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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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NASA NTRS2017

LCRD Optical Ground Station 1

NASA’s Laser Communications Relay Demonstration (LCRD) will demonstrate and study bi-directional space-to-ground optical links. Optical Ground Station 1 (OGS-1) for LCRD will be developed at the Optical Communications Telescope Laboratory (OCTL), a 1-meter telescope in the San Gabriel Mountains northeast of the Jet Propulsion Laboratory. This paper will present an updated overview of OGS-1, its systems and capabilities, and its preparations for integrating and verifying readiness of the completed system. It will conclude with predicted performance of the OGS-1 system.

Piazzolla, Sabino↗
NASA NTRS2001

A Ten-Meter Ground-Station Telescope for Deep-Space Optical Communications: A Preliminary Design

This article describes a telescope design for a 10-m optical ground station for deep-space communications. The design for a direct-detection optical communications telescope differs dramatically from a telescope for imaging applications. In general, the requirements for optical manufacturing and tracking performance are much less stringent for direct detection of optical signals. The technical challenge is providing a design that will operate in the daytime/nighttime conditions required for a Deep Space Network tracking application. The design presented addresses these requirements. The design will provide higher performance at lower cost than existing designs.

Britcliffe, M.↗
NASA NTRSDate not supplied

Insights and Observations from Operating a Geostationary Laser Communication Relay Mission: Operational Lessons from NASA’s Laser Communications Relay Demonstration (LCRD) and Associated Optical Ground Stations (OGSs)

The NASA Laser Communications Relay Demonstration (LCRD) has operated on orbit for the last two years. The LCRD Mission consists of a geostationary payload and two optical ground stations. This technology demonstration mission is NASA’s first two-way, end-to-end optical communications relay. LCRD has performed an extensive experiment campaign to analyze laser communication performance for extended operations. This paper discusses various lessons learned while operating the optical relay mission from early commissioning through two years of operation. Before launch, engineers and operators performed analyses to generate operational procedures based on expected LCRD performance. However, only operation on orbit can supply actual performance data. Additional topics covered in this paper include pre-launch and commissioning testing, ephemeris generation and cadence, environmental configurations, and accommodation concerns. The addition of Integrated Laser Communications Relay Demonstration Low Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T) to the optical network supplemented the LCRD team’s operational experiences and enabled them to garner new lessons learned. The authors of this paper include day-to-day flight leads who consulted with on-console operators, engineers, and subject matter experts analyzing data and experiment results to gather the lessons learned described in this paper. 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).

Lessons Learned↗
NASA NTRS1995

Compilation and Analysis of 20- and 30-GHz Rain Fade Events at the ACTS NASA Ground Station: Statistics and Model Assessment

Since the beginning of the operational phase of the NASA Research Center's Advanced Communication Technology Satellite (ACTS), signal-fade measurements have been recorded at the NASA Ground Station located in Cleveland, Ohio, with the use of the 20- and 30-GHz beacon signals. Compilations of the daily data have been statistically analyzed on a monthly and yearly basis. Such analyses have yielded relevant parameters as (1) cumulative monthly and yearly probability distributions of signal attenuation by rain, (2) attenuation duration versus attenuation threshold probabilities, and (3) rate-of-fade probabilities. Not only are such data needed for a realistic data base to support the design and performance analysis of future satellite systems, but they are necessary to assess predictions made with the ACTS Rain Attenuation Prediction Model.

Manning, Robert M.↗
NASA NTRS1996

Compilation and Analysis of 20 and 30 GHz Rain Fade Events at the ACTS NASA Ground Station: Statistics and Model Assessment

The purpose of the propagation studies within the ACTS Project Office is to acquire 20 and 30 GHz rain fade statistics using the ACTS beacon links received at the NGS (NASA Ground Station) in Cleveland. Other than the raw, statistically unprocessed rain fade events that occur in real time, relevant rain fade statistics derived from such events are the cumulative rain fade statistics as well as fade duration statistics (beyond given fade thresholds) over monthly and yearly time intervals. Concurrent with the data logging exercise, monthly maximum rainfall levels recorded at the US Weather Service at Hopkins Airport are appended to the database to facilitate comparison of observed fade statistics with those predicted by the ACTS Rain Attenuation Model. Also, the raw fade data will be in a format, complete with documentation, for use by other investigators who require realistic fade event evolution in time for simulation purposes or further analysis for comparisons with other rain fade prediction models, etc. The raw time series data from the 20 and 30 GHz beacon signals is purged of non relevant data intervals where no rain fading has occurred. All other data intervals which contain rain fade events are archived with the accompanying time stamps. The definition of just what constitutes a rain fade event will be discussed later. The archived data serves two purposes. First, all rain fade event data is recombined into a contiguous data series every month and every year; this will represent an uninterrupted record of the actual (i.e., not statistically processed) temporal evolution of rain fade at 20 and 30 GHz at the location of the NGS. The second purpose of the data in such a format is to enable a statistical analysis of prevailing propagation parameters such as cumulative distributions of attenuation on a monthly and yearly basis as well as fade duration probabilities below given fade thresholds, also on a monthly and yearly basis. In addition, various subsidiary statistics such as attenuation rate probabilities are derived. The purged raw rain fade data as well as the results of the analyzed data will be made available for use by parties in the private sector upon their request. The process which will be followed in this dissemination is outlined in this paper.

