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NASA NTRS2018

Ka-band High-Rate Downlink System for the NISAR Mission

This paper provides a description and analyses of the high-rate Ka-band telecom system for the upcoming NISAR (NASA-ISRO Synthetic Aperture Radar) mission. NISAR is a collaborative Earth-Science mission between National Aeronautics and Space Administration (NASA) and Indian Space Research Organization (ISRO), which features an L-band SAR instrument and an S-band SAR instrument. The simultaneous dual-frequency radar system at peak rates will produce data at gigabit-per-second speeds, which drives the data-volume requirements. The key driving requirement for the payload communication subsystem is to provide a minimum of 26 Terabits per day of radar science data to the ground. The high-rate transmitter on the flight system is a software-defined radio developed at the Jet Propulsion Laboratory (JPL), based on the Universal Space Transponder platform, providing an offset quadrature phase shift key modulated waveform with Low-Density Parity-Check encoding of the data transfer frames. Two transmitters used in a dual-polarization configuration with each transmitter providing two giga-symbols per second (Gsps) of coded data provides an aggregate rate of four Gsps. In this system, only one watt of signal power is necessary on each polarization to overcome propagation losses and achieve a successful RF link. Several Near Earth Network (NEN) ground station sites (Alaska in the United States, Svalbard in Norway, and Punta Arenas in Chile) are baselined for the space-to-Earth communications link. Each ground station will also feature multiple upgrades to support NISAR’s transmission starting with new Ka-band antennas, wideband downconverters and high-rate receivers. In addition, a baseband data processor called Data Acquisition Processor and Handling Network Environment (DAPHNE), newly developed by the NEN, provides data storage and connectivity to backhaul networks. With NISAR’s large quantities of data (over 3.5 Petabytes over the mission), the processing of science data will be primarily performed on a cloud system to reduce the overall cost to the mission. The system described herein will be the first operational use of Gsps-class downlink rates on an Earth-Science mission.

Dissanayake, Asoka↗
NASA NTRS1976

Satellites for distress alerting and locating: Report by Interagency Committee for Search and Rescue Ad Hoc Working Group

The background behind the congressional legislation that led to the requirement for the Emergency Locator Transmitter (ELT) and the Emergency Position-Indicating Radio Beacon (EPIRB) to be installed on certain types of aircraft and inspected marine vessels respectively is discussed. The DAL problem is discussed for existing ELT and EPIRB equipped aircraft and ships. It is recognized that the DAL requirement for CONUS and Alaska and the maritime regions are not identical. In order to address the serious DAL problem which currently exists in CONUS and Alaska, a low orbiting satellite system evolves as the most viable and cost effective alternative that satisfies the overall SAR system design requirements. A satellite system designed to meet the needs of the maritime regions could be either low orbiting or geostationary. The conclusions drawn from this report support the recommendation to proceed with the implementation of a SAR orbiting satellite system.

Ehrlich, E.↗
NASA NTRS1978

Assessment of needs for satellite tracking of birds and suggestions for expediting a program

Equipment development and testing, animal-instrument interphase or attachment methods, and the evaluation of various feasibility-tracking experiments with raptors are described as well as suggestions for expediting a future program. Results of animal-instrument interphases work indicate that large free-flying birds can be successfully instrumented with radio packages comparable in weight to satellite-transmitter packages. The 401 MHz frequency proved satisfactory for a combination of satellite and ground tracking of migrating birds. Tests run for nearly a year with the Nimbus 6 satellite and a miniaturized, one-watt prototype RAMS transmitter produced encouraging results in regard to location accuracy, frequency of contact with satellite and use of whip antennas. A future program is recommended with priority given to development of six operational transmitters for feasibility experiments.

Craighead, F. C., Jr.↗
NASA NTRS1978

Miniature interferometer terminals for earth surveying

A system of miniature radio interferometer terminals was proposed for the measurement of vector baselines with uncertainties ranging from the millimeter to the centimeter level for baseline lengths ranging, respectively, from a few to a few hundred kilometers. Each terminal would have no moving parts, could be packaged in a volume of less than 0.1 cu m, and would operate unattended. These units would receive radio signals from low-power (10 w) transmitters on earth-orbiting satellites. The baselines between units could be determined virtually instantaneously and monitored continuously as long as at least four satellites were visible simultaneously.

