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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Citizen Explorer: An Earth Observer With New Small Satellite Technology - 1

Citizen Explorer-I (CX-I), designed and built by students at Colorado Space Grant Consortium in Boulder to provide global ozone monitoring, employs a unique mission architecture and several innovative technologies during its mission. The mission design allows K-12 schools around the world to be involved as ground stations available to receive science data and telemetry from CX-I. Another important technology allows the spacecraft to be less reliant on ground operators. Spacecraft Command Language (SCL) allows mission designers to set constraints on the satellite operations. The satellite then automatically adheres to the constraints when the satellite is out of contact with Mission Operations. In addition to SCL, a low level of artificial intelligence will be supplied to the spacecraft through the use of the Automated Scheduling and Planning ENvironment (ASPEN). ASPEN is used to maintain a spacecraft schedule in order to achieve the objectives a mission operator would normally have to complete. Within the communications system of CX-I, internet of CX-I, internet protocols are the main method for communicating with the satellite. As internet protocols have not been widely used in satellite communication, CX-I provides an opportunity to study the effectiveness of using internet protocols over radio links. The Attitude Determination and Control System (ADCS) on CX-I uses a gravity gradient boom as a means of orienting the satellite's science instruments toward nadir. The boom design is unique because it is constructed of tape measure material. These new technologies' effectiveness will be tested for use on future small satellite projects within the space satellite industry.

Allen, Zachary↗
NASA NTRS1999

Autonomous Navigation Using Celestial Objects

In the twenty-first century, National Aeronautics and Space Administration (NASA) Enterprises envision frequent low-cost missions to explore the solar system, observe the universe, and study our planet. Satellite autonomy is a key technology required to reduce satellite operating costs. The Guidance, Navigation, and Control Center (GNCC) at the Goddard Space Flight Center (GSFC) currently sponsors several initiatives associated with the development of advanced spacecraft systems to provide autonomous navigation and control. Autonomous navigation has the potential both to increase spacecraft navigation system performance and to reduce total mission cost. By eliminating the need for routine ground-based orbit determination and special tracking services, autonomous navigation can streamline spacecraft ground systems. Autonomous navigation products can be included in the science telemetry and forwarded directly to the scientific investigators. In addition, autonomous navigation products are available onboard to enable other autonomous capabilities, such as attitude control, maneuver planning and orbit control, and communications signal acquisition. Autonomous navigation is required to support advanced mission concepts such as satellite formation flying. GNCC has successfully developed high-accuracy autonomous navigation systems for near-Earth spacecraft using NASA's space and ground communications systems and the Global Positioning System (GPS). Recently, GNCC has expanded its autonomous navigation initiative to include satellite orbits that are beyond the regime in which use of GPS is possible. Currently, GNCC is assessing the feasibility of using standard spacecraft attitude sensors and communication components to provide autonomous navigation for missions including: libration point, gravity assist, high-Earth, and interplanetary orbits. The concept being evaluated uses a combination of star, Sun, and Earth sensor measurements along with forward-link Doppler measurements from the command link carrier to autonomously estimate the spacecraft's orbit and reference oscillator's frequency. To support autonomous attitude determination and control and maneuver planning and control, the orbit determination accuracy should be on the order of kilometers in position and centimeters per second in velocity. A less accurate solution (one hundred kilometers in position) could be used for acquisition purposes for command and science downloads. This paper provides performance results for both libration point orbiting and high Earth orbiting satellites as a function of sensor measurement accuracy, measurement types, measurement frequency, initial state errors, and dynamic modeling errors.

