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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A demonstration of unified TDRS/GPS tracking and orbit determination

We describe results from an experiment in which TDRS and GPS satellites were tracked simultaneously from a small (3 station) ground network in the western United States. We refer to this technique as 'GPS-like tracking' (GLT) since the user satellite - in this case TDRS - is essentially treated as a participant in the GPS constellation. In the experiment, the TDRS K(sub space-to-ground link (SGL) was tracked together with GPS L-band signals in enhanced geodetic-quality GPS receivers (TurboRogue). The enhanced receivers simultaneously measured and recorded both the TDRS SGL and the GPS carrier phases with sub-mm precision, enabling subsequent precise TDRS orbit determination with differential GPS techniques. A small number of calibrated ranging points from routine operations at the TDRS ground station (White Sands, NM) were used to supplement the GLT measurements in order to improve determination of the TDRS longitude. Various tests performed on TDRS ephemerides derived from data collected during this demonstration - including comparisons with the operational precise orbit generated by NASA Goddard Space Flight Center - provide evidence that the TDRS orbits have been determined to better than 25 m with the GLT technique.

Haines, B.↗
NASA NTRS2014

Tethered Vehicle Control and Tracking System

A kite system includes a kite and a ground station. The ground station includes a sensor that can be utilized to determine an angular position and velocity of the kite relative to the ground station. A controller utilizes a fuzzy logic control system to autonomously fly the kite. The system may include a ground station having powered winding units that generate power as the lines to the kite are unreeled. The control system may be configured to fly the kite in a crosswind trajectory to increase line tension for power generation. The sensors for determining the position of the kite are preferably ground-based.

North, David D.↗
NASA NTRS2017

Tethered Vehicle Control and Tracking System

A kite system includes a kite and a ground station. The ground station includes a sensor that can be utilized to determine an angular position and velocity of the kite relative to the ground station. A controller utilizes a fuzzy logic control system to autonomously fly the kite. The system may include a ground station having powered winding units that generate power as the lines to the kite are unreeled. The control system may be configured to fly the kite in a crosswind trajectory to increase line tension for power generation. The sensors for determining the position of the kite are preferably ground-based.

North, David D.↗
NASA NTRS1993

Ground data system for Space Flyer Unit (SFU)

The Space Flyer Unit (SFU) is an unmanned, multi-purpose, retrievable and reusable space platform. The first mission of SFU (SFU-1) will be launched by NASDA's H-2 launch vehicle in early 1995 and retrieved by NASA's Space Shuttle after several months in orbit. Two Japanese ground stations, several ground stations belonging to NASA, and a ground station in Chile will be used for tracking of SFU-1. The control center of SFU-1 is the Sagamihara Operations Center (SOC) of ISAS located in Sagamihara, Japan. This paper describes the tracking and data acquisition network for SFU-1, the configuration and design policy of the SFU operations control system, and data processing schemes used for mission operations of SFU.

Yamada, Takahiro↗
NASA NTRS1991

Characteristics of a future aeronautical satellite communications system

A possible operational system scenario for providing satellite communications services to the future aviation community was analyzed. The system concept relies on a Ka-band (20/30 GHz) satellite that utilizes multibeam antenna (MBA) technology. The aircraft terminal uses an extremely small aperture antenna as a result of using this higher spectrum at Ka-band. The satellite functions as a relay between the aircraft and the ground stations. The ground stations function as interfaces to the existing terrestrial networks such as the Public Service Telephone Network (PSTN). Various system tradeoffs are first examined to ensure optimized system parameters. High level performance specifications and design approaches are generated for the space, ground, and aeronautical elements in the system. Both technical and economical issues affecting the feasibility of the studied concept are addressed with the 1995 timeframe in mind.

Sohn, Philip Y.↗
NASA NTRS1991

Characteristics of a future aeronautical satellite communications system

A possible operational system scenario for providing satellite communications services to the future aviation community was analyzed. The system concept relies on a Ka-band (20/30 GHz) satellite that utilizes Multibeam Antenna (MBA) technology. The aircraft terminal uses an extremely small aperture antenna as a result of using this higher spectrum at Ka-band. The satellite functions as a relay between the aircraft and the ground stations. The ground stations function as interfaces to the existing terrestrial networks such as the Public Service Telephone Network (PSTN). Various system tradeoffs are first examined to ensure optimized system parameters. High level performance specifications and design approaches are generated for the space, ground, and aeronautical elements in the system. Both technical and economical issues affecting the feasibility of the studied concept are addressed with the 1995 timeframe in mind.

