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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Range Filtering For Navigation By Satellite

Less processing and storage of data needed. Mathematical basis developed for Kalman filtering of sequential measurements of range from single-channel receiver in Global Positioning System (GPS) to each of several navigation satellites. Range filtering involves separate applications of kinematic Kalman tracking filter to measurements of signal from each satellite in use. State vector consists of pseudorange and time derivatives. Main advantages: simplification of tuning and decreases in required amounts of storage and processing of data for navigation in ships, airplanes, and ground vehicles.

Paielli, Russell↗
NASA NTRS2019

The Multi-GNSS Space Service Volume (SSV): USA ICG Support and Space User Applications

This introductory presentation discusses US contributions to the United Nations International Committee on Global Navigation Satellite Systems publication "The Interoperable Global Navigation Satellite Systems Space Service Volume", ST/SPACE/75, published November 2018. It covers US space user initiatives, lunar trajectory analysis results as performed for inclusion in the ST/SPACE/75 publication, and lunar trajectory analysis results post-publication.

Satellite navigation systems↗
NASA NTRS2017

In-Situ Navigation and Timing Services for the Human Mars Landing Site Part 1: System Concept

In [1] and [2], we introduce a new geometric trilateration method that simultaneously performs absolute positioning and relative positioning. The relative position is derived from a “differencing” function of two raw-range measurements between a known reference point and of the target from a navigation satellite, thereby eliminating most of the common errors like atmospheric delays, ephemeris errors, and instrument delays in real-time. In the Mars environment this “error-cancellation” function greatly reduces the need to perform extensive orbit determination (OD) of the navigation satellites like the Earth’s GPS, and only requires occasional tracks from the Earth’s large-aperture deep space antennas to perform OD’s. Leveraging on this scheme, we propose a low-cost, low-maintenance regional navigation satellite system architecture that provides in-situ navigation and timing services for robotic and human missions in the vicinity of a Mars landing site. This architecture is built upon the proposed Mars relay network infrastructure, and a number of notional Mars orbiting and surface missions in the human exploration era of Mars. We assume two areostationary Mars relay orbiters that have continuous line-of-sight visibility with the Mars landing site, a Deep Space Habitat (DSH) in an inclined 48-hour circular orbit, and a surface communication lander that could serve as the reference point. These orbiting and surface infrastructure elements broadcast GPS-like ranging signals and other ephemeris information to the mission users. With one or more additional orbiters in areosynchronous orbits that trace around a figure-8 path, a regional navigation satellite system can be realized that provides in-situ course absolute localization and precision relative localization and timing services to the users in the vicinity of a Mars landing site. This paper describes the system concept of the proposed Mars regional navigation satellite system.

Lee, Charles↗
NASA NTRS1985

Gravity, geoid and the oceanic lithosphere

Plate tectonics and its contribution to progress in studies of the Earth's gravitational field is discussed. In acquisition, the development of forced feedback accelerometers, satellite navigation, and satellite radar altimetry significantly improved the accuracy and coverage of gravity data over the oceans. In interpretation, gravity and geoid anomalies are used to determine information on the thermal and mechanical properties of the oceanic lithosphere and the forces that drive plate motions.

Watts, A. B.↗
NASA NTRS2017

Advantages and Limitations of L-Band Bistatic Radar Remote Sensing of Landscape Freeze/Thaw State

This paper presents results from recent satellite Global Navigation Satellite System-Reflectometry (GNSS-R) experiments in the northern high latitudes. Seasonal changes in the reflected signal are attributed to changes in the freeze/thaw state of the landscape. Here, we describe the unique geometries and sampling strategies that GNSS-R provide, which come with both advantages and limitations visà-vis traditional remote sensing techniques for monitoring the freeze/thaw transition. We will compare observational GNSSR data in the northern high latitudes with cotemporaneous Lband radiometer and radar data to highlight these advantages and limitations.

