of ≈4.7 k B per oxygen vacancy for Cemore » 4+/Ce 3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions.« less

Electric Propulsion Options for a Magnetospheric Mapping Mission

NASA Technical Reports Server (NTRS)

Oleson, Steven; Russell, Chris; Hack, Kurt; Riehl, John

1998-01-01

The Twin Electric Magnetospheric Probes Exploring on Spiral Trajectories mission concept was proposed as a Middle Explorer class mission. A pre-phase-A design was developed which utilizes the advantages of electric propulsion for Earth scientific spacecraft use. This paper presents propulsion system analyses performed for the proposal. The proposed mission required two spacecraft to explore near circular orbits 0.1 to 15 Earth radii in both high and low inclination orbits. Since the use of chemical propulsion would require launch vehicles outside the Middle Explorer class a reduction in launch mass was sought using ion, Hall, and arcjet electric propulsion system. Xenon ion technology proved to be the best propulsion option for the mission requirements requiring only two Pegasus XL launchers. The Hall thruster provided an alternative solution but required two larger, Taurus launch vehicles. Arcjet thrusters did not allow for significant launch vehicle reduction in the Middle Explorer class.

Nano-JASMINE Data Analysis and Publication

NASA Astrophysics Data System (ADS)

Yamada, Y.; Hara, T.; Yoshioka, S.; Kobayashi, Y.; Gouda, N.; Miyashita, H.; Hatsutori, Y.; Lammers, U.; Michalik, D.

2012-09-01

The core data reduction for the Nano-JASMINE mission is planned to be done with Gaia's Astrometric Global Iterative Solution (AGIS). A collaboration between the Gaia AGIS and Nano-JASMINE teams on the Nano-JASMINE data reduction started in 2007. The Nano-JASMINE team writes codes to generate AGIS input, and this is called Initial Data Treament (IDT). Identification of observed stars and their observed field of view, getting color index, are different from those of Gaia because Nano-JASMINE is ultra small satellite. For converting centroiding results on detector to the celestial sphere, orbit and attitude data of the satellite are used. In Nano-JASMINE, orbit information is derived from on board GPS data and attitude is processed from on-board star sensor data and on-ground Kalman filtering. We also show the Nano-JASMINE goals, status of the data publications and utilizations, and introduce the next Japanese space astrometric mission.

Spin-orbit torque-induced switching in ferrimagnetic alloys: Experiments and modeling

NASA Astrophysics Data System (ADS)

Je, Soong-Geun; Rojas-Sánchez, Juan-Carlos; Pham, Thai Ha; Vallobra, Pierre; Malinowski, Gregory; Lacour, Daniel; Fache, Thibaud; Cyrille, Marie-Claire; Kim, Dae-Yun; Choe, Sug-Bong; Belmeguenai, Mohamed; Hehn, Michel; Mangin, Stéphane; Gaudin, Gilles; Boulle, Olivier

2018-02-01

We investigate spin-orbit torque (SOT)-induced switching in rare-earth-transition metal ferrimagnetic alloys using W/CoTb bilayers. The switching current is found to vary continuously with the alloy concentration, and no reduction in the switching current is observed at the magnetic compensation point despite a very large SOT efficiency. A model based on coupled Landau-Lifschitz-Gilbert (LLG) equations shows that the switching current density scales with the effective perpendicular anisotropy which does not exhibit strong reduction at the magnetic compensation, explaining the behavior of the switching current density. This model also suggests that conventional SOT effective field measurements do not allow one to conclude whether the spins are transferred to one sublattice or just simply to the net magnetization. The effective spin Hall angle measurement shows an enhancement of the spin Hall angle with the Tb concentration which suggests an additional SOT contribution from the rare earth Tb atoms.

An intelligent interface for satellite operations: Your Orbit Determination Assistant (YODA)

NASA Technical Reports Server (NTRS)

Schur, Anne

1988-01-01

An intelligent interface is often characterized by the ability to adapt evaluation criteria as the environment and user goals change. Some factors that impact these adaptations are redefinition of task goals and, hence, user requirements; time criticality; and system status. To implement adaptations affected by these factors, a new set of capabilities must be incorporated into the human-computer interface design. These capabilities include: (1) dynamic update and removal of control states based on user inputs, (2) generation and removal of logical dependencies as change occurs, (3) uniform and smooth interfacing to numerous processes, databases, and expert systems, and (4) unobtrusive on-line assistance to users of concepts were applied and incorporated into a human-computer interface using artificial intelligence techniques to create a prototype expert system, Your Orbit Determination Assistant (YODA). YODA is a smart interface that supports, in real teime, orbit analysts who must determine the location of a satellite during the station acquisition phase of a mission. Also described is the integration of four knowledge sources required to support the orbit determination assistant: orbital mechanics, spacecraft specifications, characteristics of the mission support software, and orbit analyst experience. This initial effort is continuing with expansion of YODA's capabilities, including evaluation of results of the orbit determination task.

Technical and Economical study of New Technologies and Reusable Space Vehicles promoting Space Tourism.

NASA Astrophysics Data System (ADS)

Srivastav, Deepanshu; Malhotra, Sahil

2012-07-01

For many of us space tourism is an extremely fascinating and attractive idea. But in order for these to start we need vehicles that will take us to orbit and bring us back. Current space vehicles clearly cannot. Only the Space Shuttle survives past one use, and that's only if we ignore the various parts that fall off on the way up. So we need reusable launch vehicles. Launch of these vehicles to orbit requires accelerating to Mach 26, and therefore it uses a lot of propellant - about 10 tons per passenger. But there is no technical reason why reusable launch vehicles couldn't come to be operated routinely, just like aircraft. The main problem about space is how much it costs to get there, it's too expensive. And that's mainly because launch vehicles are expendable - either entirely, like satellite launchers, or partly, like the space shuttle. The trouble is that these will not only reduce the cost of launch - they'll also put the makers out of business, unless there's more to launch than just a few satellites a year, as there are today. Fortunately there's a market that will generate far more launch business than satellites ever well - passenger travel. This paper assesses this emerging market as well as technology that will make space tourism feasible. The main conclusion is that space vehicles can reduce the cost of human transport to orbit sufficiently for large new commercial markets to develop. Combining the reusability of space vehicles with the high traffic levels of space tourism offers the prospect of a thousandfold reduction in the cost per seat to orbit. The result will be airline operations to orbit involving dozens of space vehicles, each capable of more than one flight per day. These low costs will make possible a rapid expansion of space science and exploration. Luckily research aimed at developing low-cost reusable launch vehicles has increased recently. Already there are various projects like Spaceshipone, Spaceshiptwo, Spacebus, X-33 NASA etc. The prototypes of such small orbital space vehicles, needed to trigger this line of development. Other technologies like Space Hotels and their size, structure and maintenance is another important factor in Space tourism.

On the Determination of the Orbits of Comets

NASA Astrophysics Data System (ADS)

Englefield, Henry

2013-06-01

Preface; 1. General view of the method; 2. On the motion of the point of intersection of the radius vector and cord; 3. On the comparison of the parabolic cord with the space which answers to the mean velocity of the earth in the same time; 4. Of the reduction of the second longitude of the comet; 5. On the proportion of the three curtate distances of the comet from the earth; 6. Of the graphical declination of the orbit of the earth; 7. Of the numerical quantities to be prepared for the construction or computation of the comet's orbit; 8. Determination of the distances of the comet from the earth and the sun; 9. Determination of the elements of the orbit from the determined distances; 10. Determination of the place of the comet from the earth and sun; 11. Determination of the distances of the comet from the earth and sun; 12. Determination of the comet's orbit; 13. Determination of the place of the comet; 14. Application of the graphical method to the comet of 1769; 15. Application of the distances found; 16. Determination of the place of the comet, for another given time; 17. Application of the trigonometrical method to the comet of 1769; 18. Determination of the elements of the orbit of the comet of 1769; Example of the graphical operation for the orbit of the comet of 1769; Example of the trigonometrical operation for the orbit of the comet of 1769; Conclusion; La Place's general method for determining the orbits of comets; Determination of the two elements of the orbit; Application of La Place's method of finding the approximate perihelion distance; Application of La Place's method for correcting the orbit of a comet, to the comet of 1769; Explanation and use of the tables; Tables; Appendix; Plates.

Effects on the orbital debris environment due to solar activity

NASA Technical Reports Server (NTRS)

Kessler, Donald J.; Anz-Meador, Phillip D.

1990-01-01

The rate that earth-orbiting debris is removed from the environment is dependent on a number of factors which include orbital altitude and solar activity. It is generally believed that at lower altitudes and especially during periods of high solar activity, debris generated in the past will be eliminated from the environment. While some debris is eliminated, most is replaced by old debris from higher altitudes or new debris from recent launches. Some low altitude debris, which would reenter if the debris were in circular orbits, does not reenter because the debris is in higher-energy elliptical orbits.

Orbit determination of highly elliptical Earth orbiters using improved Doppler data-processing modes

NASA Technical Reports Server (NTRS)

Estefan, J. A.

1995-01-01

A navigation error covariance analysis of four highly elliptical Earth orbits is described, with apogee heights ranging from 20,000 to 76,800 km and perigee heights ranging from 1,000 to 5,000 km. This analysis differs from earlier studies in that improved navigation data-processing modes were used to reduce the radio metric data. For this study, X-band (8.4-GHz) Doppler data were assumed to be acquired from two Deep Space Network radio antennas and reconstructed orbit errors propagated over a single day. Doppler measurements were formulated as total-count phase measurements and compared to the traditional formulation of differenced-count frequency measurements. In addition, an enhanced data-filtering strategy was used, which treated the principal ground system calibration errors affecting the data as filter parameters. Results suggest that a 40- to 60-percent accuracy improvement may be achievable over traditional data-processing modes in reconstructed orbit errors, with a substantial reduction in reconstructed velocity errors at perigee. Historically, this has been a regime in which stringent navigation requirements have been difficult to meet by conventional methods.

Direct Visualization of Orbital Flipping in Volborthite by Charge Density Analysis Using Detwinned Data

NASA Astrophysics Data System (ADS)

Sugawara, Kento; Sugimoto, Kunihisa; Fujii, Tatsuya; Higuchi, Takafumi; Katayama, Naoyuki; Okamoto, Yoshihiko; Sawa, Hiroshi

2018-02-01

The distribution of d-orbital valence electrons in volborthite [Cu3V2O7(OH)2 • 2H2O] was investigated by charge density analysis of the multipole model refinement. Diffraction data were obtained by synchrotron radiation single-crystal X-ray diffraction experiments. Data reduction by detwinning of the multiple structural domains was performed using our developed software. In this study, using high-quality data, we demonstrated that the water molecules in volborthite can be located by the hydrogen bonding in cavities that consist of Kagome lattice layers of CuO4(OH)2 and pillars of V2O7. Final multipole refinements before and after the structural phase transition directly visualized the deformation electron density of the valence electrons. We successfully directly visualized the orbital flipping of the d-orbital dx2-y2, which is the highest level of 3d orbitals occupied by d9 electrons in volborthite. The developed techniques and software can be employed for investigations of structural properties of systems with multiple structural domains.

Orbital transfer of large space structures with nuclear electric rockets

NASA Technical Reports Server (NTRS)

Silva, T. H.; Byers, D. C.

1980-01-01

This paper discusses the potential application of electric propulsion for orbit transfer of a large spacecraft structure from low earth orbit to geosynchronous altitude in a deployed configuration. The electric power was provided by the spacecraft nuclear reactor space power system on a shared basis during transfer operations. Factors considered with respect to system effectiveness included nuclear power source sizing, electric propulsion thruster concept, spacecraft deployment constraints, and orbital operations and safety. It is shown that the favorable total impulse capability inherent in electric propulsion provides a potential economic advantage over chemical propulsion orbit transfer vehicles by reducing the number of Space Shuttle flights in ground-to-orbit transportation requirements.

Operational factors affecting microgravity levels in orbit

NASA Technical Reports Server (NTRS)

Olsen, R. E.; Mockovciak, J., Jr.

1980-01-01

Microgravity levels desired for proposed materials processing payloads are fundamental considerations in the design of future space platforms. Disturbance sources, such as aerodynamic drag, attitude control torques, crew motion and orbital dynamics, influence the microgravity levels attainable in orbit. The nature of these effects are assessed relative to platform design parameters such as orbital altitude and configuration geometry, and examples are presented for a representative spacecraft configuration. The possible applications of control techniques to provide extremely low acceleration levels are also discussed.

Floating Potential Probe Langmuir Probe Data Reduction Results

NASA Technical Reports Server (NTRS)

Morton, Thomas L.; Minow, Joseph I.

2002-01-01

During its first five months of operations, the Langmuir Probe on the Floating Potential Probe (FPP) obtained data on ionospheric electron densities and temperatures in the ISS orbit. In this paper, the algorithms for data reduction are presented, and comparisons are made of FPP data with ground-based ionosonde and Incoherent Scattering Radar (ISR) results. Implications for ISS operations are detailed, and the need for a permanent FPP on ISS is examined.

Experimental Design for the Evaluation of Detection Techniques of Hidden Corrosion Beneath the Thermal Protective System of the Space Shuttle Orbiter

NASA Technical Reports Server (NTRS)

Kammerer, Catherine C.; Jacoby, Joseph A.; Lomness, Janice K.; Hintze, Paul E.; Russell, Richard W.

2007-01-01

The United States Space Operational Space Shuttle Fleet Consists of three shuttles with an average age of 19.7 years. Shuttles are exposed to corrosive conditions while undergoing final closeout for missions at the launch pad and extreme conditions during ascent, orbit, and descent that may accelerate the corrosion process. Structural corrosion under TPS could progress undetected (without tile removal) and eventually result in reduction in structural capability sufficient to create negative margins of . safety and ultimate loss of local structural capability.

A Case of Orbital Abscess following Porous Orbital Implant Infection

PubMed Central

Hong, Seung Woo; Paik, Ji-Sun; Kim, So-Youl

2006-01-01

Purpose We present a case of orbital abscess following porous orbital implant infection in a 73-year-old woman with rheumatoid arthritis. Methods Just one month after a seemingly uncomplicated enucleation and porous polyethylene (Medpor®) orbital implant surgery, implant exposure developed with profuse pus discharge. The patient was unresponsive to implant removal and MRI confirmed the presence of an orbital pus pocket. Despite extirpation of the four rectus muscles, inflammatory granulation debridement and abscess drainage, another new pus pocket developed. Results After partial orbital exenteration, the wound finally healed well without any additional abscess formation. Conclusions A patient who has risk factors for delayed wound healing must be examined thoroughly and extreme care such as exenteration must be taken if there is persistent infection. PMID:17302210

GPS-Based Reduced Dynamic Orbit Determination Using Accelerometer Data

NASA Technical Reports Server (NTRS)

VanHelleputte, Tom; Visser, Pieter

2007-01-01

Currently two gravity field satellite missions, CHAMP and GRACE, are equipped with high sensitivity electrostatic accelerometers, measuring the non-conservative forces acting on the spacecraft in three orthogonal directions. During the gravity field recovery these measurements help to separate gravitational and non-gravitational contributions in the observed orbit perturbations. For precise orbit determination purposes all these missions have a dual-frequency GPS receiver on board. The reduced dynamic technique combines the dense and accurate GPS observations with physical models of the forces acting on the spacecraft, complemented by empirical accelerations, which are stochastic parameters adjusted in the orbit determination process. When the spacecraft carries an accelerometer, these measured accelerations can be used to replace the models of the non-conservative forces, such as air drag and solar radiation pressure. This approach is implemented in a batch least-squares estimator of the GPS High Precision Orbit Determination Software Tools (GHOST), developed at DLR/GSOC and DEOS. It is extensively tested with data of the CHAMP and GRACE satellites. As accelerometer observations typically can be affected by an unknown scale factor and bias in each measurement direction, they require calibration during processing. Therefore the estimated state vector is augmented with six parameters: a scale and bias factor for the three axes. In order to converge efficiently to a good solution, reasonable a priori values for the bias factor are necessary. These are calculated by combining the mean value of the accelerometer observations with the mean value of the non-conservative force models and empirical accelerations, estimated when using these models. When replacing the non-conservative force models with accelerometer observations and still estimating empirical accelerations, a good orbit precision is achieved. 100 days of GRACE B data processing results in a mean orbit fit of a few centimeters with respect to high-quality JPL reference orbits. This shows a slightly better consistency compared to the case when using force models. A purely dynamic orbit, without estimating empirical accelerations thus only adjusting six state parameters and the bias and scale factors, gives an orbit fit for the GRACE B test case below the decimeter level. The in orbit calibrated accelerometer observations can be used to validate the modelled accelerations and estimated empirical accelerations computed with the GHOST tools. In along track direction they show the best resemblance, with a mean correlation coefficient of 93% for the same period. In radial and normal direction the correlation is smaller. During days of high solar activity the benefit of using accelerometer observations is clearly visible. The observations during these days show fluctuations which the modelled and empirical accelerations can not follow.

The Application of GIM in Precise Orbit Determination for LEO Satellites with Single-frequency GPS Measurements

NASA Astrophysics Data System (ADS)

Peng, D. J.; Wu, B.

2012-01-01

With the availability of precise GPS ephemeris and clock solution, the ionospheric range delay is left as the dominant error sources in the post-processing of space-borne GPS data from single-frequency receivers. Thus, the removal of ionospheric effects is a major prerequisite for an improved orbit reconstruction of LEO satellites equipped with low cost single-frequency GPS receivers. In this paper, the use of Global Ionospheric Maps (GIM) in kinematic and dynamic orbit determination for LEO satellites with single-frequency GPS measurements is discussed first,and then, estimating the scale factor of ionosphere to remove the ionospheric effects in C/A code pseudo-range measurements in both kinematic and adynamia orbit defemination approaches is addressed. As it is known the ionospheric path delay of space-borne GPS signals is strongly dependent on the orbit altitudes of LEO satellites, we selected real space-borne GPS data from CHAMP, GRACE, TerraSAR-X and SAC-C satellites with altitudes between 300 km and 800 km as sample data in this paper. It is demonstrated that the approach of eliminating ionospheric effects in space-borne C/A code pseudo-range by estimating the scale factor of ionosphere is highly effective. Employing this approach, the accuracy of both kinematic and dynamic orbits can be improved notably. Among those five LEO satellites, CHAMP with the lowest orbit altitude has the most remarkable orbit accuracy improvements, which are 55.6% and 47.6% for kinematic and dynamic approaches, respectively. SAC-C with the highest orbit altitude has the least orbit accuracy improvements accordingly, which are 47.8% and 38.2%, respectively.

Telecommunications systems evolution for Mars Exploration

NASA Technical Reports Server (NTRS)

Noreen, Gary; De Paula, Ramon P.; Edwards, Charles D. Jr; Komarek, Thomas; Edwards, Bernard L.; Edwards, Bernard L.; Kerridge, Stuart J.; Diehl, Roger; Franklin, Stephen F.

2003-01-01

This paper describes the evolution of telecommunication systems at Mars. It reviews the telecommunications capabilities, technology and limiting factors of current and planned Mars orbiters from Mars Global Surveyor to the planned Mars Telecommunications Orbiter (MTO).

Management of maxillofacial injuries in Iraq.

PubMed

Kummoona, Raja

2011-09-01

These clinical studies reflect the experience of the author in managing 673 patients treated during the last 8 years. All patients were treated in the Maxillofacial Unit, Surgical Specialties Hospital, Medical City, Baghdad, and in the author's private clinic. Included patients were 530 males and 143 females; patients' age ranged between 1 year and 75 years (mean, 38 y). Distribution of injuries was as follows: fracture of the mandible, 287 (42.64%); middle third injuries, 39 (5.79%); orbital injuries, 236 (35.07%; including 12 cases with cranioorbital injuries); injuries in children, 27 (4.0%); fracture of the zygoma, 52 (7.73%); and fracture of the nose, 40 (5.94%).Maxillofacial injuries in this study were classified as follows: (1) craniomaxillofacial with head injuries and cerebrospinal fluid leak; (2) fracture of the middle third including Le Fort I, II, and III and midline split in the face; (3) fracture of the mandible as an isolated injury or as part of a facial skeleton injury; and (4) isolated complex injuries of the zygoma, the orbital skeleton, and the nasoethmoidal region.The technique used for treating middle third injuries was external fixation either by halo frame (with vertical rods and cheek wires) or by box frame (using 4 external pins connected by rods) or internal fixation by suspending the middle third with internal wires (0.5 mm stainless steel) from the zygomatic process of the frontal bone beneath the zygomatic arch down the lower arch bar. Fractures of the mandible were treated by gunning splint with intermaxillary fixation (IMF) or with open reduction and fixation by stainless steel wire with IMF or by IMF screw or by an arch bar and IMF. Other fractures such as fracture of the orbit were treated by bone graft, sialastic, or lyophilized dura with open reduction. Fractures of the zygoma were treated by open reduction and fixation with stainless steel wire and bone graft or by reduction without fixation. Fractures of the nose were treated by reduction with straightening of the septum with a splint (lead splint or polythene) or by external splint with plaster of Paris. With the techniques used, results from managing these cases were satisfactory.

A complete solution for GP-B's gyroscopic precession by retarded gravitational theory

NASA Astrophysics Data System (ADS)

Tang, Keyun

Mainstream physicists generally believe that Mercury’s Perihelion precession and GP-B’ gyroscopic precession are two of the strongest evidences supporting Einstein’ curved spacetime and general relativity. However, most classical literatures and textbooks (e.g. Ohanain: Gravitation and Spacetime) paint an incorrect picture of Mercury’s orbit anomaly, namely Mercury’s perihelion precessed 43 arc-seconds per century; a correct picture should be that Mercury rotated 43 arc-seconds per century more than along Newtonian theoretical orbit. The essence of Le Verrier’s and Newcomb’s observation and analysis is that the angular speed of Mercury is slightly faster than the Newtonian theoretical value. The complete explanation to Mercury’s orbit anomaly should include two factors, perihelion precession is one of two factors, in addition, the change of orbital radius will also cause a change of angular speed, which is another component of Mercury's orbital anomaly. If Schwarzschild metric is correct, then the solution of the Schwarzschild orbit equation must contain three non-ignorable items. The first corresponds to Newtonian ellipse; the second is a nonlinear perturbation with increasing amplitude, which causes the precession of orbit perihelion; this is just one part of the angular speed anomaly of Mercury; the third part is a linear perturbation, corresponding to a similar figure of the Newton's ellipse, but with a minimal radius; this makes no contribution to the perihelion precession of the Schwarzschild orbit, but makes the Schwarzschild orbital radius slightly smaller, leading to a slight increase in Mercury’s angular speed. All classical literatures of general relativity ignored this last factor, which is a gross oversight. If you correctly take all three factors into consideration, the final result is that the difference between the angles rotated along Schwarzschild’s orbit and the angle rotated along Newton’s orbit for one hundred years should be more than 130.5 arc-seconds; this means that Le Verrier’s observation on Mercury’s orbital anomaly can not be explained correctly by the Schwarzschild metric. In contrast, Mercury’s angular speed anomaly can be explained satisfactorily by the radial induction component and angular component of retarded gravitation. From the perspective of energy, the additional radial component of retarded gravitation makes the radius of Mercury’s orbit slightly smaller, i.e. some potential energy is lost. And the angular component of retarded gravitation changes the Mercury's angular momentum; this proves that the changes of Mercury’s orbit and angular speed are the results of gravitational radiation. I have found that there are similar errors in the explanation on the gyroscopic precession of GP-B, i.e. physicists only consider the contribution of the nonlinear perturbation terms and never consider the contribution of linear perturbation terms. For the precession of GP-B, the complete Schwarzschild’s solution should be about 19.8 arc-seconds per year; it is far more than the experimental results of 6.602 arc-seconds per year. I have calculated the gyroscopic precession of GP-B due to retarded gravitation, the result is 6.607 arc-seconds per year; this matches well with the experimental results. These successful explanations for both anomalies of Mercury’s orbit and the gyroscopic precession of GP -B shows that Retarded Gravitation is indeed a sound gravitational theory, and that spacetime is in fact flat, and gravity travels at the speed of light. Both Mercury’s angular speed anomaly and GP - B gyro precession were the result of the gravitational radiation!

Reduction of atmospheric disturbances in PSInSAR measure technique based on ENVISAT ASAR data for Erta Ale Ridge

NASA Astrophysics Data System (ADS)

Kopeć, Anna

2018-01-01

The interferometric synthetic aperture radar (InSAR) is becoming more and more popular to investigate surface deformation, associated with volcanism, earthquakes, landslides, and post-mining surface subsidence. The measuring accuracy depends on many factors: surface, time and geometric decorrelation, orbit errors, however the largest challenges are the tropospheric delays. The spatial and temporal variations in temperature, pressure, and relative humidity are responsible for tropospheric delays. So far, many methods have been developed, but researchers are still searching for the one, that will allow to correct interferograms consistently in different regions and times. The article focuses on examining the methods based on empirical phase-based methods, spectrometer measurements and weather model. These methods were applied to the ENVISAT ASAR data for the Erta Ale Ridge in the Afar Depression, East Africa

Final Design for a Comprehensive Orbital Debris Management Program

NASA Technical Reports Server (NTRS)

1990-01-01

The rationale and specifics for the design of a comprehensive program for the control of orbital debris, as well as details of the various components of the overall plan, are described. The problem of orbital debris has been steadily worsening since the first successful launch in 1957. The hazards posed by orbital debris suggest the need for a progressive plan for the prevention of future debris, as well as the reduction of the current debris level. The proposed debris management plan includes debris removal systems and preventative techniques and policies. The debris removal is directed at improving the current debris environment. Because of the variance in sizes of debris, a single system cannot reasonably remove all kinds of debris. An active removal system, which deliberately retrieves targeted debris from known orbits, was determined to be effective in the disposal of debris tracked directly from earth. However, no effective system is currently available to remove the untrackable debris. The debris program is intended to protect the orbital environment from future abuses. This portion of the plan involves various environment from future abuses. This portion of the plan involves various methods and rules for future prevention of debris. The preventative techniques are protective methods that can be used in future design of payloads. The prevention policies are rules which should be employed to force the prevention of orbital debris.

Laser-boosted lightcraft technology demonstrator

NASA Technical Reports Server (NTRS)

Richard, J. C.; Morales, C.; Smith, W. L.; Myrabo, L. N.

1990-01-01

The detailed description and performance analysis of a 1.4 meter diameter Lightcraft Technology Demonstator (LTD) is presented. The launch system employs a 100 MW-class ground-based laser to transmit power directly to an advanced combined-cycle engine that propels the 120 kg LTD to orbit - with a mass ratio of two. The single-stage-to-orbit (SSTO) LTD machine then becomes an autonomous sensor satellite that can deliver precise, high quality information typical of today's large orbital platforms. The dominant motivation behind this study is to provide an example of how laser propulsion and its low launch costs can induce a comparable order-of-magnitude reduction in sensor satellite packaging costs. The issue is simply one of production technology for future, survivable SSTO aerospace vehicles that intimately share both laser propulsion engine and satellite functional hardware.

Taking advantage of inclination variation in resonant remote-sensing satellite orbits

NASA Astrophysics Data System (ADS)

Gopinath, N. S.; Ravindrababu, T.; Rao, S. V.; Daniel, D. A.; Goel, P. S.

2004-08-01

The inclination of remote-sensing satellites, which are generally placed in sun-synchronous orbits, varies as a function of the nominal equatorial crossing local mean solar time selected for a given mission. The Indian Remote-Sensing satellites will have an inclination reduction of about 0.034° per year and for most of the satellites, the local time chosen was around 10:30 hours at descending node. In practice, the initial inclination is biased appropriately so that the expensive out-of-plane maneuvers could be taken up after few years of mission operations, depending on the deviations permitted in the local time for a given mission. However, the scenario differs when the mission objectives require an almost exact repeat orbit of 14 or 15 per day. In such a situation, the satellite orbit, which passes through a 14th or 15th order resonance, undergoes a nearly secular increase in orbit inclination. This paper presents a detailed analysis carried out for such an orbit, based on Cowell's approach. Long-term predictions have been carried out by considering all major forces that perturbs the satellite orbit. Observed behavior of orbit, based on the daily definitive orbit determination is also presented. The variation in inclination and the cause is clearly brought out. Further, it is demonstrated that the selection of longitude for nominal ground track pattern has an impact on the inclination variation. A proposal is made to take advantage of such expected inclination variation so that initial inclination bias can be chosen appropriately. Ground track longitude can be chosen to take advantage, subject to the mission coverage requirements. The paper contains the results of an exhaustive analysis of the actually observed orbit resonance. It is felt that the work has both theoretical and operational importance for remote-sensing missions.

Periodic orbit analysis of a system with continuous symmetry--A tutorial.

PubMed

Budanur, Nazmi Burak; Borrero-Echeverry, Daniel; Cvitanović, Predrag

2015-07-01

Dynamical systems with translational or rotational symmetry arise frequently in studies of spatially extended physical systems, such as Navier-Stokes flows on periodic domains. In these cases, it is natural to express the state of the fluid in terms of a Fourier series truncated to a finite number of modes. Here, we study a 4-dimensional model with chaotic dynamics and SO(2) symmetry similar to those that appear in fluid dynamics problems. A crucial step in the analysis of such a system is symmetry reduction. We use the model to illustrate different symmetry-reduction techniques. The system's relative equilibria are conveniently determined by rewriting the dynamics in terms of a symmetry-invariant polynomial basis. However, for the analysis of its chaotic dynamics, the "method of slices," which is applicable to very high-dimensional problems, is preferable. We show that a Poincaré section taken on the "slice" can be used to further reduce this flow to what is for all practical purposes a unimodal map. This enables us to systematically determine all relative periodic orbits and their symbolic dynamics up to any desired period. We then present cycle averaging formulas adequate for systems with continuous symmetry and use them to compute dynamical averages using relative periodic orbits. The convergence of such computations is discussed.

Shearographic Non-destructive Evaluation of Space Shuttle Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Davis, Christopher K.; Hooker, Jeffery A.; Simmons, Stephen A.; Tenbusch, Kenneth E.

1995-01-01

Preliminary results of shearographic inspections of the shuttle external tank (ET) spray-on foam insulation (SOFI) and solid rocket booster (SRB) Marshall sprayable ablative (MSA-2) epoxy-cork thermal protection systems (TPS) are presented. Debonding SOFI or MSA-2 damage the orbiter 'belly' tile and exposes the ET/SRB to thermal loading. Previous work with the ET/SRB showed promising results with shearography. The first area investigated was the jack pad close-out, one of many areas on the ET where foam is applied at KSC. Voids 0.375 inch were detected in 1.75 inch thick foam using a pressure reduction of less than 0.4 psi. Of primary interest are areas of the ET that directly face the orbiter tile TPS. It is estimated that 90% of tile TPS damage on the orbiter 'belly' results from debonding SOFI during ascent. Test panels modeling these areas were manufactured with programmed debonds to determine the sensitivity of shearography as a function of debond size, SOFI thickness and vacuum. Results show repeatable detection of debonds with a diameter approximately half the SOFI thickness at less than 0.4 psi pressure reduction. Preliminary results are also presented on inspections of MSA-2 and the remote manipulator system (RMS) honeycomb material.

Shearographic non-destructive evaluation of the Space Shuttle

NASA Technical Reports Server (NTRS)

Davis, Christopher K.; Tenbusch, Kenneth E.; Hooker, Jeffery A.; Simmons, Stephen M.

1995-01-01

Preliminary results of shearographic inspections of the shuttle external tank (ET) spray-on foam insulation (SOFI) and solid rocket booster (SRB) Marshall sprayable ablative (MSA-2) epoxy-cork thermal protection systems (TPS) and remote manipulator system (RMS) honeycomb are presented. Debonding SOFI or MSA-2 damage the orbiter belly tile and exposes the ET/SRB to thermal loading. Previous work with the ET/SRB showed promising results with shearography. The first area investigated was the jack pad close-out, one of many areas on the ET where foam is applied at KSC. Voids 0.375 inch were detected in 1.75 inch thick foam using a pressure reduction of less dm 0.4 psi. Of primary interest are areas of the ET that directly face the orbiter tile TPS. It is estimated that 90% of tile TPS damage on the orbiter 'belly' results from debonding SOFI during ascent. Test panels modeling these areas were manufactured with programmed debonds to determine the sensitivity of shearography as a function of debond size, SOFI thickness, and vacuum. Results show a Probability of Detection (POD) of .95 or better for of debonds with a diameter equal to the SOFI thickness at less than 0.4 psi pressure reduction. Preliminary results are also presented on inspections of MSA-2 and the remote manipulator system (RMS) honeycomb material.

Shearographic non-destructive evaluation of space shuttle thermal protection systems

NASA Technical Reports Server (NTRS)

Hooker, Jeffrey A.; Simmons, Stephen M.; Davis, Christopher K.; Tenbusch, Kenneth E.

1995-01-01

Preliminary results of shearographic inspections of the shuttle external tank (ET) spray-on foam insulation (SOFI) and solid rocket booster (SRB) Marshall sprayable ablative (MSA-2) epoxy-cork thermal protection systems (TPS) are presented. Debonding SOFI or MSA-2 damage the orbiter 'belly' tile and exposes the ET/SRB to thermal loading. Previous work with the ET/SRB showed promising results with shearography. The first area investigated was the jack pad close-out, one of many areas on the ET where foam is applied at KSC. Voids 0.375 inch were detected in 1.75 inch thick foam using a pressure reduction of less than 0.4 psi. Of primary interest are areas of the ET that directly face the orbiter tile TPS. It is estimated that 90% of tile TPS damage on the orbiter 'belly' results from debonding SOFI during ascent. Test panels modeling these areas were manufactured with programmed debonds to determine the sensitivity of shearography as a function of debond size, SOFI thickness and vacuum. Results show repeatable detection of debonds with a diameter approximately half the SOFI thickness at less than 0.4 psi pressure reduction. Preliminary results are also presented on inspections of MSA-2 and the remote manipulator system (RMS) honeycomb material

Orbital debris research at NASA Johnson Space Center, 1986-1988

NASA Technical Reports Server (NTRS)

Reynolds, Robert C.; Potter, Andrew E., Jr.

1989-01-01

Research on orbital debris has intensified in recent years as the number of debris objects in orbit has grown. The population of small debris has now reached the level that orbital debris has become an important design factor for the Space Station. The most active center of research in this field has been the NASA Lyndon B. Johnson Space Center. Work is being done on the measurement of orbital debris, development of models of the debris population, and development of improved shielding against hypervelocity impacts. Significant advances have been made in these areas. The purpose of this document is to summarize these results and provide references for further study.

Generation and reduction of the data for the Ulysses gravitational wave experiment

NASA Technical Reports Server (NTRS)

Agresti, R.; Bonifazi, P.; Iess, L.; Trager, G. B.

1987-01-01

A procedure for the generation and reduction of the radiometric data known as REGRES is described. The software is implemented on a HP-1000F computer and was tested on REGRES data relative to the Voyager I spacecraft. The REGRES data are a current output of NASA's Orbit Determination Program. The software package was developed in view of the data analysis of the gravitational wave experiment planned for the European spacecraft Ulysses.

Benefits Derived From Laser Ranging Measurements for Orbit Determination of the GPS Satellite Orbit

NASA Technical Reports Server (NTRS)

Welch, Bryan W.

2007-01-01

While navigation systems for the determination of the orbit of the Global Position System (GPS) have proven to be very effective, the current research is examining methods to lower the error in the GPS satellite ephemerides below their current level. Two GPS satellites that are currently in orbit carry retro-reflectors onboard. One notion to reduce the error in the satellite ephemerides is to utilize the retro-reflectors via laser ranging measurements taken from multiple Earth ground stations. Analysis has been performed to determine the level of reduction in the semi-major axis covariance of the GPS satellites, when laser ranging measurements are supplemented to the radiometric station keeping, which the satellites undergo. Six ground tracking systems are studied to estimate the performance of the satellite. The first system is the baseline current system approach which provides pseudo-range and integrated Doppler measurements from six ground stations. The remaining five ground tracking systems utilize all measurements from the current system and laser ranging measurements from the additional ground stations utilized within those systems. Station locations for the additional ground sites were taken from a listing of laser ranging ground stations from the International Laser Ranging Service. Results show reductions in state covariance estimates when utilizing laser ranging measurements to solve for the satellite s position component of the state vector. Results also show dependency on the number of ground stations providing laser ranging measurements, orientation of the satellite to the ground stations, and the initial covariance of the satellite's state vector.

Effects of Intracranial Trochlear Neurectomy on the Structure of the Primate Superior Oblique Muscle

PubMed Central

Poukens, Vadims; Ying, Howard; Shan, Xiaoyan; Tian, Jing; Zee, David S.

2010-01-01

Purpose. Although cyclovertical strabismus in humans is frequently attributed to superior oblique (SO) palsy, anatomic effects of SO denervation have not been studied. Magnetic resonance imaging (MRI) and orbital histology was used to study the effects of acute trochlear (CN4) denervation on the monkey SO. Methods. Five juvenile macaque monkeys were perfused with formalin for 5 weeks: 15 months after unilateral or bilateral 10-mm intracranial trochlear neurectomy. Denervated and fellow orbits were imaged by MRI, embedded whole in paraffin, serially sectioned at 10-μm thickness, and stained with Masson trichrome. Whole muscle and individual fiber cross sections were quantified in SO muscles throughout the orbit and traced larger fibers in one specimen where they were present. Results. MRI demonstrated marked reduction in midorbital cross section in denervated SO muscles, with anterior shift of SO mass preserving overall volume. Muscle fibers exhibited variable atrophy along their lengths. Denervated orbital layer (OL) fiber cross sections were slightly but significantly reduced from control at most anteroposterior locations, but this reduction was much more profound in global layer (GL) fibers. Intraorbital and intramuscular CN4 were uniformly fibrotic. In one animal, there were scattered clusters of markedly hypertrophic GL fibers that exhibited only sparse myomyous junctions only anteriorly. Conclusions. CN4 denervation produces predominantly SO GL atrophy with relative OL sparing. Overall midorbital SO atrophy was evident by MRI as early as 5 weeks after denervation, as denervated SO volume shifted anteriorly. Occasional GL fiber hypertrophy suggests that at least some SO fibers extend essentially the full muscle length after trochlear neurectomy. PMID:20164458

Operational Data Reduction Procedure for Determining Density and Vertical Structure of the Martian Upper Atmosphere from Mars Global Surveyor Accelerometer Measurements

NASA Technical Reports Server (NTRS)

Cancro, George J.; Tolson, Robert H.; Keating, Gerald M.

1998-01-01

The success of aerobraking by the Mars Global Surveyor (MGS) spacecraft was partly due to the analysis of MGS accelerometer data. Accelerometer data was used to determine the effect of the atmosphere on each orbit, to characterize the nature of the atmosphere, and to predict the atmosphere for future orbits. To interpret the accelerometer data, a data reduction procedure was developed to produce density estimations utilizing inputs from the spacecraft, the Navigation Team, and pre-mission aerothermodynamic studies. This data reduction procedure was based on the calculation of aerodynamic forces from the accelerometer data by considering acceleration due to gravity gradient, solar pressure, angular motion of the MGS, instrument bias, thruster activity, and a vibration component due to the motion of the damaged solar array. Methods were developed to calculate all of the acceleration components including a 4 degree of freedom dynamics model used to gain a greater understanding of the damaged solar array. The total error inherent to the data reduction procedure was calculated as a function of altitude and density considering contributions from ephemeris errors, errors in force coefficient, and instrument errors due to bias and digitization. Comparing the results from this procedure to the data of other MGS Teams has demonstrated that this procedure can quickly and accurately describe the density and vertical structure of the Martian upper atmosphere.

Digitization and reduction of old astronomical plates of natural satellites

NASA Astrophysics Data System (ADS)

Yan, D.; Qiao, R. C.; Dourneau, G.; Yu, Y.; Zhang, H. Y.; Cheng, X.; Xi, X. J.

2016-04-01

Old astrophotographic plates are precious sources of historical data for astronomical studies, especially regarding the improvement of natural satellite orbits. Today, with the advent of new, accurate techniques, these old data can be re-processed so as to give positions that are much more accurate than those initially obtained. Various recent projects, including our Chinese project, have involved measuring and reducing these old plates again. Here we present a method for measurement and reduction that involves the digitization of plates using an advanced commercial scanner, namely the EPSON 10000 XL. We selected a set of 27 plates of the satellites of Jupiter, Saturn and Uranus taken from 1987 to 1990. A total of 125 satellite positions were derived from the new measurement and reduction of these plates using the UCAC4 catalogue. A comparison of the new observed positions with recent ephemerides has shown a general consistency with satellite theory of about 100 mas. The new positions present an accuracy equivalent to the most recent CCD observations, and better than the original positions. Moreover, nearly 30 per cent of the 125 positions obtained in this work are published for the first time here. This paper is a preliminary contribution to the larger project of new measurements and reductions of all the old Chinese plates of natural satellites, which should allow further improvements in the knowledge of the orbits of these satellites.

Generation of coherent spin-wave modes in yttrium iron garnet microdiscs by spin–orbit torque

PubMed Central

Collet, M.; de Milly, X.; d'Allivy Kelly, O.; Naletov, V. V.; Bernard, R.; Bortolotti, P.; Ben Youssef, J.; Demidov, V. E.; Demokritov, S. O.; Prieto, J. L.; Muñoz, M.; Cros, V.; Anane, A.; de Loubens, G.; Klein, O.

2016-01-01

In recent years, spin–orbit effects have been widely used to produce and detect spin currents in spintronic devices. The peculiar symmetry of the spin Hall effect allows creation of a spin accumulation at the interface between a metal with strong spin–orbit interaction and a magnetic insulator, which can lead to a net pure spin current flowing from the metal into the insulator. This spin current applies a torque on the magnetization, which can eventually be driven into steady motion. Tailoring this experiment on extended films has proven to be elusive, probably due to mode competition. This requires the reduction of both the thickness and lateral size to reach full damping compensation. Here we show clear evidence of coherent spin–orbit torque-induced auto-oscillation in micron-sized yttrium iron garnet discs of thickness 20 nm. Our results emphasize the key role of quasi-degenerate spin-wave modes, which increase the threshold current. PMID:26815737

The N2O activation by Rh5 clusters. A quantum chemistry study.

PubMed

Olvera-Neria, Oscar; Avilés, Roberto; Francisco-Rodríguez, Héctor; Bertin, Virineya; García-Cruz, Raúl; González-Torres, Julio César; Poulain, Enrique

2015-04-01

Nitrous oxide (N2O) is a by-product of exhaust pipe gases treatment produced by motor vehicles. Therefore, the N2O reduction to N2 is necessary to meet the actual environmental legislation. The N2O adsorption and dissociation assisted by the square-based pyramidal Rh5 cluster was investigated using the density functional theory and the zero-order regular approximation (ZORA). The Rh5 sextet ground state is the most active in N2O dissociation, though the quartet and octet states are also active because they are degenerate. The Rh5 cluster spontaneously activates the N2─O cleavage, and the reaction is highly exothermic ca. -75 kcal mol(-1). The N2─O breaking is obtained for the geometrical arrangement that maximizes the overlap and electron transfers between the N2O and Rh5 frontier orbitals. The Rh5 high activity is due to the Rh 3d orbitals are located between the N2O HOMO and LUMO orbitals, which makes possible the interactions between them. In particular, the O 2p states strongly interact with Rh 3d orbitals, which finally weaken the N2─O bond. The electron transfer is from the Rh5 HOMO orbital to the N2O antibonding orbital.