Counselman, C. C., III↗
NASA NTRS1985

Low-Frequency Navigational System

Accurate vehicle position determination over 50 by 50-km service area accomplished by low-frequency-radio navigational system comprised of four frequency/phase comparison transmitters and receivers. Use of grid-calibration table permits accurate position determination in vehicle receiver system.

Wallis, D. E.↗
NASA NTRS2000

GPS=A Good Candidate for Data Assimilation?

The Global Positioning System (GPS) enables positioning anywhere about our planet. The microwave signals sent by the 24 transmitters are sensitive to the atmosphere. Using the radio occultation technique, it is possible to perform soundings, with a Low Earth Orbiter (700 km) GPS receiver. The insensitiveness to clouds and aerosols, the relatively high vertical resolution (1.5 km), the self-calibration and stability of the GPS make it a priori a potentially good observing system candidate for data assimilation. A low-computing cost simple method to retrieve both temperature and humidity will be presented. Comparisons with radiosonde show the capability of the GPS to resolve the tropopause. Options for using GPS for data assimilation and remaining issues will be discussed.

Poli, P.↗
NASA NTRS1978

Intruder Detector

The shadowy prowler is attempting a break-in, unaware that his presence has already been detected and reported by the device in the lower left corner of the photo. It is part of a three-element ntruder Detecti on System developed by NASA's Ames Research Center from technology acquired in the Apollo lunar exploration program. Apollo astronauts left behind on the moon small portable seismic (shock) detectors to record subsurface vibrations and transmit to Earth data on the moon's density and thickness. A similar seismic detector is the key component of the lntruder Detection System. Encased in a stainless steel tube, the detector is implanted in the ground outside the facility being protected-home, bank, industrial or other facilities. The vibration-sensing detector picks up the footstep of anyone within a preset range. The detector is connected by cable to the transmitter, which relays the warning to a portable radio receiver. The radio alerts plant guards or home occupants by emitting an audible tone burst for each footstep.

Source record↗
NASA NTRS1991

Development of a moon-based magnetospheric and coronal imager using a large broadband array

The 'Missions to and from Planet Earth' mandated by President Bush in 1989 provide a unique opportunity for magnetospheric and coronal plasma physicists to cooperate with low frequency radio astronomers in the development of an advanced experiment designed for the lunar surface. A large active lunar based array would sound the Earth's magnetosphere at VLF frequencies and the solar corona at decametric wavelengths allowing plasma physicists to map both the Earth's magnetosphere and those regions in the solar corona that trigger precursors to solar flares. With the transmitter silent, the array would become the ideal low frequency radio telescope, examining both geospace emissions such as auroral kilometric radiation and extraterrestrial signals from the planets, pulsars, supernova remnants, and active galactic nuclei. Both experiments satisfy requirements mandated in both 'Mission to Planet Earth' and in 'Mission from Planet Earth.' By proposing a cooperative effort both communities (plasma physicists and radio astronomers) stand to benefit. Jim Green, Director of the NASA Space Science Data Center (NSSDC) at GSFC; Tony Phillips, Research Fellow at California Institute of Technology; T. D. Carr, Director of the University of Florida Radio Observatory (UFRO) and the author are enlisting the cooperation of the scientific community in defining the system specifications. Some components, such as the receivers, will be standard 'off-the-shelf' items, and hence will require little developmental research. However, the individual antenna elements and the phasing and matching networks will require some R&D to satisfy the frequency requirements (20 KHz-40 MHz). By flying the experiment in Earth orbit first, Dr. Green proposes to gather valuable magnetospheric data as well as to prove the principle of the large moon based experiment. He claims that funding for the preliminary ground based studies at the UFRO may be available as early as FY-92.

Lebo, George↗
NASA NTRS1972

Operations and maintenance manual for a scale-model lunar roving vehicle

A one-sixth scale model of the lunar roving vehicle used in the Apollo 15 mission was built and instrumented to conduct model studies of vehicle mobility. The model was free running under radio control and was equipped with a lightweight telemetry transmitter that allowed 16 channels of data to be gathered simultaneously. String payout and fifth-wheel devices were developed to measure vehicle velocity. Other real-time measurements included wheel torque, wheel speed, center-of-gravity accelerations, and steering forces. Calibration, operations, and maintenance procedures were worked out. Details of the development of the instrumentation, its maintenance, and some of the problems encountered, are recorded serve as a preliminary operations and maintenance manual for this specific model. In addition, information regarding soil processing and testing that may be useful to NASA personnel planning mobility research with the model in soil is furnished.

