Search NASA⌕ Search

SEARCH · Search NASA

Results for “GPS Receiver”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Spacecraft applications of advanced global positioning system technology

This is the final report on the Texas Instruments Incorporated (TI) simulations study of Spacecraft Application of Advanced Global Positioning System (GPS) Technology. This work was conducted for the NASA Johnson Space Center (JSC) under contract NAS9-17781. GPS, in addition to its baselined capability as a highly accurate spacecraft navigation system, can provide traffic control, attitude control, structural control, and uniform time base. In Phase 1 of this program, another contractor investigated the potential of GPS in these four areas and compared GPS to other techniques. This contract was for the Phase 2 effort, to study the performance of GPS for these spacecraft applications through computer simulations. TI had previously developed simulation programs for GPS differential navigation and attitude measurement. These programs were adapted for these specific spacecraft applications. In addition, TI has extensive expertise in the design and production of advanced GPS receivers, including space-qualified GPS receivers. We have drawn on this background to augment the simulation results in the system level overview, which is Section 2 of this report.

Source record↗
NASA NTRS1992

GPS meteorology - Remote sensing of atmospheric water vapor using the Global Positioning System

We present a new approach to remote sensing of water vapor based on the Global Positioning System (GPS). Geodesists and geophysicists have devised methods for estimating the extent to which signals propagating from GPS satellites to ground-based GPS receivers are delayed by atmospheric water vapor. This delay is parameterized in terms of a time-varying zenith wet delay (ZWD) which is retrieved by stochastic filtering of the GPS data. Given surface temperature and pressure readings at the GPS receiver, the retrieved ZWD can be transformed with very little additional uncertainty into an estimate of the integrated water vapor (IWV) overlying that receiver. Networks of continuously operating GPS receivers are being constructed by geodesists, geophysicists, and government and military agencies, in order to implement a wide range of positioning capabilities. These emerging GPS networks offer the possibility of observing the horizontal distribution of IWV or, equivalently, precipitate water with unprecedented coverage and a temporal resolution of the order of 10 min. These measurements could be utilized in operational weather forecasting and in fundamental research into atmospheric storm systems, the hydrologic cycle, atmospheric chemistry, and global climate change.

Bevis, Michael↗
NASA NTRS1995

GPS as an orbit determination subsystems

This paper evaluates the use of Global Positioning System (GPS) receivers as a primary source of tracking data for low-Earth orbit satellites. GPS data is an alternative to using range, azimuth, elevation, and range-rate (RAER) data from the Air Force Satellite Control Network antennas, the Space Ground Link System (SGLS). This evaluation is applicable to missions such as Skipper, a joint U.S. and Russian atmosphere research mission, that will rely on a GPS receiver as a primary tracking data source. The Detachment 2, Space and Missile Systems Center's Test Support Complex (TSC) conducted the evaluation based on receiver data from the Space Test Experiment Platform Mission O (STEP-O) and Advanced Photovoltaic and Electronics Experiments (APEX) satellites. The TSC performed orbit reconstruction and prediction on the STEP-0 and APEX vehicles using GPS receiver navigation solution data, SGLS RAER data, and SGLS anglesonly (azimuth and elevation) data. For the STEP-O case, the navigation solution based orbits proved to be more accurate than SGLS RAER based orbits. For the APEX case, navigation solution based orbits proved to be less accurate than SGLS RAER based orbits for orbit prediction, and results for orbit reconstruction were inconclusive due to the lack of a precise truth orbit. After evaluating several different GPS data processing methods, the TSC concluded that using GPS navigation solution data is a viable alternative to using SGLS RAER data.

Fennessey, Richard↗
NASA NTRS2004

Evaluation of a Mobile Phone for Aircraft GPS Interference

Measurements of spurious emissions from a mobile phone are conducted in a reverberation chamber for the Global Positioning System (GPS) radio frequency band. This phone model was previously determined to have caused interference to several aircraft GPS receivers. Interference path loss (IPL) factors are applied to the emission data, and the outcome compared against GPS receiver susceptibility. The resulting negative safety margins indicate there are risks to aircraft GPS systems. The maximum emission level from the phone is also shown to be comparable with some laptop computer's emissions, implying that laptop computers can provide similar risks to aircraft GPS receivers.

