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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

The Lunar Communications Relay Unit system design

Lunar Surface Exploration by Early Apollo Astronauts was limited by the range capabilities and configuration of the surface communications. To permit greater scientific yield from manned lunar exploration, it was necessary to provide improvements in crew mobility plus communications compatible with extended extravehicular activity. Expansion of EVA** and video communications capability was constrained by the requirement of interfacing with existing earth and lunar surface facilities, vehicle payload requirements, and crew operational considerations. Various trade-off s were conducted to permit rapid development of a feasible communication’s system which are described herein. The revision of the EVA mission profile necessitated establishment of new signal design parameters compatible with mobile and fixed site relay configurations. The design approach selected required strict discipline to enable integration of the electrical, mechanical, thermal and human factor fields. The resultant design of the Lunar Communications Relay Unit is a portable communications package to provide relay-to-earth of voice, data and color television from lunar surface locations far beyond the LM landing site and relay of ground voice to the EVA crew.

B. Trachtenberg↗
NASA NTRS2003

Cost and Performance Comparison of an Earth-Orbiting Optical Communication Relay Transceiver and a Ground-Based Optical Receiver Subnet

Optical communications can provide high-data-rate telemetry from deep-space probes with subsystems that have lower mass, consume less power, and are smaller than their radio frequency (RF) counterparts. However, because optical communication is more a.ected by weather than is RF communication, it requires groundstation site diversity to mitigate the adverse e.ects of inclement weather on the link. An optical relay satellite is not a.ected by weather and can provide 24-hour coverage of deep-space probes. Using such a relay satellite for the deep-space link and an 8.4-GHz (X-band) link to a ground station would support high-data-rate links from small deep-space probes with very little link loss due to inclement weather. We have reviewed past JPL-funded work on RF and optical relay satellites, and on proposed clustered and linearly dispersed optical subnets. Cost comparisons show that the life cycle costs of a 7-m optical relay station based on the heritage of the Next Generation Space Telescope is comparable to that of an 8-station subnet of 10- m optical ground stations. This makes the relay link an attractive option vis- a-vis a ground-station network.

Wilson, K. E.↗
NASA NTRS1965

GSFC Relay Communications Satellite Test Station

Telemetry, command, wideband communications transmitter, receiver, video, frequency-division multiplex telephone, and tracking and antenna systems for Relay I satellite test stations

WIDEBAND COMMUNICATION↗
NASA NTRS2016

Overview and Status of the Laser Communication Relay Demonstration

NASA is presently developing first all optical high data rate satellite relay system, LCRD. To be flown on commercial geosynchronous satellite, it will communicate at DPSK and PPM modulation formats up to 1.244 Gbps. LCRD flight payload is being developed by NASA's Goddard Space Flight Center. The two ground stations, one on Table Mountain in CA, developed by NASA's Jet Propulsion Laboratory and another on Hawaiian island will enable bi-directional relay operation and ground sites diversity experiments. In this paper we will report on the current state of LCRD system development, planned operational scenarios and expected system performance.

free space optical communication↗
NASA NTRSDate not supplied

Flight and Direct to Earth/Space Relay Communication System Architecture for GSFC CubeSat Missions

The CubeSat platform is finding increasing use in space science applications due to its low cost and comparative ease of launch. It is becoming a key scientific discovery tool in low Earth orbit (LEO) and beyond, including geosynchronous equatorial orbit (GEO), the Lagrange Points, Lunar missions, and more. The increasing complexity of these missions and their scientific goals must be supported by equal advancements in communications technology. Higher data rates and greater reliability are required every year. However, the reduced Size, Weight, and Power (SWaP) constraints of CubeSat platforms introduce unique challenges in the area of satellite communications. There is currently a lack of communication equipment tailored specifically to the CubeSat platform. This lack of standardized, tested equipment extends development time and reduces mission confidence. Furthermore, missions utilizing the CubeSat platform are often subject to more difficult design constraints. Antenna placement, size, and pointing are often subordinate to the requirements of the payload instruments and mission goals. Traditional link margin estimation techniques are insufficient in these cases, as they emphasize worst case scenarios. In reality the actual link parameters may vary widely even during a single pass. This presents new challenges in predicting communications performance and scheduling ground station contacts, but also new opportunities for improving efficiency. This paper presents the integration, testing, and validation process for a new software defined radio (SDR) designed for the CubeSat platform in conjunction with Vulcan Wireless, Inc. The SDR is planned for use on 5 upcoming CubeSat missions at NASAs Goddard Space Flight Center (GSFC) including a Geosynchronous Transfer Orbit (GTO) mission and it may also serve as a standard and well-tested option for future missions by enabling a standardized, rapid and low cost CubeSat communication system network integration process. Detailed simulations have been developed to estimate the communication performance of these missions, taking the unique antenna placements and attitude behavior of each satellite into account. These simulations allow a much more accurate analysis of the expected link margin, which varies considerably during each pass for the NASA Space Relay (SR) and Direct to Earth (DTE) network. The modelling procedures are outlined, and the results are used to predict communications performance of the missions.

Space Networks↗
NASA NTRS2017

Relay Communications Support to the ExoMars Schiaparelli Lander

The European Space Agency’s ExoMars Trace Gas Orbiter (TGO) arrived at Mars on October 19, 2016, three days after releasing the Schiaparelli Lander on a ballistic trajectory to Meridiani Planum. During the separation event, and subsequently during Schiaparelli’s Entry, Descent, and Landing (EDL), the NASA-provided Electra UHF payload onboard TGO was used to record signals from the Schiaparelli Lander for post-processing on the ground to recover both tracking of the lander’s carrier signal and reconstruction of the lander’s 8 kb/s telemetry. In addition, ESA’s Mars Express orbiter also recorded the Schiaparelli signal, with ground post-processing providing independent tracking of the lander carrier signal, and the Giant Metrewave Radio Telescope near Pune, India was configured to provide real-time detection of the lander carrier signal. While an anomaly in the latter stages of EDL led to loss of the lander, these critical event data sets, and in particular the telemetry reconstruction enabled by the TGO Electra recording, proved essential in enabling detailed diagnosis of the anomaly. And while the loss of the lander during EDL precluded the planned surface relay operations, the preparations for that activity provide important lessons learned for future Mars relay support scenarios.

Edwards, Charles D., Jr.↗
NASA NTRS1961

Microwave Reflectivity of Deposited Aluminum Films for Passive Relay Communications

Reflectivity measurements from 400 Mc/sec to 10 kMc/sec on 2,200 A thick aluminum deposited on 1/2-mil-thick Mylar film show this material to be a very good reflector of radio waves. Measurements made under conditions of stress and temperature which would be encountered by a communications sphere, such as Project Echo (1960 Iota), showed very little deterioration of the high reflectivity. packaging effects also caused very little reflectivity change. Under conditions of severe temperature cycling, aluminum removal and decreased reflectivity occurred.

Cuddihy, William F.↗