Sohn, Philip Y.↗
NASA NTRS2005

Ground System for Solar Dynamics Observatory (SDO) Mission

NASA s Goddard Space Flight Center (GSFC) has recently completed its Critical Design Review (CDR) of a new dual Ka and S-band ground system for the Solar Dynamics Observatory (SDO) Mission. SDO, the flagship mission under the new Living with a Star Program Office, is one of GSFC s most recent large-scale in-house missions. The observatory is scheduled for launch in August 2008 from the Kennedy Space Center aboard an Atlas-5 expendable launch vehicle. Unique to this mission is an extremely challenging science data capture requirement. The mission is required to capture 99.99% of available science over 95% of all observation opportunities. Due to the continuous, high volume (150 Mbps) science data rate, no on-board storage of science data will be implemented on this mission. With the observatory placed in a geo-synchronous orbit at 36,000 kilometers within view of dedicated ground stations, the ground system will in effect implement a "real-time" science data pipeline with appropriate data accounting, data storage, data distribution, data recovery, and automated system failure detection and correction to keep the science data flowing continuously to three separate Science Operations Centers (SOCs). Data storage rates of approx. 45 Tera-bytes per month are expected. The Mission Operations Center (MOC) will be based at GSFC and is designed to be highly automated. Three SOCs will share in the observatory operations, each operating their own instrument. Remote operations of a multi-antenna ground station in White Sands, New Mexico from the MOC is part of the design baseline.

Tann, Hun K.↗
NASA NTRS2007

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

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

Welch, Bryan W.↗
NASA NTRSDate not supplied

NASA’s Laser Communications Relay Demonstration (LCRD) Experiment Program: Characterization And Initial Operations

The National Aeronautics and Space Administration’s (NASA) Laser Communications Relay Demonstration (LCRD) completed the first 18 months of its Experiment Program in December 2023. The LCRD geosynchronous payload includes two laser communications terminals interconnected via an onboard electronic switch. The payload can relay information between any two of a set of three ground stations. Two optical ground stations are located in California and Hawaii, and an RF ground station is located in New Mexico. Experiments to date have included demonstration of optimetrics, demonstrations of Delay/Disruption Tolerant Networking (DTN), and measurements of the effects of the atmosphere (turbulence, weather) on the performance and availability of lasercom (pointing, tracking, communications, and adaptive optics). Furthermore, future operational scenarios including robotic and exploration missions with various network service configurations have been emulated. This paper provides an overview and highlights of the first 18 months of LCRD experiments, and a preview of the upcoming experiments, including relaying data to and from the Integrated LCRD Low-Earth Orbit (LEO) User Modem and Amplifier Terminal (ILLUMA-T) on the International Space Station. LCRD is a joint project involving NASA Goddard Space Flight Center (GSFC), the California Institute of Technology Jet Propulsion Laboratory (JPL), and Massachusetts Institute of Technology Lincoln Laboratory (MIT LL).

David J. Israel↗
NASA NTRS2017

Lunar and Lagrangian Point L1 L2 CubeSat Communication and Navigation Considerations

CubeSats have grown in sophistication to the point that relatively low-cost mission solutions could be undertaken for planetary exploration. There are unique considerations for Lunar and L1L2 CubeSat communication and navigation compared with low earth orbit CubeSats. This paper explores those considerations as they relate to the MoreheadGSFC Lunar IceCube Mission. The Lunar IceCube is a CubeSat mission led by Morehead State University with participation from NASA Goddard Space Flight Center, JPL, the Busek Company and Vermont Tech. It will search for surface water ice and other resources from a high inclination lunar orbit. Lunar IceCube is one of a select group of CubeSats designed to explore beyond low-earth orbit that will fly on NASAs Space Launch System (SLS) as secondary payloads for Exploration Mission (EM) 1. Lunar IceCube and the EM-1 CubeSats will lay the groundwork for future lunar and L1L2 CubeSat missions. This paper discusses communication and navigation needs for the Lunar IceCube mission and navigation and radiation tolerance requirements related to lunar and L1L2 orbits. Potential CubeSat radio and antennas for such missions are investigated and compared. Ground station coverage, link analysis, and ground station solutions are also discussed. There are currently modifications in process for the Morehead ground station. Further enhancement of the Morehead ground station and the NASA Near Earth Network (NEN) are being examined. This paper describes how the NEN may support Lunar and L1L2 CubeSats without any enhancements and potential expansion of NEN to better support such missions in the future. The potential NEN enhancements include upgrading current NEN Cortex receiver with Forward Error Correction (FEC) Turbo Code, providing X-band Uplink capability, and adding ranging options. The benefits of ground station enhancements for CubeSats flown on NASA Exploration Missions (EM) are presented. The paper also discusses other initiatives that the NEN is studying to better support the CubeSat community, including streamlining the compatibility test, planning and scheduling associated with CubeSat missions.