Nguyen, Truong X.↗
NASA NTRS2001

TT and C - First TDRSS, Then Commercial GEO and Big LEO and Now through LEO

The advent of low earth orbit (LEO) commercial communications satellites provides an opportunity to dramatically reduce Telemetry Tracking and Control (TT&C) costs of launch vehicles and Unpiloted Aerial Vehicles (UAVs) by reducing or eliminating ground infrastructure. Personnel from the Goddard Space Flight Center Wallops Flight Facility (GSFC/WFF) in Virginia have successfully used commercial GEO & Big LEO communications satellites for Long Duration Balloon flight TT&C. In addition, TDRSS capability for these balloons has been developed by WFF for the Ultra Long Duration Balloons with the first test flight launch in January 2001 for one global circumnavigation at 120,000 feet altitude launched from Alice Springs. Australia. Numerous other low cost applications can new utilize the commercial LEO satellites for TT&C. The Flight Modern became a GSFC/WFF Advanced Range Technology Initiative (ARTI) in an effort to streamline TT&C capability to the user community at low cost. Phase I ground tests of The Flight Modem verified downlink communications quality of service and measured transmission latencies. These tests were completed last year, Phase II consisting of aircraft flight tests provide much of the data presented in this paper. Phase III of the Flight Modern baseline test program is a demonstration of the ruggedized version of the WFF Flight Modem flown on one sounding rocket launched from Sweden. Flights of opportunity have been and are being actively pursued with other centers, ranges and users at universities. The WFF goal is to reduce TT&C costs by providing a low cost COTS Flight Modem with a User Handbook containing system capability and limitation descriptions. Additionally, since data transmission is by packetized Internet Protocol (IP), data can be received and commands initialed from practically any location with no infrastructure. The WFF, like most ranges, has been using GPS receivers on sounding rockets and long duration balloons for several years, The WFF Flight Modem contains a GPS receiver to provide vehicle position for tracking and vehicle recovery. The system architecture which integrates antennas, GPS receiver, commercial satellite packet data modem. and a single board computer with custom software is described and a number of technical challenges are discussed along with the plan for their resolution. These include antenna development, high Doppler rates, reliability, environmental ruggedness, hand over between satellites and data security. An aggressive test plan is included which in addition to environmental Testing measures bit error rate latency and antenna patterns. Additional flight tests are planned far the near future on aircraft, long duration balloons and sounding rockets and these results as well as the current status of the project arc reported. Use of the WFF Flight Modem on small satellites is also being pursued. The LEO satellite constellation altitude above 1400 km is not an obstacle because most spacecraft do not require continuous Communications. The challenge is scheduling where store and forward techniques for command are required and downlink when the communications link allows connection (above 60 percent of the time depending on the satellite altitude). Sophisticated scheduling techniques utilizing 2-line orbital element sets available on the NASA/NORAD Internet site could be implemented for rare special cases. The current 9600 baud rate of the LEO communications link may be increased With special techniques that are planned for development in the WFF Flight Modem project.

Morgan, Dwayne↗
NASA NTRS1996

Deconvolution Approach to Carrier and Code Multipath Error Elimination in High Precision GPS

This paper proposes a novel technique based on the deconvolution approach of the simultaneous estimation and compensation of the multipath estimation errors in both the carrier phase lock and the code delay lock loops in GPS receivers. Simulation results are presented showing that the proposed GPS receiver algorithm achieves high precision in the range and differential range estimation in various GPS precision applications such as spacecraft attitude control, even in a relatively severe multipath environment.

GPS↗
NASA NTRS1993

Gravity recovery analysis using GPS for STEP and a low-low satellite mission

Global Positioning System (GPS) receivers on low Earth orbiting satellites can provide three-dimensional global tracking with sub-decimeter orbit accuracy. The precise GPS data can additionally be used to refine the Earth's gravity field. Satellite Test of the Equivalence Principle (STEP) is a proposed European Space Agency mission which will carry a flight GPS receiver. Using a realistic scenario for processing 5 days of GPS data, a covariance analysis is performed to obtain the expected improvement in the gravity field. Additionally, a similar analysis is then repeated for two low Earth orbiting satellites, each equipped with GPS receivers and with precise ranging measurements between them.