SCF-Xα-SW electron densities with the overlapping sphere approximation

NASA Astrophysics Data System (ADS)

McMaster, Blair N.; Smith, Vedene H., Jr.; Salahub, Dennis R.

Self consistent field-Xα-scattered wave (SCF-Xα-SW) calculations have been performed for a series of eight first and second row homonuclear diatomic molecules using both the touching (TS) and 25 per cent overlapping sphere (OS) versions. The OS deformation density maps exhibit much better quantitative agreement with those from other Xα methods, which do not employ the spherical muffin-tin (MT) potential approximation, than do the TS maps. The OS version thus compensates very effectively for the errors involved in the MT approximation in computing electron densities. A detailed comparison between the TS- and OS-Xα-SW orbitals reveals that the reasons for this improvement are surprisingly specific. The dominant effect of the OS approximation is to increase substantially the electron density near the midpoint of bonding σ orbitals, with a consequent reduction of the density behind the atoms. A similar effect occurs for the bonding π orbitals but is less pronounced. These effects are due to a change in hybridization of the orbitals, with the OS approximation increasing the proportion of the subdominant partial waves and hence changing the shapes of the orbitals. It is this increased orbital polarization which so effectively compensates for the lack of (non-spherically symmetric) polarization components in the MT potential, when overlapping spheres are used.

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

DOE PAGES

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo; ...

2017-08-02

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. In this study, we show that inelastic scattering spectroscopy using high-energy x-ray photonsmore » (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO 4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.« less

Visualizing redox orbitals and their potentials in advanced lithium-ion battery materials using high-resolution x-ray Compton scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hafiz, Hasnain; Suzuki, Kosuke; Barbiellini, Bernardo

Reduction-oxidation (redox) reactions are the key processes that underlie the batteries powering smartphones, laptops, and electric cars. A redox process involves transfer of electrons between two species. For example, in a lithium-ion battery, current is generated when conduction electrons from the lithium anode are transferred to the redox orbitals of the cathode material. The ability to visualize or image the redox orbitals and how these orbitals evolve under lithiation and delithiation processes is thus of great fundamental and practical interest for understanding the workings of battery materials. In this study, we show that inelastic scattering spectroscopy using high-energy x-ray photonsmore » (Compton scattering) can yield faithful momentum space images of the redox orbitals by considering lithium iron phosphate (LiFePO 4 or LFP) as an exemplar cathode battery material. Our analysis reveals a new link between voltage and the localization of transition metal 3d orbitals and provides insight into the puzzling mechanism of potential shift and how it is connected to the modification of the bond between the transition metal and oxygen atoms. Our study thus opens a novel spectroscopic pathway for improving the performance of battery materials.« less

Orbit/launch vehicle tradeoff studies. Earth Observatory Satellite system definition study (EOS)

NASA Technical Reports Server (NTRS)

1974-01-01

An evaluation of the Earth Observatory Satellite (EOS) design, performance, and cost factors which affect the choices of an orbit and a launch vehicle is presented. Primary emphasis is given to low altitude (300 to 900 nautical miles) land resources management applications for which payload design factors are defined. The subjects considered are: (1) a mission model, (2) orbit analysis and characterization, (3) characteristics and capabilities of candidate conventional launch vehicles, and space shuttle support. Recommendations are submitted for the EOS-A mission, the Single Multispectral Scanner payload, the Single Multispectral Scanner plus Thematic Mapper payload, the Dual Multispectral Scanner payload, and the Dual Multispectral Scanner plus Thematic Mapper payload.

Payload/orbiter contamination control requirement study, volume 1, exhibit A

NASA Technical Reports Server (NTRS)

Bareiss, L. E.; Hooper, V. W.; Rantanen, R. O.; Ress, E. B.

1974-01-01

This study is to identify and quantify the expected molecular and particulate on orbit contaminant environment for selected shuttle payloads as a result of major spacelab and shuttle orbiter contaminant sources. This investigation reviews individual payload susceptibilities to contamination, identifies the combined induced environment, identifies the risk of spacelab/payload critical surface(s) degradation, and provides preliminary contamination recommendations. It also establishes limiting factors which may depend upon operational activities associated with the payloads, spacelab, and the shuttle orbiter interface or upon independent payload functional activities.

Orbits of Two-Body Problem From the Lenz Vector

ERIC Educational Resources Information Center

Caplan, S.; And Others

1978-01-01

Obtains the orbits with reference to the center of mass of two bodies under mutual universe square law interaction by use of the eccentricity vector which is equivalent to the Lenz vector within a numerical factor. (Author/SL)

[Interactions of fibroblasts, adipocytes and immunocompeent cells in the pathogenesis of endocrine ophthalmopathy].

PubMed

Heufelder, A E

2001-01-01

Graves' ophthalmopathy is thought to result from a complex interplay of genetic and environmental factors. Various genes including those coding for HLA may determine a patient's susceptibility to the disease and its severity, but in addition numerous and often unknown environmental factors may determine its course. The orbital immune process is thought to be initiated, on the background of a permissive immunogenetic milieu, by circulating T cells directed against certain antigens on thyroid follicular cells that also recognize antigenic epitopes which are shared by tissues contained in the orbital space. Analysis of variable region genes of T cell antigen receptors in orbital T cells of patients with active Graves' ophthalmopathy has revealed limited variability of TcR V gene usage, suggesting that antigen-driven selection and/or expansion of specific T cells may occur during the early stages of Graves' ophthalmopathy. T cell recruitment into the orbital tissues is facilitated by certain chemokines and cytokines, which attract T cells by stimulating the expression of several adhesion molecules (e.g. ICAM-1, VCAM-1, CD44) in vascular endothelium and connective tissue cells. Adhesion molecules are known to be important for a variety of interactions between immunocompetent cells, preadipocyte fibroblasts and adipocytes. In addition, these molecules play a central role in lymphocyte activation and localization, facilitating antigen recognition, T cell costimulation, and various effector-target cell functions at the inflammatory sites, which result in amplification of the cellular immune process in active Graves' ophthalmopathy. T cells and macrophages populate the orbital space and release a number of cytokines (most likely a Th-1-type spectrum) into the surrounding tissues. Cytokines, oxygen free radicals and fibrogenic growth factors, released both from infiltrating inflammatory and residential cells, act upon orbital preadipocytes in a paracrine and autocrine manner to stimulate adipogenesis, fibroblast proliferation, glycosaminoglycan synthesis, and the expression of immunomodulatory molecules. Smoking, a well-known aggravating factor in Graves' ophthalmopathy, may aggravate tissue hypoxia and exert important immunomodulatory and pro-oxidant effects. Differentiation of orbital preadipocyte fibroblasts into mature adipocytes expressing increased levels of TSHR may also be driven by stimulation with circulating or locally produced cytokines or effectors. TSHR-directed autoantibodies or T cells may thus play a direct role promoting adipogenesis, glycosaminoglycan synthesis and expression of immunomodulatory proteins within the orbits. Once the net effect of these changes has come to increase the volume of the fatty connective tissues within the orbit, then proptosis, extraocular muscle dysfunction, and periorbital congestion will ensue.

Accounting of fundamental components of the rotation parameters of the Earth in the formation of a high-accuracy orbit of navigation satellites

NASA Astrophysics Data System (ADS)

Markov, Yu. G.; Mikhailov, M. V.; Pochukaev, V. N.

2012-07-01

An analysis of perturbing factors influencing the motion of a navigation satellite (NS) is carried out, and the degree of influence of each factor on the GLONASS orbit is estimated. It is found that fundamental components of the Earth's rotation parameters (ERP) are one substantial factor commensurable with maximum perturbations. Algorithms for the calculation of orbital perturbations caused by these parameters are given; these algorithms can be implemented in a consumer's equipment. The daily prediction of NS coordinates is performed on the basis of real GLONASS satellite ephemerides transmitted to a consumer, using the developed prediction algorithms taking the ERP into account. The obtained accuracy of the daily prediction of GLONASS ephemerides exceeds by tens of times the accuracy of the daily prediction performed using algorithms recommended in interface control documents.

Analysis of Orbital Lifetime Prediction Parameters in Preparation for Post-Mission Disposal

NASA Astrophysics Data System (ADS)

Choi, Ha-Yeon; Kim, Hae-Dong; Seong, Jae-Dong

2015-12-01

Atmospheric drag force is an important source of perturbation of Low Earth Orbit (LEO) orbit satellites, and solar activity is a major factor for changes in atmospheric density. In particular, the orbital lifetime of a satellite varies with changes in solar activity, so care must be taken in predicting the remaining orbital lifetime during preparation for post-mission disposal. In this paper, the System Tool Kit (STK®) Long-term Orbit Propagator is used to analyze the changes in orbital lifetime predictions with respect to solar activity. In addition, the STK® Lifetime tool is used to analyze the change in orbital lifetime with respect to solar flux data generation, which is needed for the orbital lifetime calculation, and its control on the drag coefficient control. Analysis showed that the application of the most recent solar flux file within the Lifetime tool gives a predicted trend that is closest to the actual orbit. We also examine the effect of the drag coefficient, by performing a comparative analysis between varying and constant coefficients in terms of solar activity intensities.

Launch Vehicle Propulsion Design with Multiple Selection Criteria

NASA Technical Reports Server (NTRS)

Shelton, Joey D.; Frederick, Robert A.; Wilhite, Alan W.

2005-01-01

The approach and techniques described herein define an optimization and evaluation approach for a liquid hydrogen/liquid oxygen single-stage-to-orbit system. The method uses Monte Carlo simulations, genetic algorithm solvers, a propulsion thermo-chemical code, power series regression curves for historical data, and statistical models in order to optimize a vehicle system. The system, including parameters for engine chamber pressure, area ratio, and oxidizer/fuel ratio, was modeled and optimized to determine the best design for seven separate design weight and cost cases by varying design and technology parameters. Significant model results show that a 53% increase in Design, Development, Test and Evaluation cost results in a 67% reduction in Gross Liftoff Weight. Other key findings show the sensitivity of propulsion parameters, technology factors, and cost factors and how these parameters differ when cost and weight are optimized separately. Each of the three key propulsion parameters; chamber pressure, area ratio, and oxidizer/fuel ratio, are optimized in the seven design cases and results are plotted to show impacts to engine mass and overall vehicle mass.

Task-Driven Orbit Design and Implementation on a Robotic C-Arm System for Cone-Beam CT.

PubMed

Ouadah, S; Jacobson, M; Stayman, J W; Ehtiati, T; Weiss, C; Siewerdsen, J H

2017-03-01

This work applies task-driven optimization to the design of non-circular orbits that maximize imaging performance for a particular imaging task. First implementation of task-driven imaging on a clinical robotic C-arm system is demonstrated, and a framework for orbit calculation is described and evaluated. We implemented a task-driven imaging framework to optimize orbit parameters that maximize detectability index d '. This framework utilizes a specified Fourier domain task function and an analytical model for system spatial resolution and noise. Two experiments were conducted to test the framework. First, a simple task was considered consisting of frequencies lying entirely on the f z -axis (e.g., discrimination of structures oriented parallel to the central axial plane), and a "circle + arc" orbit was incorporated into the framework as a means to improve sampling of these frequencies, and thereby increase task-based detectability. The orbit was implemented on a robotic C-arm (Artis Zeego, Siemens Healthcare). A second task considered visualization of a cochlear implant simulated within a head phantom, with spatial frequency response emphasizing high-frequency content in the ( f y , f z ) plane of the cochlea. An optimal orbit was computed using the task-driven framework, and the resulting image was compared to that for a circular orbit. For the f z -axis task, the circle + arc orbit was shown to increase d ' by a factor of 1.20, with an improvement of 0.71 mm in a 3D edge-spread measurement for edges located far from the central plane and a decrease in streak artifacts compared to a circular orbit. For the cochlear implant task, the resulting orbit favored complementary views of high tilt angles in a 360° orbit, and d ' was increased by a factor of 1.83. This work shows that a prospective definition of imaging task can be used to optimize source-detector orbit and improve imaging performance. The method was implemented for execution of non-circular, task-driven orbits on a clinical robotic C-arm system. The framework is sufficiently general to include both acquisition parameters (e.g., orbit, kV, and mA selection) and reconstruction parameters (e.g., a spatially varying regularizer).

Task-driven orbit design and implementation on a robotic C-arm system for cone-beam CT

NASA Astrophysics Data System (ADS)

Ouadah, S.; Jacobson, M.; Stayman, J. W.; Ehtiati, T.; Weiss, C.; Siewerdsen, J. H.

2017-03-01

Purpose: This work applies task-driven optimization to the design of non-circular orbits that maximize imaging performance for a particular imaging task. First implementation of task-driven imaging on a clinical robotic C-arm system is demonstrated, and a framework for orbit calculation is described and evaluated. Methods: We implemented a task-driven imaging framework to optimize orbit parameters that maximize detectability index d'. This framework utilizes a specified Fourier domain task function and an analytical model for system spatial resolution and noise. Two experiments were conducted to test the framework. First, a simple task was considered consisting of frequencies lying entirely on the fz-axis (e.g., discrimination of structures oriented parallel to the central axial plane), and a "circle + arc" orbit was incorporated into the framework as a means to improve sampling of these frequencies, and thereby increase task-based detectability. The orbit was implemented on a robotic C-arm (Artis Zeego, Siemens Healthcare). A second task considered visualization of a cochlear implant simulated within a head phantom, with spatial frequency response emphasizing high-frequency content in the (fy, fz) plane of the cochlea. An optimal orbit was computed using the task-driven framework, and the resulting image was compared to that for a circular orbit. Results: For the fz-axis task, the circle + arc orbit was shown to increase d' by a factor of 1.20, with an improvement of 0.71 mm in a 3D edge-spread measurement for edges located far from the central plane and a decrease in streak artifacts compared to a circular orbit. For the cochlear implant task, the resulting orbit favored complementary views of high tilt angles in a 360° orbit, and d' was increased by a factor of 1.83. Conclusions: This work shows that a prospective definition of imaging task can be used to optimize source-detector orbit and improve imaging performance. The method was implemented for execution of non-circular, task-driven orbits on a clinical robotic C-arm system. The framework is sufficiently general to include both acquisition parameters (e.g., orbit, kV, and mA selection) and reconstruction parameters (e.g., a spatially varying regularizer).

Research and Development, Technology Requirements, and Use of Existing Space Assets

NASA Technical Reports Server (NTRS)

Grey, Jerry; Rowell, Larry

1999-01-01

Technology requirements are addressed in three categories: (1) Passenger-carrying STS(s); (2) orbital facilities (including on-orbit operations such as servicing) and human factors (crew and passenger training and recreation, on-orbit environmental control, etc.); and (3) ground infrastructure. An example tourism trip scenario is used in discussing possible targets for technology development activities. Some general comments are made as are considerations for other working groups.

On-Orbit Noise Characterization for MODIS Reflective Solar Bands

NASA Technical Reports Server (NTRS)

Xiong, X.; Xie, X.; Angal, A.

2008-01-01

Since launch, the Moderate Resolution Imaging Spectroradiometer (MODIS) has operated successfully on-board the NASA Earth Observing System (EOS) Terra and EOS Aqua spacecraft. MODIS is a passive cross-track scanning radiometer that makes observations in 36 spectral bands with spectral wavelengths from visible (VIS) to long-wave infrared. MODIS bands 1-19 and 26 are the reflective solar bands (RSB) with wavelengths from 0.41 to 2.2 micrometers. They are calibrated on-orbit using an on-board solar diffuser (SD) and a SD stability monitor (SDSM) system. For MODIS RSB, the level 1B calibration algorithm produces top of the atmosphere reflectance factors and radiances for every pixel of the Earth view. The sensor radiometric calibration accuracy, specified at each spectral band's typical scene radiance, is 2% for the RSB reflectance factors and 5% for the RSB radiances. Also specified at the typical scene radiance is the detector signal-to-noise ratio (SNR), a key sensor performance parameter that directly impacts its radiometric calibration accuracy and stability, as well as the image quality. This paper describes an on-orbit SNR characterization approach developed to evaluate and track MODIS RSB detector performance. In order to perform on-orbit SNR characterization, MODIS RSB detector responses to the solar illumination reflected from the SD panel must be corrected for factors due to variations of the solar angles and the SD bi-directional reflectance factor. This approach enables RSB SNR characterization to be performed at different response levels for each detector. On-orbit results show that both Terra and Aqua MODIS RSB detectors have performed well since launch. Except for a few noisy or inoperable detectors which were identified pre-launch, most RSB detectors continue to meet the SNR design requirements and are able to maintain satisfactory short-term stability. A comparison of on-orbit noise characterization results with results derived from pre-launch calibration and characterization are also provided.

Three Orbital Burns to Molniya Orbit Via Shuttle_Centaur G Upper Stage

NASA Technical Reports Server (NTRS)

Williams, Craig H.

2015-01-01

An unclassified analytical trajectory design, performance, and mission study was done for the 1982 to 1986 joint National Aeronautics and Space Administration (NASA)-United States Air Force (USAF) Shuttle/Centaur G upper stage development program to send performance-demanding payloads to high orbits such as Molniya using an unconventional orbit transfer. This optimized three orbital burn transfer to Molniya orbit was compared to the then-baselined two burn transfer. The results of the three dimensional trajectory optimization performed include powered phase steering data and coast phase orbital element data. Time derivatives of the orbital elements as functions of thrust components were evaluated and used to explain the optimization's solution. Vehicle performance as a function of parking orbit inclination was given. Performance and orbital element data was provided for launch windows as functions of launch time. Ground track data was given for all burns and coasts including variation within the launch window. It was found that a Centaur with fully loaded propellant tanks could be flown from a 37 deg inclination low Earth parking orbit and achieve Molniya orbit with comparable performance to the baselined transfer which started from a 57 deg inclined orbit: 9,545 versus 9,552 lb of separated spacecraft weight, respectively. There was a significant reduction in the need for propellant launch time reserve for a 1 hr window: only 78 lb for the three burn transfer versus 320 lb for the two burn transfer. Conversely, this also meant that longer launch windows over more orbital revolutions could be done for the same amount of propellant reserve. There was no practical difference in ground tracking station or airborne assets needed to secure telemetric data, even though the geometric locations of the burns varied considerably. There was a significant adverse increase in total mission elapsed time for the three versus two burn transfer (12 vs. 1-1/4 hr), but could be accommodated by modest modifications to Centaur systems. Future applications were discussed. The three burn transfer was found to be a viable, arguably preferable, alternative to the two burn transfer.

Three Orbital Burns to Molniya Orbit via Shuttle Centaur G Upper Stage

NASA Technical Reports Server (NTRS)

Williams, Craig H.

2014-01-01

An unclassified analytical trajectory design, performance, and mission study was done for the 1982-86 joint NASA-USAF Shuttle/Centaur G upper stage development program to send performance-demanding payloads to high orbits such as Molniya using an unconventional orbit transfer. This optimized three orbital burn transfer to Molniya orbit was compared to the then-baselined two burn transfer. The results of the three dimensional trajectory optimization performed include powered phase steering data and coast phase orbital element data. Time derivatives of the orbital elements as functions of thrust components were evaluated and used to explain the optimization's solution. Vehicle performance as a function of parking orbit inclination was given. Performance and orbital element data was provided for launch windows as functions of launch time. Ground track data was given for all burns and coasts including variation within the launch window. It was found that a Centaur with fully loaded propellant tanks could be flown from a 37deg inclination low Earth parking orbit and achieve Molniya orbit with comparable performance to the baselined transfer which started from a 57deg inclined orbit: 9,545 lb vs. 9,552 lb of separated spacecraft weight respectively. There was a significant reduction in the need for propellant launch time reserve for a one hour window: only 78 lb for the three burn transfer vs. 320 lb for the two burn transfer. Conversely, this also meant that longer launch windows over more orbital revolutions could be done for the same amount of propellant reserve. There was no practical difference in ground tracking station or airborne assets needed to secure telemetric data, even though the geometric locations of the burns varied considerably. There was a significant adverse increase in total mission elapsed time for the three vs. two burn transfer (12 vs. 11/4 hrs), but could be accommodated by modest modifications to Centaur systems. Future applications were discussed. The three burn transfer was found to be a viable, arguably preferable, alternative to the two burn transfer.

Precession and atmospheric CO2 modulated variability of sea ice in the central Okhotsk Sea since 130,000 years ago

NASA Astrophysics Data System (ADS)

Lo, Li; Belt, Simon T.; Lattaud, Julie; Friedrich, Tobias; Zeeden, Christian; Schouten, Stefan; Smik, Lukas; Timmermann, Axel; Cabedo-Sanz, Patricia; Huang, Jyh-Jaan; Zhou, Liping; Ou, Tsong-Hua; Chang, Yuan-Pin; Wang, Liang-Chi; Chou, Yu-Min; Shen, Chuan-Chou; Chen, Min-Te; Wei, Kuo-Yen; Song, Sheng-Rong; Fang, Tien-Hsi; Gorbarenko, Sergey A.; Wang, Wei-Lung; Lee, Teh-Quei; Elderfield, Henry; Hodell, David A.

2018-04-01

Recent reduction in high-latitude sea ice extent demonstrates that sea ice is highly sensitive to external and internal radiative forcings. In order to better understand sea ice system responses to external orbital forcing and internal oscillations on orbital timescales, here we reconstruct changes in sea ice extent and summer sea surface temperature (SSST) over the past 130,000 yrs in the central Okhotsk Sea. We applied novel organic geochemical proxies of sea ice (IP25), SSST (TEX86L) and open water marine productivity (a tri-unsaturated highly branched isoprenoid and biogenic opal) to marine sediment core MD01-2414 (53°11.77‧N, 149°34.80‧E, water depth 1123 m). To complement the proxy data, we also carried out transient Earth system model simulations and sensitivity tests to identify contributions of different climatic forcing factors. Our results show that the central Okhotsk Sea was ice-free during Marine Isotope Stage (MIS) 5e and the early-mid Holocene, but experienced variable sea ice cover during MIS 2-4, consistent with intervals of relatively high and low SSST, respectively. Our data also show that the sea ice extent was governed by precession-dominated insolation changes during intervals of atmospheric CO2 concentrations ranging from 190 to 260 ppm. However, the proxy record and the model simulation data show that the central Okhotsk Sea was near ice-free regardless of insolation forcing throughout the penultimate interglacial, and during the Holocene, when atmospheric CO2 was above ∼260 ppm. Past sea ice conditions in the central Okhotsk Sea were therefore strongly modulated by both orbital-driven insolation and CO2-induced radiative forcing during the past glacial/interglacial cycle.

Hydrogen maser clocks in space for solid-Earth research and time-transfer applications: Experiment overview and evaluation of Russian miniature sapphire loaded cavity

NASA Astrophysics Data System (ADS)

Busca, G.; Bernier, L. G.; Silvestrin, P.; Feltham, S.; Gaygerov, B. A.; Tatarenkov, V. M.

1994-05-01

The Observatoire Cantonal de Neuchatel (ON) is developing for ESTEC a compact H-maser for space use based upon a miniature sapphire loaded microwave cavity, a technique pioneered at VNIIFTRI. Various contacts between West-European parties, headed by ESA, and the Russian parties, headed by ESA, led to the proposal for flying two H-masers on Meteor 3M, a Russian meteorology satellite in low polar orbit. The experiment will include two masers, one provided by ON and the other by VNIIFTRI. T/F transfer and precise positioning will be performed by both a microwave link, using PRARE equipment, and an optical link, using LASSO-like equipment. The main objectives of the experiment are precise orbit determination and point positioning for geodetic/geophysical research, ultra-accurate time comparison and dissemination as well as in-orbit demonstration of operation and performance of H-masers. Within the scope of a preliminary space H-maser development phase performed for ESTEC at ON in preparation to the joint experiment, a Russian miniature sapphire loaded microwave cavity, on loan from VNIIFTRI, was evaluated in a full-size EFOS hydrogen maser built by ON. The experimental evaluation confirmed the theoretical expectation that with a hydrogen storage volume of only 0.65 liter an atomic quality factor of 1.5 x 10(exp 9) can be obtained for a -105 dBm output power. This represents a theoretical Allan deviation of 1.7 x 10(exp -15) averaged on a 1000 s time interval. From a full-size design to a compact one, therefore, the sacrifice in performance due to the reduction of the storage volume is very small.

Hydrogen maser clocks in space for solid-Earth research and time-transfer applications: Experiment overview and evaluation of Russian miniature sapphire loaded cavity

NASA Technical Reports Server (NTRS)

Busca, G.; Bernier, L. G.; Silvestrin, P.; Feltham, S.; Gaygerov, B. A.; Tatarenkov, V. M.

1994-01-01

The Observatoire Cantonal de Neuchatel (ON) is developing for ESTEC a compact H-maser for space use based upon a miniature sapphire loaded microwave cavity, a technique pioneered at VNIIFTRI. Various contacts between West-European parties, headed by ESA, and the Russian parties, headed by ESA, led to the proposal for flying two H-masers on Meteor 3M, a Russian meteorology satellite in low polar orbit. The experiment will include two masers, one provided by ON and the other by VNIIFTRI. T/F transfer and precise positioning will be performed by both a microwave link, using PRARE equipment, and an optical link, using LASSO-like equipment. The main objectives of the experiment are precise orbit determination and point positioning for geodetic/geophysical research, ultra-accurate time comparison and dissemination as well as in-orbit demonstration of operation and performance of H-masers. Within the scope of a preliminary space H-maser development phase performed for ESTEC at ON in preparation to the joint experiment, a Russian miniature sapphire loaded microwave cavity, on loan from VNIIFTRI, was evaluated in a full-size EFOS hydrogen maser built by ON. The experimental evaluation confirmed the theoretical expectation that with a hydrogen storage volume of only 0.65 liter an atomic quality factor of 1.5 x 10(exp 9) can be obtained for a -105 dBm output power. This represents a theoretical Allan deviation of 1.7 x 10(exp -15) averaged on a 1000 s time interval. From a full-size design to a compact one, therefore, the sacrifice in performance due to the reduction of the storage volume is very small.

Systems Engineering Approach to Technology Integration for NASA's 2nd Generation Reusable Launch Vehicle

NASA Technical Reports Server (NTRS)

Thomas, Dale; Smith, Charles; Thomas, Leann; Kittredge, Sheryl

2002-01-01

The overall goal of the 2nd Generation RLV Program is to substantially reduce technical and business risks associated with developing a new class of reusable launch vehicles. NASA's specific goals are to improve the safety of a 2nd-generation system by 2 orders of magnitude - equivalent to a crew risk of 1-in-10,000 missions - and decrease the cost tenfold, to approximately $1,000 per pound of payload launched. Architecture definition is being conducted in parallel with the maturating of key technologies specifically identified to improve safety and reliability, while reducing operational costs. An architecture broadly includes an Earth-to-orbit reusable launch vehicle, on-orbit transfer vehicles and upper stages, mission planning, ground and flight operations, and support infrastructure, both on the ground and in orbit. The systems engineering approach ensures that the technologies developed - such as lightweight structures, long-life rocket engines, reliable crew escape, and robust thermal protection systems - will synergistically integrate into the optimum vehicle. To best direct technology development decisions, analytical models are employed to accurately predict the benefits of each technology toward potential space transportation architectures as well as the risks associated with each technology. Rigorous systems analysis provides the foundation for assessing progress toward safety and cost goals. The systems engineering review process factors in comprehensive budget estimates, detailed project schedules, and business and performance plans, against the goals of safety, reliability, and cost, in addition to overall technical feasibility. This approach forms the basis for investment decisions in the 2nd Generation RLV Program's risk-reduction activities. Through this process, NASA will continually refine its specialized needs and identify where Defense and commercial requirements overlap those of civil missions.

Systems Engineering Approach to Technology Integration for NASA's 2nd Generation Reusable Launch Vehicle

NASA Technical Reports Server (NTRS)

Thomas, Dale; Smith, Charles; Thomas, Leann; Kittredge, Sheryl

2002-01-01

The overall goal of the 2nd Generation RLV Program is to substantially reduce technical and business risks associated with developing a new class of reusable launch vehicles. NASA's specific goals are to improve the safety of a 2nd generation system by 2 orders of magnitude - equivalent to a crew risk of 1-in-10,000 missions - and decrease the cost tenfold, to approximately $1,000 per pound of payload launched. Architecture definition is being conducted in parallel with the maturating of key technologies specifically identified to improve safety and reliability, while reducing operational costs. An architecture broadly includes an Earth-to-orbit reusable launch vehicle, on-orbit transfer vehicles and upper stages, mission planning, ground and flight operations, and support infrastructure, both on the ground and in orbit. The systems engineering approach ensures that the technologies developed - such as lightweight structures, long-life rocket engines, reliable crew escape, and robust thermal protection systems - will synergistically integrate into the optimum vehicle. To best direct technology development decisions, analytical models are employed to accurately predict the benefits of each technology toward potential space transportation architectures as well as the risks associated with each technology. Rigorous systems analysis provides the foundation for assessing progress toward safety and cost goals. The systems engineering review process factors in comprehensive budget estimates, detailed project schedules, and business and performance plans, against the goals of safety, reliability, and cost, in addition to overall technical feasibility. This approach forms the basis for investment decisions in the 2nd Generation RLV Program's risk-reduction activities. Through this process, NASA will continually refine its specialized needs and identify where Defense and commercial requirements overlap those of civil missions.

Advanced Electric Propulsion for Space Solar Power Satellites

NASA Technical Reports Server (NTRS)

Oleson, Steve

1999-01-01

The sun tower concept of collecting solar energy in space and beaming it down for commercial use will require very affordable in-space as well as earth-to-orbit transportation. Advanced electric propulsion using a 200 kW power and propulsion system added to the sun tower nodes can provide a factor of two reduction in the required number of launch vehicles when compared to in-space cryogenic chemical systems. In addition, the total time required to launch and deliver the complete sun tower system is of the same order of magnitude using high power electric propulsion or cryogenic chemical propulsion: around one year. Advanced electric propulsion can also be used to minimize the stationkeeping propulsion system mass for this unique space platform. 50 to 100 kW class Hall, ion, magnetoplasmadynamic, and pulsed inductive thrusters are compared. High power Hall thruster technology provides the best mix of launches saved and shortest ground to Geosynchronous Earth Orbital Environment (GEO) delivery time of all the systems, including chemical. More detailed studies comparing launch vehicle costs, transfer operations costs, and propulsion system costs and complexities must be made to down-select a technology. The concept of adding electric propulsion to the sun tower nodes was compared to a concept using re-useable electric propulsion tugs for Low Earth Orbital Environment (LEO) to GEO transfer. While the tug concept would reduce the total number of required propulsion systems, more launchers and notably longer LEO to GEO and complete sun tower ground to GEO times would be required. The tugs would also need more complex, longer life propulsion systems and the ability to dock with sun tower nodes.

Updated Heliostorm Warning Mission: Enhancements Based on New Technology

NASA Technical Reports Server (NTRS)

Young, Roy M.

2007-01-01

The Heliostorm (also referred to as Geostorm) mission has been regarded as the best choice for the first application of solar sail technology. The objective of Heliostorm is to obtain data from an orbit station slightly displaced from the ecliptic at or nearer to the Sun than 0.98 AU, which places it twice as close to the sun as Earth's natural L1 point at 0.993 AU. The maintenance of such an orbit location would require prohibitive amounts of propellants using chemical or electric propulsion systems; however, a solar sailcraft is ideally suited for this purpose because it relies solely on the propulsive force from photons for orbit maintenance. Heliostorm has been the subject of several mission studies over the past decade, with the most complete study conducted in 1999 in conjunction with a proposed New Millennium Program (NMP) Space Technology 5 (ST-5) flight opportunity. Recently, over a two and one-half year period dating from 2003 through 2005, NASA's In-Space Propulsion Technology Program (ISTP) matured solar sail technology from laboratory components to full systems, demonstrated in as relevant a space environment as could feasibly be simulated on the ground. Work under this program has yielded promising results for enhanced Heliostorm mission performance. This enhanced performance is achievable principally through reductions in the sail areal density. These reductions are realized through the use of lower linear mass density booms, a thinner sail membrane, and increased sail area. Advancements in sailcraft vehicle system design also offer potential mass reductions and hence improved performance. This paper will present the preliminary results of an updated Heliostorm mission design study including the enhancements incorporated during the design, development, analysis and testing of the system ground demonstrator.

Updated Heliostorm Warning Mission: Enhancements Based on New Technology

NASA Technical Reports Server (NTRS)

Young, Roy M.

2007-01-01

The Heliostorm (also referred to as Geostorm) mission has been regarded as the best choice for the first application of solar sail technology. The objective of Heliostorm is to obtain data from an orbit station slightly displaced from the ecliptic at or nearer to the Sun than 0.98 AU, which places it twice as dose to the sun as Earth's natural L1 point at 0.993 AU. The maintenance of such an orbit location would require prohibitive amounts of propellants using chemical or electric propulsion systems; however, a solar sailcraft is ideally suited for this purpose because it relies solely on the propulsive force from photons for orbit maintenance. Heliostorm has been the subject of several mission studies over the past decade, with the most complete study conducted in 1999 in conjunction with a proposed New Millennium Program (NMP) Space Technology 5 (ST-5) flight opportunity. Recently, over a two and one-half year period dating from 2003 through 2005, NASA's In-Space Propulsion Technology Program (ISTP) matured solar sail technology from laboratory components to full systems, demonstrated in as relevant a space environment as could feasibly be simulated on the ground. Work under this program has yielded promising results for enhanced Heliostorm mission performance. This enhanced performance is achievable principally through reductions in the sail areal density. These reductions are realized through the use of lower linear mass density booms, a thinner sail membrane, and increased sail area. Advancements in sailcraft vehicle system design also offer potential mass reductions and hence improved performance. This paper will present the preliminary results of an updated Heliostorm mission design study including the enhancements incorporated during the design, development, analysis and testing of the system ground demonstrator.

Effective orbital volume and eyeball position: an MRI study.

PubMed

Detorakis, Efstathios T; Drakonaki, Eleni; Papadaki, Efrosini; Pallikaris, Ioannis G; Tsilimbaris, Miltiadis K

2010-10-01

Previous studies have examined factors affecting the position of the eyeball to the orbit. This study examined the role of effective orbital volume (EOV), defined as the difference between orbital and eyeball volume, as a determinant of eyeball position, using MRI scans. Forty-six patients were recruited from the Department of Ophthalmology of the University Hospital of Heraklion, Crete Greece. Patients with a history of orbital disease were excluded. Distances between eyeball poles and orbital landmarks were measured in T1 weighted transverse, sagittal and coronal orbital images. The protrusion of the eyeball in the sagittal and transverse planes was recorded. The volume of the eyeball and bony orbit, the EOV, the volume of the extraocular muscles as well as clinical information (age, gender, Hertel exophthalmometry) were also recorded. EOV was significantly associated with orbital volume but not with eyeball volume. EOV was also significantly associated with transverse and sagittal globe protrusions. Females displayed significantly lower orbital and eyeball volumes as well as EOV than males but higher transverse globe protrusion than males. Variations in EOV are associated with orbital volume rather than with eyeball volume. EOV is associated with globe protrusion and may be taken into account in the planning of various procedures, including orbital decompression, treatment of enophthalmos or the size of orbital implants following enucleation.

Chaotic dynamics outside Saturn’s main rings: The case of Atlas

NASA Astrophysics Data System (ADS)

Renner, Stéfan; Cooper, Nicholas J.; El Moutamid, Maryame; Evans, Mike W.; Murray, Carl D.; Sicardy, Bruno

2014-11-01

We revisit in detail the dynamics of Atlas. From a fit to new Cassini ISS astrometric observations spanning February 2004 to August 2013, we estimate GM_Atlas=0.384+/-0.001 x 10^(-3)km^3s^(-2), a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. Our numerically-derived orbit shows that Atlas is currently librating in both a 54:53 corotation eccentricity resonance (CER) and a 54:53 Lindblad eccentricity resonance (LER) with Prometheus. We demonstrate that the orbit of Atlas is chaotic, with a Lyapunov time of order 10 years, as a direct consequence of the coupled resonant interaction (CER/LER) with Prometheus. The interactions between the two resonances is investigated using the CoraLin analytical model (El Moutamid et al., 2014), showing that the chaotic zone fills almost all the corotation site occupied by the satellite’s orbit. Four 70 :67 apse-type mean motion resonances with Pandora are also overlapping, but these resonances have a much weaker effect on Atlas.We estimate the capture probabilities of Atlas into resonances with Prometheus as the orbits expand through tidal effects, and discuss the implications for the orbital evolution.

Subperiosteal orbital abscess: volumetric criteria for surgical drainage.

PubMed

Tabarino, Florian; Elmaleh-Bergès, Monique; Quesnel, Stéphanie; Lorrot, Mathie; Van Den Abbeele, Thierry; Teissier, Natacha

2015-02-01

To investigate predictive factors of surgical management of subperiosteal orbital abscess in children. A retrospective monocentric study was conducted between 2000 and 2011 with children hospitalized for acute pediatric orbital cellulitis (APOC). Clinical, biological and radiological data as well as medical and surgical management were collected and analyzed. All patients received intravenous antibiotics and underwent a CT-scan. Orbit and subperiosteal intraorbital abscess dimensions were measured on axial and coronal planes and the abscess volume was calculated using a spheroid model. Eighty-three children with APOC (mean age: 4.5 years) were included, 53 were boys (63.9%). Thirty-two children (38.6%) presented with a subperiosteal orbital abscess. Mean abscess volume was 570mm(3) and mean exophthalmos was 4.7mm. Twenty patients were treated surgically, 11 of which by an endoscopic approach. A positive correlation was observed between the volume of the abscess or exophthalmos and surgical drainage: 57.9% of patients underwent surgery when exophthalmos was >4mm, 29.4% between 2 and 4mm, and none when <2mm. All patients with an abscess volume >500mm(3) or >5% of orbital volume were operated on whereas only 30% or 39% of patients, respectively, in case of smaller volumes (P<0.05). Surgery for subperiosteal orbital abscess is usually performed in case of visual complications or unfavorable medical outcome. The importance of the exophthalmos and the volume of the abscess measured on the CT-scan are predictive factors of surgery in children with subperiosteal orbital abscess without visual complications. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Orbital cellulitis: clinical course and management challenges. the Lagos State University Teaching Hospital experience.

PubMed

Balogun, Bolanle G; Balogun, Modupe M; Adekoya, Bola J

2012-01-01

Orbital cellulitis is a devastating acute infection of orbital soft tissues located posterior to the orbital septum. It is both vision and life-threatening. It is an ocular emergency which most often present in childhood. This article reviewed cases presenting during the study period with the view of examining the pattern of presentation, clinical course and management challenges. A retrospective study was conducted on patients presenting with orbital cellulitis between January 2008 and June 2011. Socio-demographic data, entry and discharge visual acuity, presenting complaints, predisposing factors, duration of complaints, admission period and complications were extracted from clinical records and analyzed. Seventeen (17) patients presented with orbital cellulitis constituting 6.2% of ocular emergency admissions during the study period. Twelve (70.6%) were males. Thirteen (76.5%) were children. The major predisposing factors were upper respiratory tract infections, and facial and globe injuries in five (22.7%) cases respectively. Only five (29.4%), presented within three days of disease onset. Average duration of admission was 10.6 days. Complications during the course of disease were category 4 and 5 blindness in five (23.5%), orbital abscess four (23.5%), cavernous sinus thrombosis two (11.8%), contralateral preseptal cellulitis two (11.8%) and exposure keratopathy in one (5.9%). Orbital cellulitis has remained a disease with high ocular morbidity. The major management challenges were poor financial status of patients precluding necessary diagnostic laboratory and imaging studies. Early recognition, diagnosis and treatment are crucial to the preservation of vision and reduced occurrence of complications. The importance of record keeping is also highlighted.

Advanced transportation concept for round-trip space travel

NASA Technical Reports Server (NTRS)

Yen, Chen-Wan L.

1988-01-01

A departure from the conventional concept of round-trip space travel is introduced. It is shown that a substantial reduction in the initial load required of the Shuttle or other launch vehicle can be achieved by staging the ascent orbit and leaving fuel for the return trip at each stage of the orbit. Examples of round trips from a low-inclination LEO to a high-inclination LEO and from an LEO to a GEO are used to show the merits of the new concept. Potential problem areas and research needed for the development of an efficient space transportation network are discussed.

Dimensionality-Driven Metal-Insulator Transition in Spin-Orbit-Coupled SrIrO3

NASA Astrophysics Data System (ADS)

Schütz, P.; Di Sante, D.; Dudy, L.; Gabel, J.; Stübinger, M.; Kamp, M.; Huang, Y.; Capone, M.; Husanu, M.-A.; Strocov, V. N.; Sangiovanni, G.; Sing, M.; Claessen, R.

2017-12-01

Upon reduction of the film thickness we observe a metal-insulator transition in epitaxially stabilized, spin-orbit-coupled SrIrO3 ultrathin films. By comparison of the experimental electronic dispersions with density functional theory at various levels of complexity we identify the leading microscopic mechanisms, i.e., a dimensionality-induced readjustment of octahedral rotations, magnetism, and electronic correlations. The astonishing resemblance of the band structure in the two-dimensional limit to that of bulk Sr2 IrO4 opens new avenues to unconventional superconductivity by "clean" electron doping through electric field gating.

Management of periorbital basal cell carcinoma with orbital invasion.

PubMed

Sun, Michelle T; Wu, Albert; Figueira, Edwin; Huilgol, Shyamala; Selva, Dinesh

2015-11-01

Basal cell carcinoma (BCC) is the most common eyelid malignancy; however, orbital invasion by periocular BCC is rare, and management remains challenging. Established risk factors for orbital invasion by BCC include male gender, advanced age, medial canthal location, previous recurrences, large tumor size, aggressive histologic subtype and perineural invasion. Management requires a multidisciplinary approach with orbital exenteration remaining the treatment of choice. Globe-sparing treatment may be appropriate in selected patients and radiotherapy and chemotherapy are often used as adjuvant therapies for advanced or inoperable cases, although the evidence remains limited. We aim to summarize the presentation and treatment of BCC with orbital invasion to better guide the management of this complex condition.

High Power Microwave Emission of Large and Small Orbit Gyrotron Devices in Rectangular Interaction Structures

NASA Astrophysics Data System (ADS)

Hochman, J. M.; Gilgenbach, R. M.; Jaynes, R. L.; Rintamaki, J. I.; Luginsland, J. W.; Lau, Y. Y.; Spencer, T. A.

1996-11-01

Experiments utilize large and small orbit e-beam gyrotron devices in a rectangular-cross-section (RCS) gyrotron. This device is being explored to examine polarization control. Other research issues include pulse shortening, and mode competition. MELBA generates electron beams with parameters of: -800kV, 1-10kA diode current, and 0.5-1.0 μ sec pulselengths. The small orbit gyrotron device is converted to a large orbit experiment by running MELBA's annular electron beam through a magnetic cusp. Initial experiments showed an increase in beam alpha (V_perp/V_par) of a factor of ~ 4 between small and large orbit devices. Experimental results from the RCS gyrotron will be compared for large-orbit and small-orbit electron beams. Beam transport data and frequency measurements will be presented. Computer modeling utilizing the MAGIC and E-gun codes will be shown.