Chew, C.↗
NASA NTRS2018

The Multi-GNSS Space Service Volume

Global Navigation Satellite Systems (GNSS), now routinely used for navigation by spacecraft in low Earth orbit, are being used increasingly by high-altitude users in geostationary orbit and high eccentric orbits as well, near to and above the GNSS constellations themselves. Available signals in these regimes are very limited for any single GNSS constellation due to the weak signal strength, the blockage of signals by the Earth, and the limited number of satellites. But with the recent development of multiple GNSS constellations and ongoing upgrades to existing constellations, multi-GNSS signal availability is set to improve significantly. This will only be achieved if these signals are designed to be interoperable and are clearly documented and supported.All satellite navigation constellation providers are working together through the United Nations International Committee on GNSS (ICG) to establish an interoperable multi-GNSS Space Service Volume (SSV) for the benefit of all GNSS space users. The multi-GNSS SSV represents a common set of baseline definitions and assumptions for high-altitude service in space, documents the service provided by each constellation, and provides a framework for continued support for space users. This paper provides an overview of the GNSS SSV concept, development, status, and achievements within the ICG. It describes the final adopted definition and performance characteristics of the GNSS SSV, as well as the numerous benefits and use cases enabled by this development, and summarizes extensive technical analysis that was performed to illustrate these benefits in terms of signal availability, both on a global scale, and for multiple distinct mission types.

navigation↗
NASA NTRS1972

The role of time-frequency in satellite position determination systems.

Tests were conducted by NASA on radio navigation satellite systems that employ the use of time-frequency determination. The satellites used for this purpose were the ATS 1 and 3, and the Nimbus 3 and 4. Several systems were tested in order to examine the feasibility of three satellite navigation concepts: (1) multiple satellite range measurements, (2) satellite range rate, or range and range rate measurements and (3) satellite angle measurements. Test results indicate that locations of ships and aircraft can be determined to within 3-5 km, one sigma, by these satellite methods, and that location accuracy is both a function of the RF employed and of the extent of knowledge of the satellite orbit.

Ehrlich, E.↗
NASA NTRS2018

In-Situ Navigation and Timing Services for a Human Mars Landing Site Part 2: System Design and Simulations

In a previous paper, we described the system concept of a proposed Mars Regional Navigation Satellite System (MRNSS) that is built upon a number of notional Mars orbiting and surface missions in the human exploration era of Mars. We assume two areostationary Mars relay orbiters that have continuous line-of-sight visibility with the Mars landing site, a Deep Space Habitat (DSH) in an inclined 48-hour circular orbit, and a surface communication lander that could serve as the reference point. These orbiting and surface infrastructure elements broadcast GPS-like ranging signals and other ephemeris information to the mission users. With one or more additional orbiters in areosynchronous orbits that trace around a figure-8 path, a regional navigation satellite system can be realized that provides in-situ course absolute localization and precision relative localization and timing services to the users in the vicinity of a Mars landing site. We also introduced a new geometric trilateration method that simultaneously performs absolute positioning and relative positioning. The relative position is derived from a “differencing” function of two raw-range measurements between a known reference point and of the target from a navigation satellite, thereby eliminating most of the common errors like atmospheric delays, ephemeris errors, and instrument delays in real-time. In the Mars environment, this “error-cancellation” function greatly reduces the need to perform extensive orbit determination (OD) of the navigation satellites like the Earth’s GPS, and only requires occasional tracks from the Earth’s large-aperture deep space antennas to perform OD’s. In this paper, we provide detailed simulations on both the absolute positioning scheme and the relative positioning scheme, and show that the relative positioning scheme provides 200 – 400 times improvement in localization accuracy. On the ground side, we discuss new approaches that simultaneously perform 2-way Doppler/ranging, and re-introduce the method of Same Beam Interferometry (SBI) for the Mars navigation orbiters. This helps to further reduce the tracking burden of the ground antennas required to support the OD of the Mars orbiters, making the concept of MRNSS more realizable.