Muellerschroen, Ronald J.↗
NASA NTRS2009

Radiation-hardened fast acquisition/weak signal tracking system and method

A global positioning system (GPS) receiver and method of acquiring and tracking GPS signals comprises an antenna adapted to receive GPS signals; an analog radio frequency device operatively connected to the antenna and adapted to convert the GPS signals from an analog format to a digital format; a plurality of GPS signal tracking correlators operatively connected to the analog RF device; a GPS signal acquisition component operatively connected to the analog RF device and the plurality of GPS signal tracking correlators, wherein the GPS signal acquisition component is adapted to calculate a maximum vector on a databit correlation grid; and a microprocessor operatively connected to the plurality of GPS signal tracking correlators and the GPS signal acquisition component, wherein the microprocessor is adapted to compare the maximum vector with a predetermined correlation threshold to allow the GPS signal to be fully acquired and tracked.

Winternitz, Luke↗
NASA NTRS2003

Achieving and Validating the 1-centimeter Orbit: JASON-1 Precision Orbit Determination Using GPS, SLR, DORIS and Altimeter data

Jason-1, launched on December 7, 2001, is continuing the time series of centimeter level ocean topography observations as the follow-on to the highly successful TOPEX/POSEIDON (T/P) radar altimeter satellite. The precision orbit determination (POD) is a critical component to meeting the ocean topography goals of the mission. Jason-1 is no exception and has set a 1 cm radial orbit accuracy goal, which represents a factor of two improvement over what is currently being achieved for T/P. The challenge to precision orbit determination (POD) is both achieving the 1 cm radial orbit accuracy and evaluating and validating the performance of the 1 cm orbit. Fortunately, Jason-1 POD can rely on four independent tracking data types including near continuous tracking data from the dual frequency codeless BlackJack GPS receiver. In addition, to the enhanced GPS receiver, Jason-1 carries significantly improved SLR and DORIS tracking systems along with the altimeter itself. We demonstrate the 1 cm radial orbit accuracy goal has been achieved using GPS data alone in a reduced dynamic solution. It is also shown that adding SLR data to the GPS-based solutions improves the orbits even further. In order to assess the performance of these orbits it is necessary to process all of the available tracking data (GPS, SLR, DORIS and altimeter crossover differences) as either dependent or independent of the orbit solutions. It was also necessary to compute orbit solutions using various combinations of the four available tracking data in order to independently assess the orbit performance. Towards this end, we have greatly improved orbits determined solely from SLR+DORIS data by applying the reduced dynamic solution strategy. In addition, we have computed reduced dynamic orbits based on SLR, DORIS and crossover data that are a significant improvement over the SLR and DORIS based dynamic solutions. These solutions provide the best performing orbits for independent validation of the GPS-based reduced dynamic orbits.

Luthcke, Scott B.↗
NASA NTRS1986

The March 1985 demonstration of the fiducial network concept for GPS geodesy: A preliminary report

The first field tests in preparation for the NASA Global Positioning System (GPS) Caribbean Initiative were conducted in late March and Early April of 1985. The GPS receivers were located at the POLARIS Very Long Base Interferometry (VLBI) stations at Westford, Massachusetts; Richmond, Florida; and Ft. Davis, Texas; and at the Mojave, Owens Valley, and Hat Creek VLBI stations in California. Other mobile receivers were placed near Mammoth Lakes, California; Pt. Mugu, California; Austin, Texas; and Dahlgren, Virginia. These sites were equipped with a combination of GPS receiver types, including SERIES-X, TI-4100 and AFGL dual frequency receivers. The principal objectives of these tests were the demonstration of the fiducial network concept for precise GPS geodesy, the performance assessment of the participating GPS receiver types, and to conduct the first in a series of experiments to monitor ground deformation in the Mammoth Lakes-Long Valley caldera region in California. Other objectives included the testing of the water vapor radiometers for the calibration of GPS data, the development of efficient procedures for planning and coordinating GPS field exercise, the establishment of institutional interfaces for future cooperating ventures, the testing of the GPS Data Analysis Software (GIPSY, for GPS Inferred Positioning SYstem), and the establishment of a set of calibration baselines in California. Preliminary reports of the success of the field tests, including receiver performance and data quality, and on the status of the data analysis software are given.