Manning, Robert M.↗
NASA NTRS2018

Streamlining Ground Station Network Compatibility Test for Small Satellites

A team of eight subject matter experts at NASA Goddard Space Flight Center (GSFC) completed a Lean Six Sigma project to identify process improvements for the compatibility test process for small satellites planning to use the NASA Near Earth Network (NEN). Ground station network compatibility testing is designed to reduce the risk to missions by resolving issues between the spacecraft's flight communication and navigation components and the ground systems prior to launch. Compatibility testing, which consists of a series of tests performed over a period of months and documented in reports, is an important step meant to prevent post-launch anomalies that could lead to expensive troubleshooting or mission failure. Compared to traditional missions, small satellite missions typically have a smaller budget and compressed schedules, which can result in small satellite projects' willingness to accept the risk associated with less comprehensive compatibility testing. Optimization and or refinement of the compatibility test process for small satellite missions could alleviate some of the pressures inherent with these factors. The goal of the Lean Six Sigma project was to develop alternative scalable methods of compatibility testing for small satellites. The Lean Six Sigma approach and the results of the project are reviewed in this paper.

Streamlining↗
NASA NTRS2012

Data Distribution System (DDS) and Solar Dynamic Observatory Ground Station (SDOGS) Integration Manager

The DDS SDOGS Integration Manager (DSIM) provides translation between native control and status formats for systems within DDS and SDOGS, and the ASIST (Advanced Spacecraft Integration and System Test) control environment in the SDO MOC (Solar Dynamics Observatory Mission Operations Center). This system was created in response for a need to centralize remote monitor and control of SDO Ground Station equipments using ASIST control environment in SDO MOC, and to have configurable table definition for equipment. It provides translation of status and monitoring information from the native systems into ASIST-readable format to display on pages in the MOC. The manager is lightweight, user friendly, and efficient. It allows data trending, correlation, and storing. It allows using ASIST as common interface for remote monitor and control of heterogeneous equipments. It also provides failover capability to back up machines.

Pham, Kim↗
NASA NTRS2003

Optical ground station site diversity for Deep Space Optical Communications the Mars Telecom Orbiter optical link

Future NASA deep space missions will fly advanced high resolution imaging instruments that will require high bandwidth links to return the huge data volumes generated by these instruments. Optical communications is a key technology for returning these large data volumes from deep space probes. Yet to cost effectively realize the high bandwidth potential of the optical link will require deployment of ground receivers in diverse locations to provide high link availability. A recent analysis of GOES weather satellite data showed that a network of ground stations located in Hawaii and the Southwest continental US can provide an average of 90% availability for the deep space optical link. JPL and AFRL are exploring the use of large telescopes in Hawaii, California, and Albuquerque to support the Mars Telesat laser communications demonstration. Designed to demonstrate multi-Mbps communications from Mars, the mission will investigate key operational strategies of future deep space optical communications network.

laser communications↗
NASA NTRS1999

ACTS Ka-band Propagation Research in a Spatially Diversified Network with Two USAT Ground Stations

Congestion in the radio spectrum below 18 GHz is stimulating greater interest in the Ka (20/30 GHz) frequency band. Transmission at these shorter wavelengths is greatly influenced by rain resulting in signal attenuation and decreased link availability. The size and projected cost of Ultra Small Aperture Terminals (USATS) make site diversity methodology attractive for rain fade compensation. Separation distances between terminals must be small to be of interest commercially. This study measures diversity gain at a separation distance <5 km and investigates utilization of S-band weather radar reflectivity in predicting diversity gain. Two USAT ground stations, separated by 2.43 km for spatial diversity, received a continuous Ka-band tone sent from NASA Glenn Research Center via the Advanced Communications Technology Satellite (ACTS) steerable antenna beam. Received signal power and rainfall were measured, and Weather Surveillance Radar-1998 Doppler (WSR-88D) data were obtained as a measure of precipitation along the USAT-to-ACTS slant path. Signal attenuation was compared for the two sites, and diversity gain was calculated for fades measured on eleven days. Correlation of WSR-88D S-band reflectivity with measured Ka-band attenuation consisted of locating radar volume elements along each slant path, converting reflectivity to Ka-band attenuation with rain rate calculation as an intermediate step. Specific attenuation for each associated path segment was summed, resulting in total attenuation along the slant path. Derived Ka-band attenuation did not correlate closely with empirical data (r = 0.239), but a measured signal fade could be matched with an increase in radar reflectivity in all fade events. Applying a low pass filter to radar reflectivity prior to deriving Ka-band attenuation improved the correlation between measured and derived signal attenuation (r = 0.733). Results indicate that site diversity at small separation distances is a viable means of rain fade compensation, and that existing models underestimate diversity gain for a subtropical climate such as Florida. Also, filtered WSR-88D reflectivity can be used for optimizing diversity terminal placement by comparing derived Ka- band attenuation between the diversity sites.