Detectability of Martian carbonates from orbit using thermal neutrons

NASA Technical Reports Server (NTRS)

Feldman, W. C.; Jakosky, B. M.

1991-01-01

Numerical simulations of Martian neutron leakage flux spectra are made in order to explore the detectability of magnesium and calcium carbonate deposits using neutron spectroscopic techniques from orbit. The primary signature of such deposits is found to be an enhanced thermal amplitude. Although this enhancement is weakened by: (1) partial burial beneath an aeolian regolith blanket; (2) admixture with regolith on a microscopic (centimeter) or macroscopic (tens of centimeters) scale; and (3) reduction in the areal size of the deposit, near-surface stratigraphies of carbonates hypothesized by some authors as possible on Mars are still detectable by simple neutron sensors from orbit. However, the large variations in the magnitude of the thermal neutron enhancements caused by different carbonate deposit configurations found in this study require a combined gamma ray and neutron analysis for their unique specification.

Spectroscopic Binary Star Studies with the Palomar Testbed Interferometer II

NASA Astrophysics Data System (ADS)

Boden, A. F.; Lane, B. F.; Creech-Eakman, M.; Queloz, D.; PTI Collaboration

1999-12-01

The Palomar Testbed Interferometer (PTI) is a long-baseline near-infrared interferometer located at Palomar Observatory. Following our previous work on resolving spectroscopic binary stars with the Palomar Testbed Interferometer (PTI), we will present a number of new visual and physical orbit determinations derived from integrated reductions of PTI visibility and archival radial velocity data. The six systems for which we will present new orbit models are: 12 Boo (HD 123999), 75 Cnc (HD 78418), 47 And (HD 8374), HD 205539, BY Draconis (HDE 234677), and 3 Boo (HD 120064). Most of these systems are double-lined binary systems (SB2), and integrated astrometric/radial velocity orbit modeling provides precise fundamental parameters (mass, luminosity) and system distance determinations comparable with Hipparcos precisions. The work described in this paper was performed under contract with the National Aeronautics and Space Administration.

An Induced Environment Contamination Monitor for the Space Shuttle

NASA Technical Reports Server (NTRS)

Miller, E. R. (Editor); Decher, R. (Editor)

1978-01-01

The Induced Environment Contamination Monitor (IECM), a set of ten instruments integrated into a self-contained unit and scheduled to fly on shuttle Orbital Flight Tests 1 through 6 and on Spacelabs 1 and 2, is described. The IECM is designed to measure the actual environment to determine whether the strict controls placed on the shuttle system have solved the contamination problem. Measurements are taken during prelaunch, ascent, on-orbit, descent, and postlanding. The on-orbit measurements are molecular return flux, background spectral intensity, molecular deposition, and optical surface effects. During the other mission phases dew point, humidity, aerosol content, and trace gas are measured as well as optical surface effects and molecular deposition. The IECM systems and thermal design are discussed. Preflight and ground operations are presented together with associated ground support equipment. Flight operations and data reduction plans are given.

Human factors in space station architecture 1: Space station program implications for human factors research

NASA Technical Reports Server (NTRS)

Cohen, M. M.

1985-01-01

The space station program is based on a set of premises on mission requirements and the operational capabilities of the space shuttle. These premises will influence the human behavioral factors and conditions on board the space station. These include: launch in the STS Orbiter payload bay, orbital characteristics, power supply, microgravity environment, autonomy from the ground, crew make-up and organization, distributed command control, safety, and logistics resupply. The most immediate design impacts of these premises will be upon the architectural organization and internal environment of the space station.

Super-reduced polyoxometalates: excellent molecular cluster battery components and semipermeable molecular capacitors.

PubMed

Nishimoto, Yoshio; Yokogawa, Daisuke; Yoshikawa, Hirofumi; Awaga, Kunio; Irle, Stephan

2014-06-25

Theoretical investigations are presented on the molecular and electronic structure changes that occur as α-Keggin-type polyoxometalate (POM(3-)) clusters [PM12O40](3-) (M = Mo, W) are converted toward their super-reduced POM(27-) state during the discharging process in lithium-based molecular cluster batteries. Density functional theory was employed in geometry optimization, and first-principles molecular dynamics simulations were used to explore local minima on the potential energy surface of neutral POM clusters adorned with randomly placed Li atoms as electron donors around the cluster surface. On the basis of structural, electron density, and molecular orbital studies, we present evidence that the super-reduction is accompanied by metal-metal bond formation, beginning from the 12th to 14th excess electron transferred to the cluster. Afterward, the number of metal-metal bonds increases nearly linearly with the number of additionally transferred excess electrons. In α-Keggin-type POMs, metal triangles are a prominently emerging structural feature. The origin of the metal triangle formation during super-reduction stems from the formation of characteristic three-center two-electron bonds in triangular metal atom sites, created under preservation of the POM skeleton via "squeezing out" of oxygen atoms bridging two metal atoms when the underlying metal atoms form covalent bonds. The driving force for this unusual geometrical and electronic structure change is a local Jahn-Teller distortion at individual transition-metal octahedral sites, where the triply degenerate t2 d orbitals become partially filled during reduction and gain energy by distortion of the octahedron in such a way that metal-metal bonds are formed. The bonding orbitals show strong contributions from mixing with metal-oxygen antibonding orbitals, thereby "shuffling away" excess electrons from the cluster center to the outside of the cage. The high density of negatively charged yet largely separated oxygen atoms on the surface of the super-reduced POM(27-) polyanion allows the huge Coulombic repulsion due to the presence of the excess electrons to be counterbalanced by the presence of Li countercations, which partially penetrate into the outer oxygen shell. This "semiporous molecular capacitor" structure is likely the reason for the effective electron uptake in POMs.

Green Propulsion Advancement and Infusion

NASA Technical Reports Server (NTRS)

Mulkey, Henry W.; Maynard, Andrew P.; Anflo, Kjell

2018-01-01

All space missions benefit from increased propulsion system performance, allowing lower spacecraft launch mass, larger scientific payloads, or extended on-orbit lifetimes. Likewise, long-term storable liquid propellant candidates that offer significant reduction in personnel hazards and shorter payload processing schedules present a more attractive propulsion subsystem solution to spacecraft builders. Aiming to reduce risk to potential infusion missions and fully comprehend the alternative propellant performance, the work presented herein represents many years of development and collaborative efforts to successfully align higher performance, low toxicity green propellants into NASA Goddard Space Flight Center (GSFC) missions. High Performance Green Propulsion (HPGP), and the associated propellant technology, has advanced significantly in maturity with increased familiarity with LMP-103S propellant handling, the proven reduction in loading hazards, successful launches conducted at multiple international Ranges, and HPGP on-orbit flight heritage. As science missions move forward to the potential infusion of HPGP technology, the National Aeronautics and Space Administration (NASA) and its partners are working to address gaps in system performance and operational considerations.

Giant onsite electronic entropy enhances the performance of ceria for water splitting

DOE PAGES

Naghavi, S. Shahab; Emery, Antoine A.; Hansen, Heine A.; ...

2017-08-18

Previous studies have shown that a large solid-state entropy of reduction increases the thermodynamic efficiency of metal oxides, such as ceria, for two-step thermochemical water splitting cycles. In this context, the configurational entropy arising from oxygen off-stoichiometry in the oxide, has been the focus of most previous work. Here we report a different source of entropy, the onsite electronic configurational entropy, arising from coupling between orbital and spin angular momenta in lanthanide f orbitals. We find that onsite electronic configurational entropy is sizable in all lanthanides, and reaches a maximum value of ≈4.7 k B per oxygen vacancy for Cemore » 4+/Ce 3+ reduction. This unique and large positive entropy source in ceria explains its excellent performance for high-temperature catalytic redox reactions such as water splitting. Our calculations also show that terbium dioxide has a high electronic entropy and thus could also be a potential candidate for solar thermochemical reactions.« less

Dose and scatter characteristics of a novel cone beam CT system for musculoskeletal extremities

NASA Astrophysics Data System (ADS)

Zbijewski, W.; Sisniega, A.; Vaquero, J. J.; Muhit, A.; Packard, N.; Senn, R.; Yang, D.; Yorkston, J.; Carrino, J. A.; Siewerdsen, J. H.

2012-03-01

A novel cone-beam CT (CBCT) system has been developed with promising capabilities for musculoskeletal imaging (e.g., weight-bearing extremities and combined radiographic / volumetric imaging). The prototype system demonstrates diagnostic-quality imaging performance, while the compact geometry and short scan orbit raise new considerations for scatter management and dose characterization that challenge conventional methods. The compact geometry leads to elevated, heterogeneous x-ray scatter distributions - even for small anatomical sites (e.g., knee or wrist), and the short scan orbit results in a non-uniform dose distribution. These complex dose and scatter distributions were investigated via experimental measurements and GPU-accelerated Monte Carlo (MC) simulation. The combination provided a powerful basis for characterizing dose distributions in patient-specific anatomy, investigating the benefits of an antiscatter grid, and examining distinct contributions of coherent and incoherent scatter in artifact correction. Measurements with a 16 cm CTDI phantom show that the dose from the short-scan orbit (0.09 mGy/mAs at isocenter) varies from 0.16 to 0.05 mGy/mAs at various locations on the periphery (all obtained at 80 kVp). MC estimation agreed with dose measurements within 10-15%. Dose distribution in patient-specific anatomy was computed with MC, confirming such heterogeneity and highlighting the elevated energy deposition in bone (factor of ~5-10) compared to soft-tissue. Scatter-to-primary ratio (SPR) up to ~1.5-2 was evident in some regions of the knee. A 10:1 antiscatter grid was found earlier to result in significant improvement in soft-tissue imaging performance without increase in dose. The results of MC simulations elucidated the mechanism behind scatter reduction in the presence of a grid. A ~3-fold reduction in average SPR was found in the MC simulations; however, a linear grid was found to impart additional heterogeneity in the scatter distribution, mainly due to the increase in the contribution of coherent scatter with increased spatial variation. Scatter correction using MC-generated scatter distributions demonstrated significant improvement in cupping and streaks. Physical experimentation combined with GPU-accelerated MC simulation provided a sophisticated, yet practical approach in identifying low-dose acquisition techniques, optimizing scatter correction methods, and evaluating patientspecific dose.

Orbital-optimized MP2.5 and its analytic gradients: Approaching CCSD(T) quality for noncovalent interactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bozkaya, Uğur, E-mail: ugur.bozkaya@atauni.edu.tr; Center for Computational Molecular Science and Technology, School of Chemistry and Biochemistry, and School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332; Sherrill, C. David

2014-11-28

Orbital-optimized MP2.5 [or simply “optimized MP2.5,” OMP2.5, for short] and its analytic energy gradients are presented. The cost of the presented method is as much as that of coupled-cluster singles and doubles (CCSD) [O(N{sup 6}) scaling] for energy computations. However, for analytic gradient computations the OMP2.5 method is only half as expensive as CCSD because there is no need to solve λ{sub 2}-amplitude equations for OMP2.5. The performance of the OMP2.5 method is compared with that of the standard second-order Møller–Plesset perturbation theory (MP2), MP2.5, CCSD, and coupled-cluster singles and doubles with perturbative triples (CCSD(T)) methods for equilibrium geometries, hydrogenmore » transfer reactions between radicals, and noncovalent interactions. For bond lengths of both closed and open-shell molecules, the OMP2.5 method improves upon MP2.5 and CCSD by 38%–43% and 31%–28%, respectively, with Dunning's cc-pCVQZ basis set. For complete basis set (CBS) predictions of hydrogen transfer reaction energies, the OMP2.5 method exhibits a substantially better performance than MP2.5, providing a mean absolute error of 1.1 kcal mol{sup −1}, which is more than 10 times lower than that of MP2.5 (11.8 kcal mol{sup −1}), and comparing to MP2 (14.6 kcal mol{sup −1}) there is a more than 12-fold reduction in errors. For noncovalent interaction energies (at CBS limits), the OMP2.5 method maintains the very good performance of MP2.5 for closed-shell systems, and for open-shell systems it significantly outperforms MP2.5 and CCSD, and approaches CCSD(T) quality. The MP2.5 errors decrease by a factor of 5 when the optimized orbitals are used for open-shell noncovalent interactions, and comparing to CCSD there is a more than 3-fold reduction in errors. Overall, the present application results indicate that the OMP2.5 method is very promising for open-shell noncovalent interactions and other chemical systems with difficult electronic structures.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaing, K. C.

It is shown that potato orbits in the near-axis region of a high beta tokamak are squeezed in a magnetic well. The squeezing factor is the same as that for the banana orbits derived in an earlier work [Phys. Plasmas 3, 2843 (1996)]. It depends on the energy of the particle. For high-energy particles, the size of the squeezed orbits is independent of their energy. This implies improved confinement for high-energy particles and for high beta tokamaks with advanced fuels.

Variance Reduction Factor of Nuclear Data for Integral Neutronics Parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiba, G., E-mail: go_chiba@eng.hokudai.ac.jp; Tsuji, M.; Narabayashi, T.

We propose a new quantity, a variance reduction factor, to identify nuclear data for which further improvements are required to reduce uncertainties of target integral neutronics parameters. Important energy ranges can be also identified with this variance reduction factor. Variance reduction factors are calculated for several integral neutronics parameters. The usefulness of the variance reduction factors is demonstrated.

Long arc orbit determination for Mariner 9 using combined radio and optical data types

NASA Technical Reports Server (NTRS)

Born, G. H.; Mohan, S. N.

1974-01-01

Results of postflight orbit determination for the Mariner 9 trajectory (Mariner-Mars 1971 mission) using Doppler data combined with optical data in the form of TV photographs of the natural satellites and Mars' surface features. It is shown that the combined data yield a solution which is a factor of 3 to 5 better than that obtained from Doppler-only solutions for the node of the orbit relative to the plane perpendicular to the Earth-Mars line. Consequently, these optical data types have a demonstrated potential to significantly improve planetary orbiter navigation accuracies.

Inhibiting thyrotropin/insulin-like growth factor 1 receptor crosstalk to treat Graves' ophthalmopathy: studies in orbital fibroblasts in vitro.

PubMed

Place, Robert F; Krieger, Christine C; Neumann, Susanne; Gershengorn, Marvin C

2017-02-01

Crosstalk between thyrotropin (TSH) receptors and insulin-like growth factor 1 (IGF-1) receptors initiated by activation of TSH receptors could be important in the development of Graves' ophthalmopathy (GO). Specifically, TSH receptor activation alone is sufficient to stimulate hyaluronic acid (HA) secretion, a major component of GO, through both IGF-1 receptor-dependent and -independent pathways. Although an anti-IGF-1 receptor antibody is in clinical trials, its effectiveness depends on the relative importance of IGF-1 versus TSH receptor signalling in GO pathogenesis. TSH and IGF-1 receptor antagonists were used to probe TSH/IGF-1 receptor crosstalk in primary cultures of Graves' orbital fibroblasts (GOFs) following activation with monoclonal TSH receptor antibody, M22. Inhibition of HA secretion following TSH receptor stimulation was measured by modified HA elisa. TSH receptor antagonist, ANTAG3 (NCGC00242364), inhibited both IGF-1 receptor -dependent and -independent pathways at all doses of M22; whereas IGF-1 receptor antagonists linsitinib and 1H7 (inhibitory antibody) lost efficacy at high M22 doses. Combining TSH and IGF-1 receptor antagonists exhibited Loewe additivity within the IGF-1 receptor-dependent component of the M22 concentration-response. Similar effects were observed in GOFs activated by autoantibodies from GO patients' sera. Our data support TSH and IGF-1 receptors as therapeutic targets for GO, but reveal putative conditions for anti-IGF-1 receptor resistance. Combination treatments antagonizing both receptors yield additive effects by inhibiting crosstalk triggered by TSH receptor stimulatory antibodies. Combination therapy may be an effective strategy for dose reduction and/or compensate for any loss of anti-IGF-1 receptor efficacy. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Inhibiting thyrotropin/insulin‐like growth factor 1 receptor crosstalk to treat Graves' ophthalmopathy: studies in orbital fibroblasts in vitro

PubMed Central

Place, Robert F; Neumann, Susanne; Gershengorn, Marvin C

2017-01-01

Background and Purpose Crosstalk between thyrotropin (TSH) receptors and insulin‐like growth factor 1 (IGF‐1) receptors initiated by activation of TSH receptors could be important in the development of Graves' ophthalmopathy (GO). Specifically, TSH receptor activation alone is sufficient to stimulate hyaluronic acid (HA) secretion, a major component of GO, through both IGF‐1 receptor‐dependent and ‐independent pathways. Although an anti‐IGF‐1 receptor antibody is in clinical trials, its effectiveness depends on the relative importance of IGF‐1 versus TSH receptor signalling in GO pathogenesis. Experimental Approach TSH and IGF‐1 receptor antagonists were used to probe TSH/IGF‐1 receptor crosstalk in primary cultures of Graves' orbital fibroblasts (GOFs) following activation with monoclonal TSH receptor antibody, M22. Inhibition of HA secretion following TSH receptor stimulation was measured by modified HA elisa. Key Results TSH receptor antagonist, ANTAG3 (NCGC00242364), inhibited both IGF‐1 receptor ‐dependent and ‐independent pathways at all doses of M22; whereas IGF‐1 receptor antagonists linsitinib and 1H7 (inhibitory antibody) lost efficacy at high M22 doses. Combining TSH and IGF‐1 receptor antagonists exhibited Loewe additivity within the IGF‐1 receptor‐dependent component of the M22 concentration‐response. Similar effects were observed in GOFs activated by autoantibodies from GO patients' sera. Conclusions and Implications Our data support TSH and IGF‐1 receptors as therapeutic targets for GO, but reveal putative conditions for anti‐IGF‐1 receptor resistance. Combination treatments antagonizing both receptors yield additive effects by inhibiting crosstalk triggered by TSH receptor stimulatory antibodies. Combination therapy may be an effective strategy for dose reduction and/or compensate for any loss of anti‐IGF‐1 receptor efficacy. PMID:27987211

THE INFLUENCE OF ORBITAL ECCENTRICITY ON TIDAL RADII OF STAR CLUSTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Webb, Jeremy J.; Harris, William E.; Sills, Alison

2013-02-20

We have performed N-body simulations of star clusters orbiting in a spherically symmetric smooth galactic potential. The model clusters cover a range of initial half-mass radii and orbital eccentricities in order to test the historical assumption that the tidal radius of a cluster is imposed at perigalacticon. The traditional assumption for globular clusters is that since the internal relaxation time is larger than its orbital period, the cluster is tidally stripped at perigalacticon. Instead, our simulations show that a cluster with an eccentric orbit does not need to fully relax in order to expand. After a perigalactic pass, a clustermore » recaptures previously unbound stars, and the tidal shock at perigalacticon has the effect of energizing inner region stars to larger orbits. Therefore, instead of the limiting radius being imposed at perigalacticon, it more nearly traces the instantaneous tidal radius of the cluster at any point in the orbit. We present a numerical correction factor to theoretical tidal radii calculated at perigalacticon which takes into consideration both the orbital eccentricity and current orbital phase of the cluster.« less

Advanced Space Propulsion

NASA Technical Reports Server (NTRS)

Frisbee, Robert H.

1996-01-01

This presentation describes a number of advanced space propulsion technologies with the potential for meeting the need for dramatic reductions in the cost of access to space, and the need for new propulsion capabilities to enable bold new space exploration (and, ultimately, space exploitation) missions of the 21st century. For example, current Earth-to-orbit (e.g., low Earth orbit, LEO) launch costs are extremely high (ca. $10,000/kg); a factor 25 reduction (to ca. $400/kg) will be needed to produce the dramatic increases in space activities in both the civilian and government sectors identified in the Commercial Space Transportation Study (CSTS). Similarly, in the area of space exploration, all of the relatively 'easy' missions (e.g., robotic flybys, inner solar system orbiters and landers; and piloted short-duration Lunar missions) have been done. Ambitious missions of the next century (e.g., robotic outer-planet orbiters/probes, landers, rovers, sample returns; and piloted long-duration Lunar and Mars missions) will require major improvements in propulsion capability. In some cases, advanced propulsion can enable a mission by making it faster or more affordable, and in some cases, by directly enabling the mission (e.g., interstellar missions). As a general rule, advanced propulsion systems are attractive because of their low operating costs (e.g., higher specific impulse, ISD) and typically show the most benefit for relatively 'big' missions (i.e., missions with large payloads or AV, or a large overall mission model). In part, this is due to the intrinsic size of the advanced systems as compared to state-of-the-art (SOTA) chemical propulsion systems. Also, advanced systems often have a large 'infrastructure' cost, either in the form of initial R&D costs or in facilities hardware costs (e.g., laser or microwave transmission ground stations for beamed energy propulsion). These costs must then be amortized over a large mission to be cost-competitive with a SOTA system with a low initial development and infrastructure cost and a high operating cost. Note however that this has resulted in a 'Catch 22' standoff between the need for large initial investment that is amortized over many launches to reduce costs, and the limited number of launches possible at today's launch costs. Some examples of missions enabled (either in cost or capability) by advanced propulsion include long-life station-keeping or micro-spacecraft applications using electric propulsion or BMDO-derived micro-thrusters, low-cost orbit raising (LEO to GEO or Lunar orbit) using electric propulsion, robotic planetary missions using aerobraking or electric propulsion, piloted Mars missions using aerobraking and/or propellant production from Martian resources, very fast (100-day round-trip) piloted Mars missions using fission or fusion propulsion, and, finally, interstellar missions using fusion, antimatter, or beamed energy. The NASA Advanced Propulsion Technology program at the Jet Propulsion Laboratory (JPL) is aimed at assessing the feasibility of a range of near-term to far term advanced propulsion technologies that have the potential to reduce costs and/or enable future space activities. The program includes cooperative modeling and research activities between JPL and various universities and industry; and directly supported independent research at universities and industry. The cooperative program consists of mission studies, research and development of ion engine technology using C60 (Buckminsterfullerene) propellant, and research and development of lithium-propellant Lorentz-force accelerator (LFA) engine technology. The university/industry-supported research includes modeling and proof-of-concept experiments in advanced, high-lsp, long-life electric propulsion, and in fusion propulsion.

Comparative economics of space resource utilization

NASA Technical Reports Server (NTRS)

Cutler, Andrew Hall

1991-01-01

Physical economic factors such as mass payback ratio, total payback ratio, and capital payback time are discussed and used to compare the economics of using resources from the Moon, Mars and its moons, and near Earth asteroids to serve certain near term markets such as propellant in low Earth orbit or launched mass reduction for lunar and Martian exploration. Methods for accounting for the time cost of money in simple figures of merit such as MPRs are explored and applied to comparisons such as those between lunar, Martian, and asteroidal resources. Methods for trading off capital and operating costs to compare schemes with substantially different capital to operating cost ratio are presented and discussed. Areas where further research or engineering would be extremely useful in reducing economic uncertainty are identified, as are areas where economic merit is highly sensitive to engineering performance - as well as areas where such sensitivity is surprisingly low.

Preliminary analysis of remote infrared imagery of shuttle during entry: An aerothermodynamic flight experiment

NASA Technical Reports Server (NTRS)

Swenson, B. L.; Edsinger, L. E.

1977-01-01

The preliminary feasibility of remote high-resolution infrared imagery of the space shuttle orbiter lower surface during entry to obtain accurate measurements of aerodynamic heat transfer to that vehicle was examined. In general, it was determined that such such images can be taken from an existing aircraft/telescope system (the C-141 AIRO) with a minimum modification or addition of systems using available technology. These images will have a spatial resolution of about 0.3 m and a temperature resolution much better than 2.5 percent. The data from these images will be at conditions and at a scale not reproducible in ground based facilities and should aid in the reduction of the prudent factors of safety required to account for phenomenological uncertainties on the thermal protection system design. Principal phenomena to be observed include laminar heating, boundary-layer transition, turbulent heating, surface catalysis, and flow separation and reattachment.

[Ultrastructure of the blood vessels and muscle fibers in the skeletal muscle of rats flown on the Kosmos-605 and Kosmos-782 biosatellites].

PubMed

Savik, Z F; Rokhlenko, K D

1981-01-01

Electron microscopy was used to study ultrastructures of the wall of blood vessels and muscle fibers of the red (soleus) and mixed (gastrocnemius) muscles of rats flown on Cosmos-605 for 22.5 days and on Cosmos-782 for 19,5 days and sacrificed 4-6 hours, 48 hours and 25-27 days postflight. It was demonstrated that the orbital flight did not induce significant changes in the ultrastructure of blood vessels of the soleus and gastrocnemius muscles but caused atrophy of muscle fibers and reduction of the number of functioning capillaries. Readaptation of the soleus vascular system to 1 g led to degradation of permeability of capillary and venular walls and development of edema of the perivascular connective tissue. This may be one of the factors responsible for dystrophic changes in muscle fibers.

Design feasibility via ascent optimality for next-generation spacecraft

NASA Astrophysics Data System (ADS)

Miele, A.; Mancuso, S.

This paper deals with the optimization of the ascent trajectories for single-stage-sub-orbit (SSSO), single-stage-to-orbit (SSTO), and two-stage-to-orbit (TSTO) rocket-powered spacecraft. The maximum payload weight problem is studied for different values of the engine specific impulse and spacecraft structural factor. The main conclusions are that: feasibility of SSSO spacecraft is guaranteed for all the parameter combinations considered; feasibility of SSTO spacecraft depends strongly on the parameter combination chosen; not only feasibility of TSTO spacecraft is guaranteed for all the parameter combinations considered, but the TSTO payload is several times the SSTO payload. Improvements in engine specific impulse and spacecraft structural factor are desirable and crucial for SSTO feasibility; indeed, aerodynamic improvements do not yield significant improvements in payload. For SSSO, SSTO, and TSTO spacecraft, simple engineering approximations are developed connecting the maximum payload weight to the engine specific impulse and spacecraft structural factor. With reference to the specific impulse/structural factor domain, these engineering approximations lead to the construction of zero-payload lines separating the feasibility region (positive payload) from the unfeasibility region (negative payload).

Ofeq-2 orbit, attitude, and flight evaluation

NASA Astrophysics Data System (ADS)

Grumer, Michael; Komem, Joseph; Kronenfeld, Joseph; Kubitski, Ophir; Lorber, Vitaly; Shyldkrot, Haim

1992-02-01

The most significant events and phenomena that occurred during the Ofeq-2 flight are evaluated in this work. Particular attention is paid to the physical and technological factors which affected its orbital lifetime. Comparison of Ofeq-2 telemetry results with prelaunch estimations and with Ofeq-1 flight data are presented. The satellite's orbit and mission characteristics are defined and the principal systems of Ofeq-2 are described. Topics addressed include the interaction between the spinner's attitude with respect to the sun and consequent electric power generation. The coning angle development history, the role of the solar data evaluation, and the factors influencing drag are also analyzed. All of these affected the Ofeq-2 power outage-recovery event. The orbit determination and the coning angle evolution estimation methods are discussed in some detail. A brief report on radiation effects on computer RAM (random access memory) is also given. An integrative systems engineering approach summary of the telemetry data reconstruction and analysis concludes the paper.

Periodicity in changes of Jupiter's hemispheres activity factor is continues to recover in 2018

NASA Astrophysics Data System (ADS)

Vidmachenko, A. P.

2018-05-01

From the mid-1990s to 2013 that there was a maximum mismatch between the time of Jupiter's passage at orbit at perihelion and aphelion, and the moments of minima and maxima of Solar activity. In 1963-1995 the correlation between the changes in factor AJ, Solar activity and the moments of passage of perihelion and aphelion of the orbit - was high, and the nature of the changes was synchronized. After 1995, inconsistency in the supply of Solar energy to northern and southern hemispheres of Jupiter and its movement in orbit - has become significant. But after 2014, the periodicity in the change of photometric characteristics of the northern and southern hemispheres of Jupiter, again becomes coordinated. And the data for 2017 and 2018 confirm the improvement of the matching of the course of the Aj(T) dependence, SA index and the regime irradiation by the Sun of Jupiter at it moves along the orbit.

Precise Orbit Determination of the GOCE Re-Entry Phase

NASA Astrophysics Data System (ADS)

Gini, Francesco; Otten, Michiel; Springer, Tim; Enderle, Werner; Lemmens, Stijn; Flohrer, Tim

2015-03-01

During the last days of the GOCE mission, after the GOCE spacecraft ran out of fuel, it slowly decayed before finally re-entering the atmosphere on the 11th November 2013. As an integrated part of the AOCS, GOCE carried a GPS receiver that was in operations during the re-entry phase. This feature provided a unique opportunity for Precise Orbit Determination (POD) analysis. As part of the activities carried out by the Navigation Support Office (HSO-GN) at ESOC, precise ephemerides of the GOCE satellite have been reconstructed for the entire re-entry phase based on the available GPS observations of the onboard LAGRANGE receiver. All the data available from the moment the thruster was switched off on the 21st of October 2013 to the last available telemetry downlink on the 10th November 2013 have been processed, for a total of 21 daily arcs. For this period a dedicated processing sequence has been defined and implemented within the ESA/ESOC NAvigation Package for Earth Observation Satellites (NAPEOS) software. The computed results show a post-fit RMS of the GPS undifferenced carrier phase residuals (ionospheric-free linear combination) between 6 and 14 mm for the first 16 days which then progressively increases up to about 80 mm for the last available days. An orbit comparison with the Precise Science Orbits (PSO) generated at the Astronomical Institute of the University of Bern (AIUB, Bern, Switzerland) shows an average difference around 9 cm for the first 8 daily arcs and progressively increasing up to 17 cm for the following days. During this reentry phase (21st of October - 10th November 2013) a substantial drop in the GOCE altitude is observed, starting from about 230 km to 130 km where the last GPS measurements were taken. During this orbital decay an increment of a factor of 100 in the aerodynamic acceleration profile is observed. In order to limit the mis-modelling of the non-gravitational forces (radiation pressure and aerodynamic effects) the newly developed software ARPA (Aerodynamics and Radiation Pressure Analysis) has been adopted to compute the forces acting on GOCE. An overview of the software techniques and the results of its implementation is presented in this paper. The use of the ARPA modelling leads to an average reduction of the carrier phase post-fit RMS of about 2 mm and decrement of the difference with the PSO orbits of more than 1 cm.

Fractionation of mercury isotopes by photo-oxidation in aquatic systems

NASA Astrophysics Data System (ADS)

Ghosh, S.; Bergquist, B. A.; Blum, J. D.

2009-12-01

Mercury is a globally distributed pollutant that bioaccumulates in aquatic food webs, even in remote locations. The recent discovery of both large mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) has made the promise of tracing this neurotoxin through the environment by using its isotopes very exciting. So far, the only process demonstrated experimentally to produce large MIF for Hg (similar in magnitude to the MIF observed in natural samples such as fish) is photochemical reduction (Bergquist and Blum, 2007). During photo-reduction, MIF of the odd isotopes was observed with the odd isotopes (199Hg, 201Hg) being preferentially enriched in the aqueous phase. Bergquist and Blum, 2007, suggested that the cause of MIF was the magnetic isotope effect (MIE), which is purely a kinetic phenomenon involving radical pair intermediates. Radical pairs with odd isotopes, which have non-zero nuclear spin and magnetic moments, can undergo spin conversion faster than radical pairs with non-magnetic even isotopes. This allows the odd and even isotopes to be preferentially enriched in different reaction products. MIE is a complex phenomenon that is dependent on several factors including hyperfine coupling, life-time of the radical pair, coupling strength of the radical pair, spin-orbital coupling, diffusion factors, and the solvent cage (space) in which the reaction occurs. Only under rare circumstances will all the factors be suitable for the expression of MIE in natural reactions. The goal of this study was to conduct aqueous photo-oxidation reactions to investigate whether this redox pathway expresses MIF (in the form of MIE) similar to the photo-reduction pathway. In natural systems, net photo-reduction of Hg (II) species results in the release of Hg(0) vapor to the atmosphere. However this net photo-reduction is a combination of both photo-reduction and photo-oxidation. In their experiments, Bergquist and Blum 2007, only investigated the aqueous photo-reduction pathway and suppressed the photo-oxidation reaction. Photochemical oxidation experiments of Hg(0) were performed in quartz reaction chambers using natural sunlight. Solutions of aqueous Hg(0) were prepared by continuously bubbling vapor Hg(0) generated by a gas-liquid separator into the quartz reaction chamber filled with water. Experiments were conducted in the presence of Cl- and other potential oxidants such as semiquinone, hydroxyl radicals and H2O2 to assess if the presence of these different oxidants showed significant differences in the expression of Hg isotopic fractionation during the photo-oxidation process. For experiments run in the presence of Cl- only, ~2% of Hg was oxidized at the end of 7 hours whereas in the presence of both semiquinone radical and Cl- , approximately 20% of Hg was oxidized at the end of 6 hours. In the experiment with hydroxyl radicals present, ~ 7% of Hg was oxidized at the end of 6.5 hours. Another set of experiments were conducted where the net photo-reduction was mimicked, which allowed both photo-oxidation and photo-reduction to occur. Isotopic results and their implications on the redox cycle of mercury obtained from these experiments will be discussed in detail.

Navigation of the Twin GRAIL Spacecraft into Science Formation at the Moon

NASA Technical Reports Server (NTRS)

Antreasian, P. G.; Bhat, R. S.; Criddle, K. E.; Goodson, T. D.; Hatch, S. J; Jefferson, D. C.; Lau, E. L.; Mohan, S.; Parker, J. S.; Roncoli, R. B.;

Traumatic globe luxation associated with orbital fracture in a child: a case report and literature review.

PubMed

Amaral, Márcio Bruno Figueiredo; Carvalho, Matheus Furtado; Ferreira, André Baptista; Mesquita, Ricardo Alves

2015-03-01

Orbital fracture associated with traumatic globe luxation is rare, as it generally requires trauma with high energy for this to occur. The present case report focused on a child who had been hit by a motorcycle, leading to a globe luxation of the left eye and fractures of the superolateral orbital walls. The patient presented initial cosmetic and psychological benefits from the repositioning of the intact globe and the reduction of the orbital fractures. However, a subsequent evisceration of the globe was required due to persistent proptosis and pain. An ocular prosthesis was also implanted, thus recovering the patient's aesthetics. Thirty-four well-documented cases of traumatic globe luxation could be found in the English literature since 1970. The mean age of patients presenting traumatic globe luxation was 29.5 years. The male gender proved to be more prevalent, with traffic collisions representing the most common accident etiology. Direct orbital trauma with fractures of medial and floor walls displacing the globe into the maxillary sinus represented the most common injury mechanism (38.2 %), followed by an elongated object entering the orbit (26.5 %). Optical nerve avulsion is the most serious complication seen in association with traumatic globe luxation, with the repositioning of the initial globe, with no enucleation or evisceration, representing the main form of management.

Four-qubit entanglement classification from string theory.

PubMed

Borsten, L; Dahanayake, D; Duff, M J; Marrani, A; Rubens, W

2010-09-03

We invoke the black-hole-qubit correspondence to derive the classification of four-qubit entanglement. The U-duality orbits resulting from timelike reduction of string theory from D=4 to D=3 yield 31 entanglement families, which reduce to nine up to permutation of the four qubits.

Spacecraft Autonomy and Automation: A Comparative Analysis of Strategies for Cost Effective Mission Operations

NASA Technical Reports Server (NTRS)

Wright, Nathaniel, Jr.

2000-01-01

The evolution of satellite operations over the last 40 years has drastically changed. October 4, 1957 (during the cold war) the Soviet Union launched the world's first spacecraft into orbit. The Sputnik satellite orbited Earth for three months and catapulted the United States into a race for dominance in space. A year after Sputnik, President Dwight Eisenhower formed the National Space and Aeronautics Administration (NASA). With a team of scientists and engineers, NASA successfully launched Explorer 1, the first US satellite to orbit Earth. During these early years, massive amounts of ground support equipment and operators were required to successfully operate spacecraft vehicles. Today, budget reductions and technological advances have forced new approaches to spacecraft operations. These approaches require increasingly complex, on board spacecraft systems, that enable autonomous operations, resulting in more cost-effective mission operations. NASA's Goddard Space Flight Center, considered world class in satellite development and operations, has developed and operated over 200 satellites during its 40 years of existence. NASA Goddard is adopting several new millennium initiatives that lower operational costs through the spacecraft autonomy and automation. This paper examines NASA's approach to spacecraft autonomy and ground system automation through a comparative analysis of satellite missions for Hubble Space Telescope-HST, Near Earth Asteroid Rendezvous-NEAR, and Solar Heliospheric Observatory-SoHO, with emphasis on cost reduction methods, risk analysis and anomalies and strategies employed for mitigating risk.

Periodic orbit analysis of a system with continuous symmetry—A tutorial

DOE Office of Scientific and Technical Information (OSTI.GOV)

Budanur, Nazmi Burak, E-mail: budanur3@gatech.edu; Cvitanović, Predrag; Borrero-Echeverry, Daniel

2015-07-15

Dynamical systems with translational or rotational symmetry arise frequently in studies of spatially extended physical systems, such as Navier-Stokes flows on periodic domains. In these cases, it is natural to express the state of the fluid in terms of a Fourier series truncated to a finite number of modes. Here, we study a 4-dimensional model with chaotic dynamics and SO(2) symmetry similar to those that appear in fluid dynamics problems. A crucial step in the analysis of such a system is symmetry reduction. We use the model to illustrate different symmetry-reduction techniques. The system's relative equilibria are conveniently determined bymore » rewriting the dynamics in terms of a symmetry-invariant polynomial basis. However, for the analysis of its chaotic dynamics, the “method of slices,” which is applicable to very high-dimensional problems, is preferable. We show that a Poincaré section taken on the 'slice' can be used to further reduce this flow to what is for all practical purposes a unimodal map. This enables us to systematically determine all relative periodic orbits and their symbolic dynamics up to any desired period. We then present cycle averaging formulas adequate for systems with continuous symmetry and use them to compute dynamical averages using relative periodic orbits. The convergence of such computations is discussed.« less

Drag-Free Performance of the ST7 Disturbance Reduction System Flight Experiment on the LISA Pathfinder

NASA Technical Reports Server (NTRS)

Maghami, Peiman; O'Donnell, James, Jr.; Hsu, Oscar; Ziemer, John; Dunn, Charles

2017-01-01

The Space Technology-7 Disturbance Reduction System (DRS) is an experiment package aboard the European Space Agency (ESA) LISA Pathfinder spacecraft. LISA Pathfinder launched from Kourou, French Guiana on December 3, 2015. The DRS is tasked to validate two specific technologies: colloidal micro-Newton thrusters (CMNT) to provide low-noise control capability of the spacecraft, and drag-free control flight. This validation is performed using highly sensitive drag-free sensors, which are provided by the LISA Technology Package of the European Space Agency. The Disturbance Reduction System is required to maintain the spacecrafts position with respect to a free-floating test mass to better than 10nmHz, along its sensitive axis (axis in optical metrology). It also has a goal of limiting the residual accelerations of any of the two test masses to below 30 (1 + [f3 mHz]) fmsHz, over the frequency range of 1 to 30 mHz.This paper briefly describes the design and the expected on-orbit performance of the control system for the two modes wherein the drag-free performance requirements are verified. The on-orbit performance of these modes are then compared to the requirements, as well as to the expected performance, and discussed.

The relationship of cranial, orbital and nasal cavity size with the morphology of the supraorbital region in modern Homo sapiens.

PubMed

Nowaczewska, Wioletta; Łapicka, Urszula; Cieślik, Agata; Biecek, Przemysław

2017-09-01

Morphological variation of the supraorbital region (SR) in human crania has been investigated and its potential sources suggested, along with the importance of the size of the facial skeleton, neurocranium, and orbit for the formation of this region. However, previous studies have not indicated whether facial size exhibits a stronger association with SR robusticity than neurocranial size or sex; moreover, the association between orbital volume and SR robusticity has been analysed only in non-human primate skulls. In this study we investigate whether the size of the facial skeleton, neurocranium, two measures of relative orbital size (orbital volume and estimated orbital aperture area), the relative size of the nasal cavity, and the relative estimated area of the anterior nasal cavity opening are related to SR robusticity; we also examine which of these analysed relationships is strongest, as well as independent of the influence of the other traits, in a geographically diverse modern human cranial sample. The results of Spearman's rank and partial rank correlations (encompassing models including or excluding sex and geographic origin) show a relationship between most of the above-mentioned variables and SR robusticity, with the exception of the estimated relative area of the orbital opening (in the case of the results of Spearman's rank correlations) and the traits of the nasal cavity. Of all the analysed traits, sex appears to be the most important for the formation of SR robusticity and, of two measures of cranial size, neurocranial size was the most significant. The strong relationship between SR robusticity and relative orbital volume was observed in models without the geographic origin factor. The results concerning analysed models suggest the influence of this factor on this relationship; however, to explain this influence, further studies are needed.

Positional dependence of the SNPP VIIRS SD BRDF degradation factor

NASA Astrophysics Data System (ADS)

Lei, Ning; Chen, Xuexia; Chang, Tiejun; Xiong, Xiaoxiong

2017-09-01

The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite is a passive scanning radiometer and an imager. The VIIRS regularly performs on-orbit radiometric calibration of its reflective solar bands (RSBs) through observing an onboard sunlit solar diffuser (SD). The reflectance of the SD changes over time and the change is denoted as the SD bidirectional reflectance distribution function degradation factor. The degradation factor, measured by an onboard solar diffuser stability monitor, has been shown to be both incident sunlight and outgoing direction dependent. In this Proceeding, we investigate the factor's dependence on SD position. We develop a model to relate the SD degradation factor with the amount of solar exposure. We use Earth measurements to evaluate the effectiveness of the model.

Burn Delay Analysis of the Lunar Orbit Insertion for Korea Pathfinder Lunar Orbiter

NASA Astrophysics Data System (ADS)

Bae, Jonghee; Song, Young-Joo; Kim, Young-Rok; Kim, Bangyeop

2017-12-01

The first Korea lunar orbiter, Korea Pathfinder Lunar Orbiter (KPLO), has been in development since 2016. After launch, the KPLO will execute several maneuvers to enter into the lunar mission orbit, and will then perform lunar science missions for one year. Among these maneuvers, the lunar orbit insertion (LOI) is the most critical maneuver because the KPLO will experience an extreme velocity change in the presence of the Moon’s gravitational pull. However, the lunar orbiter may have a delayed LOI burn during operation due to hardware limitations and telemetry delays. This delayed burn could occur in different captured lunar orbits; in the worst case, the KPLO could fly away from the Moon. Therefore, in this study, the burn delay for the first LOI maneuver is analyzed to successfully enter the desired lunar orbit. Numerical simulations are performed to evaluate the difference between the desired and delayed lunar orbits due to a burn delay in the LOI maneuver. Based on this analysis, critical factors in the LOI maneuver, the periselene altitude and orbit period, are significantly changed and an additional delta-V in the second LOI maneuver is required as the delay burn interval increases to 10 min from the planned maneuver epoch.

