Sequential ranging integration times in the presence of CW interference in the ranging channel

NASA Technical Reports Server (NTRS)

Mathur, Ashok; Nguyen, Tien

1986-01-01

The Deep Space Network (DSN), managed by the Jet Propulsion Laboratory for NASA, is used primarily for communication with interplanetary spacecraft. The high sensitivity required to achieve planetary communications makes the DSN very susceptible to radio-frequency interference (RFI). In this paper, an analytical model is presented of the performance degradation of the DSN sequential ranging subsystem in the presence of downlink CW interference in the ranging channel. A trade-off between the ranging component integration times and the ranging signal-to-noise ratio to achieve a desired level of range measurement accuracy and the probability of error in the code components is also presented. Numerical results presented illustrate the required trade-offs under various interference conditions.

47 CFR 27.1166 - Reimbursement under the Cost-Sharing Plan.

Code of Federal Regulations, 2010 CFR

2010-10-01

... frequency band may seek full reimbursement through the clearinghouse of compensable costs, up to the... act in good faith in satisfying the cost-sharing obligations under §§ 27.1160 through 27.1174. The... interference from MSS space-to-Earth downlink operations, but may elect to do so, in which case the MSS...

47 CFR 27.1166 - Reimbursement under the Cost-Sharing Plan.

Code of Federal Regulations, 2011 CFR

2011-10-01

... frequency band may seek full reimbursement through the clearinghouse of compensable costs, up to the... act in good faith in satisfying the cost-sharing obligations under §§ 27.1160 through 27.1174. The... interference from MSS space-to-Earth downlink operations, but may elect to do so, in which case the MSS...

47 CFR 27.1166 - Reimbursement under the Cost-Sharing Plan.

Code of Federal Regulations, 2012 CFR

2012-10-01

... frequency band may seek full reimbursement through the clearinghouse of compensable costs, up to the... act in good faith in satisfying the cost-sharing obligations under §§ 27.1160 through 27.1174. The... interference from MSS space-to-Earth downlink operations, but may elect to do so, in which case the MSS...

Beam Design and User Scheduling for Nonorthogonal Multiple Access With Multiple Antennas Based on Pareto Optimality

NASA Astrophysics Data System (ADS)

Seo, Junyeong; Sung, Youngchul

2018-06-01

In this paper, an efficient transmit beam design and user scheduling method is proposed for multi-user (MU) multiple-input single-output (MISO) non-orthogonal multiple access (NOMA) downlink, based on Pareto-optimality. The proposed beam design and user scheduling method groups simultaneously-served users into multiple clusters with practical two users in each cluster, and then applies spatical zeroforcing (ZF) across clusters to control inter-cluster interference (ICI) and Pareto-optimal beam design with successive interference cancellation (SIC) to two users in each cluster to remove interference to strong users and leverage signal-to-interference-plus-noise ratios (SINRs) of interference-experiencing weak users. The proposed method has flexibility to control the rates of strong and weak users and numerical results show that the proposed method yields good performance.

Estimation and Mitigation of Channel Non-Reciprocity in Massive MIMO

NASA Astrophysics Data System (ADS)

Raeesi, Orod; Gokceoglu, Ahmet; Valkama, Mikko

2018-05-01

Time-division duplex (TDD) based massive MIMO systems rely on the reciprocity of the wireless propagation channels when calculating the downlink precoders based on uplink pilots. However, the effective uplink and downlink channels incorporating the analog radio front-ends of the base station (BS) and user equipments (UEs) exhibit non-reciprocity due to non-identical behavior of the individual transmit and receive chains. When downlink precoder is not aware of such channel non-reciprocity (NRC), system performance can be significantly degraded due to NRC induced interference terms. In this work, we consider a general TDD-based massive MIMO system where frequency-response mismatches at both the BS and UEs, as well as the mutual coupling mismatch at the BS large-array system all coexist and induce channel NRC. Based on the NRC-impaired signal models, we first propose a novel iterative estimation method for acquiring both the BS and UE side NRC matrices and then also propose a novel NRC-aware downlink precoder design which utilizes the obtained estimates. Furthermore, an efficient pilot signaling scheme between the BS and UEs is introduced in order to facilitate executing the proposed estimation method and the NRC-aware precoding technique in practical systems. Comprehensive numerical results indicate substantially improved spectral efficiency performance when the proposed NRC estimation and NRC-aware precoding methods are adopted, compared to the existing state-of-the-art methods.

Single- and dual-carrier microwave noise abatement in the deep space network. [microwave antennas

NASA Technical Reports Server (NTRS)

Bathker, D. A.; Brown, D. W.; Petty, S. M.

1975-01-01

The NASA/JPL Deep Space Network (DSN) microwave ground antenna systems are presented which simultaneously uplink very high power S-band signals while receiving very low level S- and X-band downlinks. Tertiary mechanisms associated with elements give rise to self-interference in the forms of broadband noise burst and coherent intermodulation products. A long-term program to reduce or eliminate both forms of interference is described in detail. Two DSN antennas were subjected to extensive interference testing and practical cleanup program; the initial performance, modification details, and final performance achieved at several planned stages are discussed. Test equipment and field procedures found useful in locating interference sources are discussed. Practices deemed necessary for interference-free operations in the DSN are described. Much of the specific information given is expected to be easily generalized for application in a variety of similar installations. Recommendations for future investigations and individual element design are given.

Viking telecommunication effects of GEOS satellite interference based on testing at the Madrid deep space station

NASA Technical Reports Server (NTRS)

Stuhr, F. V.; Kent, S. S.; Galvez, J. L.; Luaces, B. G.; Pasero, G. R.; Urech, J. M.

1976-01-01

In support of the ongoing NASA-European Space Agency (ESA) effort to understand and control possible interference between missions, testing was conducted at the Madrid Deep Space Station from July 1975 to February 1976 to characterize the effect on Viking 1975 telecommunication link performance of Geodetic Earth-Orbiting Satellite (GEOS) downlink signals. The prime use of the data was to develop a capability to predict GEOS interference effects for evaluation of Viking 1975 mission impacts and possible temporary GEOS shutdown. Also, the data would serve as a basis for assessment of the GEOS impact on missions other than Viking as well as for more general interference applications. Performances of the reference receiver, telemetry, and planetary ranging were measured in the presence of various types of GEOS-related interference, including an unmodulated GEOS carrier and simulation of the actual spectrum by an ESA-supplied GEOS suitcase model.

A Space-Time Signal Decomposition Algorithm for Downlink MIMO DS-CDMA Receivers

NASA Astrophysics Data System (ADS)

Wang, Yung-Yi; Fang, Wen-Hsien; Chen, Jiunn-Tsair

We propose a dimension reduction algorithm for the receiver of the downlink of direct-sequence code-division multiple access (DS-CDMA) systems in which both the transmitters and the receivers employ antenna arrays of multiple elements. To estimate the high order channel parameters, we develop a layered architecture using dimension-reduced parameter estimation algorithms to estimate the frequency-selective multipath channels. In the proposed architecture, to exploit the space-time geometric characteristics of multipath channels, spatial beamformers and constrained (or unconstrained) temporal filters are adopted for clustered-multipath grouping and path isolation. In conjunction with the multiple access interference (MAI) suppression techniques, the proposed architecture jointly estimates the direction of arrivals, propagation delays, and fading amplitudes of the downlink fading multipaths. With the outputs of the proposed architecture, the signals of interest can then be naturally detected by using path-wise maximum ratio combining. Compared to the traditional techniques, such as the Joint-Angle-and-Delay-Estimation (JADE) algorithm for DOA-delay joint estimation and the space-time minimum mean square error (ST-MMSE) algorithm for signal detection, computer simulations show that the proposed algorithm substantially mitigate the computational complexity at the expense of only slight performance degradation.

DS-CDMA satellite diversity reception for personal satellite communication: Downlink performance analysis

NASA Technical Reports Server (NTRS)

DeGaudenzi, Riccardo; Giannetti, Filippo

1995-01-01

The downlink of a satellite-mobile personal communication system employing power-controlled Direct Sequence Code Division Multiple Access (DS-CDMA) and exploiting satellite-diversity is analyzed and its performance compared with a more traditional communication system utilizing single satellite reception. The analytical model developed has been thoroughly validated by means of extensive Monte Carlo computer simulations. It is shown how the capacity gain provided by diversity reception shrinks considerably in the presence of increasing traffic or in the case of light shadowing conditions. Moreover, the quantitative results tend to indicate that to combat system capacity reduction due to intra-system interference, no more than two satellites shall be active over the same region. To achieve higher system capacity, differently from terrestrial cellular systems, Multi-User Detection (MUD) techniques are likely to be required in the mobile user terminal, thus considerably increasing its complexity.

The influence of the uplink noise on the performance of satellite data transmission systems

NASA Astrophysics Data System (ADS)

Dewal, Vrinda P.

The problem of transmission of binary phase shift keying (BPSK) modulated digital data through a bandlimited nonlinear satellite channel in the presence of uplink, downlink Gaussian noise and intersymbol interface is examined. The satellite transponder is represented by a zero memory bandpass nonlinearity, with AM/AM conversion. The proposed optimum linear receiver structure consists of tapped-delay lines followed by a decision device. The linear receiver is designed to minimize the mean square error that is a function of the intersymbol interface, the uplink and the downlink noise. The minimum mean square error equalizer (MMSE) is derived using the Wiener-Kolmogorov theory. In this receiver, the decision about the transmitted signal is made by taking into account the received sequence of present sample, and the interfering past and future samples, which represent the intersymbol interference (ISI). Illustrative examples of the receiver structures are considered for the nonlinear channels with a symmetrical and asymmetrical frequency responses of the transmitter filter. The transponder nonlinearity is simulated by a polynomial using only the first and the third orders terms. A computer simulation determines the tap gain coefficients of the MMSE equalizer that adapt to the various uplink and downlink noise levels. The performance of the MMSE equalizer is evaluated in terms of an estimate of the average probability of error.

Optimum Adaptive Modulation and Channel Coding Scheme for Frequency Domain Channel-Dependent Scheduling in OFDM Based Evolved UTRA Downlink

NASA Astrophysics Data System (ADS)

Miki, Nobuhiko; Kishiyama, Yoshihisa; Higuchi, Kenichi; Sawahashi, Mamoru; Nakagawa, Masao

In the Evolved UTRA (UMTS Terrestrial Radio Access) downlink, Orthogonal Frequency Division Multiplexing (OFDM) based radio access was adopted because of its inherent immunity to multipath interference and flexible accommodation of different spectrum arrangements. This paper presents the optimum adaptive modulation and channel coding (AMC) scheme when resource blocks (RBs) is simultaneously assigned to the same user when frequency and time domain channel-dependent scheduling is assumed in the downlink OFDMA radio access with single-antenna transmission. We start by presenting selection methods for the modulation and coding scheme (MCS) employing mutual information both for RB-common and RB-dependent modulation schemes. Simulation results show that, irrespective of the application of power adaptation to RB-dependent modulation, the improvement in the achievable throughput of the RB-dependent modulation scheme compared to that for the RB-common modulation scheme is slight, i.e., 4 to 5%. In addition, the number of required control signaling bits in the RB-dependent modulation scheme becomes greater than that for the RB-common modulation scheme. Therefore, we conclude that the RB-common modulation and channel coding rate scheme is preferred, when multiple RBs of the same coded stream are assigned to one user in the case of single-antenna transmission.

Self-Coexistence among IEEE 802.22 Networks: Distributed Allocation of Power and Channel

PubMed Central

Sakin, Sayef Azad; Alamri, Atif; Tran, Nguyen H.

2017-01-01

Ensuring self-coexistence among IEEE 802.22 networks is a challenging problem owing to opportunistic access of incumbent-free radio resources by users in co-located networks. In this study, we propose a fully-distributed non-cooperative approach to ensure self-coexistence in downlink channels of IEEE 802.22 networks. We formulate the self-coexistence problem as a mixed-integer non-linear optimization problem for maximizing the network data rate, which is an NP-hard one. This work explores a sub-optimal solution by dividing the optimization problem into downlink channel allocation and power assignment sub-problems. Considering fairness, quality of service and minimum interference for customer-premises-equipment, we also develop a greedy algorithm for channel allocation and a non-cooperative game-theoretic framework for near-optimal power allocation. The base stations of networks are treated as players in a game, where they try to increase spectrum utilization by controlling power and reaching a Nash equilibrium point. We further develop a utility function for the game to increase the data rate by minimizing the transmission power and, subsequently, the interference from neighboring networks. A theoretical proof of the uniqueness and existence of the Nash equilibrium has been presented. Performance improvements in terms of data-rate with a degree of fairness compared to a cooperative branch-and-bound-based algorithm and a non-cooperative greedy approach have been shown through simulation studies. PMID:29215591

Self-Coexistence among IEEE 802.22 Networks: Distributed Allocation of Power and Channel.

PubMed

Sakin, Sayef Azad; Razzaque, Md Abdur; Hassan, Mohammad Mehedi; Alamri, Atif; Tran, Nguyen H; Fortino, Giancarlo

2017-12-07

Ensuring self-coexistence among IEEE 802.22 networks is a challenging problem owing to opportunistic access of incumbent-free radio resources by users in co-located networks. In this study, we propose a fully-distributed non-cooperative approach to ensure self-coexistence in downlink channels of IEEE 802.22 networks. We formulate the self-coexistence problem as a mixed-integer non-linear optimization problem for maximizing the network data rate, which is an NP-hard one. This work explores a sub-optimal solution by dividing the optimization problem into downlink channel allocation and power assignment sub-problems. Considering fairness, quality of service and minimum interference for customer-premises-equipment, we also develop a greedy algorithm for channel allocation and a non-cooperative game-theoretic framework for near-optimal power allocation. The base stations of networks are treated as players in a game, where they try to increase spectrum utilization by controlling power and reaching a Nash equilibrium point. We further develop a utility function for the game to increase the data rate by minimizing the transmission power and, subsequently, the interference from neighboring networks. A theoretical proof of the uniqueness and existence of the Nash equilibrium has been presented. Performance improvements in terms of data-rate with a degree of fairness compared to a cooperative branch-and-bound-based algorithm and a non-cooperative greedy approach have been shown through simulation studies.

Near-field self-interference cancellation and quality of service multicast beamforming in full-duplex

NASA Astrophysics Data System (ADS)

Wu, Fei; Shao, Shihai; Tang, Youxi

2016-10-01

To enable simultaneous multicast downlink transmit and receive operations on the same frequency band, also known as full-duplex links between an access point and mobile users. The problem of minimizing the total power of multicast transmit beamforming is considered from the viewpoint of ensuring the suppression amount of near-field line-of-sight self-interference and guaranteeing prescribed minimum signal-to-interference-plus-noise-ratio (SINR) at each receiver of the multicast groups. Based on earlier results for multicast groups beamforming, the joint problem is easily shown to be NP-hard. A semidefinite relaxation (SDR) technique with linear program power adjust method is proposed to solve the NP-hard problem. Simulation shows that the proposed method is feasible even when the local receive antenna in nearfield and the mobile user in far-filed are in the same direction.

Coexistence Analysis of Civil Unmanned Aircraft Systems at Low Altitudes

NASA Astrophysics Data System (ADS)

Zhou, Yuzhe

2016-11-01

The requirement of unmanned aircraft systems in civil areas is growing. However, provisioning of flight efficiency and safety of unmanned aircraft has critical requirements on wireless communication spectrum resources. Current researches mainly focus on spectrum availability. In this paper, the unmanned aircraft system communication models, including the coverage model and data rate model, and two coexistence analysis procedures, i. e. the interference and noise ratio criterion and frequency-distance-direction criterion, are proposed to analyze spectrum requirements and interference results of the civil unmanned aircraft systems at low altitudes. In addition, explicit explanations are provided. The proposed coexistence analysis criteria are applied to assess unmanned aircraft systems' uplink and downlink interference performances and to support corresponding spectrum planning. Numerical results demonstrate that the proposed assessments and analysis procedures satisfy requirements of flexible spectrum accessing and safe coexistence among multiple unmanned aircraft systems.

Advanced technology for a satellite multichannel demultiplexer/demodulator

NASA Technical Reports Server (NTRS)

Abramovitz, Irwin J.; Flechsig, Drew E.; Matteis, Richard M., Jr.

1994-01-01

Satellite on-board processing is needed to efficiently service multiple users while at the same time minimizing earth station complexity. The processing satellite receives a wideband uplink at 30 GHz and down-converts it to a suitable intermediate frequency. A multichannel demultiplexer then separates the composite signal into discrete channels. Each channel is then demodulated by bulk demodulators, with the baseband signals routed to the downlink processor for retransmission to the receiving earth stations. This type of processing circumvents many of the difficulties associated with traditional bent-pipe repeater satellites. Uplink signal distortion and interference are not retransmitted on the downlink. Downlink power can be allocated in accordance with user needs, independent of uplink transmissions. This allows the uplink users to employ different data rates as well as different modulation and coding schemes. In addition, all downlink users have a common frequency standard and symbol clock on the satellite, which is useful for network synchronization in time division multiple access schemes. The purpose of this program is to demonstrate the concept of an optically implemented multichannel demultiplexer (MCD). A proof-of-concept (POC) model has been developed which has the ability to receive a 40 MHz wide composite signal consisting of up to 1000 40 kHz QPSK modulated channels and perform the demultiplexing process. In addition a set of special test equipment (STE) has been configured to evaluate the performance of the POC model. The optical MCD is realized as an acousto-optic spectrum analyzer utilizing the capability of Bragg cells to perform the required channelization. These Bragg cells receive an optical input from a laser source and an RF input (the signal). The Bragg interaction causes optical output diffractions at angles proportional to the RF input frequency. These discrete diffractions are optically detected and output to individual demodulators for baseband conversion. Optimization of the MCD design was conducted in order to achieve a compromise between two opposing sources of signal degradation: adjacent channel interference and intersymbol interference. The system was also optimized to allow simple, inexpensive ground stations communications with the MCD. These design goals led to the realization of a POC MCD which demonstrates the demultiplexing function with minimal signal degradation. Performance evaluation results using the STE equipment indicate that the dynamic range of the demultiplexer in the presence of adjacent and multiple channel loading is 40 - 50 dB. Measured bit error rate (BER) probabilities varied from the predicted theoretical results by one dB or less. The performance of the proof-of-concept model indicate that the development of a space qualified optically implemented MCD are feasible. The advantages to such an implementation include reduced size, weight and power and increased reliability when compared with electronic approaches. All of these factors are critical to on-board satellite processors. Further optimization can be conducted which trade ground station complexity and MCD performance to achieve desired system results.

Engineering calculations for solving the orbital allotment problem

NASA Technical Reports Server (NTRS)

Reilly, C.; Walton, E. K.; Mount-Campbell, C.; Caldecott, R.; Aebker, E.; Mata, F.

1988-01-01

Four approaches for calculating downlink interferences for shaped-beam antennas are described. An investigation of alternative mixed-integer programming models for satellite synthesis is summarized. Plans for coordinating the various programs developed under this grant are outlined. Two procedures for ordering satellites to initialize the k-permutation algorithm are proposed. Results are presented for the k-permutation algorithms. Feasible solutions are found for 5 of the 6 problems considered. Finally, it is demonstrated that the k-permutation algorithm can be used to solve arc allotment problems.

Impulsive interference in communication channels and its mitigation by SPART and other nonlinear filters

NASA Astrophysics Data System (ADS)

Nikitin, Alexei V.; Epard, Marc; Lancaster, John B.; Lutes, Robert L.; Shumaker, Eric A.

2012-12-01

A strong digital communication transmitter in close physical proximity to a receiver of a weak signal can noticeably interfere with the latter even when the respective channels are tens or hundreds of megahertz apart. When time domain observations are made in the signal chain of the receiver between the first mixer and the baseband, this interference is likely to appear impulsive. The impulsive nature of this interference provides an opportunity to reduce its power by nonlinear filtering, improving the quality of the receiver channel. This article describes the mitigation, by a particular nonlinear filter, of the impulsive out-of-band (OOB) interference induced in High Speed Downlink Packet Access (HSDPA) by WiFi transmissions, protocols which coexist in many 3G smartphones and mobile hotspots. Our measurements show a decrease in the maximum error-free bit rate of a 1.95 GHz HSDPA receiver caused by the impulsive interference from an OOB 2.4 GHz WiFi transmission, sometimes down to a small fraction of the rate observed in the absence of the interference. We apply a nonlinear SPART filter to recover a noticeable portion of the lost rate and maintain an error-free connection under much higher levels of the WiFi interference than a receiver that does not contain such a filter. These measurements support our wider investigation of OOB interference resulting from digital modulation, which appears impulsive in a receiver, and its mitigation by nonlinear filters.

Real-Time Distributed Implementation of Interference Alignment with Analog Feedback

DTIC Science & Technology

2013-01-01

manner as in Figure 5(a). As such, six OFDM symbols are transmitted for our three user 2 × 2 MIMO system. The training does not experience precoding nor...pp. 159170, August 2009. [12] O. E. Ayach, S.W. Peters, and R.W. Heath Jr., ”The feasibility of interference alignment over measured MIMO - OFDM ...A Space-Time Receiver with Joint Synchronization and Interference Cancellation in Asynchronous MIMO - OFDM Systems,” IEEE Transactions on Vehicular

Assignment of channels and polarisations in a broadcasting satellite service environment

NASA Astrophysics Data System (ADS)

Fortes, J. M. P.

1986-07-01

In the process of synthesizing a satellite communications plan, a large number of possible configurations has to be analyzed in a short amount of time. An important part of the process concerns the allocation of channels and polarizations to the various systems. It is, of course, desirable to make these allocations based on the aggregate carrier/interference ratios, but this needs a considerable amount of time, and for this reason the single-entry carrier/interference criterion is usually employed. The paper presents an integer programming model based on an approximate evaluation of the aggregate carrier/interference ratios, which is fast enough to justify its application in the synthesis process. It was developed to help the elaboration of a downlink plan for the broadcasting satellite service (BSS) of North, Central, and South America. The official software package of the 1983 Administrative Radio Conference (RARC 83), responsible for the planning of the BSS in region 2, contains a routine based on this model.

On base station cooperation using statistical CSI in jointly correlated MIMO downlink channels

NASA Astrophysics Data System (ADS)

Zhang, Jun; Jiang, Bin; Jin, Shi; Gao, Xiqi; Wong, Kai-Kit

2012-12-01

This article studies the transmission of a single cell-edge user's signal using statistical channel state information at cooperative base stations (BSs) with a general jointly correlated multiple-input multiple-output (MIMO) channel model. We first present an optimal scheme to maximize the ergodic sum capacity with per-BS power constraints, revealing that the transmitted signals of all BSs are mutually independent and the optimum transmit directions for each BS align with the eigenvectors of the BS's own transmit correlation matrix of the channel. Then, we employ matrix permanents to derive a closed-form tight upper bound for the ergodic sum capacity. Based on these results, we develop a low-complexity power allocation solution using convex optimization techniques and a simple iterative water-filling algorithm (IWFA) for power allocation. Finally, we derive a necessary and sufficient condition for which a beamforming approach achieves capacity for all BSs. Simulation results demonstrate that the upper bound of ergodic sum capacity is tight and the proposed cooperative transmission scheme increases the downlink system sum capacity considerably.

Joint Interference Alignment and Power Allocation for K-User Multicell MIMO Channel through Staggered Antenna Switching.

PubMed

Selvaprabhu, Poongundran; Chinnadurai, Sunil; Sarker, Md Abdul Latif; Lee, Moon Ho

2018-01-28

In this paper, we characterise the joint interference alignment (IA) and power allocation strategies for a K -user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with blind-IA through staggered antenna switching on the receiver. We explore the power allocation and feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired signals and interference signals to cancel the common interference signals because the received signal must have a corresponding independent signal subspace. The capacity for a K -user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised. Furthermore, we show that the proposed K -user multicell MIMO scheduling and K -user L -cell CEUs partial cooperation algorithms elaborate the generalisation of K -user IA and power allocation strategies. The numerical results demonstrate that the proposed intercell interference scheme with partial-cooperative CE MUs achieves better capacity and signal-to-interference plus noise ratio (SINR) performance compared to noncooperative CE MUs and without intercell interference schemes.

Joint Interference Alignment and Power Allocation for K-User Multicell MIMO Channel through Staggered Antenna Switching

PubMed Central

2018-01-01

In this paper, we characterise the joint interference alignment (IA) and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with blind-IA through staggered antenna switching on the receiver. We explore the power allocation and feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired signals and interference signals to cancel the common interference signals because the received signal must have a corresponding independent signal subspace. The capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised. Furthermore, we show that the proposed K-user multicell MIMO scheduling and K-user L-cell CEUs partial cooperation algorithms elaborate the generalisation of K-user IA and power allocation strategies. The numerical results demonstrate that the proposed intercell interference scheme with partial-cooperative CE MUs achieves better capacity and signal-to-interference plus noise ratio (SINR) performance compared to noncooperative CE MUs and without intercell interference schemes. PMID:29382100

The Communication Link and Error ANalysis (CLEAN) simulator

NASA Technical Reports Server (NTRS)

Ebel, William J.; Ingels, Frank M.; Crowe, Shane

1993-01-01

During the period July 1, 1993 through December 30, 1993, significant developments to the Communication Link and Error ANalysis (CLEAN) simulator were completed and include: (1) Soft decision Viterbi decoding; (2) node synchronization for the Soft decision Viterbi decoder; (3) insertion/deletion error programs; (4) convolutional encoder; (5) programs to investigate new convolutional codes; (6) pseudo-noise sequence generator; (7) soft decision data generator; (8) RICE compression/decompression (integration of RICE code generated by Pen-Shu Yeh at Goddard Space Flight Center); (9) Markov Chain channel modeling; (10) percent complete indicator when a program is executed; (11) header documentation; and (12) help utility. The CLEAN simulation tool is now capable of simulating a very wide variety of satellite communication links including the TDRSS downlink with RFI. The RICE compression/decompression schemes allow studies to be performed on error effects on RICE decompressed data. The Markov Chain modeling programs allow channels with memory to be simulated. Memory results from filtering, forward error correction encoding/decoding, differential encoding/decoding, channel RFI, nonlinear transponders and from many other satellite system processes. Besides the development of the simulation, a study was performed to determine whether the PCI provides a performance improvement for the TDRSS downlink. There exist RFI with several duty cycles for the TDRSS downlink. We conclude that the PCI does not improve performance for any of these interferers except possibly one which occurs for the TDRS East. Therefore, the usefulness of the PCI is a function of the time spent transmitting data to the WSGT through the TDRS East transponder.

Tomlinson-Harashima Precoding for Multiuser MIMO Systems With Quantized CSI Feedback and User Scheduling

NASA Astrophysics Data System (ADS)

Sun, Liang; McKay, Matthew R.

2014-08-01

This paper studies the sum rate performance of a low complexity quantized CSI-based Tomlinson-Harashima (TH) precoding scheme for downlink multiuser MIMO tansmission, employing greedy user selection. The asymptotic distribution of the output signal to interference plus noise ratio of each selected user and the asymptotic sum rate as the number of users K grows large are derived by using extreme value theory. For fixed finite signal to noise ratios and a finite number of transmit antennas $n_T$, we prove that as K grows large, the proposed approach can achieve the optimal sum rate scaling of the MIMO broadcast channel. We also prove that, if we ignore the precoding loss, the average sum rate of this approach converges to the average sum capacity of the MIMO broadcast channel. Our results provide insights into the effect of multiuser interference caused by quantized CSI on the multiuser diversity gain.

Optical beat interference noise reduction in OFDMA optical access link using self-homodyne balanced detection

NASA Astrophysics Data System (ADS)

Jung, Sang-Min; Won, Yong-Yuk; Han, Sang-Kook

2013-12-01

A Novel technique for reducing the OBI noise in optical OFDMA-PON uplink is presented. OFDMA is a multipleaccess/ multiplexing scheme that can provide multiplexing operation of user data streams onto the downlink sub-channels and uplink multiple access by means of dividing OFDM subcarriers as sub-channels. The main issue of high-speed, single-wavelength upstream OFDMA-PON arises from optical beating interference noise. Because the sub-channels are allocated dynamically to multiple access users over same nominal wavelength, it generates the optical beating interference among upstream signals. In this paper, we proposed a novel scheme using self-homodyne balanced detection in the optical line terminal (OLT) to reduce OBI noise which is generated in the uplink transmission of OFDMA-PON system. When multiple OFDMA sub-channels over the same nominal wavelength are received at the same time in the proposed architecture, OBI noises can be removed using balanced detection. Using discrete multitone modulation (DMT) to generate real valued OFDM signals, the proposed technique is verified through experimental demonstration.

Cooperative Interference Alignment for the Multiple Access Channel

DTIC Science & Technology

2015-11-01

Communications. I. INTRODUCTION Conventional wireless networks were previously thought to be interference-limited, where interference is mainly caused by...interference-free capacity for any number of users K at high SNR. This fundamental result showed that wireless networks are not interference-limited as...decoding of the K users’ messages. This is applicable in uplink transmissions in cellular communications, where mobiles transmit independent messages

High Throughput via Cross-Layer Interference Alignment for Mobile Ad Hoc Networks

DTIC Science & Technology

2013-08-26

MIMO zero-forcing receiver in the presence of channel estimation error,” IEEE Transactions on Wireless Communications , vol. 6 , no. 3, pp. 805–810, Mar...Robert W. Heath, Nachiappan Valliappan. Antenna Subset Modulation for Secure Millimeter-Wave Wireless Communication , IEEE Transactions on...in MIMO Interference Alignment Networks, IEEE Transactions on Wireless Communications , (02 2012): 0. doi: 10.1109/TWC.2011.120511.111088 TOTAL: 2

A Wideband Satcom Based Avionics Network with CDMA Uplink and TDM Downlink

NASA Technical Reports Server (NTRS)

Agrawal, D.; Johnson, B. S.; Madhow, U.; Ramchandran, K.; Chun, K. S.

2000-01-01

The purpose of this paper is to describe some key technical ideas behind our vision of a future satcom based digital communication network for avionics applications The key features of our design are as follows: (a) Packetized transmission to permit efficient use of system resources for multimedia traffic; (b) A time division multiplexed (TDM) satellite downlink whose physical layer is designed to operate the satellite link at maximum power efficiency. We show how powerful turbo codes (invented originally for linear modulation) can be used with nonlinear constant envelope modulation, thus permitting the satellite amplifier to operate in a power efficient nonlinear regime; (c) A code division multiple access (CDMA) satellite uplink, which permits efficient access to the satellite from multiple asynchronous users. Closed loop power control is difficult for bursty packetized traffic, especially given the large round trip delay to the satellite. We show how adaptive interference suppression techniques can be used to deal with the ensuing near-far problem; (d) Joint source-channel coding techniques are required both at the physical and the data transport layer to optimize the end-to-end performance. We describe a novel approach to multiple description image encoding at the data transport layer in this paper.

Blind information-theoretic multiuser detection algorithms for DS-CDMA and WCDMA downlink systems.

PubMed

Waheed, Khuram; Salem, Fathi M

2005-07-01

Code division multiple access (CDMA) is based on the spread-spectrum technology and is a dominant air interface for 2.5G, 3G, and future wireless networks. For the CDMA downlink, the transmitted CDMA signals from the base station (BS) propagate through a noisy multipath fading communication channel before arriving at the receiver of the user equipment/mobile station (UE/MS). Classical CDMA single-user detection (SUD) algorithms implemented in the UE/MS receiver do not provide the required performance for modern high data-rate applications. In contrast, multi-user detection (MUD) approaches require a lot of a priori information not available to the UE/MS. In this paper, three promising adaptive Riemannian contra-variant (or natural) gradient based user detection approaches, capable of handling the highly dynamic wireless environments, are proposed. The first approach, blind multiuser detection (BMUD), is the process of simultaneously estimating multiple symbol sequences associated with all the users in the downlink of a CDMA communication system using only the received wireless data and without any knowledge of the user spreading codes. This approach is applicable to CDMA systems with relatively short spreading codes but becomes impractical for systems using long spreading codes. We also propose two other adaptive approaches, namely, RAKE -blind source recovery (RAKE-BSR) and RAKE-principal component analysis (RAKE-PCA) that fuse an adaptive stage into a standard RAKE receiver. This adaptation results in robust user detection algorithms with performance exceeding the linear minimum mean squared error (LMMSE) detectors for both Direct Sequence CDMA (DS-CDMA) and wide-band CDMA (WCDMA) systems under conditions of congestion, imprecise channel estimation and unmodeled multiple access interference (MAI).

Molecular alignment dependent electron interference in attosecond ultraviolet photoionization

PubMed Central

Yuan, Kai-Jun; Bandrauk, André D.

2015-01-01

We present molecular photoionization processes by intense attosecond ultraviolet laser pulses from numerical solutions of time-dependent Schrödinger equations. Simulations preformed on a single electron diatomic H2+ show minima in molecular photoelectron energy spectra resulting from two center interference effects which depend strongly on molecular alignment. We attribute such sensitivity to the spatial orientation asymmetry of the photoionization process from the two nuclei. A similar influence on photoelectron kinetic energies is also presented. PMID:26798785

Linear Transceiver Design for Interference Alignment: Complexity and Computation

DTIC Science & Technology

2010-07-01

restriction on the choice of beamforming vector of node b. Thus, for any fixed transmit node b in H , there are multiple restriction sets, each...signal space can be chosen. The receive nodes in H can achieve interference alignment if and only if these restricted sets of one-dimensional signal...total number of restriction sets is at most linear in the number of edges in H and each restriction set contains at most two one-dimensional

Adaptive limited feedback for interference alignment in MIMO interference channels.

PubMed

Zhang, Yang; Zhao, Chenglin; Meng, Juan; Li, Shibao; Li, Li

2016-01-01

It is very important that the radar sensor network has autonomous capabilities such as self-managing, etc. Quite often, MIMO interference channels are applied to radar sensor networks, and for self-managing purpose, interference management in MIMO interference channels is critical. Interference alignment (IA) has the potential to dramatically improve system throughput by effectively mitigating interference in multi-user networks at high signal-to-noise (SNR). However, the implementation of IA predominantly relays on perfect and global channel state information (CSI) at all transceivers. A large amount of CSI has to be fed back to all transmitters, resulting in a proliferation of feedback bits. Thus, IA with limited feedback has been introduced to reduce the sum feedback overhead. In this paper, by exploiting the advantage of heterogeneous path loss, we first investigate the throughput of IA with limited feedback in interference channels while each user transmits multi-streams simultaneously, then we get the upper bound of sum rate in terms of the transmit power and feedback bits. Moreover, we propose a dynamic feedback scheme via bit allocation to reduce the throughput loss due to limited feedback. Simulation results demonstrate that the dynamic feedback scheme achieves better performance in terms of sum rate.

Science Planning for the Solar Probe Plus NASA Mission

NASA Astrophysics Data System (ADS)

Kusterer, M. B.; Fox, N. J.; Turner, F. S.; Vandegriff, J. D.

2015-12-01

With a planned launch in 2018, there are a number of challenges for the Science Planning Team (SPT) of the Solar Probe Plus mission. The geometry of the celestial bodies and the spacecraft during some of the Solar Probe Plus mission orbits cause limited uplink and downlink opportunities. The payload teams must manage the volume of data that they write to the spacecraft solid-state recorders (SSR) for their individual instruments for downlink to the ground. The aim is to write the instrument data to the spacecraft SSR for downlink before a set of data downlink opportunities large enough to get the data to the ground and before the start of another data collection cycle. The SPT also intend to coordinate observations with other spacecraft and ground based systems. To add further complexity, two of the spacecraft payloads have the capability to write a large volumes of data to their internal payload SSR while sending a smaller "survey" portion of the data to the spacecraft SSR for downlink. The instrument scientists would then view the survey data on the ground, determine the most interesting data from their payload SSR, send commands to transfer that data from their payload SSR to the spacecraft SSR for downlink. The timing required for downlink and analysis of the survey data, identifying uplink opportunities for commanding data transfers, and downlink opportunities big enough for the selected data within the data collection period is critical. To solve these challenges, the Solar Probe Plus Science Working Group has designed a orbit-type optimized data file priority downlink scheme to downlink high priority survey data quickly. This file priority scheme would maximize the reaction time that the payload teams have to perform the survey and selected data method on orbits where the downlink and uplink availability will support using this method. An interactive display and analysis science planning tool is being designed for the SPT to use as an aid to planning. The tool will integrate the data file priority downlink scheme, payload data volume allocations, spacecraft ephemeris, attitude, downlink and uplink schedules, spacecraft and payload activities, and other spacecraft ephemeris. A prototype of the tool is in development using notional inputs obtained from the spacecraft engineering teams.

Radio Frequency Compatibility Evaluation of S Band Navigation Signals for Future BeiDou

PubMed Central

Sun, Yanbo; Xue, Rui; Zhao, Danfeng; Wang, Dun

2017-01-01

With L band frequency allocations for satellite navigation getting more crowded, S band (2483.5–2500 MHz) is already allocated for navigation services, where Globalstar broadcasts downlink communications to user terminals. The Indian Regional Navigation Satellite System (IRNSS) is transmitting navigation signals and Galileo exploits some potential signals in S band. Also, several candidate S band signals based on binary offset carrier (BOC), binary phase shift keying (BPSK), continuous phase modulation (CPM) and minimum shift keying-BOC (MSK-BOC) are suggested for BeiDou system (BDS). In quite narrow S band, mutual interference among these systems is inevitable, thus the compatibility issue is particularly significant for S band signal design. To explore desired S band signals for BDS, the paper firstly describes a comprehensive compatibility evaluation methods based on effective carrier-to-noise ratio degradation for acquisition and code tracking. Then a real simulation is established using space constellations, modulation schemes and received power. Finally, the worst mutual interference of BDS candidate signals with Galileo, IRNSS and Globalstar is calculated and compared. The results indicate that CPM signal is easier to allow peaceful coexistence of other systems with minimal mutual interference in S band compared to other BDS candidates. PMID:28475142

Non-Orthogonal Multiple Access for Ubiquitous Wireless Sensor Networks.

PubMed

Anwar, Asim; Seet, Boon-Chong; Ding, Zhiguo

2018-02-08

Ubiquitous wireless sensor networks (UWSNs) have become a critical technology for enabling smart cities and other ubiquitous monitoring applications. Their deployment, however, can be seriously hampered by the spectrum available to the sheer number of sensors for communication. To support the communication needs of UWSNs without requiring more spectrum resources, the power-domain non-orthogonal multiple access (NOMA) technique originally proposed for 5th Generation (5G) cellular networks is investigated for UWSNs for the first time in this paper. However, unlike 5G networks that operate in the licensed spectrum, UWSNs mostly operate in unlicensed spectrum where sensors also experience cross-technology interferences from other devices sharing the same spectrum. In this paper, we model the interferences from various sources at the sensors using stochastic geometry framework. To evaluate the performance, we derive a theorem and present new closed form expression for the outage probability of the sensors in a downlink scenario under interference limited environment. In addition, diversity analysis for the ordered NOMA users is performed. Based on the derived outage probability, we evaluate the average link throughput and energy consumption efficiency of NOMA against conventional orthogonal multiple access (OMA) technique in UWSNs. Further, the required computational complexity for the NOMA users is presented.

Radio Frequency Compatibility Evaluation of S Band Navigation Signals for Future BeiDou.

PubMed

Sun, Yanbo; Xue, Rui; Zhao, Danfeng; Wang, Dun

2017-05-05

With L band frequency allocations for satellite navigation getting more crowded, S band (2483.5-2500 MHz) is already allocated for navigation services, where Globalstar broadcasts downlink communications to user terminals. The Indian Regional Navigation Satellite System (IRNSS) is transmitting navigation signals and Galileo exploits some potential signals in S band. Also, several candidate S band signals based on binary offset carrier (BOC), binary phase shift keying (BPSK), continuous phase modulation (CPM) and minimum shift keying-BOC (MSK-BOC) are suggested for BeiDou system (BDS). In quite narrow S band, mutual interference among these systems is inevitable, thus the compatibility issue is particularly significant for S band signal design. To explore desired S band signals for BDS, the paper firstly describes a comprehensive compatibility evaluation methods based on effective carrier-to-noise ratio degradation for acquisition and code tracking. Then a real simulation is established using space constellations, modulation schemes and received power. Finally, the worst mutual interference of BDS candidate signals with Galileo, IRNSS and Globalstar is calculated and compared. The results indicate that CPM signal is easier to allow peaceful coexistence of other systems with minimal mutual interference in S band compared to other BDS candidates.

Interference-free SDMA for FBMC-OQAM

NASA Astrophysics Data System (ADS)

Horlin, François; Fickers, Jessica; Deleu, Thibault; Louveaux, Jérome

2013-12-01

Filter-bank multi-carrier (FBMC) modulations have recently been considered for the emerging wireless communication systems as a means to improve the utilization of the physical resources and the robustness to channel time variations. FBMC divides the overall frequency channel in a set of subchannels of bandwidth proportionally decreasing with the number of subchannels. If the number of subchannels is high enough, the bandwidth of each subchannel is small enough to assume that it is approximately flat. On the other hand, space-division multiple access (SDMA) is a recognized technique to support multiple access in the downlink of a multi-user system. The user signals are precoded at the base station equipped with multiple antennas to separate the users in the spatial domain. The application of SDMA to FBMC is unfortunately difficult when the channel is too frequency selective (or when the number of subchannels to too small) to assume flat subchannels. In that case, the system suffers from inter-symbol and inter-subchannel interference, besides the multi-user interference inherent to SDMA. State-of-the art solutions simply neglect the inter-symbol/subchannel interference. This article proposes a new SDMA precoder for FBMC capable of mitigating the three sources of interference. It is constructed per subchannel in order to keep an acceptable complexity and has the structure of a filter applied on each subchannel and its neighbors at twice the symbol rate. Numerical results demonstrate that the precoder can get rid of all the interference present in the system and benefit therefore from the diversity and power gains achievable with multiple antenna systems.

Spacecraft Reed-Solomon downlink module

NASA Technical Reports Server (NTRS)

Luong, Huy H. (Inventor); Donaldson, James A. (Inventor); Wood, Steven H. (Inventor)

1998-01-01

Apparatus and method for providing downlink frames to be transmitted from a spacecraft to a ground station. Each downlink frame includes a synchronization pattern and a transfer frame. The apparatus may comprise a monolithic Reed-Solomon downlink (RSDL) encoding chip coupled to data buffers for storing transfer frames. The RSKL chip includes a timing device, a bus interface, a timing and control unit, a synchronization pattern unit, and a Reed-Solomon encoding unit, and a bus arbiter.

Spreading Sequence System for Full Connectivity Relay Network

NASA Technical Reports Server (NTRS)

Kwon, Hyuck M. (Inventor); Pham, Khanh D. (Inventor); Yang, Jie (Inventor)

2018-01-01

Fully connected uplink and downlink fully connected relay network systems using pseudo-noise spreading and despreading sequences subjected to maximizing the signal-to-interference-plus-noise ratio. The relay network systems comprise one or more transmitting units, relays, and receiving units connected via a communication network. The transmitting units, relays, and receiving units each may include a computer for performing the methods and steps described herein and transceivers for transmitting and/or receiving signals. The computer encodes and/or decodes communication signals via optimum adaptive PN sequences found by employing Cholesky decompositions and singular value decompositions (SVD). The PN sequences employ channel state information (CSI) to more effectively and more securely computing the optimal sequences.

Complexity Analysis and Algorithms for Optimal Resource Allocation in Wireless Networks

DTIC Science & Technology

2012-09-01

independent orthogonal signaling such as OFDM . The general formulation will exploit the concept of ‘interference alignment’ which is known to provide...substantial rate gain over OFDM signalling for general interference channels. We have successfully analyzed the complexity to characterize the optimal...categories: PaperReceived Gennady Lyubeznik, Zhi-Quan Luo, Meisam Razaviyayn. On the degrees of freedom achievable through interference alignment in a MIMO

47 CFR 101.82 - Reimbursement and relocation expenses in the 2110-2150 MHz and 2160-2200 MHz bands.

Code of Federal Regulations, 2014 CFR

2014-10-01

... for space-to-Earth downlink in the 2130-2150 or 2180-2200 MHz bands) relocates an incumbent paired...) Cost-sharing obligations for MSS (space-to-Earth downlinks). For an MSS space-to-Earth downlink, the... standard successor, relative to the relocated microwave link. Subsequently entering MSS space-to-Earth...

47 CFR 101.82 - Reimbursement and relocation expenses in the 2110-2150 MHz and 2160-2200 MHz bands.

Code of Federal Regulations, 2012 CFR

2012-10-01

... for space-to-Earth downlink in the 2130-2150 or 2180-2200 MHz bands) relocates an incumbent paired...) Cost-sharing obligations for MSS (space-to-Earth downlinks). For an MSS space-to-Earth downlink, the... standard successor, relative to the relocated microwave link. Subsequently entering MSS space-to-Earth...

47 CFR 101.82 - Reimbursement and relocation expenses in the 2110-2150 MHz and 2160-2200 MHz bands.

Code of Federal Regulations, 2010 CFR

2010-10-01

... for space-to-Earth downlink in the 2130-2150 or 2180-2200 MHz bands) relocates an incumbent paired...) Cost-sharing obligations for MSS (space-to-Earth downlinks). For an MSS space-to-Earth downlink, the... standard successor, relative to the relocated microwave link. Subsequently entering MSS space-to-Earth...

47 CFR 101.82 - Reimbursement and relocation expenses in the 2110-2150 MHz and 2160-2200 MHz bands.

Code of Federal Regulations, 2013 CFR

2013-10-01

... for space-to-Earth downlink in the 2130-2150 or 2180-2200 MHz bands) relocates an incumbent paired...) Cost-sharing obligations for MSS (space-to-Earth downlinks). For an MSS space-to-Earth downlink, the... standard successor, relative to the relocated microwave link. Subsequently entering MSS space-to-Earth...

47 CFR 101.82 - Reimbursement and relocation expenses in the 2110-2150 MHz and 2160-2200 MHz bands.

Code of Federal Regulations, 2011 CFR

2011-10-01

... for space-to-Earth downlink in the 2130-2150 or 2180-2200 MHz bands) relocates an incumbent paired...) Cost-sharing obligations for MSS (space-to-Earth downlinks). For an MSS space-to-Earth downlink, the... standard successor, relative to the relocated microwave link. Subsequently entering MSS space-to-Earth...

47 CFR 27.19 - Requirements for operation of base and fixed stations in the 600 MHz downlink band in close...

Code of Federal Regulations, 2014 CFR

2014-10-01

... stations in the 600 MHz downlink band in close proximity to Radio Astronomy Observatories. 27.19 Section 27... base and fixed stations in the 600 MHz downlink band in close proximity to Radio Astronomy Observatories. (a) Licensees must make reasonable efforts to protect the radio astronomy observatory at Green...

Simulation of Downlink Synchronization for a Frequency-Hopped Satellite Communication System

DTIC Science & Technology

1992-04-01

naflonie SIMULATION OF DOWNLINK SYNCHRONIZATION FOR A FREQUENCY-HOPPED SATELLITE COMMUNICATION SYSTEM (U) by Lyle Waper_Communicadion and Xa elo Elkaoftron...is offset by an increase in complexity while establishing the communication link, termed synchronization . This document describes a downlink... synchronization process that involves the transmission of synchronization hops by the satellite and a two-step ground terminal synchonization procedure. In

CSI Feedback Reduction for MIMO Interference Alignment

NASA Astrophysics Data System (ADS)

Rao, Xiongbin; Ruan, Liangzhong; Lau, Vincent K. N.

2013-09-01

Interference alignment (IA) is a linear precoding strategy that can achieve optimal capacity scaling at high SNR in interference networks. Most of the existing IA designs require full channel state information (CSI) at the transmitters, which induces a huge CSI signaling cost. Hence it is desirable to improve the feedback efficiency for IA and in this paper, we propose a novel IA scheme with a significantly reduced CSI feedback. To quantify the CSI feedback cost, we introduce a novel metric, namely the feedback dimension. This metric serves as a first-order measurement of CSI feedback overhead. Due to the partial CSI feedback constraint, conventional IA schemes can not be applied and hence, we develop a novel IA precoder / decorrelator design and establish new IA feasibility conditions. Via dynamic feedback profile design, the proposed IA scheme can also achieve a flexible tradeoff between the degree of freedom (DoF) requirements for data streams, the antenna resources and the CSI feedback cost. We show by analysis and simulations that the proposed scheme achieves substantial reductions of CSI feedback overhead under the same DoF requirement in MIMO interference networks.

Reduction of ETS-VI Laser Communication Equipment Optical-Downlink Telemetry Collected During GOLD

NASA Technical Reports Server (NTRS)

Toyoshima, M.; Araki, K.; Arimoto, Y.; Toyoda, M.; Jeganathan, M.; Wilson, K.; Lesh, J. R.

1997-01-01

Free-space laser communications experiments were conducted between the laser communication equipment (LCE) on board the Japanese Engineering Test Satellite VI (ETS-VI) and the ground station located at the Table Mountain Facility (TMF) during late 1995 and early 1996. This article describes the on-line data reduction process used to decode LCE telemetry (called E2) downlinked on the optical carrier during the Ground/Orbiter Lasercomm Demonstration (GOLD) experiments. The LCE has the capability of transmitting real-time sensor and status information at 128 kbps by modulating the onboard diode laser. The optical downlink was detected on the ground, bit synchronized, and the resulting data stream stored on a data recorder. The recorded data were subsequently decoded by on-line data processing that included cross-correlation of the known telemetry data format and the downlink data stream. Signals obtained from the processing can be useful not only in evaluating the characteristics of the LCE but also in understanding uplink and downlink signal quality.

A Rapid Convergent Low Complexity Interference Alignment Algorithm for Wireless Sensor Networks.

PubMed

Jiang, Lihui; Wu, Zhilu; Ren, Guanghui; Wang, Gangyi; Zhao, Nan

2015-07-29

Interference alignment (IA) is a novel technique that can effectively eliminate the interference and approach the sum capacity of wireless sensor networks (WSNs) when the signal-to-noise ratio (SNR) is high, by casting the desired signal and interference into different signal subspaces. The traditional alternating minimization interference leakage (AMIL) algorithm for IA shows good performance in high SNR regimes, however, the complexity of the AMIL algorithm increases dramatically as the number of users and antennas increases, posing limits to its applications in the practical systems. In this paper, a novel IA algorithm, called directional quartic optimal (DQO) algorithm, is proposed to minimize the interference leakage with rapid convergence and low complexity. The properties of the AMIL algorithm are investigated, and it is discovered that the difference between the two consecutive iteration results of the AMIL algorithm will approximately point to the convergence solution when the precoding and decoding matrices obtained from the intermediate iterations are sufficiently close to their convergence values. Based on this important property, the proposed DQO algorithm employs the line search procedure so that it can converge to the destination directly. In addition, the optimal step size can be determined analytically by optimizing a quartic function. Numerical results show that the proposed DQO algorithm can suppress the interference leakage more rapidly than the traditional AMIL algorithm, and can achieve the same level of sum rate as that of AMIL algorithm with far less iterations and execution time.

Multilayer Optimization of Heterogeneous Networks Using Grammatical Genetic Programming.

PubMed

Fenton, Michael; Lynch, David; Kucera, Stepan; Claussen, Holger; O'Neill, Michael

2017-09-01

Heterogeneous cellular networks are composed of macro cells (MCs) and small cells (SCs) in which all cells occupy the same bandwidth. Provision has been made under the third generation partnership project-long term evolution framework for enhanced intercell interference coordination (eICIC) between cell tiers. Expanding on previous works, this paper instruments grammatical genetic programming to evolve control heuristics for heterogeneous networks. Three aspects of the eICIC framework are addressed including setting SC powers and selection biases, MC duty cycles, and scheduling of user equipments (UEs) at SCs. The evolved heuristics yield minimum downlink rates three times higher than a baseline method, and twice that of a state-of-the-art benchmark. Furthermore, a greater number of UEs receive transmissions under the proposed scheme than in either the baseline or benchmark cases.

Iterative MMSE Detection for MIMO/BLAST DS-CDMA Systems in Frequency Selective Fading Channels - Achieving High Performance in Fully Loaded Systems

NASA Astrophysics Data System (ADS)

Silva, João Carlos; Souto, Nuno; Cercas, Francisco; Dinis, Rui

A MMSE (Minimum Mean Square Error) DS-CDMA (Direct Sequence-Code Division Multiple Access) receiver coupled with a low-complexity iterative interference suppression algorithm was devised for a MIMO/BLAST (Multiple Input, Multiple Output / Bell Laboratories Layered Space Time) system in order to improve system performance, considering frequency selective fading channels. The scheme is compared against the simple MMSE receiver, for both QPSK and 16QAM modulations, under SISO (Single Input, Single Output) and MIMO systems, the latter with 2Tx by 2Rx and 4Tx by 4Rx (MIMO order 2 and 4 respectively) antennas. To assess its performance in an existing system, the uncoded UMTS HSDPA (High Speed Downlink Packet Access) standard was considered.

Downlink Multihop Transmission Technique for Asymmetric Traffic Accommodation in DS-CDMA/FDD Cellular Communications

NASA Astrophysics Data System (ADS)

Mori, Kazuo; Naito, Katsuhiro; Kobayashi, Hideo

This paper proposes an asymmetric traffic accommodation scheme using a multihop transmission technique for CDMA/FDD cellular communication systems. The proposed scheme exploits the multihop transmission to downlink packet transmissions, which require the large transmission power at their single-hop transmissions, in order to increase the downlink capacity. In these multihop transmissions, vacant uplink band is used for the transmissions from relay stations to destination mobile stations, and this leads more capacity enhancement in the downlink communications. The relay route selection method and power control method for the multihop transmissions are also investigated in the proposed scheme. The proposed scheme is evaluated by computer simulation and the results show that the proposed scheme can achieve better system performance.

Reference-Frame-Independent and Measurement-Device-Independent Quantum Key Distribution Using One Single Source

NASA Astrophysics Data System (ADS)

Li, Qian; Zhu, Changhua; Ma, Shuquan; Wei, Kejin; Pei, Changxing

2018-04-01

Measurement-device-independent quantum key distribution (MDI-QKD) is immune to all detector side-channel attacks. However, practical implementations of MDI-QKD, which require two-photon interferences from separated independent single-photon sources and a nontrivial reference alignment procedure, are still challenging with current technologies. Here, we propose a scheme that significantly reduces the experimental complexity of two-photon interferences and eliminates reference frame alignment by the combination of plug-and-play and reference frame independent MDI-QKD. Simulation results show that the secure communication distance can be up to 219 km in the finite-data case and the scheme has good potential for practical MDI-QKD systems.

Radiofrequency-electromagnetic field exposures in kindergarten children.

PubMed

Bhatt, Chhavi Raj; Redmayne, Mary; Billah, Baki; Abramson, Michael J; Benke, Geza

2017-09-01

The aim of this study was to assess environmental and personal radiofrequency-electromagnetic field (RF-EMF) exposures in kindergarten children. Ten children and 20 kindergartens in Melbourne, Australia participated in personal and environmental exposure measurements, respectively. Order statistics of RF-EMF exposures were computed for 16 frequency bands between 88 MHz and 5.8 GHz. Of the 16 bands, the three highest sources of environmental RF-EMF exposures were: Global System for Mobile Communications (GSM) 900 MHz downlink (82 mV/m); Universal Mobile Telecommunications System (UMTS) 2100MHz downlink (51 mV/m); and GSM 900 MHz uplink (45 mV/m). Similarly, the three highest personal exposure sources were: GSM 900 MHz downlink (50 mV/m); UMTS 2100 MHz downlink, GSM 900 MHz uplink and GSM 1800 MHz downlink (20 mV/m); and Frequency Modulation radio, Wi-Fi 2.4 GHz and Digital Video Broadcasting-Terrestrial (10 mV/m). The median environmental exposures were: 179 mV/m (total all bands), 123 mV/m (total mobile phone base station downlinks), 46 mV/m (total mobile phone base station uplinks), and 16 mV/m (Wi-Fi 2.4 GHz). Similarly, the median personal exposures were: 81 mV/m (total all bands), 62 mV/m (total mobile phone base station downlinks), 21 mV/m (total mobile phone base station uplinks), and 9 mV/m (Wi-Fi 2.4 GHz). The measurements showed that environmental RF-EMF exposure levels exceeded the personal RF-EMF exposure levels at kindergartens.

An MBS-Assisted Femtocell Transmit Power Control Scheme with Mobile User QoS Guarantee in 2-Tier Heterogeneous Femtocell Networks

PubMed Central

Yang, Chih-Cheng; Sheu, Shiann-Tsong

2013-01-01

This study investigates how to adjust the transmit power of femto base station (FBS) to mitigate interference problems between the FBSs and mobile users (MUs) in the 2-tier heterogeneous femtocell networks. A common baseline of deploying the FBS to increase the indoor access bandwidth requires that the FBS operation will not affect outdoor MUs operation with their quality-of-service (QoS) requirements. To tackle this technical problem, an FBS transmit power adjustment (FTPA) algorithm is proposed to adjust the FBS transmit power (FTP) to avoid unwanted cochannel interference (CCI) with the neighboring MUs in downlink transmission. FTPA reduces the FTP to serve its femto users (FUs) according to the QoS requirements of the nearest neighboring MUs to the FBS so that the MU QoS requirement is guaranteed. Simulation results demonstrate that FTPA can achieve a low MU outage probability as well as serve FUs without violating the MU QoS requirements. Simulation results also reveal that FTPA has better performance on voice and video services which are the major trend of future multimedia communication in the NGN. PMID:24391461

Optimizing Satellite Communications With Adaptive and Phased Array Antennas

NASA Technical Reports Server (NTRS)

Ingram, Mary Ann; Romanofsky, Robert; Lee, Richard Q.; Miranda, Felix; Popovic, Zoya; Langley, John; Barott, William C.; Ahmed, M. Usman; Mandl, Dan

2004-01-01

A new adaptive antenna array architecture for low-earth-orbiting satellite ground stations is being investigated. These ground stations are intended to have no moving parts and could potentially be operated in populated areas, where terrestrial interference is likely. The architecture includes multiple, moderately directive phased arrays. The phased arrays, each steered in the approximate direction of the satellite, are adaptively combined to enhance the Signal-to-Noise and Interference-Ratio (SNIR) of the desired satellite. The size of each phased array is to be traded-off with the number of phased arrays, to optimize cost, while meeting a bit-error-rate threshold. Also, two phased array architectures are being prototyped: a spacefed lens array and a reflect-array. If two co-channel satellites are in the field of view of the phased arrays, then multi-user detection techniques may enable simultaneous demodulation of the satellite signals, also known as Space Division Multiple Access (SDMA). We report on Phase I of the project, in which fixed directional elements are adaptively combined in a prototype to demodulate the S-band downlink of the EO-1 satellite, which is part of the New Millennium Program at NASA.

An analysis of bi-directional use of frequencies for satellite communications

NASA Technical Reports Server (NTRS)

Whyte, W. A., Jr.; Miller, E. F.; Sullivan, T.; Miller, J. E.

1986-01-01

The bi-directional use of frequencies allocated for space communications has the potential to double the orbit/spectrum capacity available. The technical feasibility of reverse band use (RBU) at C-band (4 GHz uplinks and 6 GHz downlinks) is studied. The analysis identifies the constraints under which both forward and reverse band use satellite systems can share the same frequencies with terrestrial, line of sight transmission systems. The results of the analysis show that RBU satellite systems can be similarly sized to forward band use (FBU) satellite systems. In addition, the orbital separation requirements between RBU and FBU satellite systems are examined. The analysis shows that a carrier to interference ratio of 45 dB can be maintianed between RBU and FBU satellites separated by less than 0.5 deg., and that a carrier to interference ratio of 42 dB can be maintained in the antipodal case. Rain scatter propagation analysis shows that RBU and FBU Earth stations require separation distances fo less than 10 km at a rain rate of 13.5 mm/hr escalating to less than 100 km at a rain rate of 178 mm/hr for Earth station antennas in the 3 to 10 m range.

An MBS-assisted femtocell transmit power control scheme with mobile user QoS guarantee in 2-tier heterogeneous femtocell networks.

PubMed

Chen, Jenhui; Yang, Chih-Cheng; Sheu, Shiann-Tsong

2013-01-01

This study investigates how to adjust the transmit power of femto base station (FBS) to mitigate interference problems between the FBSs and mobile users (MUs) in the 2-tier heterogeneous femtocell networks. A common baseline of deploying the FBS to increase the indoor access bandwidth requires that the FBS operation will not affect outdoor MUs operation with their quality-of-service (QoS) requirements. To tackle this technical problem, an FBS transmit power adjustment (FTPA) algorithm is proposed to adjust the FBS transmit power (FTP) to avoid unwanted cochannel interference (CCI) with the neighboring MUs in downlink transmission. FTPA reduces the FTP to serve its femto users (FUs) according to the QoS requirements of the nearest neighboring MUs to the FBS so that the MU QoS requirement is guaranteed. Simulation results demonstrate that FTPA can achieve a low MU outage probability as well as serve FUs without violating the MU QoS requirements. Simulation results also reveal that FTPA has better performance on voice and video services which are the major trend of future multimedia communication in the NGN.