CubeSat↗
NASA NTRS1996

Gigabit Satellite Network for NASA's Advanced Communication Technology Satellite (ACTS)

The advanced communication technology satellite (ACTS) gigabit satellite network provides long-haul point-to-point and point-to-multipoint full-duplex SONET services over NASA's ACTS. at rates up to 622 Mbit/s (SONET OC-12), with signal quality comparable to that obtained with terrestrial fiber networks. Data multiplexing over the satellite is accomplished using time-division multiple access (TDMA) techniques coordinated with the switching and beam hopping facilities provided by ACTS. Transmissions through the satellite are protected with Reed-Solomon encoding. providing virtually error-free transmission under most weather conditions. Unique to the system are a TDMA frame structure and satellite synchronization mechanism that allow: (a) very efficient utilization of the satellite capacity: (b) over-the-satellite dosed-loop synchronization of the network in configurations with up to 64 ground stations: and (c) ground station initial acquisition without collisions with existing signalling or data traffic. The user interfaces are compatible with SONET standards, performing the function of conventional SONET multiplexers and. as such. can be: readily integrated with standard SONET fiber-based terrestrial networks. Management of the network is based upon the simple network management protocol (SNMP). and includes an over-the-satellite signalling network and backup terrestrial internet (IP-based) connectivity. A description of the ground stations is also included.

Hoder, Douglas↗
NASA NTRS2017

Lunar and Lagrangian Point L1 L2 CubeSat Communication and Navigation Considerations

CubeSats have grown in sophistication to the point that relatively low-cost mission solutions could be undertaken for planetary exploration. There are unique considerations for lunar and L1/L2 CubeSat communication and navigation compared with low earth orbit CubeSats. This paper explores those considerations as they relate to the Lunar IceCube Mission. The Lunar IceCube is a CubeSat mission led by Morehead State University with participation from NASA Goddard Space Flight Center, Jet Propulsion Laboratory, the Busek Company and Vermont Tech. It will search for surface water ice and other resources from a high inclination lunar orbit. Lunar IceCube is one of a select group of CubeSats designed to explore beyond low-earth orbit that will fly on NASA’s Space Launch System (SLS) as secondary payloads for Exploration Mission (EM) 1. Lunar IceCube and the EM-1 CubeSats will lay the groundwork for future lunar and L1/L2 CubeSat missions. This paper discusses communication and navigation needs for the Lunar IceCube mission and navigation and radiation tolerance requirements related to lunar and L1/L2 orbits. Potential CubeSat radios and antennas for such missions are investigated and compared. Ground station coverage, link analysis, and ground station solutions are also discussed. This paper will describe modifications in process for the Morehead ground station, as well as further enhancements of the Morehead ground station and NASA Near Earth Network (NEN) that are being considered. The potential NEN enhancements include upgrading current NEN Cortex receiver with Forward Error Correction (FEC) Turbo Code, providing X-band uplink capability, and adding ranging options. The benefits of ground station enhancements for CubeSats flown on NASA Exploration Missions (EM) are presented. This paper also describes how the NEN may support lunar and L1/L2 CubeSats without any enhancements. In addition, NEN is studying other initiatives to better support the CubeSat community, including streamlining the compatibility testing, planning and scheduling associated with CubeSat missions. Because of the lower cost, opportunity for simultaneous multipoint observations, it is inevitable that CubeSats will continue to increase in popularity for not only LEO missions, but for lunar and L1/L2 missions as well. The challenges for lunar and L1/L2 missions for communication and navigation are much greater than for LEO missions, but are not insurmountable. Advancements in flight hardware and ground infrastructure will ease the burden.