Determination of Orbital Parameters for Visual Binary Stars Using a Fourier-Series Approach

NASA Astrophysics Data System (ADS)

Brown, D. E.; Prager, J. R.; DeLeo, G. G.; McCluskey, G. E., Jr.

2001-12-01

We expand on the Fourier transform method of Monet (ApJ 234, 275, 1979) to infer the orbital parameters of visual binary stars, and we present results for several systems, both simulated and real. Although originally developed to address binary systems observed through at least one complete period, we have extended the method to deal explicitly with cases where the orbital data is less complete. This is especially useful in cases where the period is so long that only a fragment of the orbit has been recorded. We utilize Fourier-series fitting methods appropriate to data sets covering less than one period and containing random measurement errors. In so doing, we address issues of over-determination in fitting the data and the reduction of other deleterious Fourier-series artifacts. We developed our algorithm using the MAPLE mathematical software code, and tested it on numerous "synthetic" systems, and several real binaries, including Xi Boo, 24 Aqr, and Bu 738. This work was supported at Lehigh University by the Delaware Valley Space Grant Consortium and by NSF-REU grant PHY-9820301.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veiga, L. S. I.; Etter, M.; Glazyrin, K.

Here, we explore the response of Ir 5d orbitals to pressure in β-Li 2IrO 3, a hyperhoneycomb iridate in proximity to a Kitaev quantum spin-liquid (QSL) ground state. X-ray absorption spectroscopy reveals a reconstruction of the electronic ground state below 2 GPa, the same pressure range where x-ray magnetic circular dichroism shows an apparent collapse of magnetic order. The electronic reconstruction, which manifests a reduction in the effective spin-orbit interaction in 5d orbitals, pushes β-Li 2IrO 3 further away from the pure J eff = 1/2 limit. Although lattice symmetry is preserved across the electronic transition, x-ray diffraction shows amore » highly anisotropic compression of the hyperhoneycomb lattice which affects the balance of bond-directional Ir-Ir exchange interactions driven by spin-orbit coupling at Ir sites. An enhancement of symmetric anisotropic exchange over Kitaev and Heisenberg exchange interactions seen in theoretical calculations that use precisely this anisotropic Ir-Ir bond compression provides one possible route to the realization of a QSL state in this hyperhoneycomb iridate at high pressures.« less

Orbital angiogenesis and lymphangiogenesis in thyroid eye disease: an analysis of vascular growth factors with clinical correlation

PubMed Central

Wong, Lindsay L.; Lee, Nahyoung Grace; Amarnani, Dhanesh; Choi, Catherine J.; Bielenberg, Diane R.; Freitag, Suzanne K.; D’Amore, Patricia A.; Kim, Leo A.

2017-01-01

Purpose The human orbit is an environment that is vulnerable to inflammation and edema in the setting of autoimmune thyroid disease. Our study investigated the tenet that orbital adipose tissue lacks lymphatic vessels and analyzed the clinicopathologic differences between patients with acute and chronic thyroid eye disease (TED). The underlying molecular mediators of blood and lymphatic vessel formation within the orbital fat were also evaluated. Design Retrospective cohort study Participants The study included fat specimens from 26 orbits of 15 patients with TED undergoing orbital decompression. Orbital fat specimens from patients without TED as well as cadaveric orbital fat served as controls. Methods Tissue specimens were processed as formalin-fixed paraffin-embedded sections (FFPE) or frozen cryosections for immunohistochemistry. Total RNA was extracted and analyzed via quantitative (real-time) reverse transcription polymerase chain reaction (qRT-PCR). Clinicopathological correlation was made by determining the Clinical Activity Score (CAS) of each patient with TED. Main Outcome Measures Samples were examined for vascular and lymphatic markers including podoplanin, LYVE-1, and CD31 by immunohistochemistry, as well as for mRNA levels of VEGF, VEGF receptors, SEMA-3F, NRP-1, NRP-2, podoplanin and LYVE-1 by qRT-PCR. Results Clinicopathological correlation revealed increased staining of CD31-positive blood vessels in patients with acute TED with CAS > 4, as well as rare staining of podoplanin-positive lymphatic vessels within acutely inflamed orbital fat tissue. Additionally, qRT-PCR analysis demonstrated increased expression of vascular endothelial growth factor receptor 2 (VEGFR-2) as well as VEGF signaling molecules: VEGF-A, VEGF-C, and VEGF-D. Conclusions In acute TED, compared to chronic TED and control orbital fat, there is increased blood vessel density suggesting neovascularization and rare lymphatic vessels suggestive of limited lymphangiogenesis. This pro-angiogenic and pro-lymphangiogenic microenvironment is likely due to the increased expression of VEGFR-2 and VEGF-A, VEGF-C, and VEGF-D. These findings imply that orbital edema in acute TED may be mediated, in part, by both the formation of new, immature blood vessels and the formation of lymphatic capillaries that are functionally incapable of draining interstitial fluid. PMID:27423310

An Empirical Method for Determining the Lunar Gravity Field. Ph.D. Thesis - George Washington Univ.

NASA Technical Reports Server (NTRS)

Ferrari, A. J.

1971-01-01

A method has been devised to determine the spherical harmonic coefficients of the lunar gravity field. This method consists of a two-step data reduction and estimation process. In the first step, a weighted least-squares empirical orbit determination scheme is applied to Doppler tracking data from lunar orbits to estimate long-period Kepler elements and rates. Each of the Kepler elements is represented by an independent function of time. The long-period perturbing effects of the earth, sun, and solar radiation are explicitly modeled in this scheme. Kepler element variations estimated by this empirical processor are ascribed to the non-central lunar gravitation features. Doppler data are reduced in this manner for as many orbits as are available. In the second step, the Kepler element rates are used as input to a second least-squares processor that estimates lunar gravity coefficients using the long-period Lagrange perturbation equations.

Some significant considerations in the planning of sortie missions. [of space transportation system

NASA Technical Reports Server (NTRS)

Loftus, J. P., Jr.; Cour-Palais, B. G.; Moore, J. W.; Lohman, R. L.

1980-01-01

Opportunities and limitations to be considered in the planning of Space Shuttle/Spacelab sortie missions are discussed. As shown by a simple model of the flow of STS equipment through ground processing and flights under ideal conditions, mission duration is constrained by Orbiter availability, which is determined initially by the Orbiter production schedule and the turnaround time required between missions, and by the usage rate and quantity limitations of mission consumables. Additional considerations affecting mission duration include reductions in crew productivity upon increased mission duration and crew size, spacecraft and experiment degradation, equipment and processing facility cost effectiveness, and requirements for a power extension package, which considerations imply that increased allowable landing weight would make co-manifesting (the combination of Spacelab and deliverable payload missions) more attractive. Advantages related to payload recoverability, human presence, ease of access and the availability of different orbits are also pointed out.

[Medpor plus titanic mesh implant in the repair of orbital blowout fractures].

PubMed

Han, Xiao-hui; Zhang, Jia-yu; Cai, Jian-qiu; Shi, Ming-guang

2011-05-10

To study the efficacy of porous polyethylene (Medpor) plus titanic mesh sheets in the repair of orbital blowout fractures. A total of 20 patients underwent open surgical reduction with the combined usage of Medpor and titanic mesh. And they were followed up for average period of 14.5 months (range: 9 - 18). There is no infection or extrusion of medpor and titanic mesh in follow-up periods. There was no instance of decreased visual acuity at post-operation. And all cases of enophthalmos were corrected. The post-operative protrusion degree of both eyes was almost identical at less than 2 mm. The movement of eye balls was satisfactory in all directions. Diplopia disappeared in 18 cases with a cure rate of 90%, 1 case improved and 1 case persisted. Medpor plus titanic mesh implant is a safe and effective treatment in the repair of orbital blow out fractures.

Potential advantages of solar electric propulsion for outer planet orbiters.

NASA Technical Reports Server (NTRS)

Sauer, C. G.; Atkins, K. L.

1972-01-01

Past studies of solar electric propulsion for outer planet orbiters have generally emphasized the advantages of flight time reduction and payload increases. However, several subtle advantages exist, which may become important in an environment of increasingly difficult requirements as ways to extend current technology are sought. These advantages accrue primarily because of the inherent capability, unique to electric propulsion, to efficiently shape a trajectory while enroute. Stressed in this paper are: the ability to meet orbital constraints due to assumed radiation belts, science flexibility in a dual launch program, increased numbers of observational passes, and the lengthening of launch periods. These are examined for years representative of relatively easy and difficult ballistic missions. The results indicate that an early investment in solar electric technology will provide a strong performance foundation for a long range outer planet exploration program which evolves from current spacecraft technology.

Use of orbital floor steroids in the management of patients with uniocular non-necrotising scleritis.

PubMed Central

Hakin, K N; Ham, J; Lightman, S L

1991-01-01

Most cases of non-necrotising scleritis can be successfully treated with non-steroidal anti-inflammatory drugs. If these are ineffective, then high-dose systemic corticosteroids, with all their attendant side-effects, are usually required. We have used orbital floor injections of depot steroid in the management of nine patients with non-necrotising scleritis in an attempt to avoid the use of systemic steroids, or to allow the dose of steroids to be reduced while maintaining disease control. A temporary reduction in inflammation was achieved in all cases, which allowed the use of systemic steroids to be avoided altogether in two patients and delayed in the others. Non-steroidal anti-inflammatory drugs and systemic corticosteroids remain the mainstay of treatment for non-necrotising scleritis, but orbital floor injections may be a useful adjunct in certain cases. Images PMID:2043574

Analysis of aerothermodynamic environment of a Titan aerocapture vehicle

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Chow, H.; Moss, J. N.

1982-01-01

The feasibility of an aerocapture vehicle mission has been emphasized recently for inner and outer planetary missions. Aerocapture involves a system concept which utilizes aerodynamic drag to acquire the velocity reduction necessary to obtain a closed planetary orbit from a hyperbolic flyby trajectory. It has been proposed to use the atmosphere of Titan for braking into a Saturn orbit. This approach for a Saturn orbital mission is expected to cut the interplanetary cruise travel time to Saturn from 8 to 3.5 years. In connection with the preparation of such a mission, it will be necessary to provide a complete analysis of the aerodynamic environment of the Titan aerocapture vehicle. The main objective of the present investigation is, therefore, to determine the extent of convective and radiative heating for the aerocapture vehicle under different entry conditions. This can be essentially accomplished by assessing the heating rates in the stagnation and windward regions of an equivalent body.

KSC-2012-4215

NASA Image and Video Library

2012-08-03

CAPE CANAVERAL, Fla. -- This is an artist's conception of NASA's Commercial Crew Program or CCP, logo and low Earth orbit. The program is entering its third phase of development, called Commercial Crew integrated Capability, or CCiCap, to propel America's next human space transportation system to low Earth orbit forward. Operating under funded Space Act Agreements, or SAAs, The Boeing Co. of Houston, Sierra Nevada Corp., or SNC, Space Systems of Louisville, Colo., and Space Exploration Technologies, or SpaceX, of Hawthorne, Calif., will spend the next 21 months completing their designs, conducting critical risk reduction testing on their spacecraft and launch vehicles, and showcasing how they would operate and manage missions from launch through orbit and landing, setting the stage for future demonstration missions. To learn more about CCP, which is based at Kennedy and supported by NASA's Johnson Space Center in Houston, visit www.nasa.gov/commercialcrew. Image credit: NASA/Matthew Young

Analytic study of orbiter landing profiles

NASA Technical Reports Server (NTRS)

Walker, H. J.

1981-01-01

A broad survey of possible orbiter landing configurations was made with specific goals of defining boundaries for the landing task. The results suggest that the center of the corridors between marginal and routine represents a more or less optimal preflare condition for regular operations. Various constraints used to define the boundaries are based largely on qualitative judgements from earlier flight experience with the X-15 and lifting body research aircraft. The results should serve as useful background for expanding and validating landing simulation programs. The analytic approach offers a particular advantage in identifying trends due to the systematic variation of factors such as vehicle weight, load factor, approach speed, and aim point. Limitations such as a constant load factor during the flare and using a fixed gear deployment time interval, can be removed by increasing the flexibility of the computer program. This analytic definition of landing profiles of the orbiter may suggest additional studies, includin more configurations or more comparisons of landing profiles within and beyond the corridor boundaries.

Thermospheric density estimation from SLR observations of LEO satellites - A case study with the ANDE-Pollux satellite

NASA Astrophysics Data System (ADS)

Blossfeld, M.; Schmidt, M.; Erdogan, E.

2016-12-01

The thermospheric neutral density plays a crucial role within the equation of motion of Earth orbiting objects since drag, lift or side forces are one of the largest non-gravitational perturbations acting on the satellite. Precise Orbit Determination (POD) methods can be used to estimate thermospheric density variations from measured orbit determinations. One method which provides highly accurate measurements of the satellite position is Satellite Laser Ranging (SLR). Within the POD process, scaling factors are estimated frequently. These scaling factors can be either used for the scaling of the so called satellite-specific drag (ballistic) coefficients or the integrated thermospheric neutral density. We present a method for analytically model the drag coefficient based on a couple of physical assumptions and key parameters. In this paper, we investigate the possibility to use SLR observations to the very low Earth orbiting satellite ANDE-Pollux (approximately at 350km altitude) to determine scaling factors for different a priori thermospheric density models. We perform a POD for ANDE-Pollux covering 49 days between August 2009 and September 2009 which means the time span containing the largest number of observations during the short lifetime of the satellite. Finally, we compare the obtained scaled thermospheric densities w.r.t. each other

Lessions learned in WISE image quality

NASA Astrophysics Data System (ADS)

Kendall, Martha; Duval, Valerie G.; Larsen, Mark F.; Heinrichsen, Ingolf H.; Esplin, Roy W.; Shannon, Mark; Wright, Edward L.

2010-08-01

The Wide-Field Infrared Survey Explorer (WISE) mission launched in December of 2009 is a true success story. The mission is performing beyond expectations on-orbit and maintained cost and schedule throughout. How does such a thing happen? A team constantly focused on mission success is a key factor. Mission success is more than a program meeting its ultimate science goals; it is also meeting schedule and cost goals to avoid cancellation. The WISE program can attribute some of its success in achieving the image quality needed to meet science goals to lessons learned along the way. A requirement was missed in early decomposition, the absence of which would have adversely affected end-to-end system image quality. Fortunately, the ability of the cross-organizational team to focus on fixing the problem without pointing fingers or waiting for paperwork was crucial in achieving a timely solution. Asking layman questions early in the program could have revealed requirement flowdown misunderstandings between spacecraft control stability and image processing needs. Such is the lesson learned with the WISE spacecraft Attitude Determination & Control Subsystem (ADCS) jitter control and the image data reductions needs. Spacecraft motion can affect image quality in numerous ways. Something as seemingly benign as different terminology being used by teammates in separate groups working on data reduction, spacecraft ADCS, the instrument, mission operations, and the science proved to be a risk to system image quality. While the spacecraft was meeting the allocated jitter requirement , the drift rate variation need was not being met. This missing need was noticed about a year before launch and with a dedicated team effort, an adjustment was made to the spacecraft ADCS control. WISE is meeting all image quality requirements on-orbit thanks to a diligent team noticing something was missing before it was too late and applying their best effort to find a solution.

Space transportation and destination considerations for extraterrestrial disposal of radioactive waste

NASA Technical Reports Server (NTRS)

Zimmerman, A. V.; Thompson, R. L.; Lubick, R. J.

1973-01-01

A feasibility study is summarized of extraterrestrial (space) disposal of radioactive waste. The initial work on the evaluation and comparison of possible space destinations and launch vehicles is reported. Only current or planned space transportation systems were considered. The currently planned space shuttle was found to be more cost effective than current expendable launch vehicles, by about a factor of two. The space shuttle will require a third stage to perform the disposal missions. Depending on the particular mission this could be either a reusable space tug or an expendable stage such as a Centaur. Of the destinations considered, high earth orbits (between geostationary and lunar orbit altitudes), solar orbits (such as a 0.90 AU circular solar orbit) or a direct injection to solar system escape appear to be the best candidates. Both earth orbits and solar orbits have uncertainties regarding orbit stability and waste package integrity for times on the order of a million years.

A Review of Microgravity Levels on Ten OARE Shuttle Missions

NASA Technical Reports Server (NTRS)

McPherson, Kevin M.

1998-01-01

The Orbital Acceleration Research Experiment (OARE) is an accelerometer package with nano-g sensitivity and on-orbit bias calibration capabilities. The OARE consists of a three axis miniature electrostatic accelerometer (MESA), a full in-flight bias and scale factor calibration station, and an on-board microprocessor for experiment control and data storage. Originally designed to measure and record the aerodynamic acceleration environment of the NASA Space Shuttles during re-entry, the OARE has been used on ten shuttle missions to measure the quasi-steady acceleration environment (<1 Hz) of the Orbiter while in low-Earth orbit. The effects on the quasi-steady acceleration environment from Orbiter systems, Orbiter attitude, Orbiter altitude, and crew activity are well understood as a result of these ten shuttle missions. This knowledge of the quasi-steady acceleration realm has direct application to understanding the quasi-steady acceleration environment expected for the International Space Station (ISS). This paper will summarize the more salient aspects of this quasi-steady acceleration knowledge base.

Space Transfer Concepts and Analyses for Exploration Missions. Technical Directive 12: Beamed Power Systems Study

NASA Technical Reports Server (NTRS)

Eder, D.

1992-01-01

Parametric models were constructed for Earth-based laser powered electric orbit transfer from low Earth orbit to geosynchronous orbit. These models were used to carry out performance, cost/benefit, and sensitivity analyses of laser-powered transfer systems including end-to-end life cycle cost analyses for complete systems. Comparisons with conventional orbit transfer systems were made indicating large potential cost savings for laser-powered transfer. Approximate optimization was done to determine best parameter values for the systems. Orbit transfer flights simulations were conducted to explore effects of parameters not practical to model with a spreadsheet. The simulations considered view factors that determine when power can be transferred from ground stations to an orbit transfer vehicle and conducted sensitivity analyses for numbers of ground stations, Isp including dual-Isp transfers, and plane change profiles. Optimal steering laws were used for simultaneous altitude and plane change. Viewing geometry and low-thrust orbit raising were simultaneously simulated. A very preliminary investigation of relay mirrors was made.

Gravity fields. [Jovian, Martian, Cytherean, Mercurian and lunar mass distributions

NASA Technical Reports Server (NTRS)

Sjogren, W. L.; Anderson, J. D.; Phillips, R. J.; Trask, D. W.

1976-01-01

Detailed results on internal mass distribution have been obtained via earth-based Doppler radio tracking of deep space probes in the case of Mars, the earth's moon, Venus, Mercury, and Jupiter. Global gravity fields show close correlation with topography in the case of the moon and Mars, as data from orbiting spacecraft indicate. Some data are available on Jovian satellites. The gravity measuring instrumentation and data reduction techniques are described. Gravity profiles referable to lunar frontside mascons, craters, and mountain chains have been acquired from low-altitude (15-20 km) orbit surveys. Theoretically based cross sections through the moon and Jupiter are presented.

Transonic stability and control characteristics of a 0.015 scale model 69-0 of the space shuttle orbiter with forebody RSI modification in the NASA/LaRC 8 foot TPT (LA72)

NASA Technical Reports Server (NTRS)

Ball, J. W.; Edwards, C. R.

1976-01-01

Tests were conducted in the NASA/LaRC 8 foot transonic wind tunnel from March 26 through 31, 1976. The model was a 0.015 scale SSV Orbiter with forebody modifications to simulate slight reductions in the reusable surface insulation (RSI) thickness. Six component aerodynamic force and moment data were obtained at Mach numbers from 0.35 to 1.20 over an angle of attack range from -2 deg to 20 deg at sideslip angles of 0 deg and 5 deg.

Spectrum and orbit conservation as a factor in future mobile satellite system design

NASA Technical Reports Server (NTRS)

Bowen, Robert R.

1990-01-01

Access to the radio spectrum and geostationary orbit is essential to current and future mobile satellite systems. This access is difficult to obtain for current systems, and may be even more so for larger future systems. In this environment, satellite systems that minimize the amount of spectrum orbit resource required to meet a specific traffic requirement are essential. Several spectrum conservation techniques are discussed, some of which are complementary to designing the system at minimum cost. All may need to be implemented to the limits of technological feasibility if network growth is not to be constrained because of the lack of available spectrum-orbit resource.

Global communication using a constellation of low earth meridian orbits

NASA Astrophysics Data System (ADS)

Oli, P. V. S.; Nagarajan, N.; Rayan, H. R.

1993-07-01

The concept of 'meridian orbits' is briefly reviewed. It is shown that, if a satellite in the meridian orbit makes an odd number of revolutions per day, then the satellite passes over the same set of meridians twice a day. Satellites in such orbits pass over the same portion of the sky twice a day and every day. This enables a user to adopt a programmed mode of tracking, thereby avoiding a computational facility for orbit prediction, look angle generation, and auto tracking. A constellation of 38 or more satellites placed in a 1200 km altitude circular orbit is favorable for global communications due to various factors. It is shown that appropriate phasing in right ascension of the ascending node and mean anomaly results in a constellation, wherein each satellite appears over the user's horizon one satellite after another. Visibility and coverage plots are provided to verify the continuous coverage.

Satellite orbit determination using quantum correlation technology

NASA Astrophysics Data System (ADS)

Zhang, Bo; Sun, Fuping; Zhu, Xinhui; Jia, Xiaolin

2018-03-01

After the presentation of second-order correlation ranging principles with quantum entanglement, the concept of quantum measurement is introduced to dynamic satellite precise orbit determination. Based on the application of traditional orbit determination models for correcting the systematic errors within the satellite, corresponding models for quantum orbit determination (QOD) are established. This paper experiments on QOD with the BeiDou Navigation Satellite System (BDS) by first simulating quantum observations of 1 day arc-length. Then the satellite orbits are resolved and compared with the reference precise ephemerides. Subsequently, some related factors influencing the accuracy of QOD are discussed. Furthermore, the accuracy for GEO, IGSO and MEO satellites increase about 20, 30 and 10 times, respectively, compared with the results from the resolution by measured data. Therefore, it can be expected that quantum technology may also bring delightful surprises to satellite orbit determination as have already emerged in other fields.

Orbit selection of nanosatellite formation in term of fuel consumption

NASA Astrophysics Data System (ADS)

Pimnoo, Ammarin; Hiraki, Koju

In nanosatellite formation mission design, orbit selection is a necessary factor. Fuel consumption is also necessary to maintain the orbit. Therefore, the best orbit should be the one of minimum fuel consumption for nanosatellite formation. The purpose of this paper is to provide a convenient way to estimate fuel consumption for a nanosatellite to keep formation flying. The formation is disturbed by J _{2} perturbation and other perturbing accelerations. Firstly, the Hill-Clohessy-Wiltshire equations are used in the analysis. Gaussian variation of parameters is included into the Hill’s equation to analyze the variation of Kaplerian orbital elements. The J _{2} perturbation and other perturbing accelerations such as atmospheric drag, solar-radiation pressure and third-body perturbations are considered. Thus, a linear model based on Hill’s equation is established to estimate fuel consumption. Finally, an example of the best orbit for formation flying with minimum fuel consumption shall be presented.

Reduction procedures for accurate analysis of MSX surveillance experiment data

NASA Technical Reports Server (NTRS)

Gaposchkin, E. Mike; Lane, Mark T.; Abbot, Rick I.

1994-01-01

Technical challenges of the Midcourse Space Experiment (MSX) science instruments require careful characterization and calibration of these sensors for analysis of surveillance experiment data. Procedures for reduction of Resident Space Object (RSO) detections will be presented which include refinement and calibration of the metric and radiometric (and photometric) data and calculation of a precise MSX ephemeris. Examples will be given which support the reduction, and these are taken from ground-test data similar in characteristics to the MSX sensors and from the IRAS satellite RSO detections. Examples to demonstrate the calculation of a precise ephemeris will be provided from satellites in similar orbits which are equipped with S-band transponders.

Enzymatic reduction of acetophenone derivatives with a benzil reductase from Pichia glucozyma (KRED1-Pglu): electronic and steric effects on activity and enantioselectivity.

PubMed

Contente, Martina L; Serra, Immacolata; Palazzolo, Luca; Parravicini, Chiara; Gianazza, Elisabetta; Eberini, Ivano; Pinto, Andrea; Guidi, Benedetta; Molinari, Francesco; Romano, Diego

2016-04-07

A recombinant ketoreductase from Pichia glucozyma (KRED1-Pglu) was used for the enantioselective reduction of various mono-substituted acetophenones. Reaction rates of meta- and para-derivatives were consistent with the electronic effects described by σ-Hammett coefficients; on the other hand, enantioselectivity was determined by an opposite orientation of the substrate in the binding pocket. Reduction of ortho-derivatives occurred only with substrates bearing substituents with low steric impact (i.e., F and CN). Reactivity was controlled by stereoelectronic features (C[double bond, length as m-dash]O length and charge, shape of LUMO frontier molecular orbitals), which can be theoretically calculated.

Utilizing Solar Power Technologies for On-Orbit Propellant Production

NASA Technical Reports Server (NTRS)

Fikes, John C.; Howell, Joe T.; Henley, Mark W.

2006-01-01

The cost of access to space beyond low Earth orbit may be reduced if vehicles can refuel in orbit. The cost of access to low Earth orbit may also be reduced by launching oxygen and hydrogen propellants in the form of water. To achieve this reduction in costs of access to low Earth orbit and beyond, a propellant depot is considered that electrolyzes water in orbit, then condenses and stores cryogenic oxygen and hydrogen. Power requirements for such a depot require Solar Power Satellite technologies. A propellant depot utilizing solar power technologies is discussed in this paper. The depot will be deployed in a 400 km circular equatorial orbit. It receives tanks of water launched into a lower orbit from Earth, converts the water to liquid hydrogen and oxygen, and stores up to 500 metric tons of cryogenic propellants. This requires a power system that is comparable to a large Solar Power Satellite capable of several 100 kW of energy. Power is supplied by a pair of solar arrays mounted perpendicular to the orbital plane, which rotates once per orbit to track the Sun. The majority of the power is used to run the electrolysis system. Thermal control is maintained by body-mounted radiators; these also provide some shielding against orbital debris. The propellant stored in the depot can support transportation from low Earth orbit to geostationary Earth orbit, the Moon, LaGrange points, Mars, etc. Emphasis is placed on the Water-Ice to Cryogen propellant production facility. A very high power system is required for cracking (electrolyzing) the water and condensing and refrigerating the resulting oxygen and hydrogen. For a propellant production rate of 500 metric tons (1,100,000 pounds) per year, an average electrical power supply of 100 s of kW is required. To make the most efficient use of space solar power, electrolysis is performed only during the portion of the orbit that the Depot is in sunlight, so roughly twice this power level is needed for operations in sunlight (slightly over half of the time). This power level mandates large solar arrays, using advanced Space Solar Power technology. A significant amount of the power has to be dissipated as heat, through large radiators. This paper briefly describes the propellant production facility and the requirements for a high power system capability. The Solar Power technologies required for such an endeavor are discussed.

Addressing Human System Risks to Future Space Exploration

NASA Technical Reports Server (NTRS)

Paloski, W. H.; Francisco, D. R.; Davis, J. R.

2015-01-01

NASA is contemplating future human exploration missions to destinations beyond low Earth orbit, including the Moon, deep-space asteroids, and Mars. While we have learned much about protecting crew health and performance during orbital space flight over the past half-century, the challenges of these future missions far exceed those within our current experience base. To ensure success in these missions, we have developed a Human System Risk Board (HSRB) to identify, quantify, and develop mitigation plans for the extraordinary risks associated with each potential mission scenario. The HSRB comprises research, technology, and operations experts in medicine, physiology, psychology, human factors, radiation, toxicology, microbiology, pharmacology, and food sciences. Methods: Owing to the wide range of potential mission characteristics, we first identified the hazards to human health and performance common to all exploration missions: altered gravity, isolation/confinement, increased radiation, distance from Earth, and hostile/closed environment. Each hazard leads to a set of risks to crew health and/or performance. For example the radiation hazard leads to risks of acute radiation syndrome, central nervous system dysfunction, soft tissue degeneration, and carcinogenesis. Some of these risks (e.g., acute radiation syndrome) could affect crew health or performance during the mission, while others (e.g., carcinogenesis) would more likely affect the crewmember well after the mission ends. We next defined a set of design reference missions (DRM) that would span the range of exploration missions currently under consideration. In addition to standard (6-month) and long-duration (1-year) missions in low Earth orbit (LEO), these DRM include deep space sortie missions of 1 month duration, lunar orbital and landing missions of 1 year duration, deep space journey and asteroid landing missions of 1 year duration, and Mars orbital and landing missions of 3 years duration. We then assessed the likelihood and consequences of each risk against each DRM, using three levels of likelihood (Low: less than or equal to 0.1%; Medium: 0.1%–1.0%; High: greater than or equal to 1.0%) and four levels of consequence ranging from Very Low (temporary or insignificant) to High (death, loss of mission, or significant reduction to length or quality of life). Quantitative evidence from clinical, operational, and research sources were used whenever available. Qualitative evidence was used when quantitative evidence was unavailable. Expert opinion was used whenever insufficient evidence was available. Results: A set of 30 risks emerged that will require further mitigation efforts before being accepted by the Agency. The likelihood by consequence risk assessment process provided a means of prioritizing among the risks identified. For each of the high priority risks, a plan was developed to perform research, technology, or standards development thought necessary to provide suitable reduction of likelihood or consequence to allow agency acceptance. Conclusion: The HSRB process has successfully identified a complete set of risks to human space travelers on planned exploration missions based on the best evidence available today. Risk mitigation plans have been established for the highest priority risks. Each risk will be reassessed annually to track the progress of our risk mitigation efforts.

Effect of ephemeris errors on the accuracy of the computation of the tangent point altitude of a solar scanning ray as measured by the SAGE 1 and 2 instruments

NASA Technical Reports Server (NTRS)

Buglia, James J.

1989-01-01

An analysis was made of the error in the minimum altitude of a geometric ray from an orbiting spacecraft to the Sun. The sunrise and sunset errors are highly correlated and are opposite in sign. With the ephemeris generated for the SAGE 1 instrument data reduction, these errors can be as large as 200 to 350 meters (1 sigma) after 7 days of orbit propagation. The bulk of this error results from errors in the position of the orbiting spacecraft rather than errors in computing the position of the Sun. These errors, in turn, result from the discontinuities in the ephemeris tapes resulting from the orbital determination process. Data taken from the end of the definitive ephemeris tape are used to generate the predict data for the time interval covered by the next arc of the orbit determination process. The predicted data are then updated by using the tracking data. The growth of these errors is very nearly linear, with a slight nonlinearity caused by the beta angle. An approximate analytic method is given, which predicts the magnitude of the errors and their growth in time with reasonable fidelity.

Information origins of the chemical bond: Bond descriptors from molecular communication channels in orbital resolution

NASA Astrophysics Data System (ADS)

Nalewajski, Roman F.

The flow of information in the molecular communication networks in the (condensed) atomic orbital (AO) resolution is investigated and the plane-wave (momentum-space) interpretation of the average Fisher information in the molecular information system is given. It is argued using the quantum-mechanical superposition principle that, in the LCAO MO theory the squares of corresponding elements of the Charge and Bond-Order (CBO) matrix determine the conditional probabilities between AO, which generate the molecular communication system of the Orbital Communication Theory (OCT) of the chemical bond. The conditional-entropy ("noise," information-theoretic "covalency") and the mutual-information (information flow, information-theoretic "ionicity") descriptors of these molecular channels are related to Wiberg's covalency indices of chemical bonds. The illustrative application of OCT to the three-orbital model of the chemical bond X-Y, which is capable of describing the forward- and back-donations as well as the atom promotion accompanying the bond formation, is reported. It is demonstrated that the entropy/information characteristics of these separate bond-effects can be extracted by an appropriate reduction of the output of the molecular information channel, carried out by combining several exits into a single (condensed) one. The molecular channels in both the AO and hybrid orbital representations are examined for both the molecular and representative promolecular input probabilities.

Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone.

PubMed

Joshi, Manoj M; Haberle, Robert M

2012-01-01

M stars comprise 80% of main sequence stars, so their planetary systems provide the best chance for finding habitable planets, that is, those with surface liquid water. We have modeled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M stars), using spectrally resolved data of Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 μm, combined with M stars emitting a significant fraction of their radiation at these same longer wavelengths, means that the albedos of ice and snow on planets orbiting M stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M stars may be 10-30% farther away from the parent star than previously thought.

Radiation risk predictions for Space Station Freedom orbits

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Atwell, William; Weyland, Mark; Hardy, Alva C.; Wilson, John W.; Townsend, Lawrence W.; Shinn, Judy L.; Katz, Robert

1991-01-01

Risk assessment calculations are presented for the preliminary proposed solar minimum and solar maximum orbits for Space Station Freedom (SSF). Integral linear energy transfer (LET) fluence spectra are calculated for the trapped proton and GCR environments. Organ dose calculations are discussed using the computerized anatomical man model. The cellular track model of Katz is applied to calculate cell survival, transformation, and mutation rates for various aluminum shields. Comparisons between relative biological effectiveness (RBE) and quality factor (QF) values for SSF orbits are made.

A theoretical probe of high-valence uranium and transuranium silylamides: Structural and redox properties

NASA Astrophysics Data System (ADS)

Zhong, Yu-Xi; Guo, Yuan-Ru; Pan, Qing-Jiang

2016-02-01

Relativistic density functional theory was used to explore the structural and redox properties of 18 prototypical actinyl silylamides including a variation of metals (U, Np and Pu), metal oxidation states (VI and V) and equatorial ligands. A theoretical approach associated with implicit solvation and spin-orbit/multiplet corrections was proved to be reliable. A marked shift of reduction potentials of actinyl silylamides caused by changes of equatorial coordination ligands and implicit solvation was elucidated by analyses of electronic structures and single-electron reduction mechanism.

Prototype microprocessor controller. [for STDN antennas

NASA Technical Reports Server (NTRS)

Zarur, J.; Kraeuter, R.

1980-01-01

A microcomputer controller for STDN antennas was developed. The microcomputer technology reduces the system's physical size by the implementation in firmware of functions. The reduction in the number of components increases system reliability and similar benefit is derived when a graphic video display is substituted for several control and indicator panels. A substantial reduction in the number of cables, connectors, and mechanical switches is achieved. The microcomputer based system is programmed to perform calibration and diagnostics, to update the satellite orbital vector, and to communicate with other network systems. The design is applicable to antennas and lasers.

The observational basis for JPL's DE 200, the planetary ephemerides of the Astronomical Almanac

NASA Astrophysics Data System (ADS)

Standish, E. M., Jr.

1990-07-01

This paper documents the planetary observational data used in a series of ephemerides produced at JPL over six years preceding the creation of DE118/LE62, the set which transformed directly into the JD2000-based set, DE200/LE200. Details of the data reduction procedures are presented, and techniques to overcome the uncertainties due to planetary topography are described. For the spacecraft data, the basic reductions are augmented by formulations for locating the transponder, whether in orbit or landed on the surface of a planet.

Reduction of factor XII in antiphospholipid antibody-positive patients with thrombotic events in the rheumatology clinic.

PubMed

Takeishi, M; Mimori, A; Nakajima, K; Mimura, T; Suzuki, T

2003-02-01

Although rheumatological diagnosis often includes an assessment of antiphospholipid (aPL) antibodies, the significance of other prothrombotic factors has not been established in thrombotic patients who are not afflicted with either arteriosclerosis or vasculitis syndrome. We have observed both the presence of antiphospholipid antibodies and a reduction of factor XII in such patients. Our results identified both lupus anticoagulant-positive (50%) and anticardiolipin antibody-positive (58%) patients. In addition, 83% of patients showed factor XII antigen level reduction. Furthermore, 70% of aPL-positive thrombotic patients showed factor XII antigen level reduction. Only two cases had antiphospholipid antibody alone, and 4/12 showed just factor XII antigen reduction. Recently, it has been reported that the presence of antiphospholipid antibodies induces factor XII reduction, and that anti-factor XII autoantibody can be detected in thrombotic patients. However, our results indicate that there are smaller factor XII reductions in non-thrombotic controls who are positive for antiphospholipid antibodies. Furthermore, anti-factor XII autoantibody was not detected in patients with decreased factor XII levels. Kindred research suggested that in two patients there was a genetic component to factor XII reduction. We concluded that the presence of both antiphospholipid antibodies and reduced serum factor XII was observed in most thrombotic patients from our rheumatology clinic. It is therefore possible to consider that the coexistence of these prothrombotic factors can contribute to the onset of thrombosis.

Variations in Titan's dune orientations as a result of orbital forcing

NASA Astrophysics Data System (ADS)

McDonald, George D.; Hayes, Alexander G.; Ewing, Ryan C.; Lora, Juan M.; Newman, Claire E.; Tokano, Tetsuya; Lucas, Antoine; Soto, Alejandro; Chen, Gang

2016-05-01

Wind-blown dunes are a record of the climatic history in Titan's equatorial region. Through modeling of the climatic conditions associated with Titan's historical orbital configurations (arising from apsidal precessions of Saturn's orbit), we present evidence that the orientations of the dunes are influenced by orbital forcing. Analysis of 3 Titan general circulation models (GCMs) in conjunction with a sediment transport model provides the first direct intercomparison of results from different Titan GCMs. We report variability in the dune orientations predicted for different orbital epochs of up to 70°. Although the response of the GCMs to orbital forcing varies, the orbital influence on the dune orientations is found to be significant across all models. Furthermore, there is near agreement among the two models run with surface topography, with 3 out of the 5 dune fields matching observation for the most recent orbital cycle. Through comparison with observations by Cassini, we find situations in which the observed dune orientations are in best agreement with those modeled for previous orbital configurations or combinations thereof, representing a larger portion of the cycle. We conclude that orbital forcing could be an important factor in governing the present-day dune orientations observed on Titan and should be considered when modeling dune evolution.

Factorization and resummation: A new paradigm to improve gravitational wave amplitudes

NASA Astrophysics Data System (ADS)

Nagar, Alessandro; Shah, Abhay

2016-11-01

We introduce a new resummed analytical form of the post-Newtonian (PN), factorized, multipolar amplitude corrections fℓm of the effective-one-body (EOB) gravitational waveform of spinning, nonprecessing, circularized, coalescing black hole binaries (BBHs). This stems from the following two-step paradigm: (i) the factorization of the orbital (spin-independent) terms in fℓm; (ii) the resummation of the residual spin (or orbital) factors. We find that resumming the residual spin factor by taking its inverse resummed (iResum) is an efficient way to obtain amplitudes that are more accurate in the strong-field, fast-velocity regime. The performance of the method is illustrated on the ℓ=2 and m =(1 ,2 ) waveform multipoles, both for a test mass orbiting around a Kerr black hole and for comparable-mass BBHs. In the first case, the iResum fℓm's are much closer to the corresponding "exact" functions (obtained by numerically solving the Teukolsky equation) up to the light ring than the nonresummed ones, especially when the black-hole spin is nearly extremal. The iResum paradigm is also more efficient than including higher post-Newtonian terms (up to 20PN order): the resummed 5PN information yields per se a rather good numerical or analytical agreement at the last stable orbit and a well-controlled behavior up to the light ring. For comparable mass binaries (including the highest PN-order information available, 3.5PN), comparing EOB with numerical relativity (NR) data shows that the EOB/NR fractional disagreement at merger, without NR calibration of the EOB waveform, is generically reduced by iResum, from 40% of the usual approach to just a few percent. This suggests that EOBNR waveform models for coalescing BBHs may be improved by using iResum amplitudes.

Orbit Determination During Spacecraft Emergencies with Sparse Tracking Data - THEMIS and TDRS-3 Lessons Learned

NASA Technical Reports Server (NTRS)

Morinelli, Patrick J.; Ward, Douglas T.; Blizzard, Michael R.; Mendelsohn, Chad R.

2008-01-01

This paper provides an overview of the lessons learned from the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center s (GSFC) Flight Dynamics Facility s (FDF) support of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft emergency in February 2007, and the Tracking and Data Relay Satellite-3 (TDRS-3) spacecraft emergency in March 2006. A successful and timely recovery from both of these spacecraft emergencies depended on accurate knowledge of the orbit. Unfortunately, the combination of each spacecraft emergency with very little tracking data contributed to difficulties in estimating and predicting the orbit and delayed recovery efforts in both cases. In both the THEMIS and TDRS-3 spacecraft emergencies, numerous factors contributed to problems with obtaining nominal tracking data measurements. This paper details the various causative factors and challenges. This paper further enumerates lessons learned from FDF s recovery efforts involving the THEMIS and TDRS-3 spacecraft emergencies and scant tracking data, as well as recommendations for improvements and corrective actions. In addition, this paper describes the broad range of resources and complex navigation methods employed within the FDF for supporting critical navigation activities during all mission phases, including launch, early orbit, and on-orbit operations.

Quasiparticle band gap of organic-inorganic hybrid perovskites: Crystal structure, spin-orbit coupling, and self-energy effects

NASA Astrophysics Data System (ADS)

Gao, Weiwei; Gao, Xiang; Abtew, Tesfaye A.; Sun, Yi-Yang; Zhang, Shengbai; Zhang, Peihong

2016-02-01

The quasiparticle band gap is one of the most important materials properties for photovoltaic applications. Often the band gap of a photovoltaic material is determined (and can be controlled) by various factors, complicating predictive materials optimization. An in-depth understanding of how these factors affect the size of the gap will provide valuable guidance for new materials discovery. Here we report a comprehensive investigation on the band gap formation mechanism in organic-inorganic hybrid perovskites by decoupling various contributing factors which ultimately determine their electronic structure and quasiparticle band gap. Major factors, namely, quasiparticle self-energy, spin-orbit coupling, and structural distortions due to the presence of organic molecules, and their influences on the quasiparticle band structure of organic-inorganic hybrid perovskites are illustrated. We find that although methylammonium cations do not contribute directly to the electronic states near band edges, they play an important role in defining the band gap by introducing structural distortions and controlling the overall lattice constants. The spin-orbit coupling effects drastically reduce the electron and hole effective masses in these systems, which is beneficial for high carrier mobilities and small exciton binding energies.

20 CFR 228.16 - Adjustments in the age reduction factor (ARF).

Code of Federal Regulations, 2010 CFR

2010-04-01

... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Adjustments in the age reduction factor (ARF... RETIREMENT ACT COMPUTATION OF SURVIVOR ANNUITIES The Tier I Annuity Component § 228.16 Adjustments in the age reduction factor (ARF). Upon the attainment of retirement age, the previously-computed age reduction factor...

20 CFR 228.16 - Adjustments in the age reduction factor (ARF).

Code of Federal Regulations, 2014 CFR

2014-04-01

... 20 Employees' Benefits 1 2014-04-01 2012-04-01 true Adjustments in the age reduction factor (ARF... RETIREMENT ACT COMPUTATION OF SURVIVOR ANNUITIES The Tier I Annuity Component § 228.16 Adjustments in the age reduction factor (ARF). Upon the attainment of retirement age, the previously-computed age reduction factor...

