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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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NASA NTRS1994

Tracking strategies for laser ranging to multiple satellite targets

By the middle of the decade, several new Laser Geodynamic Satellites will be launched to join the current constellation comprised of the laser geodynamic satellite (LAGEOS) (US), Starlette (France), Ajisai (Japan), and Etalon I and II (USSR). The satellites to be launched, LAGEOS II and III (US & Italy), and Stella (France), will be injected into orbits that differ from the existing constellation so that geodetic and gravimetric quantities are sampled to enhance their resolution and accuracy. An examination of various possible tracking strategies adopted by the network of laser tracking stations has revealed that the recovery of precise geodetic parameters can be obtained over shorter intervals than is currently obtainable with the present constellation of satellites. This is particularly important in the planning of mobile laser tracking operations, given a network of permanently operating tracking sites. Through simulations, it is shown that laser tracking of certain satellite passes, pre-selected to provide optimal sky-coverage, provides the means to acquire a sufficient amount of data to allow the recovery of 1 cm station positions.

Robbins, J. W.↗

NASA NTRS2010

Orbital Debris Detection and Tracking Strategies for the NASA/AFRL Meter Class Autonomous Telescope (MCAT)

MCAT (Meter-Class Autonomous Telescope) is a 1.3m f/4 Ritchey-Chr tien on a double horseshoe equatorial mount that will be deployed in early 2011 to the western pacific island of Legan in the Kwajalein Atoll to perform orbital debris observations. MCAT will be capable of tracking earth orbital objects at all inclinations and at altitudes from 200 km to geosynchronous. MCAT s primary objective is the detection of new orbital debris in both low-inclination low-earth orbits (LEO) and at geosynchronous earth orbit (GEO). MCAT was thus designed with a fast focal ratio and a large unvignetted image circle able to accommodate a detector sized to yield a large field of view. The selected primary detector is a close-cycle cooled 4Kx4K 15um pixel CCD camera that yields a 0.9 degree diagonal field. For orbital debris detection in widely spaced angular rate regimes, the camera must offer low read-noise performance over a wide range of framing rates. MCAT s 4-port camera operates from 100 kHz to 1.5 MHz per port at 2 e- and 10 e- read noise respectively. This enables low-noise multi-second exposures for GEO observations as well as rapid (several frames per second) exposures for LEO. GEO observations will be performed using a counter-sidereal time delay integration (TDI) technique which NASA has used successfully in the past. For MCAT the GEO survey, detection, and follow-up prediction algorithms will be automated. These algorithms will be detailed herein. For LEO observations two methods will be employed. The first, Orbit Survey Mode (OSM), will scan specific orbital inclination and altitude regimes, detect new orbital debris objects against trailed background stars, and adjust the telescope track to follow the detected object. The second, Stare and Chase Mode (SCM), will perform a stare, then detect and track objects that enter the field of view which satisfy specific rate and brightness criteria. As with GEO, the LEO operational modes will be fully automated and will be described herein. The automation of photometric and astrometric processing (thus streamlining data collection for environmental modeling) will also be discussed.

Mulrooney, M.↗

NASA NTRS1990

Navigational utility of high-precision radio interferometer for Galileo's approach to Jupiter

The effect of very long baseline interferometry (VLBI) measurements of 2-nanoradian (nrad) accuracy has been studied for use in Galileo's approach to Jupiter's moon Io. Of particular interest is reducing the error in the minimum altitude above Io's surface. The nominal tracking strategy includes Doppler, range, and onboard optical data, in addition to VLBI data with 25-nrad accuracy. For nominal data, the altitude error is approximately 250 km with a data cutoff of 19 days before closest approach to Io. A limited number (two to four) of 2-nrad VLBI measurements, simulating a demonstration of improved VLBI data, were found to reduce the altitude error by 10 to 40 percent. Improving the accuracy of the VLBI measurements of the nominal tracking strategy to 2 nrads, to simulate the results from an operational few-nrad VLBI capability, was found to reduce the altitude error by an approximate factor of four. This reduction in altitude error is attributed to the ability that VLBI data give to help determine the along-track component of Jupiter's ephemeris. This capability complements the ability of the onboard optical data to determine the radial and cross-track components of Jupiter's ephemeris.