Alignment-stabilized interference filter-tuned external-cavity quantum cascade laser.

PubMed

Kischkat, Jan; Semtsiv, Mykhaylo P; Elagin, Mikaela; Monastyrskyi, Grygorii; Flores, Yuri; Kurlov, Sergii; Peters, Sven; Masselink, W Ted

2014-12-01

A passively alignment-stabilized external cavity quantum cascade laser (EC-QCL) employing a "cat's eye"-type retroreflector and an ultra-narrowband transmissive interference filter for wavelength selection is demonstrated and experimentally investigated. Compared with conventional grating-tuned ECQCLs, the setup is nearly two orders of magnitude more stable against misalignment of the components, and spectral fluctuation is reduced by one order of magnitude, allowing for a simultaneously lightweight and fail-safe construction, suitable for applications outdoors and in space. It also allows for a substantially greater level of miniaturization and cost reduction. These advantages fit in well with the general properties of modern QCLs in the promise to deliver useful and affordable mid-infrared-light sources for a variety of spectroscopic and imaging applications.

Distilling two-center-interference information during tunneling of aligned molecules with orthogonally polarized two-color laser fields

NASA Astrophysics Data System (ADS)

Gao, F.; Chen, Y. J.; Xin, G. G.; Liu, J.; Fu, L. B.

2017-12-01

When electrons tunnel through a barrier formed by the strong laser field and the two-center potential of a diatomic molecule, a double-slit-like interference can occur. However, this interference effect can not be probed directly right now, as it is strongly coupled with other dynamical processes during tunneling. Here, we show numerically and analytically that orthogonally polarized two-color (OTC) laser fields are capable of resolving the interference effect in tunneling, while leaving clear footprints of this effect in photoelectron momentum distributions. Moreover, this effect can be manipulated by changing the relative field strength of OTC fields.

Parallel alignment of bacteria using near-field optical force array for cell sorting

NASA Astrophysics Data System (ADS)

Zhao, H. T.; Zhang, Y.; Chin, L. K.; Yap, P. H.; Wang, K.; Ser, W.; Liu, A. Q.

2017-08-01

This paper presents a near-field approach to align multiple rod-shaped bacteria based on the interference pattern in silicon nano-waveguide arrays. The bacteria in the optical field will be first trapped by the gradient force and then rotated by the scattering force to the equilibrium position. In the experiment, the Shigella bacteria is rotated 90 deg and aligned to horizontal direction in 9.4 s. Meanwhile, 150 Shigella is trapped on the surface in 5 min and 86% is aligned with angle < 5 deg. This method is a promising toolbox for the research of parallel single-cell biophysical characterization, cell-cell interaction, etc.

OLT-centralized sampling frequency offset compensation scheme for OFDM-PON.

PubMed

Chen, Ming; Zhou, Hui; Zheng, Zhiwei; Deng, Rui; Chen, Qinghui; Peng, Miao; Liu, Cuiwei; He, Jing; Chen, Lin; Tang, Xionggui

2017-08-07

We propose an optical line terminal (OLT)-centralized sampling frequency offset (SFO) compensation scheme for adaptively-modulated OFDM-PON systems. By using the proposed SFO scheme, the phase rotation and inter-symbol interference (ISI) caused by SFOs between OLT and multiple optical network units (ONUs) can be centrally compensated in the OLT, which reduces the complexity of ONUs. Firstly, the optimal fast Fourier transform (FFT) size is identified in the intensity-modulated and direct-detection (IMDD) OFDM system in the presence of SFO. Then, the proposed SFO compensation scheme including phase rotation modulation (PRM) and length-adaptive OFDM frame has been experimentally demonstrated in the downlink transmission of an adaptively modulated optical OFDM with the optimal FFT size. The experimental results show that up to ± 300 ppm SFO can be successfully compensated without introducing any receiver performance penalties.

Uplink Downlink Rate Balancing and Throughput Scaling in FDD Massive MIMO Systems

NASA Astrophysics Data System (ADS)

Bergel, Itsik; Perets, Yona; Shamai, Shlomo

2016-05-01

In this work we extend the concept of uplink-downlink rate balancing to frequency division duplex (FDD) massive MIMO systems. We consider a base station with large number antennas serving many single antenna users. We first show that any unused capacity in the uplink can be traded off for higher throughput in the downlink in a system that uses either dirty paper (DP) coding or linear zero-forcing (ZF) precoding. We then also study the scaling of the system throughput with the number of antennas in cases of linear Beamforming (BF) Precoding, ZF Precoding, and DP coding. We show that the downlink throughput is proportional to the logarithm of the number of antennas. While, this logarithmic scaling is lower than the linear scaling of the rate in the uplink, it can still bring significant throughput gains. For example, we demonstrate through analysis and simulation that increasing the number of antennas from 4 to 128 will increase the throughput by more than a factor of 5. We also show that a logarithmic scaling of downlink throughput as a function of the number of receive antennas can be achieved even when the number of transmit antennas only increases logarithmically with the number of receive antennas.

SPADER - Science Planning Analysis and Data Estimation Resource for the NASA Parker Solar Probe Mission

NASA Astrophysics Data System (ADS)

Rodgers, D. J.; Fox, N. J.; Kusterer, M. B.; Turner, F. S.; Woleslagle, A. B.

2017-12-01

Scheduled to launch in July 2018, the Parker Solar Probe (PSP) will orbit the Sun for seven years, making a total of twenty-four extended encounters inside a solar radial distance of 0.25 AU. During most orbits, there are extended periods of time where PSP-Sun-Earth geometry dramatically reduces PSP-Earth communications via the Deep Space Network (DSN); there is the possibility that multiple orbits will have little to no high-rate downlink available. Science and housekeeping data taken during an encounter may reside on the spacecraft solid state recorder (SSR) for multiple orbits, potentially running the risk of overflowing the SSR in the absence of mitigation. The Science Planning Analysis and Data Estimation Resource (SPADER) has been developed to provide the science and operations teams the ability to plan operations accounting for multiple orbits in order to mitigate the effects caused by the lack of high-rate downlink. Capabilities and visualizations of SPADER are presented; further complications associated with file downlink priority and high-speed data transfers between instrument SSRs and the spacecraft SSR are discussed, as well as the long-term consequences of variations in DSN downlink parameters on the science data downlink.

Automated interferometric alignment system for paraboloidal mirrors

DOEpatents

Maxey, L.C.

1993-09-28

A method is described for a systematic method of interpreting interference fringes obtained by using a corner cube retroreflector as an alignment aid when aligning a paraboloid to a spherical wavefront. This is applicable to any general case where such alignment is required, but is specifically applicable in the case of aligning an autocollimating test using a diverging beam wavefront. In addition, the method provides information which can be systematically interpreted such that independent information about pitch, yaw and focus errors can be obtained. Thus, the system lends itself readily to automation. Finally, although the method is developed specifically for paraboloids, it can be seen to be applicable to a variety of other aspheric optics when applied in combination with a wavefront corrector that produces a wavefront which, when reflected from the correctly aligned aspheric surface will produce a collimated wavefront like that obtained from the paraboloid when it is correctly aligned to a spherical wavefront. 14 figures.

Description and Simulation of a Fast Packet Switch Architecture for Communication Satellites

NASA Technical Reports Server (NTRS)

Quintana, Jorge A.; Lizanich, Paul J.

1995-01-01

The NASA Lewis Research Center has been developing the architecture for a multichannel communications signal processing satellite (MCSPS) as part of a flexible, low-cost meshed-VSAT (very small aperture terminal) network. The MCSPS architecture is based on a multifrequency, time-division-multiple-access (MF-TDMA) uplink and a time-division multiplex (TDM) downlink. There are eight uplink MF-TDMA beams, and eight downlink TDM beams, with eight downlink dwells per beam. The information-switching processor, which decodes, stores, and transmits each packet of user data to the appropriate downlink dwell onboard the satellite, has been fully described by using VHSIC (Very High Speed Integrated-Circuit) Hardware Description Language (VHDL). This VHDL code, which was developed in-house to simulate the information switching processor, showed that the architecture is both feasible and viable. This paper describes a shared-memory-per-beam architecture, its VHDL implementation, and the simulation efforts.

47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

Code of Federal Regulations, 2014 CFR

2014-10-01

... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an NGSO...

47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

Code of Federal Regulations, 2012 CFR

2012-10-01

... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an NGSO...

47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

Code of Federal Regulations, 2010 CFR

2010-10-01

... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an NGSO...

47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

Code of Federal Regulations, 2011 CFR

2011-10-01

... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an NGSO...

47 CFR 25.147 - Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz.

Code of Federal Regulations, 2013 CFR

2013-10-01

... COMMISSION (CONTINUED) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Applications and Licenses Space Stations § 25.147 Licensing provision for NGSO MSS feeder downlinks in the band 6700-6875 MHz. If an NGSO...

Selecting Pixels for Kepler Downlink

NASA Technical Reports Server (NTRS)

Bryson, Stephen T.; Jenkins, Jon M.; Klaus, Todd C.; Cote, Miles T.; Quintana, Elisa V.; Hall, Jennifer R.; Ibrahim, Khadeejah; Chandrasekaran, Hema; Caldwell, Douglas A.; Van Cleve, Jeffrey E.;

Automated interferometric alignment system for paraboloidal mirrors

DOEpatents

Maxey, L. Curtis

1993-01-01

A method is described for a systematic method of interpreting interference fringes obtained by using a corner cube retroreflector as an alignment aid when aigning a paraboloid to a spherical wavefront. This is applicable to any general case where such alignment is required, but is specifically applicable in the case of aligning an autocollimating test using a diverging beam wavefront. In addition, the method provides information which can be systematically interpreted such that independent information about pitch, yaw and focus errors can be obtained. Thus, the system lends itself readily to automation. Finally, although the method is developed specifically for paraboloids, it can be seen to be applicable to a variety of other aspheric optics when applied in combination with a wavefront corrector that produces a wavefront which, when reflected from the correctly aligned aspheric surface will produce a collimated wavefront like that obtained from the paraboloid when it is correctly aligned to a spherical wavefront.

Experimental evaluation of open-loop UpLink Power Control using ACTS

NASA Technical Reports Server (NTRS)

Dissanayake, Asoka

1995-01-01

The present investigation deals with the implementation of open-loop up-link power control using a beacon signal in the down-link frequency band as the control parameter. A power control system was developed and tested using the ACTS satellite. ACTS carries beacon signals in both up- and down-link bands with which the relationship between the up- and down-link fading can be established. A power controlled carrier was transmitted to the ACTS satellite from a NASA operated ground station and the transponded signal was received at COMSAT Laboratories using a terminal that was routinely used to monitor the two ACTS beacon signals. The experiment ran for a period of approximately six months and the collected data were used to evaluate the performance of the power control system. A brief review of propagation factors involved in estimating the up-link fade using a beacon signal in the down-link band are presented. The power controller design and the experiment configuration are discussed. Results of the experiment are discussed.

Scheduling Onboard Processing for the Proposed HyspIRI Mission

NASA Technical Reports Server (NTRS)

Chien, Steve; Mclaren, David; Rabideau, Gregg; Mandl, Daniel; Hengemihle, Jerry

2011-01-01

The proposed Hyspiri mission is evaluating a X-band Direct Broadcast (DB) capability that would enable data to be delivered to ground stations virtually as it is acquired. However the HyspIRI VSWIR and TIR instruments will produce 1 Gbps data while the DB capability is 15 M bps for a 60x oversubscription. In order to address this data volume mismatch a DB concept has been developed thatdetermines which data to downlink based on both: 1. The type of surface the spacecraft is overflying and 2. Onboard processing of the data to detect events. For example when the spacecraft is overflying polar regions it might downlink a snow/ice product. Additionally the onboard software will search for thermal signatures indicative of a volcanic event or wild fire and downlink summary information (extent, spectra) when detected. The process of determining which products to generate when, based on request prioritization and onboard processing and downlink constraints is inherently a prioritized scheduling problem - we describe work to develop an automated solution to this problem.

Converting CSV Files to RKSML Files

NASA Technical Reports Server (NTRS)

Trebi-Ollennu, Ashitey; Liebersbach, Robert

2009-01-01

A computer program converts, into a format suitable for processing on Earth, files of downlinked telemetric data pertaining to the operation of the Instrument Deployment Device (IDD), which is a robot arm on either of the Mars Explorer Rovers (MERs). The raw downlinked data files are in comma-separated- value (CSV) format. The present program converts the files into Rover Kinematics State Markup Language (RKSML), which is an Extensible Markup Language (XML) format that facilitates representation of operations of the IDD and enables analysis of the operations by means of the Rover Sequencing Validation Program (RSVP), which is used to build sequences of commanded operations for the MERs. After conversion by means of the present program, the downlinked data can be processed by RSVP, enabling the MER downlink operations team to play back the actual IDD activity represented by the telemetric data against the planned IDD activity. Thus, the present program enhances the diagnosis of anomalies that manifest themselves as differences between actual and planned IDD activities.

Cost-effective bidirectional digitized radio-over-fiber systems employing sigma delta modulation

NASA Astrophysics Data System (ADS)

Lee, Kyung Woon; Jung, HyunDo; Park, Jung Ho

2016-11-01

We propose a cost effective digitized radio-over-fiber (D-RoF) system employing a sigma delta modulation (SDM) and a bidirectional transmission technique using phase modulated downlink and intensity modulated uplink. SDM is transparent to different radio access technologies and modulation formats, and more suitable for a downlink of wireless system because a digital to analog converter (DAC) can be avoided at the base station (BS). Also, Central station and BS share the same light source by using a phase modulation for the downlink and an intensity modulation for the uplink transmission. Avoiding DACs and light sources have advantages in terms of cost reduction, power consumption, and compatibility with conventional wireless network structure. We have designed a cost effective bidirectional D-RoF system using a low pass SDM and measured the downlink and uplink transmission performance in terms of error vector magnitude, signal spectra, and constellations, which are based on the 10MHz LTE 64-QAM standard.

Rice Crop Monitoring Using Microwave and Optical Remotely Sensed Image Data

NASA Astrophysics Data System (ADS)

Suga, Y.; Konishi, T.; Takeuchi, S.; Kitano, Y.; Ito, S.

Hiroshima Institute of Technology HIT is operating the direct down-links of microwave and optical satellite data in Japan This study focuses on the validation for rice crop monitoring using microwave and optical remotely sensed image data acquired by satellites referring to ground truth data such as height of crop ratio of crop vegetation cover and leaf area index in the test sites of Japan ENVISAT-1 ASAR data has a capability to capture regularly and to monitor during the rice growing cycle by alternating cross polarization mode images However ASAR data is influenced by several parameters such as landcover structure direction and alignment of rice crop fields in the test sites In this study the validation was carried out combined with microwave and optical satellite image data and ground truth data regarding rice crop fields to investigate the above parameters Multi-temporal multi-direction descending and ascending and multi-angle ASAR alternating cross polarization mode images were used to investigate rice crop growing cycle LANDSAT data were used to detect landcover structure direction and alignment of rice crop fields corresponding to the backscatter of ASAR As the result of this study it was indicated that rice crop growth can be precisely monitored using multiple remotely sensed data and ground truth data considering with spatial spectral temporal and radiometric resolutions

Robust Transceiver Design for Multiuser MIMO Downlink with Channel Uncertainties

NASA Astrophysics Data System (ADS)

Miao, Wei; Li, Yunzhou; Chen, Xiang; Zhou, Shidong; Wang, Jing

This letter addresses the problem of robust transceiver design for the multiuser multiple-input-multiple-output (MIMO) downlink where the channel state information at the base station (BS) is imperfect. A stochastic approach which minimizes the expectation of the total mean square error (MSE) of the downlink conditioned on the channel estimates under a total transmit power constraint is adopted. The iterative algorithm reported in [2] is improved to handle the proposed robust optimization problem. Simulation results show that our proposed robust scheme effectively reduces the performance loss due to channel uncertainties and outperforms existing methods, especially when the channel errors of the users are different.

Grouping Influences Output Interference in Short-term Memory: A Mixture Modeling Study.

PubMed

Kang, Min-Suk; Oh, Byung-Il

2016-01-01

Output interference is a source of forgetting induced by recalling. We investigated how grouping influences output interference in short-term memory. In Experiment 1, the participants were asked to remember four colored items. Those items were grouped by temporal coincidence as well as spatial alignment: two items were presented in the first memory array and two were presented in the second, and the items in both arrays were either vertically or horizontally aligned as well. The participants then performed two recall tasks in sequence by selecting a color presented at a cued location from a color wheel. In the same-group condition, the participants reported both items from the same memory array; however, in the different-group condition, the participants reported one item from each memory array. We analyzed participant responses with a mixture model, which yielded two measures: guess rate and precision of recalled memories. The guess rate in the second recall was higher for the different-group condition than for the same-group condition; however, the memory precisions obtained for both conditions were similarly degraded in the second recall. In Experiment 2, we varied the probability of the same- and different-group conditions with a ratio of 3 to 7. We expected output interference to be higher in the same-group condition than in the different-group condition. This is because items of the other group are more likely to be probed in the second recall phase and, thus, protecting those items during the first recall phase leads to a better performance. Nevertheless, the same pattern of results was robustly reproduced, suggesting grouping shields the grouped items from output interference because of the secured accessibility. We discussed how grouping influences output interference.

Beacon Spacecraft Operations: Lessons in Automation

NASA Technical Reports Server (NTRS)

Sherwood, R.; Schlutsmeyer, A.; Sue, M.; Szijjarto, J.; Wyatt, E. J.

2000-01-01

A new approach to mission operations has been flight validated on NASA's Deep Space One (DS1) mission that launched in October 1998. The beacon monitor operations technology is aimed at decreasing the total volume of downlinked engineering telemetry by reducing the frequency of downlink and the volume of data received per pass.

Fabrication of aligned magnetic nanoparticles using tobamoviruses.

PubMed

Kobayashi, Mime; Seki, Munetoshi; Tabata, Hitoshi; Watanabe, Yuichiro; Yamashita, Ichiro

2010-03-10

We used genetically modified tube-shaped tobamoviruses to produce 3 nm aligned magnetic nanoparticles. Amino acid residues facing the central channel of the virus were modified to increase the number of nucleation sites. Energy dispersive X-ray spectroscopy and superconducting quantum interference device analysis suggest that the particles consisted of Co-Pt alloy. The use of tobamovirus mutants is a promising approach to making a variety of components that can be applied to fabricate nanometer-scaled electronic devices.

Experimental Evaluation of Time Diversity Effect in Hybrid ARQ Considering Space and Path Diversity for Downlink OFDM-Based Broadband Radio Access

NASA Astrophysics Data System (ADS)

Miki, Nobuhiko; Atarashi, Hiroyuki; Higuchi, Kenichi; Sawahashi, Mamoru; Nakagawa, Masao

This paper presents experimental evaluations of the effect of time diversity obtained by hybrid automatic repeat request (HARQ) with soft combining in space and path diversity schemes on orthogonal frequency division multiplexing (OFDM)-based packet radio access in a downlink broadband multipath fading channel. The effect of HARQ is analyzed through laboratory experiments employing fading simulators and field experiments conducted in downtown Yokosuka near Tokyo. After confirming the validity of experimental results based on numerical analysis of the time diversity gain in HARQ, we show by the experimental results that, for a fixed modulation and channel coding scheme (MCS), time diversity obtained by HARQ is effective in reducing the required received signal-to-interference plus noise power ratio (SINR) according to an increase in the number of transmissions, K, up to 10, even when the diversity effects are obtained through two-branch antenna diversity reception and path diversity using a number of multipaths greater than 12 observed in a real fading channel. Meanwhile, in combined use with the adaptive modulation and channel coding (AMC) scheme associated with space and path diversity, we clarify that the gain obtained by time diversity is almost saturated at the maximum number of transmissions in HARQ, K' = 4 in Chase combining and K' = 2 in Incremental redundancy, since the improvement in the residual packet error rate (PER) obtained through time diversity becomes small owing to the low PER in the initial packet transmission arising from appropriately selecting the optimum MCS in AMC. However, the experimental results elucidate that the time diversity in HARQ with soft combining associated with antenna diversity reception is effective in improving the throughput even in a broadband multipath channel with sufficient path diversity.

Robust THP Transceiver Designs for Multiuser MIMO Downlink with Imperfect CSIT

NASA Astrophysics Data System (ADS)

Ubaidulla, P.; Chockalingam, A.

2009-12-01

We present robust joint nonlinear transceiver designs for multiuser multiple-input multiple-output (MIMO) downlink in the presence of imperfections in the channel state information at the transmitter (CSIT). The base station (BS) is equipped with multiple transmit antennas, and each user terminal is equipped with one or more receive antennas. The BS employs Tomlinson-Harashima precoding (THP) for interuser interference precancellation at the transmitter. We consider robust transceiver designs that jointly optimize the transmit THP filters and receive filter for two models of CSIT errors. The first model is a stochastic error (SE) model, where the CSIT error is Gaussian-distributed. This model is applicable when the CSIT error is dominated by channel estimation error. In this case, the proposed robust transceiver design seeks to minimize a stochastic function of the sum mean square error (SMSE) under a constraint on the total BS transmit power. We propose an iterative algorithm to solve this problem. The other model we consider is a norm-bounded error (NBE) model, where the CSIT error can be specified by an uncertainty set. This model is applicable when the CSIT error is dominated by quantization errors. In this case, we consider a worst-case design. For this model, we consider robust (i) minimum SMSE, (ii) MSE-constrained, and (iii) MSE-balancing transceiver designs. We propose iterative algorithms to solve these problems, wherein each iteration involves a pair of semidefinite programs (SDPs). Further, we consider an extension of the proposed algorithm to the case with per-antenna power constraints. We evaluate the robustness of the proposed algorithms to imperfections in CSIT through simulation, and show that the proposed robust designs outperform nonrobust designs as well as robust linear transceiver designs reported in the recent literature.

Wavefront division digital holography

NASA Astrophysics Data System (ADS)

Zhang, Wenhui; Cao, Liangcai; Li, Rujia; Zhang, Hua; Zhang, Hao; Jiang, Qiang; Jin, Guofan

2018-05-01

Digital holography (DH), mostly Mach-Zehnder configuration based, belongs to non-common path amplitude splitting interference imaging whose stability and fringe contrast are environmental sensitive. This paper presents a wavefront division DH configuration with both high stability and high-contrast fringes benefitting from quasi common path wavefront-splitting interference. In our proposal, two spherical waves with similar curvature coming from the same wavefront are used, which makes full use of the physical sampling capacity of the detectors. The interference fringe spacing can be adjusted flexibly for both in-line and off-axis mode due to the independent modulation to these two waves. Only a few optical elements, including the mirror-beam splitter interference component, are used without strict alignments, which makes it robust and easy-to-implement. The proposed wavefront division DH promotes interference imaging physics into the practical and miniaturized a step forward. The feasibility of this method is proved by the imaging of a resolution target and a water flea.

Soft X-ray holographic grating beam splitter including a double frequency grating for interferometer pre-alignment.

PubMed

Liu, Ying; Tan, Xin; Liu, Zhengkun; Xu, Xiangdong; Hong, Yilin; Fu, Shaojun

2008-09-15

Grating beam splitters have been fabricated for soft X-ray Mach- Zehnder interferometer using holographic interference lithography. The grating beam splitter consists of two gratings, one works at X-ray laser wavelength of 13.9 nm with the spatial frequency of 1000 lines/mm as the operation grating, the other works at visible wavelength of 632.8 nm for pre-aligning the X-ray interferometer with the spatial frequency of 22 lines/mm as the pre-alignment grating. The two gratings lie vertically on the same substrate. The main feature of the beam splitter is the use of low-spatial- frequency beat grating of a holographic double frequency grating as the pre-alignment grating of the X-ray interferometer. The grating line parallelism between the two gratings can be judged by observing the diffraction patterns of the pre-alignment grating directly.

Silicon Alignment Pins: An Easy Way to Realize a Wafer-To-Wafer Alignment

NASA Technical Reports Server (NTRS)

Peralta, Alejandro (Inventor); Gill, John J. (Inventor); Toda, Risaku (Inventor); Lin, Robert H. (Inventor); Jung-Kubiak, Cecile (Inventor); Reck, Theodore (Inventor); Thomas, Bertrand (Inventor); Siles, Jose V. (Inventor); Lee, Choonsup (Inventor); Chattopadhyay, Goutam (Inventor)

2016-01-01

A silicon alignment pin is used to align successive layers of components made in semiconductor chips and/or metallic components to make easier the assembly of devices having a layered structure. The pin is made as a compressible structure which can be squeezed to reduce its outer diameter, have one end fit into a corresponding alignment pocket or cavity defined in a layer of material to be assembled into a layered structure, and then allowed to expand to produce an interference fit with the cavity. The other end can then be inserted into a corresponding cavity defined in a surface of a second layer of material that mates with the first layer. The two layers are in registry when the pin is mated to both. Multiple layers can be assembled to create a multilayer structure. Examples of such devices are presented.

Joint minimization of uplink and downlink whole-body exposure dose in indoor wireless networks.

PubMed

Plets, D; Joseph, W; Vanhecke, K; Vermeeren, G; Wiart, J; Aerts, S; Varsier, N; Martens, L

2015-01-01

The total whole-body exposure dose in indoor wireless networks is minimized. For the first time, indoor wireless networks are designed and simulated for a minimal exposure dose, where both uplink and downlink are considered. The impact of the minimization is numerically assessed for four scenarios: two WiFi configurations with different throughputs, a Universal Mobile Telecommunications System (UMTS) configuration for phone call traffic, and a Long-Term Evolution (LTE) configuration with a high data rate. Also, the influence of the uplink usage on the total absorbed dose is characterized. Downlink dose reductions of at least 75% are observed when adding more base stations with a lower transmit power. Total dose reductions decrease with increasing uplink usage for WiFi due to the lack of uplink power control but are maintained for LTE and UMTS. Uplink doses become dominant over downlink doses for usages of only a few seconds for WiFi. For UMTS and LTE, an almost continuous uplink usage is required to have a significant effect on the total dose, thanks to the power control mechanism.

Joint Minimization of Uplink and Downlink Whole-Body Exposure Dose in Indoor Wireless Networks

PubMed Central

Plets, D.; Joseph, W.; Vanhecke, K.; Vermeeren, G.; Wiart, J.; Aerts, S.; Varsier, N.; Martens, L.

2015-01-01

The total whole-body exposure dose in indoor wireless networks is minimized. For the first time, indoor wireless networks are designed and simulated for a minimal exposure dose, where both uplink and downlink are considered. The impact of the minimization is numerically assessed for four scenarios: two WiFi configurations with different throughputs, a Universal Mobile Telecommunications System (UMTS) configuration for phone call traffic, and a Long-Term Evolution (LTE) configuration with a high data rate. Also, the influence of the uplink usage on the total absorbed dose is characterized. Downlink dose reductions of at least 75% are observed when adding more base stations with a lower transmit power. Total dose reductions decrease with increasing uplink usage for WiFi due to the lack of uplink power control but are maintained for LTE and UMTS. Uplink doses become dominant over downlink doses for usages of only a few seconds for WiFi. For UMTS and LTE, an almost continuous uplink usage is required to have a significant effect on the total dose, thanks to the power control mechanism. PMID:25793213

Controllable growth of vertically aligned graphene on C-face SiC

DOE PAGES

Liu, Yu; Chen, Lianlian; Hilliard, Donovan; ...

2016-10-06

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d 0 magnetism ismore » realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene.« less

Controllable growth of vertically aligned graphene on C-face SiC

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

Liu, Yu; Chen, Lianlian; Hilliard, Donovan

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d 0 magnetism ismore » realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene.« less

Live Ultra-High Definition from the International Space Station

NASA Technical Reports Server (NTRS)

Grubbs, Rodney; George, Sandy

2017-01-01

The first ever live downlink of Ultra-High Definition (UHD) video from the International Space Station (ISS) was the highlight of a 'Super Session' at the National Association of Broadcasters (NAB) in April 2017. The Ultra-High Definition video downlink from the ISS all the way to the Las Vegas Convention Center required considerable planning, pushed the limits of conventional video distribution from a space-craft, and was the first use of High Efficiency Video Coding (HEVC) from a space-craft. The live event at NAB will serve as a pathfinder for more routine downlinks of UHD as well as use of HEVC for conventional HD downlinks to save bandwidth. HEVC may also enable live Virtual Reality video downlinks from the ISS. This paper will describe the overall work flow and routing of the UHD video, how audio was synchronized even though the video and audio were received many seconds apart from each other, and how the demonstration paves the way for not only more efficient video distribution from the ISS, but also serves as a pathfinder for more complex video distribution from deep space. The paper will also describe how a 'live' event was staged when the UHD coming from the ISS had a latency of 10+ seconds. Finally, the paper will discuss how NASA is leveraging commercial technologies for use on-orbit vs. creating technology as was required during the Apollo Moon Program and early space age.

Highly Efficient Multi Channel Packet Forwarding with Round Robin Intermittent Periodic Transmit for Multihop Wireless Backhaul Networks

PubMed Central

Furukawa, Hiroshi

2017-01-01

Round Robin based Intermittent Periodic Transmit (RR-IPT) has been proposed which achieves highly efficient multi-hop relays in multi-hop wireless backhaul networks (MWBN) where relay nodes are 2-dimensionally deployed. This paper newly investigates multi-channel packet scheduling and forwarding scheme for RR-IPT. Downlink traffic is forwarded by RR-IPT via one of the channels, while uplink traffic and part of downlink are accommodated in the other channel. By comparing IPT and carrier sense multiple access with collision avoidance (CSMA/CA) for uplink/downlink packet forwarding channel, IPT is more effective in reducing packet loss rate whereas CSMA/CA is better in terms of system throughput and packet delay improvement. PMID:29137164

Apollo 16/AS-511/LM-11 operational calibration curves. Volume 1: Calibration curves for command service module CSM 113

NASA Technical Reports Server (NTRS)

Demoss, J. F. (Compiler)

1971-01-01

Calibration curves for the Apollo 16 command service module pulse code modulation downlink and onboard display are presented. Subjects discussed are: (1) measurement calibration curve format, (2) measurement identification, (3) multi-mode calibration data summary, (4) pulse code modulation bilevel events listing, and (5) calibration curves for instrumentation downlink and meter link.

Nanosatellite optical downlink experiment: design, simulation, and prototyping

NASA Astrophysics Data System (ADS)

Clements, Emily; Aniceto, Raichelle; Barnes, Derek; Caplan, David; Clark, James; Portillo, Iñigo del; Haughwout, Christian; Khatsenko, Maxim; Kingsbury, Ryan; Lee, Myron; Morgan, Rachel; Twichell, Jonathan; Riesing, Kathleen; Yoon, Hyosang; Ziegler, Caleb; Cahoy, Kerri

2016-11-01

The nanosatellite optical downlink experiment (NODE) implements a free-space optical communications (lasercom) capability on a CubeSat platform that can support low earth orbit (LEO) to ground downlink rates>10 Mbps. A primary goal of NODE is to leverage commercially available technologies to provide a scalable and cost-effective alternative to radio-frequency-based communications. The NODE transmitter uses a 200-mW 1550-nm master-oscillator power-amplifier design using power-efficient M-ary pulse position modulation. To facilitate pointing the 0.12-deg downlink beam, NODE augments spacecraft body pointing with a microelectromechanical fast steering mirror (FSM) and uses an 850-nm uplink beacon to an onboard CCD camera. The 30-cm aperture ground telescope uses an infrared camera and FSM for tracking to an avalanche photodiode detector-based receiver. Here, we describe our approach to transition prototype transmitter and receiver designs to a full end-to-end CubeSat-scale system. This includes link budget refinement, drive electronics miniaturization, packaging reduction, improvements to pointing and attitude estimation, implementation of modulation, coding, and interleaving, and ground station receiver design. We capture trades and technology development needs and outline plans for integrated system ground testing.

Onboard Algorithms for Data Prioritization and Summarization of Aerial Imagery

NASA Technical Reports Server (NTRS)

Chien, Steve A.; Hayden, David; Thompson, David R.; Castano, Rebecca

2013-01-01

Many current and future NASA missions are capable of collecting enormous amounts of data, of which only a small portion can be transmitted to Earth. Communications are limited due to distance, visibility constraints, and competing mission downlinks. Long missions and high-resolution, multispectral imaging devices easily produce data exceeding the available bandwidth. To address this situation computationally efficient algorithms were developed for analyzing science imagery onboard the spacecraft. These algorithms autonomously cluster the data into classes of similar imagery, enabling selective downlink of representatives of each class, and a map classifying the terrain imaged rather than the full dataset, reducing the volume of the downlinked data. A range of approaches was examined, including k-means clustering using image features based on color, texture, temporal, and spatial arrangement

Remote control of an impact demonstration vehicle

NASA Technical Reports Server (NTRS)

Harney, P. F.; Craft, J. B., Jr.; Johnson, R. G.

1985-01-01

Uplink and downlink telemetry systems were installed in a Boeing 720 aircraft that was remotely flown from Rogers Dry Lake at Edwards Air Force Base and impacted into a designated crash site on the lake bed. The controlled impact demonstration (CID) program was a joint venture by the National Aeronautics and Space Administration (NASA) and the Federal Aviation Administration (FAA) to test passenger survivability using antimisting kerosene (AMK) to inhibit postcrash fires, improve passenger seats and restraints, and improve fire-retardent materials. The uplink telemetry system was used to remotely control the aircraft and activate onboard systems from takeoff until after impact. Aircraft systems for remote control, aircraft structural response, passenger seat and restraint systems, and anthropomorphic dummy responses were recorded and displayed by the downlink stems. The instrumentation uplink and downlink systems are described.

A Study of an Optical Lunar Surface Communications Network with High Bandwidth Direct to Earth Link

NASA Technical Reports Server (NTRS)

Wilson, K.; Biswas, A.; Schoolcraft, J.

2011-01-01

Analyzed optical DTE (direct to earth) and lunar relay satellite link analyses, greater than 200 Mbps downlink to 1-m Earth receiver and greater than 1 Mbps uplink achieved with mobile 5-cm lunar transceiver, greater than 1Gbps downlink and greater than 10 Mpbs uplink achieved with 10-cm stationary lunar transceiver, MITLL (MIT Lincoln Laboratory) 2013 LLCD (Lunar Laser Communications Demonstration) plans to demonstrate 622 Mbps downlink with 20 Mbps uplink between lunar orbiter and ground station; Identified top five technology challenges to deploying lunar optical network, Performed preliminary experiments on two of challenges: (i) lunar dust removal and (ii)DTN over optical carrier, Exploring opportunities to evaluate DTN (delay-tolerant networking) over optical link in a multi-node network e.g. Desert RATS.

Antennas Designed for Advanced Communications for Air Traffic Management (AC/ATM) Project

NASA Technical Reports Server (NTRS)

Zakrajsek, Robert J.

2000-01-01

The goal of the Advanced Communications for Air Traffic Management (AC/ATM) Project at the NASA Glenn Research Center at Lewis Field is to enable a communications infrastructure that provides the capacity, efficiency, and flexibility necessary to realize a mature free-flight environment. The technical thrust of the AC/ATM Project is targeted at the design, development, integration, test, and demonstration of enabling technologies for global broadband aeronautical communications. Since Ku-band facilities and equipment are readily available, one of the near-term demonstrations involves a link through a Kuband communications satellite. Two conformally mounted antennas will support the initial AC/ATM communications links. Both of these are steered electronically through monolithic microwave integrated circuit (MMIC) amplifiers and phase shifters. This link will be asymmetrical with the downlink to the aircraft (mobile vehicle) at a throughput rate of greater than 1.5 megabits per second (Mbps), whereas the throughput rate of the uplink from the aircraft will be greater than 100 kilobits per second (kbps). The data on the downlink can be narrow-band, wide-band, or a combination of both, depending on the requirements of the experiment. The AC/ATM project is purchasing a phased-array Ku-band transmitting antenna for the uplink from the test vehicle. Many Ku-band receiving antennas have been built, and one will be borrowed for a short time to perform the initial experiments at the NASA Glenn Research Center at Lewis Field. The Ku-band transmitting antenna is a 254-element MMIC phased-array antenna being built by Boeing Phantom Works. Each element can radiate 100 mW. The antenna is approximately 43-cm high by 24-cm wide by 3.3-cm thick. It can be steered beyond 60 from broadside. The beamwidth varies from 6 at broadside to 12 degrees at 60 degrees, which is typical of phased-array antennas. When the antenna is steered to 60 degrees, the beamwidth will illuminate approximately five satellites on the orbital arc. Spread spectrum techniques will be employed to keep the power impinging on the adjacent satellites below their noise floor so that no interference results. This antenna is power limited. If the antenna elements (currently 254) are increased by a factor of 4 (1024) or 16 (4096), the gain will increase and the beamwidth will decrease in proportion. For the latter two antenna sizes, the power must be "backed off" to prevent interference with the neighboring satellites. The receiving antenna, which is approximately 90-cm high, 60-cm wide, and 3.5-cm thick, is composed of 1500 phased-array elements. The system phased-array controller can control both a 1500-element receiving antenna and a 500-element transmitting antenna. For ground testing, this controller will allow manual beam pointing and polarization alignment. For normal operation, the system can be connected to the receiving antenna and the navigation system for real-time autonomous track operation. This will be accomplished by first pointing both antennas at the satellite using information from the aircraft data bus. Then, the system phased-array controller will electronically adjust the antenna pointing of the receiving antenna to find the peak signal. After the peak signal has been found, the beam of the transmitting antenna will be pointed to the same steering angles as the receiving antenna. For initial ground testing without an aircraft, the ARINC 429 data bus (ARINC Inc., Annapolis, Maryland) will be simulated by a gyro system purchased for the follow-on to the Monolithic Microwave Integrated Circuit (MMIC) Arrays for Satellite Communication on the Move (MASCOM) Project. MASCOM utilized the Advanced Communications Technology Satellite (ACTS) with a pair of Ka-band experimental phased-array antennas.

Far-field interference of a neutron white beam and the applications to noninvasive phase-contrast imaging

NASA Astrophysics Data System (ADS)

Pushin, D. A.; Sarenac, D.; Hussey, D. S.; Miao, H.; Arif, M.; Cory, D. G.; Huber, M. G.; Jacobson, D. L.; LaManna, J. M.; Parker, J. D.; Shinohara, T.; Ueno, W.; Wen, H.

2017-04-01

The phenomenon of interference plays a crucial role in the field of precision measurement science. Wave-particle duality has expanded the well-known interference effects of electromagnetic waves to massive particles. The majority of the wave-particle interference experiments require a near monochromatic beam which limits its applications due to the resulting low intensity. Here we demonstrate white beam interference in the far-field regime using a two-phase-grating neutron interferometer and its application to phase-contrast imaging. The functionality of this interferometer is based on the universal moiré effect that allows us to improve upon the standard Lau setup. Interference fringes were observed with monochromatic and polychromatic neutron beams for both continuous and pulsed beams. Far-field neutron interferometry allows for the full utilization of intense neutron sources for precision measurements of gradient fields. It also overcomes the alignment, stability, and fabrication challenges associated with the more familiar perfect-crystal neutron interferometer, as well as avoids the loss of intensity due to the absorption analyzer grating requirement in Talbot-Lau interferometer.

Neural mechanisms of interference control in working memory capacity.

PubMed

Bomyea, Jessica; Taylor, Charles T; Spadoni, Andrea D; Simmons, Alan N

2018-02-01

The extent to which one can use cognitive resources to keep information in working memory is known to rely on (1) active maintenance of target representations and (2) downregulation of interference from irrelevant representations. Neurobiologically, the global capacity of working memory is thought to depend on the prefrontal and parietal cortices; however, the neural mechanisms involved in controlling interference specifically in working memory capacity tasks remain understudied. In this study, 22 healthy participants completed a modified complex working memory capacity task (Reading Span) with trials of varying levels of interference control demands while undergoing functional MRI. Neural activity associated with interference control demands was examined separately during encoding and recall phases of the task. Results suggested a widespread network of regions in the prefrontal, parietal, and occipital cortices, and the cingulate and cerebellum associated with encoding, and parietal and occipital regions associated with recall. Results align with prior findings emphasizing the importance of frontoparietal circuits for working memory performance, including the role of the inferior frontal gyrus, cingulate, occipital cortex, and cerebellum in regulation of interference demands. © 2017 Wiley Periodicals, Inc.

Adaptive array antenna for satellite cellular and direct broadcast communications

NASA Technical Reports Server (NTRS)

Horton, Charles R.; Abend, Kenneth

1993-01-01

Adaptive phased-array antennas provide cost-effective implementation of large, light weight apertures with high directivity and precise beamshape control. Adaptive self-calibration allows for relaxation of all mechanical tolerances across the aperture and electrical component tolerances, providing high performance with a low-cost, lightweight array, even in the presence of large physical distortions. Beam-shape is programmable and adaptable to changes in technical and operational requirements. Adaptive digital beam-forming eliminates uplink contention by allowing a single electronically steerable antenna to service a large number of receivers with beams which adaptively focus on one source while eliminating interference from others. A large, adaptively calibrated and fully programmable aperture can also provide precise beam shape control for power-efficient direct broadcast from space. Advanced adaptive digital beamforming technologies are described for: (1) electronic compensation of aperture distortion, (2) multiple receiver adaptive space-time processing, and (3) downlink beam-shape control. Cost considerations for space-based array applications are also discussed.

Attitude ground support system for the solar maximum mission spacecraft

NASA Technical Reports Server (NTRS)

Nair, G.

1980-01-01

The SMM attitude ground support system (AGSS) supports the acquisition of spacecraft roll attitude reference, performs the in-flight calibration of the attitude sensor complement, supports onboard control autonomy via onboard computer data base updates, and monitors onboard computer (OBC) performance. Initial roll attitude acquisition is accomplished by obtaining a coarse 3 axis attitude estimate from magnetometer and Sun sensor data and subsequently refining it by processing data from the fixed head star trackers. In-flight calibration of the attitude sensor complement is achieved by processing data from a series of slew maneuvers designed to maximize the observability and accuracy of the appropriate alignments and biases. To ensure autonomy of spacecraft operation, the AGSS selects guide stars and computes sensor occultation information for uplink to the OBC. The onboard attitude control performance is monitored on the ground through periodic attitude determination and processing of OBC data in downlink telemetry. In general, the control performance has met mission requirements. However, software and hardware problems have resulted in sporadic attitude reference losses.

Other Types Of LCDs

NASA Astrophysics Data System (ADS)

Kobayashi, Shunsuke; Mochizuki, Akihiro

The following sections are included: * INTRODUCTION * TUNABLE BIREFRINGENCE LCDs * Nematic Device with Homogeneous Alignment * Nematic Device with Homeotropic Alignment * ELECTRICALLY CONTROLLED BIREFRINGENCE EFFECT LCDs WITH A COMPENSATING CELL OR POLYMER LAYERS * Super Homeotropic LCDs * Black and White STN LCDs * Optical mode interference * Guest-host mode * Double-layered STN * Retardation film compensated STN * DUAL FREQUENCY ADDRESSING LCDs * Application for DSM LCDs * Application for TN LCDs * PI-CELL * CHOLESTERIC-NEMATIC PHASE CHANGE LCDs * Storage Mode LCDs * Stabilized Hysteresis Mode LCDs * THERMALLY ADDRESSED LCDs (CHOLESTERIC) * BISTABLE LCD * WIDE VIEWING ANGLE TN LCDs USING RETARDATION SHEETS * Type 1 Cells * Type 2 Cells * REFERENCES

Wavefront error sensing for LDR

NASA Technical Reports Server (NTRS)

Tubbs, Eldred F.; Glavich, T. A.

1988-01-01

Wavefront sensing is a significant aspect of the LDR control problem and requires attention at an early stage of the control system definition and design. A combination of a Hartmann test for wavefront slope measurement and an interference test for piston errors of the segments was examined and is presented as a point of departure for further discussion. The assumption is made that the wavefront sensor will be used for initial alignment and periodic alignment checks but that it will not be used during scientific observations. The Hartmann test and the interferometric test are briefly examined.

Astronaut Andrew M. Allen, mission commander, sets up systems for a television downlink on the

NASA Technical Reports Server (NTRS)

1996-01-01

STS-75 ONBOARD VIEW --- Astronaut Andrew M. Allen, mission commander, sets up systems for a television downlink on the flight deck of the Space Shuttle Columbia. Allen was joined by four other astronauts and an international payload specialist for more than 16 days of research aboard Columbia. The photograph was taken with a 70mm handheld camera.

Does Temporal Integration of Face Parts Reflect Holistic Processing?

PubMed Central

Cheung, Olivia S.; Richler, Jennifer J.; Phillips, W. Stewart; Gauthier, Isabel

2011-01-01

We examined whether temporal integration of face parts reflects holistic processing or response interference. Participants learned to name two faces “Fred” and two “Bob”. At test, top and bottom halves of different faces formed composites and were presented briefly separated in time. Replicating prior findings (Singer & Sheinberg, 2006), naming of the target halves for aligned composites was slowed when the irrelevant halves were from faces with a different name compared to that from the original face. However, no interference was observed when the irrelevant halves had identical names as the target halves but came from different learned faces, arguing against a true holistic effect. Instead, response interference was obtained when the target halves briefly preceded the irrelevant halves. Experiment 2 confirmed a double-dissociation between holistic processing vs. response interference for intact faces vs. temporally separated face halves, suggesting that simultaneous presentation of facial information is critical for holistic processing. PMID:21327378

Large-scale fabrication of vertically aligned ZnO nanowire arrays

DOEpatents

Wang, Zhong L; Das, Suman; Xu, Sheng; Yuan, Dajun; Guo, Rui; Wei, Yaguang; Wu, Wenzhuo

2013-02-05

In a method for growing a nanowire array, a photoresist layer is placed onto a nanowire growth layer configured for growing nanowires therefrom. The photoresist layer is exposed to a coherent light interference pattern that includes periodically alternately spaced dark bands and light bands along a first orientation. The photoresist layer exposed to the coherent light interference pattern along a second orientation, transverse to the first orientation. The photoresist layer developed so as to remove photoresist from areas corresponding to areas of intersection of the dark bands of the interference pattern along the first orientation and the dark bands of the interference pattern along the second orientation, thereby leaving an ordered array of holes passing through the photoresist layer. The photoresist layer and the nanowire growth layer are placed into a nanowire growth environment, thereby growing nanowires from the nanowire growth layer through the array of holes.

Performance Analysis of Power Saving Class of Type 1 with Both Downlink and Uplink Traffics in IEEE 802.16e

NASA Astrophysics Data System (ADS)

Baek, Sangkyu; Choi, Bong Dae

We investigate power consumption of a mobile station with the power saving class of type 1 in the IEEE 802.16e. We deal with stochastic behavior of mobile station during not only sleep mode period but also awake mode period with both downlink and uplink traffics. Our methods for investigating the power saving class of type 1 are to construct the embedded Markov chain and the semi-Markov chain generated by the embedded Markov chain. To see the effect of the sleep mode, we obtain the average power consumption of a mobile station and the mean queueing delay of a message. Numerical results show that the larger size of the sleep window makes the power consumption of a mobile station smaller and the queueing delay of a downlink message longer.

A Direct Broadcast Operations Concept for the HyspIRI Mission

NASA Technical Reports Server (NTRS)

Chien, Steve A.; Silverman, Dorothy; Rabideau, Gregg; Mandl, Daniel; Hengemihle, Jerry

2010-01-01

HyspIRI is evaluating a X-band Direct Broadcast (DB) capability that would enable data to be delivered to ground stations virtually as it is acquired. However the HyspIRI VSWIR and TIR instruments will produce 1 Gbps data while the DB capability is 15 M bps for an approximate 60x oversubscription. In order to address this data volume mismatch a DB concept has been developed that determines which data to downlink based on both: 1. the type of surface the spacecraft is overflying and 2. onboard processing of the data to detect events. For example when the spacecraft is overflying polar regions it might downlink a snow/ice product. Additionally the onboard software will search for thermal signatures indicative of a volcanic event or wild fire and downlink summary information (extent, spectra) when detected, thereby reducing data volume.

Guidance system operations plan for manned CM earth orbital missions using program Skylark 1. Section 2: Data links

NASA Technical Reports Server (NTRS)

Hamilton, M. H.

1972-01-01

A computer program to define the digital uplink and downlink for use in manned command module orbital missions is presented. The subjects discussed are: (1) digital uplink to command module, (2) CMC digital downlink, (3) downlist formats, (4) description of telemetered qualities, (5) flagbits, and (6) effects of Fresh Start (V36) and Hardware Restart on flagword and channel bits.

Students Speak with the ISS

NASA Image and Video Library

2012-11-15

Students from D.C.'s Stuart-Hobson Middle School participate in a live video downlink with astronauts aboard the International Space Station at the Smithsonian National Air and Space Museum, Thursday, Nov. 15, 2012 in Washington. The downlink is an annual event held in honor of International Education Week, and was co-hosted with the Department of Education and the National Center for Earth and Space Science Education (NCESSE). Photo Credit: (NASA/Carla Cioffi)

A full-duplex optical access system with hybrid 64/16/4QAM-OFDM downlink

NASA Astrophysics Data System (ADS)

He, Chao; Tan, Ze-fu; Shao, Yu-feng; Cai, Li; Pu, He-sheng; Zhu, Yun-le; Huang, Si-si; Liu, Yu

2016-09-01

A full-duplex optical passive access scheme is proposed and verified by simulation, in which hybrid 64/16/4-quadrature amplitude modulation (64/16/4QAM) orthogonal frequency division multiplexing (OFDM) optical signal is for downstream transmission and non-return-to-zero (NRZ) optical signal is for upstream transmission. In view of the transmitting and receiving process for downlink optical signal, in-phase/quadrature-phase (I/Q) modulation based on Mach-Zehnder modulator (MZM) and homodyne coherent detection technology are employed, respectively. The simulation results show that the bit error ratio ( BER) less than hardware decision forward error correction (HD-FEC) threshold is successfully obtained over transmission path with 20-km-long standard single mode fiber (SSMF) for hybrid downlink modulation OFDM optical signal. In addition, by dividing the system bandwidth into several subchannels consisting of some continuous subcarriers, it is convenient for users to select different channels depending on requirements of communication.

Double-Glazing Interferometry

ERIC Educational Resources Information Center

Toal, Vincent; Mihaylova, Emilia M.

2009-01-01

This note describes how white light interference fringes can be seen by observing the Moon through a double-glazed window. White light interferometric fringes are normally observed only in a well-aligned interferometer whose optical path difference is less than the coherence length of the light source, which is approximately one micrometer for…

Multimode interference tapered fiber refractive index sensors.

PubMed

Biazoli, Claudecir R; Silva, Susana; Franco, Marcos A R; Frazão, Orlando; Cordeiro, Cristiano M B

2012-08-20

Real-time monitoring of the fabrication process of tapering down a multimode-interference-based fiber structure is presented. The device is composed of a pure silica multimode fiber (MMF) with an initial 125 μm diameter spliced between two single-mode fibers. The process allows a thin MMF with adjustable parameters to obtain a high signal transmittance, arising from constructive interference among the guided modes at the output end of the MMF. Tapered structures with waist diameters as low as 55 μm were easily fabricated without the limitation of fragile splices or difficulty in controlling lateral fiber alignments. The sensing device is shown to be sensitive to the external environment, and a maximum sensitivity of 2946 nm/refractive index unit in the refractive index range of 1.42-1.43 was attained.

Three-dimensionally modulated anisotropic structure for diffractive optical elements created by one-step three-beam polarization holographic photoalignment

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

Kawai, Kotaro, E-mail: s135016@stn.nagaokaut.ac.jp; Sakamoto, Moritsugu; Noda, Kohei

2016-03-28

A diffractive optical element with a three-dimensional liquid crystal (LC) alignment structure for advanced control of polarized beams was fabricated by a highly efficient one-step photoalignment method. This study is of great significance because different two-dimensional continuous and complex alignment patterns can be produced on two alignment films by simultaneously irradiating an empty glass cell composed of two unaligned photocrosslinkable polymer LC films with three-beam polarized interference beam. The polarization azimuth, ellipticity, and rotation direction of the diffracted beams from the resultant LC grating widely varied depending on the two-dimensional diffracted position and the polarization states of the incident beams.more » These polarization diffraction properties are well explained by theoretical analysis based on Jones calculus.« less

Formation of nanotunnels inside a resist film in laser interference lithography.

PubMed

Wei, Qi; Hu, Fanhua; Wang, Liyuan

2015-05-19

A few kinds of 2-diazo-1-naphthoquinone-4-sulfonates of poly(4-hydroxylstyrene) were prepared to form one-component i-line photoresists. In the laser interference lithography experiments of some of the photoresists, nanotunnels were observed to be aligned in the interior of the resist film. The shape and size of the nanotunnels remain virtually unchanged even under an increased exposure dose, indicating that the exposure energy is confined within the tunnel space. The formation of the nanotunnels results from the effect of standing waves and the permeation of developer from the surface deep into the resist films.

Interference Alignment With Partial CSI Feedback in MIMO Cellular Networks

NASA Astrophysics Data System (ADS)

Rao, Xiongbin; Lau, Vincent K. N.

2014-04-01

Interference alignment (IA) is a linear precoding strategy that can achieve optimal capacity scaling at high SNR in interference networks. However, most existing IA designs require full channel state information (CSI) at the transmitters, which would lead to significant CSI signaling overhead. There are two techniques, namely CSI quantization and CSI feedback filtering, to reduce the CSI feedback overhead. In this paper, we consider IA processing with CSI feedback filtering in MIMO cellular networks. We introduce a novel metric, namely the feedback dimension, to quantify the first order CSI feedback cost associated with the CSI feedback filtering. The CSI feedback filtering poses several important challenges in IA processing. First, there is a hidden partial CSI knowledge constraint in IA precoder design which cannot be handled using conventional IA design methodology. Furthermore, existing results on the feasibility conditions of IA cannot be applied due to the partial CSI knowledge. Finally, it is very challenging to find out how much CSI feedback is actually needed to support IA processing. We shall address the above challenges and propose a new IA feasibility condition under partial CSIT knowledge in MIMO cellular networks. Based on this, we consider the CSI feedback profile design subject to the degrees of freedom requirements, and we derive closed-form trade-off results between the CSI feedback cost and IA performance in MIMO cellular networks.

A Search for Technosignatures from 14 Planetary Systems in the Kepler Field with the Green Bank Telescope at 1.15–1.73 GHz

NASA Astrophysics Data System (ADS)

Margot, Jean-Luc; Greenberg, Adam H.; Pinchuk, Pavlo; Shinde, Akshay; Alladi, Yashaswi; Prasad MN, Srinivas; Bowman, M. Oliver; Fisher, Callum; Gyalay, Szilard; McKibbin, Willow; Miles, Brittany; Nguyen, Donald; Power, Conor; Ramani, Namrata; Raviprasad, Rashmi; Santana, Jesse; Lynch, Ryan S.

2018-05-01

Analysis of Kepler mission data suggests that the Milky Way includes billions of Earth-sized planets in the habitable zone of their host stars. Current technology enables the detection of technosignatures emitted from a large fraction of the Galaxy. We describe a search for technosignatures that is sensitive to Arecibo-class transmitters located within ∼420 ly of Earth and transmitters that are 1000 times more effective than Arecibo within ∼13000 ly of Earth. Our observations focused on 14 planetary systems in the Kepler field and used the L-band receiver (1.15–1.73 GHz) of the 100 m diameter Green Bank Telescope. Each source was observed for a total integration time of 5 minutes. We obtained power spectra at a frequency resolution of 3 Hz and examined narrowband signals with Doppler drift rates between ±9 Hz s‑1. We flagged any detection with a signal-to-noise ratio in excess of 10 as a candidate signal and identified approximately 850,000 candidates. Most (99%) of these candidate signals were automatically classified as human-generated radio-frequency interference (RFI). A large fraction (>99%) of the remaining candidate signals were also flagged as anthropogenic RFI because they have frequencies that overlap those used by global navigation satellite systems, satellite downlinks, or other interferers detected in heavily polluted regions of the spectrum. All 19 remaining candidate signals were scrutinized and none were attributable to an extraterrestrial source.

An NFC on Two-Coil WPT Link for Implantable Biomedical Sensors under Ultra-Weak Coupling.

PubMed

Gong, Chen; Liu, Dake; Miao, Zhidong; Wang, Wei; Li, Min

2017-06-11

The inductive link is widely used in implantable biomedical sensor systems to achieve near-field communication (NFC) and wireless power transfer (WPT). However, it is tough to achieve reliable NFC on an inductive WPT link when the coupling coefficient is ultra-low (0.01 typically), since the NFC signal (especially for the uplink from the in-body part to the out-body part) could be too weak to be detected. Traditional load shift keying (LSK) requires strong coupling to pass the load modulation information to the power source. Instead of using LSK, we propose a dual-carrier NFC scheme for the weak-coupled inductive link; using binary phase shift keying (BPSK) modulation, its downlink data are modulated on the power carrier (2 MHz), while its uplink data are modulated on another carrier (125 kHz). The two carriers are transferred through the same coil pair. To overcome the strong interference of the power carrier, dedicated circuits are introduced. In addition, to minimize the power transfer efficiency decrease caused by adding NFC, we optimize the inductive link circuit parameters and approach the receiver sensitivity limit. In the prototype experiments, even though the coupling coefficient is as low as 0.008, the in-body transmitter costs only 0.61 mW power carrying 10 kbps of data, and achieves a 1 × 10 - 7 bit error rate under the strong interference of WPT. This dual-carrier NFC scheme could be useful for small-sized implantable biomedical sensor applications.

Performance evaluation of hybrid VLC using device cost and power over data throughput criteria

NASA Astrophysics Data System (ADS)

Lee, C. C.; Tan, C. S.; Wong, H. Y.; Yahya, M. B.

2013-09-01

Visible light communication (VLC) technology has attained its attention in both academic and industry lately. It is determined by the development of light emitting diode (LED) technology for solid-state lighting (SSL).It has great potential to gradually replace radio frequency (RF) wireless technology because it offers unregulated and unlicensed bandwidth to withstand future demand of indoor wireless access to real-time bandwidth-demanding applications. However, it was found to provide intrusive uplink channel that give rise to unpleasant irradiance from the user device which could interfere with the downlink channel of VLC and hence limit mobility to users as a result of small coverage (field of view of VLC).To address this potential problem, a Hybrid VLC system which integrates VLC (for downlink) and RF (for uplink) technology is proposed. It offers a non-intrusive RF back channel that provides high throughput VLC and maintains durability with conventional RF devices. To deploy Hybrid VLC system in the market, it must be energy and cost saving to attain its equivalent economical advantage by comparing to existing architecture that employs fluorescent or LED lights with RF technology. In this paper, performance evaluation on the proposed hybrid system was carried out in terms of device cost and power consumption against data throughput. Based on our simulation, Hybrid VLC system was found to reduce device cost by 3% and power consumption by 68% when compares to fluorescent lights with RF technology. Nevertheless, when it is compared to LED lights with RF technology, our proposed hybrid system is found to achieve device cost saving as high as 47% and reduced power consumption by 49%. Such promising results have demonstrated that Hybrid VLC system is a feasible solution and has paved the way for greater cost saving and energy efficient compares with the current RF architecture even with the increasing requirement of indoor area coverage.

The Mars Color Imager (MARCI) on the Mars Climate Orbiter

NASA Astrophysics Data System (ADS)

Malin, M. C.; Calvin, W.; Clancy, R. T.; Haberle, R. M.; James, P. B.; Lee, S. W.; Thomas, P. C.; Caplinger, M. A.

2001-08-01

The Mars Color Imager, or MARCI, experiment on the Mars Climate Orbiter (MCO) consists of two cameras with unique optics and identical focal plane assemblies (FPAs), Data Acquisition System (DAS) electronics, and power supplies. Each camera is characterized by small physical size and mass (~6 × 6 × 12 cm, including baffle; <500 g), low power requirements (<2.5 W, including power supply losses), and high science performance (1000 × 1000 pixel, low noise). The Wide Angle (WA) camera will have the capability to map Mars in five visible and two ultraviolet spectral bands at a resolution of better than 8 km/pixel under the worst case downlink data rate. Under better downlink conditions the WA will provide kilometer-scale global maps of atmospheric phenomena such as clouds, hazes, dust storms, and the polar hood. Limb observations will provide additional detail on atmospheric structure at 13 scale-height resolution. The Medium Angle (MA) camera is designed to study selected areas of Mars at regional scale. From 400 km altitude its 6° FOV, which covers ~40 km at 40 m/pixel, will permit all locations on the planet except the poles to be accessible for image acquisitions every two mapping cycles (roughly 52 sols). Eight spectral channels between 425 and 1000 nm provide the ability to discriminate both atmospheric and surface features on the basis of composition. The primary science objectives of MARCI are to (1) observe Martian atmospheric processes at synoptic scales and mesoscales, (2) study details of the interaction of the atmosphere with the surface at a variety of scales in both space and time, and (3) examine surface features characteristic of the evolution of the Martian climate over time. MARCI will directly address two of the three high-level goals of the Mars Surveyor Program: Climate and Resources. Life, the third goal, will be addressed indirectly through the environmental factors associated with the other two goals.

