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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

X-38 Bolt Retractor Subsystem Separation Demonstration

The Flight Robotics Laboratory FRL successfully demonstrated the X-38 bolt retractor subsystem (BRS). The BRS design was proven safe by testing in the Pyrotechnic Shock Facility (PSI) before being demonstrated in the FRL. This Technical Memorandum describes the BRS, FRL, PSF, and interface hardware. Bolt retraction time, spacecraft simulator acceleration, and a force analysis are also presented. The purpose of the demonstration was to show the FRL capability for spacecraft separation testing using pyrotechnics. Although a formal test was not performed due to schedule and budget constraints, the data will show that the BRS is a successful design concept and the FRL is suitable for future separation tests.

Rugless, Fedoria↗
NASA NTRS1978

Initial ISEE magnetometer results - Magnetopause observations

Magnetic-field profiles across the magnetopause are examined which were obtained by the ISEE 1 and 2 spacecraft on four passes when the spacecraft separation was only a few hundred kilometers. The velocity of the magnetopause is found to be highly irregular, ranging from 4 to over 40 km/s and varying on a shorter time scale than required for a spacecraft to cross the boundary. The thickness of the magnetopause is estimated to range from 500 to over 1000 km. Clear evidence for field-line reconnection is discerned in data obtained when the magnetosheath field was southward. This evidence consists of flux-transfer events in which reconnection begins and ends on a time scale of minutes or less, leading to oscillations in the position of the magnetopause.

Russell, C. T.↗
NASA NTRS1982

Large-amplitude magnetic variations in quasi-parallel shocks - Correlation lengths measured by ISEE 1 and 2

Wide separations up to more than 1 earth radius between ISEE 1 and 2 during the second half of 1978 have been used to measure the correlation length of magnetic pulsations in quasiparallel shocks. When the two spacecraft were less than a few hundred km apart, magnetic oscillations measured by magnetometers on both spacecraft exhibited virtually identical waveforms, but at distances of several thousand km, the two time series of field variation showed no detailed similarily at all. The correlation coefficients of the pulsations dropped from close to 1.0 for spacecraft separations of less than 100 km to 0.2 for separations of greater than 800 km. A correlation length of several hundred km may be related to the gyroradius of return protons with energy typical of the peaks of diffuse and beam ion distributions.

Greenstadt, E. W.↗
NASA NTRS1993

Coherence lengths of upstream ULF waves - Dual ISEE observations

We have used high time resolution simultaneous magnetic field data from the dual ISEE spacecraft to study the coherence lengths of upstream ULF waves. We examine the cross-correlation between ISEE 1 and 2 observations for different spacecraft separations and determine the coherence lengths for upstream 30-second waves, 3-second waves, and one-Hz waves. We find that the observed coherence lengths are consistent with those estimated from the bandwidth of the spectral peak and that these lengths vary markedly from less than 100 km to over 1 R(E). In order to study all these wave phenomena, a multiple spacecraft mission such as the upcoming ESA Cluster mission would need to be capable of assuming a wide variety of possible separations.

Le, G.↗
NASA NTRS2004

Ka-Band Autonomous Formation Flying Sensor

Ka-band integrated range and bearing-angle formation sensor called the Autonomous Formation Flying (AFF) Sensor has been developed to enable deep-space formation flying of multiple spacecraft. The AFF Sensor concept is similar to that of the Global Positioning System (GPS), but the AFF Sensor would not use the GPS. The AFF Sensor would reside in radio transceivers and signal-processing subsystems aboard the formation-flying spacecraft. A version of the AFF Sensor has been developed for initial application to the two-spacecraft StarLight optical-interferometry mission, and several design investigations have been performed. From the prototype development, it has been concluded that the AFF Sensor can be expected to measure distances and directions with standard deviations of 2 cm and 1 arc minute, respectively, for spacecraft separations ranging up to about 1 km. It has also been concluded that it is necessary to optimize performance of the overall mission through design trade-offs among the performance of the AFF Sensor, the field of view of the AFF Sensor, the designs of the spacecraft and the scientific instruments that they will carry, the spacecraft maneuvers required for formation flying, and the design of a formation-control system.