20 CFR 228.16 - Adjustments in the age reduction factor (ARF).

Code of Federal Regulations, 2013 CFR

2013-04-01

... 20 Employees' Benefits 1 2013-04-01 2012-04-01 true Adjustments in the age reduction factor (ARF... RETIREMENT ACT COMPUTATION OF SURVIVOR ANNUITIES The Tier I Annuity Component § 228.16 Adjustments in the age reduction factor (ARF). Upon the attainment of retirement age, the previously-computed age reduction factor...

20 CFR 228.16 - Adjustments in the age reduction factor (ARF).

Code of Federal Regulations, 2011 CFR

2011-04-01

... 20 Employees' Benefits 1 2011-04-01 2011-04-01 false Adjustments in the age reduction factor (ARF... RETIREMENT ACT COMPUTATION OF SURVIVOR ANNUITIES The Tier I Annuity Component § 228.16 Adjustments in the age reduction factor (ARF). Upon the attainment of retirement age, the previously-computed age reduction factor...

20 CFR 228.16 - Adjustments in the age reduction factor (ARF).

Code of Federal Regulations, 2012 CFR

2012-04-01

... 20 Employees' Benefits 1 2012-04-01 2012-04-01 false Adjustments in the age reduction factor (ARF... RETIREMENT ACT COMPUTATION OF SURVIVOR ANNUITIES The Tier I Annuity Component § 228.16 Adjustments in the age reduction factor (ARF). Upon the attainment of retirement age, the previously-computed age reduction factor...

Sizing of "Mother Ship and Catcher" Concepts for LEO Small Debris Capture

NASA Technical Reports Server (NTRS)

Bacon, John B.

2009-01-01

Most Low Earth Orbit (LEO) debris lies in a limited number of inclination "bands" associated with launch latitudes, or with specific useful orbit inclinations (such as polar orbits). Such narrow inclination bands generally have a uniform spread over all possible Right Ascensions of Ascending Node (RAANs), creating a different orbit plane for nearly every piece of debris. This complicates concept of rendezvous and capture for debris removal. However, a low-orbiting satellite will always phase in RAAN faster than debris objects in higher orbits at the same inclination, potentially solving the problem. Such a base can serve as a single space-based launch facility (a "mother ship") that can tend and then send tiny individual catcher devices for each debris object, as the facility drifts into the same RAAN as the higher object. This presentation will highlight characteristic system requirements of such an architecture, including structural and navigation requirements, power, mass and dV budgets for both the mother ship and the mass-produced common catcher devices that would clean out selected inclination bands. The altitude and inclination regime over which a band is to be cleared, the size distribution of the debris, and the inclusion of additional mission priorities all affect the sizing of the system. It is demonstrated that major LEO hazardous debris reductions can be realized in each band with a single LEO launch of a single mother ship, with simple attached catchers of total mass less than typical commercial LEO launch capability.

Electrical Spin Driving by g -Matrix Modulation in Spin-Orbit Qubits

NASA Astrophysics Data System (ADS)

Crippa, Alessandro; Maurand, Romain; Bourdet, Léo; Kotekar-Patil, Dharmraj; Amisse, Anthony; Jehl, Xavier; Sanquer, Marc; Laviéville, Romain; Bohuslavskyi, Heorhii; Hutin, Louis; Barraud, Sylvain; Vinet, Maud; Niquet, Yann-Michel; De Franceschi, Silvano

2018-03-01

In a semiconductor spin qubit with sizable spin-orbit coupling, coherent spin rotations can be driven by a resonant gate-voltage modulation. Recently, we have exploited this opportunity in the experimental demonstration of a hole spin qubit in a silicon device. Here we investigate the underlying physical mechanisms by measuring the full angular dependence of the Rabi frequency, as well as the gate-voltage dependence and anisotropy of the hole g factor. We show that a g -matrix formalism can simultaneously capture and discriminate the contributions of two mechanisms so far independently discussed in the literature: one associated with the modulation of the g factor, and measurable by Zeeman energy spectroscopy, the other not. Our approach has a general validity and can be applied to the analysis of other types of spin-orbit qubits.

[Core principles of treatment of corneal damage in patients with thyroid eye disease].

PubMed

Grusha, Y O; Ismailova, D S; Sherstneva, L V

To develop a therapeutic approach and to estimate the efficiency of complex treatment of corneal damage in patients with thyroid eye disease (TED). The study enrolled 44 patients (52 eyes) divided into 2 groups depending on the severity of corneal damage. Treatment of those with severe involvement included pathogenetic measures (pulse steroid therapy and/or radiation therapy) and surgery (orbital decompression, eyelid and corneal surgery). As the result of the treatment, orbital inflammation decreased and the state of the cornea improved in all patients. The treatment of corneal damage in patients with TED may differ depending on numerous factors, such as the severity of corneal damage and activity of orbital inflammation. Taking into account the potential danger of corneal involvement, one should make efforts to early detection and management of the risk factors.

The Influence of the Orbital Evolution of Main Belt Asteroids on Their Spin Vectors

NASA Astrophysics Data System (ADS)

Skoglöv, E.; Erikson, A.

2002-11-01

It was found that certain features in the observed spin vector distribution of main belt asteroids can be explained by the differences in the dynamical spin vector evolution between objects with high and low orbital inclinations. In particular, the deficiency of high-inclination objects whose spin vectors are close to the ecliptic plane can be accounted for. The present spin vector distribution of main belt asteroids is due to several factors connected with their collisional and dynamical evolution. In this paper, the influence of the orbital evolution on the spin axis of asteroids is examined in the case of 25 objects with typical main belt orbital evolution and 125 synthetic objects, during an integration over a time period of 1 Myr. This investigation produced the following general results: • The difference between maximum and minimum obliquity increases in an approximately linear fashion with increasing orbital inclination of the studied objects. • The inclination is the major factor influencing the magnitude of the obliquity variation. This variation is generally larger for asteroids with their initial spin vectors located close to the orbital plane. • In general, the regular obliquity differences are relatively insensitive to differences in the shape, composition, and spin rate of the asteroids. The result is compared with the properties of the observed spin vectors for 73 main belt asteroids and good agreement is found between the above results and the existing spin vector distribution.

An investigation of the needs and the design of an orbiting space station with growth capabilities

NASA Technical Reports Server (NTRS)

Dossey, J. R.; Trotti, G.

1977-01-01

An architectural approach to the evolutionary growth of an orbiting space station from a small manned satellite to a fully independent, self-sustainable space colony facility is presented. Social and environmental factors, ease of transportation via the space shuttle, and structural design are considered.

Spacecraft Materials in the Space Flight Environment: International Space Station - May 2002 to May 2007

NASA Technical Reports Server (NTRS)

Golden, John; Lorenz, Mary J.; Alred, John; Koontz, Steven L.; Pedley, Michael

2008-01-01

The performance of ISS spacecraft materials and systems on prolonged exposure to the low-Earth orbit (LEO) space flight is reported in this paper. In-flight data, flight crew observations, and the results of ground-based test and analysis directly supporting programmatic and operational decision-making are presented. The space flight environments definitions (both natural and induced) used for ISS design, material selection, and verification testing are shown, in most cases, to be more severe than the actual flight environment accounting for the outstanding performance of ISS as a long mission duration spacecraft. No significant ISS material or system failures have been attributed to spacecraft-environments interactions. Nonetheless, ISS materials and systems performance data is contributing to our understanding of spacecraft material interactions in the spaceflight environment so as to reduce cost and risk for future spaceflight projects and programs. Orbital inclination (51.6o) and altitude (nominally near 360 km) determine the set of natural environment factors affecting the functional life of materials and systems on ISS. ISS operates in an electrically conducting environment (the F2 region of Earth s ionosphere) with well-defined fluxes of atomic oxygen, other charged and neutral ionospheric plasma species, solar UV, VUV, and x-ray radiation as well as galactic cosmic rays, trapped radiation, and solar cosmic rays (1-4). The LEO micrometeoroid and orbital debris environment is an especially important determinant of spacecraft design and operations (5, 6). The magnitude of several environmental factors varies dramatically with latitude and longitude as ISS orbits the Earth (1-4). The high latitude orbital environment also exposes ISS to higher fluences of trapped energetic electrons, auroral electrons, solar cosmic rays, and galactic cosmic rays (1-4) than would be the case in lower inclination orbits, largely as a result of the overall shape and magnitude of the geomagnetic field (1-4). As a result, ISS exposure to many environmental factors can vary dramatically along a particular orbital ground track, and from one ground track to the next, during any 24-hour period.

Saturnʼs Inner Satellites: Orbits, Masses, and the Chaotic Motion of Atlas from New Cassini Imaging Observations

NASA Astrophysics Data System (ADS)

Cooper, N. J.; Renner, S.; Murray, C. D.; Evans, M. W.

2015-01-01

We present numerically derived orbits and mass estimates for the inner Saturnian satellites, Atlas, Prometheus, Pandora, Janus, and Epimetheus from a fit to 2580 new Cassini Imaging Science Subsystem astrometric observations spanning 2004 February to 2013 August. The observations are provided as machine-readable and Virtual Observatory tables. We estimate G{{M}Atlas} = (0.384 ± 0.001) × 10-3 km3 s-2, a value 13% smaller than the previously published estimate but with an order of magnitude reduction in the uncertainty. We also find G{{M}Prometheus} = (10.677 ± 0.006) × 10-3 km3 s-2, G{{M}Pandora} = (9.133 ± 0.009) × 10-3 km3 s-2, G{{M}Janus} = (126.51 ± 0.03) × 10-3 km3 s-2, and G{{M}Epimetheus} = (35.110 ± 0.009) × 10-3 km3 s-2, consistent with previously published values, but also with significant reductions in uncertainties. We show that Atlas is currently librating in both the 54:53 co-rotation-eccentricity resonance (CER) and the 54:53 inner Lindblad (ILR) resonance with Prometheus, making it the latest example of a coupled CER-ILR system, in common with the Saturnian satellites Anthe, Aegaeon, and Methone, and possibly Neptune's ring arcs. We further demonstrate that Atlas's orbit is chaotic, with a Lyapunov time of ˜10 years, and show that its chaotic behavior is a direct consequence of the coupled resonant interaction with Prometheus, rather than being an indirect effect of the known chaotic interaction between Prometheus and Pandora. We provide an updated analysis of the second-order resonant perturbations involving Prometheus, Pandora, and Epimetheus based on the new observations, showing that these resonant arguments are librating only when Epimetheus is the innermost of the co-orbital pair, Janus and Epimetheus. We also find evidence that the known chaotic changes in the orbits of Prometheus and Pandora are not confined to times of apse anti-alignment.

Planetary quarantine

NASA Technical Reports Server (NTRS)

1971-01-01

Developed methodologies and procedures for the reduction of microbial burden on an assembled spacecraft at the time of encapsulation or terminal sterilization are reported. This technology is required for reducing excessive microbial burden on spacecraft components for the purposes of either decreasing planetary contamination probabilities for an orbiter or minimizing the duration of a sterilization process for a lander.

Dimension Reduction Near Periodic Orbits of Hybrid Systems: Appendix

DTIC Science & Technology

2011-09-07

aplicable to a class of non-smooth systems called hybrid dynamical systems. We relegate a formal definition of the class of hybrid systems under...and highly mobile hexapod robot. IJRR, 20(7):616, 2001. [4] S. Kim, J.E. Clark, and M.R. Cutkosky. iSprawl: Design and tuning for high-speed

Highly Anisotropic Magnon Dispersion in Ca_{2}RuO_{4}: Evidence for Strong Spin Orbit Coupling.

PubMed

Kunkemöller, S; Khomskii, D; Steffens, P; Piovano, A; Nugroho, A A; Braden, M

2015-12-11

The magnon dispersion in Ca_{2}RuO_{4} has been determined by inelastic neutron scattering on single crytals containing 1% of Ti. The dispersion is well described by a conventional Heisenberg model suggesting a local moment model with nearest neighbor interaction of J=8  meV. Nearest and next-nearest neighbor interaction as well as interlayer coupling parameters are required to properly describe the entire dispersion. Spin-orbit coupling induces a very large anisotropy gap in the magnetic excitations in apparent contrast with a simple planar magnetic model. Orbital ordering breaking tetragonal symmetry, and strong spin-orbit coupling can thus be identified as important factors in this system.

Selected tether applications in space: An analysis of five selected concepts

NASA Technical Reports Server (NTRS)

1984-01-01

Ground rules and assumptions; operations; orbit considerations/dynamics; tether system design and dynamics; functional requirements; hardware concepts; and safety factors are examined for five scenarios: tethered effected separation of an Earth bound shuttle from the space station; tether effected orbit boost of a spacecraft (AXAF) into its operational orbit from the shuttle; an operational science/technology platform tether deployed from space station; a tether mediated rendezvous involving an OMV tether deployed from space station to rendezvous with an aerobraked OTV returning to geosynchronous orbit from a payload delivery mission; and an electrodynamic tether used in a dual motor/generator mode to serve as the primary energy storage facility for space station.

Development and evaluation of a hybrid averaged orbit generator

NASA Technical Reports Server (NTRS)

Mcclain, W. D.; Long, A. C.; Early, L. W.

1978-01-01

A rapid orbit generator based on a first-order application of the Generalized Method of Averaging has been developed for the Research and Development (R&D) version of the Goddard Trajectory Determination System (GTDS). The evaluation of the averaged equations of motion can use both numerically averaged and recursively evaluated, analytically averaged perturbation models. These equations are numerically integrated to obtain the secular and long-period motion. Factors affecting efficient orbit prediction are discussed and guidelines are presented for treatment of each major perturbation. Guidelines for obtaining initial mean elements compatible with the theory are presented. An overview of the orbit generator is presented and comparisons with high precision methods are given.

Project ARGO: Gas phase formation in simulated microgravity

NASA Technical Reports Server (NTRS)

Powell, Michael R.; Waligora, James M.; Norfleet, William T.; Kumar, K. Vasantha

1993-01-01

The ARGO study investigated the reduced incidence of joint pain decompression sickness (DCS) encountered in microgravity as compared with an expected incidence of joint pain DCS experienced by test subjects in Earth-based laboratories (unit gravity) with similar protocols. Individuals who are decompressed from saturated conditions usually acquire joint pain DCS in the lower extremities. Our hypothesis is that the incidence of joint pain DCS can be limited by a significant reduction in the tissue gas micronuclei formed by stress-assisted nucleation. Reductions in dynamic and kinetic stresses in vivo are linked to hypokinetic and adynamic conditions of individuals in zero g. We employed the Doppler ultrasound bubble detection technique in simulated microgravity studies to determine quantitatively the degree of gas phase formation in the upper and lower extremities of test subjects during decompression. We found no evidence of right-to-left shunting through pulmonary vasculature. The volume of gas bubble following decompression was examined and compared with the number following saline contrast injection. From this, we predict a reduced incidence of DCS on orbit, although the incidence of predicted mild DCS still remains larger than that encountered on orbit.

Evaluation and analysis of the orbital maneuvering vehicle video system

NASA Technical Reports Server (NTRS)

Moorhead, Robert J., II

1989-01-01

The work accomplished in the summer of 1989 in association with the NASA/ASEE Summer Faculty Research Fellowship Program at Marshall Space Flight Center is summarized. The task involved study of the Orbital Maneuvering Vehicle (OMV) Video Compression Scheme. This included such activities as reviewing the expected scenes to be compressed by the flight vehicle, learning the error characteristics of the communication channel, monitoring the CLASS tests, and assisting in development of test procedures and interface hardware for the bit error rate lab being developed at MSFC to test the VCU/VRU. Numerous comments and suggestions were made during the course of the fellowship period regarding the design and testing of the OMV Video System. Unfortunately from a technical point of view, the program appears at this point in time to be trouble from an expense prospective and is in fact in danger of being scaled back, if not cancelled altogether. This makes technical improvements prohibitive and cost-reduction measures necessary. Fortunately some cost-reduction possibilities and some significant technical improvements that should cost very little were identified.

Potential economic implications of the development of space tourism

NASA Astrophysics Data System (ADS)

Collins, P. Q.; Ashford, D. M.

Scenarios that involve high rates of launch traffic offer the possibility of bringing about major reductions in the cost of space transportation and hence of greatly facilitating the expansion of human activities in space. One scenario that has received little serious attention to date is the development of space tourism (i.e. the provision of pleasure trips in Low Earth Orbit (LEO) to fare-paying passengers) into a major industry. This paper investigates the feasibility of this idea. First, the range of entertainments that could be provided in Earth-orbiting facilities is discussed, and shown to be extensive. A survey is made of published estimates of the expected demand for space tourism at different prices, and an attempt is made to quantify the overall potential. Second, the feasibility of providing the required services at the prices estimated to be acceptable is examined. Two particular levels of activity are assumed, and the scope for cost reductions through economies of scale and appropriate design are considered. It is argued that space tourism has the potential to provide a commercial justification for the development of fully reusable launch vehicles with low operating-costs.

Reductive Outer-Sphere Single Electron Transfer Is an Exception Rather than the Rule in Natural and Engineered Chlorinated Ethene Dehalogenation.

PubMed

Heckel, Benjamin; Cretnik, Stefan; Kliegman, Sarah; Shouakar-Stash, Orfan; McNeill, Kristopher; Elsner, Martin

2017-09-05

Chlorinated ethenes (CEs) such as perchloroethylene, trichloroethylene and dichloroethylene are notorious groundwater contaminants. Although reductive dehalogenation is key to their environmental and engineered degradation, underlying reaction mechanisms remain elusive. Outer-sphere reductive single electron transfer (OS-SET) has been proposed for such different processes as Vitamin B 12 -dependent biodegradation and zerovalent metal-mediated dehalogenation. Compound-specific isotope effect ( 13 C/ 12 C, 37 Cl/ 35 Cl) analysis offers a new opportunity to test these hypotheses. Defined OS-SET model reactants (CO 2 radical anions, S 2- -doped graphene oxide in water) caused strong carbon (ε C = -7.9‰ to -11.9‰), but negligible chlorine isotope effects (ε Cl = -0.12‰ to 0.04‰) in CEs. Greater chlorine isotope effects were observed in CHCl 3 (ε C = -7.7‰, ε Cl = -2.6‰), and in CEs when the exergonicity of C-Cl bond cleavage was reduced in an organic solvent (reaction with arene radical anions in glyme). Together, this points to dissociative OS-SET (SET to a σ* orbital concerted with C-Cl breakage) in alkanes compared to stepwise OS-SET (SET to a π* orbital followed by C-Cl cleavage) in ethenes. The nonexistent chlorine isotope effects of chlorinated ethenes in all aqueous OS-SET experiments contrast strongly with pronounced Cl isotope fractionation in all natural and engineered reductive dehalogenations reported to date suggesting that OS-SET is an exception rather than the rule in environmental transformations of chlorinated ethenes.

Full dose reduction potential of statistical iterative reconstruction for head CT protocols in a predominantly pediatric population

PubMed Central

Mirro, Amy E.; Brady, Samuel L.; Kaufman, Robert. A.

2016-01-01

Purpose To implement the maximum level of statistical iterative reconstruction that can be used to establish dose-reduced head CT protocols in a primarily pediatric population. Methods Select head examinations (brain, orbits, sinus, maxilla and temporal bones) were investigated. Dose-reduced head protocols using an adaptive statistical iterative reconstruction (ASiR) were compared for image quality with the original filtered back projection (FBP) reconstructed protocols in phantom using the following metrics: image noise frequency (change in perceived appearance of noise texture), image noise magnitude, contrast-to-noise ratio (CNR), and spatial resolution. Dose reduction estimates were based on computed tomography dose index (CTDIvol) values. Patient CTDIvol and image noise magnitude were assessed in 737 pre and post dose reduced examinations. Results Image noise texture was acceptable up to 60% ASiR for Soft reconstruction kernel (at both 100 and 120 kVp), and up to 40% ASiR for Standard reconstruction kernel. Implementation of 40% and 60% ASiR led to an average reduction in CTDIvol of 43% for brain, 41% for orbits, 30% maxilla, 43% for sinus, and 42% for temporal bone protocols for patients between 1 month and 26 years, while maintaining an average noise magnitude difference of 0.1% (range: −3% to 5%), improving CNR of low contrast soft tissue targets, and improving spatial resolution of high contrast bony anatomy, as compared to FBP. Conclusion The methodology in this study demonstrates a methodology for maximizing patient dose reduction and maintaining image quality using statistical iterative reconstruction for a primarily pediatric population undergoing head CT examination. PMID:27056425

Space Radiation Cancer Risk Projections for Exploration Missions: Uncertainty Reduction and Mitigation

NASA Technical Reports Server (NTRS)

Cucinotta, Francis; Badhwar, Gautam; Saganti, Premkumar; Schimmerling, Walter; Wilson, John; Peterson, Leif; Dicello, John

2002-01-01

In this paper we discuss expected lifetime excess cancer risks for astronauts returning from exploration class missions. For the first time we make a quantitative assessment of uncertainties in cancer risk projections for space radiation exposures. Late effects from the high charge and energy (HZE) ions present in the galactic cosmic rays including cancer and the poorly understood risks to the central nervous system constitute the major risks. Methods used to project risk in low Earth orbit are seen as highly uncertain for projecting risks on exploration missions because of the limited radiobiology data available for estimating HZE ion risks. Cancer risk projections are described as a product of many biological and physical factors, each of which has a differential range of uncertainty due to lack of data and knowledge. Monte-Carlo sampling from subjective error distributions represents the lack of knowledge in each factor to quantify risk projection overall uncertainty. Cancer risk analysis is applied to several exploration mission scenarios. At solar minimum, the number of days in space where career risk of less than the limiting 3% excess cancer mortality can be assured at a 95% confidence level is found to be only of the order of 100 days.

``Hands-Free'' Asteroid Astrometry

NASA Astrophysics Data System (ADS)

Monet, A. K. B.; Bowell, E.; Monet, D. G.

1997-12-01

How do you undertake a major new astrometric program with no additional financial or personnel resources? The answer: automation! Early in 1992, the authors began a collaboration to obtain astrometric positions for several classes of asteroids (V_lim 17.5 mag) whose orbits required improvement or that were otherwise of special interest. The telescope used for this work is the USNOFS 0.2-meter transit telescope, equipped with a CCD camera. The operation of this instrument has been fully automated (Stone, et al. 1996, AJ, 111, 1721. Nightly observing rosters are constructed from a ranked listing of all asteroids of interest, prepared each month by Bowell. In a typical month, about 200 observations are made, although this number can range from 0 to over 400. Reductions are done automatically as well. A typical 10-hr nightly run can be fully reduced in less than 1/2 hr. Reductions are made on a frame-by-frame basis and positions of the asteroids computed with respect to the USNO-A1.0 catalog (Monet, D.G. 1996, USNO-A1.0 Catalog -- 10 CD-ROM Set, US Naval Observatory.) Observational quality is checked by Bowell, who also recomputes orbits and reports final results to the Minor Planet Center. Orbit residuals hover around 0.3 arcsec. This poster will present a brief overview of the observing and analysis methods, an account of the first five years of results, and a description of planned improvements in instrumentation and analysis techniques.

Trapped Proton Environment in Medium-Earth Orbit (2000-2010)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yue; Friedel, Reinhard Hans; Kippen, Richard Marc

This report describes the method used to derive fluxes of the trapped proton belt along the GPS orbit (i.e., a Medium-Earth Orbit) during 2000 – 2010, a period almost covering a solar cycle. This method utilizes a newly developed empirical proton radiation-belt model, with the model output scaled by GPS in-situ measurements, to generate proton fluxes that cover a wide range of energies (50keV- 6MeV) and keep temporal features as well. The new proton radiation-belt model is developed based upon CEPPAD proton measurements from the Polar mission (1996 – 2007). Comparing to the de-facto standard empirical model of AP8, thismore » model is not only based upon a new data set representative of the proton belt during the same period covered by GPS, but can also provide statistical information of flux values such as worst cases and occurrence percentiles instead of solely the mean values. The comparison shows quite different results from the two models and suggests that the commonly accepted error factor of 2 on the AP8 flux output over-simplifies and thus underestimates variations of the proton belt. Output fluxes from this new model along the GPS orbit are further scaled by the ns41 in-situ data so as to reflect the dynamic nature of protons in the outer radiation belt at geomagnetically active times. Derived daily proton fluxes along the GPS ns41 orbit, whose data files are delivered along with this report, are depicted to illustrate the trapped proton environment in the Medium-Earth Orbit. Uncertainties on those daily proton fluxes from two sources are evaluated: One is from the new proton-belt model that has error factors < ~3; the other is from the in-situ measurements and the error factors could be ~ 5.« less

Low-gravity Orbiting Research Laboratory Environment Potential Impact on Space Biology Research

NASA Technical Reports Server (NTRS)

Jules, Kenol

2006-01-01

One of the major objectives of any orbital space research platform is to provide a quiescent low gravity, preferably a zero gravity environment, to perform fundamental as well as applied research. However, small disturbances exist onboard any low earth orbital research platform. The impact of these disturbances must be taken into account by space research scientists during their research planning, design and data analysis in order to avoid confounding factors in their science results. The reduced gravity environment of an orbiting research platform in low earth orbit is a complex phenomenon. Many factors, among others, such as experiment operations, equipment operation, life support systems and crew activity (if it is a crewed platform), aerodynamic drag, gravity gradient, rotational effects as well as the vehicle structural resonance frequencies (structural modes) contribute to form the overall reduced gravity environment in which space research is performed. The contribution of these small disturbances or accelerations is precisely why the environment is NOT a zero gravity environment, but a reduced acceleration environment. This paper does not discuss other factors such as radiation, electromagnetic interference, thermal and pressure gradient changes, acoustic and CO2 build-up to name a few that affect the space research environment as well, but it focuses solely on the magnitude of the acceleration level found on orbiting research laboratory used by research scientists to conduct space research. For ease of analysis this paper divides the frequency spectrum relevant to most of the space research disciplines into three regimes: a) quasi-steady, b) vibratory and c) transient. The International Space Station is used as an example to illustrate the point. The paper discusses the impact of these three regimes on space biology research and results from space flown experiments are used to illustrate the potential negative impact of these disturbances (accelerations) on space biology research.

Absolute acceleration measurements on STS-50 from the Orbital Acceleration Research Experiment (OARE)

NASA Technical Reports Server (NTRS)

Blanchard, Robert C.; Nicholson, John Y.; Ritter, James R.

1994-01-01

Orbital Acceleration Research Experiment (OARE) data on Space Transportation System (STS)-50 have been examined in detail during a 2-day time period. Absolute acceleration levels have been derived at the OARE location, the orbiter center-of-gravity, and at the STS-50 spacelab Crystal Growth Facility. During the interval, the tri-axial OARE raw telemetered acceleration measurements have been filtered using a sliding trimmed mean filter in order to remove large acceleration spikes (e.g., thrusters) and reduce the noise. Twelve OARE measured biases in each acceleration channel during the 2-day interval have been analyzed and applied to the filtered data. Similarly, the in situ measured x-axis scale factors in the sensor's most sensitive range were also analyzed and applied to the data. Due to equipment problem(s) on this flight, both y- and z-axis sensitive range scale factors were determined in a separate process using orbiter maneuvers and subsequently applied to the data. All known significant low-frequency corrections at the OARE location (i.e., both vertical and horizontal gravity-gradient, and rotational effects) were removed from the filtered data in order to produce the acceleration components at the orbiter center-of-gravity, which are the aerodynamic signals along each body axis. Results indicate that there is a force being applied to the Orbiter in addition to the aerodynamic forces. The OARE instrument and all known gravitational and electromagnetic forces have been reexamined, but none produces the observed effect. Thus, it is tentatively concluded that the orbiter is creating the environment observed. At least part of this force is thought to be due to the Flash Evaporator System.

The size and shape of the near-Earth asteroid belt

NASA Technical Reports Server (NTRS)

Rabinowitz, David L.

1994-01-01

Evidence was recently reported for the existence of a near-Earth belt of small, Earth-approaching asteroids (SEAs) with diameters less than approximately 50 m. This result was based upon observations made with the Spacewatch Telescope of the University of Arizona during the course of an ongoing search for Earth-approaching asteroids. Using a model to describe the effects of observational bias, it was shown that the orbits observed for SEAs are inconsistent with the orbits of Earth approaches larger than approximately 1 km, and imply a relatively high fraction of Earth-like orbits among the SEAs. In this paper, new observations are included and the bias model is extended in order to quantify the number of SEAs within the near-Earth belt and to further constrain their orbital distribution. The calculation shows that relative to larger Earth approachers. SEAs are deficient in Aten-type orbits for which the semimajor axis is less than 1.0 AU. Instead, nearly all SEAs with aphelia less than 1.4 AU (5 +/- 3% of the total population) have perihelia between 0.9 and 1.1 AU, thus defining a near-Earth belt. Those SEAs with aphelia greater than 1.4 AU, however, have a distribution of orbits that are indistinguishable from the orbits of larger Earth approachers. Taking the near-Earth belt into account does not significantly alter the previously determined enhancement in the number of SEAs the previously determined enhancement in the number of SEAs compared to an extrapolation of the number of larger Earth approachers. At approximately 10 m, the enhancement factor is 40 to within a factor of 2. Also, the RMS impact velocity of SEAs with Earth (17 km/sec) is nearly the same as for larger Earth approachers (18 km/sec).

Two-Body Orbit Expansion Due to Time-Dependent Relative Acceleration Rate of the Cosmological Scale Factor

NASA Astrophysics Data System (ADS)

Iorio, Lorenzo

2014-01-01

By phenomenologically assuming a slow temporal variation of the percent acceleration rate S̈S -1 of the cosmic scale factor S(t), it is shown that the orbit of a local binary undergoes a secular expansion. To first order in the power expansion of S̈S -1 around the present epoch t0, a non-vanishing shift per orbit (Δr) of the two-body relative distance r occurs for eccentric trajectories. A general relativistic expression, which turns out to be cubic in the Hubble parameter H0 at the present epoch, is explicitly calculated for it in the case of matter-dominated epochs with Dark Energy. For a highly eccentric Oort comet orbit with period Pb ≈ 31 Myr, the general relativistic distance shift per orbit turns out to be of the order of (Δr) ≈ 70 km. For the Large Magellanic Cloud, assumed on a bound elliptic orbit around the Milky Way, the shift per orbit is of the order of (Δr) ≈ 2-4 pc. Our result has a general validity since it holds in any cosmological model admitting the Hubble law and a slowly varying S̈S-1(t). More generally, it is valid for an arbitrary Hooke-like extra-acceleration whose "elastic" parameter κ is slowly time-dependent, irrespectively of the physical mechanism which may lead to it. The coefficient κ1 of the first-order term of the power expansion of κ(t) can be preliminarily constrained in a model-independent way down to a κ1 ≤ 2 x 10-13 year-3 level from latest Solar System's planetary observations. The radial velocities of the double lined spectroscopic binary ALPHA Cen AB yield κ1 ≤ 10-8 year-3.

Astrometric positions for 18 irregular satellites of giant planets from 23 years of observations

NASA Astrophysics Data System (ADS)

Gomes-Júnior, A. R.; Assafin, M.; Vieira-Martins, R.; Arlot, J.-E.; Camargo, J. I. B.; Braga-Ribas, F.; da Silva Neto, D. N.; Andrei, A. H.; Dias-Oliveira, A.; Morgado, B. E.; Benedetti-Rossi, G.; Duchemin, Y.; Desmars, J.; Lainey, V.; Thuillot, W.

2015-08-01

Context. The irregular satellites of the giant planets are believed to have been captured during the evolution of the solar system. Knowing their physical parameters, such as size, density, and albedo is important for constraining where they came from and how they were captured. The best way to obtain these parameters are observations in situ by spacecrafts or from stellar occultations by the objects. Both techniques demand that the orbits are well known. Aims: We aimed to obtain good astrometric positions of irregular satellites to improve their orbits and ephemeris. Methods: We identified and reduced observations of several irregular satellites from three databases containing more than 8000 images obtained between 1992 and 2014 at three sites (Observatório do Pico dos Dias, Observatoire de Haute-Provence, and European Southern Observatory - La Silla). We used the software Platform for Reduction of Astronomical Images Automatically (PRAIA) to make the astrometric reduction of the CCD frames. The UCAC4 catalog represented the International Celestial Reference System in the reductions. Identification of the satellites in the frames was done through their ephemerides as determined from the SPICE/NAIF kernels. Some procedures were followed to overcome missing or incomplete information (coordinates, date), mostly for the older images. Results: We managed to obtain more than 6000 positions for 18 irregular satellites: 12 of Jupiter, 4 of Saturn, 1 of Uranus (Sycorax), and 1 of Neptune (Nereid). For some satellites the number of obtained positions is more than 50% of what was used in earlier orbital numerical integrations. Conclusions: Comparison of our positions with recent JPL ephemeris suggests there are systematic errors in the orbits for some of the irregular satellites. The most evident case was an error in the inclination of Carme. Position tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A76 and IAU NSDC database at http://www.imcce.fr/nsdcPartially based on observations made at Laboratório Nacional de Astrofísica (LNA), Itajubá-MG, Brazil.Partially based on observations through the ESO runs 079.A-9202(A), 075.C-0154, 077.C-0283 and 079.C-0345.Partially based on observations made at Observatoire de Haute Provence (OHP), 04870 Saint-Michel l'observatoire, France.

Products of the SNPP VIIRS SD Screen Transmittance and the SD BRDFs From Both Yaw Maneuver and Regular On-Orbit Data

NASA Technical Reports Server (NTRS)

Lei, Ning; Xiong, Xiaoxiong

2017-01-01

To ensure data quality, the Earth-observing Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership satellite regularly performs on-orbit radiometric calibration of its 22 spectral bands. The primary radiance source for the calibration of the VIIRS reflective solar bands (RSBs) is a sunlit onboard solar diffuser (SD).During the calibration process, sunlight goes through a perforated plate (the SD screen) and then strikes the SD. The sunlight, scattered off the SD of near-Lambertian property, is used for the calibration. Consequently, the spectral radiance of the scattered sunlight is proportional to the product of the SD screen transmittance and the SD bidirectional reflectance distribution function (BRDF) value at the observation direction. The BRDF value is decomposed to the product of its initial value at launch and a numerical degradation factor that quantifies the decrease from the initial value. The degradation factor is determined by an onboard SD stability monitor (SDSM). During the BRDF degradation factor determination process, the SDSM receives the SD scattered sunlight and the sunlight that goes through another perforated plate at almost the same time. The ratio of the signal strengths from the two observations is used to determine the BRDF degradation factor. Consequently, the RSB radiometric calibration requires the accurate knowledge of the product of the SD screen transmittance and the initial BRDF value as sensed by the RSB and the SDSM detectors. We use both yaw maneuver and a small portion of regular on-orbit data to determine the products.

The Electronic Behavior of Zinc-Finger Protein Binding Sites in the Context of the DNA Extended Ladder Model

NASA Astrophysics Data System (ADS)

Oiwa, Nestor; Cordeiro, Claudette; Heermann, Dieter

2016-05-01

Instead of ATCG letter alignments, typically used in bioinformatics, we propose a new alignment method using the probability distribution function of the bottom of the occupied molecular orbital (BOMO), highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO). We apply the technique to transcription factors with Cys2His2 zinc fingers. These transcription factors search for binding sites, probing for the electronic patterns at the minor and major DNA groves. The eukaryotic Cys2His2 zinc finger proteins bind to DNA ubiquitously at highly conserved domains. They are responsible for gene regulation and the spatial organization of DNA. To study and understand these zinc finger DNA-protein interactions, we use the extended ladder in the DNA model proposed by Zhu, Rasmussen, Balatsky & Bishop (2007) te{Zhu-2007}. Considering one single spinless electron in each nucleotide π-orbital along a double DNA chain (dDNA), we find a typical pattern for the bottom of BOMO, HOMO and LUMO along the binding sites. We specifically looked at two members of zinc finger protein family: specificity protein 1 (SP1) and early grown response 1 transcription factors (EGR1). When the valence band is filled, we find electrons in the purines along the nucleotide sequence, compatible with the electric charges of the binding amino acids in SP1 and EGR1 zinc finger.

Drag-Free Performance of the ST7 Disturbance Reduction System Flight Experiment on the LISA Pathfinder

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; O'Donnell, James R.; Hsu, Oscar H.; Ziemer, John K.; Dunn, Charles E.

2017-01-01

The Space Technology-7 Disturbance Reduction System (DRS) is an experiment package aboard the European Space Agency (ESA) LISA Pathfinder spacecraft. LISA Pathfinder launched from Kourou, French Guiana on December 3, 2015. The DRS is tasked to validate two specific technologies: colloidal micro-Newton thrusters (CMNT) to provide low-noise control capability of the spacecraft, and drag-free controlflight. This validation is performed using highly sensitive drag-free sensors, which are provided by the LISA Technology Package of the European Space Agency. The Disturbance Reduction System is required to maintain the spacecrafts position with respect to a free-floating test mass to better than 10nm/(square root of Hz), along its sensitive axis (axis in optical metrology). It also has a goal of limiting the residual accelerations of any of the two test masses to below 30 x 10(exp -14) (1 + ([f/3 mHz](exp 2))) m/sq s/(square root of Hz), over the frequency range of 1 to 30 mHz.This paper briefly describes the design and the expected on-orbit performance of the control system for the two modes wherein the drag-free performance requirements are verified. The on-orbit performance of these modes are then compared to the requirements, as well as to the expected performance, and discussed.

Analysis of facial bone fractures: An 11-year study of 2,094 patients

PubMed Central

Hwang, Kun; You, Sun Hye

2010-01-01

Purpose: The medical records of these patients were reviewed and analysed to determine the clinical characteristics and treatment of facial bone fractures. Patients and Methods: This is a retrospective study of 2,094 patients with facial bone fractures from various accidents that were treated at the Inha University Hospital from 1996 to 2007. Results: The most common age group was the third decade of life (29%). Males were more common than females (3.98:1). The most common aetiology was violent assault or nonviolent traumatic injury (49.4%). The most common isolated fracture site was the nasal bone (37.7%), followed by the mandible (30%), orbital bones (7.6%), zygoma (5.7%), maxilla (1.3%) and the frontal bone (0.3%). The largest group with complex fractures included the inferior region of the orbital floor and zygomaticomaxilla (14%). Closed reduction was performed in 46.3% of the cases while 39.7% of the cases required open reduction. For open reductions, the most commonly used soft-tissue approach was the intraoral approach (32.3%). The complication rate was 6.4% and the most common complication was hypoesthesia (68.4%) followed by diplopia (25.6%). Conclusion: Long-term collection of epidemiological data regarding facial fractures and concomitant injuries is important for the evaluation of existing preventive measures and useful in the development of new methods of injury prevention and treatment. PMID:20924449

Ultralow-dose computed tomography imaging for surgery of midfacial and orbital fractures using ASIR and MBIR.

PubMed

Widmann, G; Dalla Torre, D; Hoermann, R; Schullian, P; Gassner, E M; Bale, R; Puelacher, W

2015-04-01

The influence of dose reductions on diagnostic quality using a series of high-resolution ultralow-dose computed tomography (CT) scans for computer-assisted planning and surgery including the most recent iterative reconstruction algorithms was evaluated and compared with the fracture detectability of a standard cranial emergency protocol. A human cadaver head including the mandible was artificially prepared with midfacial and orbital fractures and scanned using a 64-multislice CT scanner. The CT dose index volume (CTDIvol) and effective doses were calculated using application software. Noise was evaluated as the standard deviation in Hounsfield units within an identical region of interest in the posterior fossa. Diagnostic quality was assessed by consensus reading of a craniomaxillofacial surgeon and radiologist. Compared with the emergency protocol at CTDIvol 35.3 mGy and effective dose 3.6 mSv, low-dose protocols down to CTDIvol 1.0 mGy and 0.1 mSv (97% dose reduction) may be sufficient for the diagnosis of dislocated craniofacial fractures. Non-dislocated fractures may be detected at CTDIvol 2.6 mGy and 0.3 mSv (93% dose reduction). Adaptive statistical iterative reconstruction (ASIR) 50 and 100 reduced average noise by 30% and 56%, and model-based iterative reconstruction (MBIR) by 93%. However, the detection rate of fractures could not be improved due to smoothing effects. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Orbital Angiogenesis and Lymphangiogenesis in Thyroid Eye Disease: An Analysis of Vascular Growth Factors with Clinical Correlation.

PubMed

Wong, Lindsay L; Lee, Nahyoung Grace; Amarnani, Dhanesh; Choi, Catherine J; Bielenberg, Diane R; Freitag, Suzanne K; D'Amore, Patricia A; Kim, Leo A

2016-09-01

The human orbit is an environment that is vulnerable to inflammation and edema in the setting of autoimmune thyroid disease. Our study investigated the tenet that orbital adipose tissue lacks lymphatic vessels and analyzed the clinicopathologic differences between patients with acute and chronic thyroid eye disease (TED). The underlying molecular mediators of blood and lymphatic vessel formation within the orbital fat also were evaluated. Retrospective cohort study. The study included fat specimens from 26 orbits of 15 patients with TED undergoing orbital decompression. Orbital fat specimens from patients without TED as well as cadaveric orbital fat served as controls. Tissue specimens were processed as formalin-fixed, paraffin-embedded sections or frozen cryosections for immunohistochemistry. Total RNA was extracted and analyzed via quantitative (real-time) reverse-transcription polymerase chain reaction. Clinicopathologic correlation was made by determining the clinical activity score (CAS) of each patient with TED. Samples were examined for vascular and lymphatic markers including podoplanin, lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), and cluster of differentiation 31 (CD31) by immunohistochemistry, as well as for mRNA levels of vascular endothelial growth factor (VEGF), VEGF receptors, semaphorin 3F, neuropilin 1, neuropilin 2, podoplanin, and LYVE-1 by quantitative (real-time) reverse-transcription polymerase chain reaction. Clinicopathologic correlation revealed increased staining of CD31-positive blood vessels in patients with acute TED with a CAS more than 4, as well as rare staining of podoplanin-positive lymphatic vessels within acutely inflamed orbital fat tissue. Additionally, quantitative (real-time) reverse-transcription polymerase chain reaction analysis demonstrated increased expression of VEGF receptor (VEGFR) 2 as well as VEGF signaling molecules VEGF-A, VEGF-C, and VEGF-D. In acute TED, compared with chronic TED and control orbital fat, there is increased blood vessel density, suggesting neovascularization and rare lymphatic vessels suggestive of limited lymphangiogenesis. This proangiogenic and prolymphangiogenic microenvironment is likely the result of the increased expression of VEGFR-2, VEGF-A, VEGF-C, and VEGF-D. These findings imply that orbital edema in acute TED may be mediated, in part, by both the formation of new, immature blood vessels and the formation of lymphatic capillaries that are functionally incapable of draining interstitial fluid. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

NAVIGATION PERFORMANCE IN HIGH EARTH ORBITS USING NAVIGATOR GPS RECEIVER

NASA Technical Reports Server (NTRS)

Bamford, William; Naasz, Bo; Moreau, Michael C.