Folta, David↗
NASA NTRS2011

FPGA for Power Control of MSL Avionics

A PLGT FPGA (Field Programmable Gate Array) is included in the LCC (Load Control Card), GID (Guidance Interface & Drivers), TMC (Telemetry Multiplexer Card), and PFC (Pyro Firing Card) boards of the Mars Science Laboratory (MSL) spacecraft. (PLGT stands for PFC, LCC, GID, and TMC.) It provides the interface between the backside bus and the power drivers on these boards. The LCC drives power switches to switch power loads, and also relays. The GID drives the thrusters and latch valves, as well as having the star-tracker and Sun-sensor interface. The PFC drives pyros, and the TMC receives digital and analog telemetry. The FPGA is implemented both in Xilinx (Spartan 3- 400) and in Actel (RTSX72SU, ASX72S). The Xilinx Spartan 3 part is used for the breadboard, the Actel ASX part is used for the EM (Engineer Module), and the pin-compatible, radiation-hardened RTSX part is used for final EM and flight. The MSL spacecraft uses a FC (Flight Computer) to control power loads, relays, thrusters, latch valves, Sun-sensor, and star-tracker, and to read telemetry such as temperature. Commands are sent over a 1553 bus to the MREU (Multi-Mission System Architecture Platform Remote Engineering Unit). The MREU resends over a remote serial command bus c-bus to the LCC, GID TMC, and PFC. The MREU also sends out telemetry addresses via a remote serial telemetry address bus to the LCC, GID, TMC, and PFC, and the status is returned over the remote serial telemetry data bus.

Wang, Duo↗
NASA NTRS1991

GenSAA - Advancing satellite monitoring with expert systems

During numerous contacts with a satellite each day, spacecraft analysts must closely monitor real time data watching for combinations of telemetry parameter values, trends, and other indications that may signify a problem or failure. At the NASA Goddard Space Flight Center, fault-isolation expert systems are currently in operation supporting this data monitoring task. Based on the lessons learned during these initial efforts in expert system automation, a new domain-specific expert system development tool is being developed to facilitate the rapid development and reuse of real-time expert systems to serve as fault-isolation assistants for spacecraft analysts.

Hughes, Peter M.↗
NASA NTRS1991

Magellan mission planning and orbital operations

The goal of NASA's Magellan mission is to understand the geological and geophysical processes that have shaped the planet Venus. Through synthetic aperture radar, radiometric, altimetric, and gravity measurements, the scientific community hopes to improve its knowledge of the planet's topography and internal mass distribution. This paper provides an overview of the Magellan mission; describes the spacecraft sequence software design, development, and test; addresses the nominal operational flow of stored sequence design and generation; briefly describes the ground processing of engineering telemetry and imaging data; and then summarizes the Magellan operational experience with non-routine behavior of the spacecraft during the cruise and mapping portions of the prime mission.

Venus↗
NASA NTRS1993

More sense for less cents: Cost effective servicing of remote sensing satellites

This paper addresses the design considerations for Earth observation spacecraft bus and payload subsystems such that cost-effective spacecraft maintainability is enhanced through optimized reliability and the application of robotic on-orbit support. In the past, for most satellites, maintainability has been associated with the clever application of telemetry reconfiguration and the use of redundant systems as necessary over the life cycle of the spacecraft. This presentation addresses the opportunities and challenges of leveraging the extensive work already accomplished in the development of on-orbit servicing technologies.

Lee, Jeannie↗
NASA NTRS1963

The spacecraft antennas

The spacecraft employs two microwave antennas for communications and a single VHF antenna for telemetry, beacon, and command functions. One microwave antenna centered at 6 gc is used to receive broadband signals from a ground transmitter while the other microwave antenna centered at 4 gc is used to transmit signals to a ground receiver. Each microwave antenna is composed of a large number of circularly polarized radiating elements equally spaced around the equator of the spacecraft and connected to the electronic receiver and transmitter by a complex precision feed system. The VHF antenna is a small multi-element helix mounted at the pole of the spacecraft and radiates a linearly polarized signal. All antennas provide nearly isotropic antenna patterns with the axis of symmetry corresponding to the spin axis of the spacecraft. The antenna systems were constructed of light, but rugged, materials and passed extensive electrical, mechanical, and thermal tests.