Lessem, A. S.↗
NASA NTRS1999

Validation of the AMSU-B Bias Corrections Based on Satellite Measurements from SSM/T-2

The NOAA-15 Advanced Microwave Sounding Unit-B (AMSU-B) was designed in the same spirit as the Special Sensor Microwave Water Vapor Profiler (SSM/T-2) on board the DMSP F11-14 satellites, to perform remote sensing of spatial and temporal variations in mid and upper troposphere humidity. While the SSM/T-2 instruments have a 48 km spatial resolution at nadir and 28 beam positions per scan, AMSU-B provides an improvement with a 16 km spatial resolution at nadir and 90 beam positions per scan. The AMSU-B instrument, though, has been experiencing radio frequency interference (RFI) contamination from the NOAA-15 transmitters whose effect is dependent upon channel, geographic location, and current spacecraft antenna configuration. This has lead to large cross-track biases reaching as high as 100 Kelvin for channel 17 (150 GHz) and 50 Kelvin for channel 19 (183 +/-3 GHz). NOAA-NESDIS has recently provided a series of bias corrections for AMSU-B data starting from March, 1999. These corrections are available for each of the five channels, for every third field of view, and for three cycles within an eight second period. There is also a quality indicator in each data record to indicate whether or not the bias corrections should be applied. As a precursor to performing retrievals of mid and upper troposphere humidity, a validation study is performed by statistically analyzing the differences between the F14 SSM/T-2 and the bias corrected AMSU-B brightness temperatures for three months in the spring of 1999.

Kolodner, Marc A.↗
NASA NTRS2010

Communication path for extreme environments

Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.

Jorgensen, Charles C.↗
NASA NTRS2024

Investigation into the Origin of the RF Phase Noise for the LISA Laser Transmitter

The Laser Interferometer Space Antenna (LISA) mission is a collaborative consortium led by the European Space Agency (ESA)in cooperation with the National Aeronautics and Space Administration (NASA). LISA’s goal is to capture gravitational wave events, such as spacetime distortions caused by massive orbiting bodies. Multiple low noise, single frequency master oscillator power amplifier (MOPA) lasers with a polarization-maintaining Yb-fiber amplifier will serve as the light sources for the LISA observatory. The NASA Goddard Space Flight Center (GSFC)is currently developing the laser transmitters for this project. The LISA lasers will carry radio frequency (RF)sidebands for exchanging reference RF clock information between spacecrafts. Excess phase noise, especially carrier-sideband differential phase noise added to the modulation side band by the phase modulator and the fiber amplifier, becomes a concern. In the gravitational wave frequency ranges, leading sources of this RF “differential” phase noise can be both intrinsic and extrinsic. Examples of intrinsic sources include thermal load on the active fiber, thermo-mechanical induced birefringence, and nonlinearities in the various passive and active fibers. Extrinsic sources can include external temperature fluctuations and infrasonic mechanical strain or vibrations. These noise spectra usually include both white and pink (1/f) thermal noise contributions. This work investigates the physical origins and impact of these sources of RF phase noise, and their characteristic spectra and management will be discussed.

Laser Interferometer Space Antenna↗
NASA NTRS1995

Instrument technology for magnetosphere plasma imaging from high Earth orbit. Design of a radio plasma sounder