2006-01-01

NASA GSFC has developed a GPS receiver that can acquire and track GPS signals with sensitivity significantly lower than conventional GPS receivers. This opens up the possibility of using GPS based navigation for missions in high altitude orbit, such as Geostationary Operational Environmental Satellites (GOES) in a geostationary orbit, and the Magnetospheric MultiScale (MMS) Mission, in highly eccentric orbits extending to 12 Earth radii and higher. Indeed much research has been performed to study the feasibility of using GPS navigation in high Earth orbits and the performance achievable. Recently, GSFC has conducted a series of hardware in-the-loop tests to assess the performance of this new GPS receiver in various high Earth orbits of interest. Tracking GPS signals to down to approximately 22-25 dB-Hz, including signals from the GPS transmitter side-lobes, steady-state navigation performance in a geostationary orbit is on the order of 10 meters. This paper presents the results of these tests, as well as sensitivity analysis to such factors as ionosphere masks, use of GPS side-lobe signals, and GPS receiver sensitivity.

Evidence and mechanism of Hurricane Fran-Induced ocean cooling in the Charleston Trough

NASA Astrophysics Data System (ADS)

Xie, Lian; Pietrafesa, L. J.; Bohm, E.; Zhang, C.; Li, X.

Evidence of enhanced sea surface cooling during and following the passage of Hurricane Fran in September 1996 over an oceanic depression located on the ocean margin offshore of Charleston, South Carolina (referred to as the Charleston Trough), [Pietrafesa, 1983] is documented. Approximately 4C° of sea surface temperature (SST) reduction within the Charleston Trough following the passage of Hurricane Fran was estimated based on SST imagery from Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-14 polar orbiting satellite. Simulations using a three-dimensional coastal ocean model indicate that the largest SST reduction occurred within the Charleston Trough. This SST reduction can be explained by oceanic mixing due to storm-induced internal inertia-gravity waves.

Clostridium septicum gas gangrene in the orbit: a case report.

PubMed

Fejes, I; Dégi, R; Végh, M

2013-02-01

Our report presents a case of Clostridium septicum gas gangrene in an unusual, orbital localization. The predisposing factors are typical: colon tumour and lymphatic malignancy. Most probably bacteria from the intestinal flora entered the bloodstream through the compromised intestinal wall and settled in the orbit resulting in the development of an abscess containing gas. At the site of the gas gangrene, an indolent B cell lymphoma was present. After surgery and antibiotic treatment, the patient healed from the C. septicum infection; but subsequently died as a consequence of the tumour.

Mariner 9 mapping science sequence design.

NASA Technical Reports Server (NTRS)

Goldman, A. M., Jr.

1973-01-01

The primary mission of Mariner 9 was to map the Martian surface. This paper discusses in detail the design of the mapping science sequences which were executed by the spacecraft in sixty days and during which over eighty percent of the surface was photographed. The sequence design was influenced by many factors: experimenter scientific objectives, instrument capabilities, spacecraft capabilities, orbit characteristics, and data return rates, which are illustrated graphically. Typical orbits are depicted for each of the three different mapping phases lasting twenty days. Examples of typical orbital sequence plans prepared daily during mission operations are given.

Vehicle systems and payload requirements evaluation. [computer programs for identifying launch vehicle system requirements

NASA Technical Reports Server (NTRS)

Rea, F. G.; Pittenger, J. L.; Conlon, R. J.; Allen, J. D.

1975-01-01

Techniques developed for identifying launch vehicle system requirements for NASA automated space missions are discussed. Emphasis is placed on development of computer programs and investigation of astrionics for OSS missions and Scout. The Earth Orbit Mission Program - 1 which performs linear error analysis of launch vehicle dispersions for both vehicle and navigation system factors is described along with the Interactive Graphic Orbit Selection program which allows the user to select orbits which satisfy mission requirements and to evaluate the necessary injection accuracy.

A Mars orbiter/rover/penetrator mission for the 1984 opportunity

NASA Technical Reports Server (NTRS)

Hastrup, R.; Driver, J.; Nagorski, R.

1977-01-01

A point design mission is described that utilizes the 1984 opportunity to extend the exploration of Mars after the successful Viking operations and provide the additional scientific information needed before conducting a sample return mission. Two identical multi-element spacecraft are employed, each consisting of (1) an orbiter, (2) a Viking-derived landing system that delivers a heavily instrumented, semi-autonomous rover, and (3) three penetrators deployed from the approach trajectory. Selection of the orbit profiles requires consideration of several important factors in order to satisfy all of the mission goals.

Analytical trade study of the STS payload environment. [design analysis and cost estimates for noise reduction devices for space shuttle orbiter payloads

NASA Technical Reports Server (NTRS)

Rader, W. P.; Barrett, S.; Raratono, J.; Payne, K. R.

1976-01-01

The current predicted acoustic environment for the shuttle orbiter payload bay will produce random vibration environments for payload components and subsystems which potentially will result in design, weight and cost penalties if means of protecting the payloads are not developed. Results are presented of a study to develop, through design and cost effectiveness trade studies, conceptual noise suppression device designs for space shuttle payloads. The impact of noise suppression on environmental levels and associated test costs, and on test philosophy for the various payload classes is considered with the ultimate goal of reducing payload test costs. Conclusions and recommendations are presented.

Assessment of candidate-expendable launch vehicles for large payloads

NASA Technical Reports Server (NTRS)

1984-01-01

In recent years the U.S. Air Force and NASA conducted design studies of 3 expendable launch vehicle configurations that could serve as a backup to the space shuttle--the Titan 34D7/Centaur, the Atlas II/Centaur, and the shuttle-derived SRB-X--as well as studies of advanced shuttle-derived launch vehicles with much larger payload capabilities than the shuttle. The 3 candidate complementary launch vehicles are judged to be roughly equivalent in cost, development time, reliability, and payload-to-orbit performance. Advanced shuttle-derived vehicles are considered viable candidates to meet future heavy lift launch requirements; however, they do not appear likely to result in significant reduction in cost-per-pound to orbit.

Photochemically Etched Construction Technology Developed for Digital Xenon Feed Systems

NASA Technical Reports Server (NTRS)

Otsap, Ben; Cardin, Joseph; Verhey, Timothy R.; Rawlin, Vincent K.; Mueller, Juergen; Aadlund, Randall; Kay, Robert; Andrews, Michael

2005-01-01

Electric propulsion systems are quickly emerging as attractive options for primary propulsion in low Earth orbit, in geosynchronous orbit, and on interplanetary spacecraft. The driving force behind the acceptance of these systems is the substantial reduction in the propellant mass that can be realized. Unfortunately, system designers are often forced to utilize components designed for chemical propellants in their electric systems. Although functionally acceptable, these relatively large, heavy components are designed for the higher pressures and mass flow rates required by chemical systems. To fully realize the benefits of electric propulsion, researchers must develop components that are optimized for the low flow rates, critical leakage needs, low pressures, and limited budgets of these emerging systems.

Near-Net Shape Powder Metallurgy Rhenium Thruster

NASA Technical Reports Server (NTRS)

Leonhardt, Todd; Hamister, Mark; Carlen, Jan C.; Biaglow, James; Reed, Brian

2001-01-01

This paper describes the development of a method to produce a near-net shape (NNS) powder metallurgy (PM) rhenium combustion chamber of the size 445 N (100 lbf) used in a high performance liquid apogee engine. These engines are used in low earth Orbit and geostationary orbit for satellite positioning systems. The developments in near-net shape powder metallurgy rhenium combustion chambers reported in this paper will reduce manufacturing cost of the rhenium chambers by 25 percent, and reduce the manufacturing time by 30 to 40 percent. The quantity of rhenium metal powder used to produce a rhenium chamber is reduced by approximately 70 percent and the subsequent reduction in machining schedule and costs is nearly 50 percent.

Hypersonic airbreathing vehicle conceptual design (focus on aero-space plane)

NASA Technical Reports Server (NTRS)

Hunt, James L.; Martin, John G.

1989-01-01

The airbreathing single stage to orbit (SSTO) vehicle design environment is variable-rich, intricately networked and sensitivity intensive. As such, it represents a tremondous technology challenge. Creating a viable design will require sophisticated configuration/synthesis and the synergistic integration of advanced technologies across the discipline spectrum. In design exercises, reductions in the fuel weight-fraction requirements projected for an orbital vehicle concept can result from improvements in aerodynamics/controls, propulsion efficiencies and trajectory optimization; also, gains in the fuel weight-fraction achievable for such a concept can result from improvements in structural design, heat management techniques, and material properties. As these technology advances take place, closure on a viable vehicle design will be realizable.

Investigation of a method for repairing the hot gas system branch 2 of the Symphonie-Satellite MV2 in orbit

NASA Technical Reports Server (NTRS)

Braun, H.

1981-01-01

The failure of all engines on the Symphonie MV2 satellite is attributed to blockage of the oxidizer branch caused by metal salts precipitating and forming a gel which constricts the narrow passage. Laboratory tests and other simulations conducted to observe the behavior of artificially produced jellies on a vacuum show that a removal or at least a reduction of the blockage in the oxidizer branch is possible by evacuation. The greatest blockage appears to occur in the filter. This fact restricts the capability to perform repairs in orbit because the filter installed ahead of the valve cannot by subjected to a vacuum.

Management of the orbital floor in silent sinus syndrome.

PubMed

Thomas, Robert D; Graham, Scott M; Carter, Keith D; Nerad, Jeffrey A

2003-01-01

Enophthalmos in a patient with an opacified hypoplastic maxillary sinus, without sinus symptomatology, describes the silent sinus syndrome. A current trend is to perform endoscopic maxillary antrostomy and orbital floor reconstruction as a single-staged operation. A two-staged approach is performed at our institution to avoid placement of an orbital floor implant in the midst of potential infection and allow for the possibility that enophthalmos and global ptosis may resolve with endoscopic antrostomy alone, obviating the need for orbital floor reconstruction. A retrospective review identified four patients with silent sinus syndrome evaluated between June 1999 and August 2001. Patients presented to our ophthalmology department with ocular asymmetry, and computerized tomography (CT) scanning confirmed the diagnosis in each case. There were three men and one woman, with ages ranging from 27 to 40 years. All patients underwent endoscopic maxillary antrostomy. Preoperative enophthalmos determined by Hertel's measurements ranged from 3 to 4 mm. After endoscopic maxillary antrostomy, the range of reduction in enophthalmos was 1-2 mm. Case 2 had a preoperative CT scan and a CT scan 9 months after left endoscopic maxillary antrostomy. Volumetric analysis of the left maxillary sinus revealed a preoperative volume of 16.85 +/- 0.06 cm3 and a postoperative volume of 19.56 +/- 0.07 cm3. This represented a 16% increase in maxillary sinus volume postoperatively. Orbital floor augmentation was avoided in two patients because of satisfactory improvement in enophthalmos. In the other two patients, orbital reconstruction was performed as a second-stage procedure. There were no complications. Orbital floor augmentation can be offered as a second-stage procedure for patients with silent sinus syndrome. Some patients' enophthalmos may improve with endoscopic antrostomy alone.

Neoclassical theory inside transport barriers in tokamaks

NASA Astrophysics Data System (ADS)

Shaing, K. C.; Hsu, C. T.

2012-02-01

Inside the transport barriers in tokamaks, ion energy losses sometimes are smaller than the value predicted by the standard neoclassical theory. This improvement can be understood in terms of the orbit squeezing theory in addition to the sonic poloidal E ×B Mach number Up,m that pushes the tips of the trapped particles to the higher energy. In general, Up,m also includes the poloidal component of the parallel mass flow speed. These physics mechanisms are the corner stones for the transition theory of the low confinement mode (L-mode) to the high confinement mode (H-mode) in tokamaks. Here, detailed transport fluxes in the banana regime are presented using the parallel viscous forces calculated earlier. It is found, as expected, that effects of orbit squeezing and the sonic Up,m reduce the ion heat conductivity. The former reduces it by a factor of |S|3/2 and the later by a factor of R(Up ,m2)exp(-Up ,m2) with R(Up ,m2), a rational function. Here, S is the orbit squeezing factor.

Two years of on-orbit gallium arsenide performance from the LIPS solar cell panel experiment

NASA Technical Reports Server (NTRS)

Francis, R. W.; Betz, F. E.

1985-01-01

The LIPS on-orbit performance of the gallium arsenide panel experiment was analyzed from flight operation telemetry data. Algorithms were developed to calculate the daily maximum power and associated solar array parameters by two independent methods. The first technique utilizes a least mean square polynomial fit to the power curve obtained with intensity and temperature corrected currents and voltages; whereas, the second incorporates an empirical expression for fill factor based on an open circuit voltage and the calculated series resistance. Maximum power, fill factor, open circuit voltage, short circuit current and series resistance of the solar cell array are examined as a function of flight time. Trends are analyzed with respect to possible mechanisms which may affect successive periods of output power during 2 years of flight operation. Degradation factors responsible for the on-orbit performance characteristics of gallium arsenide are discussed in relation to the calculated solar cell parameters. Performance trends and the potential degradation mechanisms are correlated with existing laboratory and flight data on both gallium arsenide and silicon solar cells for similar environments.

Simplified technique for orbital prosthesis fabrication: a clinical report.

PubMed

Veerareddy, Chandrika; Nair, K Chandrasekharan; Reddy, G Ramaswamy

2012-10-01

Loss of orbital content can cause functional impairment, disfigurement of the face, and psychological distress. Rehabilitation of an orbital defect is a complex task, and if reconstruction by plastic surgery is not possible or not desired by the patient, the defect can be rehabilitated by an orbital prosthesis. The prosthetic rehabilitation in such cases depends on the precisely retained, user-friendly removable maxillofacial prosthesis. Many times, making an impression of the orbital area with an accurate record of surface details can be a difficult procedure. The critical areas are making a facial moulage, mold preparation, and attaching the retention device, particularly when eyeglass frames are used. This case focuses on these hindrance factors. A simple basket was used for the impression tray to obtain the facial moulage. A putty mold was used, and attachment of the prosthesis to a retention device was accomplished with positional distance. This method proves to be an economical and simple way of making an orbital prosthesis. © 2012 by the American College of Prosthodontists.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hellier, Coel; Anderson, D. R.; Smalley, B.

WASP-19b has the shortest orbital period of any known exoplanet, orbiting at only 1.2 times the Roche tidal radius. By observing the Rossiter-McLaughlin effect we show that WASP-19b's orbit is aligned, with {lambda} = 4.{sup 0}6 {+-} 5.{sup 0}2. Using, in addition, a spectroscopic vsin I and the observed rotation period we conclude that the obliquity, {psi}, is less than 20{sup 0}. Further, the eccentricity of the orbit is less than 0.02. We argue that hot Jupiters with orbital periods as short as that of WASP-19b are two orders of magnitude less common than hot Jupiters at the 3-4 daymore » 'pileup'. We discuss the evolution of WASP-19b's orbit and argue that most likely it was first moved to near twice the Roche limit by third-body interactions, and has since spiralled inward to its current location under tidal decay. This is compatible with a stellar tidal-dissipation quality factor, Q'{sub *}, of order 10{sup 7}.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenstreet, S.; Gladman, B.; Ngo, H.

While computing an improved near-Earth object (NEO) steady-state orbital distribution model, we discovered in the numerical integrations the unexpected production of retrograde orbits for asteroids that had originally exited from the accepted main-belt source regions. Our model indicates that {approx}0.1% (a factor of two uncertainty) of the steady-state NEO population (perihelion q < 1.3 AU) is on retrograde orbits. These rare outcomes typically happen when asteroid orbits flip to a retrograde configuration while in the 3:1 mean-motion resonance with Jupiter and then live for {approx}0.001 to 100 Myr. The model predicts, given the estimated near-Earth asteroid (NEA) population, that amore » few retrograde 0.1-1 km NEAs should exist. Currently, there are two known MPC NEOs with asteroidal designations on retrograde orbits which we therefore claim could be escaped asteroids instead of devolatilized comets. This retrograde NEA population may also answer a long-standing question in the meteoritical literature regarding the origin of high-strength, high-velocity meteoroids on retrograde orbits.« less

Method of resolving radio phase ambiguity in satellite orbit determination

NASA Technical Reports Server (NTRS)

Councelman, Charles C., III; Abbot, Richard I.

1989-01-01

For satellite orbit determination, the most accurate observable available today is microwave radio phase, which can be differenced between observing stations and between satellites to cancel both transmitter- and receiver-related errors. For maximum accuracy, the integer cycle ambiguities of the doubly differenced observations must be resolved. To perform this ambiguity resolution, a bootstrapping strategy is proposed. This strategy requires the tracking stations to have a wide ranging progression of spacings. By conventional 'integrated Doppler' processing of the observations from the most widely spaced stations, the orbits are determined well enough to permit resolution of the ambiguities for the most closely spaced stations. The resolution of these ambiguities reduces the uncertainty of the orbit determination enough to enable ambiguity resolution for more widely spaced stations, which further reduces the orbital uncertainty. In a test of this strategy with six tracking stations, both the formal and the true errors of determining Global Positioning System satellite orbits were reduced by a factor of 2.

Propulsion requirements for communications satellites.

NASA Technical Reports Server (NTRS)

Isley, W. C.; Duck, K. I.

1972-01-01

The concept of characteristics thrust is introduced herein as a means of classifying propulsion system tasks related particularly to geosynchronous communications spacecraft. Approximate analytical models are developed to permit estimation of characteristic thrust for injection error corrections, orbit angle re-location, north-south station keeping, east-west station keeping, spin axis precession control, attitude rate damping, and orbit raising applications. Performance assessment factors are then outlined in terms of characteristic power, characteristic weight, and characteristic volume envelope, which are related to the characteristic thrust. Finally, selected performance curves are shown for power as a function of spacecraft weight, including the influence of duty cycle on north-south station keeping, a 90 degree orbit angle re-location in 14 days, and finally comparison of orbit raising tasks from low and intermediate orbits to a final geosynchronous station. Power requirements range from less than 75 watts for north-south station keeping on small payloads up to greater than 15 KW for a 180 day orbit raising mission including a 28.5 degree plane change.

Trim drag reduction concepts for horizontal takeoff single-stage-to-Orbit vehicles

NASA Technical Reports Server (NTRS)

Shaughnessy, John D.; Gregory, Irene M.

1991-01-01

The results of a study to investigate concepts for minimizing trim drag of horizontal takeoff single-stage-to-orbit (SSTO) vehicles are presented. A generic hypersonic airbreathing conical configuration was used as the subject aircraft. The investigation indicates that extreme forward migration of the aerodynamic center as the vehicle accelerates to orbital velocities causes severe aerodynamic instability and trim moments that must be counteracted. Adequate stability can be provided by active control of elevons and rudder, but use of elevons to produce trim moments results in excessive trim drag and fuel consumption. To alleviate this problem, two solution concepts are examined. Active control of the center of gravity (COG) location to track the aerodynamic center decreases trim moment requirements, reduces elevon deflections, and leads to significant fuel savings. Active control of the direction of the thrust vector produces required trim moments, reduces elevon deflections, and also results in significant fuel savings. It is concluded that the combination of active flight control to provide stabilization, (COG) position control to minimize trim moment requirements, and thrust vectoring to generate required trim moments has the potential to significantly reduce fuel consumption during ascent to orbit of horizontal takeoff SSTO vehicles.

Compensation of orbit distortion due to quadrupole motion using feed-forward control at KEK ATF

NASA Astrophysics Data System (ADS)

Bett, D. R.; Charrondière, C.; Patecki, M.; Pfingstner, J.; Schulte, D.; Tomás, R.; Jeremie, A.; Kubo, K.; Kuroda, S.; Naito, T.; Okugi, T.; Tauchi, T.; Terunuma, N.; Burrows, P. N.; Christian, G. B.; Perry, C.

2018-07-01

The high luminosity requirement for a future linear collider sets a demanding limit on the beam quality at the Interaction Point (IP). One potential source of luminosity loss is the motion of the ground itself. The resulting misalignments of the quadrupole magnets cause distortions to the beam orbit and hence an increase in the beam emittance. This paper describes a technique for compensating this orbit distortion by using seismometers to monitor the misalignment of the quadrupole magnets in real-time. The first demonstration of the technique was achieved at the Accelerator Test Facility (ATF) at KEK in Japan. The feed-forward system consisted of a seismometer-based quadrupole motion monitoring system, an FPGA-based feed-forward processor and a stripline kicker plus associated electronics. Through the application of a kick calculated from the position of a single quadruple, the system was able to remove about 80% of the component of the beam jitter that was correlated to the motion of the quadrupole. As a significant fraction of the orbit jitter in the ATF final focus is due to sources other than quadrupole misalignment, this amounted to an approximately 15% reduction in the absolute beam jitter.

Advancement of a 30K W Solar Electric Propulsion System Capability for NASA Human and Robotic Exploration Missions

NASA Technical Reports Server (NTRS)

Smith, Bryan K.; Nazario, Margaret L.; Manzella, David H.

2012-01-01

Solar Electric Propulsion has evolved into a demonstrated operational capability performing station keeping for geosynchronous satellites, enabling challenging deep-space science missions, and assisting in the transfer of satellites from an elliptical orbit Geostationary Transfer Orbit (GTO) to a Geostationary Earth Orbit (GEO). Advancing higher power SEP systems will enable numerous future applications for human, robotic, and commercial missions. These missions are enabled by either the increased performance of the SEP system or by the cost reductions when compared to conventional chemical propulsion systems. Higher power SEP systems that provide very high payload for robotic missions also trade favorably for the advancement of human exploration beyond low Earth orbit. Demonstrated reliable systems are required for human space flight and due to their successful present day widespread use and inherent high reliability, SEP systems have progressively become a viable entrant into these future human exploration architectures. NASA studies have identified a 30 kW-class SEP capability as the next appropriate evolutionary step, applicable to wide range of both human and robotic missions. This paper describes the planning options, mission applications, and technology investments for representative 30kW-class SEP mission concepts under consideration by NASA

Effect of orbital bony decompression for Graves' orbitopathy on the volume of extraocular muscles.

PubMed

Alsuhaibani, Adel H; Carter, Keith D; Policeni, Bruno; Nerad, Jeffrey A

2011-09-01

To evaluate the change in the rectus muscle volume following orbital bony wall decompression for Graves' orbitopathy. We used a computer program (syngo Volume Evaluation) to measure the rectus muscles from the digital preoperative and postoperative orbital CT. Of the 25 patients (20 women and five men; mean age 46 (range 18-64) years) enrolled in the study. A significant increase (mean 0.23 ml (16.5%) of preoperative volume; p=0.005) in the volume of the medial rectus muscle (MRM) was detected postoperatively, whereas no significant changes were found in the volume of the other rectus muscles and between eyes that underwent surgery in the active and inactive phases of the disease. A significant negative association was observed between the time of postoperative CT scans and the change in the MRM volume (p=0.0004) (a mean increase of 68% of preoperative MRM volume for those measured between 3 and 9 months, and a mean decrease in the volume of 50% for those measured between 41 and 50 months). The change in the volume of the MRM may partly explain the variability in the proptosis reduction following orbital decompression.

Mode-Division-Multiplexing of Multiple Bessel-Gaussian Beams Carrying Orbital-Angular-Momentum for Obstruction-Tolerant Free-Space Optical and Millimetre-Wave Communication Links.

PubMed

Ahmed, Nisar; Zhao, Zhe; Li, Long; Huang, Hao; Lavery, Martin P J; Liao, Peicheng; Yan, Yan; Wang, Zhe; Xie, Guodong; Ren, Yongxiong; Almaiman, Ahmed; Willner, Asher J; Ashrafi, Solyman; Molisch, Andreas F; Tur, Moshe; Willner, Alan E

2016-03-01

We experimentally investigate the potential of using 'self-healing' Bessel-Gaussian beams carrying orbital-angular-momentum to overcome limitations in obstructed free-space optical and 28-GHz millimetre-wave communication links. We multiplex and transmit two beams (l = +1 and +3) over 1.4 metres in both the optical and millimetre-wave domains. Each optical beam carried 50-Gbaud quadrature-phase-shift-keyed data, and each millimetre-wave beam carried 1-Gbaud 16-quadrature-amplitude-modulated data. In both types of links, opaque disks of different sizes are used to obstruct the beams at different transverse positions. We observe self-healing after the obstructions, and assess crosstalk and power penalty when data is transmitted. Moreover, we show that Bessel-Gaussian orbital-angular-momentum beams are more tolerant to obstructions than non-Bessel orbital-angular-momentum beams. For example, when obstructions that are 1 and 0.44 the size of the l = +1 beam, are placed at beam centre, optical and millimetre-wave Bessel-Gaussian beams show ~6 dB and ~8 dB reduction in crosstalk, respectively.

Reduction of phase noise in nanowire spin orbit torque oscillators

PubMed Central

Yang, Liu; Verba, Roman; Tiberkevich, Vasil; Schneider, Tobias; Smith, Andrew; Duan, Zheng; Youngblood, Brian; Lenz, Kilian; Lindner, Jürgen; Slavin, Andrei N.; Krivorotov, Ilya N.

2015-01-01

Spin torque oscillators (STOs) are compact, tunable sources of microwave radiation that serve as a test bed for studies of nonlinear magnetization dynamics at the nanometer length scale. The spin torque in an STO can be created by spin-orbit interaction, but low spectral purity of the microwave signals generated by spin orbit torque oscillators hinders practical applications of these magnetic nanodevices. Here we demonstrate a method for decreasing the phase noise of spin orbit torque oscillators based on Pt/Ni80Fe20 nanowires. We experimentally demonstrate that tapering of the nanowire, which serves as the STO active region, significantly decreases the spectral linewidth of the generated signal. We explain the observed linewidth narrowing in the framework of the Ginzburg-Landau auto-oscillator model. The model reveals that spatial non-uniformity of the spin current density in the tapered nanowire geometry hinders the excitation of higher order spin-wave modes, thus stabilizing the single-mode generation regime. This non-uniformity also generates a restoring force acting on the excited self-oscillatory mode, which reduces thermal fluctuations of the mode spatial position along the wire. Both these effects improve the STO spectral purity. PMID:26592432

Mode-Division-Multiplexing of Multiple Bessel-Gaussian Beams Carrying Orbital-Angular-Momentum for Obstruction-Tolerant Free-Space Optical and Millimetre-Wave Communication Links

PubMed Central

Ahmed, Nisar; Zhao, Zhe; Li, Long; Huang, Hao; Lavery, Martin P. J.; Liao, Peicheng; Yan, Yan; Wang, Zhe; Xie, Guodong; Ren, Yongxiong; Almaiman, Ahmed; Willner, Asher J.; Ashrafi, Solyman; Molisch, Andreas F.; Tur, Moshe; Willner, Alan E.

2016-01-01

We experimentally investigate the potential of using ‘self-healing’ Bessel-Gaussian beams carrying orbital-angular-momentum to overcome limitations in obstructed free-space optical and 28-GHz millimetre-wave communication links. We multiplex and transmit two beams (l = +1 and +3) over 1.4 metres in both the optical and millimetre-wave domains. Each optical beam carried 50-Gbaud quadrature-phase-shift-keyed data, and each millimetre-wave beam carried 1-Gbaud 16-quadrature-amplitude-modulated data. In both types of links, opaque disks of different sizes are used to obstruct the beams at different transverse positions. We observe self-healing after the obstructions, and assess crosstalk and power penalty when data is transmitted. Moreover, we show that Bessel-Gaussian orbital-angular-momentum beams are more tolerant to obstructions than non-Bessel orbital-angular-momentum beams. For example, when obstructions that are 1 and 0.44 the size of the l = +1 beam, are placed at beam centre, optical and millimetre-wave Bessel-Gaussian beams show ~6 dB and ~8 dB reduction in crosstalk, respectively. PMID:26926068

Pressure-tuning of bond-directional exchange interactions and magnetic frustration in hyperhoneycomb iridate β-Li 2IrO 3

DOE PAGES

Veiga, L. S. I.; Etter, M.; Glazyrin, K.; ...

2017-10-10

Here, we explore the response of Ir 5d orbitals to pressure in β-Li 2IrO 3, a hyperhoneycomb iridate in proximity to a Kitaev quantum spin-liquid (QSL) ground state. X-ray absorption spectroscopy reveals a reconstruction of the electronic ground state below 2 GPa, the same pressure range where x-ray magnetic circular dichroism shows an apparent collapse of magnetic order. The electronic reconstruction, which manifests a reduction in the effective spin-orbit interaction in 5d orbitals, pushes β-Li 2IrO 3 further away from the pure J eff = 1/2 limit. Although lattice symmetry is preserved across the electronic transition, x-ray diffraction shows amore » highly anisotropic compression of the hyperhoneycomb lattice which affects the balance of bond-directional Ir-Ir exchange interactions driven by spin-orbit coupling at Ir sites. An enhancement of symmetric anisotropic exchange over Kitaev and Heisenberg exchange interactions seen in theoretical calculations that use precisely this anisotropic Ir-Ir bond compression provides one possible route to the realization of a QSL state in this hyperhoneycomb iridate at high pressures.« less

Cross-Track Infrared Sounder Science Data Record Pre-launch Calibration and On-Orbit Validation Plans

NASA Astrophysics Data System (ADS)

Hagan, D. E.; Bingham, G. E.; Predina, J.; Gu, D.; Sabet-Peyman, F.; Wang, C.; de Amici, G.; Plonski, M.; Farrow, S. V.; Hohn, J.; Esplin, M.; Zavyalov, V.; Fish, C. S.; Glumb, R.; Wells, S.; Suwinski, L.; Strong, J.; Behrens, C.; Kilcoyne, H.; Feeley, J.; Kratz, G.; Tremblay, D. A.

2009-12-01

The Cross-Track Infrared Sounder (CrIS) together with the Advanced Technology Microwave Sounder will provide retrievals of atmospheric moisture and temperature profiles for the National Polar-orbiting Operational Environmental Satellite System (NPOESS). The NPOESS is the next generation of low Earth orbiting weather and climate satellites managed by the tri-agency Integrated Program Office, which includes the Department of Commerce, Department of Defense and the National Aeronautics and Space Administration. The CrIS is a Fourier-transform Michelson interferometer covering the spectral range of 3.9 to 15.4 microns (650 to 2550 wavenumbers) developed by ITT under contract to Northrop Grumman Aerospace Systems. The first deployment of the CrIS (Flight Model 1) is scheduled for 2010 on the NPOESS Preparatory Project (NPP) satellite, an early instrument risk reduction component of the NPOESS mission. The analysis and data results from comprehensive TVAC testing of the CrIS FM1 sensor demonstrate a very accurate radiometric and spectral calibration system. We describe instrument performance parameters, and the end-to-end plans and analysis tools for on-orbit verification of sensor characteristics and validation of the SDR radiance products.

Pressure tuning of bond-directional exchange interactions and magnetic frustration in the hyperhoneycomb iridate β -Li2IrO3

NASA Astrophysics Data System (ADS)

Veiga, L. S. I.; Etter, M.; Glazyrin, K.; Sun, F.; Escanhoela, C. A.; Fabbris, G.; Mardegan, J. R. L.; Malavi, P. S.; Deng, Y.; Stavropoulos, P. P.; Kee, H.-Y.; Yang, W. G.; van Veenendaal, M.; Schilling, J. S.; Takayama, T.; Takagi, H.; Haskel, D.

2017-10-01

We explore the response of Ir 5 d orbitals to pressure in β -Li2IrO3 , a hyperhoneycomb iridate in proximity to a Kitaev quantum spin-liquid (QSL) ground state. X-ray absorption spectroscopy reveals a reconstruction of the electronic ground state below 2 GPa, the same pressure range where x-ray magnetic circular dichroism shows an apparent collapse of magnetic order. The electronic reconstruction, which manifests a reduction in the effective spin-orbit interaction in 5 d orbitals, pushes β -Li2IrO3 further away from the pure Jeff=1 /2 limit. Although lattice symmetry is preserved across the electronic transition, x-ray diffraction shows a highly anisotropic compression of the hyperhoneycomb lattice which affects the balance of bond-directional Ir-Ir exchange interactions driven by spin-orbit coupling at Ir sites. An enhancement of symmetric anisotropic exchange over Kitaev and Heisenberg exchange interactions seen in theoretical calculations that use precisely this anisotropic Ir-Ir bond compression provides one possible route to the realization of a QSL state in this hyperhoneycomb iridate at high pressures.

Achieving and Validating the 1-centimeter Orbit: JASON-1 Precision Orbit Determination Using GPS, SLR, DORIS and Altimeter data

NASA Technical Reports Server (NTRS)

Luthcke, Scott B.; Zelensky, Nikita P.; Rowlands, David D.; Lemoine, Frank G.; Williams, Teresa A.

2003-01-01

Jason-1, launched on December 7, 2001, is continuing the time series of centimeter level ocean topography observations as the follow-on to the highly successful TOPEX/POSEIDON (T/P) radar altimeter satellite. The precision orbit determination (POD) is a critical component to meeting the ocean topography goals of the mission. Jason-1 is no exception and has set a 1 cm radial orbit accuracy goal, which represents a factor of two improvement over what is currently being achieved for T/P. The challenge to precision orbit determination (POD) is both achieving the 1 cm radial orbit accuracy and evaluating and validating the performance of the 1 cm orbit. Fortunately, Jason-1 POD can rely on four independent tracking data types including near continuous tracking data from the dual frequency codeless BlackJack GPS receiver. In addition, to the enhanced GPS receiver, Jason-1 carries significantly improved SLR and DORIS tracking systems along with the altimeter itself. We demonstrate the 1 cm radial orbit accuracy goal has been achieved using GPS data alone in a reduced dynamic solution. It is also shown that adding SLR data to the GPS-based solutions improves the orbits even further. In order to assess the performance of these orbits it is necessary to process all of the available tracking data (GPS, SLR, DORIS and altimeter crossover differences) as either dependent or independent of the orbit solutions. It was also necessary to compute orbit solutions using various combinations of the four available tracking data in order to independently assess the orbit performance. Towards this end, we have greatly improved orbits determined solely from SLR+DORIS data by applying the reduced dynamic solution strategy. In addition, we have computed reduced dynamic orbits based on SLR, DORIS and crossover data that are a significant improvement over the SLR and DORIS based dynamic solutions. These solutions provide the best performing orbits for independent validation of the GPS-based reduced dynamic orbits.

[Evaluation of the risk of delayed adverse effects of chronic combined exposure to radiation and chemical factors with the purpose to ensure safety in orbital and exploration space missions].

PubMed

Shafirkin, A V; Mukhamedieva, L N; Tatarkin, S V; Barantseva, M Iu

2012-01-01

The work had the aim to anatomize the existing issues with providing safety in extended orbital and exploration missions for ensuing estimation of actual values of the total radiation risk for the crew, and risks of other delayed effects of simultaneous exposure to ionizing radiation and chemical pollutants in cabin air, and a number of other stressful factors inevitable in space flight. The flow of chronic experiments for separate and combined studies with reproduction of air makeup and radiation doses in actual orbital and predicted exploration missions is outlined. To set safety limits, new approaches should be applied to the description of gradual norm degradation to pathologies in addition to several generalized quantitative indices of adaptation and straining of the regulatory systems, as well as of effectiveness of the compensatory body reserve against separate and combined exposure.

Full Wave Function Optimization with Quantum Monte Carlo and Its Effect on the Dissociation Energy of FeS.

PubMed

Haghighi Mood, Kaveh; Lüchow, Arne

2017-08-17

Diffusion quantum Monte Carlo calculations with partial and full optimization of the guide function are carried out for the dissociation of the FeS molecule. For the first time, quantum Monte Carlo orbital optimization for transition metal compounds is performed. It is demonstrated that energy optimization of the orbitals of a complete active space wave function in the presence of a Jastrow correlation function is required to obtain agreement with the experimental dissociation energy. Furthermore, it is shown that orbital optimization leads to a 5 Δ ground state, in agreement with experiments but in disagreement with other high-level ab initio wave function calculations which all predict a 5 Σ + ground state. The role of the Jastrow factor in DMC calculations with pseudopotentials is investigated. The results suggest that a large Jastrow factor may improve the DMC accuracy substantially at small additional cost.

Effect of element size on the solution accuracies of finite-element heat transfer and thermal stress analyses of space shuttle orbiter

NASA Technical Reports Server (NTRS)

Ko, William L.; Olona, Timothy

1987-01-01

The effect of element size on the solution accuracies of finite-element heat transfer and thermal stress analyses of space shuttle orbiter was investigated. Several structural performance and resizing (SPAR) thermal models and NASA structural analysis (NASTRAN) structural models were set up for the orbiter wing midspan bay 3. The thermal model was found to be the one that determines the limit of finite-element fineness because of the limitation of computational core space required for the radiation view factor calculations. The thermal stresses were found to be extremely sensitive to a slight variation of structural temperature distributions. The minimum degree of element fineness required for the thermal model to yield reasonably accurate solutions was established. The radiation view factor computation time was found to be insignificant compared with the total computer time required for the SPAR transient heat transfer analysis.

A new pattern in Saturn's D ring created in late 2011

NASA Astrophysics Data System (ADS)

Hedman, M. M.; Showalter, M. R.

2016-11-01

Images obtained by the Cassini spacecraft between 2012 and 2015 reveal a periodic brightness variation in a region of Saturn's D ring that previously appeared to be rather featureless. Furthermore, the intensity and radial wavenumber of this pattern have decreased steadily with time since it was first observed. Based on analogies with similar structures elsewhere in the D ring, we propose that this structure was created by some event that disturbed the orbital motions of the ring particles, giving them finite orbital eccentricities and initially aligned pericenters. Differential orbital precession then transformed this structure into a spiral pattern in the ring's optical depth that became increasingly tightly wound over time. The observed trends in the pattern's radial wavenumber are roughly consistent with this basic model, and also indicate that the ring-disturbing event occurred in early December 2011. Similar events in 1979 may have generated the periodic patterns seen in this same region by the Voyager spacecraft. The 2011 event could have been caused by debris striking the rings, or by a disturbance in the planet's electromagnetic environment. The rapid reduction in the intensity of the brightness variations over the course of just a few years indicates that some process is either damping orbital eccentricities in this region or causing the orbital pericenters of particles with the same semi-major axis to become misaligned.

Fuel-optimal, low-thrust transfers between libration point orbits

NASA Astrophysics Data System (ADS)

Stuart, Jeffrey R.

Mission design requires the efficient management of spacecraft fuel to reduce mission cost, increase payload mass, and extend mission life. High efficiency, low-thrust propulsion devices potentially offer significant propellant reductions. Periodic orbits that exist in a multi-body regime and low-thrust transfers between these orbits can be applied in many potential mission scenarios, including scientific observation and communications missions as well as cargo transport. In light of the recent discovery of water ice in lunar craters, libration point orbits that support human missions within the Earth-Moon region are of particular interest. This investigation considers orbit transfer trajectories generated by a variable specific impulse, low-thrust engine with a primer-vector-based, fuel-optimizing transfer strategy. A multiple shooting procedure with analytical gradients yields rapid solutions and serves as the basis for an investigation into the trade space between flight time and consumption of fuel mass. Path and performance constraints can be included at node points along any thrust arc. Integration of invariant manifolds into the design strategy may also yield improved performance and greater fuel savings. The resultant transfers offer insight into the performance of the variable specific impulse engine and suggest novel implementations of conventional impulsive thrusters. Transfers incorporating invariant manifolds demonstrate the fuel savings and expand the mission design capabilities that are gained by exploiting system symmetry. A number of design applications are generated.

R suite for the Reduction and Analysis of UFO Orbit Data

NASA Astrophysics Data System (ADS)

Campbell-Burns, P.; Kacerek, R.

2016-02-01

This paper presents work undertaken by UKMON to compile a suite of simple R scripts for the reduction and analysis of meteor data. The application of R in this context is by no means an original idea and there is no doubt that it has been used already in many reports to the IMO. However, we are unaware of any common libraries or shared resources available to the meteor community. By sharing our work we hope to stimulate interest and discussion. Graphs shown in this paper are illustrative and are based on current data from both EDMOND and UKMON.

Gossamer sails for satellite de-orbiting: Mission analysis and applications

NASA Astrophysics Data System (ADS)

Visagie, Lourens

The requirement for satellites to have a mitigation or deorbiting strategy has been brought about by the ever increasing amount of debris in Earth orbit. Studies have been used to formulate space debris mitigation guidelines, and adherence to these guidelines would theoretically lead to a sustainable environment for future satellite launches and operations. Deployable sail designs that have traditionally been studied and used for solar sails are increasingly being considered for de-orbit applications. Such sail designs benefit from a low mass and large surface area to achieve efficient thrust. A sail has the potential to be used for drag augmentation, to reduce the time until re-entry, or as an actual solar sail - to deorbit from higher orbits. A number of concerns for sail-based deorbiting are addressed in this thesis. One of these concerns is the ability of a sail to mitigate the risk of a collision. By investigating both the area-time-product (ATP) and collision probability it is shown that a gossamer sail used for deorbiting will lead to a reduction in overall collision risk. The extent to which the risk is reduced is investigated and the contributing factors assessed. Another concern is that of attitude stability of a host satellite and deorbit sail. One of the biggest benefits of drag augmentation is the fact that it can achieve the deorbiting goal with an inactive host satellite. There is thus no need for active control, communications or power after deployment. But a simple 2D sail will lose efficiency as a deorbiting device if it is not optimally oriented. It was found in this research that it is possible for a host satellite with attached sail to maintain a stable attitude under passive conditions in a drag deorbiting mode. Finally, in order to fully prove the benefit of sail-based deorbiting it is shown that in certain scenarios this alternative might be more efficient at reducing collision risk, weighs less, and has less operational requirements than other alternatives such as electrodynamic tethers and conventional propulsion. This thesis aims to cover the fundamental concerns of a sail-based deorbiting device at mission level by firstly addressing the mission analysis aspects and then applying it to specific scenarios. The theory and methods required to perform mission analysis for a sail-based deorbiting strategy is presented. These methods are then used to demonstrate passive attitude stability for a drag sail, and reduction in collision risk, both in terms of the Area-Time-Product and collision probability. The analysis results are then further applied by identifying scenarios to which the proposed deorbiting device applies, and then performing a meaningful comparison by analysing a number of case studies. The application is made more concrete by comparison with likely contenders - traditional propulsion, electrodynamic tethers and an inflatable sphere.

Improving the Estimates of International Space Station (ISS) Induced K-Factor Failure Rates for On-Orbit Replacement Unit (ORU) Supportability Analyses

NASA Technical Reports Server (NTRS)

Anderson, Leif F.; Harrington, Sean P.; Omeke, Ojei, II; Schwaab, Douglas G.

2009-01-01

This is a case study on revised estimates of induced failure for International Space Station (ISS) on-orbit replacement units (ORUs). We devise a heuristic to leverage operational experience data by aggregating ORU, associated function (vehicle sub -system), and vehicle effective' k-factors using actual failure experience. With this input, we determine a significant failure threshold and minimize the difference between the actual and predicted failure rates. We conclude with a discussion on both qualitative and quantitative improvements the heuristic methods and potential benefits to ISS supportability engineering analysis.

Pulsed Accretion in the T Tauri Binary TWA 3A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tofflemire, Benjamin M.; Mathieu, Robert D.; Herczeg, Gregory J.