Davidson, J. M.↗
NASA NTRS1988

Design and predicted performance of the GPS demonstration receiver for the NASA Topex satellite

NASA's Ocean Topography Experiment (Topex) satellite will perform topographic ocean mapping. Topex will carry an experimental tracking system based on the use of GPS (Global Positioning System). An onboard GPS Demonstration Receiver (GPSDR) will be used with a network of up to ten receivers at precisely known ground sites. Following a brief overview of the Topex mission and its derived accuracy requirements, the authors describe the design of the GPSDR. The major hardware and software components are reviewed and discussed. Projected receiver tracking and navigation performance measures are presented and discussed.

Carson, Lance↗
NASA NTRS1988

Airborne lidar global positioning investigations

The Global Positioning System (GPS) network of satellites shows high promise of revolutionizing methods for conducting surveying, navigation, and positioning. This is especially true in the case of airborne or satellite positioning. A single GPS receiver (suitably adapted for aircraft deployment) can yield positioning accuracies (world-wide) in the order of 30 to 50 m vertically, as well as horizontally. This accuracy is dramatically improved when a second GPS receiver is positioned at a known horizontal and vertical reference. Absolute horizontal and vertical positioning of 1 to 2 m are easily achieved over areas of separation of tens of km. If four common satellites remain in lock in both receivers, then differential phase pseudo-ranges on the GPS L-band carrier can be utilized to achieve accuracies of + or - 10 cm and perhaps as good as + or - 2 cm. The initial proof of concept investigation for airborne positioning using the phase difference between the airborne and stationary GPS receivers was conducted and is examined.

Krabill, W. B.↗
NASA NTRS1999

Tracking the Relative Motion of Four Space Payloads Launched from a Sub-Orbital NASA Rocket

One problem, which is comparatively new in the field of GPS applications, is the determination of the relative trajectories of space vehicles. Applications include the docking of spacecraft, collision avoidance in the area of space stations, and trajectory reconstruction of multiple payloads. The required precision in any of these applications will vary, according to the requirements of the task and abilities of GPS to cope with the environment and the dynamics. This paper describes the post-mission reconstruction of the relative trajectories of four GPS receivers attached to four payloads jettisoned from a Black Brant XII rocket. This vehicle was launched by the National Aeronautics and Space Administration (NASA) in January 1999 from the Poker Flats Research Range near Fairbanks, Alaska. The Black Brant XII is a sub-orbital rocket designed to carry payloads of 100 to 500 kg into the upper atmosphere. Flight time is generally in the order of 10-20 minutes. In this experiment, a GPS receiver and antenna was attached to each of the four payloads. One of the GPS receivers was assigned as the "base station", while the other 3 receivers were designated as remotes. GPS time, code and phase measurements were telemetered to a ground station for real-time processing and storage. The object of the mission was to re-compute the position and velocity of the remote units with respect to the base station during the launch phase and after the payloads separated. During the launch segment the 3 baseling distances between the 4 antennas are known from plans and are constant values until each payload is released. On the fly ambiguity determination was used to establish local coordinates from the base antenna to each of the other 3 GPS units during flight. Distance computations were made from the GPS-derived coordinates and compared to plan distances. Using this methodology an error analysis of the relative GPS accuracies has been presented and in addition a description given of the respective payload behaviour following separation from the vehicle.

Martell, Hugh↗
NASA NTRS1993

Comparison of GPS and GLONASS common-view time transfers

It was already shown than even with a simple daily averaging of GLONASS data at each site, continental GLONASS time transfer can be achieved at a level of several tens of nanoseconds. A further step is to carry out observations of GLONASS satellites by the common-view method. A comparison of GPS and GLONASS common-view time transfers between Russia and Western Europe are reported. At each site, a GPS receiver and a GLONASS receiver are connected to the same atomic clock. Both GPS receivers are of NBS type and the GLONASS receivers are of type A-724. As GPS common-view time transfer between Sevres and Mendeleevo is accomplished at a level of a few nanoseconds in precision, it gives an excellent reference with which to evaluate the performance of GLONASS common-view time transfer.