Folkner, W. M.↗

NASA NTRS1997

Steady-State Pursuit Is Driven by Object Motion Rather Than the Vector Average of Local Motions

We have previously shown that humans can pursue the motion of objects whose trajectories can be recovered only by spatio-temporal integration of local motion signals. We now explore the integration rule used to derive the target-motion signal driving pursuit. We measured the pursuit response of 4 observers (2 naive) to the motion of a line-figure diamond viewed through two vertical bar apertures (0.2 cd/square m). The comers were always occluded so that only four line segments (93 cd/square m) were visible behind the occluding foreground (38 cd/square m). The diamond was flattened (40 & 140 degree vertex angles) such that vector averaging of the local normal motions and vertical integration (e.g. IOC) yield very I or different predictions, analogous to using a Type II plaid. The diamond moved along Lissajous-figure trajectories (Ax = Ay = 2 degrees; TFx = 0.8 Hz; TFy = 0.4 Hz). We presented only 1.25 cycles and used 6 different randomly interleaved initial relative phases to minimize the role of predictive strategies. Observers were instructed to track the diamond and reported that its motion was always coherent (unlike type II plaids). Saccade-free portions of the horizontal and vertical eye-position traces sampled at 240 Hz were fit by separate sinusoids. Pursuit gain with respect to the diamond averaged 0.7 across subjects and directions. The ratio of the mean vertical to horizontal amplitude of the pursuit response was 1.7 +/- 0.7 averaged across subjects (1SD). This is close to the prediction of 1.0 from vertical motion-integration rules, but far from 7.7 predicted by vector averaging and infinity predicted by segment- or terminator-tracking strategies. Because there is no retinal motion which directly corresponds to the diamond's motion, steady-state pursuit of our "virtual" diamond is not closed-loop in the traditional sense. Thus, accurate pursuit is unlikely to result simply from local retinal negative feedback. We conclude that the signal driving steady-state pursuit is not the vector average of local motion signals, but rather a more vertical estimate of object motion, derived in extrastriate cortical areas beyond V1, perhaps NIT or MST.

Stone, Leland S.↗

NASA NTRS1988

Space Station Astrometric Telescope tracking for the detection of planetary systems

The paper presents a comprehensive star observation and tracking strategy, which uses a computer simulation of the Space Station orbital mechanics, system constraints, and Astrometric Telescope Facility (ATF) tracking maneuvers over a long observational period. This approach may be used to obtain data which may assist in the preliminary systems definition of the ATF. Results are given for an analysis which uses a restricted target set in order to demonstrate the disproportionate effect of the galactic-photon-rate index on the observation times for each star.

Mascy, Alfred C.↗

NASA NTRS1973

Orbit determination for low-thrust spacecraft: Concepts and analysis

Earth-based orbit determination capability for SEP spacecraft in multistation tracking and in thrust subsystem error modeling is described. Five different tracking strategies are applied to a 15 day segment of an Encke rendezvous mission. Both optimal and suboptimal orbit determination performance are determined for a wide range of process noise parameter values. The multi-station tracking techniques are found to be extremely effective, reducing orbit determination errors by orders of magnitude over that obtained with conventional single-station tracking. Explicitly differenced multistation data (QVLBI) is found to be least sensitive to gross modeling errors, but if a reasonably good process noise model is available, explicit differencing is not required.

Mcdanell, J. P.↗

NASA NTRS2022

Gravity Poppers: Hopping Probes for the Internal Mapping of Small Solar System Bodies

This paper presents the results of NIAC Phase I study into the feasibility of a novel mission architecture for highresolution gravity science on small Solar System bodies. The “Gravity Poppers” mission concept (see Fig. 1) consists of a swarm of small, minimalistic probes that are deployed from a mother spacecraft to the surface of a small body and which periodically and randomly hop around the surface. By tracking the ballistic sub-orbital trajectories of this hopping swarm, a very high resolution gravity field can be measured, which can then be used to answer a number of scientific questions of interest regarding the interior mass distribution of the body. This paper describes the three core focus areas of our study to demonstrate concept feasibility: (1) the design of hopping probes to be small, simple, robust, and “visible” to a distant spacecraft, (2) the tracking strategy for detecting and estimating the trajectories of a large number of ballistic probes, and (3) the algorithmic framework by which such measurements can be used to estimate the body’s gravity field. Our results suggest the ability to estimate the gravity field of a 500m asteroid beyond degree-and-order 40 through days to weeks of optical tracking of several LED-strobing probes, with a mass of only 200 g each. Collectively, this study demonstrates that the high-resolution gravity mapping of small body interiors is technically possible, economically feasible, and would enable a compelling set of science objectives aligned with NASA’s goals in planetary science, planetary defense, and future interests in resource prospecting.