ANTENNA↗
NASA NTRS2010

Determining Atmospheric-Density Profile of Titan

A method was developed for measuring the atmospheric density of Titan, the largest moon of Saturn, to create an accurate density profile as a function of altitude. This will allow mission planners to select safe flyby altitudes, and for navigation engineers to accurately predict the delta-v associated with those flybys. The spacecraft angular rate vector profile as a function of time is collected via telemetry from the onboard attitude estimator once every 2 seconds. The telemetry for thruster times, as a function of time, for eight Reaction Control System (RCS) thrusters is gathered, once a second, from the Propulsion Manager algorithm of the Cassini onboard attitude-control flight software. Using these data, the ground software computes the angular momentum vector profile and the per-axis external torque as a function of time imparted from the spacecraft only due to the atmospheric drag. The software can then determine the Titan atmospheric density profile as a function of time and altitude with the known values of spacecraft center of mass, the Titan-relative range and velocity data, the projected area, and the aerocenter, along with the estimated drag coefficient in a free molecular flow field.

Sarani, Siamak↗
NASA NTRS1995

The New Galileo Communication System

ave been developed to get as much data as possible from the Galileo spacecraft even without the high gain antenna. These methods include extensive data compression, a new packetized telemetry format, new error-correcting codes, new modulation, new ground receivers, and antenna arraying. (abstract only).

Galileo data compression spacecraft mission operat↗
NASA NTRS1993

AMFESYS: Modelling and diagnosis functions for operations support

Packetized telemetry, combined with low station coverage for close-earth satellites, may introduce new problems in presenting to the operator a clear picture of what the spacecraft is doing. A recent ESOC study has gone some way to show, by means of a practical demonstration, how the use of subsystem models combined with artificial intelligence techniques, within a real-time spacecraft control system (SCS), can help to overcome these problems. A spin-off from using these techniques can be an improvement in the reliability of the telemetry (TM) limit-checking function, as well as the telecommand verification function, of the Spacecraft Control systems (SCS). The problem and how it was addressed, including an overview of the 'AMF Expert System' prototype are described, and proposes further work which needs to be done to prove the concept. The Automatic Mirror Furnace is part of the payload of the European Retrievable Carrier (EURECA) spacecraft, which was launched in July 1992.

Wheadon, J.↗
NASA NTRS2008

Moving Away from Ones and Zeros, Designing a Ground Data System Based on Higher Levels of Abstraction

Previous JPL ground systems have been designed with the Ground Data System (GDS) engineer in mind. The focus on these systems has been on packaging and delivery of low level information (frames, packets, telemetry values) to the end user. It was not that long ago when project teams would be huddled over a workstation, examining crude displays of telemetry bits organized in various ways, trying to determine the status of a spacecraft. Understanding the data often required additional levels of GDS expertise, or worse, transformation of the raw data into alternative formats followed by ingestion into other tools so that the data became meaningful. The primary focus was often to answer these types of questions: "Why did this particular frame fail Reed-Solomon decode? Why did this packet get marked as invalid? Why am I missing a block of telemetry from my query?" -- which are completely valid questions to ask from a GDS Engineer's point of view, and large families of tools have been designed to help answer these questions. But these are not the questions that most users care about - which are more like: "Why is the battery state of charge trending down? Show me a summary image report for the last traverse to the target. Show me a data accountability summary for the last DSN pass." Answers to these questions, which are what users are looking for, requires a higher level of abstraction and supporting tools than mining through ones and zeros. JPL has created a next generation capability called the Mission Data Processing and Control System (MPCS) which is designed to support this higher level of abstraction by providing customizable views of the ground system combining collections of lower level information into more meaningful ways. Instead of examining frames, packets, and individual telemetry data points -- MPCS is capable of providing comprehensive summary reports, product status, overall flight/ground event status, as well as payload health summaries. Based on these higher level views, end users can make tactical or strategic decisions, or drop into detailed analysis as needed. System designers need to continue building systems that support low level GDS troubleshooting - but the basic design of a GDS should be geared towards what end users actually need to see. This paper will describe the capabilities of MPCS that directly support these higher levels of abstraction, and which are being used today in missions such as the Mars Science Laboratory and other NASA missions.