Kalu, Alex↗
NASA NTRS1994

TOMS total ozone data compared with northern latitude Dobson ground stations

Ozone measurements from the Total Ozone Mapping Spectrometer on the Nimbus 7 satellite are compared with ground-based measurements from five Dobson stations at northern latitudes to evaluate the accuracy of the TOMS data, particularly in regions north of 50 deg N. The measurements from the individual stations show mean differences from -2.5 percent up to plus 8.3 percent relative to TOMS measurements and two of the ground stations, Oslo and Longyearbyen, show a significant drift of plus 1.2 percent and plus 3.7 percent per year, respectively. It can be shown from nearly simultaneous measurements in two different wavelength double pairs at Oslo that at least 2 percent of the differences result from the use of the CC' wavelength double pair instead of the standard AD wavelength double pair. Since all Norwegian stations used the CC' wavelength double pair exclusively a similar error can be assumed for Tromso and Longyearbyren. A comparison between the tropospheric ozone content in TOMS data and from ECC ozonesonde measurements at Ny-Alesund and Bear Island shows that the amount of tropospheric ozone in the standard profiles used in the TOMS algorithm is too low, which leads to an error of about 2 percent in total ozone. Particularly at high solar zenith angles (greater than 80 deg), Dobson measurements become unreliable. They are up to 20 percent lower than TOMS measurements averaged over solar zenith angles of 88 deg to 89 deg.

Heese, B.↗
NASA NTRS1994

Advanced ground station architecture

This paper describes a new station architecture for NASA's Ground Network (GN). The architecture makes efficient use of emerging technologies to provide dramatic reductions in size, operational complexity, and operational and maintenance costs. The architecture, which is based on recent receiver work sponsored by the Office of Space Communications Advanced Systems Program, allows integration of both GN and Space Network (SN) modes of operation in the same electronics system. It is highly configurable through software and the use of charged coupled device (CCD) technology to provide a wide range of operating modes. Moreover, it affords modularity of features which are optional depending on the application. The resulting system incorporates advanced RF, digital, and remote control technology capable of introducing significant operational, performance, and cost benefits to a variety of NASA communications and tracking applications.

Zillig, David↗
NASA NTRS1985

Whistler-triggered VLF noise bursts observed on the DE-1 satellite and simultaneously at Antarctic ground stations

Simultaneous observations of whistler-triggered very low-frequency noise bursts on the ground at Anarctic stations, Halley and Siple, and on the high-altitude satellite DE-1 are reported. Results of a case study from June 25, 1982 in which the satellite data were recorded near 25 deg south magnetic latitude and the L = 4.7 magnetic shell, are presented. Analysis indicates that the chorus bursts that are triggered in whistler ducts travel downwards in the ducts to low altitudes in the ionosphere, and that propagation to DE-1 is by upward reflection into a nonducted mode. A means of estimating the propagation characteristics of the wave bursts is provided by comparisons of nonducted signals from the Siple transmitter and discrete periodic emissions. The ducted-nonducted mode conversion process is a mechanism for the large-scale spreading into the magnetosphere of coherent whistler-mode wave energy which is generated, amplified, or triggered in small localized ducts. The DE-1 data show that a strong interaction exists between whistler-triggered noise bursts and prevailing hiss levels.

Smith, A. J.↗
NASA NTRS1991

GTEX: An expert system for diagnosing faults in satellite ground stations

A proof of concept expert system called Ground Terminal Expert (GTEX) was developed at The University of Akron in collaboration with NASA Lewis Research Center. The objective of GTEX is to aid in diagnosing data faults occurring with a digital ground terminal. This strategy can also be applied to the Very Small Aperture Terminal (VSAT) technology. An expert system which detects and diagnoses faults would enhance the performance of the VSAT by improving reliability and reducing maintenance time. GTEX is capable of detecting faults, isolating the cause and recommending appropriate actions. Isolation of faults is completed to board-level modules. A graphical user interface provides control and a medium where data can be requested and cryptic information logically displayed. Interaction with GTEX consists of user responses and input from data files. The use of data files provides a method of simulating dynamic interaction between the digital ground terminal and the expert system. GTEX as described is capable of both improving reliability and reducing the time required for necessary maintenance.

Schlegelmilch, Richard F.↗