Tien, Jeffrey↗
NASA NTRS2023

The Earth in Living Color - NASA’s Surface Biology and Geology Designated Observable

The Surface Biology and Geology (SBG) Designated Observable will transform our understanding of the global land surface, inland and coastal aquatic ecosystems through visible-to-shortwave infra-red imaging (VSWIR) spectroscopy and thermal infra-red (TIR) imaging. SBG is one of four high-priority observables recommended in the 2017 NASA Earth Science Decadal Survey t o address science questions on vegetation and aquatic ecosystem health, snow-cover dynamics, volcanic activity, and minerology. With a planned launch readiness date of 2028, SBG is currently in Pre-Phase A, with Level 1 requirements being developed for a two-spacecraft architecture, including an additional constellation pathfinder. The recommended architecture emerged from an extensive study (2018-2021) that engaged the research and applications community to consider the science questions and measurement objectives of the Decadal Survey. A Science and Applications Traceability Matrix was used as a basis for scoring candidate architectures, with inputs from four working groups that covered algorithms, applications, calibration and validation, and modeling. Two pathfinder studies, Modeling End-to-End Traceability in support of SBG (MEET-SBG) and Space-based Imaging Spectroscopy and Thermal pathfindER (SISTER) are providing pre-launch modeling tools and data for algorithm development to support science value trades. The architecture consists of one spacecraft hosting a wide-swath VSWIR imaging spectrometer providing 30-m ground-sample distance (GSD), a spectral range of 380-2500 nm (at 10 nm resolution), 16-day revisit with 400 signal-to-noise for VNIR and 250 for SWIR (at 25% reflectance). A separate spacecraft will host a wide swath thermal imager, with five to seven bands placed between 4-12 μm), with 60-m (GSD), 3- day revisit, and 0.2K noise-equivalent differential temperature (NeDT). A VNIR compact camera will be hosted on the TIR spacecraft to enable coincident TIR and VNIR observations. A constellation pathfinder will evaluate options for enabling VSWIR mission continuity using Small Sats or data buys. Partnerships with international space agencies contribute technology as well as improvements to temporal revisit. SBG, when launched, will be the first dedicated mission collecting the full spectra of the Earth’s ‘living color’ and will play a critical role in NASA’s Earth System Observatory.

David S Schimel↗
NASA NTRS2007

GPS-Based Precision Baseline Reconstruction for the TanDEM-X SAR-Formation

The TanDEM-X formation employs two separate spacecraft to collect interferometric Synthetic Aperture Radar (SAR) measurements over baselines of about 1 km. These will allow the generation ofa global Digital Elevation Model (DEM) with an relative vertical accuracy of 2-4 m and a 10 m ground resolution. As part of the ground processing, the separation of the SAR antennas at the time of each data take must be reconstructed with a 1 mm accuracy using measurements from two geodetic grade GPS receivers. The paper discusses the TanDEM-X mission as well as the methods employed for determining the interferometric baseline with utmost precision. Measurements collected during the close fly-by of the two GRACE satellites serve as a reference case to illustrate the processing concept, expected accuracy and quality control strategies.

Montenbruck, O.↗
NASA NTRS1998

Delta II Mars Pathfinder

Final preparations for lift off of the DELTA II Mars Pathfinder Rocket are shown. Activities include loading the liquid oxygen, completing the construction of the Rover, and placing the Rover into the Lander. After the countdown, important visual events include the launch of the Delta Rocket, burnout and separation of the three Solid Rocket Boosters, and the main engine cutoff. The cutoff of the main engine marks the beginning of the second stage engine. After the completion of the second stage, the third stage engine ignites and then cuts off. Once the third stage engine cuts off spacecraft separation occurs.