MPCS↗
NASA NTRS1972

OSO-7 orbiting solar observatory one year performance summary

The performance of the OSO-7 spacecraft during the first twelve months after launch is discussed. A summary description of the spacecraft and experiments is given. Line drawings of the satellite configuration, telemetry subsystem, electronics equipment, pneumatic equipment, and optical equipment are included.

Source record↗
NASA NTRS1975

Orbit and attitude state recoveries from Landmark data

The navigation of earth-referenced satellites with imaging data rather than, or in addition to, conventional radio tracking and attitude sensor telemetry is gaining increased popularity. Driving forces include a trend towards spacecraft autonomy, a need for timely and highly accurate griding information, and a growing awareness of the presence of high quality navigation information contained in such data. This paper describes the techniques used and the results obtained in an experiment to determine the orbit and attitude state of the geosynchronous SMS-1 spacecraft from Landmark observations extracted from earth images generated by the on-board Visible and Infrared Spin-Scan Radiometer (VISSR).

Fuchs, A. F.↗
NASA NTRS1975

Orbit and attitude state recoveries from Landmark data

The navigation of earth-referenced satellites with imaging data rather than, or in addition to, conventional radio tracking and attitude sensor telemetry is gaining increased popularity. Driving forces include a trend towards spacecraft autonomy, a need for timely and highly accurate gridding information, and a growing awareness of the presence of high quality navigation information contained in such data. This paper describes the techniques used and the results obtained in an experiment to determine the orbit and attitude state of the geosynchronous SMS-1 spacecraft from Landmark observations extracted from earth images generated by the on-board Visible and Infrared Spin-Scan Radiometer (VISSR).

Fuchs, A. F.↗
NASA NTRS1978

The Plasma Interaction Experiment (PIX) description and test program

The plasma interaction experiment (PIX) is a battery powered preprogrammed auxiliary payload on the LANDSAT-C launch. This experiment is part of a larger program to investigate space plasma interactions with spacecraft surfaces and components. The varying plasma densities encountered during available telemetry coverage periods are deemed sufficient to determine first order interactions between the space plasma environment and the biased experimental surfaces. The specific objectives of the PIX flight experiment are to measure the plasma coupling current and the negative voltage breakdown characteristics of a solar array segment and a gold plated steel disk. Measurements will be made over a range of surface voltages up to plus or minus kilovolt. The orbital environment will provide a range of plasma densities. The experimental surfaces will be voltage biased in a preprogrammed step sequence to optimize the data returned for each plasma region and for the available telemetry coverage.

Ignaczak, L. R.↗
NASA NTRS1978

The Plasma Interaction Experiment /PIX/ - Description and flight qualification test program

The Plasma Interaction Experiment (PIX) is a battery powered preprogrammed auxiliary payload on the Landsat-C launch. This experiment is part of a larger program to investigate space plasma interactions with spacecraft surfaces and components. The varying plasma densities encountered during available telemetry coverage periods are deemed sufficient to determine first order interactions between the space plasma environment and the biased experimental surfaces. The specific objectives of the PIX flight experiment are to measure the plasma coupling current and the negative voltage breakdown characteristics of a solar array segment and a gold plated steel disk. Measurements will be made over a range of surface voltages up to plus or minus 1 kilovolt. The orbital environment will provide a range of plasma densities. The experimental surfaces will be voltage-biased in a preprogrammed step sequence to optimize the data returned for each plasma region and for the available telemetry coverage.

Ignaczak, L. R.↗