Lewandowski, W.↗
NASA NTRS2001

Spaceborne Global Positioning System for Spacecraft

The spaceborne Global Positioning System receiver provides navigational solutions and is designed for use in low Earth orbit. The spaceborne GPS receiver can determine the orbital position of a spacecraft using any of the satellites wi thin the GPS constellation. It is a multiple processor system incorporating redundancy by using a microcontroller to handle the closure of tracking loops for acquired GPS satellites, while a separate microprocessor computes the spacecraft navigational solution and handles other tasks within the receiver. 'Me spaceborne GPS receiver can use either microcontroller or the microprocessor to close the satellite tracking loops. The use of microcontroller provides better tracking performance of acquired GPS satellites. The spaceborne GPS receiver utilizes up to seven separate GPS boards, with each board including its own set of correlators, down-converters and front-end components. The spaceborne GPS receiver also includes telemetry and time-marking circuitry. The spaceborne GPS receiver communicates with other spacecraft systems through a variety of interfaces and can be software-configured to support several different mission profiles.

Lamar F Dougherty↗
NASA NTRS2002

An assessment of the current WAAS algorithm in the South American region

In this paper, we use a network of 230 GPS receivers worldwide, each equipped with dual-frequency GPS receivers. We assessed the WAAS's planar fit algorithm in the equatorial region where the spatial gradients and the absolute slant TEC are known to be the highest in the world.

GPS total electron content ionosphere validation m↗
NASA NTRS1998

Ionospheric Signature of Surface Mine Blasts from Global Positioning System Measurements

Sources such as atmospheric or buried explosions and shallow earthquakes are known to produce infrasonic pressure waves in the atmosphere. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these acoustic and gravity waves induce variations of the ionospheric electron density. The Global Positioning System (GPS) provides a way of directly measuring the total electron content in the ionosphere and, therefore, of detecting such perturbations in the upper atmosphere. In July and August 1996, three large surface mine blasts (1.5 Kt each) were detonated at the Black Thunder coal mine in eastern Wyoming. As part of a seismic and acoustic monitoring- experiment, we deployed five dual-frequency GPS receivers at distances ranging from 50 to 200 km from the mine and were able to detect the ionospheric perturbation caused by the blasts. The perturbation starts 10 to 15 min after the blast, lasts for about 30 min, and propagates with an apparent horizontal velocity of 1200 meters per second. Its amplitude reaches 3 x 10 (exp 14) el per square meters in the 7-3 min period band, a value close to the ionospheric perturbation caused by the M = 6.7 Northridge earthquake. The small signal-to-noise ratio of the perturbation can be improved by slant-stacking the electron content time-series recorded by the different GPS receivers taking into account the horizontal propagation of the perturbation. The energy of the perturbation is concentrated in the 200 to 300 second period band, a result consistent with previous observations and numerical model predictions. The 300 second band probably corresponds to gravity modes and shorter periods to acoustic modes, respectively. Using a 1-D stratified velocity model of the atmosphere we show that linear acoustic ray tracing fits arrival times at all GPS receivers. We interpret the perturbation as a direct acoustic wave caused by the explosion itself. This study shows that even relatively small subsurface events can produce ionospheric perturbations that are above the detection threshold of the GPS technique. By sensing derivative signals, which can be detected over a relatively broad region, it appears that GPS might be particularly useful for source characterization within the first acoustic quiet zone where infrasound would probably be ineffective. This suggests that dual-frequency GPS monitoring could contribute to Comprehensive Nuclear Test Ban Treaty verification.

Calais, Eric↗
NASA NTRS1992

Appraisal of digital terrain elevation data for low-altitude flight

The use of terrain elevation databases in advanced guidance and navigation systems has greatly expanded. However, the limitations and accuracies of these databases must be considered and established prior to safe system flight evaluation. A simple approach to quantify reasonable flight limits is presented and evaluated for a helicopter guidance system dependent on a terrain database. The flight test evaluated involved a helicopter equipped with a Global Positioning System (GPS) receiver and radar altimeter, and a ground station GPS receiver which provided improved helicopter positioning. The precision navigation and radar altimeter data was acquired while flying low-altitude missions in south-central Pennsylvania. The aircraft-determined terrain elevations were compared with the terrain predicted by the Defense Mapping Agency (DMA) Level 1 terrain elevation data for the same area. The results suggest a safe set clearance altitude of 220 ft for flight testing of a DMA-based guidance avionic in the same area.

Zelenka, Richard E.↗