A novel design measuring method based on linearly polarized laser interference

NASA Astrophysics Data System (ADS)

Cao, Yanbo; Ai, Hua; Zhao, Nan

2013-09-01

The interferometric method is widely used in the precision measurement, including the surface quality of the large-aperture mirror. The laser interference technology has been developing rapidly as the laser sources become more and more mature and reliable. We adopted the laser diode as the source for the sake of the short coherent wavelength of it for the optical path difference of the system is quite shorter as several wavelengths, and the power of laser diode is sufficient for measurement and safe to human eye. The 673nm linearly laser was selected and we construct a novel form of interferometric system as we called `Closed Loop', comprised of polarizing optical components, such as polarizing prism and quartz wave plate, the light from the source split by which into measuring beam and referencing beam, they've both reflected by the measuring mirror, after the two beams transforming into circular polarization and spinning in the opposite directions we induced the polarized light synchronous phase shift interference technology to get the detecting fringes, which transfers the phase shifting in time domain to space, so that we did not need to consider the precise-controlled shift of optical path difference, which will introduce the disturbance of the air current and vibration. We got the interference fringes from four different CCD cameras well-alignment, and the fringes are shifted into four different phases of 0, π/2, π, and 3π/2 in time. After obtaining the images from the CCD cameras, we need to align the interference fringes pixel to pixel from different CCD cameras, and synthesis the rough morphology, after getting rid of systematic error, we could calculate the surface accuracy of the measuring mirror. This novel design detecting method could be applied into measuring the optical system aberration, and it would develop into the setup of the portable structural interferometer and widely used in different measuring circumstances.

Multivariate curve resolution based chromatographic peak alignment combined with parallel factor analysis to exploit second-order advantage in complex chromatographic measurements.

PubMed

Parastar, Hadi; Akvan, Nadia

2014-03-13

In the present contribution, a new combination of multivariate curve resolution-correlation optimized warping (MCR-COW) with trilinear parallel factor analysis (PARAFAC) is developed to exploit second-order advantage in complex chromatographic measurements. In MCR-COW, the complexity of the chromatographic data is reduced by arranging the data in a column-wise augmented matrix, analyzing using MCR bilinear model and aligning the resolved elution profiles using COW in a component-wise manner. The aligned chromatographic data is then decomposed using trilinear model of PARAFAC in order to exploit pure chromatographic and spectroscopic information. The performance of this strategy is evaluated using simulated and real high-performance liquid chromatography-diode array detection (HPLC-DAD) datasets. The obtained results showed that the MCR-COW can efficiently correct elution time shifts of target compounds that are completely overlapped by coeluted interferences in complex chromatographic data. In addition, the PARAFAC analysis of aligned chromatographic data has the advantage of unique decomposition of overlapped chromatographic peaks to identify and quantify the target compounds in the presence of interferences. Finally, to confirm the reliability of the proposed strategy, the performance of the MCR-COW-PARAFAC is compared with the frequently used methods of PARAFAC, COW-PARAFAC, multivariate curve resolution-alternating least squares (MCR-ALS), and MCR-COW-MCR. In general, in most of the cases the MCR-COW-PARAFAC showed an improvement in terms of lack of fit (LOF), relative error (RE) and spectral correlation coefficients in comparison to the PARAFAC, COW-PARAFAC, MCR-ALS and MCR-COW-MCR results. Copyright © 2014 Elsevier B.V. All rights reserved.

10 Gbps Shuttle-to-Ground Adjunct Communication Link Capability Experiment

NASA Technical Reports Server (NTRS)

Ceniceros, J. M.; Sandusky, J. V.; Hemmati, H.

1999-01-01

A 1.2 Gbps space-to-ground laser communication experiment being developed for use on an EXpedite the PRocessing of Experiments to the Space Station (EXPRESS) Pallet Adapter can be adapted to fit the Hitchhiker cross-bay-carrier pallet and upgraded to data rates exceeding 1O Gbps. So modified, this instrument would enable both real-time data delivery and increased data volume for payloads using the Space Shuttle. Applications such as synthetic aperture radar and multispectral imaging collect large data volumes at a high rate and would benefit from the capability for real-time data delivery and from increased data downlink volume. Current shuttle downlink capability is limited to 50 Mbps, forcing such instruments to store large amounts of data for later analysis. While the technology is not yet sufficiently proven to be relied on as the primary communication link, when in view of the ground station it would increase the shuttle downlink rate capability 200 times, with typical total daily downlinks of 200 GB - as much data as the shuttle could downlink if it were able to maintain its maximum data rate continuously for one day. The lasercomm experiment, the Optical Communication Demonstration and High-Rate Link Facility (OCDHRLF), is being developed by the Jet Propulsion Laboratory's (JPL) Optical Communication Group through support from the International Space Station Engineering Research and Technology Development program. It is designed to work in conjunction with the Optical Communication Telescope Laboratory (OCTL) NASA's first optical communication ground station, which is under construction at JPL's Table Mountain Facility near Wrightwood, California. This paper discusses the modifications to the preliminary design of the flight system that would be necessary to adapt it to fit the Hitchhiker Cross-Bay Carrier. It also discusses orbit geometries which are favorable to the OCTL and potential non-NASA ground stations, anticipated burst-error-rates and bit-error-rates, and requirements for data collection on the ground.

Exposure assessment of one-year-old child to 3G tablet in uplink mode and to 3G femtocell in downlink mode using polynomial chaos decomposition

NASA Astrophysics Data System (ADS)

Liorni, I.; Parazzini, M.; Varsier, N.; Hadjem, A.; Ravazzani, P.; Wiart, J.

2016-04-01

So far, the assessment of the exposure of children, in the ages 0-2 years old, to relatively new radio-frequency (RF) technologies, such as tablets and femtocells, remains an open issue. This study aims to analyse the exposure of a one year-old child to these two sources, tablets and femtocells, operating in uplink (tablet) and downlink (femtocell) modes, respectively. In detail, a realistic model of an infant has been used to model separately the exposures due to (i) a 3G tablet emitting at the frequency of 1940 MHz (uplink mode) placed close to the body and (ii) a 3G femtocell emitting at 2100 MHz (downlink mode) placed at a distance of at least 1 m from the infant body. For both RF sources, the input power was set to 250 mW. The variability of the exposure due to the variation of the position of the RF sources with respect to the infant body has been studied by stochastic dosimetry, based on polynomial chaos to build surrogate models of both whole-body and tissue specific absorption rate (SAR), which makes it easy and quick to investigate the exposure in a full range of possible positions of the sources. The major outcomes of the study are: (1) the maximum values of the whole-body SAR (WB SAR) have been found to be 9.5 mW kg-1 in uplink mode and 65 μW kg-1 in downlink mode, i.e. within the limits of the ICNIRP 1998 Guidelines; (2) in both uplink and downlink mode the highest SAR values were approximately found in the same tissues, i.e. in the skin, eye and penis for the whole-tissue SAR and in the bone, skin and muscle for the peak SAR; (3) the change in the position of both the 3G tablet and the 3G femtocell significantly influences the infant exposure.

Onboard Science and Applications Algorithm for Hyperspectral Data Reduction

NASA Technical Reports Server (NTRS)

Chien, Steve A.; Davies, Ashley G.; Silverman, Dorothy; Mandl, Daniel

2012-01-01

An onboard processing mission concept is under development for a possible Direct Broadcast capability for the HyspIRI mission, a Hyperspectral remote sensing mission under consideration for launch in the next decade. The concept would intelligently spectrally and spatially subsample the data as well as generate science products onboard to enable return of key rapid response science and applications information despite limited downlink bandwidth. This rapid data delivery concept focuses on wildfires and volcanoes as primary applications, but also has applications to vegetation, coastal flooding, dust, and snow/ice applications. Operationally, the HyspIRI team would define a set of spatial regions of interest where specific algorithms would be executed. For example, known coastal areas would have certain products or bands downlinked, ocean areas might have other bands downlinked, and during fire seasons other areas would be processed for active fire detections. Ground operations would automatically generate the mission plans specifying the highest priority tasks executable within onboard computation, setup, and data downlink constraints. The spectral bands of the TIR (thermal infrared) instrument can accurately detect the thermal signature of fires and send down alerts, as well as the thermal and VSWIR (visible to short-wave infrared) data corresponding to the active fires. Active volcanism also produces a distinctive thermal signature that can be detected onboard to enable spatial subsampling. Onboard algorithms and ground-based algorithms suitable for onboard deployment are mature. On HyspIRI, the algorithm would perform a table-driven temperature inversion from several spectral TIR bands, and then trigger downlink of the entire spectrum for each of the hot pixels identified. Ocean and coastal applications include sea surface temperature (using a small spectral subset of TIR data, but requiring considerable ancillary data), and ocean color applications to track biological activity such as harmful algal blooms. Measuring surface water extent to track flooding is another rapid response product leveraging VSWIR spectral information.

NPOESS Field Terminal Updates

NASA Astrophysics Data System (ADS)

Heckmann, G.; Route, G.

2009-12-01

The National Oceanic and Atmospheric Administration (NOAA), Department of Defense (DoD), and National Aeronautics and Space Administration (NASA) are jointly acquiring the next-generation weather and environmental satellite system; the National Polar-orbiting Operational Environmental Satellite System (NPOESS). NPOESS replaces the current Polar-orbiting Operational Environmental Satellites (POES) managed by NOAA and the Defense Meteorological Satellite Program (DMSP) managed by the DoD. The NPOESS satellites carry a suite of sensors that collect meteorological, oceanographic, climatological, and solar-geophysical observations of the earth, atmosphere, and space. The ground data processing segment for NPOESS is the Interface Data Processing Segment (IDPS), developed by Raytheon Intelligence and Information Systems. The IDPS processes NPOESS satellite data to provide environmental data products (aka, Environmental Data Records or EDRs) to NOAA and DoD processing centers operated by the United States government. The IDPS will process EDRs beginning with the NPOESS Preparatory Project (NPP) and continuing through the lifetime of the NPOESS system. IDPS also provides the software and requirements for the Field Terminal Segment (FTS). NPOESS provides support to deployed field terminals by providing mission data in the Low Rate and High Rate downlinks (LRD/HRD), mission support data needed to generate EDRs and decryption keys needed to decrypt mission data during Selective data Encryption (SDE). Mission support data consists of globally relevant data, geographically constrained data, and two line element sets. NPOESS provides these mission support data via the Internet accessible Mission Support Data Server and HRD/LRD downlinks. This presentation will illustrate and describe the NPOESS capabilities in support of Field Terminal users. This discussion will include the mission support data available to Field Terminal users, content of the direct broadcast HRD and LRD downlinks identifying differences between the direct broadcast downlinks including the variability of the LRD downlink and NPOESS management and distribution of decryption keys to approved field terminals using Public Key Infrastructure (PKI) AES standard with 256 bit encryption and elliptical curve cryptography.

Exposure assessment of one-year-old child to 3G tablet in uplink mode and to 3G femtocell in downlink mode using polynomial chaos decomposition.

PubMed

Liorni, I; Parazzini, M; Varsier, N; Hadjem, A; Ravazzani, P; Wiart, J

2016-04-21

So far, the assessment of the exposure of children, in the ages 0-2 years old, to relatively new radio-frequency (RF) technologies, such as tablets and femtocells, remains an open issue. This study aims to analyse the exposure of a one year-old child to these two sources, tablets and femtocells, operating in uplink (tablet) and downlink (femtocell) modes, respectively. In detail, a realistic model of an infant has been used to model separately the exposures due to (i) a 3G tablet emitting at the frequency of 1940 MHz (uplink mode) placed close to the body and (ii) a 3G femtocell emitting at 2100 MHz (downlink mode) placed at a distance of at least 1 m from the infant body. For both RF sources, the input power was set to 250 mW. The variability of the exposure due to the variation of the position of the RF sources with respect to the infant body has been studied by stochastic dosimetry, based on polynomial chaos to build surrogate models of both whole-body and tissue specific absorption rate (SAR), which makes it easy and quick to investigate the exposure in a full range of possible positions of the sources. The major outcomes of the study are: (1) the maximum values of the whole-body SAR (WB SAR) have been found to be 9.5 mW kg(-1) in uplink mode and 65 μW kg(-1) in downlink mode, i.e. within the limits of the ICNIRP 1998 Guidelines; (2) in both uplink and downlink mode the highest SAR values were approximately found in the same tissues, i.e. in the skin, eye and penis for the whole-tissue SAR and in the bone, skin and muscle for the peak SAR; (3) the change in the position of both the 3G tablet and the 3G femtocell significantly influences the infant exposure.

The fabrication of vertically aligned and periodically distributed carbon nanotube bundles and periodically porous carbon nanotube films through a combination of laser interference ablation and metal-catalyzed chemical vapor deposition.

PubMed

Yuan, Dajun; Lin, Wei; Guo, Rui; Wong, C P; Das, Suman

2012-06-01

Scalable fabrication of carbon nanotube (CNT) bundles is essential to future advances in several applications. Here, we report on the development of a simple, two-step method for fabricating vertically aligned and periodically distributed CNT bundles and periodically porous CNT films at the sub-micron scale. The method involves laser interference ablation (LIA) of an iron film followed by CNT growth via iron-catalyzed chemical vapor deposition. CNT bundles with square widths ranging from 0.5 to 1.5 µm in width, and 50-200 µm in length, are grown atop the patterned catalyst over areas spanning 8 cm(2). The CNT bundles exhibit a high degree of control over square width, orientation, uniformity, and periodicity. This simple scalable method of producing well-placed and oriented CNT bundles demonstrates a high application potential for wafer-scale integration of CNT structures into various device applications, including IC interconnects, field emitters, sensors, batteries, and optoelectronics, etc.

SATCOM Supply Versus Demand and the Impact on Remotely Piloted Aircraft ISR

DTIC Science & Technology

2016-03-01

produced a laser transmitter called OPALS , which successfully transmitted both text and video from the International Space Station to a ground control...station. In one test, a video which took 12 hours to upload via traditional radio frequency was downloaded in a mere seven seconds using OPALS .52 ESA...enhanced Ku-band IntelsatEpic satellites to be launched in 2016 will provide 200Mbps downlink data rate, while OPALS and EDRS provide 1.8Gbps downlink

Adaptive nonlinear Volterra equalizer for mitigation of chirp-induced distortions in cost effective IMDD OFDM systems.

PubMed

André, Nuno Sequeira; Habel, Kai; Louchet, Hadrien; Richter, André

2013-11-04

We report experimental validations of an adaptive 2nd order Volterra equalization scheme for cost effective IMDD OFDM systems. This equalization scheme was applied to both uplink and downlink transmission. Downlink settings were optimized for maximum bitrate where we achieved 34 Gb/s over 10 km of SSMF using an EML with 10 GHz bandwidth. For the uplink, maximum reach was optimized achieving 14 Gb/s using a low-cost DML with 2.5 GHz bandwidth.

A Synchronous Digital Duplexing Technique for OFDMA-Based Indoor Communications

NASA Astrophysics Data System (ADS)

Park, Chang-Hwan; Ko, Yo-Han; Kim, Yeong-Jun; Park, Kyung-Won; Jeon, Won-Gi; Paik, Jong-Ho; Lee, Seok-Pil; Cho, Yong-Soo

In this paper, we propose a new digital duplexing scheme, called synchronous digital duplexing (SDD), which can increase data efficiency and flexibility of resource by transmitting uplink signal and downlink signal simultaneously in wireless communication. In order to transmit uplink and downlink signals simultaneously, the proposed SDD obtains mutual information among subscriber stations (SSs) with a mutual ranging symbol. This information is used for selection of transmission time, decision on cyclic suffix (CS) insertion, determination of CS length, and re-establishment of FFT starting point.

Transceiver optics for interplanetary communications

NASA Astrophysics Data System (ADS)

Roberts, W. T.; Farr, W. H.; Rider, B.; Sampath, D.

2017-11-01

In-situ interplanetary science missions constantly push the spacecraft communications systems to support successively higher downlink rates. However, the highly restrictive mass and power constraints placed on interplanetary spacecraft significantly limit the desired bandwidth increases in going forward with current radio frequency (RF) technology. To overcome these limitations, we have evaluated the ability of free-space optical communications systems to make substantial gains in downlink bandwidth, while holding to the mass and power limits allocated to current state-of-the-art Ka-band communications systems. A primary component of such an optical communications system is the optical assembly, comprised of the optical support structure, optical elements, baffles and outer enclosure. We wish to estimate the total mass that such an optical assembly might require, and assess what form it might take. Finally, to ground this generalized study, we should produce a conceptual design, and use that to verify its ability to achieve the required downlink gain, estimate it's specific optical and opto-mechanical requirements, and evaluate the feasibility of producing the assembly.

Adaptive optics correction into single mode fiber for a low Earth orbiting space to ground optical communication link using the OPALS downlink.

PubMed

Wright, Malcolm W; Morris, Jeffery F; Kovalik, Joseph M; Andrews, Kenneth S; Abrahamson, Matthew J; Biswas, Abhijit

2015-12-28

An adaptive optics (AO) testbed was integrated to the Optical PAyload for Lasercomm Science (OPALS) ground station telescope at the Optical Communications Telescope Laboratory (OCTL) as part of the free space laser communications experiment with the flight system on board the International Space Station (ISS). Atmospheric turbulence induced aberrations on the optical downlink were adaptively corrected during an overflight of the ISS so that the transmitted laser signal could be efficiently coupled into a single mode fiber continuously. A stable output Strehl ratio of around 0.6 was demonstrated along with the recovery of a 50 Mbps encoded high definition (HD) video transmission from the ISS at the output of the single mode fiber. This proof of concept demonstration validates multi-Gbps optical downlinks from fast slewing low-Earth orbiting (LEO) spacecraft to ground assets in a manner that potentially allows seamless space to ground connectivity for future high data-rates network.

Solving the Swath Segment Selection Problem

NASA Technical Reports Server (NTRS)

Knight, Russell; Smith, Benjamin

2006-01-01

Several artificial-intelligence search techniques have been tested as means of solving the swath segment selection problem (SSSP) -- a real-world problem that is not only of interest in its own right, but is also useful as a test bed for search techniques in general. In simplest terms, the SSSP is the problem of scheduling the observation times of an airborne or spaceborne synthetic-aperture radar (SAR) system to effect the maximum coverage of a specified area (denoted the target), given a schedule of downlinks (opportunities for radio transmission of SAR scan data to a ground station), given the limit on the quantity of SAR scan data that can be stored in an onboard memory between downlink opportunities, and given the limit on the achievable downlink data rate. The SSSP is NP complete (short for "nondeterministic polynomial time complete" -- characteristic of a class of intractable problems that can be solved only by use of computers capable of making guesses and then checking the guesses in polynomial time).

Onboard Classifiers for Science Event Detection on a Remote Sensing Spacecraft

NASA Technical Reports Server (NTRS)

Castano, Rebecca; Mazzoni, Dominic; Tang, Nghia; Greeley, Ron; Doggett, Thomas; Cichy, Ben; Chien, Steve; Davies, Ashley

2006-01-01

Typically, data collected by a spacecraft is downlinked to Earth and pre-processed before any analysis is performed. We have developed classifiers that can be used onboard a spacecraft to identify high priority data for downlink to Earth, providing a method for maximizing the use of a potentially bandwidth limited downlink channel. Onboard analysis can also enable rapid reaction to dynamic events, such as flooding, volcanic eruptions or sea ice break-up. Four classifiers were developed to identify cryosphere events using hyperspectral images. These classifiers include a manually constructed classifier, a Support Vector Machine (SVM), a Decision Tree and a classifier derived by searching over combinations of thresholded band ratios. Each of the classifiers was designed to run in the computationally constrained operating environment of the spacecraft. A set of scenes was hand-labeled to provide training and testing data. Performance results on the test data indicate that the SVM and manual classifiers outperformed the Decision Tree and band-ratio classifiers with the SVM yielding slightly better classifications than the manual classifier.

Generation of helical Ince-Gaussian beams: beam-shaping with a liquid crystal display

NASA Astrophysics Data System (ADS)

Davis, Jeffrey A.; Bentley, Joel B.; Bandres, Miguel A.; Gutiérrez-Vega, Julio C.

2006-08-01

We review the three types of laser beams - Hermite-Gaussian (HG), Laguerre-Gaussian (LG) and the newly discovered Ince-Gaussian (IG) beams. We discuss the helical forms of the LG and IG beams that consist of linear combinations of the even and odd solutions and form a number of vortices that are useful for optical trapping applications. We discuss how to generate these beams by encoding the desired amplitude and phase onto a single parallel-aligned liquid crystal display (LCD). We introduce a novel interference technique where we generate both the object and reference beams using a single LCD and show the vortex interference patterns.

Operation of a separated-type x-ray interferometer for phase-contrast x-ray imaging

NASA Astrophysics Data System (ADS)

Yoneyama, Akio; Momose, Atsushi; Seya, Eiichi; Hirano, Keiichi; Takeda, Tohoru; Itai, Yuji

1999-12-01

Aiming at large-area phase-contrast x-ray imaging, a separated-type x-ray interferometer system was designed and developed to produce 25×20 mm interference patterns. The skew-symmetric optical system was adopted because of the feasibility of alignment. The rotation between the separated crystal blocks was controlled within a drift of 0.06 nrad using a feedback positioning system. This interferometer generated a 25×15 mm interference pattern with 0.07 nm synchrotron x-rays. A slice of a rabbit's kidney was observed, and its tubular structure could be revealed in a measured phase map.

Computationally Efficient Power Allocation Algorithm in Multicarrier-Based Cognitive Radio Networks: OFDM and FBMC Systems

NASA Astrophysics Data System (ADS)

Shaat, Musbah; Bader, Faouzi

2010-12-01

Cognitive Radio (CR) systems have been proposed to increase the spectrum utilization by opportunistically access the unused spectrum. Multicarrier communication systems are promising candidates for CR systems. Due to its high spectral efficiency, filter bank multicarrier (FBMC) can be considered as an alternative to conventional orthogonal frequency division multiplexing (OFDM) for transmission over the CR networks. This paper addresses the problem of resource allocation in multicarrier-based CR networks. The objective is to maximize the downlink capacity of the network under both total power and interference introduced to the primary users (PUs) constraints. The optimal solution has high computational complexity which makes it unsuitable for practical applications and hence a low complexity suboptimal solution is proposed. The proposed algorithm utilizes the spectrum holes in PUs bands as well as active PU bands. The performance of the proposed algorithm is investigated for OFDM and FBMC based CR systems. Simulation results illustrate that the proposed resource allocation algorithm with low computational complexity achieves near optimal performance and proves the efficiency of using FBMC in CR context.

Downlink Probability Density Functions for EOS-McMurdo Sound

NASA Technical Reports Server (NTRS)

Christopher, P.; Jackson, A. H.

1996-01-01

The visibility times and communication link dynamics for the Earth Observations Satellite (EOS)-McMurdo Sound direct downlinks have been studied. The 16 day EOS periodicity may be shown with the Goddard Trajectory Determination System (GTDS) and the entire 16 day period should be simulated for representative link statistics. We desire many attributes of the downlink, however, and a faster orbital determination method is desirable. We use the method of osculating elements for speed and accuracy in simulating the EOS orbit. The accuracy of the method of osculating elements is demonstrated by closely reproducing the observed 16 day Landsat periodicity. An autocorrelation function method is used to show the correlation spike at 16 days. The entire 16 day record of passes over McMurdo Sound is then used to generate statistics for innage time, outage time, elevation angle, antenna angle rates, and propagation loss. The levation angle probability density function is compared with 1967 analytic approximation which has been used for medium to high altitude satellites. One practical result of this comparison is seen to be the rare occurrence of zenith passes. The new result is functionally different than the earlier result, with a heavy emphasis on low elevation angles. EOS is one of a large class of sun synchronous satellites which may be downlinked to McMurdo Sound. We examine delay statistics for an entire group of sun synchronous satellites ranging from 400 km to 1000 km altitude. Outage probability density function results are presented three dimensionally.

Pointing History Engine for the Spitzer Space Telescope

NASA Technical Reports Server (NTRS)

Bayard, David; Ahmed, Asif; Brugarolas, Paul

2007-01-01

The Pointing History Engine (PHE) is a computer program that provides mathematical transformations needed to reconstruct, from downlinked telemetry data, the attitude of the Spitzer Space Telescope (formerly known as the Space Infrared Telescope Facility) as a function of time. The PHE also serves as an example for development of similar pointing reconstruction software for future space telescopes. The transformations implemented in the PHE take account of the unique geometry of the Spitzer telescope-pointing chain, including all data on relative alignments of components, and all information available from attitude-determination instruments. The PHE makes it possible to coordinate attitude data with observational data acquired at the same time, so that any observed astronomical object can be located for future reference and re-observation. The PHE is implemented as a subroutine used in conjunction with telemetry-formatting services of the Mission Image Processing Laboratory of NASA s Jet Propulsion Laboratory to generate the Boresight Pointing History File (BPHF). The BPHF is an archival database designed to serve as Spitzer s primary astronomical reference documenting where the telescope was pointed at any time during its mission.

Interference effect on a heavy Higgs resonance signal in the γ γ and Z Z channels

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

Song, Jeonghyeon; Yoon, Yeo Woong; Jung, Sunghoon

2016-03-24

The resonance-continuum interference is usually neglected when the width of a resonance is small compared to the resonance mass. We reexamine this standard by studying the interference effects in high-resolution decay channels, γγ and ZZ, of the heavy Higgs boson H in nearly aligned two-Higgs-doublet models. For the H with a sub-percent width-to-mass ratio, we find that, in the parameter space where the LHC 14 TeV ZZ resonance search can be sensitive, the interference effects can modify the ZZ signal rate by O(10)% and the exclusion reach by O(10) GeV. In other parameter space where the ZZ or γγ signalmore » rate is smaller, the LHC 14 TeV reach is absent, but a resonance shape can be much more dramatically changed. In particular, the γγ signal rate can change by O(100)%. Relevant to such parameter space, we suggest variables that can characterize a general resonance shape. Furthermore, we also illustrate the relevance of the width on the interference by adding nonstandard decay modes of the heavy Higgs boson.« less

Improved Phase-Mask Fabrication of Fiber Bragg Gratings

NASA Technical Reports Server (NTRS)

Grant, Joseph; Wang, Ying; Sharma, Anup

2004-01-01

An improved method of fabrication of Bragg gratings in optical fibers combines the best features of two prior methods: one that involves the use of a phase mask and one that involves interference between the two coherent laser beams. The improved method affords flexibility for tailoring Bragg wavelengths and bandwidths over wide ranges. A Bragg grating in an optical fiber is a periodic longitudinal variation in the index of refraction of the fiber core. The spatial period (Bragg wavelength) is chosen to obtain enhanced reflection of light of a given wavelength that would otherwise propagate relatively unimpeded along the core. Optionally, the spatial period of the index modulation can be made to vary gradually along the grating (such a grating is said to be chirped ) in order to obtain enhanced reflection across a wavelength band, the width of which is determined by the difference between the maximum and minimum Bragg wavelengths. In the present method as in both prior methods, a Bragg grating is formed by exposing an optical fiber to an ultraviolet-light interference field. The Bragg grating coincides with the pattern of exposure of the fiber core to ultraviolet light; in other words, the Bragg grating coincides with the interference fringes. Hence, the problem of tailoring the Bragg wavelength and bandwidth is largely one of tailoring the interference pattern and the placement of the fiber in the interference pattern. In the prior two-beam interferometric method, a single laser beam is split into two beams, which are subsequently recombined to produce an interference pattern at the location of an optical fiber. In the prior phase-mask method, a phase mask is used to diffract a laser beam mainly into two first orders, the interference between which creates the pattern to which an optical fiber is exposed. The prior two-beam interferometric method offers the advantage that the period of the interference pattern can be adjusted to produce gratings over a wide range of Bragg wavelengths, but offers the disadvantage that success depends on precise alignment and high mechanical stability. The prior phase-mask method affords the advantages of compactness of equipment and relative insensitivity to both misalignment and vibration, but does not afford adjustability of the Bragg wavelength. The present method affords both the flexibility of the prior two-beam interferometric method and the compactness and stability of the prior phase-mask method. In this method (see figure), a laser beam propagating along the x axis is normally incident on a phase mask that lies in the (y,z) plane. The phase of light propagating through the mask is modulated with a spatial periodicity, p, along the y axis chosen to diffract the laser light primarily to first order at the angle . (The zero-order laser light propagating along the x axis can be used for alignment and thereafter suppressed during exposure of the fiber.) The diffracted light passes through a concave cylindrical lens, which converts the flat diffracted wave fronts to cylindrical ones, as though the light emanated from a line source. Then two parallel flat mirrors recombine the diffracted beams to form an interference field equivalent to that of two coherent line sources at positions A and B (virtual sources). The interference pattern is a known function of the parameters of the apparatus and of position (x,y) in the interference field. Hence, the tilt, wavelength, and chirp of the Bragg grating can be chosen through suitable adjustments of the apparatus and/or of the position and orientation of the optical fiber. In particular, the Bragg wavelength can be adjusted by moving the fiber along the x axis, and the bandwidth can be modified over a wide range by changing the fiber tilt angle or by moving the phase mask and/or the fiber. Alignment is easy because the zero-order beam defines the x axis. The interference is relatively stable and insensitive to the mechanical vibration because of the gh symmetry and compactness of the apparatus, the fixed positions of the mirrors and lens, and the consequent fixed positions of the two virtual line sources, which are independent of the translations of the phase mask and the laser relative to the lens.

Outer planet Pioneer imaging communications system study. [data compression

NASA Technical Reports Server (NTRS)

1974-01-01

The effects of different types of imaging data compression on the elements of the Pioneer end-to-end data system were studied for three imaging transmission methods. These were: no data compression, moderate data compression, and the advanced imaging communications system. It is concluded that: (1) the value of data compression is inversely related to the downlink telemetry bit rate; (2) the rolling characteristics of the spacecraft limit the selection of data compression ratios; and (3) data compression might be used to perform acceptable outer planet mission at reduced downlink telemetry bit rates.

OPALS: A COTS-based Tech Demo of Optical Communications

NASA Technical Reports Server (NTRS)

Oaida, Bogdan

2012-01-01

I. Objective: Deliver video from ISS to optical ground terminal via an optical communications link. a) JPL Phaeton/Early Career Hire (ECH) training project. b) Implemented as Class-D payload. c) Downlink at approx.30Mb/s. II. Flight System a) Optical Head Beacon Acquisition Camera. Downlink Transmitter. 2-axis Gimbal. b) Sealed Container Laser Avionics Power distribution Digital I/O board III. Implementation: a) Ground Station - Optical Communications Telescope Laboratory at Table Mountain Facility b) Flight System mounted to ISS FRAM as standard I/F. Attached externally on Express Logistics Carrier.

Satellite diversity and its implications on the RAKE receiver architecture for CDMA-based S-PCN's

NASA Technical Reports Server (NTRS)

Taaghol, P.; Sammut, A.; Tafazolli, R.; Evans, B. G.

1995-01-01

In this paper we examine the applicability of RAKE receivers in a mobile LEO satellite channel and identify the potential problem areas. We then proceed to investigate the possibility of a coherent combining architecture (downlink) in the presence of satellite diversity. We closely examine the path delay difference statistics of a diversity channel and propose a delay compensation scheme for the downlink in order to reduce the complexity of the user terminal. Finally, the required modifications to the conventional RAKE receiver are proposed and discussed.

Students Speak with the ISS

NASA Image and Video Library

2012-11-15

Leland Melvin, NASA Associate Administrator for Education and two-time space shuttle astronaut, answers a question from a student in a live video downlink at the Smithsonian National Air and Space Museum, Thursday, Nov. 15, 2012 in Washington. The students, participants from the Student Spaceflight Experiments Program (SSEP) conducted a live conversation with astronauts aboard the International Space Station. The downlink is an annual event held in honor of International Education Week, and was co-hosted with the Department of Education and the National Center for Earth and Space Science Education (NCESSE). Photo Credit: (NASA/Carla Cioffi)

Information Switching Processor (ISP) contention analysis and control

NASA Technical Reports Server (NTRS)

Shyy, D.; Inukai, T.

1993-01-01

Future satellite communications, as a viable means of communications and an alternative to terrestrial networks, demand flexibility and low end-user cost. On-board switching/processing satellites potentially provide these features, allowing flexible interconnection among multiple spot beams, direct to the user communications services using very small aperture terminals (VSAT's), independent uplink and downlink access/transmission system designs optimized to user's traffic requirements, efficient TDM downlink transmission, and better link performance. A flexible switching system on the satellite in conjunction with low-cost user terminals will likely benefit future satellite network users.

GenomeVista

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

Poliakov, Alexander; Couronne, Olivier

2002-11-04

Aligning large vertebrate genomes that are structurally complex poses a variety of problems not encountered on smaller scales. Such genomes are rich in repetitive elements and contain multiple segmental duplications, which increases the difficulty of identifying true orthologous SNA segments in alignments. The sizes of the sequences make many alignment algorithms designed for comparing single proteins extremely inefficient when processing large genomic intervals. We integrated both local and global alignment tools and developed a suite of programs for automatically aligning large vertebrate genomes and identifying conserved non-coding regions in the alignments. Our method uses the BLAT local alignment program tomore » find anchors on the base genome to identify regions of possible homology for a query sequence. These regions are postprocessed to find the best candidates which are then globally aligned using the AVID global alignment program. In the last step conserved non-coding segments are identified using VISTA. Our methods are fast and the resulting alignments exhibit a high degree of sensitivity, covering more than 90% of known coding exons in the human genome. The GenomeVISTA software is a suite of Perl programs that is built on a MySQL database platform. The scheduler gets control data from the database, builds a queve of jobs, and dispatches them to a PC cluster for execution. The main program, running on each node of the cluster, processes individual sequences. A Perl library acts as an interface between the database and the above programs. The use of a separate library allows the programs to function independently of the database schema. The library also improves on the standard Perl MySQL database interfere package by providing auto-reconnect functionality and improved error handling.« less

An NFC on Two-Coil WPT Link for Implantable Biomedical Sensors under Ultra-Weak Coupling

PubMed Central

Gong, Chen; Liu, Dake; Miao, Zhidong; Wang, Wei; Li, Min

2017-01-01

The inductive link is widely used in implantable biomedical sensor systems to achieve near-field communication (NFC) and wireless power transfer (WPT). However, it is tough to achieve reliable NFC on an inductive WPT link when the coupling coefficient is ultra-low (0.01 typically), since the NFC signal (especially for the uplink from the in-body part to the out-body part) could be too weak to be detected. Traditional load shift keying (LSK) requires strong coupling to pass the load modulation information to the power source. Instead of using LSK, we propose a dual-carrier NFC scheme for the weak-coupled inductive link; using binary phase shift keying (BPSK) modulation, its downlink data are modulated on the power carrier (2 MHz), while its uplink data are modulated on another carrier (125 kHz). The two carriers are transferred through the same coil pair. To overcome the strong interference of the power carrier, dedicated circuits are introduced. In addition, to minimize the power transfer efficiency decrease caused by adding NFC, we optimize the inductive link circuit parameters and approach the receiver sensitivity limit. In the prototype experiments, even though the coupling coefficient is as low as 0.008, the in-body transmitter costs only 0.61 mW power carrying 10 kbps of data, and achieves a 1 × 10−7 bit error rate under the strong interference of WPT. This dual-carrier NFC scheme could be useful for small-sized implantable biomedical sensor applications. PMID:28604610

Rice crop growth monitoring using ENVISAT-1/ASAR AP mode

NASA Astrophysics Data System (ADS)

Konishi, Tomohisa; Suga, Yuzo; Omatu, Shigeru; Takeuchi, Shoji; Asonuma, Kazuyoshi

2007-10-01

Hiroshima Institute of Technology (HIT) is operating the direct down-links of microwave and optical earth observation satellite data in Japan. This study focuses on the validation for rice crop monitoring using microwave remotely sensed image data acquired by ENIVISAT-1 referring to ground truth data such as height of rice crop, vegetation cover rate and leaf area index in the test sites of Hiroshima district, the western part of Japan. ENVISAT-1/ASAR data has the capabilities for the monitoring of the rice crop growing cycle by using alternating cross polarization mode images. However, ASAR data is influenced by several parameters such as land cover structure, direction and alignment of rice crop fields in the test sites. In this study, the validation was carried out to be combined with microwave image data and ground truth data regarding rice crop fields to investigate the above parameters. Multi-temporal, multi-direction (descending and ascending) and multi-angle ASAR alternating cross polarization mode images were used to investigate during the rice crop growing cycle. On the other hand, LANDSAT-7/ETM+ data were used to detect land cover structure, direction and alignment of rice crop fields corresponding to the backscatter of ASAR. Finally, the extraction of rice planted area was attempted by using multi-temporal ASAR AP mode data such as VV/VH and HH/HV. As the result of this study, it is clear that the estimated rice planted area coincides with the existing statistical data for area of the rice crop field. In addition, HH/HV is more effective than VV/VH in the rice planted area extraction.

Radiofrequency radiation at Stockholm Central Railway Station in Sweden and some medical aspects on public exposure to RF fields.

PubMed

Hardell, Lennart; Koppel, Tarmo; Carlberg, Michael; Ahonen, Mikko; Hedendahl, Lena

2016-10-01

The Stockholm Central Railway Station in Sweden was investigated for public radiofrequency (RF) radiation exposure. The exposimeter EME Spy 200 was used to collect the RF exposure data across the railway station. The exposimeter covers 20 different radiofrequency bands from 88 to 5,850 MHz. In total 1,669 data points were recorded. The median value for total exposure was 921 µW/m2 (or 0.092 µW/cm2; 1 µW/m2=0.0001 µW/cm2) with some outliers over 95,544 µW/m2 (6 V/m, upper detection limit). The mean total RF radiation level varied between 2,817 to 4,891 µW/m2 for each walking round. High mean measurements were obtained for GSM + UMTS 900 downlink varying between 1,165 and 2,075 µW/m2. High levels were also obtained for UMTS 2100 downlink; 442 to 1,632 µW/m2. Also LTE 800 downlink, GSM 1800 downlink, and LTE 2600 downlink were in the higher range of measurements. Hot spots were identified, for example close to a wall mounted base station yielding over 95,544 µW/m2 and thus exceeding the exposimeter's detection limit. Almost all of the total measured levels were above the precautionary target level of 3-6 µW/m2 as proposed by the BioInitiative Working Group in 2012. That target level was one-tenth of the scientific benchmark providing a safety margin either for children, or chronic exposure conditions. We compare the levels of RF radiation exposures identified in the present study to published scientific results reporting adverse biological effects and health harm at levels equivalent to, or below those measured in this Stockholm Central Railway Station project. It should be noted that these RF radiation levels give transient exposure, since people are generally passing through the areas tested, except for subsets of people who are there for hours each day of work.

Radiofrequency radiation at Stockholm Central Railway Station in Sweden and some medical aspects on public exposure to RF fields

PubMed Central

Hardell, Lennart; Koppel, Tarmo; Carlberg, Michael; Ahonen, Mikko; Hedendahl, Lena

2016-01-01

The Stockholm Central Railway Station in Sweden was investigated for public radiofrequency (RF) radiation exposure. The exposimeter EME Spy 200 was used to collect the RF exposure data across the railway station. The exposimeter covers 20 different radiofrequency bands from 88 to 5,850 MHz. In total 1,669 data points were recorded. The median value for total exposure was 921 μW/m2 (or 0.092 μW/cm2; 1 μW/m2=0.0001 μW/cm2) with some outliers over 95,544 μW/m2 (6 V/m, upper detection limit). The mean total RF radiation level varied between 2,817 to 4,891 μW/m2 for each walking round. High mean measurements were obtained for GSM + UMTS 900 downlink varying between 1,165 and 2,075 μW/m2. High levels were also obtained for UMTS 2100 downlink; 442 to 1,632 μW/m2. Also LTE 800 downlink, GSM 1800 downlink, and LTE 2600 downlink were in the higher range of measurements. Hot spots were identified, for example close to a wall mounted base station yielding over 95,544 μW/m2 and thus exceeding the exposimeter's detection limit. Almost all of the total measured levels were above the precautionary target level of 3–6 μW/m2 as proposed by the BioInitiative Working Group in 2012. That target level was one-tenth of the scientific benchmark providing a safety margin either for children, or chronic exposure conditions. We compare the levels of RF radiation exposures identified in the present study to published scientific results reporting adverse biological effects and health harm at levels equivalent to, or below those measured in this Stockholm Central Railway Station project. It should be noted that these RF radiation levels give transient exposure, since people are generally passing through the areas tested, except for subsets of people who are there for hours each day of work. PMID:27633090

Rover Sequencing and Visualization Program

NASA Technical Reports Server (NTRS)

Cooper, Brian; Hartman, Frank; Maxwell, Scott; Yen, Jeng; Wright, John; Balacuit, Carlos

2005-01-01

The Rover Sequencing and Visualization Program (RSVP) is the software tool for use in the Mars Exploration Rover (MER) mission for planning rover operations and generating command sequences for accomplishing those operations. RSVP combines three-dimensional (3D) visualization for immersive exploration of the operations area, stereoscopic image display for high-resolution examination of the downlinked imagery, and a sophisticated command-sequence editing tool for analysis and completion of the sequences. RSVP is linked with actual flight-code modules for operations rehearsal to provide feedback on the expected behavior of the rover prior to committing to a particular sequence. Playback tools allow for review of both rehearsed rover behavior and downlinked results of actual rover operations. These can be displayed simultaneously for comparison of rehearsed and actual activities for verification. The primary inputs to RSVP are downlink data products from the Operations Storage Server (OSS) and activity plans generated by the science team. The activity plans are high-level goals for the next day s activities. The downlink data products include imagery, terrain models, and telemetered engineering data on rover activities and state. The Rover Sequence Editor (RoSE) component of RSVP performs activity expansion to command sequences, command creation and editing with setting of command parameters, and viewing and management of rover resources. The HyperDrive component of RSVP performs 2D and 3D visualization of the rover s environment, graphical and animated review of rover-predicted and telemetered state, and creation and editing of command sequences related to mobility and Instrument Deployment Device (IDD) operations. Additionally, RoSE and HyperDrive together evaluate command sequences for potential violations of flight and safety rules. The products of RSVP include command sequences for uplink that are stored in the Distributed Object Manager (DOM) and predicted rover state histories stored in the OSS for comparison and validation of downlinked telemetry. The majority of components comprising RSVP utilize the MER command and activity dictionaries to automatically customize the system for MER activities. Thus, RSVP, being highly data driven, may be tailored to other missions with minimal effort. In addition, RSVP uses a distributed, message-passing architecture to allow multitasking, and collaborative visualization and sequence development by scattered team members.

Update on Rover Sequencing and Visualization Program

NASA Technical Reports Server (NTRS)

Cooper, Brian; Hartman, Frank; Maxwell, Scott; Yen, Jeng; Wright, John; Balacuit, Carlos

2005-01-01

The Rover Sequencing and Visualization Program (RSVP) has been updated. RSVP was reported in Rover Sequencing and Visualization Program (NPO-30845), NASA Tech Briefs, Vol. 29, No. 4 (April 2005), page 38. To recapitulate: The Rover Sequencing and Visualization Program (RSVP) is the software tool to be used in the Mars Exploration Rover (MER) mission for planning rover operations and generating command sequences for accomplishing those operations. RSVP combines three-dimensional (3D) visualization for immersive exploration of the operations area, stereoscopic image display for high-resolution examination of the downlinked imagery, and a sophisticated command-sequence editing tool for analysis and completion of the sequences. RSVP is linked with actual flight code modules for operations rehearsal to provide feedback on the expected behavior of the rover prior to committing to a particular sequence. Playback tools allow for review of both rehearsed rover behavior and downlinked results of actual rover operations. These can be displayed simultaneously for comparison of rehearsed and actual activities for verification. The primary inputs to RSVP are downlink data products from the Operations Storage Server (OSS) and activity plans generated by the science team. The activity plans are high-level goals for the next day s activities. The downlink data products include imagery, terrain models, and telemetered engineering data on rover activities and state. The Rover Sequence Editor (RoSE) component of RSVP performs activity expansion to command sequences, command creation and editing with setting of command parameters, and viewing and management of rover resources. The HyperDrive component of RSVP performs 2D and 3D visualization of the rover s environment, graphical and animated review of rover predicted and telemetered state, and creation and editing of command sequences related to mobility and Instrument Deployment Device (robotic arm) operations. Additionally, RoSE and HyperDrive together evaluate command sequences for potential violations of flight and safety rules. The products of RSVP include command sequences for uplink that are stored in the Distributed Object Manager (DOM) and predicted rover state histories stored in the OSS for comparison and validation of downlinked telemetry. The majority of components comprising RSVP utilize the MER command and activity dictionaries to automatically customize the system for MER activities.

Control techniques to improve Space Shuttle solid rocket booster separation

NASA Technical Reports Server (NTRS)

Tomlin, D. D.

1983-01-01

The present Space Shuttle's control system does not prevent the Orbiter's main engines from being in gimbal positions that are adverse to solid rocket booster separation. By eliminating the attitude error and attitude rate feedback just prior to solid rocket booster separation, the detrimental effects of the Orbiter's main engines can be reduced. In addition, if angular acceleration feedback is applied, the gimbal torques produced by the Orbiter's engines can reduce the detrimental effects of the aerodynamic torques. This paper develops these control techniques and compares the separation capability of the developed control systems. Currently with the worst case initial conditions and each Shuttle system dispersion aligned in the worst direction (which is more conservative than will be experienced in flight), the solid rocket booster has an interference with the Shuttle's external tank of 30 in. Elimination of the attitude error and attitude rate feedback reduces that interference to 19 in. Substitution of angular acceleration feedback reduces the interference to 6 in. The two latter interferences can be eliminated by atess conservative analysis techniques, that is, by using a root sum square of the system dispersions.

Understanding Beam Alignment in a Coherent Lidar System

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Roychoudhari, Chandrasekhar

2015-01-01

Optical beam alignment in a coherent lidar (or ladar) receiver system plays a critical role in optimizing its performance. Optical alignment in a coherent lidar system dictates the wavefront curvature (phase front) and Poynting vector) matching of the local oscillator beam with the incoming receiver beam on a detector. However, this alignment is often not easy to achieve and is rarely perfect. Furthermore, optical fibers are being increasingly used in coherent lidar system receivers for transporting radiation to achieve architectural elegance. Single mode fibers also require stringent mode matching for efficient light coupling. The detector response characteristics vary with the misalignment of the two pointing vectors. Misalignment can lead to increase in DC current. Also, a lens in front of the detector may exasperate phase front and Poynting vector mismatch. Non-Interaction of Waves, or the NIW property indicates the light beams do not interfere by themselves in the absence of detecting dipoles. In this paper, we will analyze the extent of misalignment on the detector specifications using pointing vectors of mixing beams in light of the NIW property.

Technical support for digital systems technology development. Task order 1: ISP contention analysis and control

NASA Technical Reports Server (NTRS)

Stehle, Roy H.; Ogier, Richard G.

1993-01-01

Alternatives for realizing a packet-based network switch for use on a frequency division multiple access/time division multiplexed (FDMA/TDM) geostationary communication satellite were investigated. Each of the eight downlink beams supports eight directed dwells. The design needed to accommodate multicast packets with very low probability of loss due to contention. Three switch architectures were designed and analyzed. An output-queued, shared bus system yielded a functionally simple system, utilizing a first-in, first-out (FIFO) memory per downlink dwell, but at the expense of a large total memory requirement. A shared memory architecture offered the most efficiency in memory requirements, requiring about half the memory of the shared bus design. The processing requirement for the shared-memory system adds system complexity that may offset the benefits of the smaller memory. An alternative design using a shared memory buffer per downlink beam decreases circuit complexity through a distributed design, and requires at most 1000 packets of memory more than the completely shared memory design. Modifications to the basic packet switch designs were proposed to accommodate circuit-switched traffic, which must be served on a periodic basis with minimal delay. Methods for dynamically controlling the downlink dwell lengths were developed and analyzed. These methods adapt quickly to changing traffic demands, and do not add significant complexity or cost to the satellite and ground station designs. Methods for reducing the memory requirement by not requiring the satellite to store full packets were also proposed and analyzed. In addition, optimal packet and dwell lengths were computed as functions of memory size for the three switch architectures.

Automated Planning of Science Products Based on Nadir Overflights and Alerts for Onboard and Ground Processing

NASA Technical Reports Server (NTRS)

Chien, Steve A.; McLaren, David A.; Rabideau, Gregg R.; Mandl, Daniel; Hengemihle, Jerry

2013-01-01

A set of automated planning algorithms is the current operations baseline approach for the Intelligent Payload Module (IPM) of the proposed Hyper spectral Infrared Imager (HyspIRI) mission. For this operations concept, there are only local (e.g. non-depletable) operations constraints, such as real-time downlink and onboard memory, and the forward sweeping algorithm is optimal for determining which science products should be generated onboard and on ground based on geographical overflights, science priorities, alerts, requests, and onboard and ground processing constraints. This automated planning approach was developed for the HyspIRI IPM concept. The HyspIRI IPM is proposed to use an X-band Direct Broadcast (DB) capability that would enable data to be delivered to ground stations virtually as it is acquired. However, the HyspIRI VSWIR and TIR instruments will produce approximately 1 Gbps data, while the DB capability is 15 Mbps for a approx. =60X oversubscription. In order to address this mismatch, this innovation determines which data to downlink based on both the type of surface the spacecraft is overflying, and the onboard processing of data to detect events. For example, when the spacecraft is overflying Polar Regions, it might downlink a snow/ice product. Additionally, the onboard software will search for thermal signatures indicative of a volcanic event or wild fire and downlink summary information (extent, spectra) when detected, thereby reducing data volume. The planning system described above automatically generated the IPM mission plan based on requested products, the overflight regions, and available resources.

Composite Faces Are Not (Necessarily) Processed Coactively: A Test Using Systems Factorial Technology and Logical-Rule Models

ERIC Educational Resources Information Center

Cheng, Xue Jun; McCarthy, Callum J.; Wang, Tony S. L.; Palmeri, Thomas J.; Little, Daniel R.

2018-01-01

Upright faces are thought to be processed more holistically than inverted faces. In the widely used composite face paradigm, holistic processing is inferred from interference in recognition performance from a to-be-ignored face half for upright and aligned faces compared with inverted or misaligned faces. We sought to characterize the nature of…

Achromatic shearing phase sensor for generating images indicative of measure(s) of alignment between segments of a segmented telescope's mirrors

NASA Technical Reports Server (NTRS)

Stahl, H. Philip (Inventor); Walker, Chanda Bartlett (Inventor)

2006-01-01

An achromatic shearing phase sensor generates an image indicative of at least one measure of alignment between two segments of a segmented telescope's mirrors. An optical grating receives at least a portion of irradiance originating at the segmented telescope in the form of a collimated beam and the collimated beam into a plurality of diffraction orders. Focusing optics separate and focus the diffraction orders. Filtering optics then filter the diffraction orders to generate a resultant set of diffraction orders that are modified. Imaging optics combine portions of the resultant set of diffraction orders to generate an interference pattern that is ultimately imaged by an imager.

A sounding rocket program in extreme and far ultraviolet interferometry

NASA Technical Reports Server (NTRS)

Chakrabarti, S.

1994-01-01

A self-compensating, all reflection interferometric (SCARI) spectrometer was developed that can provide high resolution measurements of spectral features at any wavelength. Several mechanical components were developed that aid the instrument's performance at the short wavelength range. Examples include an optical bench and modular removable precision mechanisms for alignment. Upon alignment and lock down of the interferometer with the latter, the device is removed to minimize weight. A ray-trace code was developed to simulate the instrument's performance. Interference patterns were obtained at the shortest wavelength: the hydrogen Lyman alpha (1216 A). A laboratory instrument was developed that will be flown aboard a Black Brant sounding rocket to study the very local interstellar medium.

Research on the method of precise alignment technology of atmospheric laser communication

NASA Astrophysics Data System (ADS)

Chen, Wen-jian; Gao, Wei; Duan, Yuan-yuan; Ma, Shi-wei; Chen, Jian

2016-10-01

Atmosphere laser communication takes advantage of laser as the carrier transmitting the voice, data, and image information in the atmosphere. Because of its high reliability, strong anti-interference ability, the advantages of easy installation, it has great potential and development space in the communications field. In the process of establish communication, the capture, targeting and tracking of the communication signal is the key technology. This paper introduce a method of targeting the signal spot in the process of atmosphere laser communication, which through the way of making analog signal addition and subtraction directly and normalized to obtain the target azimuth information to drive the servo system to achieve precise alignment of tracking.

A Coarse Alignment Method Based on Digital Filters and Reconstructed Observation Vectors

PubMed Central

Xu, Xiang; Xu, Xiaosu; Zhang, Tao; Li, Yao; Wang, Zhicheng

2017-01-01

In this paper, a coarse alignment method based on apparent gravitational motion is proposed. Due to the interference of the complex situations, the true observation vectors, which are calculated by the apparent gravity, are contaminated. The sources of the interference are analyzed in detail, and then a low-pass digital filter is designed in this paper for eliminating the high-frequency noise of the measurement observation vectors. To extract the effective observation vectors from the inertial sensors’ outputs, a parameter recognition and vector reconstruction method are designed, where an adaptive Kalman filter is employed to estimate the unknown parameters. Furthermore, a robust filter, which is based on Huber’s M-estimation theory, is developed for addressing the outliers of the measurement observation vectors due to the maneuver of the vehicle. A comprehensive experiment, which contains a simulation test and physical test, is designed to verify the performance of the proposed method, and the results show that the proposed method is equivalent to the popular apparent velocity method in swaying mode, but it is superior to the current methods while in moving mode when the strapdown inertial navigation system (SINS) is under entirely self-contained conditions. PMID:28353682

Software for Displaying Data from Planetary Rovers

NASA Technical Reports Server (NTRS)

Powell, Mark; Backers, Paul; Norris, Jeffrey; Vona, Marsette; Steinke, Robert

2003-01-01

Science Activity Planner (SAP) DownlinkBrowser is a computer program that assists in the visualization of processed telemetric data [principally images, image cubes (that is, multispectral images), and spectra] that have been transmitted to Earth from exploratory robotic vehicles (rovers) on remote planets. It is undergoing adaptation to (1) the Field Integrated Design and Operations (FIDO) rover (a prototype Mars-exploration rover operated on Earth as a test bed) and (2) the Mars Exploration Rover (MER) mission. This program has evolved from its predecessor - the Web Interface for Telescience (WITS) software - and surpasses WITS in the processing, organization, and plotting of data. SAP DownlinkBrowser creates Extensible Markup Language (XML) files that organize data files, on the basis of content, into a sortable, searchable product database, without the overhead of a relational database. The data-display components of SAP DownlinkBrowser (descriptively named ImageView, 3DView, OrbitalView, PanoramaView, ImageCubeView, and SpectrumView) are designed to run in a memory footprint of at least 256MB on computers that utilize the Windows, Linux, and Solaris operating systems.

Color coded multiple access scheme for bidirectional multiuser visible light communications in smart home technologies

NASA Astrophysics Data System (ADS)

Tiwari, Samrat Vikramaditya; Sewaiwar, Atul; Chung, Yeon-Ho

2015-10-01

In optical wireless communications, multiple channel transmission is an attractive solution to enhancing capacity and system performance. A new modulation scheme called color coded multiple access (CCMA) for bidirectional multiuser visible light communications (VLC) is presented for smart home applications. The proposed scheme uses red, green and blue (RGB) light emitting diodes (LED) for downlink and phosphor based white LED (P-LED) for uplink to establish a bidirectional VLC and also employs orthogonal codes to support multiple users and devices. The downlink transmission for data user devices and smart home devices is provided using red and green colors from the RGB LEDs, respectively, while uplink transmission from both types of devices is performed using the blue color from P-LEDs. Simulations are conducted to verify the performance of the proposed scheme. It is found that the proposed bidirectional multiuser scheme is efficient in terms of data rate and performance. In addition, since the proposed scheme uses RGB signals for downlink data transmission, it provides flicker-free illumination that would lend itself to multiuser VLC system for smart home applications.

Onboard Classification of Hyperspectral Data on the Earth Observing One Mission

NASA Technical Reports Server (NTRS)

Chien, Steve; Tran, Daniel; Schaffer, Steve; Rabideau, Gregg; Davies, Ashley Gerard; Doggett, Thomas; Greeley, Ronald; Ip, Felipe; Baker, Victor; Doubleday, Joshua;

Optimum satellite relay positions with application to a TDRS-1 Indian Ocean relay

NASA Technical Reports Server (NTRS)

Jackson, A. H.; Christopher, P.

1994-01-01

An Indian Ocean satellite relay is examined. The relay satellite position is optimized by minimizing the sum of downlink and satellite to satellite link losses. Osculating orbital elements are used for fast intensive orbital computation. Integrated Van Vleck gaseous attenuation and a Crane rain model are used for downlink attenuation. Circular polarization losses on the satellite to satellite link are found dynamically. Space to ground link antenna pointing losses are included as a function of yaw ans spacecraft limits. Relay satellite positions between 90 to 100 degrees East are found attractive for further study.

Compatibility of booster seats and vehicles in the U.S. market.

PubMed

Bing, Julie A; Agnew, Amanda M; Bolte, John H

2018-05-19

The objective of this study was to analyze booster and rear vehicle seat dimensions to identify the most frequent compatibility problems. Measurements were collected from 40 high-back and backless boosters and 95 left rear and center rear row seating positions in 50 modern vehicles. Dimensions were compared for 3,800 booster/vehicle seat combinations. For validation and estimation of tolerance and correction factors, 72 booster installations were physically completed and compared with measurement-based compatibility predictions. Dimensions were also compared to the International Organization for Standardization (ISO) volumetric envelopes of forward-facing child restraints and boosters. Seat belt buckles in outboard positions accommodated the width of boosters better than center positions (success rates of 85.4 and 34.7%, respectively). Adequate head restraint clearance occurred in 71.9 to 77.2% of combinations, depending on the booster's head support setting. Booster recline angles aligned properly with vehicle seat cushion angles in 71.5% of combinations. In cases of poor angle alignment, booster angles were more obtuse than the vehicle seat angles 97.7% of the time. Head restraint interference exacerbated angle alignment issues. Data indicate success rates above 90% for boosters being fully supported by the length of the seat cushion and for adequate height clearance with the vehicle roofline. Comparison to ISO envelopes indicates that most boosters on the U.S. market are taller and angled more obtusely than ISO target envelopes. This study quantifies some of the common interferences between boosters and vehicles that may complicate booster usage. Data are useful for design and to prioritize specific problem areas.

2.4-3.2 GHz robust self-injecting injection-locked phase-locked loop

NASA Astrophysics Data System (ADS)

Yang, Jincheng; Zhang, Zhao; Qi, Nan; Liu, Liyuan; Liu, Jian; Wu, Nanjian

2018-04-01

In this paper, we propose a robust self-injecting injection-locked phase-locked loop (SI-ILPLL). It adopts a phase alignment loop (PAL) based on a subsampling phase frequency detector to align the phase between the injected pulse and the voltage-controlled oscillator (VCO) output. With the proposed phase frequency detector, the PAL performs phase alignment and the pulse generator can self-inject pulses into the VCO for injection locking. The subsampling phase detection and self-injection locking techniques can suppress the phase noise of the SI-ILPLL. The SI-ILPLL shows excellent robustness to environmental interference. The SI-ILPLL is implemented in 65 nm CMOS technology. It occupies an active area of 0.7 mm2. The measured root-mean-square (RMS) jitters at 3.2 GHz output without and with injection locking are 216 and 131 fs, respectively. When the supply voltage varies from 1.17 to 1.23 V and the temperature varies from 0 to 80 °C, the maximum jitter variation of all the output frequencies is less than 50 fs. The measured results demonstrate that even when a large interference appears at the supply voltage and unlocks the SI-ILPLL, the SI-ILPLL can self-recover its injection-locked state rapidly after the disturbance disappears, whereas the conventional ILPLL cannot self-recover its locked state after losing it. The power consumption of the SI-ILPLL is 7.4 mW under a 1.2 V supply voltage. The SI-ILPLL achieves a figure of merit (FOM) of -249 dB.

Rapid learning of magnetic compass direction by C57BL/6 mice in a 4-armed 'plus' water maze.