McMahon, Jay↗

NASA NTRS2005

Response to MRO's end-to-end data accountability challenges

(MRO) on August 12, 2005. It carries six science instruments and three engineering payloads. Because MRO will produce an unprecedented number of science products, it will transmit a much higher data volume via high data rate than any other deep space mission to date. Keeping track of MRO products as well as relay products would be a daunting, expensive task without a well-planned data-product tracking strategy. To respond to this challenge, the MRO project developed the End-to- End Data Accountability System by utilizing existing information available from both ground and flight elements. Therefore, a capability to perform first-order problem diagnosis is essential in order for MRO to answer the questions, where is my data? and when will my data be available? This paper details the approaches taken, design and implementation of the tools, procedures and teams that track data products from the time they are predicted until they arrive in the hands of the end users.

data delivery status tracking↗

NASA NTRS2019

The ILRS: Approaching 20 Years and Planning for the Future

The International Laser Ranging Service (ILRS) was established by the International Association of Geodesy (IAG) in 1998 to support programs in geodesy, geophysics, fundamental constants and lunar research, and to provide the International Earth Rotation Service with data products that are essential to the maintenance and improvement in the International Terrestrial Reference Frame (ITRF), the basis for metric measurements of changes in the Earth and Earth–Moon system. Other scientific products derived from laser ranging include precise geocentric positions and motions of ground stations, satellite orbits, components of Earth’s gravity field and their temporal variations, Earth Orientation Parameters, precise lunar ephemerides and information about the internal structure of the Moon. Laser ranging systems are already measuring the one-way distance to remote optical receivers in space and are performing very accurate time transfer between remote sites in the Earth and in Space. The ILRS works closely with the IAG’s Global Geodetic Observing System. The ILRS develops (1) the standards and specifications necessary for product consistency, and (2) the priorities and tracking strategies required to maximize network efficiency. The service collects, merges, analyzes, archives and distributes satellite and lunar laser ranging data to satisfy a variety of scientific, engineering, and operational needs and encourages the application of new technologies to enhance the quality, quantity, and cost effectiveness of its data products. The ILRS works with (1) new satellite missions in the design and building of retroreflector targets to maximize data quality and quantity, and (2) science programs to optimize scientific data yield. Since its inception, the ILRS has grown to include forty laser ranging stations distributed around the world. The ILRS stations track more than ninety satellites from low Earth orbit (LEO) to the geosynchronous orbit altitude as well as retroreflector arrays on the surface of the Moon. Applications have been expanded to include time transfer, asynchronous ranging for targets at extended ranges, free space quantum telecommunications, and the tracking of space debris. Laser ranging technology is moving to lower energy, higher repetition rates (kHz), single-photon-sensitive detectors, shorter pulse widths, shorter normal point intervals for faster data acquisition, and increased pass interleaving, automated to autonomous operation with remote access, and embedded software for real-time updates and decision making. An example of pass interleaving is presented for the Yarragadee station (see Fig. 4); tracking of LEO satellites is often accommodated during break in LEO and GNSS passes. New satellites arrays provide more compact targets and work continues on the development of lighter less expensive arrays for satellites and the moon. The service now provides operational ITRF products including daily/ weekly station positions and daily resolution Earth orientation products; the flow of weekly combination of satellite orbit files for LAGEOS/Etalon-1 and -2 has recently been established. New products are under testing through a pilot project on systematic error monitoring currently underway. The article will give an overview of activities underway within the service, paths forward presently envisioned, and current issues and challenges.