Lightsey, Glenn↗
NASA NTRS2020

Feasibility of “Weak GPS” Real-Time Positioning/Timing at Lunar Distance

There are multiple Global Navigation Satellite Systems (GNSS’s), comprising over 100 navigation satellites in the Earth’s medium and high orbits. Most of these satellites have antennas that point Nadir to earth, and transmit navigation signals so vehicles on Earth’s surface and in its vicinity can perform trilateration and estimate its 3-dimenional (3D) positioning. The sidelobes of these antennas can occasionally point to the Moon. It is postulated that a lunar vehicle carrying a large enough receiving antenna can occasionally detects and receives four or more sidelobes of these weak GNSS signals, thus enabling the vehicle to perform 3D positioning using an onboard GNSS receiver. We propagate the orbits of the GNSS satellites from United States’ Global Positioning Satellite (GPS) constellation, the Europe’s Galileo constellation, and the Russia’s GLONASS constellation, a total of 81 satellites. We simulate the visibility of these satellites by a lunar vehicle in a Near Rectilinear Halo Orbit (NRHO), based on the assumption that the lunar vehicle is “in-view” of a GNSS satellite as long as it falls within the 40- degree beam-width of the satellite. We also simulate the 3D positioning performance as a function of satellites’ ephemeris errors and pseudo-range errors. The preliminary results show that the lunar vehicle can “see” 5 – 13 satellites, and achieve a 3D positioning error (one-sigma) of 200 – 300 meters based on reasonable ephemeris and pseudo- range error assumptions. We also consider the case of using relative positioning to mitigate the GNSS satellites’ ephemeris biases. That is, by assuming a reference receiver with accurately known positioning that is close to the lunar vehicle, and computing the relative position of the lunar vehicle relative to the reference.

Cheung, Kar-Ming↗
NASA NTRS2018

Development of an Interoperable GNSS Space Service Volume

Global Navigation Satellite Systems (GNSS), now routinely used for navigation by spacecraft in low Earth orbit, are being used increasingly by high-altitude users in geostationary orbit and high eccentric orbits as well, near to and above the GNSS constellations themselves. Available signals in these regimes are very limited for any single GNSS constellation due to the weak signal strength, the blockage of signals by the Earth, and the limited number of satellites. But with the recent development of multiple GNSS constellations and ongoing upgrades to existing constellations, multi-GNSS signal availability is set to improve significantly. This will only be achieved if these signals are designed to be interoperable and are clearly documented and supported.All satellite navigation constellation providers are working together through the United Nations International Committee on GNSS (ICG) to establish an interoperable multi-GNSS Space Service Volume (SSV) for the benefit of all GNSS space users. The multi-GNSS SSV represents a common set of baseline definitions and assumptions for high-altitude service in space, documents the service provided by each constellation, and provides a framework for continued support for space users. This paper provides an overview of the GNSS SSV concept, development, status, and achievements within the ICG. It describes the final adopted definition and performance characteristics of the GNSS SSV, as well as the numerous benefits and use cases enabled by this development. Extensive technical analysis was also performed to illustrate these benefits in terms of signal availability, both on a global scale, and for multiple distinct mission types. This analysis is summarized here and presented in detail in a companion paper by Enderle, et al.

Positioning↗
NASA NTRS2018

Development of an Interoperable GNSS Space Service Volume

Global Navigation Satellite Systems (GNSS), now routinely used for navigation by spacecraft in low Earth orbit, are being used increasingly by high-altitude users in geostationary orbit and high eccentric orbits as well, near to and above the GNSS constellations themselves. Available signals in these regimes are very limited for any single GNSS constellation due to the weak signal strength, the blockage of signals by the Earth, and the limited number of satellites. But with the recent development of multiple GNSS constellations and ongoing upgrades to existing constellations, multi-GNSS signal availability is set to improve significantly. This will only be achieved if these signals are designed to be interoperable and are clearly documented and supported. All satellite navigation constellation providers are working together through the United Nations International Committee on GNSS (ICG) to establish an interoperable multi-GNSS Space Service Volume (SSV) for the benefit of all GNSS space users. The multi-GNSS SSV represents a common set of baseline definitions and assumptions for high-altitude service in space, documents the service provided by each constellation, and provides a framework for continued support for space users. This paper provides an overview of the GNSS SSV concept, development, status, and achievements within the ICG. It describes the final adopted definition and performance characteristics of the GNSS SSV, as well as the numerous benefits and use cases enabled by this development. Extensive technical analysis was also performed to illustrate these benefits in terms of signal availability, both on a global scale, and for multiple distinct mission types. This analysis is summarized here and presented in detail in a companion paper by Enderle, et al.