PubMed

Phillips, John B; Youmans, Paul W; Muheim, Rachel; Sloan, Kelly A; Landler, Lukas; Painter, Michael S; Anderson, Christopher R

2013-01-01

Magnetoreception has been demonstrated in all five vertebrate classes. In rodents, nest building experiments have shown the use of magnetic cues by two families of molerats, Siberian hamsters and C57BL/6 mice. However, assays widely used to study rodent spatial cognition (e.g. water maze, radial arm maze) have failed to provide evidence for the use of magnetic cues. Here we show that C57BL/6 mice can learn the magnetic direction of a submerged platform in a 4-armed (plus) water maze. Naïve mice were given two brief training trials. In each trial, a mouse was confined to one arm of the maze with the submerged platform at the outer end in a predetermined alignment relative to magnetic north. Between trials, the training arm and magnetic field were rotated by 180(°) so that the mouse had to swim in the same magnetic direction to reach the submerged platform. The directional preference of each mouse was tested once in one of four magnetic field alignments by releasing it at the center of the maze with access to all four arms. Equal numbers of responses were obtained from mice tested in the four symmetrical magnetic field alignments. Findings show that two training trials are sufficient for mice to learn the magnetic direction of the submerged platform in a plus water maze. The success of these experiments may be explained by: (1) absence of alternative directional cues (2), rotation of magnetic field alignment, and (3) electromagnetic shielding to minimize radio frequency interference that has been shown to interfere with magnetic compass orientation of birds. These findings confirm that mice have a well-developed magnetic compass, and give further impetus to the question of whether epigeic rodents (e.g., mice and rats) have a photoreceptor-based magnetic compass similar to that found in amphibians and migratory birds.

Rapid Learning of Magnetic Compass Direction by C57BL/6 Mice in a 4-Armed ‘Plus’ Water Maze

PubMed Central

Phillips, John B.; Youmans, Paul W.; Muheim, Rachel; Sloan, Kelly A.; Landler, Lukas; Painter, Michael S.; Anderson, Christopher R.

2013-01-01

Magnetoreception has been demonstrated in all five vertebrate classes. In rodents, nest building experiments have shown the use of magnetic cues by two families of molerats, Siberian hamsters and C57BL/6 mice. However, assays widely used to study rodent spatial cognition (e.g. water maze, radial arm maze) have failed to provide evidence for the use of magnetic cues. Here we show that C57BL/6 mice can learn the magnetic direction of a submerged platform in a 4-armed (plus) water maze. Naïve mice were given two brief training trials. In each trial, a mouse was confined to one arm of the maze with the submerged platform at the outer end in a predetermined alignment relative to magnetic north. Between trials, the training arm and magnetic field were rotated by 180° so that the mouse had to swim in the same magnetic direction to reach the submerged platform. The directional preference of each mouse was tested once in one of four magnetic field alignments by releasing it at the center of the maze with access to all four arms. Equal numbers of responses were obtained from mice tested in the four symmetrical magnetic field alignments. Findings show that two training trials are sufficient for mice to learn the magnetic direction of the submerged platform in a plus water maze. The success of these experiments may be explained by: (1) absence of alternative directional cues (2), rotation of magnetic field alignment, and (3) electromagnetic shielding to minimize radio frequency interference that has been shown to interfere with magnetic compass orientation of birds. These findings confirm that mice have a well-developed magnetic compass, and give further impetus to the question of whether epigeic rodents (e.g., mice and rats) have a photoreceptor-based magnetic compass similar to that found in amphibians and migratory birds. PMID:24023673

Scanning laser reflection tool for alignment and period measurement of critical-angle transmission gratings

NASA Astrophysics Data System (ADS)

Song, Jungki; Heilmann, Ralf K.; Bruccoleri, Alexander R.; Hertz, Edward; Schatternburg, Mark L.

2017-08-01

We report progress toward developing a scanning laser reflection (LR) tool for alignment and period measurement of critical-angle transmission (CAT) gratings. It operates on a similar measurement principle as a tool built in 1994 which characterized period variations of grating facets for the Chandra X-ray Observatory. A specularly reflected beam and a first-order diffracted beam were used to record local period variations, surface slope variations, and grating line orientation. In this work, a normal-incidence beam was added to measure slope variations (instead of the angled-incidence beam). Since normal incidence reflection is not coupled with surface height change, it enables measurement of slope variations more accurately and, along with the angled-incidence beam, helps to reconstruct the surface figure (or tilt) map. The measurement capability of in-grating period variations was demonstrated by measuring test reflection grating (RG) samples that show only intrinsic period variations of the interference lithography process. Experimental demonstration for angular alignment of CAT gratings is also presented along with a custom-designed grating alignment assembly (GAA) testbed. All three angles were aligned to satisfy requirements for the proposed Arcus mission. The final measurement of roll misalignment agrees with the roll measurements performed at the PANTER x-ray test facility.

Acoustic Nondestructive Evaluation of Aircraft Paneling Using Piezoelectric Sensors

DTIC Science & Technology

2012-12-01

Electromagnetic Materials Team of the U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Clinical Trials Monitoring Branch, for...connected to this clip. This electrical connection ensures single-point grounding, which has been implemented to avoid electromagnetic interference...waveform of each sensor features an electromagnetic pick-up signature that is aligned with the transduced signal but phase shifted by 180. We know to

Science Planning and Orbit Classification for Solar Probe Plus

NASA Astrophysics Data System (ADS)

Kusterer, M. B.; Fox, N. J.; Rodgers, D. J.; Turner, F. S.

2016-12-01

There are a number of challenges for the Science Planning Team (SPT) of the Solar Probe Plus (SPP) Mission. Since SPP is using a decoupled payload operations approach, tight coordination between the mission operations and payload teams will be required. The payload teams must manage the volume of data that they write to the spacecraft solid-state recorders (SSR) for their individual instruments for downlink to the ground. Making this process more difficult, the geometry of the celestial bodies and the spacecraft during some of the SPP mission orbits cause limited uplink and downlink opportunities. The payload teams will also be required to coordinate power on opportunities, command uplink opportunities, and data transfers from instrument memory to the spacecraft SSR with the operation team. The SPT also intend to coordinate observations with other spacecraft and ground based systems. To solve these challenges, detailed orbit activity planning is required in advance for each orbit. An orbit planning process is being created to facilitate the coordination of spacecraft and payload activities for each orbit. An interactive Science Planning Tool is being designed to integrate the payload data volume and priority allocations, spacecraft ephemeris, attitude, downlink and uplink schedules, spacecraft and payload activities, and other spacecraft ephemeris. It will be used during science planning to select the instrument data priorities and data volumes that satisfy the orbit data volume constraints and power on, command uplink and data transfer time periods. To aid in the initial stages of science planning we have created an orbit classification scheme based on downlink availability and significant science events. Different types of challenges arise in the management of science data driven by orbital geometry and operational constraints, and this scheme attempts to identify the patterns that emerge.

High Capacity Communications From Martian Distances. Part 1; Spacecraft Link Design Analysis

NASA Technical Reports Server (NTRS)

Vyas, Hemali N.; Schuchman, Leonard; Orr, Richard; Williams, Wallace Dan; Collins, Michael; Noreen, Gary

2006-01-01

High capacity space communications has been a desire for Human Exploration and Science missions. Current Mars missions operate at data rates of 120 kbps for telemetry downlink and it is desirable to study high rate communication links in the range of 100 Mbps to 1 Gbps data rates from Martian distances. This paper will present some assumed scenarios along with link design assumptions and link analysis for high capacity communications from Mars. The paper will focus on RF subsystems namely antenna and power for the downlink communication from a relay orbiter at Mars. The relay orbiter will communicate with the low orbit spacecrafts at Mars or any Martian surface elements such as robots, and relay the data back to the ground networks on Earth. The study will dive into the spacecraft downlink system design and communication link analysis between the relay orbiter and ground network on Earth for data rates ranging from 100 Mbps to 1 Gbps based on the assumed scenarios and link assumptions. With high rate links at larger distances, there will be a significant impact on the antenna and power requirements and the link design will make an attempt to minimize the mass of the RF subsystem on the spacecraft. The results of this study will be presented for three data rates 1 Gbps, 500 Mbps and 100 Mbps at maximum Mars to Earth distance of 2.67AU. The design will use a Ka-band downlink with 90% link availability, along with various ground network G/T assumptions and possible bandwidth efficient modulations. The paper will conclude with what types of high rate communication links are feasible from Martian distances and also identify a range of requirements for antenna and power technologies for these high capacity communications from Mars.

A COTS-Based Attitude Dependent Contact Scheduling System

NASA Technical Reports Server (NTRS)

DeGumbia, Jonathan D.; Stezelberger, Shane T.; Woodard, Mark

2006-01-01

The mission architecture of the Gamma-ray Large Area Space Telescope (GLAST) requires a sophisticated ground system component for scheduling the downlink of science data. Contacts between the ````````````````` satellite and the Tracking and Data Relay Satellite System (TDRSS) are restricted by the limited field-of-view of the science data downlink antenna. In addition, contacts must be scheduled when permitted by the satellite s complex and non-repeating attitude profile. Complicating the matter further, the long lead-time required to schedule TDRSS services, combined with the short duration of the downlink contact opportunities, mandates accurate GLAST orbit and attitude modeling. These circumstances require the development of a scheduling system that is capable of predictively and accurately modeling not only the orbital position of GLAST but also its attitude. This paper details the methods used in the design of a Commercial Off The Shelf (COTS)-based attitude-dependent. TDRSS contact Scheduling system that meets the unique scheduling requirements of the GLAST mission, and it suggests a COTS-based scheduling approach to support future missions. The scheduling system applies filtering and smoothing algorithms to telemetered GPS data to produce high-accuracy predictive GLAST orbit ephemerides. Next, bus pointing commands from the GLAST Science Support Center are used to model the complexities of the two dynamic science gathering attitude modes. Attitude-dependent view periods are then generated between GLAST and each of the supporting TDRSs. Numerous scheduling constraints are then applied to account for various mission specific resource limitations. Next, an optimization engine is used to produce an optimized TDRSS contact schedule request which is sent to TDRSS scheduling for confirmation. Lastly, the confirmed TDRSS contact schedule is rectified with an updated ephemeris and adjusted bus pointing commands to produce a final science downlink contact schedule.

Engineering a Live UHD Program from the International Space Station

NASA Technical Reports Server (NTRS)

Grubbs, Rodney; George, Sandy

2017-01-01

The first-ever live downlink of Ultra-High Definition (UHD) video from the International Space Station (ISS) was the highlight of a “Super Session” at the National Association of Broadcasters (NAB) Show in April 2017. Ultra-High Definition is four times the resolution of “full HD” or “1080P” video. Also referred to as “4K”, the Ultra-High Definition video downlink from the ISS all the way to the Las Vegas Convention Center required considerable planning, pushed the limits of conventional video distribution from a space-craft, and was the first use of High Efficiency Video Coding (HEVC) from a space-craft. The live event at NAB will serve as a pathfinder for more routine downlinks of UHD as well as use of HEVC for conventional HD downlinks to save bandwidth. A similar demonstration was conducted in 2006 with the Discovery Channel to demonstrate the ability to stream HDTV from the ISS. This paper will describe the overall work flow and routing of the UHD video, how audio was synchronized even though the video and audio were received many seconds apart from each other, and how the demonstration paves the way for not only more efficient video distribution from the ISS, but also serves as a pathfinder for more complex video distribution from deep space. The paper will also describe how a “live” event was staged when the UHD video coming from the ISS had a latency of 10+ seconds. In addition, the paper will touch on the unique collaboration between the inherently governmental aspects of the ISS, commercial partners Amazon and Elemental, and the National Association of Broadcasters.

MPI investigation for 40G NRZ link with low-RL cable assemblies

NASA Astrophysics Data System (ADS)

Satake, Toshiaki; Berdinskikh, Tatiana; Thongdaeng, Rutsuda; Faysanyo, Pitak; Gurreri, Michael

2017-01-01

Bit Error Ratio (BER) dependence on received power was studied for 40Gb/s NRZ short optical fiber transmission, including a series of four low return loss (RL 21dB) and low insertion loss (IL 0.1dB) connections. The calculated power penalty (PP) was 0.15dB for BER 10-11. Although the fiber length was within DFB laser's coherent length of 100m and the multi path interference (MPI) value was 34.3dB, no PP of BER was observed. There was no PP due to low MPI probably because the polarization of the signal pulses were not aligned for optical interference, indicating that NRZ systems have a high resistance to MPI.

Fiber-optic polarization diversity detection for rotary probe optical coherence tomography.

PubMed

Lee, Anthony M D; Pahlevaninezhad, Hamid; Yang, Victor X D; Lam, Stephen; MacAulay, Calum; Lane, Pierre

2014-06-15

We report a polarization diversity detection scheme for optical coherence tomography with a new, custom, miniaturized fiber coupler with single mode (SM) fiber inputs and polarization maintaining (PM) fiber outputs. The SM fiber inputs obviate matching the optical lengths of the X and Y OCT polarization channels prior to interference and the PM fiber outputs ensure defined X and Y axes after interference. Advantages for this scheme include easier alignment, lower cost, and easier miniaturization compared to designs with free-space bulk optical components. We demonstrate the utility of the detection system to mitigate the effects of rapidly changing polarization states when imaging with rotating fiber optic probes in Intralipid suspension and during in vivo imaging of human airways.

Integrating free-space optical communication links with existing WiFi (WiFO) network

NASA Astrophysics Data System (ADS)

Liverman, S.; Wang, Q.; Chu, Y.; Duong, T.; Nguyen-Huu, D.; Wang, S.; Nguyen, T.; Wang, A. X.

2016-02-01

Recently, free-space optical (FSO) systems have generated great interest due to their large bandwidth potential and a line-of-sight physical layer of protection. In this paper, we propose WiFO, a novel hybrid system, FSO downlink and WiFi uplink, which will integrate currently available WiFi infrastructure with inexpensive infrared light emitting diodes. This system takes full advantage of the mobility inherent in WiFi networks while increasing the downlink bandwidth available to each end user. We report the results of our preliminary investigation that show the capabilities of our prototype design in terms of bandwidth, bit error rates, delays and transmission distances.

Results From Phase-1 and Phase-2 GOLD Experiments

NASA Technical Reports Server (NTRS)

Wilson, K.; Jeganathan, M.; Lesh, J. R.; James, J.; Xu, G.

1997-01-01

The Ground/Orbiter Lasercomm Demonstration conducted between the Japanese Engineering Test Satellite (ETS-VI) and the ground station at JPL's Table Mountain Facility, Wrightwood, California, was the rst ground-to-space two-way optical communications experiment. Experiment objectives included validating the performance predictions of the optical link. Atmospheric attenuation and seeing measurements were made during the experiment, and data were analyzed. Downlink telemetry data recovered over the course of the experiment provided information on in-orbit performance of the ETS-VI's laser communications equipment. Biterror rates as low as 10 4 were measured on the uplink and 10 5 on the downlink. Measured signal powers agreed well with theoretical predictions.

Proposed Solar Probe telecommunications system concept

NASA Astrophysics Data System (ADS)

Kellogg, K.; Devereaux, A.; Vacchione, J.; Kapoor, V.; Crist, R.

1992-01-01

A proposed telecommunications system concept for NASA's Solar Probe mission is described. Key system requirements include 70 kbps data rate at perihelion and operation at X-band (uplink/downlink) and Ka-band (downlink). A design control table is presented to demonstrate design compliance with telecommunication needs. The Ka-band feed is to be a hexagonal array of 37 active elements, each containing 1/4W HEMT amplifiers. The array is located at the Cassegrain point of a 0.75-m reflector. When compared to the TWTA-based system, the Ka-band active array feed provides advantages of reduced mass, increased dc power efficiency, enhanced reliability, graceful degradation, and reduced volume requirements.

Onboard Data Compression of Synthetic Aperture Radar Data: Status and Prospects

NASA Technical Reports Server (NTRS)

Klimesh, Matthew A.; Moision, Bruce

2008-01-01

Synthetic aperture radar (SAR) instruments on spacecraft are capable of producing huge quantities of data. Onboard lossy data compression is commonly used to reduce the burden on the communication link. In this paper an overview is given of various SAR data compression techniques, along with an assessment of how much improvement is possible (and practical) and how to approach the problem of obtaining it. Synthetic aperture radar (SAR) instruments on spacecraft are capable of acquiring huge quantities of data. As a result, the available downlink rate and onboard storage capacity can be limiting factors in mission design for spacecraft with SAR instruments. This is true both for Earth-orbiting missions and missions to more distant targets such as Venus, Titan, and Europa. (Of course for missions beyond Earth orbit downlink rates are much lower and thus potentially much more limiting.) Typically spacecraft with SAR instruments use some form of data compression in order to reduce the storage size and/or downlink rate necessary to accommodate the SAR data. Our aim here is to give an overview of SAR data compression strategies that have been considered, and to assess the prospects for additional improvements.

The Future of the Deep Space Network: Technology Development for K2-Band Deep Space Communications

NASA Technical Reports Server (NTRS)

Bhanji, Alaudin M.

1999-01-01

Projections indicate that in the future the number of NASA's robotic deep space missions is likely to increase significantly. A launch rate of up to 4-6 launches per year is projected with up to 25 simultaneous missions active [I]. Future high resolution mapping missions to other planetary bodies as well as other experiments are likely to require increased downlink capacity. These future deep space communications requirements will, according to baseline loading analysis, exceed the capacity of NASA's Deep Space Network in its present form. There are essentially two approaches for increasing the channel capacity of the Deep Space Network. Given the near-optimum performance of the network at the two deep space communications bands, S-Band (uplink 2.025-2.120 GHz, downlink 2.2-2.3 GHz), and X-Band (uplink 7.145-7.19 GHz, downlink 8.48.5 GHz), additional improvements bring only marginal return for the investment. Thus the only way to increase channel capacity is simply to construct more antennas, receivers, transmitters and other hardware. This approach is relatively low-risk but involves increasing both the number of assets in the network and operational costs.

Investigation on adaptive optics performance from propagation channel characterization with the small optical transponder

NASA Astrophysics Data System (ADS)

Petit, Cyril; Védrenne, Nicolas; Velluet, Marie Therese; Michau, Vincent; Artaud, Geraldine; Samain, Etienne; Toyoshima, Morio

2016-11-01

In order to address the high throughput requested for both downlink and uplink satellite to ground laser links, adaptive optics (AO) has become a key technology. While maturing, application of this technology for satellite to ground telecommunication, however, faces difficulties, such as higher bandwidth and optimal operation for a wide variety of atmospheric conditions (daytime and nighttime) with potentially low elevations that might severely affect wavefront sensing because of scintillation. To address these specificities, an accurate understanding of the origin of the perturbations is required, as well as operational validation of AO on real laser links. We report here on a low Earth orbiting (LEO) microsatellite to ground downlink with AO correction. We discuss propagation channel characterization based on Shack-Hartmann wavefront sensor (WFS) measurements. Fine modeling of the propagation channel is proposed based on multi-Gaussian model of turbulence profile. This model is then used to estimate the AO performance and validate the experimental results. While AO performance is limited by the experimental set-up, it proves to comply with expected performance and further interesting information on propagation channel is extracted. These results shall help dimensioning and operating AO systems for LEO to ground downlinks.

OCDMA Over WDM PON—Solution Path to Gigabit-Symmetric FTTH

NASA Astrophysics Data System (ADS)

Kitayama, Ken-Ichi; Wang, Xu; Wada, Naoya

2006-04-01

It will be revealed that a myth of deploying low bit-rate uplink fiber-to-the-home (FTTH) services while providing a high bit-rate downlink is wrong. Therefore, for the future broadband FTTH services, the focus should be on the capability to provide gigabit-or even multigigabits-per-second both in up-and downlinks, namely gigabit symmetric systems. Optical code-division multiple access (OCDMA) now deserves a revisit as a powerful alternative to time-division multiple access and wavelength-division multiple (WDM) access in FTTH systems. In this paper, the authors will first highlight the OCDMA systems. The system architecture and its operation principle, code design, optical en/decoding, using a long superstructured fiber Bragg grating (SSFBG) en/decoder, and its system performance will be described. Next, an OCDMA over WDM passive optical network (PON) as a solution for the gigabit-symmetric FTTH systems will be proposed. The system architecture and the WDM interchannel crosstalk will be studied. It will be shown that by taking advantage of reflection spectrum notches of the SSFBG en/decoder, the WDM interchannel crosstalk can be suppressed and can enable OCDMA over WDM PON to simultaneously provide multigigabit-per-second up-and downlinks to a large number of users.

FDD Massive MIMO Channel Estimation With Arbitrary 2D-Array Geometry

NASA Astrophysics Data System (ADS)

Dai, Jisheng; Liu, An; Lau, Vincent K. N.

2018-05-01

This paper addresses the problem of downlink channel estimation in frequency-division duplexing (FDD) massive multiple-input multiple-output (MIMO) systems. The existing methods usually exploit hidden sparsity under a discrete Fourier transform (DFT) basis to estimate the cdownlink channel. However, there are at least two shortcomings of these DFT-based methods: 1) they are applicable to uniform linear arrays (ULAs) only, since the DFT basis requires a special structure of ULAs, and 2) they always suffer from a performance loss due to the leakage of energy over some DFT bins. To deal with the above shortcomings, we introduce an off-grid model for downlink channel sparse representation with arbitrary 2D-array antenna geometry, and propose an efficient sparse Bayesian learning (SBL) approach for the sparse channel recovery and off-grid refinement. The main idea of the proposed off-grid method is to consider the sampled grid points as adjustable parameters. Utilizing an in-exact block majorization-minimization (MM) algorithm, the grid points are refined iteratively to minimize the off-grid gap. Finally, we further extend the solution to uplink-aided channel estimation by exploiting the angular reciprocity between downlink and uplink channels, which brings enhanced recovery performance.

On the Problem of Bandwidth Partitioning in FDD Block-Fading Single-User MISO/SIMO Systems

NASA Astrophysics Data System (ADS)

Ivrlač, Michel T.; Nossek, Josef A.

2008-12-01

We report on our research activity on the problem of how to optimally partition the available bandwidth of frequency division duplex, multi-input single-output communication systems, into subbands for the uplink, the downlink, and the feedback. In the downlink, the transmitter applies coherent beamforming based on quantized channel information which is obtained by feedback from the receiver. As feedback takes away resources from the uplink, which could otherwise be used to transfer payload data, it is highly desirable to reserve the "right" amount of uplink resources for the feedback. Under the assumption of random vector quantization, and a frequency flat, independent and identically distributed block-fading channel, we derive closed-form expressions for both the feedback quantization and bandwidth partitioning which jointly maximize the sum of the average payload data rates of the downlink and the uplink. While we do introduce some approximations to facilitate mathematical tractability, the analytical solution is asymptotically exact as the number of antennas approaches infinity, while for systems with few antennas, it turns out to be a fairly accurate approximation. In this way, the obtained results are meaningful for practical communication systems, which usually can only employ a few antennas.

Optimized scheduling technique of null subcarriers for peak power control in 3GPP LTE downlink.

PubMed

Cho, Soobum; Park, Sang Kyu

2014-01-01

Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system.

A laboratory system for the investigation of rain fade compensation techniques for Ka-band satellites

NASA Technical Reports Server (NTRS)

Svoboda, James S.; Kachmar, Brian A.

1993-01-01

The design and performance of a rain fade simulation/counteraction system on a laboratory simulated 30/20 GHz, time division multiple access (TDMA) satellite communications testbed is evaluated. Severe rain attenuation of electromagnetic radiation at 30/20 GHz occurs due to the carrier wavelength approaching the water droplet size. Rain in the downlink path lowers the signal power present at the receiver, resulting in a higher number of bit errors induced in the digital ground terminal. The laboratory simulation performed at NASA Lewis Research Center uses a programmable PIN diode attenuator to simulate 20 GHz satellite downlink geographic rain fade profiles. A computer based network control system monitors the downlink power and informs the network of any power threshold violations, which then prompts the network to issue commands that temporarily increase the gain of the satellite based traveling wave tube (TWT) amplifier. After the rain subsides, the network returns the TWT to the normal energy conserving power mode. Bit error rate (BER) data taken at the receiving ground terminal serves as a measure of the severity of rain degradation, and also evaluates the extent to which the network can improve the faded channel.

Spacecraft-spacecraft very long baseline interferometry. Part 1: Error modeling and observable accuracy

NASA Technical Reports Server (NTRS)

Edwards, C. D., Jr.; Border, J. S.

1992-01-01

In Part 1 of this two-part article, an error budget is presented for Earth-based delta differential one-way range (delta DOR) measurements between two spacecraft. Such observations, made between a planetary orbiter (or lander) and another spacecraft approaching that planet, would provide a powerful target-relative angular tracking data type for approach navigation. Accuracies of better than 5 nrad should be possible for a pair of spacecraft with 8.4-GHz downlinks, incorporating 40-MHz DOR tone spacings, while accuracies approaching 1 nrad will be possible if the spacecraft incorporate 32-GHz downlinks with DOR tone spacing on the order of 250 MHz; these accuracies will be available for the last few weeks or months of planetary approach for typical Earth-Mars trajectories. Operational advantages of this data type are discussed, and ground system requirements needed to enable spacecraft-spacecraft delta DOR observations are outlined. This tracking technique could be demonstrated during the final approach phase of the Mars '94 mission, using Mars Observer as the in-orbit reference spacecraft, if the Russian spacecraft includes an 8.4-GHz downlink incorporating DOR tones. Part 2 of this article will present an analysis of predicted targeting accuracy for this scenario.

Optimized Scheduling Technique of Null Subcarriers for Peak Power Control in 3GPP LTE Downlink

PubMed Central

Park, Sang Kyu

2014-01-01

Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system. PMID:24883376

Simplifying operations with an uplink/downlink integration toolkit

NASA Technical Reports Server (NTRS)

Murphy, Susan C.; Miller, Kevin J.; Guerrero, Ana Maria; Joe, Chester; Louie, John J.; Aguilera, Christine

1994-01-01

The Operations Engineering Lab (OEL) at JPL has developed a simple, generic toolkit to integrate the uplink/downlink processes, (often called closing the loop), in JPL's Multimission Ground Data System. This toolkit provides capabilities for integrating telemetry verification points with predicted spacecraft commands and ground events in the Mission Sequence Of Events (SOE) document. In the JPL ground data system, the uplink processing functions and the downlink processing functions are separate subsystems that are not well integrated because of the nature of planetary missions with large one-way light times for spacecraft-to-ground communication. Our new closed-loop monitoring tool allows an analyst or mission controller to view and save uplink commands and ground events with their corresponding downlinked telemetry values regardless of the delay in downlink telemetry and without requiring real-time intervention by the user. An SOE document is a time-ordered list of all the planned ground and spacecraft events, including all commands, sequence loads, ground events, significant mission activities, spacecraft status, and resource allocations. The SOE document is generated by expansion and integration of spacecraft sequence files, ground station allocations, navigation files, and other ground event files. This SOE generation process has been automated within the OEL and includes a graphical, object-oriented SOE editor and real-time viewing tool running under X/Motif. The SOE toolkit was used as the framework for the integrated implementation. The SOE is used by flight engineers to coordinate their operations tasks, serving as a predict data set in ground operations and mission control. The closed-loop SOE toolkit allows simple, automated integration of predicted uplink events with correlated telemetry points in a single SOE document for on-screen viewing and archiving. It automatically interfaces with existing real-time or non real-time sources of information, to display actual values from the telemetry data stream. This toolkit was designed to greatly simplify the user's ability to access and view telemetry data, and also provide a means to view this data in the context of the commands and ground events that are used to interpret it. A closed-loop system can prove especially useful in small missions with limited resources requiring automated monitoring tools. This paper will discuss the toolkit implementation, including design trade-offs and future plans for enhancing the automated capabilities.

Simplifying operations with an uplink/downlink integration toolkit

NASA Astrophysics Data System (ADS)

Murphy, Susan C.; Miller, Kevin J.; Guerrero, Ana Maria; Joe, Chester; Louie, John J.; Aguilera, Christine

1994-11-01

The Operations Engineering Lab (OEL) at JPL has developed a simple, generic toolkit to integrate the uplink/downlink processes, (often called closing the loop), in JPL's Multimission Ground Data System. This toolkit provides capabilities for integrating telemetry verification points with predicted spacecraft commands and ground events in the Mission Sequence Of Events (SOE) document. In the JPL ground data system, the uplink processing functions and the downlink processing functions are separate subsystems that are not well integrated because of the nature of planetary missions with large one-way light times for spacecraft-to-ground communication. Our new closed-loop monitoring tool allows an analyst or mission controller to view and save uplink commands and ground events with their corresponding downlinked telemetry values regardless of the delay in downlink telemetry and without requiring real-time intervention by the user. An SOE document is a time-ordered list of all the planned ground and spacecraft events, including all commands, sequence loads, ground events, significant mission activities, spacecraft status, and resource allocations. The SOE document is generated by expansion and integration of spacecraft sequence files, ground station allocations, navigation files, and other ground event files. This SOE generation process has been automated within the OEL and includes a graphical, object-oriented SOE editor and real-time viewing tool running under X/Motif. The SOE toolkit was used as the framework for the integrated implementation. The SOE is used by flight engineers to coordinate their operations tasks, serving as a predict data set in ground operations and mission control. The closed-loop SOE toolkit allows simple, automated integration of predicted uplink events with correlated telemetry points in a single SOE document for on-screen viewing and archiving. It automatically interfaces with existing real-time or non real-time sources of information, to display actual values from the telemetry data stream. This toolkit was designed to greatly simplify the user's ability to access and view telemetry data, and also provide a means to view this data in the context of the commands and ground events that are used to interpret it. A closed-loop system can prove especially useful in small missions with limited resources requiring automated monitoring tools. This paper will discuss the toolkit implementation, including design trade-offs and future plans for enhancing the automated capabilities.

The SIGMA CubeSat Mission for Space Research and Technology Demonstration

NASA Astrophysics Data System (ADS)

Lee, S.; Lee, J. K.; Lee, H.; Shin, J.; Jeong, S.; Jin, H.; Nam, U. W.; Kim, H.; Lessard, M.; Lee, R.

2016-12-01

The Scientific cubesat with Instrument for Global Magnetic field and rAdiation (SIGMA) is the 3U standard CubeSat measuring the space radiation and magnetic field on a 450 × 720 km sun-synchronous orbit. Its mass is 2.95 kg and the communication system consists of Very High Frequency (VHF) uplink and Ultra High Frequency (UHF) downlink. The SIGMA mission has two academic purposes which are space research and technology demonstration. For the space research, SIGMA has two instruments such as Tissue Equivalent Proportional Counter (TEPC) and a miniaturized fluxgate MAGnetometer (MAG). The TEPC primary instrument measures the Linear Energy Transfer (LET) spectrum and calculates the equivalent dose in the range from 0.3 to 1,000 keV/μm with a single Multi-Channel Analyzer. The secondary is a miniaturized fluxgate magnetometer which have 1 nT resolution with the dynamic range of ±42000 nT. The MAG is deployed by 0.7 m folding boom to avoid CubeSat body's Electromagnetic Interference (EMI). This boom is one of our mechanical technology demonstrations. After launch, we expect that the SIGMA give us new scientific data and technologic verification. This CubeSat is supported by Korean CubeSat contest program.

Ant Colony Optimization Algorithm for Centralized Dynamic Channel Allocation in Multi-Cell OFDMA Systems

NASA Astrophysics Data System (ADS)

Kim, Hyo-Su; Kim, Dong-Hoi

The dynamic channel allocation (DCA) scheme in multi-cell systems causes serious inter-cell interference (ICI) problem to some existing calls when channels for new calls are allocated. Such a problem can be addressed by advanced centralized DCA design that is able to minimize ICI. Thus, in this paper, a centralized DCA is developed for the downlink of multi-cell orthogonal frequency division multiple access (OFDMA) systems with full spectral reuse. However, in practice, as the search space of channel assignment for centralized DCA scheme in multi-cell systems grows exponentially with the increase of the number of required calls, channels, and cells, it becomes an NP-hard problem and is currently too complicated to find an optimum channel allocation. In this paper, we propose an ant colony optimization (ACO) based DCA scheme using a low-complexity ACO algorithm which is a kind of heuristic algorithm in order to solve the aforementioned problem. Simulation results demonstrate significant performance improvements compared to the existing schemes in terms of the grade of service (GoS) performance and the forced termination probability of existing calls without degrading the system performance of the average throughput.

Coverage Extension and Balancing the Transmitted Power of the Moving Relay Node at LTE-A Cellular Network

PubMed Central

Aldhaibani, Jaafar A.; Yahya, Abid; Ahmad, R. Badlishah

2014-01-01

The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user's location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain. PMID:24672378

Coverage extension and balancing the transmitted power of the moving relay node at LTE-A cellular network.

PubMed

Aldhaibani, Jaafar A; Yahya, Abid; Ahmad, R Badlishah

2014-01-01

The poor capacity at cell boundaries is not enough to meet the growing demand and stringent design which required high capacity and throughput irrespective of user's location in the cellular network. In this paper, we propose new schemes for an optimum fixed relay node (RN) placement in LTE-A cellular network to enhance throughput and coverage extension at cell edge region. The proposed approach mitigates interferences between all nodes and ensures optimum utilization with the optimization of transmitted power. Moreover, we proposed a new algorithm to balance the transmitted power of moving relay node (MR) over cell size and providing required SNR and throughput at the users inside vehicle along with reducing the transmitted power consumption by MR. The numerical analysis along with the simulation results indicates that an improvement in capacity for users is 40% increment at downlink transmission from cell capacity. Furthermore, the results revealed that there is saving nearly 75% from transmitted power in MR after using proposed balancing algorithm. ATDI simulator was used to verify the numerical results, which deals with real digital cartographic and standard formats for terrain.

Low-latency fiber-millimeter-wave system for future mobile fronthauling

NASA Astrophysics Data System (ADS)

Tien Dat, Pham; Kanno, Atsushi; Yamamoto, Naokatsu; Kawanishi, Tetsuya

2016-02-01

A seamless combination of fiber and millimeter-wave (MMW) systems can be very attractive for future heterogeneous mobile networks such as 5G because of its flexibility and high bandwidth. Analog mobile signal transmission over seamless fiber-MMW systems is very promising to reduce the latency and the required band-width, and to simplify the systems. However, stable and high-performance seamless systems are indispensable to conserve the quality of the analog signal transmission. In this paper, we present several technologies to develop such seamless fiber-MMW systems. In the downlink direction, a high-performance system can be realized using a high-quality optical MMW signal generator and a self-homodyne MMW signal detector. In the uplink direction, a cascade of radio-on-radio and radio-over-fiber systems using a burst-mode optical amplifier can support bursty radio signal transmission. A full-duplex transmission with negligible interference effects can be realized using frequency multiplexing in the radio link and wavelength-division multiplexing in the optical link. A high-spectral efficiency MMW-over-fiber system using an intermediate frequency-over-fiber system and a high-quality remote delivery of a local oscillator signal is highly desirable to reduce the costs.

Planetary Science Enabled by High Power Ion Propulsion Systems from NASA's Prometheus Program

NASA Astrophysics Data System (ADS)

Cooper, John

2004-11-01

NASA's Prometheus program seeks to develop new generations of spacecraft nuclear-power and ion propulsion systems for applications to future planetary missions. The Science Definition Team for the first mission in the Prometheus series, the Jupiter Icy Moons Orbiter (JIMO), has defined science objectives for in-situ orbital exploration of the icy Galilean moons (Europa, Ganymede, Callisto) and the Jovian magnetosphere along with remote observations of Jupiter's atmosphere and aurorae, the volcanic moon Io, and other elements of the Jovian system. Important to this forum is that JIMO power and propulsion systems will need to be designed to minimize magnetic, radio, neutral gas, and plasma backgrounds that might otherwise interfere with achievement of mission science objectives. Another potential Prometheus mission of high science interest would be an extended tour of primitive bodies in the solar system, including asteroids, Jupiter family comets, Centaurs, and Kuiper Belt Objects (KBO). The final landed phase of this mission might include an active keplerian experiment for detectable (via downlink radio doppler shift) acceleration of a small kilometer-size Centaur or KBO object, likely the satellite of a larger object observable from Earth. This would have obvious application to testing of mitigation techniques for Earth impact hazards.

Evaluation of two glucose meters and interference corrections for screening neonatal hypoglycemia.

PubMed

Wada, Yuka; Nakamura, Tomoo; Kaneshige, Masao; Takahashi, Shigehiro; Fujinaga, Hideshi; Tsukamoto, Keiko; Ito, Yushi; Sago, Haruhiko

2015-08-01

Many neonatal intensive care and maternal units still use self-monitoring of blood glucose (SMBG) devices as a tool to aid diagnosis despite the introduction of point-of-care testing (POCT) devices, which are known to have higher accuracy. We evaluated the performance of two glucose meters, the StatStrip (Nova Biomedical), a POCT device, and the Medisafe Mini (Terumo), an SMBG device, to detect hypoglycemia in neonates. In addition, we evaluated the interference of hematocrit, acetaminophen and ascorbic acid. Whole blood samples were drawn from neonates who were at risk of hypoglycemia and analyzed with the StatStrip and Medisafe Mini. The results were further confirmed with blood gas analyzers ABL825 and BM6050. To evaluate the interference of hematocrit, acetaminophen and ascorbic acid, concentrated solutions of glucose and interfering substances were gravimetrically prepared and analyzed. Among the 222 blood samples analyzed, results from the StatStrip were more closely aligned to those of the ABL825 at all levels of glucose than the Medisafe Mini. StatStrip appears to be unaffected by hematocrit, ascorbic acid or acetaminophen. We recommend its use in neonates in hospital. Further studies are required to identify other interference effects. © 2014 Japan Pediatric Society.

Development of a Grazing Incidence X-Ray Interferometer

NASA Technical Reports Server (NTRS)

Shipley, Ann; Cash, Webster; Osterman, Steve; Joy, Marshall; Carter, James

1999-01-01

A grazing incidence x-ray interferometer design capable of micro-arcsecond level resolution is discussed. This practical design employs a Michelson Stellar interferometer approach to create x-ray interference fringes without the use of Wolter style optics or diffraction crystals. Design solutions accommodating alignment, vibration, and thermal constraints are reviewed. We present the development and demonstration of a working experiment along with tolerance studies, data analysis, and results.

Differences in holistic processing do not explain cultural differences in the recognition of facial expression.

PubMed

Yan, Xiaoqian; Young, Andrew W; Andrews, Timothy J

2017-12-01

The aim of this study was to investigate the causes of the own-race advantage in facial expression perception. In Experiment 1, we investigated Western Caucasian and Chinese participants' perception and categorization of facial expressions of six basic emotions that included two pairs of confusable expressions (fear and surprise; anger and disgust). People were slightly better at identifying facial expressions posed by own-race members (mainly in anger and disgust). In Experiment 2, we asked whether the own-race advantage was due to differences in the holistic processing of facial expressions. Participants viewed composite faces in which the upper part of one expression was combined with the lower part of a different expression. The upper and lower parts of the composite faces were either aligned or misaligned. Both Chinese and Caucasian participants were better at identifying the facial expressions from the misaligned images, showing interference on recognizing the parts of the expressions created by holistic perception of the aligned composite images. However, this interference from holistic processing was equivalent across expressions of own-race and other-race faces in both groups of participants. Whilst the own-race advantage in recognizing facial expressions does seem to reflect the confusability of certain emotions, it cannot be explained by differences in holistic processing.

Angular spectra of the intrinsic galaxy ellipticity field, their observability and their impact on lensing in tomographic surveys

NASA Astrophysics Data System (ADS)

Schäfer, Björn Malte; Merkel, Philipp M.

2017-09-01

This paper describes intrinsic ellipticity correlations between galaxies, their statistical properties, their observability with future surveys and their interference with weak gravitational lensing measurements. Using an angular-momentum-based, quadratic intrinsic alignment model we derive correlation functions of the ellipticity components and project them to yield the four non-zero angular ellipticity spectra C^ɛ _E(ℓ), C^ɛ _B(ℓ), C^ɛ _C(ℓ) and C^ɛ _S(ℓ) in their generalization to tomographic surveys. For a Euclid-like survey, these spectra would have amplitudes smaller than the weak lensing effect on non-linear structures, but would constitute an important systematics. Computing estimation biases for cosmological parameters derived from an alignment-contaminated survey suggests biases of +5σw for the dark energy equation of state parameter w, -20σ _{Ω _m} for the matter density Ωm and -12σ _{σ _8} for the spectrum normalization σ8. Intrinsic alignments yield a signal that is easily observable with a survey similar to Euclid: while not independent, significances for estimates of each of the four spectra reach values of tens of σ if weak lensing and shape noise are considered as noise sources, which suggests relative uncertainties on alignment parameters at the percent level, implying that galaxy alignment mechanisms can be investigated by future surveys.

How does electromagnetic navigation stack up against infrared navigation in minimally invasive total knee arthroplasties?

PubMed

Lionberger, David R; Weise, Jennifer; Ho, David M; Haddad, John L

2008-06-01

Forty-six primary total knee arthroplasties were performed using either an electromagnetic (EM) or infrared (IR) navigation system. In this IRB-approved study, patients were evaluated clinically and for accuracy using spiral computed tomographic imaging and 36-in standing radiographs. Although EM navigation was subject to metal interference, it was not as drastic as line-of-sight interference with IR navigation. Mechanical alignment was ideal in 92.9% of EM and 90.0% of IR cases based on spiral computed tomographic imaging and 100% of EM and 95% of IR cases based on x-ray. Individual measurements of component varus/valgus and sagittal measurements showed EM to be equivalent to IR, with both systems producing subdegree accuracy in 95% of the readings.

An Efficient Downlink Scheduling Strategy Using Normal Graphs for Multiuser MIMO Wireless Systems

NASA Astrophysics Data System (ADS)

Chen, Jung-Chieh; Wu, Cheng-Hsuan; Lee, Yao-Nan; Wen, Chao-Kai

Inspired by the success of the low-density parity-check (LDPC) codes in the field of error-control coding, in this paper we propose transforming the downlink multiuser multiple-input multiple-output scheduling problem into an LDPC-like problem using the normal graph. Based on the normal graph framework, soft information, which indicates the probability that each user will be scheduled to transmit packets at the access point through a specified angle-frequency sub-channel, is exchanged among the local processors to iteratively optimize the multiuser transmission schedule. Computer simulations show that the proposed algorithm can efficiently schedule simultaneous multiuser transmission which then increases the overall channel utilization and reduces the average packet delay.

An AWG-based 10 Gbit/s colorless WDM-PON system using a chirp-managed directly modulated laser

NASA Astrophysics Data System (ADS)

Latif, Abdul; Yu, Chong-xiu; Xin, Xiang-jun; Husain, Aftab; Hussain, Ashiq; Munir, Abid; Khan, Yousaf

2012-09-01

We propose an arrayed waveguide grating (AWG)-based 10 Gbit/s per channel full duplex wavelength division multiplexing passive optical network (WDM-PON). A chirp managed directly modulated laser with return-to-zero (RZ) differential phase shift keying (DPSK) modulation technique is utilized for downlink (DL) direction, and then the downlink signal is re-modulated for the uplink (UL) direction using intensity modulation technique with the data rate of 10 Gbit/s per channel. A successful WDM-PON transmission operation with the data rate of 10 Gbit/s per channel over a distance of 25 km without any optical amplification or dispersion compensation is demonstrated with low power penalty.

Sharing the 620-790 MHz band allocated to terrestrial television with an audio-bandwidth social service satellite system

NASA Technical Reports Server (NTRS)

Smith, E. K.; Reinhart, E. E.

1977-01-01

A study was carried out to identify the optimum uplink and downlink frequencies for audio-bandwidth channels for use by a satellite system distributing social services. The study considered functional-user-need models for five types of social services and identified a general baseline system that is appropriate for most of them. Technical aspects and costs of this system and of the frequency bands that it might use were reviewed, leading to the identification of the 620-790 MHz band as a perferred candidate for both uplink and downlink transmissions for nonmobile applications. The study also led to some ideas as to how to configure the satellite system.

STS-54 crewmembers with DSO 802 & Physics of Toys on OV-105's middeck

NASA Image and Video Library

1993-01-15

STS054-S-022 (15 Jan 1993) --- Casper talks to a TV audience including students during a lengthy "physics of toys" program conducted by all five crewmembers on their third day aboard the Shuttle. Through telephone and TV downlinks, students in four schools around the country participated in a special lesson to discover how specific toys function differently in the classroom compared to those on the Shuttle. Counter clockwise from the left are Helms, Casper, McMonagle, Runco, and Harbaugh. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the autumn. The scene was downlinked at 18:28:04:18 GMT, Jan. 15, 1993.

Iridescent clouds and distorted coronas.

PubMed

Laven, Philip

2017-07-01

Near-forward scattering of sunlight generates coronas and iridescence on clouds. Coronas are caused by diffraction, whereas iridescence is less easily explained. Iridescence often appears as bands of color aligned with the edges of clouds or as apparently random patches of color on clouds. This paper suggests that iridescence is due to interference between light that has been diffracted by a spherical droplet of water and light that has been transmitted through the same droplet.

Atomic alignment effect in the dissociative energy transfer reaction of metal carbonyls (Fe(CO)5, Ni(CO)4) with oriented Ar (3P2, M(J) = 2).

PubMed

Ohoyama, H; Matsuura, Y

2011-10-13

The atomic alignment effect has been studied for the dissociative energy transfer reaction of metal carbonyls (Fe(CO)(5), Ni(CO)(4)) with the oriented Ar ((3)P(2), M(J) = 2). The emission intensity from the excited metal products (Fe*, Ni*) has been measured as a function of the atomic alignment in the collision frame. The selectivity of the atomic orbital alignment of Ar ((3)P(2), M(J) = 2) (rank 2 moment, a(2)) is found to be opposite for the two reaction systems; the Fe(CO)(5) reaction is favorable at the Π configuration (positive a(2)), while the Ni(CO)(4) reaction is favorable at the Σ configuration (negative a(2)). Moreover, a significant spin alignment effect (rank 4 moment, a(4)) is recognized only in the Ni(CO)(4) reaction. The atomic alignment effect turns out to be essentially different between the two reaction systems; the Fe(CO)(5) reaction is controlled by the configuration of the half-filled 3p atomic orbital of Ar ((3)P(2)) in the collision frame (L dependence), whereas the Ni(CO)(4) reaction is controlled by the configuration of the total angular moment J (including spin) of Ar ((3)P(2)) in the collision frame (J dependence). As the origin of J dependence observed only in the Ni(CO)(4) reaction, the correlation (and/or the interference) between two electron exchange processes via the electron rearrangements is proposed.

Producing a Live HDTV Program from Space

NASA Technical Reports Server (NTRS)

Grubbs, Rodney; Fontanot, Carlos; Hames, Kevin

2007-01-01

By the year 2000, NASA had flown HDTV camcorders on three Space Shuttle missions: STS-95, STS-93 and STS-99. All three flights of these camcorders were accomplished with cooperation from the Japanese space agency (then known as NASDA and now known as JAXA). The cameras were large broadcast-standard cameras provided by NASDA and flight certified by both NASA and NASDA. The high-definition video shot during these missions was spectacular. Waiting for the return of the tapes to Earth emphasized the next logical step: finding a way to downlink the HDTV live from space. Both the Space Shuttle and the International Space Station (ISS) programs were interested in live HDTV from space, but neither had the resources to fully fund the technology. Technically, downlinking from the ISS was the most effective approach. Only when the Japanese broadcaster NHK and the Japanese space agency expressed interest in covering a Japanese astronaut's journey to the ISS did the project become possible. Together, JAXA and NHK offered equipment, technology, and funding toward the project. In return, NHK asked for a live HDTV downlink during one of its broadcast programs. NASA and the ISS Program sought a US partner to broadcast a live HDTV program and approached the Discovery Channel. The Discovery Channel had proposed a live HDTV project in response to NASA's previous call for offers. The Discovery Channel agreed to provide addItional resources. With the final partner in place, the project was under way. Engineers in the Avionics Systems Division at NASA's Johnson Space Center (JSC) had already studied the various options for downlinking HDTV from the ISS. They concluded that the easiest way was to compress the HDTV so that the resulting data stream would "look" like a payload data stream. The flight system would consist of a professional HDTV camcorder with live HD-SDI output, an HDTV MPEG-2 encoder, and a packetizer/protocol converter.

Onboard Data Processors for Planetary Ice-Penetrating Sounding Radars

NASA Astrophysics Data System (ADS)

Tan, I. L.; Friesenhahn, R.; Gim, Y.; Wu, X.; Jordan, R.; Wang, C.; Clark, D.; Le, M.; Hand, K. P.; Plaut, J. J.

2011-12-01

Among the many concerns faced by outer planetary missions, science data storage and transmission hold special significance. Such missions must contend with limited onboard storage, brief data downlink windows, and low downlink bandwidths. A potential solution to these issues lies in employing onboard data processors (OBPs) to convert raw data into products that are smaller and closely capture relevant scientific phenomena. In this paper, we present the implementation of two OBP architectures for ice-penetrating sounding radars tasked with exploring Europa and Ganymede. Our first architecture utilizes an unfocused processing algorithm extended from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS, Jordan et. al. 2009). Compared to downlinking raw data, we are able to reduce data volume by approximately 100 times through OBP usage. To ensure the viability of our approach, we have implemented, simulated, and synthesized this architecture using both VHDL and Matlab models (with fixed-point and floating-point arithmetic) in conjunction with Modelsim. Creation of a VHDL model of our processor is the principle step in transitioning to actual digital hardware, whether in a FPGA (field-programmable gate array) or an ASIC (application-specific integrated circuit), and successful simulation and synthesis strongly indicate feasibility. In addition, we examined the tradeoffs faced in the OBP between fixed-point accuracy, resource consumption, and data product fidelity. Our second architecture is based upon a focused fast back projection (FBP) algorithm that requires a modest amount of computing power and on-board memory while yielding high along-track resolution and improved slope detection capability. We present an overview of the algorithm and details of our implementation, also in VHDL. With the appropriate tradeoffs, the use of OBPs can significantly reduce data downlink requirements without sacrificing data product fidelity. Through the development, simulation, and synthesis of two different OBP architectures, we have proven the feasibility and efficacy of an OBP for planetary ice-penetrating radars.

Ultrafast Microscopy of Spin-Momentum-Locked Surface Plasmon Polaritons.

PubMed

Dai, Yanan; Dąbrowski, Maciej; Apkarian, Vartkess A; Petek, Hrvoje

2018-06-26

Using two-photon photoemission electron microscopy (2P-PEEM) we image the polarization dependence of coupling and propagation of surface plasmon polaritons (SPPs) launched from edges of a triangular, micrometer size, single-crystalline Ag crystal by linearly or circularly polarized light. 2P-PEEM records interferences between the optical excitation field and SPPs it creates with nanofemto space-time resolution. Both the linearly and circularly polarized femtosecond light pulses excite spatially asymmetric 2PP yield distributions, which are imaged. We attribute the asymmetry for linearly polarized light to the relative alignments of the laser polarization and triangle edges, which affect the efficiency of excitation of the longitudinal component of the SPP field. For circular polarization, the asymmetry is caused by matching of the spin angular momenta (SAM) of light and the transverse SAM of SPPs. Moreover, we show that the interference patterns recorded in the 2P-PEEM images are cast by phase shifts and amplitudes for coupling of light into the longitudinal and transverse components of SPP fields. While the interference patterns depend on the excitation polarization, nanofemto movies show that the phase and group velocities of SPPs are independent of SAM of light in time-reversal invariant media. Simulations of the wave interference reproduce the polarization and spin-dependent coupling of optical pulses into SPPs.

[Motion control of moving mirror based on fixed-mirror adjustment in FTIR spectrometer].

PubMed

Li, Zhong-bing; Xu, Xian-ze; Le, Yi; Xu, Feng-qiu; Li, Jun-wei

2012-08-01

The performance of the uniform motion of the moving mirror, which is the only constant motion part in FTIR spectrometer, and the performance of the alignment of the fixed mirror play a key role in FTIR spectrometer, and affect the interference effect and the quality of the spectrogram and may restrict the precision and resolution of the instrument directly. The present article focuses on the research on the uniform motion of the moving mirror and the alignment of the fixed mirror. In order to improve the FTIR spectrometer, the maglev support system was designed for the moving mirror and the phase detection technology was adopted to adjust the tilt angle between the moving mirror and the fixed mirror. This paper also introduces an improved fuzzy PID control algorithm to get the accurate speed of the moving mirror and realize the control strategy from both hardware design and algorithm. The results show that the development of the moving mirror motion control system gets sufficient accuracy and real-time, which can ensure the uniform motion of the moving mirror and the alignment of the fixed mirror.

Wave-optical assessment of alignment tolerances in nano-focusing with ellipsoidal mirror

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

Yumoto, Hirokatsu, E-mail: yumoto@spring8.or.jp; Koyama, Takahisa; Matsuyama, Satoshi

2016-01-28

High-precision ellipsoidal mirrors, which can efficiently focus X-rays to the nanometer dimension with a mirror, have not been realized because of the difficulties in the fabrication process. The purpose of our study was to develop nano-focusing ellipsoidal mirrors in the hard X-ray region. We developed a wave-optical focusing simulator for investigating alignment tolerances in nano-focusing with a designed ellipsoidal mirror, which produce a diffraction-limited focus size of 30 × 35 nm{sup 2} in full width at half maximum at an X-ray energy of 7 keV. The simulator can calculate focusing intensity distributions around the focal point under conditions of misalignment. Themore » wave-optical simulator enabled the calculation of interference intensity distributions, which cannot be predicted by the conventional ray-trace method. The alignment conditions with a focal length error of ≲ ±10 µm, incident angle error of ≲ ±0.5 µrad, and in-plane rotation angle error of ≲ ±0.25 µrad must be satisfied for nano-focusing.« less

EDOS Evolution to Support NASA Future Earth Sciences Missions

NASA Technical Reports Server (NTRS)

Cordier, Guy R.; McLemore, Bruce; Wood, Terri; Wilkinson, Chris

2010-01-01

This paper presents a ground system architecture to service future NASA decadal missions and in particular, the high rate science data downlinks, by evolving EDOS current infrastructure and upgrading high rate network lines. The paper will also cover EDOS participation to date in formulation and operations concepts for the respective missions to understand the particular mission needs and derived requirements such as data volumes, downlink rates, data encoding, and data latencies. Future decadal requirements such as onboard data recorder management and file protocols drive the need to emulate these requirements within the ground system. The EDOS open system modular architecture is scalable to accommodate additional missions using the current sites antennas and future sites as well and meet the data security requirements and fulfill mission's objectives

DSS 13 frequency stability tests performed during May 1985 through March 1986

NASA Technical Reports Server (NTRS)

Otoshi, T. Y.; Franco, M. M.

1986-01-01

Results of station frequency stability testing performed at DSS 13 (Deep Space Station) during May 1985 through March 1986 are presented. The testing was done on X-band uplink and X- and S-band downlink subsystems as well as on end-to-end systems. The subsystem test data are useful for assessing the frequency stability of various prototype X-band uplink or downlink subsystems for purposes of making design improvements. Information derived from extensive testing at DSS 13 will be useful in the preparation of an X-band Uplink Demonstration Experiment to be conducted at DSS 13, and will also be valuable in the preparations of gravity wave experiments to be conducted at other DSN stations in the future.

The NASA Deep Space Network (DSN) Array

NASA Technical Reports Server (NTRS)

Gatti, Mark

2006-01-01

The DSN Array Project is currently working with Senior Management at both JPL and NASA to develop strategies towards starting a major implementation project. Several studies within NASA are concluding, all of which recommend that any future DSN capability include arraying of antennas to increase performance. Support of Deep Space, Lunar, and CEV (crewed exploration vehicle) missions is possible. High data rate and TDRSS formatting is being investigated. Any future DSN capacity must include Uplink. Current studies ongoing to investigate and develop technologies for uplink arraying; provides advantages in three ways: 1) N2 effect. EIRP grows as N2(-vs-N for a downlink array); 2) Improved architectural options (can separate uplink and downlink); and 3) Potential for more cost effective transmitters for fixed EIRP.

Feasibility of satellite quantum key distribution

NASA Astrophysics Data System (ADS)

Bonato, C.; Tomaello, A.; Da Deppo, V.; Naletto, G.; Villoresi, P.

2009-04-01

In this paper, we present a novel analysis of the feasibility of quantum key distribution between a LEO satellite and a ground station. First of all, we study signal propagation through a turbulent atmosphere for uplinks and downlinks, discussing the contribution of beam spreading and beam wandering. Then we introduce a model for the background noise of the channel during night-time and day-time, calculating the signal-to-noise ratio for different configurations. We also discuss the expected error-rate due to imperfect polarization compensation in the channel. Finally, we calculate the expected key generation rate of a secure key for different configurations (uplink, downlink) and for different protocols (BB84 with and without decoy states, entanglement-based Ekert91 protocol).

STS-54 Commander Casper with DSO 802 & Physics of Toys on OV-105's middeck

NASA Image and Video Library

1993-01-15

STS054-S-023 (15 Jan 1993) --- Casper holds up a paper boomerang before sailing it across Endeavour's middeck. The demonstration was part of a lengthy "physics of toys" program conducted by all five crewmembers on their third day aboard the Shuttle. Through telephone and TV downlinks, students in four schools around the country participated in a special lesson to discover how specific toys function differently in the classroom compared to those on the Shuttle. The boomerang was used to demonstrate Bernouli's principle and gyroscopic stability. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the autumn. The scene was downlinked at 18:11:04:26 GMT, Jan. 15, 1993.

Recent field experiments with commercial satellite imagery direct downlink.

PubMed

Gonzalez, Anthony R; Amber, Samuel H

US Pacific Command's strategy includes assistance to United States government relief agencies and nongovernment organizations during humanitarian aid and disaster relief operations in the Asia-Pacific region. Situational awareness during these operations is enhanced by broad interagency access to unclassified commercial satellite imagery. The Remote Ground Terminal-a mobile satellite downlink ground station-has undergone several technology demonstrations and participated in an overseas deployment exercise focused on a natural disaster scenario. This ground station has received new commercial imagery within 20 minutes, hastening a normally days-long process. The Army Geospatial Center continues to manage technology development and product improvement for the Remote Ground Terminal. Furthermore, this ground station is now on a technology transition path into the Distributed Common Ground System-Army program of record.

Signal design study for shuttle/TDRSS Ku-band uplink

NASA Technical Reports Server (NTRS)

1976-01-01

The adequacy of the signal design approach chosen for the TDRSS/orbiter uplink was evaluated. Critical functions and/or components associated with the baseline design were identified, and design alternatives were developed for those areas considered high risk. A detailed set of RF and signal processing performance specifications for the orbiter hardware associated with the TDRSS/orbiter Ku band uplink was analyzed. Performances of a detailed design of the PN despreader, the PSK carrier synchronization loop, and the symbol synchronizer are identified. The performance of the downlink signal by means of computer simulation to obtain a realistic determination of bit error rate degradations was studied. The three channel PM downlink signal was detailed by means of analysis and computer simulation.

STS-54 MS1 Runco uses DSO 802 and Physics of Toys racetrack on OV-105's middeck

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Mission Specialist 1 (MS1) Mario Runco, Jr watches as a toy friction car navigates a loop track on the middeck of the Earth-orbiting Endeavour, Orbiter Vehicle (OV) 105. The demonstration was part of Application Specific Preprogrammed Experiment Culture System Physics of Toys (ASPEC) and Detailed Supplementary Objective (DSO) 802, Educational activities. Through telephone and television (TV) downlinks, students at Sacred Heart School (notice banner in the background) in Bronx, New York -- Runco's birthplace -- asked him questions about the several toys he demonstrated. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the autumn. This scene was downlinked at 17:37:03:12 GMT.

Autonomous Instrument Placement for Mars Exploration Rovers

NASA Technical Reports Server (NTRS)

Leger, P. Chris; Maimone, Mark

2009-01-01

Autonomous Instrument Placement (AutoPlace) is onboard software that enables a Mars Exploration Rover to act autonomously in using its manipulator to place scientific instruments on or near designated rock and soil targets. Prior to the development of AutoPlace, it was necessary for human operators on Earth to plan every motion of the manipulator arm in a time-consuming process that included downlinking of images from the rover, analysis of images and creation of commands, and uplinking of commands to the rover. AutoPlace incorporates image analysis and planning algorithms into the onboard rover software, eliminating the need for the downlink/uplink command cycle. Many of these algorithms are derived from the existing groundbased image analysis and planning algorithms, with modifications and augmentations for onboard use.