TWA 3A is the most recent addition to a small group of young binary systems that both actively accrete from a circumbinary disk and have spectroscopic orbital solutions. As such, it provides a unique opportunity to test binary accretion theory in a well-constrained setting. To examine TWA 3A’s time-variable accretion behavior, we have conducted a two-year, optical photometric monitoring campaign, obtaining dense orbital phase coverage (∼20 observations per orbit) for ∼15 orbital periods. From U -band measurements we derive the time-dependent binary mass accretion rate, finding bursts of accretion near each periastron passage. On average, these enhanced accretion events evolvemore » over orbital phases 0.85 to 1.05, reaching their peak at periastron. The specific accretion rate increases above the quiescent value by a factor of ∼4 on average but the peak can be as high as an order of magnitude in a given orbit. The phase dependence and amplitude of TWA 3A accretion is in good agreement with numerical simulations of binary accretion with similar orbital parameters. In these simulations, periastron accretion bursts are fueled by periodic streams of material from the circumbinary disk that are driven by the binary orbit. We find that TWA 3A’s average accretion behavior is remarkably similar to DQ Tau, another T Tauri binary with similar orbital parameters, but with significantly less variability from orbit to orbit. This is only the second clear case of orbital-phase-dependent accretion in a T Tauri binary.« less

Preliminary OARE absolute acceleration measurements on STS-50

NASA Technical Reports Server (NTRS)

Blanchard, Robert C.; Nicholson, John Y.; Ritter, James

1993-01-01

On-orbit Orbital Acceleration Research Experiment (OARE) data on STS-50 was examined in detail during a 2-day time period. Absolute acceleration levels were derived at the OARE location, the orbiter center-of-gravity, and at the STS-50 spacelab Crystal Growth Facility. The tri-axial OARE raw acceleration measurements (i.e., telemetered data) during the interval were filtered using a sliding trimmed mean filter in order to remove large acceleration spikes (e.g., thrusters) and reduce the noise. Twelve OARE measured biases in each acceleration channel during the 2-day interval were analyzed and applied to the filtered data. Similarly, the in situ measured x-axis scale factors in the sensor's most sensitive range were also analyzed and applied to the data. Due to equipment problem(s) on this flight, both y- and z- axis sensitive range scale factors were determined in a separate process (using the OARE maneuver data) and subsequently applied to the data. All known significant low-frequency corrections at the OARE location (i.e., both vertical and horizontal gravity-gradient, and rotational effects) were removed from the filtered data in order to produce the acceleration components at the orbiter's center-of-gravity, which are the aerodynamic signals along each body axes. Results indicate that there is a force of unknown origin being applied to the Orbiter in addition to the aerodynamic forces. The OARE instrument and all known gravitational and electromagnetic forces were reexamined, but none produce the observed effect. Thus, it is tentatively concluded that the Orbiter is creating the environment observed.

Orbit Stability of OSIRIS-REx in the Vicinity of Bennu Using a High-Fidelity Solar Radiation Model

NASA Technical Reports Server (NTRS)

Williams, Trevor W.; Hughes, Kyle M.; Mashiku, Alinda K.; Longuski, James M.

2015-01-01

Solar radiation pressure is one of the largest perturbing forces on the OSIRISRex trajectory as it orbits the asteroid Bennu. In this work, we investigate how forces due to solar radiation perturb the OSIRIS-REx trajectory in a high-fidelity model. The model accounts for Bennu's non-spherical gravity field, third-body gravity forces from the Sun and Jupiter, as well as solar radiation forces acting on a simplified spacecraft model. Such high-fidelity simulations indicate significant solar radiation pressure perturbations from the nominal orbit. Modifications to the initial design of the nominal orbit are found using a variation of parameters approach that reduce the perturbation in eccentricity by a factor of one-half.

Study of the decay and recovery of orbiting artificial space objects

NASA Technical Reports Server (NTRS)

1976-01-01

The reentry of earth-orbiting space objects unconsumed in the atmosphere represents a potential hazard to populated areas of the earth. The Smithsonian Astrophysical Observatory has conducted a program called Moonwatch, whose purposes were to observe orbiting artificial satellites and reentries of space objects and, if possible, to recover and analyze reentered pieces. In addition, through observations of low-perigee objects, data obtained by Moonwatchers have been instrumental in defining some of the factors affecting satellite decay. The objectives of the program are presented, and the problems that enter into satellite-orbit and decay predictions are addressed. Moonwatchers contributed substantially to increasing an overall prediction capability, and some of the specific achievements over the 6-year period are cited.

A new Space Station power system

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

1988-01-01

A new concept for a Space Station power system is proposed which reduces the drag effect of the solar panels and eliminates eclipsing by the Earth. The solar generator is physically separated from the Space Station, and power transmitted to the station by a microwave beam. The power station can thus be placed high enough that drag is not a significant factor. For a resonant orbit where the ratio of periods s:p is a ratio of odd integers, and the orbital planes nearly perpendicular, an orbit can be chosen such that the line of sight is never blocked if the lower orbit has an altitude greater than calculatable mininum. For the 1:3 resonance, this minimum altitude is 0.5 r(e). Finally, by placing the power station into a sun-synchronous orbit, it can be made to avoid shadowing by the Earth, thus providing continuous power.

International Space Station End-of-Life Probabilistic Risk Assessment

NASA Technical Reports Server (NTRS)

Duncan, Gary

2014-01-01

Although there are ongoing efforts to extend the ISS life cycle through 2028, the International Space Station (ISS) end-of-life (EOL) cycle is currently scheduled for 2020. The EOL for the ISS will require de-orbiting the ISS. This will be the largest manmade object ever to be de-orbited, therefore safely de-orbiting the station will be a very complex problem. This process is being planned by NASA and its international partners. Numerous factors will need to be considered to accomplish this such as target corridors, orbits, altitude, drag, maneuvering capabilities, debris mapping etc. The ISS EOL Probabilistic Risk Assessment (PRA) will play a part in this process by estimating the reliability of the hardware supplying the maneuvering capabilities. The PRA will model the probability of failure of the systems supplying and controlling the thrust needed to aid in the de-orbit maneuvering.

Natural orbital environment definition guidelines for use in aerospace vehicle development

NASA Technical Reports Server (NTRS)

Anderson, B. Jeffrey (Editor); Smith, Robert E. (Compiler)

1994-01-01

This document provides definitions of the natural near-Earth space environment suitable for use in the initial development/design phase of any space vehicle. The natural environment includes the neutral atmosphere, plasma, charged particle radiation, electromagnetic radiation (EMR), meteoroids, orbital debris, magnetic field, physical and thermal constants, and gravitational field. Communications and other unmanned satellites operate in geosynchronous-Earth orbit (GEO); therefore, some data are given for GEO, but emphasis is on altitudes from 200 km to 1000 km (low-Earth orbit (LEO)). This document does not cover the induced environment of other effects resulting from presence of the space vehicle. Manmade factors are included as part of the ambient natural environment; i.e., orbital debris and radio frequency (RF) noise generated on Earth, because they are not caused by the presence of the space vehicle but form part of the ambient environment that the space vehicle experiences.

STS mission duration enhancement study: (orbiter habitability)

NASA Technical Reports Server (NTRS)

Carlson, A. D.

1979-01-01

Habitability improvements for early flights that could be implemented with minimum impact were investigated. These included: (1) launching the water dispenser in the on-orbit position instead of in a locker; (2) the sleep pallet concept; and (3) suction cup foot restraints. Past studies that used volumetric terms and requirements for crew size versus mission duration were reviewed and common definitions of key habitability terms were established. An accurately dimensioned drawing of the orbiter mid-deck, locating all of the known major elements was developed. Finally, it was established that orbiter duration and crew size can be increased with minimum modification and impact to the crew module. Preliminary concepts of the aft med-deck, external versions of expanded tunnel adapters (ETA), and interior concepts of ETA-3 were developed and comparison charts showing the various factors of volume, weight, duration, size, impact to orbiter, and number of sleep stations were generated.

Optimal aeroassisted coplanar orbital transfer using an energy model

NASA Technical Reports Server (NTRS)

Halyo, Nesim; Taylor, Deborah B.

1989-01-01

The atmospheric portion of the trajectories for the aeroassisted coplanar orbit transfer was investigated. The equations of motion for the problem are expressed using reduced order model and total vehicle energy, kinetic plus potential, as the independent variable rather than time. The order reduction is achieved analytically without an approximation of the vehicle dynamics. In this model, the problem of coplanar orbit transfer is seen as one in which a given amount of energy must be transferred from the vehicle to the atmosphere during the trajectory without overheating the vehicle. An optimal control problem is posed where a linear combination of the integrated square of the heating rate and the vehicle drag is the cost function to be minimized. The necessary conditions for optimality are obtained. These result in a 4th order two-point-boundary-value problem. A parametric study of the optimal guidance trajectory in which the proportion of the heating rate term versus the drag varies is made. Simulations of the guidance trajectories are presented.

An integral nuclear power and propulsion system concept

NASA Astrophysics Data System (ADS)

Choong, Phillip T.; Teofilo, Vincent L.; Begg, Lester L.; Dunn, Charles; Otting, William

An integral space power concept provides both the electrical power and propulsion from a common heat source and offers superior performance capabilities over conventional orbital insertion using chemical propulsion systems. This paper describes a hybrid (bimodal) system concept based on a proven, inherently safe solid fuel form for the high temperature reactor core operation and rugged planar thermionic energy converter for long-life steady state electric power production combined with NERVA-based rocket technology for propulsion. The integral system is capable of long-life power operation and multiple propulsion operations. At an optimal thrust level, the integral system can maintain the minimal delta-V requirement while minimizing the orbital transfer time. A trade study comparing the overall benefits in placing large payloads to GEO with the nuclear electric propulsion option shows superiority of nuclear thermal propulsion. The resulting savings in orbital transfer time and the substantial reduction of overall lift requirement enables the use of low-cost launchers for several near-term military satellite missions.

X-40A Free Flight #5

NASA Technical Reports Server (NTRS)

2001-01-01

X-40A Free Flight #5. The unpowered X-40A, an 85 percent scale risk reduction version of the proposed X-37, proved the capability of an autonomous flight control and landing system in a series of glide flights at NASA's Dryden Flight Research Center in California. NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the X-37 project. At Dryden, the X-40A underwent a series of ground and air tests to reduce possible risks to the larger X-37, including drop tests from a helicopter to check guidance and navigation systems planned for use in the X-37. The X-37 is designed to demonstrate technologies in the orbital and reentry environments for next-generation reusable launch vehicles that will increase both safety and reliability, while reducing launch costs from $10,000 per pound to $1,000 per pound. The X-37, carried into orbit by the Space Shuttle, is planned to fly two orbital missions to test reusable launch vehicle technologies.

Laser Shearographic Inspection for Debonds in Sprayed On Foam Insulation (SOFI)

NASA Technical Reports Server (NTRS)

Adams, F. W.; Hooker, J.; Simmons, S.

1997-01-01

Preliminary results of shearographic inspections of the test panels simulating the Space Shuttle's external tank (ET) spray on foam insulation (SOFI) are presented. Debonding of SOFI may introduce flight debris that may damage the orbiter's thermal protection system (TPS) exposing the orbiter (as well as the ET) to thermal loading. It is estimated that 90 percent of the TPS damage on the orbiter's 'belly' results from debonded SOFI during ascent. A series of test panels were fabricated, with programmed debonds of different geometries and sizes, to determine the sensitivity of shearography as a function of debond size, SOFI thickness,'and vacuum excitation. Results show that a Probability of Detection (POD) of 0.95 or better can be expected for debonds with a diameter equal to the SOFI thickness as less than 0.4-psi pressure reduction. More testing will be required to validate the laser shearography imaging process for certifying its use in nondestructive evaluation (NDE) of Space Shuttle space flight components.

Electric propulsion for lunar exploration and lunar base development

NASA Technical Reports Server (NTRS)

Palaszewski, Bryan

1992-01-01

Using electric propulsion to deliver materials to lunar orbit for the development and construction of a lunar base was investigated. Because the mass of the base and its life-cycle resupply mass are large, high specific impulse propulsion systems may significantly reduce the transportation system mass and cost. Three electric propulsion technologies (arcjet, ion, and magnetoplasmadynamic (MPD) propulsion) were compared with oxygen/hydrogen propulsion for a lunar base development scenario. Detailed estimates of the orbital transfer vehicles' (OTV's) masses and their propellant masses are presented. The fleet sizes for the chemical and electric propulsion systems are estimated. Ion and MPD propulsion systems enable significant launch mass savings over O2/H2 propulsion. Because of the longer trip time required for the low-thrust OTV's, more of them are required to perform the mission model. By offloading the lunar cargo from the manned O2/H2 OTV missions onto the electric propulsion OTV's, a significant reduction of the low Earth orbit (LEO) launch mass is possible over the 19-year base development period.

The 3D-HST Survey: An Introduction

NASA Astrophysics Data System (ADS)

Momcheva, Ivelina G.; Van Dokkum, P. G.; Brammer, G.; Franx, M.; Skelton, R.; Lundgren, B.; Whitaker, K. E.; 3D-HST Team

2013-01-01

3D-HST is a near-IR spectroscopic survey with the Hubble Space Telescope designed to study galaxy evolution at 11. In this talk, I will review the observational details, reduction pipeline, data quality and the wide range of public data products, including added-value photometric and spectroscopic catalogs. Data from the 3D-HST survey are non-proprietary and are useful for a wide variety of science investigations. Our first public data release will be in early 2013 and we would like to advertise this unique data set to the community.

Solar rocket system concept analysis

NASA Technical Reports Server (NTRS)

Boddy, J. A.

1980-01-01

The use of solar energy to heat propellant for application to Earth orbital/planetary propulsion systems is of interest because of its performance capabilities. The achievable specific impulse values are approximately double those delivered by a chemical rocket system, and the thrust is at least an order of magnitude greater than that produced by a mercury bombardment ion propulsion thruster. The primary advantage the solar heater thruster has over a mercury ion bombardment system is that its significantly higher thrust permits a marked reduction in mission trip time. The development of the space transportation system, offers the opportunity to utilize the full performance potential of the solar rocket. The requirements for transfer from low Earth orbit (LEO) to geosynchronous equatorial orbit (GEO) was examined as the return trip, GEO to LEO, both with and without payload. Payload weights considered ranged from 2000 to 100,000 pounds. The performance of the solar rocket was compared with that provided by LO2-LH2, N2O4-MMH, and mercury ion bombardment systems.

Future earth orbit transportation systems/technology implications

NASA Technical Reports Server (NTRS)

Henry, B. Z.; Decker, J. P.

1976-01-01

Assuming Space Shuttle technology to be state-of-the-art, projected technological advances to improve the capabilities of single-stage-to-orbit (SSTO) derivatives are examined. An increase of about 30% in payload performance can be expected from upgrading the present Shuttle system through weight and drag reductions and improvements in the propellants and engines. The ODINEX (Optimal Design Integration Executive Computer Program) program has been used to explore design options. An advanced technology SSTO baseline system derived from ODINEX analysis has a conventional wing-body configuration using LOX/LH engines, three with two-position nozzles with expansion ratios of 40 and 200 and four with fixed nozzles with an expansion ratio of 40. Two assisted-takeoff approaches are under consideration in addition to a concept in which the orbital vehicle takes off empty using airbreathing propulsion and carries out a rendezvous with two large cryogenic tankers carrying propellant at an altitude of 6100 m. Further approaches under examination for propulsion, aerothermodynamic design, and design integration are described.

On the reduction of dynamic loads during actuation of separation devices of advanced orbital astrophysical observatories

NASA Astrophysics Data System (ADS)

Efanov, V. V.; Birukov, A. S.; Demenko, O. G.

2014-12-01

The paper gives a brief description of pyromechanical and detonation devices separating spacecraft (SC) from the upper stage. Causes of significant shock loads in the design and equipment are explained. Technical solutions to reduce these loads implemented in future SC using the mechanism of gas-dynamic and mechanical damping are described.

KSC-2009-2946

NASA Image and Video Library

2009-05-05

VANDENBERG AIR FORCE BASE, Calif. – A United Launch Alliance Delta II rocket blasts off from Space Launch Complex-2 launch pad at Vandenberg AFB, Calif., at 1:24 p.m. PDT. The Delta II successfully carried the Missile Defense Agency's Space Tracking and Surveillance System (STSS) Advanced Technology Risk Reduction (ATRR) payload into orbit. Photo by Carleton Bailie, United Launch Alliance.

Blepharoplasty techniques in the management of orbito-temporal neurofibromatosis.

PubMed

Li, Jin; Lin, Ming; Shao, Chunyi; Ge, Shengfang; Fan, Xianqun

2014-11-01

We aimed to present blepharoplasty techniques we used for severe orbito-temporal neurofibromatosis (NF). A retrospective noncomparative single-center case study was undertaken on patients with orbito-temporal NF. Twenty-two patients with orbito-temporal NF treated at the Department of Ophthalmology of Shanghai Ninth People's Hospital between 2007 and 2011 participated in the study. They underwent a standard ophthalmologic assessment for orbito-temporal NF involving both the orbito-temporal soft tissue and bony orbits. The orbits were examined with three-dimensional computed tomography (CT) and all 22 patients underwent tumor debulking, blepharoplasty, and orbital reconstruction. We modified the conventional procedures. Our reconstructive techniques included eyelid reduction; lateral canthal reattachment; for patients with collapse of the lateral orbital margin, reconstruction of the orbital margin to be performed before reattaching the lateral canthus to the implanted titanium mesh; anterior levator resection; and frontalis suspension according to preoperative levator muscle function. Visual acuity, tumor recurrence, and postoperative palpebral fissure and orbital appearance were evaluated to assess outcomes. Acceptable cosmetic results were obtained in 22 patients after debulking of the orbito-temporal NF and surgical reconstruction. There was no loss of vision or visual impairment postoperatively. All patients did not display recrudescence after a follow-up period of >1 year. Three patients with residual ptosis were successfully treated with a second ptosis repair. We believe that the blepharoplasty techniques described in the treatment of orbito-palpebral NF may provide both functional and esthetic benefits. Copyright © 2014 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

First Results of the Juno Magnetometer Investigation in Jupiter's Magnetosphere

NASA Astrophysics Data System (ADS)

Connerney, J. E. P.; Oliversen, R. J.; Espley, J. R.; Schnurr, R.; Sheppard, D.; Odom, J.; Lawton, P.; Murphy, S.; Joergensen, J. L.; Joergensen, P. S.; Merayo, J. M. G.; Denver, T.; Benn, M.; Bjarno, J. B.; Malinnikova Bang, A.; Bloxham, J.; Smith, E. J.; Bolton, S. J.

2016-12-01

The Juno spacecraft entered polar orbit about Jupiter on July 4, 2016, after a picture perfect Jupiter Orbit Insertion (JOI) main engine burn lasting 35 minutes. Juno's science instruments were not powered during the critical maneuver sequence ( 5 days) but were fully operational shortly afterward. The 53.5-day capture orbit provides Juno's science instruments with the first opportunity to sample the Jovian environment close up and in polar orbit on August 27, 2016 (PJ1). Following a successful PJ1, a period reduction maneuver (PRM) will drop the spacecraft into its 14-day science orbit to begin the science phase of the mission. During this phase, the gravity and magnetic fields will be mapped with unprecedented accuracy as Juno conducts a study of Jupiter's interior structure and composition, in addition to the first comprehensive exploration of the polar magnetosphere. The magnetic field investigation onboard Juno is equipped with two magnetometer sensor suites, located at 10 and 12 m from the spacecraft body at the end of one of the three solar panel wings. Each contains a vector fluxgate magnetometer (FGM) sensor and a pair of co-located non-magnetic star tracker camera heads which provide accurate attitude determination for the FGM sensors. This very capable magnetic observatory samples the Jovian magnetic field at a rate of up to 64 vector samples/second. We present the first observations of Jupiter's magnetic field obtained in polar orbit and in context with prior observations and those acquired by Juno's other science instruments (waves and particles instruments, and remote-sensing infrared and ultraviolet imaging spectrographs).

Aesthetic refinements in the treatment of graves ophthalmopathy.

PubMed

Doumit, Gaby; Abouhassan, William; Yaremchuk, Michael J

2014-09-01

Graves ophthalmopathy is a chronic, multisystem, autoimmune disorder characterized by increased volume of intraorbital fat and hypertrophic extraocular muscles. Proptosis, impaired ocular motility, diplopia, lid retraction, and impaired visual acuity are treated with orbit decompression and fat reduction. The authors present the addition of skeletal augmentation to further improve periorbital aesthetics. Through a transconjunctival with lateral canthotomy incision, a balanced orbital decompression was executed, removing medial and lateral walls and medial floor. Intraorbital fat was excised. All patients underwent placement of porous polyethylene infraorbital rim implants and midface soft-tissue elevation, increasing inferior orbital rim projection and improving the globe-cheek relationship. From 2009 to 2012, 13 patients (11 female and two male; 26 eyes) with Graves ophthalmopathy underwent surgery at two institutions. Outcomes were evaluated for improvements of proptosis, diplopia, dry eye symptoms, and cosmetic satisfaction. Postoperative follow-up ranged from 0.5 to 3 years (median, 1.5 years). The mean improvement on Hertel exophthalmometry was 5.4 mm. Diplopia resolved in three patients (23 percent). No patients had worsening diplopia, and 12 (92 percent) discontinued use of eye lubricants. All patients had cosmetic satisfaction. One patient suffered temporary inferior orbital nerve paresthesia. There were no infections, hematomas, or ocular complications. Skeletal augmentation is a useful adjunct to orbital decompression and fat excision for treating Graves ophthalmopathy. Balanced orbital decompression with infraorbital rim implants is reliable, effective, and safe, with good, lasting results. Resolution of ocular symptoms is improved, as are the patient's personal well-being and social life, with a high-benefit-to-low-risk. Therapeutic, IV.

Orbit Refinement of Asteroids and Comets Using a Robotic Telescope Network

NASA Astrophysics Data System (ADS)

Lantz Caughey, Austin; Brown, Johnny; Puckett, Andrew W.; Hoette, Vivian L.; Johnson, Michael; McCarty, Cameron B.; Whitmore, Kevin; UNC-Chapel Hill SKYNET Team

2016-01-01

We report on a multi-semester project to refine the orbits of asteroids and comets in our Solar System. One of the newest fields of research for undergraduate Astrophysics students at Columbus State University is that of asteroid astrometry. By measuring the positions of an asteroid in a set of images, we can reduce the overall uncertainty in the accepted orbital parameters of that object. These measurements, using our WestRock Observatory (WRO) and several other telescopes around the world, are being published through the Minor Planet Center (MPC) and benefit the global community.Three different methods are used to obtain these observations. First, we use our own 24-inch telescope at WRO, located in at CSU's Coca-Cola Space Science Center in downtown Columbus, Georgia . Second, we have access to data from the 20-inch telescope at Stone Edge Observatory in El Verano, California. Finally, we may request images remotely using Skynet, an online worldwide network of robotic telescopes. Our primary and long-time collaborator on Skynet has been the "41-inch" reflecting telescope at Yerkes Observatory in Williams Bay, Wisconsin. Thus far, we have used these various telescopes to refine the orbits of more than 15 asteroids and comets. We have also confirmed the resulting reduction in orbit-model uncertainties using Monte Carlo simulations and orbit visualizations, using Find_Orb and OrbitMaster software, respectively.Before any observatory site can be used for official orbit refinement projects, it must first become a trusted source of astrometry data for the MPC. We have therefore obtained Observatory Codes not only for our own WestRock Observatory (W22), but also for 3 Skynet telescopes that we may use in the future: Dark Sky Observatory in Boone, North Carolina (W38) Hume Observatory in Santa Rosa, California (U54) and Athabasca University Geophysical Observatory in Athabasca, Alberta, Canada (U96).

Tidal synchronization of an anelastic multi-layered body: Titan's synchronous rotation

NASA Astrophysics Data System (ADS)

Folonier, Hugo A.; Ferraz-Mello, Sylvio

2017-12-01

Tidal torque drives the rotational and orbital evolution of planet-satellite and star-exoplanet systems. This paper presents one analytical tidal theory for a viscoelastic multi-layered body with an arbitrary number of homogeneous layers. Starting with the static equilibrium figure, modified to include tide and differential rotation, and using the Newtonian creep approach, we find the dynamical equilibrium figure of the deformed body, which allows us to calculate the tidal potential and the forces acting on the tide generating body, as well as the rotation and orbital elements variations. In the particular case of the two-layer model, we study the tidal synchronization when the gravitational coupling and the friction in the interface between the layers is added. For high relaxation factors (low viscosity), the stationary solution of each layer is synchronous with the orbital mean motion ( n) when the orbit is circular, but the rotational frequencies increase if the orbital eccentricity increases. This behavior is characteristic in the classical Darwinian theories and in the homogeneous case of the creep tide theory. For low relaxation factors (high viscosity), as in planetary satellites, if friction remains low, each layer can be trapped in different spin-orbit resonances with frequencies n/2,n,3n/2,2n,\\ldots . When the friction increases, attractors with differential rotations are destroyed, surviving only commensurabilities in which core and shell have the same velocity of rotation. We apply the theory to Titan. The main results are: (i) the rotational constraint does not allow us to confirm or reject the existence of a subsurface ocean in Titan; and (ii) the crust-atmosphere exchange of angular momentum can be neglected. Using the rotation estimate based on Cassini's observation (Meriggiola et al. in Icarus 275:183-192, 2016), we limit the possible value of the shell relaxation factor, when a deep subsurface ocean is assumed, to γ _s≲ 10^{-9} s^{-1}, which corresponds to a shell's viscosity η _s≳ 10^{18} Pa s, depending on the ocean's thickness and viscosity values. In the case in which a subsurface ocean does not exist, the maximum shell relaxation factor is one order of magnitude smaller and the corresponding minimum shell's viscosity is one order higher.

Characteristic of the radiation field in low Earth orbit and in deep space.

PubMed

Reitz, Guenther

2008-01-01

The radiation exposure in space by cosmic radiation can be reduced through careful mission planning and constructive measures as example the provision of a radiation shelter, but it cannot be completely avoided. The reason for that are the extreme high energies of particles in this field and the herewith connected high penetration depth in matter. For missions outside the magnetosphere ionizing radiation is recognized as the key factor through its impact on crew health and performance. In absence of sporadic solar particle events the radiation exposure in Low Earth orbit (LEO) inside Spacecraft is determined by the galactic cosmic radiation (protons and heavier ions) and by the protons inside the South Atlantic Anomaly (SAA), an area where the radiation belt comes closer to the earth surface due to a displacement of the magnetic dipole axes from the Earth's center. In addition there is an albedo source of neutrons produced as interaction products of the primary galactic particles with the atoms of the earth atmosphere. Outside the spacecraft the dose is dominated by the electrons of the horns of the radiation belt located at about 60" latitude in Polar Regions. The radiation field has spatial and temporal variations in dependence of the Earth magnetic field and the solar cycle. The complexity of the radiation field inside a spacecraft is further increased through the interaction of the high energy components with the spacecraft shielding material and with the body of the astronauts. In interplanetary missions the radiation belt will be crossed in a couple of minutes and therefore its contribution to their radiation exposure is quite small, but subsequently the protection by the Earth magnetic field is lost, leaving only shielding measures as exposure reduction means. The report intends to describe the radiation field in space, the interaction of the particles with the magnetic field and shielding material and give some numbers on the radiation exposure in low earth orbits and in interplanetary missions.

Life Cycle Systems Engineering Approach to NASA's 2nd Generation Reusable Launch Vehicle

NASA Technical Reports Server (NTRS)

Thomas, Dale; Smith, Charles; Safie, Fayssal; Kittredge, Sheryl

2002-01-01

The overall goal of the 2nd Generation RLV Program is to substantially reduce technical and business risks associated with developing a new class of reusable launch vehicles. NASA's specific goals are to improve the safety of a 2nd- generation system by 2 orders of magnitude - equivalent to a crew risk of 1 -in- 10,000 missions - and decrease the cost tenfold, to approximately $1,000 per pound of payload launched. Architecture definition is being conducted in parallel with the maturating of key technologies specifically identified to improve safety and reliability, while reducing operational costs. An architecture broadly includes an Earth-to-orbit reusable launch vehicle, on-orbit transfer vehicles and upper stages, mission planning, ground and flight operations, and support infrastructure, both on the ground and in orbit. The systems engineering approach ensures that the technologies developed - such as lightweight structures, long-life rocket engines, reliable crew escape, and robust thermal protection systems - will synergistically integrate into the optimum vehicle. Given a candidate architecture that possesses credible physical processes and realistic technology assumptions, the next set of analyses address the system's functionality across the spread of operational scenarios characterized by the design reference missions. The safety/reliability and cost/economics associated with operating the system will also be modeled and analyzed to answer the questions "How safe is it?" and "How much will it cost to acquire and operate?" The systems engineering review process factors in comprehensive budget estimates, detailed project schedules, and business and performance plans, against the goals of safety, reliability, and cost, in addition to overall technical feasibility. This approach forms the basis for investment decisions in the 2nd Generation RLV Program's risk-reduction activities. Through this process, NASA will continually refine its specialized needs and identify where Defense and commercial requirements overlap those of civil missions.

Omitted variable bias in crash reduction factors.

DOT National Transportation Integrated Search

2015-09-01

Transportation planners and traffic engineers are increasingly turning to crash reduction factors to evaluate changes in road : geometric and design features in order to reduce crashes. Crash reduction factors are typically estimated based on segment...

Crash reduction factor (CRF) update.

DOT National Transportation Integrated Search

2011-01-01

Recent research conducted by the Federal Highway Administration (FHWA) produced the Desktop Reference for : Crash Reduction Factors, FHWA Report No. FHWA-SA-07-015, published in September 2007. These crash : reduction factors are commonly used by sta...

Changes of Space Debris Orbits After LDR Operation

NASA Astrophysics Data System (ADS)

Wnuk, E.; Golebiewska, J.; Jacquelard, C.; Haag, H.

2013-09-01

A lot of technical studies are currently developing concepts of active removal of space debris to protect space assets from on orbit collision. For small objects, such concepts include the use of ground-based lasers to remove or reduce the momentum of the objects thereby lowering their orbit in order to facilitate their decay by re-entry into the Earth's atmosphere. The concept of the Laser Debris Removal (LDR) system is the main subject of the CLEANSPACE project. One of the CLEANSPACE objectives is to define a global architecture (including surveillance, identification and tracking) for an innovative ground-based laser solution, which can remove hazardous medium debris around selected space assets. The CLEANSPACE project is realized by a European consortium in the frame of the European Commission Seventh Framework Programme (FP7), Space topic. The use of sequence of laser operations to remove space debris, needs very precise predictions of future space debris orbital positions, on a level even better than 1 meter. Orbit determination, tracking (radar, optical and laser) and orbit prediction have to be performed with accuracy much better than so far. For that, the applied prediction tools have to take into account all perturbation factors that influence object orbit. The expected object's trajectory after the LDR operation is a lowering of its perigee. To prevent the debris with this new trajectory to collide with another object, a precise trajectory prediction after the LDR sequence is therefore the main task allowing also to estimate re-entry parameters. The LDR laser pulses change the debris object velocity v. The future orbit and re-entry parameters of the space debris after the LDR engagement can be calculated if the resulting ?v vector is known with the sufficient accuracy. The value of the ?v may be estimated from the parameters of the LDR station and from the characteristics of the orbital debris. However, usually due to the poor knowledge of the debris object's size, mass, spin and chemical composition the value and the direction of the vector ?v cannot be estimated with the high accuracy. Therefore, a high precise tracking of the debris will be necessary immediately before the engagement of the LDR and also during this engagement. By extending this tracking and ranging for a few seconds after engagement, the necessary data to evaluate the orbital modification can be produced in the same way as it is done for the catalogue generation. In our paper we discuss the object's orbit changes due to LDR operation for different locations of LDR station and different parameters of the laser energy and telescope diameter. We estimate the future orbit and re-entry parameters taking into account the influence of all important perturbation factors on the space debris orbital motion after LDR.

Predictions of cardiovascular responses during STS reentry using mathematical models

NASA Technical Reports Server (NTRS)

Leonard, J. I.; Srinivasan, R.

1985-01-01

The physiological adaptation to weightless exposure includes cardiovascular deconditioning arising in part from a loss of total circulating blood volume and resulting in a reduction of orthostatic tolerance. The crew of the Shuttle orbiter are less tolerant to acceleration forces in the head-to-foot direction during the reentry phase of the flight at a time they must function at a high level of performance. The factors that contribute to orthostatic intolerance during and following reentry and to predict the likelihood of impaired crew performance are evaluated. A computer simulation approach employing a mathematical model of the cardiovascular system is employed. It is shown that depending on the severity of blood volume loss, the reentry acceleration stress may be detrimental to physiologic function and may place the physiologic status of the crew near the borderline of some type of impairment. They are in agreement with conclusions from early ground-based experiments and from observations of early Shuttle flights.

Space, our next frontier; Proceedings of the conference, Dallas, TX, June 7, 8, 1984

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musgrave, G.

1985-01-01

The present conference on space development encompasses space commercialization, legislative, legal, and insurance-related factors in current space programs, political aspects of space militarization and governmental control, the military future uses of space and their consequences, command and control issues arising in space, economic influences on space policy, and recent developments in space solar power generation concepts. Attention is given to public opinion surveys concerning the scientific, military, and economic uses of space, the Leasecraft orbital industrial infrastructure concept, capitalism and democracy in space development, the current status of space law on commercialization topics, the nature of Ballistic Missile Defense, themore » Soviet Space threat, the High Frontier concept for space defense, lunar solar power systems, solar power satellites, and the utilization of lunar resources for the reduction of lunar base construction costs. Such specific technical issues as microgravity crystal growth and directional solidification, electrophoresis operations for pharmaceuticals, and technical barriers to commercial access to space, are also noted.« less

[Population characteristics of mucous tissue basocytes in the Mongolian gerbil's jejunum following the 12-day orbital flight onboard space platform "Foton-M3"].

PubMed

Atyakshin, D A; Bykov, E G

2013-01-01

Optical (light) microscopy and histochemical techniques were used for the first-ever studies of the population characteristics of tissue basocytes in the jejunum mucous membrane in three groups of gerbils Meriones unguiculatus: flown over 12 days aboard space platform Foton-M3, subjected to spaceflight factors simulation (SFS) in dedicated system Kontur-L (2) and maintained in standard vivarium conditions (control). Space flight was shown to induce quantitative and qualitative changes in the population of jejunum mucus labrocytes. Reduction of the basocytes population, alterations in age composition and ratio of the morphofunctional cell types in microgravity were indicative of cytoplasmic aggregation intensity, paths of biosynthesis products release into the intersticium, and their tinctorial properties. Also, heparin maturation and liberalization into the extracellular space in support of the jejunum mucus adaptive functions progressed with greater intensity. SFS did not affect size of the basocytes population significantly although it did cause qualitative rearrangements in the population structure.

Evaluation of passive and active vibration control mechanisms in a microgravity environment

NASA Technical Reports Server (NTRS)

Ellison, J.; Ahmadi, G.; Grodsinsky, C.

1993-01-01

The behavior of equipment and their light secondary attachments in large space structures under orbital excitation is studied. The equipment is modeled as a shear beam and its secondary attachment is treated as a single-degree-of-freedom lumped mass system. Peak responses of the equipment and its secondary system for a variety of vibration control mechanisms are evaluated. A novel active friction control mechanism, by varying the normal force, is suggested. The device uses a magnetic field control to minimize the stick condition, thereby reducing the overall structural response. The results show that the use of the passive vibration control devices could reduce the peak equipment responses to a certain extent. However, major reduction of vibration levels could be achieved only by the use of active devices. Using active control of the interface normal force, the peak responses of the equipment and its attachment are reduced by a factor of 10 over the fixed-base equipment response.

The Southern Argentina Agile Meteor Radar Orbital System (SAAMER-OS): An Initial Sporadic Meteoroid Orbital Survey in the Southern Sky

NASA Technical Reports Server (NTRS)

Janches, D.; Close, S.; Hormaechea, J. L.; Swarnalingam, N.; Murphy, A.; O'Connor, D.; Vandepeer, B.; Fuller, B.; Fritts, D. C.; Brunini, C.

2015-01-01

We present an initial survey in the southern sky of the sporadic meteoroid orbital environment obtained with the Southern Argentina Agile MEteor Radar (SAAMER) Orbital System (OS), in which over three-quarters of a million orbits of dust particles were determined from 2012 January through 2015 April. SAAMER-OS is located at the southernmost tip of Argentina and is currently the only operational radar with orbit determination capability providing continuous observations of the southern hemisphere. Distributions of the observed meteoroid speed, radiant, and heliocentric orbital parameters are presented, as well as those corrected by the observational biases associated with the SAAMER-OS operating parameters. The results are compared with those reported by three previous surveys performed with the Harvard Radio Meteor Project, the Advanced Meteor Orbit Radar, and the Canadian Meteor Orbit Radar, and they are in agreement with these previous studies. Weighted distributions for meteoroids above the thresholds for meteor trail electron line density, meteoroid mass, and meteoroid kinetic energy are also considered. Finally, the minimum line density and kinetic energy weighting factors are found to be very suitable for meteoroid applications. The outcomes of this work show that, given SAAMERs location, the system is ideal for providing crucial data to continuously study the South Toroidal and South Apex sporadic meteoroid apparent sources.

THE SOUTHERN ARGENTINA AGILE METEOR RADAR ORBITAL SYSTEM (SAAMER-OS): AN INITIAL SPORADIC METEOROID ORBITAL SURVEY IN THE SOUTHERN SKY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Janches, D.; Swarnalingam, N.; Close, S.

2015-08-10

We present an initial survey in the southern sky of the sporadic meteoroid orbital environment obtained with the Southern Argentina Agile MEteor Radar (SAAMER) Orbital System (OS), in which over three-quarters of a million orbits of dust particles were determined from 2012 January through 2015 April. SAAMER-OS is located at the southernmost tip of Argentina and is currently the only operational radar with orbit determination capability providing continuous observations of the southern hemisphere. Distributions of the observed meteoroid speed, radiant, and heliocentric orbital parameters are presented, as well as those corrected by the observational biases associated with the SAAMER-OS operatingmore » parameters. The results are compared with those reported by three previous surveys performed with the Harvard Radio Meteor Project, the Advanced Meteor Orbit Radar, and the Canadian Meteor Orbit Radar, and they are in agreement with these previous studies. Weighted distributions for meteoroids above the thresholds for meteor trail electron line density, meteoroid mass, and meteoroid kinetic energy are also considered. Finally, the minimum line density and kinetic energy weighting factors are found to be very suitable for meteroid applications. The outcomes of this work show that, given SAAMER’s location, the system is ideal for providing crucial data to continuously study the South Toroidal and South Apex sporadic meteoroid apparent sources.« less

Evaluation of semiempirical atmospheric density models for orbit determination applications

NASA Technical Reports Server (NTRS)

Cox, C. M.; Feiertag, R. J.; Oza, D. H.; Doll, C. E.

1994-01-01

This paper presents the results of an investigation of the orbit determination performance of the Jacchia-Roberts (JR), mass spectrometer incoherent scatter 1986 (MSIS-86), and drag temperature model (DTM) atmospheric density models. Evaluation of the models was performed to assess the modeling of the total atmospheric density. This study was made generic by using six spacecraft and selecting time periods of study representative of all portions of the 11-year cycle. Performance of the models was measured for multiple spacecraft, representing a selection of orbit geometries from near-equatorial to polar inclinations and altitudes from 400 kilometers to 900 kilometers. The orbit geometries represent typical low earth-orbiting spacecraft supported by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). The best available modeling and orbit determination techniques using the Goddard Trajectory Determination System (GTDS) were employed to minimize the effects of modeling errors. The latest geopotential model available during the analysis, the Goddard earth model-T3 (GEM-T3), was employed to minimize geopotential model error effects on the drag estimation. Improved-accuracy techniques identified for TOPEX/Poseidon orbit determination analysis were used to improve the Tracking and Data Relay Satellite System (TDRSS)-based orbit determination used for most of the spacecraft chosen for this analysis. This paper shows that during periods of relatively quiet solar flux and geomagnetic activity near the solar minimum, the choice of atmospheric density model used for orbit determination is relatively inconsequential. During typical solar flux conditions near the solar maximum, the differences between the JR, DTM, and MSIS-86 models begin to become apparent. Time periods of extreme solar activity, those in which the daily and 81-day mean solar flux are high and change rapidly, result in significant differences between the models. During periods of high geomagnetic activity, the standard JR model was outperformed by DTM. Modification of the JR model to use a geomagnetic heating delay of 3 hours, as used in DTM, instead of the 6.7-hour delay produced results comparable to or better than the DTM performance, reducing definitive orbit solution ephermeris overlap differences by 30 to 50 percent. The reduction in the overlap differences would be useful for mitigating the impact of geomagnetic storms on orbit prediction.

Parametric trade studies on a Shuttle 2 launch system architecture

NASA Technical Reports Server (NTRS)

Stanley, Douglas O.; Talay, Theodore A.; Lepsch, Roger A.; Morris, W. Douglas; Naftel, J. Christopher; Cruz, Christopher I.

1991-01-01

A series of trade studies are presented on a complementary architecture of launch vehicles as a part of a study often referred to as Shuttle-2. The results of the trade studies performed on the vehicles of a reference Shuttle-2 mixed fleet architecture have provided an increased understanding of the relative importance of each of the major vehicle parameters. As a result of trades on the reference booster-orbiter configuration with a methane booster, the study showed that 60 percent of the total liftoff thrust should be on the booster and 40 percent on the orbiter. It was also found that the liftoff thrust to weight ratio (T/W) on the booster-orbiter should be 1.3. This leads to a low dry weight and still provides enough thrust to allow the design of a heavy lift architecture. As a result of another trade study, the dry weight of the reference booster-orbiter was chosen for a variety of operational considerations. Other trade studies on the booster-orbiter demonstrate that the cross feeding of propellant during boost phase is desirable and that engine-out capability from launch to orbit is worth the performance penalty. Technology assumptions made during the Shuttle-2 design were shown to be approx. equivalent to a 25 percent across the board weight reduction over the Space Shuttle technology. The vehicles of the Shuttle-2 architecture were also sized for a wide variety of payloads and missions to different orbits. Many of these same parametric trades were also performed on completely liquid hydrogen fueled fully reusable concepts. If a booster-orbiter is designed using liquid hydrogen engines on both the booster and orbiter, the total vehicle dry weight is only 3.0 percent higher than the reference dual-fuel booster-orbiter, and the gross weight is 3.8 percent less. For this booster-orbiter vehicle, a liftoff T/W of 1.3, a thrust of about 60 percent on the booster, and a Mach staging number of 3 all proved to be desirable. This modest dry weight increase for a liquid hydrogen fueled Shuttle-2 system should be more than offset by the elimination of the entire hydrocarbon engine development program and the savings in operation cost realized by the elimination of an entire fuel type.