Parker, Joel J. K.↗
NASA NTRS2002

Relative Navigation of Formation Flying Satellites

The Guidance, Navigation, and Control Center (GNCC) at Goddard Space Flight Center (GSFC) has successfully developed high-accuracy autonomous satellite navigation systems using the National Aeronautics and Space Administration's (NASA's) space and ground communications systems and the Global Positioning System (GPS). In addition, an autonomous navigation system that uses celestial object sensor measurements is currently under development and has been successfully tested using real Sun and Earth horizon measurements.The GNCC has developed advanced spacecraft systems that provide autonomous navigation and control of formation flyers in near-Earth, high-Earth, and libration point orbits. To support this effort, the GNCC is assessing the relative navigation accuracy achievable for proposed formations using GPS, intersatellite crosslink, ground-to-satellite Doppler, and celestial object sensor measurements. This paper evaluates the performance of these relative navigation approaches for three proposed missions with two or more vehicles maintaining relatively tight formations. High-fidelity simulations were performed to quantify the absolute and relative navigation accuracy as a function of navigation algorithm and measurement type. Realistically-simulated measurements were processed using the extended Kalman filter implemented in the GPS Enhanced Inboard Navigation System (GEONS) flight software developed by GSFC GNCC. Solutions obtained by simultaneously estimating all satellites in the formation were compared with the results obtained using a simpler approach based on differencing independently estimated state vectors.

Long, Anne↗
NASA NTRS2003

Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System

A radio receiver system that features enhanced capabilities for remote sensing by use of reflected Global Positioning System (GPS) signals has been developed. This system was designed primarily for ocean altimetry, but can also be used for scatterometry and bistatic synthetic-aperture radar imaging. Moreover, it could readily be adapted to utilize navigation-satellite systems other than the GPS, including the Russian Global Navigation Satellite System GLONASS) and the proposed European Galileo system. This remote-sensing system offers both advantages and disadvantages over traditional radar altimeters: One advantage of GPS-reflection systems is that they cost less because there is no need to transmit signals. Another advantage is that there are more simultaneous measurement opportunities - one for each GPS satellite in view. The primary disadvantage is that in comparison with radar signals, GPS signals are weaker, necessitating larger antennas and/or longer observations. This GPS-reflection remote-sensing system was tested in aircraft and made to record and process both (1) signals coming directly from GPS satellites by means of an upward-looking antenna and (2) GPS signals reflected from the ground by means of a downward-looking antenna. In addition to performing conventional GPS processing, the system records raw signals for postprocessing as required.

Lowe, Stephen↗
NASA NTRS1975

Autonomous navigation for artificial satellites

An autonomous navigation system is considered that provides a satellite with sufficient numbers and types of sensors, as well as computational hardware and software, to enable it to track itself. Considered are attitude type sensors, meteorological cameras and scanners, one way Doppler, and image correlator.

Desai, P. S.↗
NASA NTRS2018

Exploring the Moon with GNSS: Applications of GNSS Within and Beyond the Space Service Volume

GNSS (Global Navigation Satellite Systems), long used by spacecraft in low Earth orbits, is now being used operationally by geostationary spacecraft. That use is expected to expand in the near future and even into higher orbits, thanks to work by the ICG (International Committee on Global Navigation Satellite Systems) and the service providers to formalize the GNSS Space Service Volume. Recent research has shown that GNSS navigation is possible even in lunar orbit, where it can benefit human and robotic exploration activities. This talk will focus on these emerging high-altitude applications of GNSS in cislunar space.

PNT↗