Interference-Assisted Techniques for Transmission and Multiple Access in Optical Communications

NASA Astrophysics Data System (ADS)

Guan, Xun

Optical communications can be in wired or wireless form. Fiber optics communication (FOC) connects transmitters and receivers with optical fiber. Benefiting from its high bandwidth, low cost per volume and stability, it gains a significant market share in long-haul networks, access networks and data centers. Meanwhile, optical wireless communication (OWC) is also emerging as a crucial player in the communication market. In OWC, free-space optical communication (FSO) and visible light communication (VLC) are being studied and commercially deployed extensively. Interference is a common phenomenon in multi-user communication systems. In both FOC and OWC, interference has long been treated as a detrimental effect. However, it could also be beneficial to system applications. The effort of harnessing interference has spurred numerous innovations. Interesting examples are physical-layer network coding (PNC) and non-orthogonal multiple access (NOMA). The first part of this thesis in on the topic of PNC. PNC was firstly proposed in wireless communication to improve the throughput of a two-way relay network (TWRN). As a variation of network coding (NC), PNC turns the common channel interference (CCI) as a natural network coding operation. In this thesis, PNC is introduced into optical communication. Three schemes are proposed in different scenarios. Firstly, PNC is applied to a coherent optical orthogonal frequency division multiplexing (CO-OFDM) system so as to improve the throughput of the multicast network. The optical signal to noise ratio (OSNR) penalty is quite low. Secondly, we investigate the application of PNC in an OFDM passive optical network (OFDM-PON) supporting heterogeneous services. It is found that only minor receiver power penalties are observed to realize PNC-based virtual private networks (VPN), both in the wired service part and the wireless service part in an OFDM-PON with heterogeneous services. Thirdly, we innovate relay-based visible light communication (VLC) by adopting PNC, with a newly proposed phase-aligning method. PNC could improve the throughput at the bottlenecking relay node in a VLC system, and the proposed phase aligning method can improve the BER performance. The second part of this thesis discusses another interference-assisted technology in communication, that is, non-orthogonal multiple access (NOMA). NOMA multiplexes signals from multiple users in another dimension: power domain, with a non-orthogonal multiplexing in other dimensions such as time, frequency and code. Three schemes are proposed in this part. The first and the second schemes both realize NOMA in VLC, with different multiuser detection (MUD) techniques and a proposed phase pre-distortion method. Although both can decrease the system BER compared to conventional NOMA, the scheme using joint detection (JD) outperforms the one using successive interference cancellation (SIC). The third scheme investigated in this part is a combination of NOMA and a multicarrier precoding (MP) technology based on an orthogonal circulant transform matrix (OCT). This combination can avoid the complicated adaptive bit loading or electronic equalization, making NOMA more attractive in a practical system.

Ionosphere/microwave beam interaction study. [satellite solar energy conversion

NASA Technical Reports Server (NTRS)

Duncan, L. M.; Gordon, W. E.

1977-01-01

A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results.

Low-cost and miniaturized 100-Gb/s (2 × 50 Gb/s) PAM-4 TO-packaged ROSA for data center networks.

PubMed

Kang, Sae-Kyoung; Huh, Joon Young; Lee, Jie Hyun; Lee, Joon Ki

2018-03-05

We design and implement a cost-effective and compact 100-Gb/s (2 × 50 Gb/s) PAM-4 receiver optical sub-assembly (ROSA) by using a TO-can package instead of an expensive box-type package. It consists of an optical demultiplexer, two PIN-PDs and a 2-channel linear transimpedance amplifier. The components are passively aligned and assembled using alignment marks engraved on each part. With a real-time PAM-4 DSP chip, we measured the back-to-back receiver sensitivities of the 100-Gb/s ROSA based on TO-56 to be less than -13.2 dBm for both channels at a bit error rate of 2.4e-4. The crosstalk penalty due to the adjacent channel interference was observed around 0.1 dB.

Design and implementation of the next generation Landsat satellite communications system

USGS Publications Warehouse

Mah, Grant R.; O'Brien, Michael; Garon, Howard; Mott, Claire; Ames, Alan; Dearth, Ken

2012-01-01

The next generation Landsat satellite, Landsat 8 (L8), also known as the Landsat Data Continuity Mission (LDCM), uses a highly spectrally efficient modulation and data formatting approach to provide large amounts of downlink (D/L) bandwidth in a limited X-Band spectrum allocation. In addition to purely data throughput and bandwidth considerations, there were a number of additional constraints based on operational considerations for prevention of interference with the NASA Deep-Space Network (DSN) band just above the L8 D/L band, minimization of jitter contributions to prevent impacts to instrument performance, and the need to provide an interface to the Landsat International Cooperator (IC) community. A series of trade studies were conducted to consider either X- or Ka-Band, modulation type, and antenna coverage type, prior to the release of the request for proposal (RFP) for the spacecraft. Through use of the spectrally efficient rate-7/8 Low-Density Parity-Check error-correction coding and novel filtering, an XBand frequency plan was developed that balances all the constraints and considerations, while providing world-class link performance, fitting 384 Mbits/sec of data into the 375 MHz X-Band allocation with bit-error rates better than 10-12 using an earth-coverage antenna.

A Scalable Framework for CSI Feedback in FDD Massive MIMO via DL Path Aligning

NASA Astrophysics Data System (ADS)

Luo, Xiliang; Cai, Penghao; Zhang, Xiaoyu; Hu, Die; Shen, Cong

2017-09-01

Unlike the time-division duplexing (TDD) systems, the downlink (DL) and uplink (UL) channels are not reciprocal anymore in the case of frequency-division duplexing (FDD). However, some long-term parameters, e.g. the time delays and angles of arrival (AoAs) of the channel paths, still enjoy reciprocity. In this paper, by efficiently exploiting the aforementioned limited reciprocity, we address the DL channel state information (CSI) feedback in a practical wideband massive multiple-input multiple-output (MIMO) system operating in the FDD mode. With orthogonal frequency-division multiplexing (OFDM) waveform and assuming frequency-selective fading channels, we propose a scalable framework for the DL pilots design, DL CSI acquisition, and the corresponding CSI feedback in the UL. In particular, the base station (BS) can transmit the FFT-based pilots with the carefully-selected phase shifts. Then the user can rely on the so-called time-domain aggregate channel (TAC) to derive the feedback of reduced imensionality according to either its own knowledge about the statistics of the DL channels or the instruction from the serving BS. We demonstrate that each user can just feed back one scalar number per DL channel path for the BS to recover the DL CSIs. Comprehensive numerical results further corroborate our designs.

NASA Tech Briefs, March 2004

NASA Technical Reports Server (NTRS)

2004-01-01

Topics covered include: 1) Advanced Signal Conditioners for Data-Acquisition Systems; 2) Downlink Data Multiplexer; 3) Viewing ISS Data in Real Time via the Internet; 4) Autonomous Environment-Monitoring Networks; 5) Readout of DSN Monitor Data; 6) Parallel-Processing Equalizers for Multi-Gbps Communications; 7) AIN-Based Packaging for SiC High-Temperature Electronics; 8) Software for Optimizing Quality Assurance of Other Software; 9) The TechSat 21 Autonomous Sciencecraft Experiment; 10) Software for Analyzing Laminar-to-Turbulent Flow Transitions; 11) Elastomer Filled With Single-Wall Carbon Nanotubes; 12) Modifying Ship Air-Wake Vortices for Aircraft Operations; 13) Strain-Gauge Measurement of Weight of Fluid in a Tank; 14) Advanced Docking System With Magnetic Initial Capture; 15) Blade-Pitch Control for Quieting Tilt-Rotor Aircraft; 16) Solar Array Panels With Dust-Removal Capability; 17) Aligning Arrays of Lenses and Single-Mode Optical Fibers; 18) Automatic Control of Arc Process for Making Carbon Nanotubes; 19) Curved-Focal-Plane Arrays Using Deformed-Membrane Photodetectors; 20) Role of Meteorology in Flights of a Solar-Powered Airplane; 21) Model of Mixing Layer With Multicomponent Evaporating Drops; 22) Solution-Assisted Optical Contacting; 23) Improved Discrete Approximation of Laplacian of Gaussian; 24) Utilizing Expert Knowledge in Estimating Future STS Costs; 25) Study of Rapid-Regression Liquefying Hybrid Rocket Fuels; and 26) More About the Phase-Synchronized Enhancement Method.

Telecom and scintillation first data analysis for DOMINO: laser communication between SOTA, onboard SOCRATES satellite, and MEO optical ground station

NASA Astrophysics Data System (ADS)

Phung, D.-H.; Samain, E.; Maurice, N.; Albanesse, D.; Mariey, H.; Aimar, M.; M. Lagarde, G.; Artaud, G.; Issler, J.-L.; Vedrenne, N.; Velluet, M.-T.; Toyoshima, M.; Akioka, M.; Kolev, D.; Munemasa, Y.; Takenaka, H.; Iwakiri, N.

2016-03-01

In collaboration between CNES, NICT, Geoazur, the first successful lasercom link between the micro-satellite SOCRATES and an OGS in Europe has been established. This paper presents some results of telecom and scintillation first data analysis for 4 successful links in June & July 2015 between SOTA terminal and MEO optical ground station (OGS) at Caussols France. The telecom and scintillation data have been continuously recorded during the passes by using a detector developed at the laboratory. An irradiance of 190 nW/m2 and 430 nW/m2 has been detected for 1549 nm and 976 nm downlinks at 35° elevation. Spectrums of power fluctuation measured at OGS are analyzed at different elevation angles and at different diameters of telescope aperture to determine fluctuations caused by pointing error (due to satellite & OGS telescope vibrations) and caused by atmospheric turbulence. Downlink & Uplink budgets are analyzed, the theoretical estimation matches well to measured power levels. Telecom signal forms and bit error rates (BER) of 1549 nm and 976 nm downlink are also shown at different diameters of telescope aperture. BER is 'Error Free' with full-aperture 1.5m telescope, and almost in `good channel' with 0.4 m sub-aperture of telescope. We also show the comparison between the expected and measured BER distributions.

Pulsed laser-based optical frequency comb generator for high capacity wavelength division multiplexed passive optical network supporting 1.2 Tbps

NASA Astrophysics Data System (ADS)

Ullah, Rahat; Liu, Bo; Zhang, Qi; Saad Khan, Muhammad; Ahmad, Ibrar; Ali, Amjad; Khan, Razaullah; Tian, Qinghua; Yan, Cheng; Xin, Xiangjun

2016-09-01

An architecture for flattened and broad spectrum multicarriers is presented by generating 60 comb lines from pulsed laser driven by user-defined bit stream in cascade with three modulators. The proposed scheme is a cost-effective architecture for optical line terminal (OLT) in wavelength division multiplexed passive optical network (WDM-PON) system. The optical frequency comb generator consists of a pulsed laser in cascade with a phase modulator and two Mach-Zehnder modulators driven by an RF source incorporating no phase shifter, filter, or electrical amplifier. Optical frequency comb generation is deployed in the simulation environment at OLT in WDM-PON system supports 1.2-Tbps data rate. With 10-GHz frequency spacing, each frequency tone carries data signal of 20 Gbps-based differential quadrature phase shift keying (DQPSK) in downlink transmission. We adopt DQPSK-based modulation technique in the downlink transmission because it supports 2 bits per symbol, which increases the data rate in WDM-PON system. Furthermore, DQPSK format is tolerant to different types of dispersions and has a high spectral efficiency with less complex configurations. Part of the downlink power is utilized in the uplink transmission; the uplink transmission is based on intensity modulated on-off keying. Minimum power penalties have been observed with excellent eye diagrams and other transmission performances at specified bit error rates.

Calibration and performance measurements for the nasa deep space network aperture enhancement project (daep)

NASA Astrophysics Data System (ADS)

LaBelle, Remi C.; Rochblatt, David J.

2018-06-01

The NASA Deep Space Network (DSN) has recently constructed two new 34-m antennas at the Canberra Deep Space Communications Complex (CDSCC). These new antennas are part of the larger DAEP project to add six new 34-m antennas to the DSN, including two in Madrid, three in Canberra and one in Goldstone (California). The DAEP project included development and implementation of several new technologies for the X, and Ka (32 GHz) -band uplink and downlink electronics. The electronics upgrades were driven by several different considerations, including parts obsolescence, cost reduction, improved reliability and maintainability, and capability to meet future performance requirements. The new antennas are required to support TT&C links for all of the NASA deep-space spacecraft, as well as for several international partners. Some of these missions, such as Voyager 1 and 2, have very limited link budgets, which results in demanding requirements for system G/T performance. These antennas are also required to support radio science missions with several spacecraft, which dictate some demanding requirements for spectral purity, amplitude stability and phase stability for both the uplink and downlink electronics. After completion of these upgrades, a comprehensive campaign of tests and measurements took place to characterize the electronics and calibrate the antennas. Radiometric measurement techniques were applied to characterize, calibrate, and optimize the performance of the antenna parameters. These included optical and RF high-resolution holographic and total power radiometry techniques. The methodology and techniques utilized for the measurement and calibration of the antennas is described in this paper. Lessons learned (not all discussed in this paper) from the commissioning of the first antenna (DSS-35) were applied to the commissioning of the second antenna (DSS-36). These resulted in achieving antenna aperture efficiency of 66% (for DSS-36), at Ka-Band (32-Ghz), which is currently the highest operating frequency for these antennas. The other measurements and results described include antenna noise temperature, photogrammetry and holography alignment of antenna panels, beam-waveguide mirrors, and subreflector, antenna aperture efficiencies and G/T versus frequency, and antenna pointing models. The first antenna (DSS-35) entered into operations in October 2014 and the 2nd antenna (DSS-36) in October 2016. This paper describes the measurement techniques and results of the testing and calibration for both antennas, along with the driving requirements.

Fabrication and Characterization of Three Dimensional Photonic Crystals Generated by Multibeam Interference Lithography

DTIC Science & Technology

2009-01-01

and J. A. Lewis, "Microperiodic structures - Direct writing of three-dimensional webs ," Nature, vol. 428, pp. 386-386, 2004. [9] M. Campbell, D. N...of Applied Physics Part 1-Regular Papers Brief Communications & Review Papers , vol. 44, pp. 6355-6367, 2005. [75] P. Cloetens, W. Ludwig, J... paper screen on the sample holder and marking the beam position. If the central beam is properly aligned, the spot on the screen remains at the

Spacelab uplink/downlink data flow and formats

NASA Technical Reports Server (NTRS)

Kandefer, F.

1978-01-01

The results of an analysis of the Spacelab (SL) data uplink/downlink structure and those data system elements associated with the support of this data flow are presented. Specific objectives of this report are to present the results of the following analyses: (1) operations of the SL high rate multiplexer, including format structure, data rates, format combinations, format switching, etc.; (2) operations of SL data recorders to include the definition of modes, data rates and forms; (3) operations of the high rate demultiplexer as described above; (4) potential experiment data formats defining formatting parameters to be considered in decommutation analysis; (5) SL computer input/output (I/O) decommutation channels, including the definition of structure, quantity and use of this I/O data; (6) detailed requirements of the data quality monitoring philosophy for this function.

Characterization of Photon-Counting Detector Responsivity for Non-Linear Two-Photon Absorption Process

NASA Technical Reports Server (NTRS)

Sburlan, S. E.; Farr, W. H.

2011-01-01

Sub-band absorption at 1550 nm has been demonstrated and characterized on silicon Geiger mode detectors which normally would be expected to have no response at this wavelength. We compare responsivity measurements to singlephoton absorption for wavelengths slightly above the bandgap wavelength of silicon (approx. 1100 microns). One application for this low efficiency sub-band absorption is in deep space optical communication systems where it is desirable to track a 1030 nm uplink beacon on the same flight terminal detector array that monitors a 1550 nm downlink signal for pointingcontrol. The currently observed absorption at 1550 nm provides 60-70 dB of isolation compared to the response at 1064 nm, which is desirable to avoid saturation of the detector by scattered light from the downlink laser.

Solar Probe Plus MAG Sensor Thermal Design for Low Heater Power and Extreme Thermal Environment

NASA Technical Reports Server (NTRS)

Choi, Michael K.

2015-01-01

The heater power available for the Solar Probe Plus FIELDS MAG sensor is less than half of the heritage value for other missions. Nominally the MAG sensors are in the spacecraft's umbra. In the worst hot case, approximately 200 spacecraft communication downlinks, up to 10 hours each, are required at 0.7 AU. These downlinks require the spacecraft to slew 45 deg. about the Y-axis, exposing the MAG sensors and boom to sunlight. This paper presents the thermal design to meet the MAG sensor thermal requirements in the extreme thermal environment and with low heater power. A thermal balance test on the MAG sensor engineering model has verified the thermal design and correlated the thermal model for flight temperature predictions.

Measurement and Statistics of Application Business in Complex Internet

NASA Astrophysics Data System (ADS)

Wang, Lei; Li, Yang; Li, Yipeng; Wu, Shuhang; Song, Shiji; Ren, Yong

Owing to independent topologies and autonomic routing mechanism, the logical networks formed by Internet application business behavior cause the significant influence on the physical networks. In this paper, the backbone traffic of TUNET (Tsinghua University Networks) is measured, further more, the two most important application business: HTTP and P2P are analyzed at IP-packet level. It is shown that uplink HTTP and P2P packets behavior presents spatio-temporal power-law characteristics with exponents 1.25 and 1.53 respectively. Downlink HTTP packets behavior also presents power-law characteristics, but has more little exponents γ = 0.82 which differs from traditional complex networks research result. Moreover, downlink P2P packets distribution presents an approximate power-law which means that flow equilibrium profits little from distributed peer-to peer mechanism actually.

STS-54 Pilot McMonagle with DSO 802 and Physics of Toys top on OV-105's middeck

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Pilot Donald R. McMonagle watches as a top spins above his head on the middeck of the Earth-orbiting Endeavour, Orbiter Vehicle (OV) 105. The demonstration was part of Application Specific Preprogrammed Experiment Culture System Physics of Toys (ASPEC) and Detailed Supplementary Objective (DSO) 802, Educational activities. Through telephone and television (TV) downlinks, students at Westwood Elementary School in Flint, Michigan -- McMonagle's hometown -- asked him questions about the several toys he demonstrated. The top demonstrates gyroscopic motion, the center of mass and angular momentum. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the autumn. This scene was downlinked at 18:01:59:11 GMT.

STS-54 Commander Casper with DSO 802 and Physics of Toys on OV-105's middeck

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Commander John H. Casper holds up a paper boomerang before sailing it across the middeck of the Earth-orbiting Endeavour, Orbiter Vehicle (OV) 105. The demonstration was part of Application Specific Preprogrammed Experiment Culture System Physics of Toys (ASPEC) and Detailed Supplementary Objective (DSO) 802, Educational activities. Through telephone and TV downlinks, Casper conversed with students in four schools who participated in a special lesson to discover how specific toys function differently in the classroom compared to those on the Shuttle. The boomerang was used to demonstrate Bernouli's principle and gyroscopic stability. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the fall of this year. This scene was downlinked at 18:11:04:26 GMT.

Potential digitization/compression techniques for Shuttle video

NASA Technical Reports Server (NTRS)

Habibi, A.; Batson, B. H.

1978-01-01

The Space Shuttle initially will be using a field-sequential color television system but it is possible that an NTSC color TV system may be used for future missions. In addition to downlink color TV transmission via analog FM links, the Shuttle will use a high resolution slow-scan monochrome system for uplink transmission of text and graphics information. This paper discusses the characteristics of the Shuttle video systems, and evaluates digitization and/or bandwidth compression techniques for the various links. The more attractive techniques for the downlink video are based on a two-dimensional DPCM encoder that utilizes temporal and spectral as well as the spatial correlation of the color TV imagery. An appropriate technique for distortion-free coding of the uplink system utilizes two-dimensional HCK codes.

Novel Semi-Parametric Algorithm for Interference-Immune Tunable Absorption Spectroscopy Gas Sensing

PubMed Central

Michelucci, Umberto; Venturini, Francesca

2017-01-01

One of the most common limits to gas sensor performance is the presence of unwanted interference fringes arising, for example, from multiple reflections between surfaces in the optical path. Additionally, since the amplitude and the frequency of these interferences depend on the distance and alignment of the optical elements, they are affected by temperature changes and mechanical disturbances, giving rise to a drift of the signal. In this work, we present a novel semi-parametric algorithm that allows the extraction of a signal, like the spectroscopic absorption line of a gas molecule, from a background containing arbitrary disturbances, without having to make any assumption on the functional form of these disturbances. The algorithm is applied first to simulated data and then to oxygen absorption measurements in the presence of strong fringes.To the best of the authors’ knowledge, the algorithm enables an unprecedented accuracy particularly if the fringes have a free spectral range and amplitude comparable to those of the signal to be detected. The described method presents the advantage of being based purely on post processing, and to be of extremely straightforward implementation if the functional form of the Fourier transform of the signal is known. Therefore, it has the potential to enable interference-immune absorption spectroscopy. Finally, its relevance goes beyond absorption spectroscopy for gas sensing, since it can be applied to any kind of spectroscopic data. PMID:28991161

Interferenceless coded aperture correlation holography-a new technique for recording incoherent digital holograms without two-wave interference.

PubMed

Vijayakumar, A; Rosen, Joseph

2017-06-12

Recording digital holograms without wave interference simplifies the optical systems, increases their power efficiency and avoids complicated aligning procedures. We propose and demonstrate a new technique of digital hologram acquisition without two-wave interference. Incoherent light emitted from an object propagates through a random-like coded phase mask and recorded directly without interference by a digital camera. In the training stage of the system, a point spread hologram (PSH) is first recorded by modulating the light diffracted from a point object by the coded phase masks. At least two different masks should be used to record two different intensity distributions at all possible axial locations. The various recorded patterns at every axial location are superposed in the computer to obtain a complex valued PSH library cataloged to its axial location. Following the training stage, an object is placed within the axial boundaries of the PSH library and the light diffracted from the object is once again modulated by the same phase masks. The intensity patterns are recorded and superposed exactly as the PSH to yield a complex hologram of the object. The object information at any particular plane is reconstructed by a cross-correlation between the complex valued hologram and the appropriate element of the PSH library. The characteristics and the performance of the proposed system were compared with an equivalent regular imaging system.

Automated Sanger Analysis Pipeline (ASAP): A Tool for Rapidly Analyzing Sanger Sequencing Data with Minimum User Interference.

PubMed

Singh, Aditya; Bhatia, Prateek

2016-12-01

Sanger sequencing platforms, such as applied biosystems instruments, generate chromatogram files. Generally, for 1 region of a sequence, we use both forward and reverse primers to sequence that area, in that way, we have 2 sequences that need to be aligned and a consensus generated before mutation detection studies. This work is cumbersome and takes time, especially if the gene is large with many exons. Hence, we devised a rapid automated command system to filter, build, and align consensus sequences and also optionally extract exonic regions, translate them in all frames, and perform an amino acid alignment starting from raw sequence data within a very short time. In full capabilities of Automated Mutation Analysis Pipeline (ASAP), it is able to read "*.ab1" chromatogram files through command line interface, convert it to the FASTQ format, trim the low-quality regions, reverse-complement the reverse sequence, create a consensus sequence, extract the exonic regions using a reference exonic sequence, translate the sequence in all frames, and align the nucleic acid and amino acid sequences to reference nucleic acid and amino acid sequences, respectively. All files are created and can be used for further analysis. ASAP is available as Python 3.x executable at https://github.com/aditya-88/ASAP. The version described in this paper is 0.28.

On-board error correction improves IR earth sensor accuracy

NASA Astrophysics Data System (ADS)

Alex, T. K.; Kasturirangan, K.; Shrivastava, S. K.

1989-10-01

Infra-red earth sensors are used in satellites for attitude sensing. Their accuracy is limited by systematic and random errors. The sources of errors in a scanning infra-red earth sensor are analyzed in this paper. The systematic errors arising from seasonal variation of infra-red radiation, oblate shape of the earth, ambient temperature of sensor, changes in scan/spin rates have been analyzed. Simple relations are derived using least square curve fitting for on-board correction of these errors. Random errors arising out of noise from detector and amplifiers, instability of alignment and localized radiance anomalies are analyzed and possible correction methods are suggested. Sun and Moon interference on earth sensor performance has seriously affected a number of missions. The on-board processor detects Sun/Moon interference and corrects the errors on-board. It is possible to obtain eight times improvement in sensing accuracy, which will be comparable with ground based post facto attitude refinement.

Speech Cues Contribute to Audiovisual Spatial Integration

PubMed Central

Bishop, Christopher W.; Miller, Lee M.

2011-01-01

Speech is the most important form of human communication but ambient sounds and competing talkers often degrade its acoustics. Fortunately the brain can use visual information, especially its highly precise spatial information, to improve speech comprehension in noisy environments. Previous studies have demonstrated that audiovisual integration depends strongly on spatiotemporal factors. However, some integrative phenomena such as McGurk interference persist even with gross spatial disparities, suggesting that spatial alignment is not necessary for robust integration of audiovisual place-of-articulation cues. It is therefore unclear how speech-cues interact with audiovisual spatial integration mechanisms. Here, we combine two well established psychophysical phenomena, the McGurk effect and the ventriloquist's illusion, to explore this dependency. Our results demonstrate that conflicting spatial cues may not interfere with audiovisual integration of speech, but conflicting speech-cues can impede integration in space. This suggests a direct but asymmetrical influence between ventral ‘what’ and dorsal ‘where’ pathways. PMID:21909378

Demonstrating Broadband Billion-to-One Contrast with the Visible Nulling Coronagraph

NASA Technical Reports Server (NTRS)

Hicks, Brian A.; Lyon, Richard G.; Petrone, Peter, III; Miller, Ian J.; Bolcar, Matthew R.; Clampin, Mark; Helmbrecht, Michael A.; Mallik, Udayan

2015-01-01

The key to broadband operation of the Visible Nulling Coronagraph (VNC) is achieving a condition of quasi- achromatic destructive interference between combined beams. Here we present efforts towards meeting this goal using Fresnel rhombs in each interferometric arm as orthogonally aligned half wave phase retarders. The milestone goal of the demonstration is to achieve 1 × 10-9 contrast at 2/D over a 40 nm bandpass centered at 633 nm. Rhombs have been designed and fabricated, and a multi-step approach to alignment using coarse positioners for each rhomb and pair has been developed to get within range of piezo stages used for fine positioning. The previously demonstrated narrowband VNC sensing and control approach that uses a segmented deformable mirror is being adapted to broadband to include fine positioning of the piezo-mounted rhombs, all demonstrated in a low-pressure environment.

Vertically aligned carbon nanotube probes for monitoring blood cholesterol

NASA Astrophysics Data System (ADS)

Roy, Somenath; Vedala, Harindra; Choi, Wonbong

2006-02-01

Detection of blood cholesterol is of great clinical significance. The amperometric detection technique was used for the enzymatic assay of total cholesterol. Multiwall carbon nanotubes (MWNTs), vertically aligned on a silicon platform, promote heterogeneous electron transfer between the enzyme and the working electrode. Surface modification of the MWNT with a biocompatible polymer, polyvinyl alcohol (PVA), converted the hydrophobic nanotube surface into a highly hydrophilic one, which facilitates efficient attachment of biomolecules. The fabricated working electrodes showed a linear relationship between cholesterol concentration and the output signal. The efficacy of the multiwall carbon nanotubes in promoting heterogeneous electron transfer was evident by distinct electrochemical peaks and higher signal-to-noise ratio as compared to the Au electrode with identical enzyme immobilization protocol. The selectivity of the cholesterol sensor in the presence of common interferents present in human blood, e.g. uric acid, ascorbic acid and glucose, is also reported.

Aligning incentives in supply chains.

PubMed

Narayanan, V G; Raman, Ananth

2004-11-01

Most companies don't worry about the behavior of their supply chain partners. Instead, they expect the supply chain to work efficiently without interference, as if guided by Adam Smith's famed invisible hand. In their study of more than 50 supply networks, V.G. Narayanan and Ananth Raman found that companies often looked out for their own interests and ignored those of their network partners. Consequently, supply chains performed poorly. Those results aren't shocking when you consider that supply chains extend across several functions and many companies, each with its own priorities and goals. Yet all those functions and firms must pull in the same direction for a chain to deliver goods and services to consumers quickly and cost-effectively. According to the authors, a supply chain works well only if the risks, costs, and rewards of doing business are distributed fairly across the network. In fact, misaligned incentives are often the cause of excess inventory, stock-outs, incorrect forecasts, inadequate sales efforts, and even poor customer service. The fates of all supply chain partners are interlinked: If the firms work together to serve consumers, they will all win. However, they can do that only if incentives are aligned. Companies must acknowledge that the problem of incentive misalignment exists and then determine its root cause and align or redesign incentives. They can improve alignment by, for instance, adopting revenue-sharing contracts, using technology to track previously hidden information, or working with intermediaries to build trust among network partners. It's also important to periodically reassess incentives, because even top-performing networks find that changes in technology or business conditions alter the alignment of incentives.

IONAC-Lite

NASA Technical Reports Server (NTRS)

Torgerson, Jordan L.; Clare, Loren P.; Pang, Jackson

2011-01-01

The Interplanetary Overlay Net - working Protocol Accelerator (IONAC) described previously in The Inter - planetary Overlay Networking Protocol Accelerator (NPO-45584), NASA Tech Briefs, Vol. 32, No. 10, (October 2008) p. 106 (http://www.techbriefs.com/component/ content/article/3317) provides functions that implement the Delay Tolerant Networking (DTN) bundle protocol. New missions that require high-speed downlink-only use of DTN can now be accommodated by the unidirectional IONAC-Lite to support high data rate downlink mission applications. Due to constrained energy resources, a conventional software implementation of the DTN protocol can provide only limited throughput for any given reasonable energy consumption rate. The IONAC-Lite DTN Protocol Accelerator is able to reduce this energy consumption by an order of magnitude and increase the throughput capability by two orders of magnitude. In addition, a conventional DTN implementation requires a bundle database with a considerable storage requirement. In very high downlink datarate missions such as near-Earth radar science missions, the storage space utilization needs to be maximized for science data and minimized for communications protocol-related storage needs. The IONAC-Lite DTN Protocol Accelerator is implemented in a reconfigurable hardware device to accomplish exactly what s needed for high-throughput DTN downlink-only scenarios. The following are salient features of the IONAC-Lite implementation: An implementation of the Bundle Protocol for an environment that requires a very high rate bundle egress data rate. The C&DH (command and data handling) subsystem is also expected to be very constrained so the interaction with the C&DH processor and the temporary storage are minimized. Fully pipelined design so that bundle processing database is not required. Implements a lookup table-based approach to eliminate multi-pass processing requirement imposed by the Bundle Protocol header s length field structure and the SDNV (self-delimiting numeric value) data field formatting. 8-bit parallel datapath to support high data-rate missions. Reduced resource utilization implementation for missions that do not require custody transfer features. There was no known implementation of the DTN protocol in a field programmable gate array (FPGA) device prior to the current implementation. The combination of energy and performance optimization that embodies this design makes the work novel.

The chromokinesin Kid is required for maintenance of proper metaphase spindle size.

PubMed

Tokai-Nishizumi, Noriko; Ohsugi, Miho; Suzuki, Emiko; Yamamoto, Tadashi

2005-11-01

The human chromokinesin Kid/kinesin-10, a plus end-directed microtubule (MT)-based motor with both microtubule- and DNA-binding domains, is required for proper chromosome alignment at the metaphase plate. Here, we performed RNA interference experiments to deplete endogenous Kid from HeLa cells and confirmed defects in metaphase chromosome arm alignment in Kid-depleted cells. In addition, we noted a shortening of the spindle length, resulting in a pole-to-pole distance only 80% of wild type. The spindle microtubule-bundles with which Kid normally colocalize became less robust. Rescue of the two Kid deficiency phenotypes-imprecise chromosome alignment at metaphase and shortened spindles- exhibited distinct requirements. Mutants lacking either the DNA-binding domain or the MT motor ATPase failed to rescue the former defect, whereas rescue of the shortened spindle phenotype required neither activity. Kid also exhibits microtubule bundling activity in vitro, and rescue of the shortened spindle phenotype and the bundling activity displayed similar domain requirements, except that rescue required a coiled-coil domain not needed for bundling. These results suggest that distinct from its role in chromosome movement, Kid contributes to spindle morphogenesis by mediating spindle microtubules stabilization.

The Chromokinesin Kid Is Required for Maintenance of Proper Metaphase Spindle SizeD⃞

PubMed Central

Tokai-Nishizumi, Noriko; Ohsugi, Miho; Suzuki, Emiko; Yamamoto, Tadashi

2005-01-01

The human chromokinesin Kid/kinesin-10, a plus end-directed microtubule (MT)-based motor with both microtubule- and DNA-binding domains, is required for proper chromosome alignment at the metaphase plate. Here, we performed RNA interference experiments to deplete endogenous Kid from HeLa cells and confirmed defects in metaphase chromosome arm alignment in Kid-depleted cells. In addition, we noted a shortening of the spindle length, resulting in a pole-to-pole distance only 80% of wild type. The spindle microtubule-bundles with which Kid normally colocalize became less robust. Rescue of the two Kid deficiency phenotypes—imprecise chromosome alignment at metaphase and shortened spindles— exhibited distinct requirements. Mutants lacking either the DNA-binding domain or the MT motor ATPase failed to rescue the former defect, whereas rescue of the shortened spindle phenotype required neither activity. Kid also exhibits microtubule bundling activity in vitro, and rescue of the shortened spindle phenotype and the bundling activity displayed similar domain requirements, except that rescue required a coiled-coil domain not needed for bundling. These results suggest that distinct from its role in chromosome movement, Kid contributes to spindle morphogenesis by mediating spindle microtubules stabilization. PMID:16176979

Galileo radio science investigations

NASA Technical Reports Server (NTRS)

Howard, H. T.; Eshleman, V. R.; Hinson, D. P.; Kliore, A. J.; Lindal, G. F.; Woo, R.; Bird, M. K.; Volland, H.; Edenhoffer, P.; Paetzold, M.

1992-01-01

Galileo radio-propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal strength, and polarization. These measurements can be used to study: the atmospheric and ionospheric structure, constituents, and dynamics of Jupiter; the magnetic field of Jupiter; the diameter of Io, its ionospheric structure, and the distribution of plasma in the Io torus; the diameters of the other Galilean satellites, certain properties of their surfaces, and possibly their atmospheres and ionospheres; and the plasma dynamics and magnetic field of the solar corona. The spacecraft system provides linear rather than circular polarization on the S-band downlink signal, the capability to receive X-band uplink signals, and a differential downlink ranging mode. A highly-stable, dual-frequency, spacecraft radio system is developed that is suitable for simultaneous measurements of all the parameters normally attributed to radio waves.

Downlink power distributions for 2G and 3G mobile communication networks.

PubMed

Colombi, Davide; Thors, Björn; Persson, Tomas; Wirén, Niklas; Larsson, Lars-Eric; Jonsson, Mikael; Törnevik, Christer

2013-12-01

Knowledge of realistic power levels is key when conducting accurate EMF exposure assessments. In this study, downlink output power distributions for radio base stations in 2G and 3G mobile communication networks have been assessed. The distributions were obtained from network measurement data collected from the Operations Support System, which normally is used for network monitoring and management. Significant amounts of data were gathered simultaneously for large sets of radio base stations covering wide geographical areas and different environments. The method was validated with in situ measurements. For the 3G network, the 90th percentile of the averaged output power during high traffic hours was found to be 43 % of the maximum available power. The corresponding number for 2G, with two or more transceivers installed, was 65 % or below.

Full-duplex radio over fiber link with colorless source-free base station based on single sideband optical mm-wave signal with polarization rotated optical carrier

NASA Astrophysics Data System (ADS)

Ma, Jianxin

2016-07-01

A full-duplex radio-over fiber (RoF) link scheme based on single sideband (SSB) optical millimeter (mm)-wave signal with polarization-rotated optical carrier is proposed to realize the source-free colorless base station (BS), in which a polarization beam splitter (PBS) is used to abstract part of the optical carrier for conveying the uplink data. Since the optical carrier for the uplink does not bear the downlink signal, no cross-talk from the downlink contaminates the uplink signal. The simulation results demonstrate that both down- and up-links maintain good performance. The mm-wave signal distribution network based on the proposed full duplex fiber link scheme can use the uniform source-free colorless BSs, which makes the access system very simpler.

Switch for serial or parallel communication networks

DOEpatents

Crosette, D.B.

1994-07-19

A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination. 9 figs.

Switch for serial or parallel communication networks

DOEpatents

Crosette, Dario B.

1994-01-01

A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination.

Heterogeneous wireless/wireline optical access networks with the R-EAT as backend component

NASA Astrophysics Data System (ADS)

Hagedorn, Klaus; Gindera, Ralf; Stohr, Andreas; Jager, Dieter

2004-09-01

A heterogeneous wireless/wireline optical transmission link using a reflection type electroabsorption transceiver (R-EAT) is presented. Simultaneous transmission of full-duplex broadband wireless LAN (WLAN) channels and 1Gb/s base band data is experimentally demonstrated. The system link employs sub-carrier multiplexing (SCM) and two optical channels for full duplex transmission of various analog WLAN channels and downlink digital base band data. The developed link architecture is suitable for simultaneous transmission of broadband wireline and wireless signals, it enables the coexistence and interoperability between wireline and wireless access technologies. The developed R-EAT component employed in this wireline/wireless access system, features "single-chip-component" base stations in access networks with star type topology where only a single optical fiber is used for bidirectional optical transmission. The R-EAT can be used within the optical C-band (1530- 1560nm) and is suitable for (D)WDM networks. Bit error rate measurements demonstrate the capabilities of the R-EAT for 1Gb/s base band transmission. The analog performance for WLAN transmission is characterised by a spurious free dynamic range (SFDR) of more than 75dB and 90dB for uplink and downlink transmission, respectively. The link gain for uplink and downlink transmission is -42dB and -37dB, respectively. The demonstrates the analog performances of the R-EAT for being used in wireless access networks such as W-LAN.

A nucleolar protein RRS1 contributes to chromosome congression.

PubMed

Gambe, Arni E; Matsunaga, Sachihiro; Takata, Hideaki; Ono-Maniwa, Rika; Baba, Akiko; Uchiyama, Susumu; Fukui, Kiichi

2009-06-18

We report here the functional analysis of human Regulator of Ribosome Synthesis 1 (RRS1) protein during mitosis. We demonstrate that RRS1 localizes in the nucleolus during interphase and is distributed at the chromosome periphery during mitosis. RNA interference experiments revealed that RRS1-depleted cells show abnormalities in chromosome alignment and spindle organization, which result in mitotic delay. RRS1 knockdown also perturbs the centromeric localization of Shugoshin 1 and results in premature separation of sister chromatids. Our results suggest that a nucleolar protein RRS1 contributes to chromosome congression.

Simple Laser Communications Terminal for Downlink from Earth Orbit at Rates Exceeding 10 Gb/s

NASA Technical Reports Server (NTRS)

Kovalik, Joseph M.; Hemmati, Hamid; Biswas, Abhijit; Roberts, William T.

2013-01-01

A compact, low-cost laser communications transceiver was prototyped for downlinking data at 10 Gb/s from Earth-orbiting spacecraft. The design can be implemented using flight-grade parts. With emphasis on simplicity, compactness, and light weight of the flight transceiver, the reduced-complexity design and development approach involves: 1. A high-bandwidth coarse wavelength division multiplexed (CWDM) (4 2.5 or 10-Gb/s data-rate) downlink transmitter. To simplify the system, emphasis is on the downlink. Optical uplink data rate is modest (due to existing and adequate RF uplink capability). 2. Highly simplified and compact 5-cm diameter clear aperture optics assembly is configured to single transmit and receive aperture laser signals. About 2 W of 4-channel multiplexed (1,540 to 1,555 nm) optically amplified laser power is coupled to the optical assembly through a fiber optic cable. It contains a highly compact, precision-pointing capability two-axis gimbal assembly to coarse point the optics assembly. A fast steering mirror, built into the optical path of the optical assembly, is used to remove residual pointing disturbances from the gimbal. Acquisition, pointing, and tracking are assisted by a beacon laser transmitted from the ground and received by the optical assembly, which will allow transmission of a laser beam. 3. Shifting the link burden to the ground by relying on direct detection optical receivers retrofitted to 1-m-diameter ground telescopes. 4. Favored mass and volume reduction over power-consumption reduction. The two major variables that are available include laser transmit power at either end of the link, and telescope aperture diameter at each end of the link. Increased laser power is traded for smaller-aperture diameters. 5. Use of commercially available spacequalified or qualifiable components with traceability to flight qualification (i.e., a flight-qualified version is commercially available). An example is use of Telecordia-qualified fiber optic communication components including active components (lasers, amplifiers, photodetectors) that, except for vacuum and radiation, meet most of the qualifications required for space. 6. Use of CWDM technique at the flight transmitter for operation at four channels (each at 2.5 Gb/s or a total of 10 Gb/s data rate). Applying this technique allows utilization of larger active area photodetectors at the ground station. This minimizes atmospheric scintillation/turbulence induced losses on the received beam at the ground terminal. 7. Use of forward-error-correction and deep-interleaver codes to minimize atmospheric turbulence effects on the downlink beam. Target mass and power consumption for the flight data transmitter system is less than 10 kg and approximately 60 W for the 400-km orbit (900-km slant range), and 12 kg and 120 W for the 2,000-km orbit (6,000-km slant range). The higher mass and power for the latter are the result of employing a higher-power laser only.

Optical add/drop filter for wavelength division multiplexed systems

DOEpatents

Deri, Robert J.; Strand, Oliver T.; Garrett, Henry E.

2002-01-01

An optical add/drop filter for wavelength division multiplexed systems and construction methods are disclosed. The add/drop filter includes a first ferrule having a first pre-formed opening for receiving a first optical fiber; an interference filter oriented to pass a first set of wavelengths along the first optical fiber and reflect a second set of wavelengths; and, a second ferrule having a second pre-formed opening for receiving the second optical fiber, and the reflected second set of wavelengths. A method for constructing the optical add/drop filter consists of the steps of forming a first set of openings in a first ferrule; inserting a first set of optical fibers into the first set of openings; forming a first set of guide pin openings in the first ferrule; dividing the first ferrule into a first ferrule portion and a second ferrule portion; forming an interference filter on the first ferrule portion; inserting guide pins through the first set of guide pin openings in the first ferrule portion and second ferrule portion to passively align the first set of optical fibers; removing material such that light reflected from the interference filter from the first set of optical fibers is accessible; forming a second set of openings in a second ferrule; inserting a second set of optical fibers into the second set of openings; and positioning the second ferrule with respect to the first ferrule such that the second set of optical fibers receive the light reflected from the interference filter.

Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

PubMed Central

Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

2015-01-01

In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

Realizing one-dimensional quantum and high-frequency transport features in aligned single-walled carbon nanotube ropes

NASA Astrophysics Data System (ADS)

Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath

2014-07-01

The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2-300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80-300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.

Twisted nematic liquid crystal cells with rubbed poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) films for active polarization control of terahertz waves

NASA Astrophysics Data System (ADS)

Sasaki, Tomoyuki; Okuyama, Hiroki; Sakamoto, Moritsugu; Noda, Kohei; Okamoto, Hiroyuki; Kawatsuki, Nobuhiro; Ono, Hiroshi

2017-04-01

We fabricated a terahertz (THz) polarization converter using a twisted nematic (TN) liquid crystal (LC) cell. Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) films coated on quartz glass substrates were used as electrode layers in the TN LC cell. The PEDOT/PSS films were rubbed unidirectionally using a rayon cloth to align the nematic LC, thereby also serving as an alignment layer. The azimuthal surface anchoring strength of the PEDOT/PSS films was measured to be 5 × 10-4 J/m2 using the Néel wall method, which is similar to that of typical polymeric alignment layers. The optical constants of the PEDOT/PSS film in the THz range were also characterized using the Drude-Smith model, and the results indicated that the PEDOT/PSS films could be used both as transparent electrodes in the THz range and as alignment layers for the LC. The electro-optical properties of the fabricated TN LC cell were also investigated using a polarized visible laser and THz time-domain spectroscopic system. In particular, the transmission spectra and polarization conversion property of the TN LC cell in the THz range were theoretically analyzed based on a stratified model that considers optical anisotropy, absorption, and multiple interference. This work substantiates the advantages of TN LC cells with rubbed PEDOT/PSS films useful for THz polarization converters with electrical tunability.

An Active K-Band Receive Slot Array for Mobile Satellite Communications

NASA Technical Reports Server (NTRS)

Tulintseff, A. N.; Lee, K. A.; Sukamto, L. M.; Chew, W.

1994-01-01

An active receive slot array has been developed for operation in the downlink frequency band, 19.914-20.064 GHz, of NASA's Advanced Communication Technology Satellite (ACTS) for the ACTS Mobile Terminal (AMT) project.

Downlinks for DBS - Design and engineering considerations

NASA Astrophysics Data System (ADS)

Blecker, M.; Martin, E. R.

1985-01-01

The subsystem interrelationships and design parameters choice procedures for a DBS downlink design are discussed from a business decisions point of view. The image quality is determined by customer satisfaction, which is translated to a required carrier/noise (C/N) ratio. The C/N ratio defines acceptable levels of signal fading, a subjective value which is modified by the demographics of the service area. Increasing the satellite on-board transmitting power to meet acceptable broadcast reliability places burdens on the start-up capitalization of the business. Larger receiving antennas in rural areas ameliorates some of the power requirements. The dish size, however, affects the labor costs of installation, but must be kept small enough to be used in heavily populated areas. The satellites must be built, as far as is possible, from off-the-shelf components to keep costs down. Design selections for a sample complete system are listed.

Incorporating CCSDS telemetry standards and philosophy on Cassini

NASA Technical Reports Server (NTRS)

Day, John C.; Elson, Anne B.

1995-01-01

The Cassini project at the Jet Propulsion Laboratory (JPL) is implementing a spacecraft telemetry system based on the Consultative Committee for Space Data Systems (CCSDS) packet telemetry standards. Resolving the CCSDS concepts with a Ground Data System designed to handle time-division-multiplexed telemetry and also handling constraints unique to a deep-space planetary spacecraft (such as fixed downlink opportunities, small downlink rates and requirements for on-board data storage) have resulted in spacecraft and ground system design challenges. Solving these design challenges involved adapting and extending the CCSDS telemetry standards as well as changes to the spacecraft and ground system designs. The resulting spacecraft/ground system design is an example of how new ideas and philosophies can be incorporated into existing systems and design approaches without requiring significant rework. In addition, it shows that the CCSDS telemetry standards can be successfully applied to deep-space planetary spacecraft.

Portable color multimedia training systems based on monochrome laptop computers (CBT-in-a-briefcase), with spinoff implications for video uplink and downlink in spaceflight operations

NASA Technical Reports Server (NTRS)

Scott, D. W.

1994-01-01

This report describes efforts to use digital motion video compression technology to develop a highly portable device that would convert 1990-91 era IBM-compatible and/or MacIntosh notebook computers into full-color, motion-video capable multimedia training systems. An architecture was conceived that would permit direct conversion of existing laser-disk-based multimedia courses with little or no reauthoring. The project did not physically demonstrate certain critical video keying techniques, but their implementation should be feasible. This investigation of digital motion video has spawned two significant spaceflight projects at MSFC: one to downlink multiple high-quality video signals from Spacelab, and the other to uplink videoconference-quality video in realtime and high quality video off-line, plus investigate interactive, multimedia-based techniques for enhancing onboard science operations. Other airborne or spaceborne spinoffs are possible.

Bubble and Drop Nonlinear Dynamics experiment

NASA Technical Reports Server (NTRS)

2003-01-01

The Bubble and Drop Nonlinear Dynamics (BDND) experiment was designed to improve understanding of how the shape and behavior of bubbles respond to ultrasound pressure. By understanding this behavior, it may be possible to counteract complications bubbles cause during materials processing on the ground. This 12-second sequence came from video downlinked from STS-94, July 5 1997, MET:3/19:15 (approximate). The BDND guest investigator was Gary Leal of the University of California, Santa Barbara. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced fluid dynamics experiments will be a part of investigations plarned for the International Space Station. (189KB JPEG, 1293 x 1460 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300163.html.

Full-duplex bidirectional data transmission link using twisted lights multiplexing over 1.1-km orbital angular momentum fiber

PubMed Central

Chen, Shi; Liu, Jun; Zhao, Yifan; Zhu, Long; Wang, Andong; Li, Shuhui; Du, Jing; Du, Cheng; Mo, Qi; Wang, Jian

2016-01-01

We present a full-duplex bidirectional data transmission link using twisted lights multiplexing over 1.1-km orbital angular momentum (OAM) fiber. OAM+1 and OAM−1 modes carrying 20-Gbit/s quadrature phase-shift keying (QPSK) signals are employed in the downlink and uplink transmission experiments. The observed mode crosstalks are less than −15.2 dB, and the full-duplex crosstalks are less than −12.7 dB. The measured full-duplex optical signal-to-noise ratio (OSNR) penalties at a bit-error rate (BER) of 2 × 10−3 are ~2.4 dB in the downlink transmission and ~2.3 dB in the uplink transmission. The obtained results show favorable full-duplex twisted lights multiplexing data transmission performance in a km-scale OAM fiber link. PMID:27901082

On-board demux/demod

NASA Technical Reports Server (NTRS)

Sayegh, S.; Kappes, M.; Thomas, J.; Snyder, J.; Eng, M.; Poklemba, John J.; Steber, M.; House, G.

1991-01-01

To make satellite channels cost competitive with optical cables, the use of small, inexpensive earth stations with reduced antenna size and high powered amplifier (HPA) power will be needed. This will necessitate the use of high e.i.r.p. and gain-to-noise temperature ratio (G/T) multibeam satellites. For a multibeam satellite, onboard switching is required in order to maintain the needed connectivity between beams. This switching function can be realized by either an receive frequency (RF) or a baseband unit. The baseband switching approach has the additional advantage of decoupling the up-link and down-link, thus enabling rate and format conversion as well as improving the link performance. A baseband switching satellite requires the demultiplexing and demodulation of the up-link carriers before they can be switched to their assigned down-link beams. Principles of operation, design and implementation issues of such an onboard demultiplexer/demodulator (bulk demodulator) that was recently built at COMSAT Labs. are discussed.

Mission science value-cost savings from the Advanced Imaging Communication System (AICS)

NASA Technical Reports Server (NTRS)

Rice, R. F.

1984-01-01

An Advanced Imaging Communication System (AICS) was proposed in the mid-1970s as an alternative to the Voyager data/communication system architecture. The AICS achieved virtually error free communication with little loss in the downlink data rate by concatenating a powerful Reed-Solomon block code with the Voyager convolutionally coded, Viterbi decoded downlink channel. The clean channel allowed AICS sophisticated adaptive data compression techniques. Both Voyager and the Galileo mission have implemented AICS components, and the concatenated channel itself is heading for international standardization. An analysis that assigns a dollar value/cost savings to AICS mission performance gains is presented. A conservative value or savings of $3 million for Voyager, $4.5 million for Galileo, and as much as $7 to 9.5 million per mission for future projects such as the proposed Mariner Mar 2 series is shown.

RAID Disk Arrays for High Bandwidth Applications

NASA Technical Reports Server (NTRS)

Moren, Bill

1996-01-01

High bandwidth applications require large amounts of data transferred to/from storage devices at extremely high data rates. Further, these applications often are 'real time' in which access to the storage device must take place on the schedule of the data source, not the storage. A good example is a satellite downlink - the volume of data is quite large and the data rates quite high (dozens of MB/sec). Further, a telemetry downlink must take place while the satellite is overhead. A storage technology which is ideally suited to these types of applications is redundant arrays of independent discs (RAID). Raid storage technology, while offering differing methodologies for a variety of applications, supports the performance and redundancy required in real-time applications. Of the various RAID levels, RAID-3 is the only one which provides high data transfer rates under all operating conditions, including after a drive failure.

Design concepts and performance of NASA X-band transponder (DST) for deep space spacecraft applications

NASA Technical Reports Server (NTRS)

Mysoor, Narayan R.; Perret, Jonathan D.; Kermode, Arthur W.

1991-01-01

The design concepts and measured performance characteristics of an X band (7162 MHz/8415 MHz) breadboard deep space transponder (DST) for future spacecraft applications, with the first use scheduled for the Comet Rendezvous Asteroid Flyby (CRAF) and Cassini missions in 1995 and 1996, respectively. The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X band (8415 MHz) exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X band (7162 MHz) uplink carrier signal. The exciter phase modulates the X band (8415 MHz) downlink signal with composite telemetry and ranging signals. The receiver measured tracking threshold, automatic gain control static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB.

An X-band spacecraft transponder for deep space applications - Design concepts and breadboard performance

NASA Technical Reports Server (NTRS)

Mysoor, Narayan R.; Perret, Jonathan D.; Kermode, Arthur W.

1992-01-01

The design concepts and measured performance characteristics are summarized of an X band (7162 MHz/8415 MHz) breadboard deep space transponder (DSP) for future spacecraft applications, with the first use scheduled for the Comet Rendezvous Asteroid Flyby (CRAF) and Cassini missions in 1995 and 1996, respectively. The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X band (8415 MHz) exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X band (7162 MHz) uplink carrier signal. The exciter phase modulates the band (8415 MHz) downlink signal with composite telemetry and ranging signals. The receiver measured tracking threshold, automatic gain control, static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB.

STS-54 Pilot McMonagle with DSO 802 & Physics of Toys top on OV-105's middeck

NASA Image and Video Library

1993-01-15

STS054-S-020 (15 Jan 1993) --- McMonagle watches as a top spins above his head on the middeck of the Earth-orbiting Endeavour. The demonstration was part of a lengthy "physics of toys" program conducted by all five crewmembers on their third day aboard the Shuttle. Through telephone and TV downlinks, students in four schools around the country participated in a special lesson to discover how specific toys function differently in the classroom compared to those on the Shuttle. Students at Westwood Elementary School in Flint, Michigan -- McMonagle's hometown -- asked him questions about the several toys he demonstrated. The top demonstrates gyroscopic motion, the center of mass and angular momentum. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the autumn. The scene was downlinked at 18:01:59:11 GMT, Jan. 15, 1993.

Bubbles Responding to Ultrasound Pressure

NASA Technical Reports Server (NTRS)

2003-01-01

The Bubble and Drop Nonlinear Dynamics (BDND) experiment was designed to improve understanding of how the shape and behavior of bubbles respond to ultrasound pressure. By understanding this behavior, it may be possible to counteract complications bubbles cause during materials processing on the ground. This 12-second sequence came from video downlinked from STS-94, July 5 1997, MET:3/19:15 (approximate). The BDND guest investigator was Gary Leal of the University of California, Santa Barbara. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced fluid dynamics experiments will be a part of investigations plarned for the International Space Station. (435KB, 13-second MPEG, screen 160 x 120 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300162.html.

STS-54 crewmembers with DSO 802 and Physics of Toys on OV-105's middeck

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Commander John H. Casper, holding microphone, talks to a television (TV) audience including students on the middeck of the Earth-orbiting Endeavour, Orbiter Vehicle (OV) 105. Surrounded by crewmembers, Casper explains how specific toys function differently in the classroom versus in space as part of Application Specific Preprogrammed Experiment Culture System Physics of Toys (ASPEC) and Detailed Supplementary Objective (DSO) 802, Educational activities. Through telephone and TV downlinks, Casper and crewmembers conversed with students in four schools who participated in the special lesson. Counter clockwise from the left are Mission Specialist 3 (MS3) Susan J. Helms, Casper, Pilot Donald R. McMonagle, MS1 Mario Runco, Jr, and MS2 Gregory J. Harbaugh. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the autumn. This scene was downlinked at 18:28:04:18 GMT.

STS-54 MS3 Helms uses DSO 802 and Physics of Toys frog toy on OV-105's middeck

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Mission Specialist 3 (MS3) Susan J. Helms with a frog swimmer toy on the middeck of the Earth-orbiting Endeavour, Orbiter Vehicle (OV) 105, demonstrates some of the physics of toys to students watching on television (TV). The demonstration was part of Application Specific Preprogrammed Experiment Culture System Physics of Toys (ASPEC) and Detailed Supplementary Objective (DSO) 802, Educational activities. Through telephone and TV downlinks, Helms fielded questions from students at Shaver Elementary School in Portland, Oregon. The swimmer frog was used to demonstrate Newton's third law of motion and the conservation of angular momentum. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the fall of this year. Helms wears an Oregon Trail t-shirt. This scene was downlinked at 17:51:38:12 GMT.

STS-54 MS3 Helms uses DSO 802 and Physics of Toys fish toy on OV-105's middeck

NASA Technical Reports Server (NTRS)

1993-01-01

STS-54 Mission Specialist 3 (MS3) Susan J. Helms with a fish toy on the middeck of the Earth-orbiting Endeavour, Orbiter Vehicle (OV) 105, demonstrates some of the physics of toys to students watching on television (TV). The demonstration was part of Application Specific Preprogrammed Experiment Culture System Physics of Toys (ASPEC) and Detailed Supplementary Objective (DSO) 802, Educational activities. Through telephone and TV downlinks, Helms fielded questions from students at Shaver Elementary School in Portland, Oregon. The fish was used to demonstrate Newton's third law of motion and the conservation of angular momentum. The entire collection of toys will be videotaped for an educational program to be distributed to schools in the fall of this year. Helms wears an Oregon Trail t-shirt. This scene was downlinked at 17:50:08:27 GMT.

Worst-Case Energy Efficiency Maximization in a 5G Massive MIMO-NOMA System.

PubMed

Chinnadurai, Sunil; Selvaprabhu, Poongundran; Jeong, Yongchae; Jiang, Xueqin; Lee, Moon Ho

2017-09-18

In this paper, we examine the robust beamforming design to tackle the energy efficiency (EE) maximization problem in a 5G massive multiple-input multiple-output (MIMO)-non-orthogonal multiple access (NOMA) downlink system with imperfect channel state information (CSI) at the base station. A novel joint user pairing and dynamic power allocation (JUPDPA) algorithm is proposed to minimize the inter user interference and also to enhance the fairness between the users. This work assumes imperfect CSI by adding uncertainties to channel matrices with worst-case model, i.e., ellipsoidal uncertainty model (EUM). A fractional non-convex optimization problem is formulated to maximize the EE subject to the transmit power constraints and the minimum rate requirement for the cell edge user. The designed problem is difficult to solve due to its nonlinear fractional objective function. We firstly employ the properties of fractional programming to transform the non-convex problem into its equivalent parametric form. Then, an efficient iterative algorithm is proposed established on the constrained concave-convex procedure (CCCP) that solves and achieves convergence to a stationary point of the above problem. Finally, Dinkelbach's algorithm is employed to determine the maximum energy efficiency. Comprehensive numerical results illustrate that the proposed scheme attains higher worst-case energy efficiency as compared with the existing NOMA schemes and the conventional orthogonal multiple access (OMA) scheme.

Worst-Case Energy Efficiency Maximization in a 5G Massive MIMO-NOMA System

PubMed Central

Jeong, Yongchae; Jiang, Xueqin; Lee, Moon Ho

2017-01-01

In this paper, we examine the robust beamforming design to tackle the energy efficiency (EE) maximization problem in a 5G massive multiple-input multiple-output (MIMO)-non-orthogonal multiple access (NOMA) downlink system with imperfect channel state information (CSI) at the base station. A novel joint user pairing and dynamic power allocation (JUPDPA) algorithm is proposed to minimize the inter user interference and also to enhance the fairness between the users. This work assumes imperfect CSI by adding uncertainties to channel matrices with worst-case model, i.e., ellipsoidal uncertainty model (EUM). A fractional non-convex optimization problem is formulated to maximize the EE subject to the transmit power constraints and the minimum rate requirement for the cell edge user. The designed problem is difficult to solve due to its nonlinear fractional objective function. We firstly employ the properties of fractional programming to transform the non-convex problem into its equivalent parametric form. Then, an efficient iterative algorithm is proposed established on the constrained concave-convex procedure (CCCP) that solves and achieves convergence to a stationary point of the above problem. Finally, Dinkelbach’s algorithm is employed to determine the maximum energy efficiency. Comprehensive numerical results illustrate that the proposed scheme attains higher worst-case energy efficiency as compared with the existing NOMA schemes and the conventional orthogonal multiple access (OMA) scheme. PMID:28927019

Novel toggle-rate based energy-efficient scheme for heavy load real-time IM-DD OFDM-PON with ONU LLID identification in time-domain using amplitude decision.

PubMed

Qin, Youxiang; Zhang, Junjie

2017-07-10

A novel low complexity and energy-efficient scheme by controlling the toggle-rate of ONU with time-domain amplitude identification is proposed for a heavy load downlink in an intensity-modulation and direct-detection orthogonal frequency division multiplexing passive optical network (IM-DD OFDM-PON). In a conventional OFDM-PON downlink, all ONUs have to perform demodulation for all the OFDM frames in a broadcast way no matter whether the frames are targeted to or not, which causes a huge energy waste. However, in our scheme, the optical network unit (ONU) logical link identifications (LLIDs) are inserted into each downlink OFDM frame in time-domain at the optical line terminal (OLT) side. At the ONU side, the LLID is obtained with a low complexity and high precision amplitude identification method. The ONU sets the toggle-rate of demodulation module to zero when the frames are not targeted to, which avoids unnecessary digital signal processing (DSP) energy consumption. Compared with the sleep-mode methods consisting of clock recovery and synchronization, toggle-rate shows its advantage in fast changing, which is more suitable for the heavy load scenarios. Moreover, for the first time to our knowledge, the characteristics of the proposed scheme are investigated in a real-time IM-DD OFDM system, which performs well at the received optical power as low as -21dBm. The experimental results show that 25.1% energy consumption can be saved in the receiver compared to the conventional configurations.