Source record↗
NASA NTRS2005

A Direct Method for Fuel Optimal Maneuvers of Distributed Spacecraft in Multiple Flight Regimes

We present a method to solve the impulsive minimum fuel maneuver problem for a distributed set of spacecraft. We develop the method assuming a non-linear dynamics model and parameterize the problem to allow the method to be applicable to multiple flight regimes including low-Earth orbits, highly-elliptic orbits (HEO), Lagrange point orbits, and interplanetary trajectories. Furthermore, the approach is not limited by the inter-spacecraft separation distances and is applicable to both small formations as well as large constellations. Semianalytical derivatives are derived for the changes in the total AV with respect to changes in the independent variables. We also apply a set of constraints to ensure that the fuel expenditure is equalized over the spacecraft in formation. We conclude with several examples and present optimal maneuver sequences for both a HE0 and libration point formation.

Hughes, Steven P.↗
NASA NTRS2017

Spacecraft Alignment Determination and Control for Dual Spacecraft Precision Formation Flying

Many proposed formation flying missions seek to advance the state of the art in spacecraft science imaging by utilizing precision dual spacecraft formation flying to enable a virtual space telescope. Using precision dual spacecraft alignment, very long focal lengths can be achieved by locating the optics on one spacecraft and the detector on the other. Proposed science missions include astrophysics concepts with spacecraft separations from 1000 km to 25,000 km, such as the Milli-Arc-Second Structure Imager (MASSIM) and the New Worlds Observer, and Heliophysics concepts for solar coronagraphs and X-ray imaging with smaller separations (50m 500m). All of these proposed missions require advances in guidance, navigation, and control (GNC) for precision formation flying. In particular, very precise astrometric alignment control and estimation is required for precise inertial pointing of the virtual space telescope to enable science imaging orders of magnitude better than can be achieved with conventional single spacecraft instruments. This work develops design architectures, algorithms, and performance analysis of proposed GNC systems for precision dual spacecraft astrometric alignment. These systems employ a variety of GNC sensors and actuators, including laser-based alignment and ranging systems, optical imaging sensors (e.g. guide star telescope), inertial measurement units (IMU), as well as micro-thruster and precision stabilized platforms. A comprehensive GNC performance analysis is given for Heliophysics dual spacecraft PFF imaging mission concept.

Formation flying↗
NASA NTRS2017

Spacecraft Alignment Determination and Control for Dual Spacecraft Precision Formation Flying

Many proposed formation flying missions seek to advance the state of the art in spacecraft science imaging by utilizing precision dual spacecraft formation flying to enable a virtual space telescope. Using precision dual spacecraft alignment, very long focal lengths can be achieved by locating the optics on one spacecraft and the detector on the other. Proposed science missions include astrophysics concepts with spacecraft separations from 1000 km to 25,000 km, such as the Milli-Arc-Second Structure Imager (MASSIM) and the New Worlds Observer, and Heliophysics concepts for solar coronagraphs and X-ray imaging with smaller separations (50m-500m). All of these proposed missions require advances in guidance, navigation, and control (GNC) for precision formation flying. In particular, very precise astrometric alignment control and estimation is required for precise inertial pointing of the virtual space telescope to enable science imaging orders of magnitude better than can be achieved with conventional single spacecraft instruments. This work develops design architectures, algorithms, and performance analysis of proposed GNC systems for precision dual spacecraft astrometric alignment. These systems employ a variety of GNC sensors and actuators, including laser-based alignment and ranging systems, optical imaging sensors (e.g. guide star telescope), inertial measurement units (IMU), as well as microthruster and precision stabilized platforms. A comprehensive GNC performance analysis is given for Heliophysics dual spacecraft PFF imaging mission concept.