Mapping the Solar System with LSST

NASA Astrophysics Data System (ADS)

Ivezic, Z.; Juric, M.; Lupton, R.; Connolly, A.; Kubica, J.; Moore, A.; Harris, A.; Bowell, T.; Bernstein, G.; Stubbs, C.; LSST Collaboration

2004-12-01

The currently considered LSST cadence, based on two 10 sec exposures, may result in orbital parameters, light curves and accurate colors for over a million main-belt asteroids (MBA), and about 20,000 trans-Neptunian objects (TNO). Compared to the current state-of-the-art, this sample would represent a factor of 5 increase in the number of MBAs with known orbits, a factor of 20 increase in the number of MBAs with known orbits and accurate color measurements, and a factor of 100 increase in the number of MBAs with measured variability properties. The corresponding sample increase for TNOs is 10, 100, and 1000, respectively. The LSST MBA and TNO samples will enable detailed studies of the dynamical and chemical history of the solar system. For example, they will constrain the MBA size distribution for objects larger than 100 m, and TNO size distribution for objects larger than 100 km, their physical state through variability measurements (solid body vs. a rubble pile), as well as their surface chemistry through color measurements. A proposed deep TNO survey, based on 1 hour exposures, may result in a sample of about 100,000 TNOs, while spending only 10% of the LSST observing time. Such a deep TNO survey would be capable of discovering Sedna-like objects at distances beyond 150 AU, thereby increasing the observable Solar System volume by about a factor of 7. The increase in data volume associated with LSST asteroid science will present many computational challenges to how we might extract tracks and orbits of asteroids from the underlying clutter. Tree-based algorithms for multihypothesis testing of asteroid tracks can help solve these challenges by providing the necessary 1000-fold speed-ups over current approaches while recovering 95% of the underlying asteroid populations.

Study of multi-kW solar arrays for Earth orbit application

NASA Technical Reports Server (NTRS)

1980-01-01

Low cost low Earth orbit (LOW) and geosynchronous Earth orbit (GEO) Solar Array concepts in the 300 to 1000 kW range which could be reduced to hardware in the mid 1980's, are identified. Size scaling factors and longer life demands are recognized as the prime drivers for the designs if low life cycle costs for energy are to be achieved. Technology is identified which requires further development in order to assure component readiness and availability. Use of the low concentration ratio (CR) concentrator, which uses gallium arsenide solar cells for both LEO and GEO applications, is recommended.

Study of the low energy spectrum of titanium by using QMC methods

NASA Astrophysics Data System (ADS)

Buendía, E.; Caballero, M. A.; Gálvez, F. J.

2018-02-01

We study the ground state and the low energy excited states of Ti. Each variational wave function is a product of a Jastrow correlation factor by a model function obtained within the parameterized optimized effective potential (POEP) framework by using a configuration mixing. Near degeneracy effects between the orbitals 4s and 4p, as well as excitations to the 3d orbital due to the strong competition between 4s and 3d orbitals in transition metal atoms are taken into account. All electron calculations have been carried out by using quantum Monte Carlo techniques, variational and diffusion.

Orbital magnetism: pros and cons for enhancing the cluster magnetism.

PubMed

Andriotis, Antonis N; Menon, Madhu

2004-07-09

The discrepancy seen in the experimental and theoretical results on the magnetic moment of a small magnetic cluster has been attributed to the contribution arising from orbital magnetism. In this Letter we show that the magnetic states with large orbital magnetic moment are not always energetically favorable; they could, however, be realizable by coating the cluster or deposing it on appropriate substrates. More importantly, our work shows that the crucial factors that determine the cluster magnetism are found to be the intrinsic, and consequently, the extrinsic properties of the constituent atoms of the cluster.

GNSS orbit determination by precise modeling of non-gravitational forces acting on satellite's body

NASA Astrophysics Data System (ADS)

Wielgosz, Agata; Kalarus, Maciej; Liwosz, Tomasz

2016-04-01

Satellites orbiting around Earth are affected by gravitational forces and non-gravitational perturbations (NGP). While the perturbations caused by gravitational forces, which are due to central body gravity (including high-precision geopotential field) and its changes (due to secular variations and tides), solar bodies attraction and relativistic effects are well-modeled, the perturbations caused by the non-gravitational forces are the most limiting factor in Precise Orbit Determination (POD). In this work we focused on very precise non-gravitational force modeling for medium Earth orbit satellites by applying the various models of solar radiation pressure including changes in solar irradiance and Earth/Moon shadow transition, Earth albedo and thermal radiation. For computing influence of aforementioned forces on spacecraft the analytical box-wing satellite model was applied. Smaller effects like antenna thrust or spacecraft thermal radiation were also included. In the process of orbit determination we compared the orbit with analytically computed NGP with the standard procedure in which CODE model is fitted for NGP recovery. We considered satellites from several systems and on different orbits and for different periods: when the satellite is all the time in full sunlight and when transits the umbra and penumbra regions.

Congenital anophthalmia: current concepts in management.

PubMed

Quaranta-Leoni, Francesco M

2011-09-01

The introduction of hydrogel socket and orbital expanders has modified the approach towards the rehabilitation of congenital anophthalmia. This study highlights the most recent advances for the treatment of congenital anophthalmia based on personal experience and the review of recent literature. Hydrogel socket expanders may be positioned as an out-patient procedure with topical anaesthesia, using cyanoacrylate glue as opposed to temporary tarsorraphy. Increased orbital volume has been confirmed by computed tomography (CT) scan or magnetic resonance imaging (MRI) following early dermis-fat graft in children with congenital anophthalmia. An orbital tissue expander made of an inflatable silicone globe sliding on a titanium T-plate and secured to the lateral orbital rim appears to be effective to stimulate orbital bone growth and development. Congenital anophthalmia has a complex cause with both genetic and environmental factors involved. The ideal treatment is simultaneous expansion of the eyelids, socket and orbital bones, and it should begin after birth as soon as possible. Socket expansion with self-inflating expanders is a useful technique, although custom-made conformers may produce similar results. Dermis-fat grafts are another reasonable option as an orbital implant, following adequate lid and socket expansion.

Thalidomide inhibits adipogenesis of orbital fibroblasts in Graves' ophthalmopathy.

PubMed

Zhang, Chu; Zhang, Xianfeng; Ma, Lizhen; Peng, Fengying; Huang, Jiao; Han, Hui

2012-04-01

The expansion of orbital adipose tissue is a main pathophysiology of Graves' ophthalmopathy (GO), which is an inflammatory autoimmune disease in the orbital region. The effects of immunosuppressive drugs on adipogenesis of orbital fibroblasts have not been determined. Thalidomide, as an immunosuppressive drug, has recently been used in the therapy of many autoimmune diseases. In this study, we analyzed the effects of thalidomide on adipogenesis and found that adipocyte differentiation from preadipocytes in the orbital region was enhanced, which was demonstrated by enhanced expression of peroxisome proliferator activated receptor γ (PPARγ), ap2, and thyroid-stimulating hormone receptor (TSHR). The expression of inflammatory cytokines tumor necrosis factor α (TNFα) and interleukin 6 (IL-6) was also increased in GO. Thalidomide dose-dependently inhibited adipogenesis of 3T3-L1 preadipocytes and orbital fibroblasts from GO patients. Along with the inhibited adipogenesis, the expression of TSHR, TNFα, and IL-6 was also down-regulated. We discovered that the mechanism for thalidomide inhibiting adipogenesis was the down-regulation of PPARγ, rather than C/EBPβ and C/EBPδ. We suggest that, besides its canonical anti-TNFα effect, thalidomide plays a role in inhibiting adipogenesis of orbital fibroblasts in GO patients.

Orbiter LH2 Feedline Flowliner Cracking Problem. Version 1.0

NASA Technical Reports Server (NTRS)

Harris, Charles E.; Cragg, Clinton H.; Raju, Ivatury S.; Elliot, Kenny B.; Madaras, Eric I.; Piascik, Robert S.; Halford, Gary R.; Bonacuse, Peter J.; Sutliff, Daniel L.; Bakhle, Milind A.

2005-01-01

In May of 2002, three cracks were found in the downstream flowliner at the gimbal joint in the LH2 feedline at the interface with the Low Pressure Fuel Turbopump (LPFP) of Space Shuttle Main Engine (SSME) #1 of Orbiter OV-104. Subsequent inspections of the feedline flowliners in the other orbiters revealed the existence of 8 additional cracks. No cracks were found in the LO2 feedline flowliners. A solution to the cracking problem was developed and implemented on all orbiters. The solution included weld repair of all detectable cracks and the polishing of all slot edges to remove manufacturing discrepancies that could initiate new cracks. Using the results of a fracture mechanics analysis with a scatter factor of 4 on the predicted fatigue life, the orbiters were cleared for return to flight with a one-flight rationale requiring inspections after each flight. OV-104 flew mission STS-112 and OV-105 flew mission STS-113. The post-flight inspections did not find any cracks in the repaired flowliners. At the request of the Orbiter Program, the NESC conducted an assessment of the Orbiter LH2 Feedline Flowliner cracking problem with a team of subject matter experts from throughout NASA.

Orbital Evolution of Jupiter-Family Comets

NASA Technical Reports Server (NTRS)

Ipatov, S. I.; Mather, J. S.; Oegerle, William R. (Technical Monitor)

2002-01-01

We investigated the evolution for periods of at least 5-10 Myr of 2500 Jupiter-crossing objects (JCOs) under the gravitational influence of all planets, except for Mercury and Pluto (without dissipative factors). In the first series we considered N=2000 orbits near the orbits of 30 real Jupiter-family comets with period less than 10 yr, and in the second series we took 500 orbits close to the orbit of Comet 10P Tempel 2. We calculated the probabilities of collisions of objects with the terrestrial planets, using orbital elements obtained with a step equal to 500 yr and then summarized the results for all time intervals and all bodies, obtaining the total probability P(sub sigma) of collisions with a planet and the total time interval T(sub sigma) during which perihelion distance of bodies was less than a semimajor axis of the planet. The values of P = 10(exp 6)P(sub sigma)/N and T = T(sub sigma)/1000 yr are presented in Table together with the ratio r of the total time interval when orbits were of Apollo type (at e less than 0.999) to that of Amor type.

Migration of Trans-Neptunian Objects to a Near-Earth Space

NASA Technical Reports Server (NTRS)

Ipatov, S. I.; Mather, J. C.; Oegerle, William (Technical Monitor)

2002-01-01

Our estimates of the migration of trans-Neptunian objects (TNOs) to a near-Earth space are based on the results of investigations of orbital evolution of TNOs and Jupiter-crossing objects (JCOs). The orbital evolution of TNOs was considered in many papers. Recently we investigated the evolution for intervals of at least 5-10 Myr of 2500 JCOs under the gravitational influence of all planets, except for Mercury and Pluto (without dissipative factors). In the first series we considered N=2000 orbits near the orbits of 30 real Jupiter-family comets with period P(sub alpha)less than 10 yr, and in the second series we took N=500 orbits close to the orbit of Comet 10P Tempel 2 (alpha=3.1 AU, e=0.53, i=12 deg). We calculated the probabilities of collisions of objects with the terrestrial planets, using orbital elements obtained with a step equal to 500 yr, and then summarized the results for all time intervals and all bodies, obtaining the total probability P(sub sigma) of collisions with a planet and the total time interval T(sub sigma) during which perihelion distance q of bodies was less than a semimajor axis of the planet.

Plasma diagnostics package. Volume 2: Spacelab 2 section, part A

NASA Technical Reports Server (NTRS)

Pickett, Jolene S. (Compiler); Frank, L. A. (Compiler); Kurth, W. S. (Compiler)

1988-01-01

This volume (2), which consists of two parts (A and B), of the Plasma Diagnostics Package (PDP) Final Science Report contains a summary of all of the data reduction and scientific analyses which were performed using PDP data obtained on STS-51F as a part of the Spacelab 2 (SL-2) payload. This work was performed during the period of launch, July 29, l985, through June 30, l988. During this period the primary data reduction effort consisted of processing summary plots of the data received by 12 of the 14 instruments located on the PDP and submitting these data to the National Space Science Data Center (NSSDC). The scientific analyses during the performance period consisted of follow-up studies of shuttle orbiter environment and orbiter/ionosphere interactions and various plasma particle and wave studies which dealt with data taken when the PDP was on the Remote Manipulator System (RMS) arm and when the PDP was in free flight. Of particular interest during the RMS operations and free flight were the orbiter wake studies and joint studies of beam/plasma interactions with the SL-2 Fast Pulse Electron Generator (FPEG) of the Vehicle Charging and Potential Investigation (VCAP). Internal reports, published papers and presentations which involve PDP/SL-2 data are listed in Sections 3 and 4. A PDP/SL-2 scientific results meeting was held at the University of Iowa on June 10, l986. This meeting was attended by most of the PDP and VCAP investigators and provided a forum for discussing and comparing the various results, particularly with regard to the PDP free flight.

Advances in Single and Multijunction III-V Photovoltaics on Silicon for Space Power

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fitzgerald, Eugene A.; Ringel, Steven A.

2005-01-01

A collaborative research effort at MIT, Ohio State University and NASA has resulted in the demonstration of record quality gallium arsenide (GaAs) based single junction photovoltaic devices on silicon (Si) substrates. The ability to integrate highly efficient, radiation hard III-V based devices on silicon offers the potential for dramatic reductions in cell mass (approx.2x) and increases in cell area. Both of these improvements offer the potential for dramatic reductions in the cost of on-orbit electrical power. Recently, lattice matched InGaP/GaAs and metamorphic InGaP/InGaAs dual junction solar cells were demonstrated by MBE and OMVPE, respectively. Single junction GaAs on Si devices have been integrated into a space flight experiment (MISSES), scheduled to be launched to the International Space Station in March of 2005. I-V performance data from the GaAs/Si will be collected on-orbit and telemetered to ground stations daily. Microcracks in the GaAs epitaxial material, generated because of differences in the thermal expansion coefficient between GaAs and Si, are of concern in the widely varying thermal environment encountered in low Earth orbit. Ground based thermal life cycling (-80 C to + 80 C) equivalent to 1 year in LEO has been conducted on GaAs/Si devices with no discernable degradation in device performance, suggesting that microcracks may not limit the ability to field GaAs/Si in harsh thermal environments. Recent advances in the development and testing of III-V photovoltaic devices on Si will be presented.

Assessment of the Contribution of BeiDou GEO, IGSO, and MEO Satellites to PPP in Asia-Pacific Region.

PubMed

Zhao, Qile; Wang, Chen; Guo, Jing; Liu, Xianglin

2015-12-01

In contrast to the US Global Positioning System (GPS), the Russian Global Navigation Satellite System (GLONASS) and the European Galileo, the developing Chinese BeiDou satellite navigation system (BDS) consists of not only Medium Earth Orbit (MEO), but also Geostationary Orbit (GEO) as well as Inclined Geosynchronous Orbit (IGSO) satellites. In this study, the Precise Point Positioning (PPP) and PPP with Integer Ambiguity Resolution (IAR) are obtained. The contributions of these three different types of BDS satellites to PPP in Asia-Pacific region are assessed using data from selected 20 sites over more than four weeks. By using various PPP cases with different satellite combinations, in general, the largest contribution of BDS IGSO among the three kinds of BDS satellites to the reduction of convergence time and the improvement of positioning accuracy, particularly in the east direction, is identified. These PPP cases include static BDS only solutions and static/kinematic ambiguity-float and -fixed PPP with the combination of GPS and BDS. The statistical results demonstrate that the inclusion of BDS GEO and MEO satellites can improve the observation condition and result in better PPP performance as well. When combined with GPS, the contribution of BDS to the reduction of convergence time is, however, not as significant as that of GLONASS. As far as the positioning accuracy is concerned, GLONASS improves the accuracy in vertical component more than BDS does, whereas similar improvement in horizontal component can be achieved by inclusion of BDS IGSO and MEO as GLONASS.

Assessment of the Contribution of BeiDou GEO, IGSO, and MEO Satellites to PPP in Asia–Pacific Region

PubMed Central

Zhao, Qile; Wang, Chen; Guo, Jing; Liu, Xianglin

2015-01-01

In contrast to the US Global Positioning System (GPS), the Russian Global Navigation Satellite System (GLONASS) and the European Galileo, the developing Chinese BeiDou satellite navigation system (BDS) consists of not only Medium Earth Orbit (MEO), but also Geostationary Orbit (GEO) as well as Inclined Geosynchronous Orbit (IGSO) satellites. In this study, the Precise Point Positioning (PPP) and PPP with Integer Ambiguity Resolution (IAR) are obtained. The contributions of these three different types of BDS satellites to PPP in Asia–Pacific region are assessed using data from selected 20 sites over more than four weeks. By using various PPP cases with different satellite combinations, in general, the largest contribution of BDS IGSO among the three kinds of BDS satellites to the reduction of convergence time and the improvement of positioning accuracy, particularly in the east direction, is identified. These PPP cases include static BDS only solutions and static/kinematic ambiguity-float and -fixed PPP with the combination of GPS and BDS. The statistical results demonstrate that the inclusion of BDS GEO and MEO satellites can improve the observation condition and result in better PPP performance as well. When combined with GPS, the contribution of BDS to the reduction of convergence time is, however, not as significant as that of GLONASS. As far as the positioning accuracy is concerned, GLONASS improves the accuracy in vertical component more than BDS does, whereas similar improvement in horizontal component can be achieved by inclusion of BDS IGSO and MEO as GLONASS. PMID:26633406

ARPES Study on the Strongly Correlated Iron Chalcogenides Fe1+ySexTe1-x

NASA Astrophysics Data System (ADS)

Liu, Zhongkai

2014-03-01

The level of electronic correlation has been one of the key questions in understanding the nature of iron-based superconductivity. Using Angle Resolved Photoemission Spectroscopy (ARPES), we systematically investigated the correlation level in the iron chalcogenide family Fe1+ySexTe1-x. For the parent compound Fe1.02Te, we discovered ``peak-dip-hump'' spectra with heavily renormalized quasiparticles in the low temperature antiferromagnetic (AFM) state, characteristic of coherent polarons seen in other correlated materials with complex electronic and lattice interactions. As the temperature (or Se ratio x) increases and Fe1.02SexTe1-x is in the paramagnetic (PM) phase, we observed dissociation behavior of polarons, suggestive of connection between the weakening electron-phonon coupling and AFM. Further increase of x leads to an incoherent to coherent crossover in the electronic structure, indicating a reduction in the electronic correlation as the superconductivity emerges. Furthermore, the reduction of the electronic correlation in Fe1+ySexTe1-x evolves in an orbital-dependent way, where the dxy orbital is influenced most significantly. At the other end of the phase diagram (FeSe) where the single crystal is not stable, we have studied the MBE-grown thin film which also reveals orbital-dependent strong correlation in the electronic structure. Our findings provide a quantitative comprehension on the correlation level and its evolution on the phase diagram of Fe1+ySexTe1-x. We discuss the physical scenarios leading to strong correlations and its connection to superconductivity.

Development of a residual acceleration data reduction and dissemination plan

NASA Technical Reports Server (NTRS)

Rogers, Melissa J. B.

1992-01-01

A major obstacle in evaluating the residual acceleration environment in an orbiting space laboratory is the amount of data collected during a given mission: gigabytes of data will be available as SAMS units begin to fly regularly. Investigators taking advantage of the reduced gravity conditions of space should not be overwhelmed by the accelerometer data which describe these conditions. We are therefore developing a data reduction and analysis plan that will allow principal investigators of low-g experiments to create experiment-specific residual acceleration data bases for post-flight analysis. The basic aspects of the plan can also be used to characterize the acceleration environment of earth orbiting laboratories. Our development of the reduction plan is based on the following program of research: the identification of experiment sensitivities by order of magnitude estimates and numerical modelling; evaluation of various signal processing techniques appropriate for the reduction, supplementation, and dissemination of residual acceleration data; and testing and implementation of the plan on existing acceleration data bases. The orientation of the residual acceleration vector with respect to some set of coordinate axes is important for experiments with known directional sensitivity. Orientation information can be obtained from the evaluation of direction cosines. Fourier analysis is commonly used to transform time history data into the frequency domain. Common spectral representations are the amplitude spectrum which gives the average of the components of the time series at each frequency and the power spectral density which indicates the power or energy present in the series per unit frequency interval. The data reduction and analysis scheme developed involves a two tiered structure to: (1) identify experiment characteristics and mission events that can be used to limit the amount of accelerator data an investigator should be interested in; and (2) process the data in a way that will be meaningful to the experiment objectives. A general outline of the plan is given.

Comparative analysis of on-orbit dynamic performance of several large antenna concepts

NASA Technical Reports Server (NTRS)

Andersen, G. C.; Garrett, L. B.; Calleson, R. E.

1985-01-01

A comparative analysis of the on-orbit dynamic performance of four large anetanna concepts is presented. Among the antenna concepts evaluated are: the box truss; tetrahedral truss; warp-radial rib; and the hoop and column antenna designs. The characteristics and magnitudes of the antennas' dynamic response were evaluated in terms of structural displacements and member loads incurred during various slew-rate maneuvers. The results of the dynamic response analysis are compared to the design requirements of the Land Mobile Satellite System (LMSS) with respect to surface accuracy, decenter, defocus, and angular rocking. Comments are made on the effectiveness of structural damping and the application of active controls for vibrational response reduction. Schematic illustrations of the antenna design concepts are provided.

A Shuttle Upper Atmosphere Mass Spectrometer /SUMS/ experiment

NASA Technical Reports Server (NTRS)

Blanchard, R. C.; Duckett, R. J.; Hinson, E. W.

1982-01-01

A magnetic mass spectrometer is currently being adapted to the Space Shuttle Orbiter to provide repeated high altitude atmosphere data to support in situ rarefied flow aerodynamics research, i.e., in the high velocity, low density flight regime. The experiment, called Shuttle Upper Atmosphere Mass Spectrometer (SUMS), is the first attempt to design mass spectrometer equipment for flight vehicle aerodynamic data extraction. The SUMS experiment will provide total freestream atmospheric quantitites, principally total mass density, above altitudes at which conventional pressure measurements are valid. Experiment concepts, the expected flight profile, tradeoffs in the design of the total system and flight data reduction plans are discussed. Development plans are based upon a SUMS first flight after the Orbiter initial development flights.

Supersonic stability and control characteristics of a 0.015 scale model 69-0 of the space shuttle orbiter with forebody RSI modifications in the NASA/LaRC 4-foot UPWT (legs 1 and 2) (LA71A/B)

NASA Technical Reports Server (NTRS)

1977-01-01

Investigations are reported for the determination of aerodynamic effects of reducing the thickness of the reusable surface insulation located along the sides of the shuttle orbiter in order to allow weight reduction in the nose region. Six-component aerodynamic force and moment data were obtained at Mach numbers from 1.5 to 4.6 over an angle of attack range from about -1 deg to 28 deg. Additional tests were made over an angle of sideslip range from -6 deg to 6 deg at selected angles of attack. Test results are presented in graph and tables.

Atmospheric rendezvous feasibility study

NASA Technical Reports Server (NTRS)

Schaezler, A. D.

1972-01-01

A study was carried out to determine the feasibility of using atmospheric rendezvous to increase the efficiency of space transportation and to determine the most effective implementation. It is concluded that atmospheric rendezvous is feasible and can be utilized in a space transportation system to reduce size of the orbiter vehicle, provide a powered landing with go-around capability for every mission, and achieve lateral range performance that exceeds requirements. A significantly lighter booster and reduced launch fuel requirements are additional benefits that can be realized with a system that includes a large subsonic airplane for recovery of the orbiter. Additional reduction in booster size is possible if the airplane is designed for recovery of the booster by towing. An airplane about the size of the C-5A is required.

Three Decades of Precision Orbit Determination Progress, Achievements, Future Challenges and its Vital Contribution to Oceanography and Climate Research

NASA Technical Reports Server (NTRS)

Luthcke, Scott; Rowlands, David; Lemoine, Frank; Zelensky, Nikita; Beckley, Brian; Klosko, Steve; Chinn, Doug

2006-01-01

Although satellite altimetry has been around for thirty years, the last fifteen beginning with the launch of TOPEX/Poseidon (TP) have yielded an abundance of significant results including: monitoring of ENS0 events, detection of internal tides, determination of accurate global tides, unambiguous delineation of Rossby waves and their propagation characteristics, accurate determination of geostrophic currents, and a multi-decadal time series of mean sea level trend and dynamic ocean topography variability. While the high level of accuracy being achieved is a result of both instrument maturity and the quality of models and correction algorithms applied to the data, improving the quality of the Climate Data Records produced from altimetry is highly dependent on concurrent progress being made in fields such as orbit determination. The precision orbits form the reference frame from which the radar altimeter observations are made. Therefore, the accuracy of the altimetric mapping is limited to a great extent by the accuracy to which a satellite orbit can be computed. The TP mission represents the first time that the radial component of an altimeter orbit was routinely computed with an accuracy of 2-cm. Recently it has been demonstrated that it is possible to compute the radial component of Jason orbits with an accuracy of better than 1-cm. Additionally, still further improvements in TP orbits are being achieved with new techniques and algorithms largely developed from combined Jason and TP data analysis. While these recent POD achievements are impressive, the new accuracies are now revealing subtle systematic orbit error that manifest as both intra and inter annual ocean topography errors. Additionally the construction of inter-decadal time series of climate data records requires the removal of systematic differences across multiple missions. Current and future efforts must focus on the understanding and reduction of these errors in order to generate a complete and consistent time series of improved orbits across multiple missions and decades required for the most stringent climate-related research. This presentation discusses the POD progress and achievements made over nearly three decades, and presents the future challenges, goals and their impact on altimetric derived ocean sciences.

Drag De-Orbit Device: A New Standard Re-Entry Actuator for CubeSats

NASA Technical Reports Server (NTRS)

Guglielmo, David; Omar, Sanny; Bevilacqua, Riccardo

2017-01-01

With the advent of CubeSats, research in Low Earth Orbit (LEO) becomes possible for universities and small research groups. Only a handful of launch sites can be used, due to geographical and political restrictions. As a result, common orbits in LEO are becoming crowded due to the additional launches made possible by low-cost access to space. CubeSat design principles require a maximum of a 25-year orbital lifetime in an effort to reduce the total number of spacecraft in orbit at any time. Additionally, since debris may survive re-entry, it is ideal to de-orbit spacecraft over unpopulated areas to prevent casualties. The Drag Deorbit Device (D3) is a self-contained targeted re-entry subsystem intended for CubeSats. By varying the cross-wind area, the atmospheric drag can be varied in such a way as to produce desired maneuvers. The D3 is intended to be used to remove spacecraft from orbit to reach a desired target interface point. Additionally, attitude stabilization is performed by the D3 prior to deployment and can replace a traditional ADACS on many missions.This paper presents the hardware used in the D3 and operation details. Four stepper-driven, repeatedly retractable booms are used to modify the cross-wind area of the D3 and attached spacecraft. Five magnetorquers (solenoids) over three axes are used to damp rotational velocity. This system is expected to be used to improve mission flexibility and allow additional launches by reducing the orbital lifetime of spacecraft.The D3 can be used to effect a re-entry to any target interface point, with the orbital inclination limiting the maximum latitude. In the chance that the main spacecraft fails, a timer will automatically deploy the booms fully, ensuring the spacecraft will at the minimum reenter the atmosphere in the minimum possible time, although not necessarily at the desired target interface point. Although this does not reduce the risk of casualties, the 25-year lifetime limit is still respected, allowing a reduction of the risk associated with a hardware failure.

Electric Propulsion System for Constellation Deployment and Orbit Control of Minisats

NASA Astrophysics Data System (ADS)

Bianco, P.; de Rocco, L.; Lovera, M.

1999-09-01

The late technology developments and the demand for low-cost space missions have raised the interest in small satellites and in their potential use as parts of satellite formations as well as building units of satellite constellations. Formation flying of small satellites can be used to bring in-orbit spares for failed payloads on larger satellites as well as to replace large satellites at all by flying the mission on more small satellites, each carrying a single payload. Small satellites can be used in constellations for scientific missions (e.g. remote sensing) as well as for commercial purposes (e.g. data relay). Yet, "small satellite" doesn't necessarily mean "cheap satellite": cost reduction must be enforced into the space mission design since the very beginning of it, at system level. This usually implies seeking for trade-offs on most expensive system items for a small sat. Among these, we surely have the launch and the onboard propulsion system for orbital manoeuvres and station keeping: the stricter the requirements, the higher the costs. And, when dealing with satellite constellations or formations, orbital requirements can be quite challenging. The system designer is faced with the dilemma on whether to buy a relatively expensive dedicated launch or to have a highly cost-impactive autonomous onboard propulsion system that should perform orbit transfers as well. The present paper, which is an up-to-date version of the one presented at IAF-99, introduces a system based on FEEP (Field Emission Electric Propulsion) technology, featuring low thrust plug-on propulsion units. Thanks to the self-contained concept of FEEP thrusters and to the plug-on feature of the whole system, a very low cost-impactive onboard propulsion system can be implemented in order to serve for both orbital manoeuvres (constellation / formation deployment, orbit rising) and orbit maintenance (drag compensation, station keeping relative to other satellites). Most convenient strategies to operate such propulsion systems with respect to orbital requirements, principal design drivers and sizing methods are presented and discussed as well as practical up-to-date case study results performed at Carlo Gavazzi Space.

UV emissions of Jupiter: exploration of the high-latitude regions through the UV spectrograph on NASA's Juno mission

NASA Astrophysics Data System (ADS)

Hue, Vincent; Gladstone, Randy; Versteeg, Maarten; Greathouse, Thomas K.; Davis, Michael; Gerard, Jean-Claude; Grodent, Denis; Bonfond, Bertrand

2016-10-01

The Juno mission offers the opportunity to study Jupiter, from its inner structure to its magnetospheric environment. Juno was launched on August 2011 and its Jupiter orbit insertion (JOI) planned for July 4th 2016, will place Juno in a 53.5 days capture orbit. A period reduction maneuver will be performed two orbits later to place Juno into 14-days elliptical orbits for the duration of the nominal mission, which includes 36 orbits. Juno-UVS is a UV spectrograph with a bandpass of 70 ≤ λ ≤ 205 nm, designed to characterize Jupiter UV emissions. One of the main additions of UVS compared to its predecessors is a 2.54 mm tantalum shielding, to protect it from the harsh radiation environment at Jupiter, and a scan mirror, to allow for targeting specific auroral regions during perijove passes. The scan mirror is located at the front end of the instrument and will be used to look at +/- 30° perpendicular to the Juno spin plane. The entrance slit of UVS has a dog-bone shape composed by three sections with field of views of 0.2°x2.5°, 0.025°x2.0° and 0.2°x2.5°, as projected onto the sky. It will provide new constraints on Jupiter's auroral nightside morphology and spectral features as well as the vertical structure of these emissions. It will bring remote-sensing constraints for the onboard waves and particle instruments (JADE, JEDI, Waves and MAG). The ability to change the pointing will allow relating the observed UV brightness of the regions magnetically connected to where Juno flies with the particles and waves measurements. We will discuss the planned observations and scientific targets for the nominal mission orbital sequence, which will consist of three UV datasets per orbit. We will present the results from the first orbit. As Juno orbit evolves during the mission, we will also present how these objectives evolve over time.

Enhanced orbital magnetic moment in FeCo nanogranules observed by Barnett effect

NASA Astrophysics Data System (ADS)

Ogata, Y.; Chudo, H.; Gu, B.; Kobayashi, N.; Ono, M.; Harii, K.; Matsuo, M.; Saitoh, E.; Maekawa, S.

2017-11-01

The gyroscopic g factor, g‧ , of FeCo nanogranules embedded in a matrix of MgF2 (FeCo-MgF2) was determined by measuring the magnetic-field generation from a rotating sample due to the Barnett effect. The g‧ value of the FeCo-MgF2 is estimated to be 1.76 ± 0.11. The orbital contribution to the magnetic moment in the FeCo nanogranules was found to be quite large compared with that in bulk FeCo, being consistent with a density-functional-theory calculation that shows that the orbital magnetic moment may increase at the FeCo/MgF2 interfaces. The result suggests that the orbital magnetic moment is enhanced by symmetry breaking at the surface of the FeCo nanogranules.

Estimation of Orbital Neutron Detector Spatial Resolution by Systematic Shifting of Differential Topographic Masks

NASA Technical Reports Server (NTRS)

McClanahan, T. P.; Mitrofanov, I. G.; Boynton, W. V.; Chin, G.; Livengood, T.; Starr, R. D.; Evans, L. G.; Mazarico, E.; Smith, D. E.

2012-01-01

We present a method and preliminary results related to determining the spatial resolution of orbital neutron detectors using epithermal maps and differential topographic masks. Our technique is similar to coded aperture imaging methods for optimizing photonic signals in telescopes [I]. In that approach photon masks with known spatial patterns in a telescope aperature are used to systematically restrict incoming photons which minimizes interference and enhances photon signal to noise. Three orbital neutron detector systems with different stated spatial resolutions are evaluated. The differing spatial resolutions arise due different orbital altitudes and the use of neutron collimation techniques. 1) The uncollimated Lunar Prospector Neutron Spectrometer (LPNS) system has spatial resolution of 45km FWHM from approx. 30km altitude mission phase [2]. The Lunar Rennaissance Orbiter (LRO) Lunar Exploration Neutron Detector (LEND) with two detectors at 50km altitude evaluated here: 2) the collimated 10km FWHM spatial resolution detector CSETN and 3) LEND's collimated Sensor for Epithermal Neutrons (SETN). Thus providing two orbital altitudes to study factors of: uncollimated vs collimated and two average altitudes for their effect on fields-of-view.

The eivaN: A forward-looking interactive orbital trajectory plotting tool for use with proximity operations (PROX OPS) and other maneuvers: Description and user's manual

NASA Technical Reports Server (NTRS)

Brody, Adam R.

1988-01-01

The results of vehicle burns on-orbit are very difficult to anticipate because of nonlinearities in the equations of motion governing orbiting bodies. This confusion was noticed firsthand in prior experimentation. Out of plane motion is relatively simple as it is uncoupled from the other two degrees of freedom. However, in plane thrusts are more complex because the motions resulting from these inputs are coupled. An interactive planning device, eivaN, was developed to plot resulting trajectories, to provide a better comprehension of orbital mechanics effects, and to help the user to develop heuristics for on-orbit mission planning. The eivaN runs with Microsoft Excel on a Macintosh computer. It provides a forward looking display: burn parameters in the three orthogonal axes in addition to time inputted, and the resultant trajectory is then plotted. Position and velocity components for any burn at any user specified time are readily available. A new area of research related to the human factors of real time, on-orbit mission planning was identified and is currently being investigated.

Characterization of MODIS and SeaWiFS Solar Diffuser On-Orbit Degradation

NASA Technical Reports Server (NTRS)

Xiong, X.; Eplee, R. E., Jr.; Sun, J.; Patt, F. S.; Angal, A.; McClain, C. R.

2009-01-01

MODIS has 20 reflective solar bands (RSB), covering the VIS, NIR, and SWIR spectral regions. They are calibrated on-orbit using a solar diffuser (SD) panel, made of space-grade Spectralon. The SD bi-directional reflectance factor (BRF) was characterized pre-launch by the instrument vendor reference to the NIST reflectance standard. Its on-orbit degradation is tracked by an on-board solar diffuser stability monitor (SDSM). The SeaWifS on-orbit calibration strategy uses monthly lunar observations to monitor the long-term radiometric stability of the instrument and applies daily observations of its solar diffuser (an aluminum plate coated with YB71 paint) to track the short-term changes in the instrument response. This paper provides an overview of MODIS and SeaWiFS SD observations, applications, and approaches used to track their on-orbit degradations. Results from sensors are presented with emphasis on the spectral dependence and temporal trends of the SD degradation. Lessons and challenges from the use of SD for sensor on-orbit calibration are also discussed.

Comparisons of LET distributions measured in low-earth orbit using tissue-equivalent proportional counters and the position-sensitive silicon-detector telescope (RRMD-III)

NASA Technical Reports Server (NTRS)

Doke, T.; Hayashi, T.; Borak, T. B.; Chatterjee, A. (Principal Investigator)

2001-01-01

Determinations of the LET distribution, phi(L), of charged particles within a spacecraft in low-Earth orbit have been made. One method used a cylindrical tissue-equivalent proportional counter (TEPC), with the assumption that for each measured event, lineal energy, y, is equal to LET and thus phi(L) = phi(y). The other was based on the direct measurement of LETs for individual particles using a charged-particle telescope consisting of position-sensitive silicon detectors called RRMD-III. There were differences of up to a factor of 10 between estimates of phi(L) using the two methods on the same mission. This caused estimates of quality factor to vary by a factor of two between the two methods.

Correlation between ionic radii of metals and thermal decomposition of supramolecular structure of azodye complexes

NASA Astrophysics Data System (ADS)

El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Eldesoky, A. M.; Morgan, Sh. M.

2015-01-01

An interesting azodye heterocyclic ligand of copper(II), cobalt(II), nickel(II) and uranyl(II) complexes have been synthesized by the reaction of metal salts with 5-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-2-thioxo-4-thiazolidinone (HL) yields 1:1 and 1:2 (M:L) complexes depending on the reaction conditions. The elemental analysis, magnetic moments, spectral (UV-Vis, IR, 1H and 13C NMR and ESR) and thermal studies were used to characterize the isolated complexes. The molecular structures of the ligand tautomers are optimized theoretically and the quantum chemical parameters are calculated. The IR spectra showed that the ligand (HL) act as monobasic tridentate/neutral bidentate through the (sbnd Ndbnd N), enolic (Csbnd O)- and/or oxygen keto moiety groups forming a five/six-membered structures. According to intramolecular hydrogen bond leads to increasing of the complexes stability. The molar conductivities show that all the complexes are non-electrolytes. The ESR spectra indicate that the free electron is in dxy orbital. The calculated bonding parameter indicates that in-plane σ-bonding is more covalent than in-plane π-bonding. The coordination geometry is five/six-coordinated trigonal bipyramidal for complex (1) and octahedral for complexes (2-6). The value of covalency factor β12 and orbital reduction factor K accounts for the covalent nature of the complexes. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. The synthesized ligand (HL) and its Cu(II) complexes (1, 2 and 4) are screened for their biological activity against bacterial and fungal species. The ligand (HL) showed antimicrobial activities against Escherichia coli. The ligand (HL) and its Cu(II) complexes (2 and 4) have very high antifungal activity against Penicillium italicum. The inhibitive action of ligand (HL), against the corrosion of C-steel in 2 M HCl solution has been investigated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).

[SUBSTANTIATION OF DOSE LIMITS FOR A NEW NORMATIVE DOCUMENT ON RADIATION SAFETY OF LONG-DURATION SPACE MISSIONS AT ORBIT ALTITUDES OF UP TO 500 KM].

PubMed

Ushakov, I B; Grigoriev, Yu G; Shafirkin, A V; Shurshakov, V A

2016-01-01

Review of the data of experimental radiobiology and epidemiological follow-up of large groups of people subjected to radiation exposures on Earth has been undertaken to substantiate dose limits for critical organs of cosmonauts in order to ensure good performance and vitality while on long-duration orbital missions. The career dose limits for cosmonauts and astronauts established earlier in the USSR and USA amounted to nothing more but banning the risk of cancer death increase to 3%. To apply more rigorous criteria of delayed radiation risks, the Russian limits for cosmonauts were revised to substantiate a 4-fold reduction of the average tissue equivalent dose maximum to 1 Sv. The total of cancer and non-cancer radiation risks over lifetime and probable reduction of mean life expectancy (MLE) were calculated using the model of radiation-induced mortality for mammals and taken as the main damage to health. The established dose limit is equal to the career dose for nuclear industry personnel set forth by Russian standard document NRB 99/2009. For better agreement of admissible threshold doses to critical human organs (bone marrow, lens and skin) in the revised radiation limits for long-duration space missions and radiation safety limits on Earth, reduction of dose limits for the critical organs were substantiated additionally; these limits comply with those for planned over-exposure on Earth in document NRB 99/2009.

Orbital design strategy for domestic communication satellite systems.

NASA Technical Reports Server (NTRS)

Ramji, S.; Sawitz, P.

1973-01-01

Review of some of the considerations pertinent to efficient orbit utilization in the design of domestic communications satellite systems. A strategy is developed to efficiently locate a heterogeneous system of satellites within the available arc and provide room for future growth. A practical design is illustrated, using a computer simulation model, for the placement of 25 satellites within 73% of the available arc employing frequency and polarization coordination techniques. A number of widely variable factors that influence satellite spacing are examined. These factors include such critical system elements as telephony and television interference noise limits, frequency plan coordination, polarization plan coordination, ground antenna diameter, signal protection ratio, and satellite station keeping.

Periodic Orbits and Semiclassical Form Factor in Barrier Billiards

NASA Astrophysics Data System (ADS)

Giraud, O.

2005-11-01

Using heuristic arguments based on the trace formulas, we analytically calculate the semiclassical two-point correlation form factor for a family of rectangular billiards with a barrier of height irrational with respect to the side of the billiard and located at any rational position p/q from the side. To do this, we first obtain the asymptotic density of lengths for each family of periodic orbits by a Siegel-Veech formula. The result obtained for these pseudo-integrable, non-Veech billiards is different but not far from the value of 1/2 expected for semi-Poisson statistics and from values of obtained previously in the case of Veech billiards.

Collisions near Kerr black holes: lower limit of energy between orbiting and incoming particles

NASA Astrophysics Data System (ADS)

Rutkowski, Mieszko

2017-01-01

In our paper we investigate the lower limit of collisional energy of test particles near the Kerr black hole. In particular we examine the minimal Lorentz factor between the freely falling particles and the particles orbiting around a black hole. We consider collisions on the innermost stable circular orbit and examine near-extreme case, where collisions take place near an event horizon. By fine-tuning the particles' angular momentum, the Lorentz factor of the collision can always be minimized to a value dependent on the black hole's spin. We identified that this minimal value is always less than 2√{2}-1/√{3} and more than √{12}-1/√{6} (the limits are the values for an extreme Kerr and Schwarzschild, respectively). It implies that this kind of collisions of compact objects are expected to be highly energetic near supermassive black holes. In addition, we show that an interaction between black hole's and particle's spins has an influence on minimal Lorentz factor. This contribution is nonnegligible for near-extreme black holes. We also discuss the relation between our results and sci-fi movie Interstellar.

Preliminary design and cost of a 1-megawatt solar-pumped iodide laser space-to-space transmission station

NASA Technical Reports Server (NTRS)

Deyoung, R. J.; Walker, G. H.; Williams, M. D.; Schuster, G. L.; Conway, E. J.

1987-01-01

A preliminary conceptual design of a space-based solar pumped iodide laser emitting 1 megawatt of laser power for space-to-space power transmission is described. A near parabolic solar collector focuses sunlight onto the t-C4F9I (perfluoro-t butyl iodide) lasant within a transverse flow optical cavity. Using waste heat, a thermal system was designed to supply compressor and auxiliary power. System components were designed with weight and cost estimates assigned. Although cost is very approximate, the cost comparison of individual system components leads to valuable insights for future research. In particular, it was found that laser efficiency was not a dominant cost or weight factor, the dominant factor being the laser cavity and laser transmission optics. The manufacturing cost was approx. two thirds of the total cost with transportation to orbit the remainder. The flowing nonrenewable lasant comprised 20% of the total life cycle cost of the system and thus was not a major cost factor. The station mass was 92,000 kg without lasant, requiring approx. four shuttle flights to low Earth orbit where an orbital transfer vehicle will transport it to the final altitude of 6378 km.

Measurements of the linear energy transfer spectra on the Mir orbital station and comparison with radiation transport models

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Konradi, A.; Atwell, W.; Golightly, M. J.; Cucinotta, F. A.; Wilson, J. W.; Petrov, V. M.; Tchernykh, I. V.; Shurshakov, V. A.; Lobakov, A. P.

1996-01-01

A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.