Validity of a heart rate monitor during work in the laboratory and on the Space Shuttle

NASA Technical Reports Server (NTRS)

Moore, A. D. Jr; Lee, S. M.; Greenisen, M. C.; Bishop, P.

1997-01-01

Accurate heart rate measurement during work is required for many industrial hygiene and ergonomics situations. The purpose of this investigation was to determine the validity of heart rate measurements obtained by a simple, lightweight, commercially available wrist-worn heart rate monitor (HRM) during work (cycle exercise) sessions conducted in the laboratory and also during the particularly challenging work environment of space flight. Three different comparisons were made. The first compared HRM data to simultaneous electrocardiogram (ECG) recordings of varying heart rates that were generated by an ECG simulator. The second compared HRM data to ECG recordings collected during work sessions of 14 subjects in the laboratory. Finally, ECG downlink and HRM data were compared in four astronauts who performed cycle exercise during space flight. The data were analyzed using regression techniques. The results were that the HRM recorded virtually identical heart rates compared with ECG recordings for the data set generated by an ECG simulator. The regression equation for the relationship between ECG versus HRM heart rate data during work in the laboratory was: ECG HR = 0.99 x (HRM) + 0.82 (r2 = 0.99). Finally, the agreement between ECG downlink data and HRM data during space flight was also very high, with the regression equation being: Downlink ECG HR = 1.05 x (HRM) -5.71 (r2 = 0.99). The results of this study indicate that the HRM provides accurate data and may be used to reliably obtain valid data regarding heart rate responses during work.

Performance Analysis of Power Saving Class of Type I for Voice Service in Two-Way Communication in IEEE 802.16e

NASA Astrophysics Data System (ADS)

Hwang, Eunju; Kim, Kyung Jae; Choi, Bong Dae

In IEEE 802.16e, power saving is one of the important issues for battery-powered mobile stations (MSs). We present a performance analysis of power saving class (PSC) of type I in IEEE 802.16e standard for voice over Internet protocol (VoIP) service with silence suppression in two-way communication. On-off pattern of a voice user in two-way communication is characterized by the modified Brady model, which includes short silence gaps less than 200ms and talkspurt periods shorter than 15ms, and so differs from the Brady model. Our analysis of PSC I follows the standard-based procedure for the deactivation of the sleep mode, where a uplink packet arrival during a mutual silence period wakes up the MS immediately while a downlink packet arrival waits to be served until the next listening window. We derive the delay distribution of the first downlink packet arriving during a mutual silence period, and find the dropping probability of downlink packets since a voice packet drops if it is not transmitted within maximum delay constraint. In addition, we calculate the average power consumption under the modified Brady model. Analysis and simulation results show that the sleep mode operation for the MS with VoIP service yields 32 ∼ 39% reduction in the power consumption of the MS. Finally we obtain the optimal initial/final-sleep windows that yield the minimum average power consumption while satisfying QoS constraints on the packet dropping probability and the maximum delay.

Laser guide stars for optical free-space communications

NASA Astrophysics Data System (ADS)

Mata-Calvo, Ramon; Bonaccini Calia, Domenico; Barrios, Ricardo; Centrone, Mauro; Giggenbach, Dirk; Lombardi, Gianluca; Becker, Peter; Zayer, Igor

2017-02-01

The German Aerospace Center (DLR) and the European Southern Observatory (ESO) performed a measurement campaign together in April and July 2016 at Teide-Observatory (Tenerife), with the support of the European Space Agency (ESA), to investigate the use of laser guide stars (LGS) in ground to space optical communications. Atmospheric turbulence causes strong signal fluctuations in the uplink, due to scintillation and beam wander. In space communications, the use of the downlink channel as reference for pointing and for pre-distortion adaptive optics is limited by the size of the isokinetic and isoplanatic angle in relation to the required point-ahead angle. Pointing and phase errors due to the decorrelation between downward and upward beam due to the point-ahead angle may have a severe impact on the required transmit power and the stability of the communications link. LGSs provide a self-tailored reference to any optical ground-to-space link, independently of turbulence conditions and required point-ahead angle. In photon-starved links, typically in deep-space scenarios, LGSs allow dedicating all downlink received signal to communications purposes, increasing the available link margin. The scope of the joint DLR-ESO measurement campaign was, first, to measure the absolute value of the beam wander (uplink-tilt) using a LGS, taking a natural star as a reference, and, second, to characterize the decrease of correlation between uplink-tilt and downlink-tilt with respect to the angular separation between both sources. This paper describes the experiments performed during the measurement campaigns, providing an overview of the measured data and the first outcomes of the data post-processing.

Software systems for operation, control, and monitoring of the EBEX instrument

NASA Astrophysics Data System (ADS)

Milligan, Michael; Ade, Peter; Aubin, François; Baccigalupi, Carlo; Bao, Chaoyun; Borrill, Julian; Cantalupo, Christopher; Chapman, Daniel; Didier, Joy; Dobbs, Matt; Grainger, Will; Hanany, Shaul; Hillbrand, Seth; Hubmayr, Johannes; Hyland, Peter; Jaffe, Andrew; Johnson, Bradley; Kisner, Theodore; Klein, Jeff; Korotkov, Andrei; Leach, Sam; Lee, Adrian; Levinson, Lorne; Limon, Michele; MacDermid, Kevin; Matsumura, Tomotake; Miller, Amber; Pascale, Enzo; Polsgrove, Daniel; Ponthieu, Nicolas; Raach, Kate; Reichborn-Kjennerud, Britt; Sagiv, Ilan; Tran, Huan; Tucker, Gregory S.; Vinokurov, Yury; Yadav, Amit; Zaldarriaga, Matias; Zilic, Kyle

2010-07-01

We present the hardware and software systems implementing autonomous operation, distributed real-time monitoring, and control for the EBEX instrument. EBEX is a NASA-funded balloon-borne microwave polarimeter designed for a 14 day Antarctic flight that circumnavigates the pole. To meet its science goals the EBEX instrument autonomously executes several tasks in parallel: it collects attitude data and maintains pointing control in order to adhere to an observing schedule; tunes and operates up to 1920 TES bolometers and 120 SQUID amplifiers controlled by as many as 30 embedded computers; coordinates and dispatches jobs across an onboard computer network to manage this detector readout system; logs over 3 GiB/hour of science and housekeeping data to an onboard disk storage array; responds to a variety of commands and exogenous events; and downlinks multiple heterogeneous data streams representing a selected subset of the total logged data. Most of the systems implementing these functions have been tested during a recent engineering flight of the payload, and have proven to meet the target requirements. The EBEX ground segment couples uplink and downlink hardware to a client-server software stack, enabling real-time monitoring and command responsibility to be distributed across the public internet or other standard computer networks. Using the emerging dirfile standard as a uniform intermediate data format, a variety of front end programs provide access to different components and views of the downlinked data products. This distributed architecture was demonstrated operating across multiple widely dispersed sites prior to and during the EBEX engineering flight.

Earth Observation

NASA Image and Video Library

2013-07-04

ISS036-E-015342 (4 July 2013) --- A number of Quebec, Canada wildfires southeast of James Bay were recorded as part of a series of photographs taken and downlinked to Earth on July 4 by the Expedition 36 crew members aboard the International Space Station.

Earth Observation

NASA Image and Video Library

2013-07-04

ISS036-E-015335 (4 July 2013) --- A number of Quebec, Canada wildfires southeast of James Bay were recorded as part of a series of photographs taken and downlinked to Earth on July 4 by the Expedition 36 crew members aboard the International Space Station.

Opportunistic MSPA Demonstration #1: Final Report

NASA Astrophysics Data System (ADS)

Abraham, D. S.; Finley, S. G.; Heckman, D. P.; Lay, N. E.; Lush, C. M.; MacNeal, B. E.

2015-02-01

The Opportunistic Multiple Spacecraft Per Antenna (OMSPA) concept seeks to provide smallsat missions with a low-attributed-aperture-fee technique for obtaining routine downlink in a manner that is very low cost to the Deep Space Network (DSN). Unlike traditional MSPA in which the number of spacecraft that can be supported is limited by the number of available receivers, OMSPA makes use of a digital recorder at each station that is capable of capturing IF signals from every spacecraft in the antenna beam within the frequency bands of interest. When smallsat missions see one or more opportunities to intercept the traditionally scheduled antenna beam of a "host" spacecraft, they can transmit open loop during those opportunities. Via a secure Internet site, the smallsat mission operators can then retrieve relevant portions of the digital recording for subsequent demodulation and decoding or subscribe to a service that does it for them. The demonstration discussed in this article was intended to provide prospective smallsat users and the DSN, as the prospective service provider, with demonstrable proof that the OMSPA concept is, in fact, an operationally viable means for obtaining routine downlink telemetry. To do this, the demonstration began by treating Mars Odyssey as a "smallsat" and Mars Reconnaissance Orbiter (MRO) as the "host" spacecraft. Using a specially created Beam Intercept Planning System (BIPS) and a DSN 7-Day Schedule Cross-Comparison (7-DSC) tool, opportunities were identified when Mars Odyssey would be transmitting while in MRO's ground antenna beam. Existing Very Long Baseline Interferometry (VLBI) Science Receivers (VSRs) were used to record the Mars Odyssey downlink telemetry during these opportunities. The recordings were played back to a secure server outside the Flight Operations Network firewall, but inside the JPL firewall. The demonstration team's signal processing personnel retrieved the recordings from this secure server and downloaded them to a workstation containing an OMSPA Software Demodulator (OSD) tool that was developed to demodulate and decode the Mars Odyssey signal. Validation of the recovered data was then accomplished by comparing the transfer frames obtained through OMSPA with those recovered via Mars Odyssey's formally scheduled downlink. The demonstration successfully achieved its intended purpose. All of the above steps were accomplished within an operationally viable timeframe, with at least 99.95 percent of the transfer frames being successfully recovered from each demonstration recording.

Aspects of scintillation modelling in LEO-ground free-space optical communications

NASA Astrophysics Data System (ADS)

Moll, Florian

2017-10-01

Free-space optical communications can be used to transmit data from low Earth orbit satellites to ground with very high data rate. In the last section of the downlink, the electro-magnetic wave propagates through the turbulent atmosphere which is characterized by random index of refraction fluctuations. The propagating wave experiences phase distortions that lead to intensity scintillation in the aperture plane of the receiving telescope. For quantification, an appropriate scintillation model is needed. Approaches to analytically model the scintillation exist. Parameterization of the underlying turbulence profile (Cn2 profile) is however difficult. The Cn2 profiles are often site-specific and thus inappropriate or generic and thus too complex for a feasible deployment. An approach that directly models the scintillation effect based on measurements without claiming to be generic is therefore more feasible. Since measurements are sparse, a combination with existing theoretical framework is feasible to develop a new scintillation model that focuses on low earth orbit to ground free-space optical communications link design with direct detection. The paper addresses several questions one has to answer while analyzing the measurements data and selection of the theoretical models for the LEO downlink scenario. The first is the question of a suitable yet ease to use simple Cn2 profile. The HAP model is analyzed for its feasibility in this scenario since it includes a more realistic boundary layer profile decay than the HV model. It is found that the HAP model needs to be modified for a feasible deployment in the LEO downlink scenario for night time. The validity of the plane wave assumption in the downlink is discussed by model calculations of the scintillation index for a plane and Gaussian beam wave. Inaccuracies when using the plane earth model instead of the spherical earth model are investigated by analyzing the Rytov index. Impact of beam wander and non-ideal tracking are also discussed. Eventually, satellite measurements are discussed together with model calculations. It is found that the model calculation with the modified HAP turbulence profile fits the measurements. The plane wave assumption is valid for calculation of scintillation. The flat earth model is accurate enough to model scintillation over elevation when using the extended Rytov theory. The effect of beam wander is negligible. Further work needs to be carried out to elaborate a new scintillation model from the measurements and theory.

Closing the uplink/downlink loop on the new Horizons Mission to Pluto

NASA Astrophysics Data System (ADS)

Peterson, Joseph G.; Birath, Emma; Carcich, Brian; Harch, Ann

Commanding the payload on a spacecraft (“ uplink” sequencing and command generation) and processing the instrument data returned (“ downlink” data processing) are two primary functions of Science Operations on a mission. While vitally important, it is sometimes surprisingly difficult to connect data returned from a spacecraft to the corresponding commanding and sequencing information that created the data, especially when data processing is done via an automated science data pipeline and not via a manual process with humans in the loop. For a variety of reasons it is necessary to make such a connection and close this loop. Perhaps the most important reason is to ensure that all data asked for has arrived safely on the ground. This is especially critical when the mission must erase parts of the spacecraft memory to make room for new data; mistakes here can result in permanent loss of data. Additionally, there are often key pieces of information (such as intended observation target or certain instrument modes that are not included in housekeeping, etc.) that are known only at the time of commanding and never makes it down in the telemetry. Because missions like New Horizons strive to be frugal with how much telemetry is sent back to Earth, and the telemetry may not include unambiguous identifiers (like observation ids, etc.), connecting downlinked data with uplink command information in an automated way can require creative approaches and heuristics. In this paper, we describe how these challenges were overcome on the New Horizons Mission to Pluto. The system developed involves ingesting uplink information into a database and automatically correlating it with downlinked data products. This allows for more useful data searches and the ability to attach the original intent of each observation to the processed science data. Also a new data tracking tool is now being developed to help in planning data playback from the spacecraft and to ensu- e data is verified on the ground before being erased from spacecraft memory. The development of these tools and techniques have also uncovered powerful lessons-learned for future missions. At the early stages of the design of a mission's dataflow, the allocation of a few more bytes of telemetry can go a long way toward making the uplink to downlink loop even easier to close on the ground, simplifying ground systems for future missions.

The NASA Spacecraft Transponding Modem

NASA Technical Reports Server (NTRS)

Berner, Jeff B.; Kayalar, Selahattin; Perret, Jonathan D.

2000-01-01

A new deep space transponder is being developed by the Jet Propulsion Laboratory for NASA. The Spacecraft Transponding Modem (STM) implements the standard transponder functions and the channel service functions that have previously resided in spacecraft Command/Data Subsystems. The STM uses custom ASICs, MMICs, and MCMs to reduce the active device parts count to 70, mass to I kg, and volume to 524 cc. The first STMs will be flown on missions launching in the 2003 time frame. The STM tracks an X-band uplink signal and provides both X-band and Ka-band downlinks, either coherent or non-coherent with the uplink. A NASA standard Command Detector Unit is integrated into the STM, along with a codeblock processor and a hardware command decoder. The decoded command codeblocks are output to the spacecraft command/data subsystem. Virtual Channel 0 (VC-0) (hardware) commands are processed and output as critical controller (CRC) commands. Downlink telemetry is received from the spacecraft data subsystem as telemetry frames. The STM provides the following downlink coding options: the standard CCSDS (7-1/2) convolutional coding, ReedSolomon coding with interleave depths one and five, (15-1/6) convolutional coding, and Turbo coding with rates 1/3 and 1/6. The downlink symbol rates can be linearly ramped to match the G/T curve of the receiving station, providing up to a 1 dB increase in data return. Data rates range from 5 bits per second (bps) to 24 Mbps, with three modulation modes provided: modulated subcarrier (3 different frequencies provided), biphase-L modulated direct on carrier, and Offset QPSK. Also, the capability to generate one of four non-harmonically related telemetry beacon tones is provided, to allow for a simple spacecraft status monitoring scheme for cruise phases of missions. Three ranging modes are provided: standard turn around ranging, regenerative pseudo-noise (PN) ranging, and Differential One-way Ranging (DOR) tones. The regenerative ranging provides the capability of increasing the ground received ranging SNR by up to 30 dB. Two different avionics interfaces to the command/data subsystem's data bus are provided: a MIL STD 1553B bus or an industry standard PCI interface. Digital interfaces provide the capability to control antenna selection (e.g., switching between high gain and low gain antennas) and antenna pointing (for future steered Ka-band antennas).

Intergroup visual perspective-taking: Shared group membership impairs self-perspective inhibition but may facilitate perspective calculation.

PubMed

Simpson, Austin J; Todd, Andrew R

2017-09-01

Reasoning about what other people see, know, and want is essential for navigating social life. Yet, even neurodevelopmentally healthy adults make perspective-taking errors. Here, we examined how the group membership of perspective-taking targets (ingroup vs. outgroup) affects processes underlying visual perspective-taking. In three experiments using two bases of group identity (university affiliation and minimal groups), interference from one's own differing perspective (i.e., egocentric intrusion) was stronger when responding from an ingroup versus an outgroup member's perspective. Spontaneous perspective calculation, as indexed by interference from another's visual perspective when reporting one's own (i.e., altercentric intrusion), did not differ across target group membership in any of our experiments. Process-dissociation analyses, which aim to isolate automatic processes underlying altercentric-intrusion effects, further revealed negligible effects of target group membership on perspective calculation. Meta-analytically, however, there was suggestive evidence that shared group membership facilitates responding from others' perspectives when self and other perspectives are aligned. Copyright © 2017 Elsevier B.V. All rights reserved.

Optical filter including a sub-wavelength periodic structure and method of making

DOEpatents

Kaushik, Sumanth; Stallard, Brian R.

1998-01-01

An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof. The optical filter has applications to spectrometry, colorimetry, and chemical sensing.

Optical filter including a sub-wavelength periodic structure and method of making

DOEpatents

Kaushik, S.; Stallard, B.R.

1998-03-10

An optical filter includes a dielectric layer formed within a resonant optical cavity, with the dielectric layer having formed therein a sub-wavelength periodic structure to define, at least in part, a wavelength for transmission of light through the resonant optical cavity. The sub-wavelength periodic structure can be formed either by removing material from the dielectric layer (e.g. by etching through an electron-beam defined mask), or by altering the composition of the layer (e.g. by ion implantation). Different portions of the dielectric layer can be patterned to form one or more optical interference filter elements having different light transmission wavelengths so that the optical filter can filter incident light according to wavelength and/or polarization. For some embodiments, the optical filter can include a detector element in optical alignment with each optical interference filter element to quantify or measure the filtered light for analysis thereof. The optical filter has applications to spectrometry, colorimetry, and chemical sensing. 17 figs.

Magnetic annihilation of the dark mode in a strongly coupled bright-dark terahertz metamaterial.

PubMed

Manjappa, Manukumara; Turaga, Shuvan Prashant; Srivastava, Yogesh Kumar; Bettiol, Andrew Anthony; Singh, Ranjan

2017-06-01

Dark mode in metamaterials has become a vital component in determining the merit of the Fano type of interference in the system. Its strength dictates the enhancement and suppression in the amplitude and Q-factors of resulting resonance features. In this work, we experimentally probe the effect of strong near-field coupling on the strength of the dark mode in a concentrically aligned bright resonator and a dark split ring resonator (SRR) system exhibiting the classical analog of the electromagnetically induced transparency effect. An enhanced strong magnetic field between the bright-dark resonators destructively interferes with the inherent magnetic field of the dark mode to completely annihilate its effect in the coupled system. Moreover, the observed annihilation effect in the dark mode has a direct consequence on the disappearance of the SRR effect in the proposed system, wherein under the strong magnetic interactions, the LC resonance feature of the split ring resonator becomes invisible to the incident terahertz wave.

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation

NASA Astrophysics Data System (ADS)

Rabus, Dominik Gerhard; Hamacher, Michael; Heidrich, Helmut

2002-02-01

A racetrack shaped double ring resonator (DRR) filter is demonstrated with radii of 200 μm. The double ring resonator contains two -3 dB multimode interference (MMI) couplers for I/O coupling and a -13 dB codirectional coupler in between the rings. A free spectral range of 50 GHz has been realized. A simulation model has been developed to describe the DRR. As fabrication tolerances do not allow the realization of two identical rings with required nm-circumference accuracy in the resonator, a frequency alignment of the resonator is indispensable. The resonance frequency tuning is performed thermally using platinum resistors which have been placed on top of the waveguides in both rings. An on-off ratio increase has been achieved of more than 3 dB, resulting in a total on-off ratio larger than 18 dB. The frequency alignment is inevitable in the case of multiple coupled micro ring resonators.

Angular and Intensity Dependent Spectral Modulations in High Harmonics from N2

NASA Astrophysics Data System (ADS)

McFarland, Brian; Farrell, Joseph; Bucksbaum, Philip; Guehr, Markus

2009-05-01

The spectral amplitude and phase modulation of high harmonics (HHG) in molecules provides important clues to molecular structure and dynamics in strong laser fields. We have studied these effects in aligned N2. Earlier results of HHG experiments claimed that the spectral amplitude modulation was predominantly due to geometrical interference between the recombining electron and the highest occupied molecular orbital (HOMO) [1]. We report evidence that contradicts this simple view. We observe a phase jump accompanied by a spectral minimum for HHG in aligned N2. The minimum shifts to lower harmonics as the angle between the molecular axis and harmonic generation polarization increases, and shifts to higher harmonics with increasing harmonic generation intensity. The features observed cannot be fully explained by a geometrical model. We discuss alternative explanations involving multi orbital effects [2]. [0pt] [1] Lein et al., Phys. Rev. A, 66, 023805 (2002) [2] B. K. McFarland, J. P. Farrell, P. H. Bucksbaum and M. Gühr, Science 322, 1232 (2008)

Recombination Proteins Mediate Meiotic Spatial Chromosome Organization and Pairing

PubMed Central

Storlazzi, Aurora; Gargano, Silvana; Ruprich-Robert, Gwenael; Falque, Matthieu; David, Michelle; Kleckner, Nancy; Zickler, Denise

2010-01-01

SUMMARY Meiotic chromosome pairing involves not only recognition of homology but also juxtaposition of entire chromosomes in a topologically regular way. Analysis of filamentous fungus Sordaria macrospora reveals that recombination proteins Mer3, Msh4 and Mlh1 play direct roles in all of these aspects, in advance of their known roles in recombination. Absence of Mer3 helicase results in interwoven chromosomes, thereby revealing the existence of features that specifically ensure “entanglement avoidance”. Entanglements that remain at zygotene, i.e. “interlockings”, require Mlh1 for resolution, likely to eliminate constraining recombinational connections. Patterns of Mer3 and Msh4 foci along aligned chromosomes show that the double-strand breaks mediating homologous alignment have spatially separated ends, one localized to each partner axis, and that pairing involves interference among developing interhomolog interactions. We propose that Mer3, Msh4 and Mlh1 execute all of these roles during pairing by modulating the state of nascent double-strand break/partner DNA contacts within axis-associated recombination complexes. PMID:20371348

Sub-Diffraction Limited Writing based on Laser Induced Periodic Surface Structures (LIPSS).

PubMed

He, Xiaolong; Datta, Anurup; Nam, Woongsik; Traverso, Luis M; Xu, Xianfan

2016-10-10

Controlled fabrication of single and multiple nanostructures far below the diffraction limit using a method based on laser induced periodic surface structure (LIPSS) is presented. In typical LIPSS, multiple lines with a certain spatial periodicity, but often not well-aligned, were produced. In this work, well-controlled and aligned nanowires and nanogrooves with widths as small as 40 nm and 60 nm with desired orientation and length are fabricated. Moreover, single nanowire and nanogroove were fabricated based on the same mechanism for forming multiple, periodic structures. Combining numerical modeling and AFM/SEM analyses, it was found these nanostructures were formed through the interference between the incident laser radiation and the surface plasmons, the mechanism for forming LIPSS on a dielectric surface using a high power femtosecond laser. We expect that our method, in particular, the fabrication of single nanowires and nanogrooves could be a promising alternative for fabrication of nanoscale devices due to its simplicity, flexibility, and versatility.

Sub-Diffraction Limited Writing based on Laser Induced Periodic Surface Structures (LIPSS)

PubMed Central

He, Xiaolong; Datta, Anurup; Nam, Woongsik; Traverso, Luis M.; Xu, Xianfan

2016-01-01

Controlled fabrication of single and multiple nanostructures far below the diffraction limit using a method based on laser induced periodic surface structure (LIPSS) is presented. In typical LIPSS, multiple lines with a certain spatial periodicity, but often not well-aligned, were produced. In this work, well-controlled and aligned nanowires and nanogrooves with widths as small as 40 nm and 60 nm with desired orientation and length are fabricated. Moreover, single nanowire and nanogroove were fabricated based on the same mechanism for forming multiple, periodic structures. Combining numerical modeling and AFM/SEM analyses, it was found these nanostructures were formed through the interference between the incident laser radiation and the surface plasmons, the mechanism for forming LIPSS on a dielectric surface using a high power femtosecond laser. We expect that our method, in particular, the fabrication of single nanowires and nanogrooves could be a promising alternative for fabrication of nanoscale devices due to its simplicity, flexibility, and versatility. PMID:27721428

ISS NASA Social

NASA Image and Video Library

2013-02-20

A NASA Social participant asks a question to the astronauts onboard the International Space Station in a live downlink from the ISS at a NASA Social exploring science on the ISS at NASA Headquarters, Wednesday, Feb. 20, 2013 in Washington. Photo Credit: (NASA/Carla Cioffi)

Earth Observation

NASA Image and Video Library

2013-07-04

ISS036-E-015355 (4 July 2013) --- A number of Quebec, Canada wildfires near the Manicouagan Reservoir (seen at bottom center) were recorded in a series of photographs taken and downlinked to Earth on July 4 by the Expedition 36 crew members aboard the International Space Station.

Earth Observations taken by the Expedition 39 Crew

NASA Image and Video Library

2014-04-10

Earth observation taken by the Expedition 39 crew aboard the ISS. A portion of the docked Soyuz TMA-11M spacecraft is in view. Image was released by astronaut on Instagram and downlinked in folder: Personal photos and the Maldive islands.

A depolarization and attenuation experiment using the CTS satellite. [meteorological radar

NASA Technical Reports Server (NTRS)

Bostian, C. W.; Holt, S. B., Jr.; Kauffman, S. R.; Manus, E. A.; Marshall, R. E.; Stutzman, W. L.; Wiley, P. H.

1977-01-01

Rain attenuation and depolarization data collected on the communications technology satellite 11.7 GHz downlink, and changes made in equipment following rain leak damage to the parametric amplifier are discussed. A 15 GHz radar system is described.

The Telecommunications and Data Acquisition Report

NASA Technical Reports Server (NTRS)

Posner, E. C. (Editor)

1985-01-01

Developments in programs managed by the Jet Propulsion Laboratory's Office of Telecommunications and Data acquisition are discussed. Space communications, radio antennas, the Deep Space Network, antenna design, Project SETI, seismology, coding, very large scale integration, downlinking, and demodulation are among the topics covered.

Automatic Alignment of Displacement-Measuring Interferometer

NASA Technical Reports Server (NTRS)

Halverson, Peter; Regehr, Martin; Spero, Robert; Alvarez-Salazar, Oscar; Loya, Frank; Logan, Jennifer

2006-01-01

A control system strives to maintain the correct alignment of a laser beam in an interferometer dedicated to measuring the displacement or distance between two fiducial corner-cube reflectors. The correct alignment of the laser beam is parallel to the line between the corner points of the corner-cube reflectors: Any deviation from parallelism changes the length of the optical path between the reflectors, thereby introducing a displacement or distance measurement error. On the basis of the geometrical optics of corner-cube reflectors, the length of the optical path can be shown to be L = L(sub 0)cos theta, where L(sub 0) is the distance between the corner points and theta is the misalignment angle. Therefore, the measurement error is given by DeltaL = L(sub 0)(cos theta - 1). In the usual case in which the misalignment is small, this error can be approximated as DeltaL approximately equal to -L(sub 0)theta sup 2/2. The control system (see figure) is implemented partly in hardware and partly in software. The control system includes three piezoelectric actuators for rapid, fine adjustment of the direction of the laser beam. The voltages applied to the piezoelectric actuators include components designed to scan the beam in a circular pattern so that the beam traces out a narrow cone (60 microradians wide in the initial application) about the direction in which it is nominally aimed. This scan is performed at a frequency (2.5 Hz in the initial application) well below the resonance frequency of any vibration of the interferometer. The laser beam makes a round trip to both corner-cube reflectors and then interferes with the launched beam. The interference is detected on a photodiode. The length of the optical path is measured by a heterodyne technique: A 100- kHz frequency shift between the launched beam and a reference beam imposes, on the detected signal, an interferometric phase shift proportional to the length of the optical path. A phase meter comprising analog filters and specialized digital circuitry converts the phase shift to an indication of displacement, generating a digital signal proportional to the path length.

Vacuum-Compatible Wideband White Light and Laser Combiner Source System

NASA Technical Reports Server (NTRS)

Azizi, Alineza; Ryan, Daniel J.; Tang, Hong; Demers, Richard T.; Kadogawa, Hiroshi; An, Xin; Sun, George Y.

2010-01-01

For the Space Interferometry Mission (SIM) Spectrum Calibration Development Unit (SCDU) testbed, wideband white light is used to simulate starlight. The white light source mount requires extremely stable pointing accuracy (<3.2 microradians). To meet this and other needs, the laser light from a single-mode fiber was combined, through a beam splitter window with special coating from broadband wavelengths, with light from multimode fiber. Both lights were coupled to a photonic crystal fiber (PCF). In many optical systems, simulating a point star with broadband spectrum with stability of microradians for white light interferometry is a challenge. In this case, the cameras use the white light interference to balance two optical paths, and to maintain close tracking. In order to coarse align the optical paths, a laser light is sent into the system to allow tracking of fringes because a narrow band laser has a great range of interference. The design requirements forced the innovators to use a new type of optical fiber, and to take a large amount of care in aligning the input sources. The testbed required better than 1% throughput, or enough output power on the lowest spectrum to be detectable by the CCD camera (6 nW at camera). The system needed to be vacuum-compatible and to have the capability for combining a visible laser light at any time for calibration purposes. The red laser is a commercially produced 635-nm laser 5-mW diode, and the white light source is a commercially produced tungsten halogen lamp that gives a broad spectrum of about 525 to 800 nm full width at half maximum (FWHM), with about 1.4 mW of power at 630 nm. A custom-made beam splitter window with special coating for broadband wavelengths is used with the white light input via a 50-mm multi-mode fiber. The large mode area PCF is an LMA-8 made by Crystal Fibre (core diameter of 8.5 mm, mode field diameter of 6 mm, and numerical aperture at 625 nm of 0.083). Any science interferometer that needs a tracking laser fringe to assist in alignment can use this system.

Developments in Scanning Hall Probe Microscopy

NASA Astrophysics Data System (ADS)

Chouinard, Taras; Chu, Ricky; David, Nigel; Broun, David

2009-05-01

Low temperature scanning Hall probe microscopy is a sensitive means of imaging magnetic structures with high spatial resolution and magnetic flux sensitivity approaching that of a Superconducting Quantum Interference Device. We have developed a scanning Hall probe microscope with novel features, including highly reliable coarse positioning, in situ optimization of sensor-sample alignment and capacitive transducers for linear, long range positioning measurement. This has been motivated by the need to reposition accurately above fabricated nanostructures such as small superconducting rings. Details of the design and performance will be presented as well as recent progress towards time-resolved measurements with sub nanosecond resolution.

Surface-mount sapphire interferometric temperature sensor.

PubMed

Zhu, Yizheng; Wang, Anbo

2006-08-20

A fiber-optic high-temperature sensor is demonstrated by bonding a 45 degrees -polished single-crystal sapphire fiber on the surface of a sapphire wafer, whose optical thickness is temperature dependent and measured by white-light interferometry. A novel adhesive-free coupling between the silica and sapphire fibers is achieved by fusion splicing, and its performance is characterized. The sensor's interference signal is investigated for its dependence on angular alignment between the fiber and the wafer. A prototype sensor is tested to 1,170 degrees C with a resolution of 0.4 degrees C, demonstrating excellent potential for high-temperature measurement.

ATRX, a member of the SNF2 family of helicase/ATPases, is required for chromosome alignment and meiotic spindle organization in metaphase II stage mouse oocytes.

PubMed

De La Fuente, Rabindranath; Viveiros, Maria M; Wigglesworth, Karen; Eppig, John J

2004-08-01

ATRX is a centromeric heterochromatin binding protein belonging to the SNF2 family of helicase/ATPases with chromatin remodeling activity. Mutations in the human ATRX gene result in X-linked alpha-thalassaemia with mental retardation (ATRX) syndrome and correlate with changes in methylation of repetitive DNA sequences. We show here that ATRX also functions to regulate key stages of meiosis in mouse oocytes. At the germinal vesicle (GV) stage, ATRX was found associated with the perinucleolar heterochromatin rim in transcriptionally quiescent oocytes. Phosphorylation of ATRX during meiotic maturation is dependent upon calcium calmodulin kinase (CamKII) activity. Meiotic resumption also coincides with deacetylation of histone H4 at lysine 5 (H4K5 Ac) while ATRX and histone H3 methylated on lysine 9 (H3K9) remained bound to the centromeres and interstitial regions of condensing chromosomes, respectively. Inhibition of histone deacetylases (HDACs) with trichostatin A (TSA) disrupted ATRX binding to the centromeres of hyperacetylated chromosomes resulting in abnormal chromosome alignments at metaphase II (MII). Similarly, while selective ablation of ATRX by antibody microinjection and RNA interference (RNAi) had no effect on the progression of meiosis, it had severe consequences for the alignment of chromosomes on the metaphase II spindle. These results suggest that genome-wide epigenetic modifications such as global histone deacetylation are essential for the binding of ATRX to centromeric heterochromatin. Moreover, centromeric ATRX is required for correct chromosome alignment and organization of a bipolar meiotic metaphase II spindle.

CALIPSO Instrument OFF

Atmospheric Science Data Center

2013-12-05

... the 100MeV levels are above the 1 pfu, which requires the computer to be powered down.   Recovery planning has begun and will be ... Payload was returned to Data Acquisition and regular nightly science data downlinks following the Inclination Maneuver on April 16th at ...

Earth Observation

NASA Image and Video Library

2013-07-04

ISS036-E-015354 (4 July 2013) --- A number of Quebec, Canada wildfires near the Manicouagan Reservoir (seen at lower left) were recorded as part of a series of photographs taken and downlinked to Earth on July 4 by the Expedition 36 crew members aboard the International Space Station.

Going the Distance.

ERIC Educational Resources Information Center

Ambler, Marjane

1994-01-01

Describes efforts to utilize advances in telecommunications technology to provide distance education for tribal colleges that reflects tribal cultures. Indicates that planners have decided to establish uplinks at the colleges, instead of merely downlinks from remote sites, and that satellite technology will be utilized to reach as many…

Breakthrough Science Enabled by Regular Access to Orbits Beyond Earth

NASA Astrophysics Data System (ADS)

Gorjian, V.

2018-02-01

Regular launches to the Deep Space Gateway (DSG) will enable smallsats to access orbits not currently easily available to low cost missions. These orbits will allow great new science, especially when using the DSG as an optical hub for downlink.

Lessons Learned During Implementation and Early Operations of the DS1 Beacon Monitor Experiment

NASA Technical Reports Server (NTRS)

Sherwood, Rob; Wyatt, Jay; Hotz, Henry; Schlutsmeyer, Alan; Sue, Miles

1998-01-01

A new approach to mission operations will be flight validated on NASA's New Millennium Program Deep Space One (DS1) mission which launched in October 1998. The Beacon Monitor Operations Technology is aimed at decreasing the total volume of downlinked engineering telemetry by reducing the frequency of downlink and the volume of data received per pass. Cost savings are achieved by reducing the amount of routine telemetry processing and analysis performed by ground staff. The technology is required for upcoming NASA missions to Pluto, Europa, and possibly some other missions. With beacon monitoring, the spacecraft will assess its own health and will transmit one of four beacon messages each representing a unique frequency tone to inform the ground how urgent it is to track the spacecraft for telemetry. If all conditions are nominal, the tone provides periodic assurance to ground personnel that the mission is proceeding as planned without having to receive and analyze downlinked telemetry. If there is a problem, the tone will indicate that tracking is required and the resulting telemetry will contain a concise summary of what has occurred since the last telemetry pass. The primary components of the technology are a tone monitoring technology, AI-based software for onboard engineering data summarization, and a ground response system. In addition, there is a ground visualization system for telemetry summaries. This paper includes a description of the Beacon monitor concept, the trade-offs with adapting that concept as a technology experiment, the current state of the resulting implementation on DS1, and our lessons learned during the initial checkout phase of the mission. Applicability to future missions is also included.

Downlink Training Techniques for FDD Massive MIMO Systems: Open-Loop and Closed-Loop Training With Memory

NASA Astrophysics Data System (ADS)

Choi, Junil; Love, David J.; Bidigare, Patrick

2014-10-01

The concept of deploying a large number of antennas at the base station, often called massive multiple-input multiple-output (MIMO), has drawn considerable interest because of its potential ability to revolutionize current wireless communication systems. Most literature on massive MIMO systems assumes time division duplexing (TDD), although frequency division duplexing (FDD) dominates current cellular systems. Due to the large number of transmit antennas at the base station, currently standardized approaches would require a large percentage of the precious downlink and uplink resources in FDD massive MIMO be used for training signal transmissions and channel state information (CSI) feedback. To reduce the overhead of the downlink training phase, we propose practical open-loop and closed-loop training frameworks in this paper. We assume the base station and the user share a common set of training signals in advance. In open-loop training, the base station transmits training signals in a round-robin manner, and the user successively estimates the current channel using long-term channel statistics such as temporal and spatial correlations and previous channel estimates. In closed-loop training, the user feeds back the best training signal to be sent in the future based on channel prediction and the previously received training signals. With a small amount of feedback from the user to the base station, closed-loop training offers better performance in the data communication phase, especially when the signal-to-noise ratio is low, the number of transmit antennas is large, or prior channel estimates are not accurate at the beginning of the communication setup, all of which would be mostly beneficial for massive MIMO systems.

Replacing the CCSDS Telecommand Protocol with the Next Generation Uplink (NGU)

NASA Technical Reports Server (NTRS)

Kazz, Greg J.; Greenberg, Ed; Burleigh, Scott C.

2012-01-01

The current CCSDS Telecommand (TC) Recommendations 1-3 have essentially been in use since the early 1960s. The purpose of this paper is to propose a successor protocol to TC. The current CCSDS recommendations can only accommodate telecommand rates up to approximately 1 mbit/s. However today's spacecraft are storehouses for software including software for Field Programmable Gate Arrays (FPGA) which are rapidly replacing unique hardware systems. Changes to flight software occasionally require uplinks to deliver very large volumes of data. In the opposite direction, high rate downlink missions that use acknowledged CCSDS File Delivery Protocol (CFDP)4 will increase the uplink data rate requirements. It is calculated that a 5 mbits/s downlink could saturate a 4 kbits/s uplink with CFDP downlink responses: negative acknowledgements (NAKs), FINISHs, End-of-File (EOF), Acknowledgements (ACKs). Moreover, it is anticipated that uplink rates of 10 to 20 mbits/s will be required to support manned missions. The current TC recommendations cannot meet these new demands. Specifically, they are very tightly coupled to the Bose-Chaudhuri-Hocquenghem (BCH) code in Ref. 2. This protocol requires that an uncorrectable BCH codeword delimit the TC frame and terminate the randomization process. This method greatly limits telecom performance since only the BCH code can support the protocol. More modern techniques such as the CCSDS Low Density Parity Check (LDPC)5 codes can provide a minimum performance gain of up to 6 times higher command data rates as long as sufficient power is available in the data. This paper will describe the proposed protocol format, trade-offs, and advantages offered, along with a discussion of how reliable communications takes place at higher nominal rates.

Building an Energy-efficient Uplink and Downlink Delay Aware TDM-PON System

NASA Astrophysics Data System (ADS)

Newaz, S. H. Shah; Jang, Min Seok; Alaelddin, Fuad Yousif Mohammed; Lee, Gyu Myoung; Choi, Jun Kyun

2016-05-01

With the increasing concern over the energy expenditure due to rapid ICT expansion and growth of Internet traffic volume, there is a growing trend towards developing energy-efficient ICT solutions. Passive Optical Network (PON), which is regarded as a key enabler to facilitate high speed broadband connection to individual subscribers, is considered as one of the energy-efficient access network technologies. However, an immense amount of research effort can be noticed in academia and industries to make PON more energy-efficient. In this paper, we aim at improving energy saving performance of Time Division Multiplexing (TDM)-PON, which is the most widely deployed PON technology throughout the world. A commonly used approach to make TDM-PON energy-efficient is to use sleep mode in Optical Network Units (ONUs), which are the customer premises equipment of a TDM-PON system. However, there is a strong trade-off relationship between traffic delay performance of an ONU and its energy saving (the longer the sleep interval length of an ONU, the lower its energy consumption, but the higher the traffic delay, and vice versa). In this paper, we propose an Energy-efficient Uplink and Downlink Delay Aware (EUDDA) scheme for TDM-PON system. The prime object of EUDDA is to meet both downlink and uplink traffic delay requirement while maximizing energy saving performance of ONUs as much as possible. In EUDDA, traffic delay requirement is given more priority over energy saving. Even so, it still can improve energy saving of ONUs noticeably. We evaluate performance of EUDDA in front of two existing solutions in terms of traffic delay, jitter, and ONU energy consumption. The performance results show that EUDDA significantly outperforms the other existing solutions.

Deep-Space Ka-Band Flight Experience

NASA Astrophysics Data System (ADS)

Morabito, D. D.

2017-11-01

Lower frequency bands have become more congested in allocated bandwidth as there is increased competition between flight projects and other entities. Going to higher frequency bands offers significantly more bandwidth, allowing for the use of much higher data rates. However, Ka-band is more susceptible to weather effects than lower frequency bands currently used for most standard downlink telemetry operations. Future or prospective flight projects considering deep-space Ka-band (32-GHz) telemetry data links have expressed an interest in understanding past flight experience with received Ka-band downlink performance. Especially important to these flight projects is gaining a better understanding of weather effects from the experience of current or past missions that operated Ka-band radio systems. We will discuss the historical flight experience of several Ka-band missions starting from Mars Observer in 1993 up to present-day deep-space missions such as Kepler. The study of historical Ka-band flight experience allows one to recommend margin policy for future missions. Of particular interest, we will review previously reported-on flight experience with the Cassini spacecraft Ka-band radio system that has been used for radio science investigations as well as engineering studies from 2004 to 2015, when Cassini was in orbit around the planet Saturn. In this article, we will focus primarily on the Kepler spacecraft Ka-band link, which has been used for operational telemetry downlink from an Earth trailing orbit where the spacecraft resides. We analyzed the received Ka-band signal level data in order to characterize link performance over a wide range of weather conditions and as a function of elevation angle. Based on this analysis of Kepler and Cassini flight data, we found that a 4-dB margin with respect to adverse conditions ensures that we achieve at least a 95 percent data return.

Robot Sequencing and Visualization Program (RSVP)

NASA Technical Reports Server (NTRS)

Cooper, Brian K.; Maxwell,Scott A.; Hartman, Frank R.; Wright, John R.; Yen, Jeng; Toole, Nicholas T.; Gorjian, Zareh; Morrison, Jack C

2013-01-01

The Robot Sequencing and Visualization Program (RSVP) is being used in the Mars Science Laboratory (MSL) mission for downlink data visualization and command sequence generation. RSVP reads and writes downlink data products from the operations data server (ODS) and writes uplink data products to the ODS. The primary users of RSVP are members of the Rover Planner team (part of the Integrated Planning and Execution Team (IPE)), who use it to perform traversability/articulation analyses, take activity plan input from the Science and Mission Planning teams, and create a set of rover sequences to be sent to the rover every sol. The primary inputs to RSVP are downlink data products and activity plans in the ODS database. The primary outputs are command sequences to be placed in the ODS for further processing prior to uplink to each rover. RSVP is composed of two main subsystems. The first, called the Robot Sequence Editor (RoSE), understands the MSL activity and command dictionaries and takes care of converting incoming activity level inputs into command sequences. The Rover Planners use the RoSE component of RSVP to put together command sequences and to view and manage command level resources like time, power, temperature, etc. (via a transparent realtime connection to SEQGEN). The second component of RSVP is called HyperDrive, a set of high-fidelity computer graphics displays of the Martian surface in 3D and in stereo. The Rover Planners can explore the environment around the rover, create commands related to motion of all kinds, and see the simulated result of those commands via its underlying tight coupling with flight navigation, motor, and arm software. This software is the evolutionary replacement for the Rover Sequencing and Visualization software used to create command sequences (and visualize the Martian surface) for the Mars Exploration Rover mission.

Two-dimensional wavelength routing for transparent optical wireless networking

NASA Astrophysics Data System (ADS)

Shi, Haiyan; Liang, Kefei; Sheard, Stephen J.; O'Brien, Dominic C.; Faulkner, Grahame E.

2005-08-01

In this article a novel system architecture that uses a combination of wavelength and spatial diversity for indoor infrared wireless communications is presented. This configuration promises to fully exploit the available bandwidth of optics and demonstrate all-optical networking. Electronic processing is restricted to mobile terminals, with base stations potentially remaining passive, without any conversion between optics and electronics. For the downlink, multiple transmitter beams with different wavelengths are steered from the fiber infrastructure through the base station to mobile terminals located in different positions. An optimum combination of diffractive optics and reflective optics (a diffraction grating and an array of mirrors) can flexibly steer each transmitter beam and enable full control over the required coverage pattern. For the uplink, in the transmitter, another grating and an array of mirrors can direct multiple beams upward from different mobile users toward the base station. System simulation shows that the downlink has the potential to approach 10 Gbit/s, while maintaining wide-area coverage (such as in a room of 3m×4m×4m) with the help of fine optical tracking. System modeling indicates that the uplink is more susceptible to power losses than the downlink, but the utilization of dynamic beam steering in the uplink can suppress power losses to a tolerable level (e.g. below 30dB). An array of 16 mirrors has been designed to implement point-to-point beam steering in a room of 3m×1m×1m. Two-dimensional coverage patterns measured at a distance of 0.5 m and 1.5 m coincide with simulation results. Operation at 1 Gbit/s has been demonstrated successfully for tracking in two dimensions.

An analysis of the low-earth-orbit communications environment

NASA Astrophysics Data System (ADS)

Diersing, Robert Joseph

Advances in microprocessor technology and availability of launch opportunities have caused interest in low-earth-orbit satellite based communications systems to increase dramatically during the past several years. In this research the capabilities of two low-cost, store-and-forward LEO communications satellites operating in the public domain are examined--PACSAT-1 (operated by the Radio Amateur Satellite Corporation) and UoSAT-3 (operated by the University of Surrey, England, Electrical Engineering Department). The file broadcasting and file transfer facilities are examined in detail and a simulation model of the downlink traffic pattern is developed. The simulator will aid the assessment of changes in design and implementation for other systems. The development of the downlink traffic simulator is based on three major parts. First, is a characterization of the low-earth-orbit operating environment along with preliminary measurements of the PACSAT-1 and UoSAT-3 systems including: satellite visibility constraints on communications, monitoring equipment configuration, link margin computations, determination of block and bit error rates, and establishing typical data capture rates for ground stations using computer-pointed directional antennas and fixed omni-directional antennas. Second, arrival rates for successful and unsuccessful file server connections are established along with transaction service times. Downlink traffic has been further characterized by measuring: frame and byte counts for all data-link layer traffic; 30-second interval average response time for all traffic and for file server traffic only; file server response time on a per-connection basis; and retry rates for information and supervisory frames. Finally, the model is verified by comparison with measurements of actual traffic not previously used in the model building process. The simulator is then used to predict operation of the PACSAT-1 satellite with modifications to the original design.

View of the MRM2/Poisk

NASA Image and Video Library

2009-11-21

ISS021-E-030653 (21 Nov. 2009) --- One of the newest pieces of hardware docked with the International Space Station is the Mini Research Module 2 (MRM-2), featured in this electronic still image downlinked by the Expedition 21 crew members during flight day six activities.

An Overview of the Beacon Monitor Operations Technology

NASA Technical Reports Server (NTRS)

Sue, Miles K.; Wyatt, E. Jay; Foster, Mike; Schlutsmeyer, Alan; Sherwood, Rob

1997-01-01

This paper summarizes the end-to-end design of a technology for low cost mission operations. Cost savings is achieved by reducing the total volume of downlinked engineering telemetry by decreasing the frequency of telemetry acquisition and the volume of data received per pass.

Mariner Venus Mercury 1973 S/X-band experiment

NASA Technical Reports Server (NTRS)

Levy, G. S.

1977-01-01

The S/X-band experiment on the Mariner Venus/Mercury 1973 spacecraft constituted a unique opportunity to demonstrate the capability of an X-band downlink coherent with the normal S-band downlink. This was both a technological and scientific experiment, and the results indicated that it was successful in both cases. Analysis of the tracking data shows that the new S/X data type was capable of reducing the miss distance at the planet Mercury by 80% (post-processed data). The use of S/X electron content was demonstrated by comparison with Faraday rotation data. An X-band turnaround telemetry experiment showed the feasibility of a planetary X-band link. In the science area, the model atmospheric environment of Venus was refined. The ionosphere of the planet was measured to a higher accuracy than before, and the value of the dual-frequency link for measuring the scale size of turbulence was demonstrated. The estimate of the scale size was increased from 100 m to above 5 km.

Autonomy enables new science missions

NASA Astrophysics Data System (ADS)

Doyle, Richard J.; Gor, Victoria; Man, Guy K.; Stolorz, Paul E.; Chapman, Clark; Merline, William J.; Stern, Alan

1997-01-01

The challenge of space flight in NASA's future is to enable smaller, more frequent and intensive space exploration at much lower total cost without substantially decreasing mission reliability, capability, or the scientific return on investment. The most effective way to achieve this goal is to build intelligent capabilities into the spacecraft themselves. Our technological vision for meeting the challenge of returning quality science through limited communication bandwidth will actually put scientists in a more direct link with the spacecraft than they have enjoyed to date. Technologies such as pattern recognition and machine learning can place a part of the scientist's awareness onboard the spacecraft to prioritize downlink or to autonomously trigger time-critical follow-up observations-particularly important in flyby missions-without ground interaction. Onboard knowledge discovery methods can be used to include candidate discoveries in each downlink for scientists' scrutiny. Such capabilities will allow scientists to quickly reprioritize missions in a much more intimate and efficient manner than is possible today. Ultimately, new classes of exploration missions will be enabled.

Low-Complexity User Selection for Rate Maximization in MIMO Broadcast Channels with Downlink Beamforming

PubMed Central

Silva, Adão; Gameiro, Atílio

2014-01-01

We present in this work a low-complexity algorithm to solve the sum rate maximization problem in multiuser MIMO broadcast channels with downlink beamforming. Our approach decouples the user selection problem from the resource allocation problem and its main goal is to create a set of quasiorthogonal users. The proposed algorithm exploits physical metrics of the wireless channels that can be easily computed in such a way that a null space projection power can be approximated efficiently. Based on the derived metrics we present a mathematical model that describes the dynamics of the user selection process which renders the user selection problem into an integer linear program. Numerical results show that our approach is highly efficient to form groups of quasiorthogonal users when compared to previously proposed algorithms in the literature. Our user selection algorithm achieves a large portion of the optimum user selection sum rate (90%) for a moderate number of active users. PMID:24574928

Electronic Still Camera Project on STS-48

NASA Technical Reports Server (NTRS)

1991-01-01

On behalf of NASA, the Office of Commercial Programs (OCP) has signed a Technical Exchange Agreement (TEA) with Autometric, Inc. (Autometric) of Alexandria, Virginia. The purpose of this agreement is to evaluate and analyze a high-resolution Electronic Still Camera (ESC) for potential commercial applications. During the mission, Autometric will provide unique photo analysis and hard-copy production. Once the mission is complete, Autometric will furnish NASA with an analysis of the ESC s capabilities. Electronic still photography is a developing technology providing the means by which a hand held camera electronically captures and produces a digital image with resolution approaching film quality. The digital image, stored on removable hard disks or small optical disks, can be converted to a format suitable for downlink transmission, or it can be enhanced using image processing software. The on-orbit ability to enhance or annotate high-resolution images and then downlink these images in real-time will greatly improve Space Shuttle and Space Station capabilities in Earth observations and on-board photo documentation.

Design concepts and performance of NASA X-band (7162 MHz/8415 MHz) transponder for deep-space spacecraft applications

NASA Technical Reports Server (NTRS)

Mysoor, N. R.; Perret, J. D.; Kermode, A. W.

1991-01-01

The design concepts and measured performance characteristics are summarized of an X band (7162 MHz/8415 MHz) breadboard deep space transponder (DSP) for future spacecraft applications, with the first use scheduled for the Comet Rendezvous Asteroid Flyby (CRAF) and Cassini missions in 1995 and 1996, respectively. The DST consists of a double conversion, superheterodyne, automatic phase tracking receiver, and an X band (8415 MHz) exciter to drive redundant downlink power amplifiers. The receiver acquires and coherently phase tracks the modulated or unmodulated X band (7162 MHz) uplink carrier signal. The exciter phase modulates the X band (8415 MHz) downlink signal with composite telemetry and ranging signals. The receiver measured tracking threshold, automatic gain control, static phase error, and phase jitter characteristics of the breadboard DST are in good agreement with the expected performance. The measured results show a receiver tracking threshold of -158 dBm and a dynamic signal range of 88 dB.

Comparisons between Common and Dedicated Reference Signals for MIMO Multiplexing Using Precoding in Evolved UTRA Downlink

NASA Astrophysics Data System (ADS)

Taoka, Hidekazu; Kishiyama, Yoshihisa; Higuchi, Kenichi; Sawahashi, Mamoru

This paper presents comparisons between common and dedicated reference signals (RSs) for channel estimation in MIMO multiplexing using codebook-based precoding for orthogonal frequency division multiplexing (OFDM) radio access in the Evolved UTRA downlink with frequency division duplexing (FDD). We clarify the best RS structure for precoding-based MIMO multiplexing based on comparisons of the structures in terms of the achievable throughput taking into account the overhead of the common and dedicated RSs and the precoding matrix indication (PMI) signal. Based on extensive simulations on the throughput in 2-by-2 and 4-by-4 MIMO multiplexing with precoding, we clarify that channel estimation based on common RSs multiplied with the precoding matrix indicated by the PMI signal achieves higher throughput compared to that using dedicated RSs irrespective of the number of spatial multiplexing streams when the number of available precoding matrices, i.e., the codebook size, is less than approximately 16 and 32 for 2-by-2 and 4-by-4 MIMO multiplexing, respectively.

Low-Complexity, Digital Encoder/Modulator Developed for High-Data-Rate Satellite B-ISDN Applications

NASA Technical Reports Server (NTRS)

1996-01-01

The Space Electronics Division at the NASA Lewis Research Center is developing advanced electronic technologies for the space communications and remote sensing systems of tomorrow. As part of the continuing effort to advance the state-of-the-art in satellite communications and remote sensing systems, Lewis developed a low-cost, modular, programmable, and reconfigurable all-digital encoder-modulator (DEM) for medium- to high-data-rate radiofrequency communication links. The DEM is particularly well suited to high-data-rate downlinks to ground terminals or direct data downlinks from near-Earth science platforms. It can support data rates up to 250 megabits per second (Mbps) and several modulation schemes, including the traditional binary phase-shift keying (BPSK) and quadrature phase-shift keying (QPSK) modes, as well as higher order schemes such as 8 phase-shift keying (8PSK) and 16 quadrature amplitude modulation (16QAM). The DEM architecture also can precompensate for channel disturbances and alleviate amplitude degradations caused by nonlinear transponder characteristics.

Development and experimental validation of downlink multiuser MIMO-OFDM in gigabit wireless LAN systems

NASA Astrophysics Data System (ADS)

Ishihara, Koichi; Asai, Yusuke; Kudo, Riichi; Ichikawa, Takeo; Takatori, Yasushi; Mizoguchi, Masato

2013-12-01

Multiuser multiple-input multiple-output (MU-MIMO) has been proposed as a means to improve spectrum efficiency for various future wireless communication systems. This paper reports indoor experimental results obtained for a newly developed and implemented downlink (DL) MU-MIMO orthogonal frequency division multiplexing (OFDM) transceiver for gigabit wireless local area network systems in the microwave band. In the transceiver, the channel state information (CSI) is estimated at each user and fed back to an access point (AP) on a real-time basis. At the AP, the estimated CSI is used to calculate the transmit beamforming weight for DL MU-MIMO transmission. This paper also proposes a recursive inverse matrix computation scheme for computing the transmit weight in real time. Experiments with the developed transceiver demonstrate its feasibility in a number of indoor scenarios. The experimental results clarify that DL MU-MIMO-OFDM transmission can achieve a 972-Mbit/s transmission data rate with simple digital signal processing of single-antenna users in an indoor environment.

Tri-state delta modulation system for Space Shuttle digital TV downlink

NASA Technical Reports Server (NTRS)

Udalov, S.; Huth, G. K.; Roberts, D.; Batson, B. H.

1981-01-01

Future requirements for Shuttle Orbiter downlink communication may include transmission of digital video which, in addition to black and white, may also be either field-sequential or NTSC color format. The use of digitized video could provide for picture privacy at the expense of additional onboard hardware, together with an increased bandwidth due to the digitization process. A general objective for the Space Shuttle application is to develop a digitization technique that is compatible with data rates in the 20-30 Mbps range but still provides good quality pictures. This paper describes a tri-state delta modulation/demodulation (TSDM) technique which is a good compromise between implementation complexity and performance. The unique feature of TSDM is that it provides for efficient run-length encoding of constant-intensity segments of a TV picture. Axiomatix has developed a hardware implementation of a high-speed TSDM transmitter and receiver for black-and-white TV and field-sequential color. The hardware complexity of this TSDM implementation is summarized in the paper.

An onboard data analysis method to track the seasonal polar caps on Mars

USGS Publications Warehouse

Wagstaff, K.L.; Castano, R.; Chien, S.; Ivanov, A.B.; Pounders, E.; Titus, T.N.; ,

2005-01-01

The Martian seasonal CO2 ice caps advance and retreat each year. They are currently studied using instruments such as the THermal EMission Imaging System (THEMIS), a visible and infra-red camera on the Mars Odyssey spacecraft [1]. However, each image must be downlinked to Earth prior to analysis. In contrast, we have developed the Bimodal Image Temperature (BIT) histogram analysis method for onboard detection of the cap edge, before transmission. In downlink-limited scenarios when the entire image cannot be transmitted, the location of the cap edge can still be identified and sent to Earth. In this paper, we evaluate our method on uncalibrated THEMIS data and find 1) agreement with manual cap edge identifications to within 28.2 km, and 2) high accuracy even with a smaller analysis window, yielding large reductions in memory requirements. This algorithm is currently being considered as a capability enhancement for the Odyssey second extended mission, beginning in fall 2006.

Onboard Detection of Active Canadian Sulfur Springs: A Europa Analogue

NASA Technical Reports Server (NTRS)

Castano, Rebecca; Wagstaff, Kiri; Gleeson, Damhnait; Pappalardo, Robert; Chien, Steve; Tran, Daniel; Scharenbroich, Lucas; Moghaddam, Baback; Tang, Benyang; Bue, Brian;

Method for traceable measurement of LTE signals

NASA Astrophysics Data System (ADS)

Sunder Dash, Soumya; Pythoud, Frederic; Leuchtmann, Pascal; Leuthold, Juerg

2018-04-01

This contribution presents a reference setup to measure the power of the cell-specific resource elements present in downlink long term evolution (LTE) signals in a way that the measurements are traceable to the international system of units. This setup can be used to calibrate the LTE code-selective field probes that are used to measure the radiation of base stations for mobile telephony. It can also be used to calibrate LTE signal generators and receivers. The method is based on traceable scope measurements performed directly at the output of a measuring antenna. It implements offline digital signal processing demodulation algorithms that consider the digital down-conversion, timing synchronization, frequency synchronization, phase synchronization and robust LTE cell identification to produce the downlink time-frequency LTE grid. Experimental results on conducted test scenarios, both single-input-single-output and multiple-input-multiple-output antenna configuration, show promising results confirming measurement uncertainties of the order of 0.05 dB with a coverage factor of 2.