CubeSat↗
NASA NTRS2020

Case Study of Using Flocad to Model a Ground Test Station Ln2 Heat Exchanger

This paper presents a case study of using FLOCAD to model the heat transfer and boiling flow behavior of a Liquid Nitrogen (LN2) ground station equipment heat exchanger. The unique aspect of this work is that is one of very few studies documenting the use of FLOCAD in the spacecraft thermal control community. The results of the simulations described herein were used to guide and plan the execution of thermal vacuum testing spacecraft hardware using a ground test heat exchanger such as the one modeled herein. The paper will review the theory of two-phase boiling flow and correlations used by SINDA/FLUINT as well as the terminology and nomenclature used within Thermal Desktop / FLOCAD regarding two-phase boiling flow heat transfer modeling and simulation. Results for using the ground station heat exchanger as a heat sink in a thermal vacuum test set up are shown in order to demonstrate the set-up and execution of a typical FLOCAD model. Results indicate that properly modeling of the two-phase behavior is critical in order to ascertain the time constant associated with the heat exchanger, as well as understanding the temperature distribution across the test equipment and prediction of required LN2 flowrates to be used during testing. The paper is meant to augment the FLOCAD user’s manual and serve as a tutorial for thermal engineers and analysts wishing to learn and apply FLOCAD to industrial problems.

Anderson, Kevin R.↗
NASA NTRS1978

The effects of quantization on signal processing

Typically an analog signal from a space system is sampled, quantized by Analog-to-Digital (A/D) conversion, merged into a bit stream, communicated to a ground station, received by the ground station, and processed by the ground station to extract useful information for dissemination to the users. The cost of each of these steps is reduced as the number of quantization steps is reduced in the A/D converter. The number of quantization steps should be as small as possible without losing the required information content. This report deals specifically with the accuracy of averages as a function of the number of quantized samples used to compute the averages with the noise on the analog signal as a parameter. For example, the success of the Visible Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS) Demonstration depends upon temporally averaging multiple samples in an effort to reduce noise to a sufficiently low level such that temperature profile sounding is made possible. A tutorial description of this process is presented.

Montgomery, H. E.↗
NASA NTRS2018

Simulation and Analysis of Opportunistic MSPA for Multiple Cubesat Deployments

We describe a software approach for simultaneous demodulation and decoding of multiple frequency- multiplexed spacecraft across multiple ground stations. The approach involves the use of a single ground antenna with wide enough aperture to receive multiple angularly adjacent spacecraft simultaneously. This technique uses a wide-band RF signal digitizer coupled with easily and cheaply duplicated software-receiver modules to independently process the frequency-channelized downlink signals from the spacecraft. This approach relaxes the need for realizable modems at each antenna, for example in the Deep-SpaceNetwork (DSN), and can also function as a delayed data retrieval method for cubesat missions with routine science data return. Thus, we hope that this solution can enable more efficient utilization of DSN assets. We concentrate on a simulation similar to the proposed Exploration Mission 1 (EM-1) mission from a geometric perspective. To that end, the simulated scenario involves ten secondary cubesats deployed and tracked for a span of four days (the modeled motion over the first four days of the mission does not include any Trajectory Correction Maneuvers (TCMs) that may be necessary as the cubesats approach the moon). Transmissions from the cubesats may be received through a combination of DSN ground sites based on visibility. The cubesats are assumed to utilize typical cubesat transmit powers and a waveform similar to that of the Iris radio. One cubesat is chosen as the “target” and is considered tracked by all ground-stations throughout the simulation (i.e., it is consistently at the center of the main lobe of each ground station antenna when the ground station is in view of the cubesat in terms of elevation angle). The simulation effort involves synthesizing a wideband signal that includes the ten cubesats across a large bandwidth due to each cubesat having its own center-frequency in X-band, near 8.4 GHz. Each signal is characterized by its own Doppler-frequency shift and free-space path-loss computed through the underlying geometry of the simulation as well as the cubesat transmit power. Finally, each cubesat signal experiences a unique antenna gain at each ground station due to the underlying antenna pattern and spacecraft-ground station geometry. We establish two interesting findings: First, the link-budget for the EM-1-like scenario is almost completely limited by the angle between the center of the antenna main beam and the cubesat, which means that the signal-to-noise ratio is wholly adequate for demodulation and decoding at the simulated bitrates unless the cubesat exits the main beam. Secondly, and fortunately due to the use of a software radio architecture, we show that it is possible to successfully receive signals from most cubesats for the entire 4-day simulation. Due to the signal-to-noise ratio being sufficient for demodulation even after the side-lobe’s 17dB reduction in SNR, the software radio can still demodulate such cubesats as long as the radio is capable of re-establishing carrier lock as the cubesats leave the main beam and enter the side-lobe. Considering that the target application utilizes offline processing, a loss of lock can be detected and lock can be re-established by iterating over the data. Extensive simulations demonstrate these results.