Virtual Telescope↗
NASA NTRS2005

The Space Technology 7 disturbance reduction system

The NASA New Millennium Program Space Technology 7 (ST7) project was selected for the purpose of flight validation of technology for minimizing disturbances on spacecraft and freely-floating test masses. Measurements of the motion of test masses are used for determining the gravitational field in its location, providing information on the nearby mass distribution or looking gravitational waves generated by distant star systems. Any unmeasured forces acting on the test mass cause a deviation from a purely gravitational trajectory and so limit the accuracy of the gravity field estimation. The ST7 project will validate the capability to eliminate unwanted forces to a level 3000 times lower than the current state of the art. The ST7 design is based on the concept of a freely-floating test mass surrounded by a spacecraft which shields the test mass from unwanted disturbances. since some disturbance of the test mass can be caused by motion of the spacecraft itself with respect to the test mass, the disturbance reduction system includes the capability of precisely measuring the position of the spacecraft with respect to the test mass and control of the spacecraft position to within 1/100 of a wavelength of light.. The overall system performance of the ST7 project will be infused into space observatories for gravitational waves such as the Laser Interferometer Space Antenna project, and into future mission for mapping the time-variable Earth gravity field. The ST7 precision control capability also has applications for separated-spacecraft interferometric imaging projects. ST7 will consist of an instrument package and a set of microthrusters, which will be attached to the European Space Agency’s LISA Pathfinder spacecraft with launch scheduled for 2008.

Folkner, W. M.↗
NASA NTRS2017

Omnidirectional Inter-Satellite Optical Communicator (ISOC)

The objective of the Omnidirectional Inter-Satellite Optical Communicator (ISOC) project is to design a compact, lightweight,and energy efficient communicator module for use between satellites in space. This module will achieve continuous optical communication, with simultaneous data transmission and reception, at up to1 gigabit per second (Gbits) data rates for small spacecraft separated by up to 200 kilometers (kms). To achieve this goal,a data communicator with full spherical coverage field of view (FOV) needs to be designed. The proposed ISOC is a dodecahedron geometric array of chipscale, microelectromechanical systems (MEMS) based gimbal-less scanning mirrors that provide adjustable beam pointing and spherical FOV coverage for uninterrupted data transmission between several small spacecraft at arbitrary relative positions. This design eliminates known pointing issues and hence allows accurate direction of arrival calculations.Moreover, the proposed approach will enable data relaying between multiple satellites, and enable relative navigation control.

Inter-small satellite communication↗
NASA NTRS1981

Space shuttle launch era spacecraft injection errors and DSN initial acquisition

The initial acquisition of a spacecraft by the Deep Space Network (DSN) is a critical mission event. This results from the importance of rapidly evaluating the health and trajectory of a spacecraft in the event that immediate corrective action might be required. Further, the DSN initial acquisition is always complicated by the most extreme tracking rates of the mission. The DSN initial acquisition characteristics will change considerably in the upcoming space shuttle launch era. How given injection errors at spacecraft separation from the upper stage launch vehicle (carried into orbit by the space shuttle) impact the DSN initial acquisition, and how this information can be factored into injection accuracy requirements to be levied on the Space Transportation System (STS) is addressed. The approach developed begins with the DSN initial acquisition parameters, generates a covariance matrix, and maps this covariance matrix backward to the spacecraft injection, thereby greatly simplifying the task of levying accuracy requirements on the STS, by providing such requirements in a format both familiar and convenient to STS.

Khatib, A. R.↗
NASA NTRS2010

LISA and LISA Pathfinder: Gravitational Wave Observation in Space

The Laser Interferometer Space Antenna (LISA) is a planned NASA-ESA gravitational wave observatory in the frequency range of 0.1 mHz--100 mHz. This observation band is inaccessible to ground-based detectors due to fluctuations in the Earth gravitational field. Gravitational wave sources for LISA include galactic binaries, mergers of supermassive black-hole binaries, extreme-mass-ratio inspirals, and cosmology backgrounds and bursts. LISA is a constellation of three spacecraft separated by 5 million km in an equilateral triangle, whose center follows the Earth in a heliocentric orbit with an orbital phase offset of 20 degrees. Challenging technology is required to ensure pure geodetic trajectories of the six onboard test masses, whose distance fluctuations will be measured by interspacecraft laser interferometers with picometer accuracy. LISA Pathfinder is an ESA-launched technology demonstration mission of key LISA subsystems such as spacecraft control with micronewton thrusters, test mass drag-free control, and precision laser interferometry between free-flying test masses. Ground testing of hardware of the Gravitational Reference Sensor and Optical Metrology subsystems of LISA Pathfinder is currently ongoing. A detailed description of the two missions and an overview of current investigations conducted by the community will be discussed. The current status in development and implementation of LISA Pathfinder pre-flight systems and latest results of the ongoing ground testing efforts will also be presented.