Mutual coupling, channel model, and BER for curvilinear antenna arrays

NASA Astrophysics Data System (ADS)

Huang, Zhiyong

This dissertation introduces a wireless communications system with an adaptive beam-former and investigates its performance with different antenna arrays. Mutual coupling, real antenna elements and channel models are included to examine the system performance. In a beamforming system, mutual coupling (MC) among the elements can significantly degrade the system performance. However, MC effects can be compensated if an accurate model of mutual coupling is available. A mutual coupling matrix model is utilized to compensate mutual coupling in the beamforming of a uniform circular array (UCA). Its performance is compared with other models in uplink and downlink beamforming scenarios. In addition, the predictions are compared with measurements and verified with results from full-wave simulations. In order to accurately investigate the minimum mean-square-error (MSE) of an adaptive array in MC, two different noise models, the environmental and the receiver noise, are modeled. The minimum MSEs with and without data domain MC compensation are analytically compared. The influence of mutual coupling on the convergence is also examined. In addition, the weight compensation method is proposed to attain the desired array pattern. Adaptive arrays with different geometries are implemented with the minimum MSE algorithm in the wireless communications system to combat interference at the same frequency. The bit-error-rate (BER) of systems with UCA, uniform rectangular array (URA) and UCA with center element are investigated in additive white Gaussian noise plus well-separated signals or random direction signals scenarios. The output SINR of an adaptive array with multiple interferers is analytically examined. The influence of the adaptive algorithm convergence on the BER is investigated. The UCA is then investigated in a narrowband Rician fading channel. The channel model is built and the space correlations are examined. The influence of the number of signal paths, number of the interferers, Doppler spread and convergence are investigated. The tracking mode is introduced to the adaptive array system, and it further improves the BER. The benefit of using faster data rate (wider bandwidth) is discussed. In order to have better performance in a 3D space, the geometries of uniform spherical array (USAs) are presented and different configurations of USAs are discussed. The LMS algorithm based on temporal a priori information is applied to UCAs and USAs to beamform the patterns. Their performances are compared based on simulation results. Based on the analytical and simulation results, it can be concluded that mutual coupling slightly influences the performance of the adaptive array in communication systems. In addition, arrays with curvilinear geometries perform well in AWGN and fading channels.

Diagnosing the Role of Alfvén Waves in Magnetosphere-Ionosphere Coupling: Swarm Observations of Large Amplitude Nonstationary Magnetic Perturbations During an Interval of Northward IMF

NASA Astrophysics Data System (ADS)

Pakhotin, I. P.; Mann, I. R.; Lysak, R. L.; Knudsen, D. J.; Gjerloev, J. W.; Rae, I. J.; Forsyth, C.; Murphy, K. R.; Miles, D. M.; Ozeke, L. G.; Balasis, G.

2018-01-01

High-resolution multispacecraft Swarm data are used to examine magnetosphere-ionosphere coupling during a period of northward interplanetary magnetic field (IMF) on 31 May 2014. The observations reveal a prevalence of unexpectedly large amplitude (>100 nT) and time-varying magnetic perturbations during the polar passes, with especially large amplitude magnetic perturbations being associated with large-scale downward field-aligned currents. Differences between the magnetic field measurements sampled at 50 Hz from Swarm A and C, approximately 10 s apart along track, and the correspondence between the observed electric and magnetic fields at 16 samples per second, provide significant evidence for an important role for Alfvén waves in magnetosphere-ionosphere coupling even during northward IMF conditions. Spectral comparison between the wave E- and B-fields reveals a frequency-dependent phase difference and amplitude ratio consistent with interference between incident and reflected Alfvén waves. At low frequencies, the E/B ratio is in phase with an amplitude determined by the Pedersen conductance. At higher frequencies, the amplitude and phase change as a function of frequency in good agreement with an ionospheric Alfvén resonator model including Pedersen conductance effects. Indeed, within this Alfvén wave incidence, reflection, and interference paradigm, even quasi-static field-aligned currents might be reasonably interpreted as very low frequency (ω → 0) Alfvén waves. Overall, our results not only indicate the importance of Alfvén waves for magnetosphere-ionosphere coupling but also demonstrate a method for using Swarm data for the innovative experimental diagnosis of Pedersen conductance from low-Earth orbit satellite measurements.

Reduction of a grid moiré pattern by integrating a carbon-interspaced high precision x-ray grid with a digital radiographic detector.

PubMed

Yoon, Jai-Woong; Park, Young-Guk; Park, Chun-Joo; Kim, Do-Il; Lee, Jin-Ho; Chung, Nag-Kun; Choe, Bo-Young; Suh, Tae-Suk; Lee, Hyoung-Koo

2007-11-01

The stationary grid commonly used with a digital x-ray detector causes a moiré interference pattern due to the inadequate sampling of the grid shadows by the detector pixels. There are limitations with the previous methods used to remove the moiré such as imperfect electromagnetic interference shielding and the loss of image information. A new method is proposed for removing the moiré pattern by integrating a carbon-interspaced high precision x-ray grid with high grid line uniformity with the detector for frequency matching. The grid was aligned to the detector by translating and rotating the x-ray grid with respect to the detector using microcontrolled alignment mechanism. The gap between the grid and the detector surface was adjusted with micrometer precision to precisely match the projected grid line pitch to the detector pixel pitch. Considering the magnification of the grid shadows on the detector plane, the grids were manufactured such that the grid line frequency was slightly higher than the detector sampling frequency. This study examined the factors that affect the moiré pattern, particularly the line frequency and displacement. The frequency of the moiré pattern was found to be sensitive to the angular displacement of the grid with respect to the detector while the horizontal translation alters the phase but not the moiré frequency. The frequency of the moiré pattern also decreased with decreasing difference in frequency between the grid and the detector, and a moiré-free image was produced after complete matching for a given source to detector distance. The image quality factors including the contrast, signal-to-noise ratio and uniformity in the images with and without the moiré pattern were investigated.

Telemetry downlink interfaces and level-zero processing

NASA Technical Reports Server (NTRS)

Horan, S.; Pfeiffer, J.; Taylor, J.

1991-01-01

The technical areas being investigated are as follows: (1) processing of space to ground data frames; (2) parallel architecture performance studies; and (3) parallel programming techniques. Additionally, the University administrative details and the technical liaison between New Mexico State University and Goddard Space Flight Center are addressed.

Earth Observation

NASA Image and Video Library

2013-07-03

ISS036-E-015292 (3 July 2013) --- A number of Quebec, Canada wildfires southeast of James Bay were recorded as part of a series of photographs taken and downlinked to Earth on July 3-4 by the Expedition 36 crew members aboard the International Space Station. This image was recorded on July 3.

78 FR 21555 - Signal Booster Rules

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-11

... needed, such as when the device approaches the base station with which it is communicating; (5) be..., the signals received from base, fixed, mobile, or portable stations, with no change in frequency or... oscillations in uplink and downlink bands (such as may result from insufficient isolation between the antennas...

Electromagnetic characteristics of systems of prolate and oblate ellipsoids

NASA Astrophysics Data System (ADS)

Karimi, Pouyan; Amiri-Hezaveh, Amirhossein; Ostoja-Starzewski, Martin; Jin, Jian-Ming

2017-11-01

The present study suggests a novel model for simulating electromagnetic characteristics of spheroidal nanofillers. The electromagnetic interference shielding efficiency of prolate and oblate ellipsoids in the X-band frequency range is studied. Different multilayered nanocomposite configurations incorporating carbon nanotubes, graphene nanoplatelets, and carbon blacks are fabricated and tested. The best performance for a specific thickness is observed for the multilayered composite with a gradual increase in the thickness and electrical conductivity of layers. The simulation results based on the proposed model are shown to be in good agreement with the experimental data. The effect of filler alignment on shielding efficiency is also studied by using the nematic order parameter. The ability of a nanocomposite to shield the incident power is found to decrease by increasing alignment especially for high volume fractions of prolate fillers. The interaction of the electromagnetic wave and the fillers is mainly affected by the polarization of the electric field; when the electric field is perpendicular to the equatorial axis of a spheroid, the interaction is significantly reduced and results in a lower shielding efficiency. Apart from the filler alignment, size polydispersity is found to have a significant effect on reflected and transmitted powers. It is demonstrated that the nanofillers with a higher aspect ratio mainly contribute to the shielding performance. The results are of interest in both shielding structures and microwave absorbing materials.

Effect of Serum and Insulin Modulation on the Organization and Morphology of Matrix Synthesized by Bovine Corneal Stromal Cells

PubMed Central

Bueno, Ericka M.; Saeidi, Nima; Melotti, Suzanna

2009-01-01

The in vitro production of highly organized collagen fibrils by corneal keratocytes in a three-dimensional scaffold-free culture system presents a unique opportunity for the direct observation of organized matrix formation. The objective of this investigation was to develop such a culture system in a glass substrate (for optical accessibility) and to directly examine the effect of reducing serum and/or increasing insulin on the stratification and secretion of aligned matrix by fourth- to fifth-passage bovine corneal stromal keratocytes. Medium concentrations of 0%, 1%, or 10% fetal bovine serum and 0% or 1% insulin–transferrin–selenium were investigated. High-resolution differential interference contrast microscopy, quick-freeze/deep-etch, and conventional transmission electron microscopy were used to monitor the evolution, morphology, and ultrastructure of the cell–matrix constructs. In a medium containing 1% each of serum and insulin–transferrin–selenium, stromal cells stratified and secreted abundant and locally aligned matrix, generating the thickest cell–matrix constructs (allowing handling with forceps). The results of this study have the potential to significantly advance the field of developmental functional engineering of load-bearing tissues by (i) elucidating cues that modulate in vitro cell secretion of organized matrix and (ii) establishing an optically accessible cell culture system for investigating the mechanism of cell secretion of aligned collagen fibrils. PMID:19480568

Laser Light Scattering with Multiple Scattering Suppression Used to Measure Particle Sizes

NASA Technical Reports Server (NTRS)

Meyer, William V.; Tin, Padetha; Lock, James A.; Cannell, David S.; Smart, Anthony E.; Taylor, Thomas W.

1999-01-01

Laser light scattering is the technique of choice for noninvasively sizing particles in a fluid. The members of the Advanced Technology Development (ATD) project in laser light scattering at the NASA Lewis Research Center have invented, tested, and recently enhanced a simple and elegant way to extend the concentration range of this standard laboratory particle-sizing technique by several orders of magnitude. With this technique, particles from 3 nm to 3 mm can be measured in a solution. Recently, laser light scattering evolved to successfully size particles in both clear solutions and concentrated milky-white solutions. The enhanced technique uses the property of light that causes it to form tall interference patterns at right angles to the scattering plane (perpendicular to the laser beam) when it is scattered from a narrow laser beam. Such multiple-scattered light forms a broad fuzzy halo around the focused beam, which, in turn, forms short interference patterns. By placing two fiber optics on top of each other and perpendicular to the laser beam (see the drawing), and then cross-correlating the signals they produce, only the tall interference patterns formed by singly scattered light are detected. To restate this, unless the two fiber optics see the same interference pattern, the scattered light is not incorporated into the signal. With this technique, only singly scattered light is seen (multiple-scattered light is rejected) because only singly scattered light has an interference pattern tall enough to span both of the fiber-optic pickups. This technique is simple to use, easy to align, and works at any angle. Placing a vertical slit in front of the signal collection fibers enhanced this approach. The slit serves as an optical mask, and it significantly shortens the time needed to collect good data by selectively masking out much of the unwanted light before cross-correlation is applied.

Summary of EOS flight dynamics analysis

NASA Technical Reports Server (NTRS)

Newman, Lauri Kraft; Folta, David C.

1995-01-01

From a flight dynamics perspective, the Earth Observing System (EOS) spacecraft present a number of challenges to mission designers. The Flight Dynamics Support Branch of NASA GSFC has examined a number of these challenges, including managing the EOS constellation, disposing of the spacecraft at the end-of-life (EOL), and achieving the appropriate mission orbit given launch vehicle and ascent propulsion constraints. The EOS program consists of a number of spacecraft including EOS-AM, an ascending node spacecraft, EOS-PM, a descending node spacecraft, the EOS Chemistry mission (EOS-CHEM), the EOS Altimetry Laser (EOS-LALT), and the EOS-Altimetry Radar (EOS-RALT). The orbit characteristics of these missions are presented. In order to assure that downlinking data from each spacecraft will be possible without interference between any two spacecraft, a careful examination of the relationships between spacecraft and how to maintain the spacecraft in a configuration which would minimize these communications problems must be made. The FDSB has performed various analyses to determine whether the spacecraft will be in a position to interfere with each other, how the orbit dynamics will change the relative positioning of the spacecraft over their lifetimes, and how maintenance maneuvers could be performed, if needed, to minimize communications problems. Prompted by an activity at NASA HQ to set guidelines for spacecraft regarding their end-of-life dispositions, much analysis has also been performed to determine the spacecraft lifetime of EOS-AM1 under various conditions, and to make suggestions regarding the spacecraft disposal. In performing this analysis, some general trends have been observed in lifetime calculations. The paper will present the EOS-AM1 lifetime results, comment on general reentry conclusions, and discuss how these analyses reflect on the HQ NMI. Placing the EOS spacecraft into their respective mission orbits involves some intricate maneuver planning to assure that all mission orbit requirements are met, given the initial conditions supplied by the launch vehicle at injection. The FDSB has developed an ascent scenario to meet the mission requirements. This paper presents results of the ascent analysis.

Energy-efficient downlink resource management in self-organized OFDMA-based two-tier femtocell networks

NASA Astrophysics Data System (ADS)

Shahid, Adnan; Aslam, Saleem; Kim, Hyung Seok; Lee, Kyung-Geun

2015-12-01

Femtocell is a novel technology that is used for escalating indoor coverage as well as the capacity of traditional cellular networks. However, interference is the limiting factor for performance improvement due to co-channel deployment between macrocells and femtocells. The traditional network planning is not feasible because of the random deployment of femtocells. Therefore, self-organization approaches are the key to having successful deployment of femtocells. This study presents the joint resource block (RB) and power allocation task for the two-tier femtocell network in a self-organizing manner, with the concern to minimizing the impact of interference and maximizing the energy efficiency. In this study, we analyze the performance of the system in terms of the energy efficiency, which is composed of both the transmission and circuit power. Most of the previous studies investigate the performance regarding the throughput requirement of the two-tier femtocell network while the energy efficiency aspect is largely ignored. Here, the joint allocation task is modeled as a non-cooperative game which is demonstrated to exhibit pure and unique Nash equilibrium. In order to reduce the complexity of the proposed non-cooperative game, the joint RB and power allocation task is divided into two subproblems: an RB allocation and a particle swarm optimization-based power allocation. The analysis of the proposed game is carried out in terms of not only energy efficiency but also throughput. With practical 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) parameters, the simulation results illustrate the superior performance of the proposed game as compared to the traditional methods. Also, the comparison is carried out with the joint allocation scheme which only considers the throughput as the objective function. The results illustrate that significant performance improvement is achieved in terms of energy efficiency with slight loss in the throughput. The analysis in regard to energy efficiency and throughput of the two-tier femtocell network is carried out in terms of the performance metrics, which include convergence, impact of varying RBs, impact of femtocell density, and the fairness index.

Incentive and Architecture of Multi-Band Enabled Small Cell and UE for Up-/Down-Link and Control-/User-Plane Splitting for 5G Mobile Networks

NASA Astrophysics Data System (ADS)

Saha, Rony Kumer; Aswakul, Chaodit

2017-01-01

In this paper, a multi-band enabled femtocell base station (FCBS) and user equipment (UE) architecture is proposed in a multi-tier network that consists of small cells, including femtocells and picocells deployed over the coverage of a macrocell for splitting uplink and downlink (UL/DL) as well as control-plane and user-plane (C-/U-plane) for 5G mobile networks. Since splitting is performed at the same FCBS, we define this architecture as the same base station based split architecture (SBSA). For multiple bands, we consider co-channel (CC) microwave and different frequency (DF) 60 GHz millimeter wave (mmWave) bands for FCBSs and UEs with respect to the microwave band used by their over-laid macrocell base station. All femtocells are assumed to be deployed in a 3-dimensional multi-storage building. For CC microwave band, cross-tier CC interference of femtocells with macrocell is avoided using almost blank subframe based enhanced inter-cell interference coordination techniques. The co-existence of CC microwave and DF mmWave bands for SBSA on the same FCBS and UE is first studied to show their performance disparities in terms of system capacity and spectral efficiency in order to provide incentives for employing multiple bands at the same FCBS and UE and identify a suitable band for routing decoupled UL/DL or C-/U-plane traffic. We then present a number of disruptive architectural design alternatives of multi-band enabled SBSA for 5G mobile networks for UL/DL and C-/U-plane splitting, including a disruptive and complete splitting of UL/DL and C-/U-plane as well as a combined UL/DL and C-/U-plane splitting, by exploiting dual connectivity on CC microwave and DF mmWave bands. The outperformances of SBSA in terms of system level capacity, average spectral efficiency, energy efficiency, and control-plane overhead traffic capacity in comparison with different base stations based split architecture (DBSA) are shown. Finally, a number of technical and business perspectives as well as key research issues of SBSA are discussed.

47 CFR 25.158 - Consideration of GSO-like satellite applications.

Code of Federal Regulations, 2010 CFR

2010-10-01

... directional antennas. Examples of GSO-like satellite systems are those which use earth stations with antennas... contiguous bandwidth in both the uplink and downlink band. Each licensee's bandwidth selection shall not... selection. (e) Services offered pursuant to a GSO-like license in a frequency band granted before the...

47 CFR 25.157 - Consideration of NGSO-like satellite applications.

Code of Federal Regulations, 2010 CFR

2010-10-01

...-directional antennas. (b) Each NGSO-like satellite system application will be reviewed to determine whether it... licensee's bandwidth selection in both the uplink and downlink band shall not preclude other licensees from... to make another selection. (g)(1) In the event that an applicants' license is cancelled for any...

Stripline Antenna Beam-Forming Network

NASA Technical Reports Server (NTRS)

Cramer, P. W.

1984-01-01

Stripline antenna beam-forming network includes 87 beam ports and 136 feed-element ports and contained on only two microstrip boards. Both uplink and downlink strips supported on same boards. Originally used for communications coverage of continental United States for Land Mobile Satellite System, structure of interest to antenna designers in other applications.

Mentoring for Youth in Schools and Communities. National Satellite Videoconference. [Videotape].

ERIC Educational Resources Information Center

Department of Justice, Washington, DC. Office of Juvenile Justice and Delinquency Prevention.

This videotape presents the National Satellite Videoconference on mentoring for youth. The video opens with a discussion of mentoring and presents panelists who make statements about mentoring and youth programs and respond to questions called in by videoconference participants at approximately 500 downlinked sites. Panelists were: (1) Shay…

The use of LANDSAT DCS and imagery in reservoir management and operation. [New England

NASA Technical Reports Server (NTRS)

Cooper, S. (Principal Investigator)

1976-01-01

The author has identified the following significant results. A tally of DCP messages received shows that the number of messages increased markedly at the beginning of the year as the downlink went into operation, but dropped off in May due to computer troubles.

47 CFR 25.211 - Analog video transmissions in the Fixed-Satellite Services.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 2 2011-10-01 2011-10-01 false Analog video transmissions in the Fixed...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25.211 Analog video transmissions in the Fixed-Satellite Services. (a) Downlink analog video transmissions in the band 3700-4200 MHz...

47 CFR 25.211 - Analog video transmissions in the Fixed-Satellite Services.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 2 2013-10-01 2013-10-01 false Analog video transmissions in the Fixed...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25.211 Analog video transmissions in the Fixed-Satellite Services. (a) Downlink analog video transmissions in the band 3700-4200 MHz...

47 CFR 25.211 - Analog video transmissions in the Fixed-Satellite Services.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 2 2014-10-01 2014-10-01 false Analog video transmissions in the Fixed...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25.211 Analog video transmissions in the Fixed-Satellite Services. (a) Downlink analog video transmissions in the band 3700-4200 MHz...

47 CFR 25.211 - Analog video transmissions in the Fixed-Satellite Services.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 2 2012-10-01 2012-10-01 false Analog video transmissions in the Fixed...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25.211 Analog video transmissions in the Fixed-Satellite Services. (a) Downlink analog video transmissions in the band 3700-4200 MHz...

47 CFR 25.211 - Analog video transmissions in the Fixed-Satellite Services.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 2 2010-10-01 2010-10-01 false Analog video transmissions in the Fixed...) COMMON CARRIER SERVICES SATELLITE COMMUNICATIONS Technical Standards § 25.211 Analog video transmissions in the Fixed-Satellite Services. (a) Downlink analog video transmissions in the band 3700-4200 MHz...

47 CFR 20.21 - Signal boosters.

Code of Federal Regulations, 2014 CFR

2014-10-01

... operation to ensure compliance with applicable noise and gain limits and either self-correct or shut down... provide equivalent uplink and downlink gain and conducted uplink power output that is at least 0.05 watts... referenced to the booster's input port for each band of operation. (C) Booster Gain Limits. (1) The uplink...

47 CFR 20.21 - Signal boosters.

Code of Federal Regulations, 2013 CFR

2013-10-01

... operation to ensure compliance with applicable noise and gain limits and either self-correct or shut down... provide equivalent uplink and downlink gain and conducted uplink power output that is at least 0.05 watts... referenced to the booster's input port for each band of operation. (C) Booster Gain Limits. (1) The uplink...

Telecommunications in Higher Education: Creating New Information Sources.

ERIC Educational Resources Information Center

Brown, Fred D.

1986-01-01

Discusses the telecommunications systems in operation at Buena Vista College in Iowa. Describes the systems' uses in linking all offices and classrooms on the campus, downlinking satellite communications through a dish, transmitting audio and video information to any set of defined studio or classroom space, and teleconferencing. (TW)

Melanie Klein and countertransference: a note on some archival material.

PubMed

Hinshelwood, R D

2008-01-01

Five pages of notes were found in the Melanie Klein Archives at the Wellcome Library that concern her views on countertransference in 1953. Because of the paucity of references to countertransference in Klein's published writings these Notes fill in out knowledge. Her views were provoked by the work her students were doing in their experimental analyses of schizophrenic patients. Apocryphal stories suggest that Klein remained aligned with Freud's view of countertransference as simply interference. The Notes confirm that, whilst there is some truth to that, she did have a more sophisticated and nuanced view of the unconscious relations between analyst and analysand.

Risk of Performance Decrements and Adverse Health Outcomes Resulting from Sleep Loss, Circadian Desynchronization, and Work Overload

NASA Technical Reports Server (NTRS)

Evans-Flynn, Erin; Gregory, Kevin; Arsintescu, Lucia; Whitmire, Alexandra; Leveton, Lauren B.; Vessey, William

2015-01-01

Sleep loss, circadian desynchronization, and work overload occur to some extent for ground and flight crews, prior to and during spaceflight missions. Ground evidence indicates that such risk factors may lead to performance decrements and adverse health outcomes, which could potentially compromise mission objectives. Efforts are needed to identify the environmental and mission conditions that interfere with sleep and circadian alignment, as well as individual differences in vulnerability and resiliency to sleep loss and circadian desynchronization. Specifically, this report highlights a collection of new evidence to better characterize the risk and reveals new gaps in this risk.

Standing wave contributions to the linear interference effect in stratosphere-troposphere coupling

NASA Astrophysics Data System (ADS)

Watt-Meyer, Oliver; Kushner, Paul

2014-05-01

A body of literature by Hayashi and others [Hayashi 1973, 1977, 1979; Pratt, 1976] developed a decomposition of the wavenumber-frequency spectrum into standing and travelling waves. These techniques directly decompose the power spectrum—that is, the amplitudes squared—into standing and travelling parts. This, incorrectly, does not allow for a term representing the covariance between these waves. We propose a simple decomposition based on the 2D Fourier transform which allows one to directly compute the variance of the standing and travelling waves, as well as the covariance between them. Applying this decomposition to geopotential height anomalies in the Northern Hemisphere winter, we show the dominance of standing waves for planetary wavenumbers 1 through 3, especially in the stratosphere, and that wave-1 anomalies have a significant westward travelling component in the high-latitude (60N to 80N) troposphere. Variations in the relative zonal phasing between a wave anomaly and the background climatological wave pattern—the "linear interference" effect—are known to explain a large part of the planetary wave driving of the polar stratosphere in both hemispheres. While the linear interference effect is robust across observations, models of varying degrees of complexity, and in response to various types of perturbations, it is not well understood dynamically. We use the above-described decomposition into standing and travelling waves to investigate the drivers of linear interference. We find that the linear part of the wave activity flux is primarily driven by the standing waves, at all vertical levels. This can be understood by noting that the longitudinal positions of the antinodes of the standing waves are typically close to being aligned with the maximum and minimum of the background climatology. We discuss implications for predictability of wave activity flux, and hence polar vortex strength variability.

A Dimensionally Aligned Signal Projection for Classification of Unintended Radiated Emissions

DOE PAGES

Vann, Jason Michael; Karnowski, Thomas P.; Kerekes, Ryan; ...

2017-04-24

Characterization of unintended radiated emissions (URE) from electronic devices plays an important role in many research areas from electromagnetic interference to nonintrusive load monitoring to information system security. URE can provide insights for applications ranging from load disaggregation and energy efficiency to condition-based maintenance of equipment-based upon detected fault conditions. URE characterization often requires subject matter expertise to tailor transforms and feature extractors for the specific electrical devices of interest. We present a novel approach, named dimensionally aligned signal projection (DASP), for projecting aligned signal characteristics that are inherent to the physical implementation of many commercial electronic devices. These projectionsmore » minimize the need for an intimate understanding of the underlying physical circuitry and significantly reduce the number of features required for signal classification. We present three possible DASP algorithms that leverage frequency harmonics, modulation alignments, and frequency peak spacings, along with a two-dimensional image manipulation method for statistical feature extraction. To demonstrate the ability of DASP to generate relevant features from URE, we measured the conducted URE from 14 residential electronic devices using a 2 MS/s collection system. Furthermore, a linear discriminant analysis classifier was trained using DASP generated features and was blind tested resulting in a greater than 90% classification accuracy for each of the DASP algorithms and an accuracy of 99.1% when DASP features are used in combination. Furthermore, we show that a rank reduced feature set of the combined DASP algorithms provides a 98.9% classification accuracy with only three features and outperforms a set of spectral features in terms of general classification as well as applicability across a broad number of devices.« less

A Dimensionally Aligned Signal Projection for Classification of Unintended Radiated Emissions

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

Vann, Jason Michael; Karnowski, Thomas P.; Kerekes, Ryan

Characterization of unintended radiated emissions (URE) from electronic devices plays an important role in many research areas from electromagnetic interference to nonintrusive load monitoring to information system security. URE can provide insights for applications ranging from load disaggregation and energy efficiency to condition-based maintenance of equipment-based upon detected fault conditions. URE characterization often requires subject matter expertise to tailor transforms and feature extractors for the specific electrical devices of interest. We present a novel approach, named dimensionally aligned signal projection (DASP), for projecting aligned signal characteristics that are inherent to the physical implementation of many commercial electronic devices. These projectionsmore » minimize the need for an intimate understanding of the underlying physical circuitry and significantly reduce the number of features required for signal classification. We present three possible DASP algorithms that leverage frequency harmonics, modulation alignments, and frequency peak spacings, along with a two-dimensional image manipulation method for statistical feature extraction. To demonstrate the ability of DASP to generate relevant features from URE, we measured the conducted URE from 14 residential electronic devices using a 2 MS/s collection system. Furthermore, a linear discriminant analysis classifier was trained using DASP generated features and was blind tested resulting in a greater than 90% classification accuracy for each of the DASP algorithms and an accuracy of 99.1% when DASP features are used in combination. Furthermore, we show that a rank reduced feature set of the combined DASP algorithms provides a 98.9% classification accuracy with only three features and outperforms a set of spectral features in terms of general classification as well as applicability across a broad number of devices.« less

High-field magnetoconductance in Anderson insulators

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

Vaknin, A.; Frydman, A.; Ovadyahu, Z.

1996-11-01

We report on high-field magnetoconductance measurements made on indium-oxide films as a function of temperature and static disorder. Special emphasis is given to the strong-localization regime where the magnetoconductance reveals a negative contribution associated with a spin-alignment mechanism in addition to the positive contribution associated with orbital, quantum-coherence effects. While the overall features of the theoretically expected effects are observed in our experiments, they depart in certain ways from the detailed predictions. We discuss the merits and shortcomings of current models to describe them, in particular, as they apply to the regime where the localized wave functions become larger thanmore » the Bohr radius. The main results of this paper are both quantum interference and spin effects contribute to the magnetoconductance throughout the entire range studied. In the limit of very strong disorder, the quantum interference effects are faithfully described by the Nguyen {ital et} {ital al}. model. The spin effects, on the other hand, show only qualitative agreement with current models which are unable to account for the saturation field being insensitive to changes in disorder. {copyright} {ital 1996 The American Physical Society.}« less

Spectral-domain low-coherence interferometry for phase-sensitive measurement of Faraday rotation at multiple depths.

PubMed

Yeh, Yi-Jou; Black, Adam J; Akkin, Taner

2013-10-10

We describe a method for differential phase measurement of Faraday rotation from multiple depth locations simultaneously. A polarization-maintaining fiber-based spectral-domain interferometer that utilizes a low-coherent light source and a single camera is developed. Light decorrelated by the orthogonal channels of the fiber is launched on a sample as two oppositely polarized circular states. These states reflect from sample surfaces and interfere with the corresponding states of the reference arm. A custom spectrometer, which is designed to simplify camera alignment, separates the orthogonal channels and records the interference-related oscillations on both spectra. Inverse Fourier transform of the spectral oscillations in k-space yields complex depth profiles, whose amplitudes and phase difference are related to reflectivity and Faraday rotation within the sample, respectively. Information along a full depth profile is produced at the camera speed without performing an axial scan for a multisurface sample. System sensitivity for the Faraday rotation measurement is 0.86 min of arc. Verdet constants of clear liquids and turbid media are measured at 687 nm.

NMR of (133)Cs(+) in stretched hydrogels: One-dimensional, z- and NOESY spectra, and probing the ion's environment in erythrocytes.

PubMed

Kuchel, Philip W; Shishmarev, Dmitry; Puckeridge, Max; Levitt, Malcolm H; Naumann, Christoph; Chapman, Bogdan E

2015-12-01

(133)Cs nuclear magnetic resonance (NMR) spectroscopy was conducted on (133)Cs(+) in gelatin hydrogels that were either relaxed or stretched. Stretching generated a septet from this spin-7/2 nucleus, and its nuclear magnetic relaxation was studied via z-spectra, and two-dimensional nuclear Overhauser (NOESY) spectroscopy. Various spectral features were well simulated by using Mathematica and the software package SpinDynamica. Spectra of CsCl in suspensions of human erythrocytes embedded in gelatin gel showed separation of the resonances from the cation inside and outside the cells. Upon stretching the sample, the extracellular (133)Cs(+) signal split into a septet, while the intracellular peak was unchanged, revealing different alignment/ordering properties of the environment inside and around the cells. Differential interference contrast light microscopy confirmed that the cells were stretched when the overall sample was elongated. Analysis of the various spectral features of (133)Cs(+) reported here opens up applications of this K(+) congener for studies of cation-handling by metabolically-active cells and tissues in aligned states. Copyright © 2015 Elsevier Inc. All rights reserved.

Interferometric surface mapping with variable sensitivity.

PubMed

Jaerisch, W; Makosch, G

1978-03-01

In the photolithographic process, presently employed for the production of integrated circuits, sets of correlated masks are used for exposing the photoresist on silicon wafers. Various sets of masks which are printed in different printing tools must be aligned correctly with respect to the structures produced on the wafer in previous process steps. Even when perfect alignment is considered, displacements and distortions of the printed wafer patterns occur. They are caused by imperfections of the printing tools or/and wafer deformations resulting from high temperature processes. Since the electrical properties of the final integrated circuits and therefore the manufacturing yield depend to a great extent on the precision at which such patterns are superimposed, simple and fast overlay measurements and flatness measurements as well are very important in IC-manufacturing. A simple optical interference method for flatness measurements will be described which can be used under manufacturing conditions. This method permits testing of surface height variations by nearly grazing light incidence by absence of a physical reference plane. It can be applied to polished surfaces and rough surfaces as well.

Wavelet analysis of poorly-focused ultrasonic signal of pressure tube inspection in nuclear industry

NASA Astrophysics Data System (ADS)

Zhao, Huan; Gachagan, Anthony; Dobie, Gordon; Lardner, Timothy

2018-04-01

Pressure tube fabrication and installment challenges combined with natural sagging over time can produce issues with probe alignment for pressure tube inspection of the primary circuit of CANDU reactors. The ability to extract accurate defect depth information from poorly focused ultrasonic signals would reduce additional inspection procedures, which leads to a significant time and cost saving. Currently, the defect depth measurement protocol is to simply calculate the time difference between the peaks of the echo signals from the tube surface and the defect from a single element probe focused at the back-wall depth. When alignment issues are present, incorrect focusing results in interference within the returning echo signal. This paper proposes a novel wavelet analysis method that employs the Haar wavelet to decompose the original poorly focused A-scan signal and reconstruct detailed information based on a selected high frequency component range within the bandwidth of the transducer. Compared to the original signal, the wavelet analysis method provides additional characteristic defect information and an improved estimate of defect depth with errors less than 5%.

ISS NASA Social

NASA Image and Video Library

2013-02-20

Expedition 33/34 astronauts onboard the International Space Station answer questions in a live downlink at a NASA Social exploring science on the ISS at NASA Headquarters, Wednesday, Feb. 20, 2013 in Washington. Seen from left to right are NASA astronauts Tom Marshburn, Kevin Ford and Canadian Space Agency (CSA) astronaut Chris Hadfield. Photo Credit: (NASA/Carla Cioffi)

Experimental Optimization of Exposure Index and Quality of Service in Wlan Networks.

PubMed

Plets, David; Vermeeren, Günter; Poorter, Eli De; Moerman, Ingrid; Goudos, Sotirios K; Luc, Martens; Wout, Joseph

2017-07-01

This paper presents the first real-life optimization of the Exposure Index (EI). A genetic optimization algorithm is developed and applied to three real-life Wireless Local Area Network scenarios in an experimental testbed. The optimization accounts for downlink, uplink and uplink of other users, for realistic duty cycles, and ensures a sufficient Quality of Service to all users. EI reductions up to 97.5% compared to a reference configuration can be achieved in a downlink-only scenario, in combination with an improved Quality of Service. Due to the dominance of uplink exposure and the lack of WiFi power control, no optimizations are possible in scenarios that also consider uplink traffic. However, future deployments that do implement WiFi power control can be successfully optimized, with EI reductions up to 86% compared to a reference configuration and an EI that is 278 times lower than optimized configurations under the absence of power control. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Microhard MHX 2420 Orbital Performance Evaluation Using RT Logic T400CS

NASA Technical Reports Server (NTRS)

Kearney, Stuart; Lombardi, Mark; Attai, Watson; Oyadomari, Ken; Al Rumhi, Ahmed Saleh Nasser; Rakotonarivo, Sebastien; Chardon, Loic; Gazulla, Oriol Tintore; Wolfe, Jasper; Salas, AlbertoGuillen;

Evaluation of Algorithms for Compressing Hyperspectral Data

NASA Technical Reports Server (NTRS)

Cook, Sid; Harsanyi, Joseph; Faber, Vance

2003-01-01

With EO-1 Hyperion in orbit NASA is showing their continued commitment to hyperspectral imaging (HSI). As HSI sensor technology continues to mature, the ever-increasing amounts of sensor data generated will result in a need for more cost effective communication and data handling systems. Lockheed Martin, with considerable experience in spacecraft design and developing special purpose onboard processors, has teamed with Applied Signal & Image Technology (ASIT), who has an extensive heritage in HSI spectral compression and Mapping Science (MSI) for JPEG 2000 spatial compression expertise, to develop a real-time and intelligent onboard processing (OBP) system to reduce HSI sensor downlink requirements. Our goal is to reduce the downlink requirement by a factor > 100, while retaining the necessary spectral and spatial fidelity of the sensor data needed to satisfy the many science, military, and intelligence goals of these systems. Our compression algorithms leverage commercial-off-the-shelf (COTS) spectral and spatial exploitation algorithms. We are currently in the process of evaluating these compression algorithms using statistical analysis and NASA scientists. We are also developing special purpose processors for executing these algorithms onboard a spacecraft.

New Horizons Successful Completes the Historic First Flyby of Pluto and Its Moons

NASA Technical Reports Server (NTRS)

Ennico, Kimberly

2015-01-01

On July 14, 2015, after a 9.5 year trek across the solar system, NASA's New Horizons spacecraft flew by the dwarf planet Pluto and its system of moons, taking imagery, spectra and in-situ particle data. Data from New Horizons will address numerous outstanding questions on the geology and composition of Pluto and Charon, plus measurements of Pluto's atmosphere, and provide revised understanding of the formation and evolution of Pluto and Charon and its smaller moons. This data set is an invaluable glimpse into the outer Third Zone of the solar system. Data from the intense July 14th fly-by sequence will be downlinked to Earth over a period of 16 months, the duration set by the large data set (over 60 GBits) and the limited transmitted bandwidth rates (approx. 1-2 kbps) and sharing the three 70 m DSN assets with our missions. The small fraction (approx. 1%) of data downlinked during the early phase of the flyby has already revealed Pluto and Charon to be very different worlds, with increasing and dynamic complexity.

Evaluation of optical up- and downlinks from high altitude platforms using IM/DD

NASA Astrophysics Data System (ADS)

Henniger, Hennes; Giggenbach, Dirk; Horwath, Joachim; Rapp, Christoph

2005-04-01

The advantages of optical links like small, light and power efficient terminals are practical for high data rate services over high altitude platforms (HAPs). However, atmospheric effects can disturb the optical links and must be considered in link design. In this paper we evaluate clear sky and non clear sky attenuation effects and their impact on the link-quality of up- and downlinks from HAPs. As vertical links could be restricted by very large cloud and fog attenuation, investigations of the scattering effects in cloud media has been done. The Mie-theory shows that cloud transmittance is not depending on the wavelength, whereas the attenuation of fog and dust is smaller for longer wavelengths. Satellite cloud data has been used to predict the link availability for a ground station in Germany. A ground station diversity concept is introduced to achieve higher link availability. As high receiver sensitivity helps to reduce terminal mass, power and size, evaluation of receiver sensitivity is shown. Also, a receiver model is developed which enables to calculate for the background light loss in direct detection systems.

Experimental demonstration of high spectral efficient 4 × 4 MIMO SCMA-OFDM/OQAM radio over multi-core fiber system.

PubMed

Liu, Chang; Deng, Lei; He, Jiale; Li, Di; Fu, Songnian; Tang, Ming; Cheng, Mengfan; Liu, Deming

2017-07-24

In this paper, 4 × 4 multiple-input multiple-output (MIMO) radio over 7-core fiber system based on sparse code multiple access (SCMA) and OFDM/OQAM techniques is proposed. No cyclic prefix (CP) is required by properly designing the prototype filters in OFDM/OQAM modulator, and non-orthogonally overlaid codewords by using SCMA is help to serve more users simultaneously under the condition of using equal number of time and frequency resources compared with OFDMA, resulting in the increase of spectral efficiency (SE) and system capacity. In our experiment, 11.04 Gb/s 4 × 4 MIMO SCMA-OFDM/OQAM signal is successfully transmitted over 20 km 7-core fiber and 0.4 m air distance in both uplink and downlink. As a comparison, 6.681 Gb/s traditional MIMO-OFDM signal with the same occupied bandwidth has been evaluated for both uplink and downlink transmission. The experimental results show that SE could be increased by 65.2% with no bit error rate (BER) performance degradation compared with the traditional MIMO-OFDM technique.

Simulating the performance of adaptive optics techniques on FSO communications through the atmosphere

NASA Astrophysics Data System (ADS)

Martínez, Noelia; Rodríguez Ramos, Luis Fernando; Sodnik, Zoran

2017-08-01

The Optical Ground Station (OGS), installed in the Teide Observatory since 1995, was built as part of ESA efforts in the research field of satellite optical communications to test laser telecommunication terminals on board of satellites in Low Earth Orbit and Geostationary Orbit. As far as one side of the link is settled on the Earth, the laser beam (either on the uplink or on the downlink) has to bear with the atmospheric turbulence. Within the framework of designing an Adaptive Optics system to improve the performance of the Free-Space Optical Communications at the OGS, turbulence conditions regarding uplink and downlink have been simulated within the OOMAO (Object-Oriented Matlab Adaptive Optics) Toolbox as well as the possible utilization of a Laser Guide Star to measure the wavefront in this context. Simulations have been carried out by reducing available atmospheric profiles regarding both night-time and day-time measurements and by having into account possible seasonal changes. An AO proposal to reduce atmospheric aberrations and, therefore, ameliorate FSO links performance is presented and analysed in this paper

X-Band CubeSat Communication System Demonstration

NASA Technical Reports Server (NTRS)

Altunc, Serhat; Kegege, Obadiah; Bundick, Steve; Shaw, Harry; Schaire, Scott; Bussey, George; Crum, Gary; Burke, Jacob C.; Palo, Scott; O'Conor, Darren

2015-01-01

Today's CubeSats mostly operate their communications at UHF- and S-band frequencies. UHF band is presently crowded, thus downlink communications are at lower data rates due to bandwidth limitations and are unreliable due to interference. This research presents an end-to-end robust, innovative, compact, efficient and low cost S-band uplink and X-band downlink CubeSat communication system demonstration between a balloon and a Near Earth Network (NEN) ground system. Since communication systems serve as umbilical cords for space missions, demonstration of this X-band communication system is critical for successfully supporting current and future CubeSat communication needs. This research has three main objectives. The first objective is to design, simulate, and test a CubeSat S- and X-band communication system. Satellite Tool Kit (STK) dynamic link budget calculations and HFSS Simulations and modeling results have been used to trade the merit of various designs for small satellite applications. S- and X-band antennas have been tested in the compact antenna test range at Goddard Space Flight Center (GSFC) to gather radiation pattern data. The second objective is simulate and test a CubeSat compatible X-band communication system at 12.5Mbps including S-band antennas, X-band antennas, Laboratory for Atmospheric and Space Physics (LASP) /GSFC transmitter and an S-band receiver from TRL-5 to TRL-8 by the end of this effort. Different X-band communication system components (antennas, diplexers, etc.) from GSFC, other NASA centers, universities, and private companies have been investigated and traded, and a complete component list for the communication system baseline has been developed by performing analytical and numerical analysis. This objective also includes running simulations and performing trades between different X-band antenna systems to optimize communication system performance. The final objective is to perform an end-to-end X-band CubeSat communication system demonstration between a balloon and/or a sounding rocket and a Near Earth Network (NEN) ground system. This paper presents CubeSat communication systems simulation results, analysis of X-band and S-band antennas and RF front-end components, transceiver design, analysis and optimization of space-to-ground communication performance, subsystem development, as well as the test results for an end-to-end X-band CubeSat communication system demonstration. The outcome of this work will be used to pave the way for next generation NEN-compatible X-band CubeSat communication systems to support higher data rates with more advanced modulation and forward error correction (FEC) coding schemes, and to support and attract new science missions at lower cost. It also includes an abbreviated concept of operations for CubeSat users to utilize the NEN, starting from first contact with NASA's communication network and continuing through on-orbit operations.

Theory and implementation of summarization: Improving sensor interpretation for spacecraft operations

NASA Astrophysics Data System (ADS)

Swartwout, Michael Alden

New paradigms in space missions require radical changes in spacecraft operations. In the past, operations were insulated from competitive pressures of cost, quality and time by system infrastructures, technological limitations and historical precedent. However, modern demands now require that operations meet competitive performance goals. One target for improvement is the telemetry downlink, where significant resources are invested to acquire thousands of measurements for human interpretation. This cost-intensive method is used because conventional operations are not based on formal methodologies but on experiential reasoning and incrementally adapted procedures. Therefore, to improve the telemetry downlink it is first necessary to invent a rational framework for discussing operations. This research explores operations as a feedback control problem, develops the conceptual basis for the use of spacecraft telemetry, and presents a method to improve performance. The method is called summarization, a process to make vehicle data more useful to operators. Summarization enables rational trades for telemetry downlink by defining and quantitatively ranking these elements: all operational decisions, the knowledge needed to inform each decision, and all possible sensor mappings to acquire that knowledge. Summarization methods were implemented for the Sapphire microsatellite; conceptual health management and system models were developed and a degree-of-observability metric was defined. An automated tool was created to generate summarization methods from these models. Methods generated using a Sapphire model were compared against the conventional operations plan. Summarization was shown to identify the key decisions and isolate the most appropriate sensors. Secondly, a form of summarization called beacon monitoring was experimentally verified. Beacon monitoring automates the anomaly detection and notification tasks and migrates these responsibilities to the space segment. A set of experiments using Sapphire demonstrated significant cost and time savings compared to conventional operations. Summarization is based on rational concepts for defining and understanding operations. Therefore, it enables additional trade studies that were formerly not possible and also can form the basis for future detailed research into spacecraft operations.

Architecture Studies Done for High-Rate Duplex Direct Data Distribution (D4) Services

NASA Technical Reports Server (NTRS)

2002-01-01

A study was sponsored to investigate a set of end-to-end system concepts for implementing a high-rate duplex direct data distribution (D4) space-to-ground communications link. The NASA Glenn Research Center is investigating these systems (both commercial and Government) as a possible method of providing a D4 communications service between NASA spacecraft in low Earth orbit and the respective principal investigators using or monitoring instruments aboard these spacecraft. Candidate commercial services were assessed regarding their near-term potential to provide a D4 type of service. The candidates included K-band and V-band geostationary orbit and nongeostationary orbit satellite relay services and direct downlink (D3) services. Internet protocol (IP) networking technologies were evaluated to enable the user-directed distribution and delivery of science data. Four realistic, near-future concepts were analyzed: 1) A duplex direct link (uplink plus downlink communication paths) between a low-Earth-orbit spacecraft and a principal-investigator-based autonomous Earth station; 2) A space-based relay using a future K-band nongeosynchronous-orbit system to handle both the uplink and downlink communication paths; 3) A hybrid link using both direct and relay services to achieve full duplex capability; 4) A dual-mode concept consisting of both a duplex direct link and a space relay duplex link operating independently. The concepts were analyzed in terms of contact time between the NASA spacecraft and the communications service and the achievable data throughput. Throughput estimates for the D4 systems were based on the infusion of advanced communications technology products (single and multibeam K-band phased-arrays and digital modems) being developed by Glenn. Cost estimates were also performed using extrapolated information from both terrestrial and current satellite communications providers. The throughput and cost estimates were used to compare the concepts.

Micro ring cavity resonator incorporating total internal reflection mirrors

NASA Astrophysics Data System (ADS)

Kim, Doo Gun; Choi, Woon Kyung; Choi, Young Wan; Yi, Jong Chang; Chung, Youngchul; Dagli, Nadir

2007-02-01

We investigate the properties of a multimode-interference (MMI) coupled micro ring cavity resonator with total-internal-reflection (TIR) mirrors and a semiconductor optical amplifier (SOA). The TIR mirrors were fabricated by the self-aligned process with a loss of 0.7 dB per mirror. The length and width of an MMI are 142 μm and 10 μm, respectively. The resulting free spectral range (FSR) of the resonator was approximately 1.698 nm near 1571 nm and the extinction ratio was about 17 dB. These devices might be useful as optical switching and add-drop filters in a photonic integrated circuit or as small and fast resonator devices.

Dual-modulation fiber Fabry-Perot interferometer with double reflection for slowly-varying displacements.

PubMed

Seat, H C; Chawah, P; Cattoen, M; Sourice, A; Plantier, G; Boudin, F; Chéry, J; Brunet, C; Bernard, P; Suleiman, M

2012-07-15

This Letter describes a dual-amplitude modulation technique incorporated into a double reflection extrinsic-type fiber Fabry-Perot interferometer to measure periodic, nonperiodic as well as quasi-static displacements. The modulation scheme simultaneously maintains the interference signal pair in quadrature and provides a reference signal for displacements inferior to a quarter of the source wavelength. The control and phase demodulation of the interferometer carried out via software enable quasi-real-time measurement and facilitates sensor alignment. The sensor system can be exploited in the low frequency range from 10(-3) to ∼500 Hz and has a resolution better than 2.2 nm, targeting applications in geophysics.

Flipping interferometry and its application for quantitative phase microscopy in a micro-channel.

PubMed

Roitshtain, Darina; Turko, Nir A; Javidi, Bahram; Shaked, Natan T

2016-05-15

We present a portable, off-axis interferometric module for quantitative phase microscopy of live cells, positioned at the exit port of a coherently illuminated inverted microscope. The module creates on the digital camera an interference pattern between the image of the sample and its flipped version. The proposed simplified module is based on a retro-reflector modification in an external Michelson interferometer. The module does not contain any lenses, pinholes, or gratings and its alignment is straightforward. Still, it allows full control of the off-axis angle and does not suffer from ghost images. As experimentally demonstrated, the module is useful for quantitative phase microscopy of live cells rapidly flowing in a micro-channel.

Practical gigahertz quantum key distribution robust against channel disturbance.

PubMed

Wang, Shuang; Chen, Wei; Yin, Zhen-Qiang; He, De-Yong; Hui, Cong; Hao, Peng-Lei; Fan-Yuan, Guan-Jie; Wang, Chao; Zhang, Li-Jun; Kuang, Jie; Liu, Shu-Feng; Zhou, Zheng; Wang, Yong-Gang; Guo, Guang-Can; Han, Zheng-Fu

2018-05-01

Quantum key distribution (QKD) provides an attractive solution for secure communication. However, channel disturbance severely limits its application when a QKD system is transferred from the laboratory to the field. Here a high-speed Faraday-Sagnac-Michelson QKD system is proposed that can automatically compensate for the channel polarization disturbance, which largely avoids the intermittency limitations of environment mutation. Over a 50 km fiber channel with 30 Hz polarization scrambling, the practicality of this phase-coding QKD system was characterized with an interference fringe visibility of 99.35% over 24 h and a stable secure key rate of 306 k bits/s over seven days without active polarization alignment.

VLSI single-chip (255,223) Reed-Solomon encoder with interleaver

NASA Technical Reports Server (NTRS)

Hsu, In-Shek (Inventor); Deutsch, Leslie J. (Inventor); Truong, Trieu-Kie (Inventor); Reed, Irving S. (Inventor)

1990-01-01

The invention relates to a concatenated Reed-Solomon/convolutional encoding system consisting of a Reed-Solomon outer code and a convolutional inner code for downlink telemetry in space missions, and more particularly to a Reed-Solomon encoder with programmable interleaving of the information symbols and code correction symbols to combat error bursts in the Viterbi decoder.

A depolarization and attenuation experiment using the COMSTAR and CTS satellites

NASA Technical Reports Server (NTRS)

Bostian, C. W.; Kauffman, S. R.; Manus, E. A.; Marshall, R. E.; Overstreet, W. P.; Persinger, R. R.; Stutzman, W. L.; Wiley, P. H.

1978-01-01

An experiment for measuring precipitation attenuation and depolarization on the CTS 11.7 and the COMSTAR 19.04 and 28.56 GHz downlinks is described. Attenuation scaling, effective path length, and the relationship between isolation and attenuation are discussed. Attenuation and effective path data are presented for the months of July, August, and September, 1977.

Integrated Solar Array and Reflectarray Antenna for High Bandwidth Cubesats

NASA Technical Reports Server (NTRS)

Lewis, Dorothy; Martinez, Andres; Petro, Andrew

2015-01-01

The Integrated Solar Array and Reflectarray Antenna (ISARA) mission will demonstrate a reflectarray antenna that increases downlink data rates for Cube- Sats from the existing baseline rate of 9.6 kilobits per second (kbps) to more than 100 megabits per second (Mbps). The ISARA spacecraft is slated for launch no earlier than Dec. 1, 2015.

Kuipers installs and routes RCS Video Cables in the U.S. Laboratory

NASA Image and Video Library

2012-02-01

ISS030-E-060117 (1 Feb. 2012) --- In the International Space Station?s Destiny laboratory, European Space Agency astronaut Andre Kuipers, Expedition 30 flight engineer, routes video cable for the High Rate Communication System (HRCS). HRCS will allow for two additional space-to-ground audio channels and two additional downlink video channels.

The Deep Space Network: A Radio Communications Instrument for Deep Space Exploration

NASA Technical Reports Server (NTRS)

Renzetti, N. A.; Stelzried, C. T.; Noreen, G. K.; Slobin, S. D.; Petty, S. M.; Trowbridge, D. L.; Donnelly, H.; Kinman, P. W.; Armstrong, J. W.; Burow, N. A.

1983-01-01

The primary purpose of the Deep Space Network (DSN) is to serve as a communications instrument for deep space exploration, providing communications between the spacecraft and the ground facilities. The uplink communications channel provides instructions or commands to the spacecraft. The downlink communications channel provides command verification and spacecraft engineering and science instrument payload data.

47 CFR 25.259 - Time sharing between NOAA meteorological satellite systems and non-voice, non-geostationary...

Code of Federal Regulations, 2014 CFR

2014-10-01

... satellite systems and non-voice, non-geostationary satellite systems in the 137-138 MHz band. 25.259 Section... systems and non-voice, non-geostationary satellite systems in the 137-138 MHz band. (a) The space stations of a non-voice, non-geostationary Mobile-Satellite Service (NVNG MSS) system time-sharing downlink...

47 CFR 25.259 - Time sharing between NOAA meteorological satellite systems and non-voice, non-geostationary...

Code of Federal Regulations, 2013 CFR

2013-10-01

... satellite systems and non-voice, non-geostationary satellite systems in the 137-138 MHz band. 25.259 Section... systems and non-voice, non-geostationary satellite systems in the 137-138 MHz band. (a) The space stations of a non-voice, non-geostationary Mobile-Satellite Service (NVNG MSS) system time-sharing downlink...

HST Solar Arrays photographed by Electronic Still Camera

NASA Technical Reports Server (NTRS)

1993-01-01

This close-up view of one of two Solar Arrays (SA) on the Hubble Space Telescope (HST) was photographed with an Electronic Still Camera (ESC), and downlinked to ground controllers soon afterward. Electronic still photography is a technology which provides the means for a handheld camera to electronically capture and digitize an image with resolution approaching film quality.

78 FR 1166 - Service Rules for the Advanced Wireless Services in the H Block-Implementing Section 6401 of the...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-08

... proposals regarding the licensing, use, and assignment of the spectrum, including the costs and benefits of... downlink band. Accordingly, we tentatively conclude that licensing the Upper H Block under flexible use... to our expectation, the record results in a determination that licensing the Upper H Block, the Lower...

Fractional Programming for Communication Systems—Part II: Uplink Scheduling via Matching

NASA Astrophysics Data System (ADS)

Shen, Kaiming; Yu, Wei

2018-05-01

This two-part paper develops novel methodologies for using fractional programming (FP) techniques to design and optimize communication systems. Part I of this paper proposes a new quadratic transform for FP and treats its application for continuous optimization problems. In this Part II of the paper, we study discrete problems, such as those involving user scheduling, which are considerably more difficult to solve. Unlike the continuous problems, discrete or mixed discrete-continuous problems normally cannot be recast as convex problems. In contrast to the common heuristic of relaxing the discrete variables, this work reformulates the original problem in an FP form amenable to distributed combinatorial optimization. The paper illustrates this methodology by tackling the important and challenging problem of uplink coordinated multi-cell user scheduling in wireless cellular systems. Uplink scheduling is more challenging than downlink scheduling, because uplink user scheduling decisions significantly affect the interference pattern in nearby cells. Further, the discrete scheduling variable needs to be optimized jointly with continuous variables such as transmit power levels and beamformers. The main idea of the proposed FP approach is to decouple the interaction among the interfering links, thereby permitting a distributed and joint optimization of the discrete and continuous variables with provable convergence. The paper shows that the well-known weighted minimum mean-square-error (WMMSE) algorithm can also be derived from a particular use of FP; but our proposed FP-based method significantly outperforms WMMSE when discrete user scheduling variables are involved, both in term of run-time efficiency and optimizing results.

A narrowband CDMA communications payload for little LEOS applications

NASA Astrophysics Data System (ADS)

Michalik, H.; Hävecker, W.; Ginati, A.

1996-09-01

In recent years Code Division Multiple Access (CDMA) techniques have been investigated for application in Local Area Networks [J. A. Salehi, IEEE Trans. Commun. 37 (1989)]as well as in Mobile Communications [R. Kohno et al., IEEE Commun. Mag. Jan (1995)]. The main attraction of these techniques is due to potential higher throughput and capacity of such systems under certain conditions compared to conventional multi-access schemes like frequency and time division multiplexing. Mobile communication over a Satellite Link represents in some terms the "worst case" for operating a CDMA-system. Considering e.g. the uplink case from mobile to satellite, the imperfections due to different and time varying channel conditions will add to the well known effects of Multiple Access Interference (MAI) between the simultaneously active users at the satellite receiver. In addition, bandwidth constraints due to the non-availability of large bandwidth channels in the interesting frequency bands, exist for small systems. As a result, for a given service in terms of user data rates, the practical code sequence lengths are limited as well as the available number of codes within a code set. In this paper a communications payload for Small Satellite Applications with CDMA uplink and C/TDMA downlink under the constraint of bandwidth limitations is proposed. To optimise the performance under the above addressed imperfections the system provides ability for power control and synchronisation for the CDMA uplink. The major objectives of this project are studying, development and testing of such a system for educational purposes and technology development at Hochschule Bremen.

Design and Performance Evaluation of a UWB Communication and Tracking System for Mini-AERCam

NASA Technical Reports Server (NTRS)

Barton, Richard J.

2005-01-01

NASA Johnson Space Center (JSC) is developing a low-volume, low-mass, robotic free-flying camera known as Mini-AERCam (Autonomous Extra-vehicular Robotic Camera) to assist the International Space Station (ISS) operations. Mini-AERCam is designed to provide astronauts and ground control real-time video for camera views of ISS. The system will assist ISS crewmembers and ground personnel to monitor ongoing operations and perform visual inspections of exterior ISS components without requiring extravehicular activity (EAV). Mini-AERCam consists of a great number of subsystems. Many institutions and companies have been involved in the R&D for this project. A Mini-AERCam ground control system has been studied at Texas A&M University [3]. The path planning and control algorithms that direct the motions of Mini-AERCam have been developed through the joint effort of Carnegie Mellon University and the Texas Robotics and Automation Center [5]. NASA JSC has designed a layered control architecture that integrates all functions of Mini-AERCam [8]. The research described in this report is part of a larger effort focused on the communication and tracking subsystem that is designed to perform three major tasks: 1. To transmit commands from ISS to Mini-AERCam for control of robotic camera motions (downlink); 2. To transmit real-time video from Mini-AERCam to ISS for inspections (uplink); 3. To track the position of Mini-AERCam for precise motion control. The ISS propagation environment is unique due to the nature of the ISS structure and multiple RF interference sources [9]. The ISS is composed of various truss segments, solar panels, thermal radiator panels, and modules for laboratories and crew accommodations. A tracking system supplemental to GPS is desirable both to improve accuracy and to eliminate the structural blockage due to the close proximity of the ISS which could at times limit the number of GPS satellites accessible to the Mini-AERCam. Ideally, the tracking system will be a passive component of the communication system which will need to operate in a time-varying multipath environment created as the robot camera moves over the ISS structure. In addition, due to many interference sources located on the ISS, SSO, LEO satellites and ground-based transmitters, selecting a frequency for the ISS and Mini-AERCam link which will coexist with all interferers poses a major design challenge. To meet all of these challenges, ultrawideband (UWB) radio technology is being studied for use in the Mini-AERCam communication and tracking subsystem. The research described in this report is focused on design and evaluation of passive tracking system algorithms based on UWB radio transmissions from mini-AERCam.

Aligning a Receiving Antenna Array to Reduce Interference

NASA Technical Reports Server (NTRS)

Jongeling, Andre P.; Rogstad, David H.

2009-01-01

A digital signal-processing algorithm has been devised as a means of aligning (as defined below) the outputs of multiple receiving radio antennas in a large array for the purpose of receiving a desired weak signal transmitted by a single distant source in the presence of an interfering signal that (1) originates at another source lying within the antenna beam and (2) occupies a frequency band significantly wider than that of the desired signal. In the original intended application of the algorithm, the desired weak signal is a spacecraft telemetry signal, the antennas are spacecraft-tracking antennas in NASA s Deep Space Network, and the source of the wide-band interfering signal is typically a radio galaxy or a planet that lies along or near the line of sight to the spacecraft. The algorithm could also afford the ability to discriminate between desired narrow-band and nearby undesired wide-band sources in related applications that include satellite and terrestrial radio communications and radio astronomy. The development of the present algorithm involved modification of a prior algorithm called SUMPLE and a predecessor called SIMPLE. SUMPLE was described in Algorithm for Aligning an Array of Receiving Radio Antennas (NPO-40574), NASA Tech Briefs Vol. 30, No. 4 (April 2006), page 54. To recapitulate: As used here, aligning signifies adjusting the delays and phases of the outputs from the various antennas so that their relatively weak replicas of the desired signal can be added coherently to increase the signal-to-noise ratio (SNR) for improved reception, as though one had a single larger antenna. Prior to the development of SUMPLE, it was common practice to effect alignment by means of a process that involves correlation of signals in pairs. SIMPLE is an example of an algorithm that effects such a process. SUMPLE also involves correlations, but the correlations are not performed in pairs. Instead, in a partly iterative process, each signal is appropriately weighted and then correlated with a composite signal equal to the sum of the other signals.