The use of radio sounding techniques for the study of the ionospheric plasma dates back to G. Briet and M. A. Tuve in 1926. Ground based swept frequency sounders can monitor the electron number density (N(sub e)) as a function of height (the N(sub e) profile). These early instruments evolved into a global network that produced high-resolution displays of echo time delay vs frequency on 35-mm film. These instruments provided the foundation for the success of the International Geophysical Year (1958). The Alouette and International Satellites for Ionospheric Studies (ISIS) programs pioneered the used of spaceborne, swept frequency sounders to obtain N(sub e) profiles of the topside of the ionosphere, from a position above the electron density maximum. Repeated measurements during the orbit produced an orbital plane contour which routinely provided density measurements to within 10%. The Alouette/ISIS experience also showed that even with a high powered transmitter (compared to the low power sounder possible today) a radio sounder can be compatible with other imaging instruments on the same satellite. Digital technology was used on later spacecraft developed by the Japanese (the EXOS C and D) and the Soviets (Intercosmos 19 and Cosmos 1809). However, a full coherent pulse compression and spectral integrating capability, such as exist today for ground-based sounders (Reinisch et al., 1992), has never been put into space. NASA's 1990 Space Physics Strategy Implementation Study "The NASA Space Physics Program from 1995 to 2010" suggested using radio sounders to study the plasmasphere and the magnetopause and its boundary layers (Green and Fung, 1993). Both the magnetopause and plasmasphere, as well as the cusp and boundary layers, can be observed by a radio sounder in a high-inclination polar orbit with an apogee greater than 6 R(sub e) (Reiff et al., 1994; Calvert et al., 1995). Magnetospheric radio sounding from space will provide remote density measurements of unprecedented precision and coverage in the plasmasphere, inner magnetosphere and magnetopause, from which the structure, inter-relationship, and variations of different plasma regions can be determined (Armstrong Johnson, 1995). A space-borne Radio Plasma Imager (RPI) could provide a unique global view of the magnetosphere revealing the underlying structure of remote plasma regions, thereby providing a framework for the interpretation of images obtained by other techniques as identified in the technical areas TA1 to TA4 in the MSFC NRA8-8.

Haines, D. Mark↗
NASA NTRS1976

ALSEP: Quasar differential VLBI

A program of Apollo Lunar Surface Experiments Package (ALSEP)-Quasar Very Long Baseline Interferometry (VLBI) is being reported. These observations primarily employ a 4 antenna technique, whereby simultaneous observations with two antennas at each end of an intercontinental baseline are used to derive the differential interferometric phase between a compact extragalactic radio source (usually a quasar) and a number of ALSEP transmitters on the lunar surface. A continous ALSEP-quasar differential phase history over a few hour period leads to extremely high angular accuracy in measuring the lunar position against the quasar reference frame. This application of the 4 antenna technique has been underway for more than a year and is now producing high quality data utilizing Deep Space Network (DSN) stations in Australia, Spain, and Goldstone, California, as well as the Spaceflight Tracking and Data Network (STDN) Apollo station at Goldstone.

Slade, M. A.↗
NASA NTRS1977

ALSEP-quasar differential VLBI

A program of ALSEP-quasar very-long-baseline interferometry (VLBI) is being carried out. These observations employ primarily a 'four-antenna' technique whereby simultaneous observations with two antennas at each end of an intercontinental baseline are used to derive the differential interferometric phase between a compact extragalactic radio source (usually a quasar) and a number of ALSEP transmitters on the lunar surface. A continuous ALSEP-quasar differential phase history over a period of a few hours will lead to milliarcsecond angular accuracy in measuring the lunar position against the quasar reference frame if suitable calibration measurements are obtained. Development of this application of the four-antenna technique has been underway for more than a year and is producing high-quality data utilizing Deep Space Network stations. These high-accuracy observations are of value to tie the lunar ephemeris to a nearly inertial extragalactic reference frame, to test gravitational theories, and to measure the earth-moon tidal friction interaction.

Slade, M. A.↗
NASA NTRS1979

Apparatus for endoscopic examination

An endoscope is having a propulsion mechanism and at least one transmitter at the distal end transmitting bursts of energy waves (radio frequency or ultrasonic) for tracking the position of the distal end through the use of two or more transducers on the anterior or lateral surfaces of a patient is described. The propulsion mechanism which consists of two radially expandable bladders separated by an axially expandable bellows with only the forward bladder attached to the distal end is discussed. Alternate mechanisms are reported. A sheath on the endoscope which includes material having a sharp melting point slightly above body temperature so that the sheath is made flexible at selected sections by applying current to separate heating wires in the sections of the sheath is described.

Frazer, R. E.↗
NASA NTRS1980

Electronic search and rescue aids

There are two elements to the basic electronic search and rescue problem: a means for immediately alerting potential rescuers and an effective method to guide the rescue forces to the scene of the emergency. An Emergency Locator Transmitter (ELT) used by aircraft or an Emergency Position Indicating Radio Beacon (EPIRB) used by maritime vessels has the capability of providing for both an immediate alert and a homing signal to assist rescue forces in locating the site of the distress. This paper describes the development of ELT/EPIRB systems. Emphasis is placed on the SARSAT project, the COSPAS/SARSAT project, and an experimental 406 MHz ELT/EPIRB system.

Trudell, B. J.↗