Guzman, Felipe↗
NASA NTRS2010

Laser Interferometry for Gravitational Wave Observation: LISA and LISA Pathfinder

The Laser Interferometer Space Antenna (LISA) is a planned NASA-ESA gravitational wave observatory in the frequency range of 0.1mHz-100mHz. This observation band is inaccessible to ground-based detectors due to the large ground motions of the Earth. Gravitational wave sources for LISA include galactic binaries, mergers of supermasive black-hole binaries, extreme-mass-ratio inspirals, and possibly from as yet unimagined sources. LISA is a constellation of three spacecraft separated by 5 million km in an equilateral triangle, whose center follows the Earth in a heliocentric orbit with an orbital phase offset oF 20 degrees. Challenging technology is required to ensure pure geodetic trajectories of the six onboard test masses, whose distance fluctuations will be measured by interspacecraft laser interferometers with picometer accuracy. LISA Pathfinder is an ESA-launched technology demonstration mission of key LISA subsystems such us spacecraft control with micro-newton thrusters, test mass drag-free control, and precision laser interferometry between free-flying test masses. Ground testing of flight hardware of the Gravitational Reference Sensor and Optical Metrology subsystems of LISA Pathfinder is currently ongoing. An introduction to laser interferometric gravitational wave detection, ground-based observatories, and a detailed description of the two missions together with an overview of current investigations conducted by the community will bc discussed. The current status in development and implementation of LISA Pathfinder pre-flight systems and latest results of the ongoing ground testing efforts will also be presented

Guzman, Felipe↗
NASA NTRS2004

Relative Sensor with 4Pi Coverage for Formation Flying Missions

The Terrestrial Planet Finder (TPF) pre-project, an element of NASA s Origins program, is currently developing two architectures for a mission to search for earth-like planets around nearby stars. One of the architectures being developed is the Formation Flying Interferometer (FFI). The FFI is envisioned to consist of up to seven spacecraft (as many as six "collectors" with IR telescopes, and a "combiner") flying in precise formation within +/-1 cm of pre-determined trajectories for synchronized observations. The spacecraft-to-spacecraft separations are variable between 20 m and 100 m or more during observations to support various configurations of the interferometer in the planet-finding mode. The challenges involved with TPF autonomous operations, ranging from formation acquisition and formation maneuvering to high precision formation control during science observations, are unprecedented. In this paper we discuss the development of the formation acquisition sensor, which uses novel modulation and duplexing schemes to enable fast signal acquisition, multiple-spacecraft operation, and mitigation of inherent jamming conditions, while providing precise formation sensing and integrated radar capability. This approach performs delay synthesis and carrier cycle ambiguity resolution to improve range measurement, and uses differential carrier cycle ambiguity resolution to make precise bearing angle measurements without calibration maneuvers.

Tien, Jeffrey Y.↗
NASA NTRS2004

Relative Sensor with 4(pi) Coverage for Formation Flying Missions

The Terrestrial Planet Finder (TPF) pre-project, an element of NASA's Origins program, is currently developing two architectures for a mission to search for earth-like planets around nearby stars. One of the architectures being developed is the Formation Flying Interferometer (FFI). The FFI is envisioned to consist of up to seven spacecraft (as many as six 'collectors' with IR telescopes, and a 'combiner') flying in precise formation within f 1 cm of pre-determined trajectories for synchronized observations. The spacecraft-to-spacecraft separations are variable between 20 m and 100 m or more during observations to support various configurations of the interferometer in the planet-finding mode. The challenges involved with TPF autonomous operations, ranging from formation acquisition and formation maneuvering to high precision formation control during science observations, are unprecedented. In this paper we discuss the development of the formation acquisition sensor, which uses novel modulation and duplexing schemes to enable fast signal acquisition, multiple-spacecraft operation, and mitigation of inherent jamming conditions, while providing precise formation sensing and integrated radar capability. This approach performs delay synthesis and carrier cycle ambiguity resolution to improve range measurement, and uses differential carrier cycle ambiguity resolution to make precise bearing angle measurements without calibration maneuvers.

formation flying sensors↗