Paramagnetic dysprosium-doped zinc oxide thin films grown by pulsed-laser deposition

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

Lo, Fang-Yuh, E-mail: fangyuhlo@ntnu.edu.tw; Ting, Yi-Chieh; Chou, Kai-Chieh

2015-06-07

Dysprosium(Dy)-doped zinc oxide (Dy:ZnO) thin films were fabricated on c-oriented sapphire substrate by pulsed-laser deposition with doping concentration ranging from 1 to 10 at. %. X-ray diffraction (XRD), Raman-scattering, optical transmission spectroscopy, and spectroscopic ellipsometry revealed incorporation of Dy into ZnO host matrix without secondary phase. Solubility limit of Dy in ZnO under our deposition condition was between 5 and 10 at. % according to XRD and Raman-scattering characteristics. Optical transmission spectroscopy and spectroscopic ellipsometry also showed increase in both transmittance in ultraviolet regime and band gap of Dy:ZnO with increasing Dy density. Zinc vacancies and zinc interstitials were identified by photoluminescencemore » spectroscopy as the defects accompanied with Dy incorporation. Magnetic investigations with a superconducting quantum interference device showed paramagnetism without long-range order for all Dy:ZnO thin films, and a hint of antiferromagnetic alignment of Dy impurities was observed at highest doping concentration—indicating the overall contribution of zinc vacancies and zinc interstitials to magnetic interaction was either neutral or toward antiferromagnetic. From our investigations, Dy:ZnO thin films could be useful for spin alignment and magneto-optical applications.« less

Alignment of the hydrogen molecule under intense laser fields

DOE PAGES

Lopez, Gary V.; Fournier, Martin; Jankunas, Justin; ...

2017-06-01

Alignment, dissociation and ionization of H 2 molecules in the ground or the electronically excited E,F state of the H 2 molecule are studied and contrasted using the Velocity Mapping Imaging (VMI) technique. Photoelectron images from nonresonant 7-, 8- and 9-photon radiation ionization of H 2 show that the intense laser fields create ponderomotive shifts in the potential energy surfaces and distort the velocity of the emitted electrons that are produced from ionization. Photofragment images of H+ due to the dissociation mechanism that follows the 2-photon excitation into the (E,F; v = 0, J = 0, 1) electronic state showmore » a strong dependence on laser intensity, which is attributed to the high polarizability of the H 2 (E,F) state. For transitions from the J = 0 state, particularly, we observe marked structure in the angular distribution, which we explain as the interference between the prepared J = 0 and Stark-mixed J = 2 rovibrational states of H 2, as the laser intensity increases. Quantification of these effects allows us to extract the molecular polarizability of the H 2 (E,F) state, and yields a value of 103 ± 37 A.U.« less

Alignment of the hydrogen molecule under intense laser fields

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

Lopez, Gary V.; Fournier, Martin; Jankunas, Justin

Alignment, dissociation and ionization of H 2 molecules in the ground or the electronically excited E,F state of the H 2 molecule are studied and contrasted using the Velocity Mapping Imaging (VMI) technique. Photoelectron images from nonresonant 7-, 8- and 9-photon radiation ionization of H 2 show that the intense laser fields create ponderomotive shifts in the potential energy surfaces and distort the velocity of the emitted electrons that are produced from ionization. Photofragment images of H+ due to the dissociation mechanism that follows the 2-photon excitation into the (E,F; v = 0, J = 0, 1) electronic state showmore » a strong dependence on laser intensity, which is attributed to the high polarizability of the H 2 (E,F) state. For transitions from the J = 0 state, particularly, we observe marked structure in the angular distribution, which we explain as the interference between the prepared J = 0 and Stark-mixed J = 2 rovibrational states of H 2, as the laser intensity increases. Quantification of these effects allows us to extract the molecular polarizability of the H 2 (E,F) state, and yields a value of 103 ± 37 A.U.« less

Kadenza: Kepler/K2 Raw Cadence Data Reader

NASA Astrophysics Data System (ADS)

Barentsen, Geert; Cardoso, José Vinícius de Miranda

2018-03-01

Kadenza enables time-critical data analyses to be carried out using NASA's Kepler Space Telescope. It enables users to convert Kepler's raw data files into user-friendly Target Pixel Files upon downlink from the spacecraft. The primary motivation for this tool is to enable the microlensing, supernova, and exoplanet communities to create quicklook lightcurves for transient events which require rapid follow-up.

Rapid toxicity detection in water quality control utilizing automated multispecies biomonitoring for permanent space stations

NASA Technical Reports Server (NTRS)

Morgan, E. L.; Young, R. C.; Smith, M. D.; Eagleson, K. W.

1986-01-01

The objective of this study was to evaluate proposed design characteristics and applications of automated biomonitoring devices for real-time toxicity detection in water quality control on-board permanent space stations. Simulated tests in downlinking transmissions of automated biomonitoring data to Earth-receiving stations were simulated using satellite data transmissions from remote Earth-based stations.

Personnel in blue and white FCR bldg 30 during STS-106

NASA Image and Video Library

2000-09-19

JSC2000-E-22831 (13 September 2000) --- Astronauts Barbara R. Morgan and Chris A. Hadfield listen to downlinked audio from the Space Shuttle Atlantis at the approximate midway point of the STS-106 mission. The two are working at the Spacecraft Communicator (CAPCOM) console in Houston's Mission Control Center (MCC). Nearby is Bill Reeves at the Flight Director console.

Burbank uses video camera during installation and routing of HRCS Video Cables

NASA Image and Video Library

2012-02-01

ISS030-E-060104 (1 Feb. 2012) --- NASA astronaut Dan Burbank, Expedition 30 commander, uses a video camera in the Destiny laboratory of the International Space Station during installation and routing of video cable for the High Rate Communication System (HRCS). HRCS will allow for two additional space-to-ground audio channels and two additional downlink video channels.

Autonomous Science on the EO-1 Mission

NASA Technical Reports Server (NTRS)

Chien, S.; Sherwood, R.; Tran, D.; Castano, R.; Cichy, B.; Davies, A.; Rabideau, G.; Tang, N.; Burl, M.; Mandl, D.;

Education Payload Operation - Kit D

NASA Technical Reports Server (NTRS)

Keil, Matthew

2009-01-01

Education Payload Operation - Kit D (EPO-Kit D) includes education items that will be used to support the live International Space Station (ISS) education downlinks and Education Payload Operation (EPO) demonstrations onboard the ISS. The main objective of EPO-Kit D supports the National Aeronautics and Space Administration (NASA) goal of attracting students to study and seek careers in science, technology, engineering, and mathematics.

Fade Analysis of ORCA DATA Beam at NTTR and Pax River

DTIC Science & Technology

2010-08-01

bit-error-rate (BER) of the data beam on the downlink path. 15 Start Time-PST (Duration) Range Scin Index 1 Rx=5.1cm... Scin Index 2 Rx=13.7cm Scin Index 3 Rx=27.2cm Path Ave Cn2 (m-2/3) Path Ave Inner Scale Path Ave Outer Scale Flight 2 May 16

Department of Education ISS Link

NASA Image and Video Library

2009-11-05

NASA Administrator Charles F. Bolden, center, stands with two unidentified students as he performs a demonstration to illustrate how far the International Space Station is from the Earth in comparison with the Moon, during an event where students spoke via downlink to astronauts on the ISS, Thursday, Nov. 5, 2009, at the U.S. Department of Education in Washington. Photo Credit: (NASA/Paul E. Alers)

Digital aerial sketchmapping and downlink communications: a new tool for fire managers

Treesearch

Everett Hinkley; Tom Zajkowski; Charlie Schrader-Patton

2010-01-01

Aerial sketchmapping is the geolocating of features that are seen on the ground below an aircraft and the subsequent recording of those features. Traditional aerial sketchmapping methods required hand-sketching on hardcopy maps or photos and the translation of that information to a digital file. In 1996, the U.S. Department of Agriculture (USDA) Forest Service embarked...

47 CFR 25.260 - Time sharing between DoD meteorological satellite systems and non-voice, non-geostationary...

Code of Federal Regulations, 2014 CFR

2014-10-01

... satellite systems and non-voice, non-geostationary satellite systems in the 400.15-401 MHz band. 25.260... systems and non-voice, non-geostationary satellite systems in the 400.15-401 MHz band. (a) The space stations of a non-voice, non-geostationary Mobile-Satellite Service (NVNG MSS) system time-sharing downlink...

47 CFR 25.260 - Time sharing between DoD meteorological satellite systems and non-voice, non-geostationary...

Code of Federal Regulations, 2013 CFR

2013-10-01

... satellite systems and non-voice, non-geostationary satellite systems in the 400.15-401 MHz band. 25.260... systems and non-voice, non-geostationary satellite systems in the 400.15-401 MHz band. (a) The space stations of a non-voice, non-geostationary Mobile-Satellite Service (NVNG MSS) system time-sharing downlink...

Millimeter wave propagation measurements using the ATS 5 satellite

NASA Technical Reports Server (NTRS)

Ippolito, L. J.

1972-01-01

The ATS 5 millimeter wave propagation experiment determines long- and short-term attenuation statistics of operational millimeter wavelength earthspace links as functions of defined meteorological conditions. A preliminary analysis of results with 15 GHz downlink and 32 GHz uplink frequency bands indicates that both frequency bands exhibit an excellent potential for utilization in reliable high data rate earth-space communications systems.

NPS-SCAT: A CubeSat Communications System Design, Test, and Integration

DTIC Science & Technology

2009-06-01

used two patch antennas for the S-Band transceiver and a quad-canted turnstile antenna for the downlink in the 70-centimeter band ( Tuli , Orr, & Zee...Service. Retrieved March 08, 2009, from Cute-1.7 + APD II Project: http://lss.mes.titech.ac.jp/ssp/cute1.7/amateur_servic e_e.html Tuli , T.S., Orr

Autonomous planning and scheduling on the TechSat 21 mission

NASA Technical Reports Server (NTRS)

Sherwood, R.; Chien, S.; Castano, R.; Rabideau, G.

2002-01-01

The Autonomous Sciencecraft Experiment (ASE) will fly onboard the Air Force TechSat 21 constellation of three spacecraft scheduled for launch in 2006. ASE uses onboard continuous planning, robust task and goal-based execution, model-based mode identification and reconfiguration, and onboard machine learning and pattern recognition to radically increase science return by enabling intelligent downlink selection and autonomous retargeting.

Chinese Spacesuit Analysis

NASA Technical Reports Server (NTRS)

Croog, Lewis

2010-01-01

In 2008, China became only the 3rd nation to perform an Extravehicular Activity (EVA) from a spacecraft. An overview of the Chinese spacesuit and life support system were assessed from video downlinks during their EVA; from those assessments, spacesuit characteristics were identified. The spacesuits were compared against the Russian Orlan Spacesuit and the U.S. Extravehicular Mobility Unit (EMU). China's plans for future missions also were presented.

Downlink Cooperative Broadcast Transmission Based on Superposition Coding in a Relaying System for Future Wireless Sensor Networks.

PubMed

Liu, Yang; Han, Guangjie; Shi, Sulong; Li, Zhengquan

2018-06-20

This study investigates the superiority of cooperative broadcast transmission over traditional orthogonal schemes when applied in a downlink relaying broadcast channel (RBC). Two proposed cooperative broadcast transmission protocols, one with an amplify-and-forward (AF) relay, and the other with a repetition-based decode-and-forward (DF) relay, are investigated. By utilizing superposition coding (SupC), the source and the relay transmit the private user messages simultaneously instead of sequentially as in traditional orthogonal schemes, which means the channel resources are reused and an increased channel degree of freedom is available to each user, hence the half-duplex penalty of relaying is alleviated. To facilitate a performance evaluation, theoretical outage probability expressions of the two broadcast transmission schemes are developed, based on which, we investigate the minimum total power consumption of each scheme for a given traffic requirement by numerical simulation. The results provide details on the overall system performance and fruitful insights on the essential characteristics of cooperative broadcast transmission in RBCs. It is observed that better overall outage performances and considerable power gains can be obtained by utilizing cooperative broadcast transmissions compared to traditional orthogonal schemes.

Ka-Band Transponder for Deep-Space Radio Science

NASA Technical Reports Server (NTRS)

Dennis, Matthew S.; Mysoor, Narayan R.; Folkner, William M.; Mendoza, Ricardo; Venkatesan, Jaikrishna

2008-01-01

A one-page document describes a Ka-band transponder being developed for use in deep-space radio science. The transponder receives in the Deep Space Network (DSN) uplink frequency band of 34.2 to 34.7 GHz, transmits in the 31.8- to 32.3 GHz DSN downlink band, and performs regenerative ranging on a DSN standard 4-MHz ranging tone subcarrier phase-modulated onto the uplink carrier signal. A primary consideration in this development is reduction in size, relative to other such transponders. The transponder design is all-analog, chosen to minimize not only the size but also the number of parts and the design time and, thus, the cost. The receiver features two stages of frequency down-conversion. The receiver locks onto the uplink carrier signal. The exciter signal for the transmitter is derived from the same source as that used to generate the first-stage local-oscillator signal. The ranging-tone subcarrier is down-converted along with the carrier to the second intermediate frequency, where the 4-MHz tone is demodulated from the composite signal and fed into a ranging-tone-tracking loop, which regenerates the tone. The regenerated tone is linearly phase-modulated onto the downlink carrier.

PHY-DLL dialogue: cross-layer design for optical-wireless OFDM downlink transmission

NASA Astrophysics Data System (ADS)

Wang, Xuguo; Li, Lee

2005-11-01

The use of radio over fiber to provide radio access has a number of advantages including the ability to deploy small, low-cost remote antenna units and ease of upgrade. And due to the great potential for increasing the capacity and quality of service, the combination of Orthogonal Frequency Division Multiplexing (OFDM) modulation and the sub-carrier multiplexed optical transmission is one of the best solutions for the future millimeter-wave mobile communication. And this makes the optimum utility of valuable radio resources essential. This paper devises a cross-layer adaptive algorithm for optical-wireless OFDM system, which takes into consideration not only transmission power limitation in the physical layer, but also traffic scheduling and user fairness at the data-link layer. According to proportional fairness principle and water-pouring theorem, we put forward the complete description of this cross-layer adaptive downlink transmission 6-step algorithm. Simulation results show that the proposed cross-layer algorithm outperforms the mere physical layer adaptive algorithm markedly. The novel scheme is able to improve performance of the packet success rate per time chip and average packet delay, support added active users.

Frequency Domain Beamforming for a Deep Space Network Downlink Array

NASA Technical Reports Server (NTRS)

Navarro, Robert

2012-01-01

This paper describes a frequency domain beamformer to array up to 8 antennas of NASA's Deep Space Network currently in development. The objective of this array is to replace and enhance the capability of the DSN 70m antennas with multiple 34m antennas for telemetry, navigation and radio science use. The array will coherently combine the entire 500 MHz of usable bandwidth available to DSN receivers. A frequency domain beamforming architecture was chosen over a time domain based architecture to handle the large signal bandwidth and efficiently perform delay and phase calibration. The antennas of the DSN are spaced far enough apart that random atmospheric and phase variations between antennas need to be calibrated out on an ongoing basis in real-time. The calibration is done using measurements obtained from a correlator. This DSN Downlink Array expands upon a proof of concept breadboard array built previously to develop the technology and will become an operational asset of the Deep Space Network. Design parameters for frequency channelization, array calibration and delay corrections will be presented as well a method to efficiently calibrate the array for both wide and narrow bandwidth telemetry.

GIS Methodology for Planning Planetary-Rover Operations

NASA Technical Reports Server (NTRS)

Powell, Mark; Norris, Jeffrey; Fox, Jason; Rabe, Kenneth; Shu, I-Hsiang

2007-01-01

A document describes a methodology for utilizing image data downlinked from cameras aboard a robotic ground vehicle (rover) on a remote planet for analyzing and planning operations of the vehicle and of any associated spacecraft. Traditionally, the cataloging and presentation of large numbers of downlinked planetary-exploration images have been done by use of two organizational methods: temporal organization and correlation between activity plans and images. In contrast, the present methodology involves spatial indexing of image data by use of the computational discipline of geographic information systems (GIS), which has been maturing in terrestrial applications for decades, but, until now, has not been widely used in support of exploration of remote planets. The use of GIS to catalog data products for analysis is intended to increase efficiency and effectiveness in planning rover operations, just as GIS has proven to be a source of powerful computational tools in such terrestrial endeavors as law enforcement, military strategic planning, surveying, political science, and epidemiology. The use of GIS also satisfies the need for a map-based user interface that is intuitive to rover-activity planners, many of whom are deeply familiar with maps and know how to use them effectively in field geology.

Design of a high-current downlink using Bi-based superconductors

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

Fisher, B.L.; Lanagan, M.T.; Balachandran, U.

1996-08-01

Recent processing developments in Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}0{sub x} (BSCCO-2223) bars have produced bulk BSCCO-2223 bars with properties advantageous for power applications. Cold isostatically pressed (CIP) and sinter-forged BSCCO-2223 both have low AC loss, which make them desirable for use in power devices. Thermal conductivity of the CIP bars is lower than that of the previously used sinter-forged samples by a factor of 2. CIP bars with cross-sectional areas of =0.75 cm{sup 2} and carrying 250 A RMS transport current have AC loss values of 30 pJ/cycle-cm at 50 Hz and 77 K. A pair of prototype downlinksmore » were designed and built with sinter forged bars to deliver a continuous AC current of 1500 A over a temperature gradient of 77 to 4.2 K while delivering about -200 MW of heat to the liquid-helium-cooled end. This paper will discuss the design considerations and modeling of downlinks, which supply high AC currents over the 77 to 4.2 K temperature gradient with low thermal losses.« less

Adaptive spatial filtering of daytime sky noise in a satellite quantum key distribution downlink receiver

NASA Astrophysics Data System (ADS)

Gruneisen, Mark T.; Sickmiller, Brett A.; Flanagan, Michael B.; Black, James P.; Stoltenberg, Kurt E.; Duchane, Alexander W.

2016-02-01

Spatial filtering is an important technique for reducing sky background noise in a satellite quantum key distribution downlink receiver. Atmospheric turbulence limits the extent to which spatial filtering can reduce sky noise without introducing signal losses. Using atmospheric propagation and compensation simulations, the potential benefit of adaptive optics (AO) to secure key generation (SKG) is quantified. Simulations are performed assuming optical propagation from a low-Earth-orbit satellite to a terrestrial receiver that includes AO. Higher-order AO correction is modeled assuming a Shack-Hartmann wavefront sensor and a continuous-face-sheet deformable mirror. The effects of atmospheric turbulence, tracking, and higher-order AO on the photon capture efficiency are simulated using statistical representations of turbulence and a time-domain wave-optics hardware emulator. SKG rates are calculated for a decoy-state protocol as a function of the receiver field of view for various strengths of turbulence, sky radiances, and pointing angles. The results show that at fields of view smaller than those discussed by others, AO technologies can enhance SKG rates in daylight and enable SKG where it would otherwise be prohibited as a consequence of background optical noise and signal loss due to propagation and turbulence effects.

Ka-band study: 1988

NASA Technical Reports Server (NTRS)

Layland, J. W.; Horttor, R. L.; Clauss, R. C.; Wilcher, J. H.; Wallace, R. J.; Mudgway, D. J.

1989-01-01

The Ka-band study team was chartered in late 1987 to bring together all the planning elements for establishing 32 GHz (Ka-band) as the primary downlink frequency for deep-space operation, and to provide a stable baseline from which to pursue that development. This article summarizes the results of that study at its conclusion in mid-1988, and corresponds to material presented to NASA's Office of Space Operations on July 14, 1988. For a variety of reasons, Ka-band is the right next major step in deep-space communications. It offers improved radio metric accuracy through reduced plasma sensitivity and increased bandwidth. Because of these improvements, it offers the opportunity to reduce costs in the flight radio system or in the DSN by allocating part of the overall benefits of Ka-band to this cost reduction. A mission scenario is being planned that can drive at least two and possibly all three of the DSN subnets to provide a Ka-band downlink capability by the turn of the century. The implementation scenario devised by the study team is believed to be feasible within reasonable resource expectations, and capable of providing the needed upgrade as a natural follow-on to the technology development which is already underway.

Telemetry-Enhancing Scripts

NASA Technical Reports Server (NTRS)

Maimone, Mark W.

2009-01-01

Scripts Providing a Cool Kit of Telemetry Enhancing Tools (SPACKLE) is a set of software tools that fill gaps in capabilities of other software used in processing downlinked data in the Mars Exploration Rovers (MER) flight and test-bed operations. SPACKLE tools have helped to accelerate the automatic processing and interpretation of MER mission data, enabling non-experts to understand and/or use MER query and data product command simulation software tools more effectively. SPACKLE has greatly accelerated some operations and provides new capabilities. The tools of SPACKLE are written, variously, in Perl or the C or C++ language. They perform a variety of search and shortcut functions that include the following: Generating text-only, Event Report-annotated, and Web-enhanced views of command sequences; Labeling integer enumerations with their symbolic meanings in text messages and engineering channels; Systematic detecting of corruption within data products; Generating text-only displays of data-product catalogs including downlink status; Validating and labeling of commands related to data products; Performing of convenient searches of detailed engineering data spanning multiple Martian solar days; Generating tables of initial conditions pertaining to engineering, health, and accountability data; Simplified construction and simulation of command sequences; and Fast time format conversions and sorting.

Two-Level Scheduling for Video Transmission over Downlink OFDMA Networks

PubMed Central

Tham, Mau-Luen

2016-01-01

This paper presents a two-level scheduling scheme for video transmission over downlink orthogonal frequency-division multiple access (OFDMA) networks. It aims to maximize the aggregate quality of the video users subject to the playback delay and resource constraints, by exploiting the multiuser diversity and the video characteristics. The upper level schedules the transmission of video packets among multiple users based on an overall target bit-error-rate (BER), the importance level of packet and resource consumption efficiency factor. Instead, the lower level renders unequal error protection (UEP) in terms of target BER among the scheduled packets by solving a weighted sum distortion minimization problem, where each user weight reflects the total importance level of the packets that has been scheduled for that user. Frequency-selective power is then water-filled over all the assigned subcarriers in order to leverage the potential channel coding gain. Realistic simulation results demonstrate that the proposed scheme significantly outperforms the state-of-the-art scheduling scheme by up to 6.8 dB in terms of peak-signal-to-noise-ratio (PSNR). Further test evaluates the suitability of equal power allocation which is the common assumption in the literature. PMID:26906398

Hydrostatic Pressure and Temperature Measurements Using an In-Line Mach-Zehnder Interferometer Based on a Two-Mode Highly Birefringent Microstructured Fiber

PubMed Central

Statkiewicz-Barabach, Gabriela; Olszewski, Jacek; Mergo, Pawel; Urbanczyk, Waclaw.

2017-01-01

We present a comprehensive study of an in-line Mach-Zehnder intermodal interferometer fabricated in a boron-doped two-mode highly birefringent microstructured fiber. We observed different interference signals at the output of the interferometer, related to the intermodal interference of the fundamental and the first order modes of the orthogonal polarizations and a beating of the polarimetric signal related to the difference in the group modal birefringence between the fundamental and the first order modes, respectively. The proposed interferometer was tested for measurements of hydrostatic pressure and temperature for different alignments of the input polarizer with no analyzer at the output. The sensitivities to hydrostatic pressure of the intermodal interference signals for x- and y-polarizations had an opposite sign and were equal to 0.229 nm/MPa and −0.179 nm/MPa, respectively, while the temperature sensitivities for both polarizations were similar and equal 0.020 nm/°C and 0.019 nm/°C. In the case of pressure, for the simultaneous excitation of both polarization modes, we observed a displacement of intermodal fringes with a sensitivity depending on the azimuth of the input polarization state, as well as on the displacement of their envelope with a sensitivity of 2.14 nm/MPa, accompanied by a change in the fringes visibility. Such properties of the proposed interferometer allow for convenient adjustments to the pressure sensitivity of the intermodal fringes and possible applications for the simultaneous interrogation of temperature and pressure. PMID:28718796

Evaluation of a method to shield a welding electron beam from magnetic interference

NASA Technical Reports Server (NTRS)

Wall, W. A.

1976-01-01

It is known that electron beams are easily deflected by magnetic and electrostatic fields. Therefore, to prevent weld defects, stray electromagnetic fields are avoided in electron beam welding chambers if at all possible. The successful results of tests conducted at MSFC to evaluate a simple magnetic shield made from steel tubing are reported. Tests indicate that this shield was up to 85 percent effective in reducing magnetic effects on the electron beam of a welding machine. In addition, residual magnetic fields within the shield were so nearly uniform that the net effect on the beam alignment was negligible. It is concluded that the shield, with the addition of a tungsten liner, could be used in production welding.

High-pressure needle interface for thermoplastic microfluidics.

PubMed

Chen, C F; Liu, J; Hromada, L P; Tsao, C W; Chang, C C; DeVoe, D L

2009-01-07

A robust and low dead volume world-to-chip interface for thermoplastic microfluidics has been developed. The high pressure fluidic port employs a stainless steel needle inserted into a mating hole aligned to an embedded microchannel, with an interference fit used to increase pressure resistance. Alternately, a self-tapping threaded needle screwed into a mating hole is also demonstrated. In both cases, the flat bottom needle ports seat directly against the microchannel substrate, ensuring low interfacial dead volumes. Low dispersion is observed for dye bands passing the interfaces. The needle ports offer sufficient pull-out forces for applications such as liquid chromatography that require high internal fluid pressures, with the epoxy-free interfaces compatible with internal microchannel pressures above 40 MPa.

Master dye laser oscillator including a specific grating assembly for use therein

DOEpatents

Davin, James M.

1992-01-01

A dye laser oscillator for producing a tuned dye beam is disclosed herein and includes, among other components, a beam output coupling assembly, a dye cell assembly, a beam expander assembly, an etalon assembly, and a grating assembly. Each of three assemblies is vertically supported from a horizontal base so as to be readily removable from the base without interference from or interfering with the other assemblies. The particular grating assembly disclosed is specifically designed for proper optical alignment with the intended path of the dye beam to be produced and for accurate pivotal movement relative to the beam path in order to function as a coarse tuning mechanism in the production of the ultimately tuned beam.

Master dye laser oscillator including a specific grating assembly for use therein

DOEpatents

Davin, J.M.

1992-09-01

A dye laser oscillator for producing a tuned dye beam is disclosed herein and includes, among other components, a beam output coupling assembly, a dye cell assembly, a beam expander assembly, an etalon assembly, and a grating assembly. Each of three assemblies is vertically supported from a horizontal base so as to be readily removable from the base without interference from or interfering with the other assemblies. The particular grating assembly disclosed is specifically designed for proper optical alignment with the intended path of the dye beam to be produced and for accurate pivotal movement relative to the beam path in order to function as a coarse tuning mechanism in the production of the ultimately tuned beam. 5 figs.

Dual-beam, second-derivative tunable diode-laser infrared spectroscopy applied to trace-gas measurement

NASA Astrophysics Data System (ADS)

Tallant, D. R.; Jungst, R. G.

1981-04-01

A dual base diode laser spectrometer was constructed using off axis reflective optics. The spectrometer was amplitude modulated for direct absorption measurements or frequency modulated to obtain derivative spectra. The spectrometer had: high throughput; was easy to operate and align; provided good dual beam compensation; and had no evidence of the interference effects that were observed in diode laser spectrometers using refractive optics. Unpurged, using second derivative techniques, the instrument measured 108 parts per million CO (10/cm absorption cell, atmospheric pressure broadened) with good signal/noise. With the replacement of marginal instrumental components, the signal/noise was substantially increased. This instrument was developed to monitor the evolution of decomposition gases in sealed containers of small volume at atmospheric pressure.

Solid optical ring interferometer for high-throughput feedback-free spectral analysis and filtering

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

Petrak, B.; Peiris, M.; Muller, A., E-mail: mullera@usf.edu

2015-02-15

We describe a simple and inexpensive optical ring interferometer for use in high-resolution spectral analysis and filtering. It consists of a solid cuboid, reflection-coated on two opposite sides, in which constructive interference occurs for waves in a rhombic trajectory. Due to its monolithic design, the interferometer’s resonance frequencies are insensitive to environmental disturbances over time. Additional advantages are its simplicity of alignment, high-throughput, and feedback-free operation. If desired, it can be stabilized with a secondary laser without disturbance of the primary signal. We illustrate the use of the interferometer for the measurement of the spectral Mollow triplet from a quantummore » dot and characterize its long-term stability for filtering applications.« less

Discovery of novel bacterial RNA polymerase inhibitors: pharmacophore-based virtual screening and hit optimization.

PubMed

Hinsberger, Stefan; Hüsecken, Kristina; Groh, Matthias; Negri, Matthias; Haupenthal, Jörg; Hartmann, Rolf W

2013-11-14

The bacterial RNA polymerase (RNAP) is a validated target for broad spectrum antibiotics. However, the efficiency of drugs is reduced by resistance. To discover novel RNAP inhibitors, a pharmacophore based on the alignment of described inhibitors was used for virtual screening. In an optimization process of hit compounds, novel derivatives with improved in vitro potency were discovered. Investigations concerning the molecular mechanism of RNAP inhibition reveal that they prevent the protein-protein interaction (PPI) between σ(70) and the RNAP core enzyme. Besides of reducing RNA formation, the inhibitors were shown to interfere with bacterial lipid biosynthesis. The compounds were active against Gram-positive pathogens and revealed significantly lower resistance frequencies compared to clinically used rifampicin.

MATISSE: alignment, integration, and test phase first results

NASA Astrophysics Data System (ADS)

Allouche, F.; Robbe-Dubois, S.; Lagarde, S.; Cruzalèbes, P.; Antonelli, P.; Bresson, Y.; Fantei-Caujolle, Y.; Marcotto, A.; Morel, S.; Beckmann, U.; Bettonvil, F.; Berio, Ph.; Heininger, M.; Lehmitz, M.; Agocs, T.; Brast, R.; Elswijk, E.; Ives, D.; Meixner, K.; Laun, W.; Mellein, M.; Neumann, U.; Bailet, C.; Clausse, J.-M.; Matter, A.; Meilland, A.; Millour, F.; Petrov, R. G.; Accardo, M.; Bristow, P.; Frahm, R.; Glindemann, A.; Gonzáles Herrera, J.-C.; Lizon, J.-L.; Schöller, M.; Graser, U.; Jaffe, W.; Lopez, B.

2016-08-01

MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the spectro-interferometer for the VLTI of the European Southern Observatory, operating in near and mid-infrared, and combining up to four beams from the unit or the auxiliary telescopes. MATISSE will offer new breakthroughs in the study of circumstellar environments by allowing the multispectral mapping of the material distribution, the gas and essentially the dust. The instrument consists in a warm optical system (WOP) accepting four optical beams and relaying them after a dichroic splitting (for the L and M- and N- spectral bands) to cold optical benches (COB) located in two separate cryostats. The Observatoire de la Côte d'Azur is in charge of the WOP providing the spectral band separation, optical path equalization and modulation, pupil positioning, beam anamorphosis, beam commutation, and calibration. NOVA-ASTRON is in charge of the COB providing the functions of beam selection, reduction of thermal background emission, spatial filtering, pupil transfer, photometry and interferometry splitting, additional beam anamorphosis, spectral filtering, polarization selection, image dispersion, and image combination. The Max Planck Institut für Radio Astronomie is in charge of the operation and performance validation of the two detectors, a HAWAII-2RG from Teledyne for the L- and M- bands and a Raytheon AQUARIUS for the N-band. Both detectors are provided by ESO. The Max Planck Institut für Astronomie is in charge of the electronics and the cryostats for which the requirements on space limitations and vibration stability resulted on very specific and stringent decisions on the design. The integration and test of the COB: the two cryogenic systems, including the cold benches and the detectors, have been conducted at MPIA in parallel with the integration of the WOP at OCA. At the end of 2014, the complete instrument was integrated at OCA. Following this integration, a period of interface and alignment between the COB and the WOP took place resulting in the first interference fringes in the L-band during summer 2015 and the first interference fringes in the N-ban in March 2016. After a period of optimization of both the instrument reliability and the environmental working conditions, the test plan is presently being conducted in order to evaluate the complete performance of the instrument and its compliance with the high-level requirements. The present paper gives the first results of the alignment, integration and test phase of the MATISSE instrument.

A cascaded coding scheme for error control

NASA Technical Reports Server (NTRS)

Shu, L.; Kasami, T.

1985-01-01

A cascade coding scheme for error control is investigated. The scheme employs a combination of hard and soft decisions in decoding. Error performance is analyzed. If the inner and outer codes are chosen properly, extremely high reliability can be attained even for a high channel bit-error-rate. Some example schemes are evaluated. They seem to be quite suitable for satellite down-link error control.

A cascaded coding scheme for error control

NASA Technical Reports Server (NTRS)

Kasami, T.; Lin, S.

1985-01-01

A cascaded coding scheme for error control was investigated. The scheme employs a combination of hard and soft decisions in decoding. Error performance is analyzed. If the inner and outer codes are chosen properly, extremely high reliability can be attained even for a high channel bit-error-rate. Some example schemes are studied which seem to be quite suitable for satellite down-link error control.

Guidance system operations plan for manned LM earth orbital and lunar missions using program luminary 1E. Section 2: Data links

NASA Technical Reports Server (NTRS)

Hamilton, M. H.

1972-01-01

Data links for the guidance system of manned lunar module orbital and lunar missions are presented. Subjects discussed are: (1) digital uplink to lunar module, (2) lunar module liftoff time increment, (3) lunar module contiguous block update, (4) lunar module scatter update, (5) lunar module digital downlink, and (6) absolute addresses for update program.

SAR Imaging through the Earth’s Ionosphere

DTIC Science & Technology

2013-11-06

or, otherwise, if polarimetry puts too high of a demand on storage, downlink capacity, etc.), then the approach based on the Faraday rotation is not...reflected fields for both are the same in the first Born approximation. Modern practical applications of radar polarimetry employ different empirical and...Fruneau, and J.-P. Rudant. Classification of tropical vegetation using multifrequency partial SAR polarimetry . IEEE Geoscience and Remote Sensing Letters

National Space Transportation System telemetry distribution and processing, NASA-JFK Space Center/Cape Canaveral

NASA Technical Reports Server (NTRS)

Jenkins, George

1986-01-01

Prelaunch, launch, mission, and landing distribution of RF and hardline uplink/downlink information between Space Shuttle Orbiter/cargo elements, tracking antennas, and control centers at JSC, KSC, MSFC, GSFC, ESMC/RCC, and Sunnyvale are presented as functional block diagrams. Typical mismatch problems encountered during spacecraft-to-project control center telemetry transmissions are listed along with new items for future support enhancement.

MS Grunsfeld changes film using film bag

NASA Image and Video Library

1997-01-16

S81-E-05468 (16 Jan. 1997) --- To protect it from exposure to light, astronaut John M. Grunsfeld, mission specialist, uses a black bag to change out a film magazine on a 70mm handheld camera during mid-week activity aboard the Space Shuttle Atlantis. The photograph was recorded with an Electronic Still Camera (ESC) and later was downlinked to flight controllers in Houston, Texas.

Circuit-switch architecture for a 30/20-GHz FDMA/TDM geostationary satellite communications network

NASA Technical Reports Server (NTRS)

Ivancic, William D.

1992-01-01

A circuit switching architecture is described for a 30/20 GHz frequency division, multiple access uplink/time division multiplexed downlink (FDMA/TDM) geostationary satellite communications network. Critical subsystems and problem areas are identified and addressed. Work was concentrated primarily on the space segment; however, the ground segment was considered concurrently to ensure cost efficiency and realistic operational constraints.

National Space Transportation System telemetry distribution and processing, NASA-JFK Space Center/Cape Canaveral

NASA Astrophysics Data System (ADS)

Jenkins, George

Prelaunch, launch, mission, and landing distribution of RF and hardline uplink/downlink information between Space Shuttle Orbiter/cargo elements, tracking antennas, and control centers at JSC, KSC, MSFC, GSFC, ESMC/RCC, and Sunnyvale are presented as functional block diagrams. Typical mismatch problems encountered during spacecraft-to-project control center telemetry transmissions are listed along with new items for future support enhancement.

Multisite Testing of the Discrete Address Beacon System (DABS).

DTIC Science & Technology

1981-07-01

downlink messages from an airborne distributed computer system containing , transponder in addition to performing 36 minicomputers, most of which are...the lockout function. organized into groups (or ensembles) of four computers interfaced to a local Each sensor may provide surveillance and data bus...position and velocity. Depending upon computer subsystem, which monitors the means used for scenario generation, in real time all communication and aircraft

47 CFR 25.134 - Licensing provisions of Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2012 CFR

2012-10-01

... Applications and Licenses Earth Stations § 25.134 Licensing provisions of Very Small Aperture Terminal (VSAT... maximum outbound downlink EIRP density of +10.0 dBW/4 kHz per carrier and earth station antennas with... Order in the Matter of Routine Licensing of Earth Stations in the 6 GHz and 14 GHz Bands Using Antennas...

47 CFR 25.134 - Licensing provisions for Very Small Aperture Terminal (VSAT) and C-band Small Aperture Terminal...

Code of Federal Regulations, 2013 CFR

2013-10-01

... Applications and Licenses Earth Stations § 25.134 Licensing provisions for Very Small Aperture Terminal (VSAT... maximum outbound downlink EIRP density of +10.0 dBW/4 kHz per carrier and earth station antennas with... Order in the Matter of Routine Licensing of Earth Stations in the 6 GHz and 14 GHz Bands Using Antennas...

Mir 22 flight engineer on the Spacehab module

NASA Image and Video Library

1997-01-16

STS081-E-05482 (16 Jan. 1997) --- Perhaps overwhelmed by a giant stock of supplies (out of frame, left), cosmonaut Aleksandr Y. Kaleri, Mir-22 flight engineer, ponders what parcel to transfer next from the Spacehab Double Module (DM) to the Russian Mir Space Station complex. The photograph was recorded with an Electronic Still Camera (ESC) and later was downlinked to flight controllers in Houston, Texas.

Naval Research Reviews. Volume 39, Number 3,

DTIC Science & Technology

1987-01-01

remote sensing, ice and waves, acoustics, and MIZEX East Research Area. biology . Operations benefitted greatly from SAR imagery, downlinked daily. in near...the carried out coordinated programs in oceanography . edd\\ Norwsegian Satellite Telemelr\\ Station under D).A. Horn. studies. biology and meteorology...processes are the principal generators of " ambient noise in the Arctic MIZ. 20 . % Biology Acknowledgements In MIZEX 87, growth rates and the standing

HST Solar Arrays photographed by Electronic Still Camera

NASA Technical Reports Server (NTRS)

1993-01-01

This view, backdropped against the blackness of space shows one of two original Solar Arrays (SA) on the Hubble Space Telescope (HST). The scene was photographed with an Electronic Still Camera (ESC), and downlinked to ground controllers soon afterward. Electronic still photography is a technology which provides the means for a handheld camera to electronically capture and digitize an image with resolution approaching film quality.

Human Flight to Lunar and Beyond - Re-Learning Operations Paradigms

NASA Technical Reports Server (NTRS)

Kenny, Ted; Statman, Joseph

2016-01-01

For the first time since the Apollo era, NASA is planning on sending astronauts on flights beyond Low-Earth Orbit (LEO). The Human Space Flight (HSF) program started with a successful initial flight in Earth orbit, in December 2014. The program will continue with two Exploration Missions (EM) to Lunar orbit: EM-1 will be unmanned and EM-2, carrying astronauts, will follow. NASA established a multi-center team to address the communications, and related navigation, needs. This paper will focus on the lessons learned in the team, planning for the missions' parts that are beyond Earth orbit. Many of these lessons had to be re-learned, as the HSF program after operated for many years in Earth orbit. Fortunately, the experience base from tracking robotic missions in deep space by the Deep Space Network (DSN) and close interaction with the HSF community to understand the unique needs (e.g. 2-way voice) resulted in a ConOps that leverages of both the deep space robotic and the Human LEO experiences. Several examples will be used to highlight the unique operational needs for HSF missions beyond Earth Orbit, including: - Navigation. At LEO, HSF missions can rely on Global Positioning System (GPS) devices for orbit determination. For Lunar-and-beyond HSF missions, techniques such as precision 2-way and 3-way Doppler and ranging, Delta-Difference-of-range, and eventually on-board navigation will be used. - Impact of latency - the delay associated with Round-Trip-Light-Time (RTLT). Imagine trying to have a 2-way discussion (audio or video) with an astronaut, with a 2-3 sec delay inserted (for Lunar distances) or 20 minutes delay (for Mars distances). - Balanced communications link. For robotic missions, there has been a heavy emphasis on the downlink data rates, bringing back science data from the instruments on-board the spacecraft. Uplink data rates were of secondary importance, used to send commands to the spacecraft. The ratio of downlink-to-uplink data rates was often 10:1 or more. For HSF, rates for uplink and downlink, at least for high-quality video, need to be similar.

Field Experiments on Real-Time 1-Gbps High-Speed Packet Transmission in MIMO-OFDM Broadband Packet Radio Access

NASA Astrophysics Data System (ADS)

Taoka, Hidekazu; Higuchi, Kenichi; Sawahashi, Mamoru

This paper presents experimental results in real propagation channel environments of real-time 1-Gbps packet transmission using antenna-dependent adaptive modulation and channel coding (AMC) with 4-by-4 MIMO multiplexing in the downlink Orthogonal Frequency Division Multiplexing (OFDM) radio access. In the experiment, Maximum Likelihood Detection employing QR decomposition and the M-algorithm (QRM-MLD) with adaptive selection of the surviving symbol replica candidates (ASESS) is employed to achieve such a high data rate at a lower received signal-to-interference plus background noise power ratio (SINR). The field experiments, which are conducted at the average moving speed of 30km/h, show that real-time packet transmission of greater than 1Gbps in a 100-MHz channel bandwidth (i.e., 10bits/second/Hz) is achieved at the average received SINR of approximately 13.5dB using 16QAM modulation and turbo coding with the coding rate of 8/9. Furthermore, we show that the measured throughput of greater than 1Gbps is achieved at the probability of approximately 98% in a measurement course, where the maximum distance from the cell site was approximately 300m with the respective transmitter and receiver antenna separation of 1.5m and 40cm with the total transmission power of 10W. The results also clarify that the minimum required receiver antenna spacing is approximately 10cm (1.5 carrier wave length) to suppress the loss in the required received SINR at 1-Gbps throughput to within 1dB compared to that assuming the fading correlation between antennas of zero both under non-line-of-sight (NLOS) and line-of-sight (LOS) conditions.

Analyzing mobile WiMAX base station deployment under different frequency planning strategies

NASA Astrophysics Data System (ADS)

Salman, M. K.; Ahmad, R. B.; Ali, Ziad G.; Aldhaibani, Jaafar A.; Fayadh, Rashid A.

2015-05-01

The frequency spectrum is a precious resource and scarce in the communication markets. Therefore, different techniques are adopted to utilize the available spectrum in deploying WiMAX base stations (BS) in cellular networks. In this paper several types of frequency planning techniques are illustrated, and a comprehensive comparative study between conventional frequency reuse of 1 (FR of 1) and fractional frequency reuse (FFR) is presented. These techniques are widely used in network deployment, because they employ universal frequency (using all the available bandwidth) in their base station installation/configuration within network system. This paper presents a network model of 19 base stations in order to be employed in the comparison of the aforesaid frequency planning techniques. Users are randomly distributed within base stations, users' resource mapping and their burst profile selection are based on the measured signal to interference plus-noise ratio (SINR). Simulation results reveal that the FFR has advantages over the conventional FR of 1 in various metrics. 98 % of downlink resources (slots) are exploited when FFR is applied, whilst it is 81 % at FR of 1. Data rate of FFR has been increased to 10.6 Mbps, while it is 7.98 Mbps at FR of 1. The spectral efficiency is better enhanced (1.072 bps/Hz) at FR of 1 than FFR (0.808 bps/Hz), since FR of 1 exploits all the Bandwidth. The subcarrier efficiency shows how many data bits that can be carried by subcarriers under different frequency planning techniques, the system can carry more data bits under FFR (2.40 bit/subcarrier) than FR of 1 (1.998 bit/subcarrier). This study confirms that FFR can perform better than conventional frequency planning (FR of 1) which made it a strong candidate for WiMAX BS deployment in cellular networks.

NASA Langley Teacher Resource Center at the Virginia Air and Space Center

NASA Technical Reports Server (NTRS)

Maher, Kim L.

1999-01-01

Nation's education goals through expanding and enhancing the scientific an technological competence of students and educators. To help disseminate NASA instructional materials and educational information, NASA's Education Division has established the Educator Resource Center Network. Through this network (ERCN), educators are provided the opportunity to receive free instructional information, materials, consultation, and training workshops on NASA educational products. The Office of Education at NASA Langley Research Center offers an extension of its Precollege Education program by supporting the NASA LARC Educator Resource Center at the Virginia Air & Space Center, the official visitor center for NASA LARC. This facility is the principal distribution point for educators in the five state service region that includes Virginia, West Virginia, Kentucky, North Carolina and South Carolina. The primary goal, to provide expertise and facilities to help educators access and utilize science, mathematics, and technology instructional products aligned with national standards and appropriate state frameworks and based on NASA's unique mission and results, has been accomplished. This ERC had 15,200 contacts and disseminated over 190,000 instructional items during the period of performance. In addition the manager attended 35 conferences, workshops, and educational meetings as an GR, presenter, or participant. The objective to demonstrate and facilitate the use of educational technologies has been accomplished through the following: The ERC's web page has been developed as a cyber-gateway to a multitude of NASA and other educational resources as well as to Our own database of current resource materials. NASA CORE CD-ROM technology is regularly demonstrated and promoted using the center's computers. NASA TV is available, demonstrated to educators, and used to facilitate the downlinking of NASA educational programming.

Initial Satellite Formation Flight Results from the Magnetospheric Multiscale Mission

NASA Technical Reports Server (NTRS)

Williams, Trevor; Ottenstein, Neil; Palmer, Eric; Farahmand, Mitra

2016-01-01

This paper will describe the results that have been obtained to date concerning MMS formation flying. The MMS spacecraft spin at a rate of 3.1 RPM, with spin axis roughly aligned with Ecliptic North. Several booms are used to deploy instruments: two 5 m magnetometer booms in the spin plane, two rigid booms of length 12.5 m along the positive and negative spin axes, and four flexible wire booms of length 60 m in the spin plane. Minimizing flexible motion of the wire booms requires that reorientation of the spacecraft spin axis be kept to a minimum: this is limited to attitude maneuvers to counteract the effects of gravity-gradient and apparent solar motion. Orbital maneuvers must therefore be carried out in essentially the nominal science attitude. These burns make use of a set of monopropellant hydrazine thrusters: two (of thrust 4.5 N) along the spin axis in each direction, and eight (of thrust 18 N) in the spin plane; the latter are pulsed at the spin rate to produce a net delta-v. An on-board accelerometer-based controller is used to accurately generate a commanded delta-v. Navigation makes use of a weak-signal GPS-based system: this allows signals to be received even when MMS is flying above the GPS orbits, producing a highly accurate determination of the four MMS orbits. This data is downlinked to the MMS Mission Operations Center (MOC) and used by the MOC Flight Dynamics Operations Area (FDOA) for maneuver design. These commands are then uplinked to the spacecraft and executed autonomously using the controller, with the ground monitoring the burns in real time.

Integration of micro-/nano-/quantum-scale photonic devices: scientific and technological considerations

NASA Astrophysics Data System (ADS)

Lee, El-Hang; Lee, Seung-Gol; O, Beom Hoan; Park, Se Geun

2004-08-01

Scientific and technological issues and considerations regarding the integration of miniaturized microphotonic devices, circuits and systems in micron, submicron, and quantum scale, are presented. First, we examine the issues regarding the miniaturization of photonic devices including the size effect, proximity effect, energy confinement effect, microcavity effect, optical and quantum interference effect, high field effect, nonlinear effect, noise effect, quantum optical effect, and chaotic effect. Secondly, we examine the issues regarding the interconnection including the optical alignment, minimizing the interconnection losses, and maintaining optical modes. Thirdly, we address the issues regarding the two-dimensional or three-dimensional integration either in a hybrid format or in a monolithic format between active devices and passive devices of varying functions. We find that the concept of optical printed circuit board (O-PCB) that we propose is highly attractive as a platform for micro/nano/quantum-scale photonic integration. We examine the technological issues to be addressed in the process of fabrication, characterization, and packaging for actual implementation of the miniaturization, interconnection and integration. Devices that we have used for our study include: mode conversion schemes, micro-ring and micro-racetrack resonator devices, multimode interference devices, lasers, vertical cavity surface emitting microlasers, and their arrays. Future prospects are also discussed.

Interference figures of polarimetric interferometry analysis of the human corneal stroma

PubMed Central

Mastropasqua, Rodolfo; Nubile, Mario; Salgari, Niccolò; Lanzini, Manuela; Calienno, Roberta; Mattei, Peter A.; Sborgia, Alessandra; Agnifili, Luca

2017-01-01

A rotating polarimetric 90°-cross linear-filter interferometry system was used to detect the morphological characteristics and features of interference patterns produced in in-vivo corneal stroma in healthy human corneas of 23 subjects. The characteristic corneal isogyres presenting with an evident cross-shaped pattern, grossly aligned with the fixation axis, were observed in all patients with centers within the pupillary dark area, impeding the exact determination of the center point. During the rotational scan in 78.3% of the eyes the cross-shaped pattern of the isogyre gradually separated to form two distinct hyperbolic arcs in opposite quadrants, reaching their maximal separation at 45 degrees with respect to angle of cross-shaped pattern formation. The corneal cross and hyperbolic-pattern repeated every 90° throughout the 360° rotational scan. While the interpretation of the isogyres presents particular difficulties, two summary parameters can be extracted for each cornea: the presence/orientation of a single or two dark areas in post-processed images and isochromes. However, the development of dedicated software for semi-quantitative analysis of these parameters and enantiomorphism may become available in the near future. The possible application of polarimetric interferometry in the field of both corneal pathologies and corneal surgery may be of great interest for clinical purposes. PMID:28570631

Interference figures of polarimetric interferometry analysis of the human corneal stroma.

PubMed

Mastropasqua, Rodolfo; Nubile, Mario; Salgari, Niccolò; Lanzini, Manuela; Calienno, Roberta; Mattei, Peter A; Sborgia, Alessandra; Agnifili, Luca

2017-01-01

A rotating polarimetric 90°-cross linear-filter interferometry system was used to detect the morphological characteristics and features of interference patterns produced in in-vivo corneal stroma in healthy human corneas of 23 subjects. The characteristic corneal isogyres presenting with an evident cross-shaped pattern, grossly aligned with the fixation axis, were observed in all patients with centers within the pupillary dark area, impeding the exact determination of the center point. During the rotational scan in 78.3% of the eyes the cross-shaped pattern of the isogyre gradually separated to form two distinct hyperbolic arcs in opposite quadrants, reaching their maximal separation at 45 degrees with respect to angle of cross-shaped pattern formation. The corneal cross and hyperbolic-pattern repeated every 90° throughout the 360° rotational scan. While the interpretation of the isogyres presents particular difficulties, two summary parameters can be extracted for each cornea: the presence/orientation of a single or two dark areas in post-processed images and isochromes. However, the development of dedicated software for semi-quantitative analysis of these parameters and enantiomorphism may become available in the near future. The possible application of polarimetric interferometry in the field of both corneal pathologies and corneal surgery may be of great interest for clinical purposes.

Electrical potential induced switchable wettability of super-aligned carbon nanotube films

NASA Astrophysics Data System (ADS)

Zhang, Guang; Duan, Zheng; Wang, Qinggong; Li, Long; Yao, Wei; Liu, Changhong

2018-01-01

Controlling of the wettability of micro-nano scale surfaces not only plays important roles in basic science but also presents some significant applications in interference shielding materials, microfluidics and phase-change heat transfer enhancement, etc. Here, the superhydrophobic super-aligned carbon nanotube (SACNT) films are firstly obtained by the chemical vapor deposition method and the annealing process. Then their wettabilities are in-situ switched by the electrowetting strategy. Specifically, the fascinating transformation of superhydrophobicity to the superhydrophilicity is achieved by exerting external DC voltages across the CNT-liquid interfaces, and the transitions of Cassie-to-Wenzel states are observed on the multilayer SACNT films. In addition, the electrowetting induced salt absorption of the porous SACNT is also reported here. Finally, the threshold voltages of the electrowetting behaviors for different liquids on the SACNT films and unit capacitances across the CNT-liquid interfaces are obtained, which reveal that the SACNT films have much more outstanding electrowetting properties than the previously reported works. Our approach reported here demonstrates that the wettability of SACNT films could be simply, effectively and in-situ controlled by the electrowetting method, which will have many profound implications in numerous applications such as phase-change heat transfer enhancement, optical lens with variable focal length and microfluidics, etc.

A Fiber-Optic Coupled Telescope for Water Vapor DIAL Receivers

NASA Technical Reports Server (NTRS)

DeYoung, Russell J.; Lonn, Frederick

1998-01-01

A fiber-optic coupled telescope of low complexity was constructed and tested. The major loss mechanisms of the optical system have been characterized. Light collected by the receiver mirror is focused onto an optical fiber, and the output of the fiber is filtered by an interference filter and then focused onto an APD detector. This system was used in lidar field measurements with a 532-nm Nd:YAG laser beam. The results were encouraging. A numerical model used for calculation of the expected return signal agreed with the lidar return signal obtained. The assembled system was easy to align and operate and weighed about 8 kg for a 30 cm (12") mirror system. This weight is low enough to allow mounting of the fiber-optic telescope receiver system in a UAV. Furthermore, the good agreement between the numerical lidar model and the performance of the actual receiver system, suggests that this model may be used for estimation of the performance of this and other lidar systems in the future. Such telescopes are relatively easy to construct and align. The fiber optic cable allows easy placement of the optical detector in any position. These telescope systems should find widespread use in aircraft and space home DIAL water vapor receiver systems.

From reading numbers to seeing ratios: a benefit of icons for risk comprehension.

PubMed

Tubau, Elisabet; Rodríguez-Ferreiro, Javier; Barberia, Itxaso; Colomé, Àngels

2018-06-21

Promoting a better understanding of statistical data is becoming increasingly important for improving risk comprehension and decision-making. In this regard, previous studies on Bayesian problem solving have shown that iconic representations help infer frequencies in sets and subsets. Nevertheless, the mechanisms by which icons enhance performance remain unclear. Here, we tested the hypothesis that the benefit offered by icon arrays lies in a better alignment between presented and requested relationships, which should facilitate the comprehension of the requested ratio beyond the represented quantities. To this end, we analyzed individual risk estimates based on data presented either in standard verbal presentations (percentages and natural frequency formats) or as icon arrays. Compared to the other formats, icons led to estimates that were more accurate, and importantly, promoted the use of equivalent expressions for the requested probability. Furthermore, whereas the accuracy of the estimates based on verbal formats depended on their alignment with the text, all the estimates based on icons were equally accurate. Therefore, these results support the proposal that icons enhance the comprehension of the ratio and its mapping onto the requested probability and point to relational misalignment as potential interference for text-based Bayesian reasoning. The present findings also argue against an intrinsic difficulty with understanding single-event probabilities.

Guidance system operations plan for manned cm earth orbital and lunar missions using program Colossus 3. Section 2: Data links

NASA Technical Reports Server (NTRS)

Hamilton, M. H.

1971-01-01

The data links for use with the guidance system operations plan for manned command module earth orbital and lunar missions using program Colossus 3 are presented. The subjects discussed are: (1) digital uplink to CMC, (2) command module contiguous block update, (3) CMC retrofire external data update, (4) CMC digital downlink, and (5) CMC entry update.

A depolarization and attenuation experiment using the COMSTAR and CTS satellites

NASA Technical Reports Server (NTRS)

Bostian, C. W.; Manus, E. A.; Marshall, R. E.; Overstreet, W. P.; Persinger, R. R.; Powell, J. D.; Santago, P.; Stutzman, W. L.; Wiley, P. H.

1978-01-01

Monthly statistical data are presented on ground rainfall rate and attenuation of satellite downlinks at 11.7 GHz, 19.04 GHz, and 28.56 GHz and on cross-polarization isolation at 11.7 GHz. Regression equations for relating isolation to attenuation, attenuation to rain rate, and attenuation at one frequency to attenuation at another frequency are also included. Longer-term statistics are also presented and discussed.

A depolarization and attenuation experiment using the COMSTAR and CTS satellites

NASA Technical Reports Server (NTRS)

Bostian, C. W.; Babula, S. M.; Dent, J. R.; Dombroski, R. E.; Lane, S. O.; Manus, E. A.; Marshall, R. E.; Meadows, D. N.; Stutzman, W. L.; Wiley, P. H.

1979-01-01

Monthly and annual percent-of-time data on ground rain fall rate and attenuation on satellite downlinks at 11.7 GHz, 19.04 GHz, and 28.56 GHz is presented. Equal probability values of attenuation and rain rate are compared for monthly, quarterly, half-year periods and for the entire year. Regression equations relating cross polarization isolation to the logarithm of attenuation are also presented.

An Advanced Commanding and Telemetry System

NASA Astrophysics Data System (ADS)

Hill, Maxwell G. G.

The Loral Instrumentation System 500 configured as an Advanced Commanding and Telemetry System (ACTS) supports the acquisition of multiple telemetry downlink streams, and simultaneously supports multiple uplink command streams for today's satellite vehicles. By using industry and federal standards, the system is able to support, without relying on a host computer, a true distributed dataflow architecture that is complemented by state-of-the-art RISC-based workstations and file servers.

The TechSat-21 Autonomous Sciencecraft Experiment

DTIC Science & Technology

2003-06-01

indicating lava flow on Kilauea Volcano , Big Island, Hawaii . The changes in the highlighted areas of the image are indicative of lava flow that occurred in...recognizable features of interest such as craters and volcanoes . Such onboard science will enable retargeting and search, e.g., shifting the radar aim- point...phenomena at fine time-scales without overwhelming onboard caching or downlink capacities. Future examples can include: eruption of volcanoes on Io

An Introduction to Military Satellite Communications.

DTIC Science & Technology

1987-04-01

in the range 220 - 400 MHz, and hence shared with a variety of terrestrial systems (including TV). Helix antennas are commonly employed, both on the...downlink). A common helix antenna is used for both transmit and receive, with a multiplexer unit separating the two. This antenna is relatively large...into account; these increase sharply as the TWT is driven into saturation, and the controller will determine any required back-off (and will perhaps

Real-Time Optimization in Complex Stochastic Environment

DTIC Science & Technology

2015-06-24

simpler ones, thus addressing scalability and the limited resources of networked wireless devices. This, however, comes at the expense of increased...Maximization of Wireless Sensor Networks with Non-ideal Batteries”, IEEE Trans. on Control of Network Systems, Vol. 1, 1, pp. 86-98, 2014. [27...C.G., “Optimal Energy-Efficient Downlink Transmission Scheduling for Real-Time Wireless Networks ”, subm. to IEEE Trans. on Control of Network Systems

Earth Observations taken by the Expedition 31 Crew

NASA Image and Video Library

2012-06-02

ISS031-E-83747 (2 June 2012) --- Downlinked from the International Space Station this still image -– part of a series from a mounted, automated, twilight session -- when viewed in sequence shows the flame ring associated with wild fires in the Southwest move from bottom to top-center framed at a distance by the bright urban areas of Tucson, Phoenix, El Paso-Las Cruces, and finally Albuquerque (mostly under cloud).

Earth Observations taken by the Expedition 31 Crew

NASA Image and Video Library

2012-06-02

ISS031-E-83789 (2 June 2012) --- Downlinked from the International Space Station this still image – part of a series from a mounted, automated, twilight session -- when viewed in sequence shows the flame ring associated with wild fires in the Southwest move from bottom to top-center framed at a distance by the bright urban areas of Tucson, Phoenix, El Paso-Las Cruces, and finally Albuquerque (mostly under cloud).

Integrated Doppler Correction to TWSTFT Using Round-Trip Measurement

DTIC Science & Technology

2010-11-01

42 nd Annual Precise Time and Time Interval (PTTI) Meeting 251 INTEGRATED DOPPLER CORRECTION TO TWSTFT USING ROUND-TRIP MEASUREMENT Yi...Frequency Transfer ( TWSTFT ) data. It is necessary to correct the diurnal variation for comparing the time-scale difference. We focus on the up-/downlink...delay difference caused by satellite motion. In this paper, we propose to correct the TWSTFT data by using round-trip delay measurement. There are

Acapulco, Mexico taken with electronic still camera

NASA Image and Video Library

1995-10-29

STS073-E-5275 (3 Nov. 1995) --- Resort City of Acapulco appears in this north-looking view, photographed from the Earth-orbiting space shuttle Columbia with the Electronic Still Camera (ESC). The airport lies on a narrow neck of land between the sea and a large coastal lagoon. This mission marks the first time NASA has released in mid-flight electronically-downlinked color images that feature geographic subject matter.