Abraham, Douglas S.↗
NASA NTRS2000

ACTS Ka-Band Earth Stations: Technology, Performance, and Lessons Learned

The Advanced Communications Technology Satellite (ACTS) Project invested heavily in prototype Ka-band satellite ground terminals to conduct an experiments program with the ACTS satellite. The ACTS experiment's program proposed to validate Ka-band satellite and ground station technology. demonstrate future telecommunication services. demonstrate commercial viability and market acceptability of these new services, evaluate system networking and processing technology, and characterize Ka-band propagation effects, including development of techniques to mitigate signal fading. This paper will present a summary of the fixed ground terminals developed by the NASA Glenn Research Center and its industry partners, emphasizing the technology and performance of the terminals (Part 1) and the lessons learned throughout their six year operation including the inclined orbit phase of operations (Full Report). An overview of the Ka-band technology and components developed for the ACTS ground stations is presented. Next. the performance of the ground station technology and its evolution during the ACTS campaign are discussed to illustrate the technical tradeoffs made during the program and highlight technical advances by industry to support the ACTS experiments program and terminal operations. Finally. lessons learned during development and operation of the user terminals are discussed for consideration of commercial adoption into future Ka-band systems. The fixed ground stations used for experiments by government, academic, and commercial entities used reflector based offset-fed antenna systems ranging in size from 0.35m to 3.4m antenna diameter. Gateway earth stations included two systems, referred to as the NASA Ground Station (NGS) and the Link Evaluation Terminal (LET). The NGS provides tracking, telemetry, and control (TT&C) and Time Division Multiple Access (TDMA) network control functions. The LET supports technology verification and high data rate experiments. The ground stations successfully demonstrated many services and applications at Ka-band in three different modes of operation: circuit switched TDMA using the satellite on-board processor, satellite switched SS-TDMA applications using the on-board Microwave Switch Matrix (MSM), and conventional transponder (bent-pipe) operation. Data rates ranged from 4.8 kbps up to 622 Mbps. Experiments included: 1) low rate (4.8- 1 00's kbps) remote data acquisition and control using small earth stations, 2) moderate rate (1-45 Mbps) experiments included full duplex voice and video conferencing and both full duplex and asymmetric data rate protocol and network evaluation using mid-size ground stations, and 3) link characterization experiments and high data rate (155-622 Mbps) terrestrial and satellite interoperability application experiments conducted by a consortium of experimenters using the large transportable ground stations.

Reinhart, Richard C.↗
NASA NTRS2004

James Webb Space Telescope Ka-Band Trade

In August 2003 James Webb Space Telescope (JWST) had its Initial Review Confirmation Assessment Briefing with NASA HQ management. This is a major milestone as the project was approved to proceed from Phase A to B, and NASA will commit funds for the project towards meeting its science goals from the Earth-Sun s Lagrange 2 (L2) environment. At this briefing, the Project was asked, "to take another look" into using, the JPL s Deep Space Network (DSN) as the provider of ground stations and evaluate other ground station options. The current operations concept assumes S-band and X-band communications with a daily &hour contact using the DSN with the goal of transmitting over 250 Gigabit (Gb) of data to the ground. The Project has initiated a trade study to look at this activity, and we would like to share the result of the trade in the conference. Early concept trades tends to focus on the "normal" operation mode of supporting telemetry (science and engineering), command and radio metrics. Entering the design phase, we find that we have the unique ranging requirement for our L2 orbit using alternating ground stations located in different hemispheres. The trade must also address emergency operations (which are covered when using the DSN). This paper describes the issues confronting this Project and how the DSN and the JWST Project are working together to find an optimized approach for meeting these issues. We believe this trade is of major interest for future Code S and other L2 missions in that JWST will set the standard.

Gal-Edd, Jonathan↗