Laser retroreflectors↗

NASA NTRS1975

Worst-error analysis of batch filter and sequential filter in navigation problems

This paper proposes a worst-error analysis for dealing with problems of estimation of spacecraft trajectories in deep space missions. Navigation filters in use assume either constant or stochastic (Markov) models for their estimated parameters. When the actual behavior of these parameters does not follow the pattern of the assumed model, the filters sometimes result in very poor performance. To prepare for such pathological cases, the worst errors of both batch and sequential filters are investigated based on the incremental sensitivity studies of these filters. By finding critical switching instances of non-gravitational accelerations, intensive tracking can be carried out around those instances. Also the worst errors in the target plane provide a measure in assignment of the propellant budget for trajectory corrections. Thus the worst-error study presents useful information as well as practical criteria in establishing the maneuver and tracking strategy of spacecraft's missions.

Nishimura, T.↗

NASA NTRS1977

On achieving sufficient dual station range accuracy for deep space navigation at zero declination

Since the Voyager Mission will encounter Saturn at a time when the planet will be nearly in the earth's equatorial plane, earth-based orbit determination will be more difficult than usual because of the so-called zero-declination singularity associated with conventional radiometric observations. Simulation studies show that in order to meet the required delivery accuracy at Saturn, a relative range measurement between the Goldstone and Canberra Deep Space Stations must be accurate to 4.5 times the square root of two meters. Topics discussed include the nature of error sources, the methodology and technology required for calibration, the verification process concerning the nearly simultaneous range capability, a description of the ranging system, and tracking strategy.

Siegel, H. L.↗

NASA NTRS1988

Determination of the Venus flyby orbits of the Soviet Vega probes using VLBI techniques

In December 1984, the Soviet Union launched two identical Vega spacecraft with the dual objective of exploring Venus and continuing to rendezvous with the comet Halley. The two Vega spacecraft encountered Venus in mid-June 1985 and successfully deployed entry probes and wind-measuring balloons into the Venus atmosphere. An objective of the Venus Balloon experiment was to measure the Venus winds using differential VLBI from the balloon and the flyby bus. NASA's Deep Space 64 meter subnet was part of a world wide network organized to collect data from the Vega probes and balloons. A critical element of this experiment was an accurate determination of the Venus relative flyby orbits of the Vega spacecraft during the 46 hour balloon lifetime. Venus flyby solutions were independently determined by the Soviets using two-way range and Doppler from Soviet stations and by JPL using one-way Doppler and VLBI data collected from the DSN. The Vega flyby solutions determined by the Soviets using a sparse two-way tracking strategy with JPL solutions using the DSN VLBI data to complement the Soviet data and with solutions using only one-way data collected by the DSN were compared.

Ellis, J.↗

NASA NTRS1992

Space debris measurement program at Phillips Laboratory

Ground-based optical sensing was identified as a technique for measuring space debris complementary to radar in the critical debris size range of 1 to 10 cm. The Phillips Laboratory is building a staring optical sensor for space debris measurement and considering search and track optical measurement at additional sites. The staring sensor is implemented in collaboration with Wright Laboratory using the 2.5 m telescope at Wright Patterson AFB, Dayton, Ohio. The search and track sensor is designed to detect and track orbital debris in tasked orbits. A progress report and a discussion of sensor performance and search and track strategies will be given.

Dao, Phan D.↗

NASA NTRS1993

AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pts. 1-6

Topics addressed include the prediction of helicopter component loads using neural networks, spacecraft on-orbit coupled loads analysis, hypersonic flutter of a curved shallow panel with aerodynamic heating, thermal-acoustic fatigue of ceramic matrix composite materials, transition elements based on transfinite interpolation, damage progression in stiffened composite panels, a direct treatment of min-max dynamic response optimization problems, and sources of helicopter rotor hub inplane shears. Also discussed are dynamics of a layered elastic system, confidence bounds on structural reliability, mixed triangular space-time finite elements, advanced transparency development for USAF aircraft, a low-velocity impact on a graphite/PEEK, an automated mode-tracking strategy, transonic flutter suppression by a passive flap, a nonlinear response of composite panels to random excitation, an optimal placement of elastic supports on a simply supported plate, a probabilistic assessment of composite structures, a model for mode I failure of laminated composites, a residual flexibility approach to multibody dynamics,and multilayer piezoelectric actuators.

Source record↗

NASA NTRS2003

Transonic Unsteady Aerodynamics of the F/A-18E at Conditions Promoting Abrupt Wing Stall

A transonic wind tunnel test of an 8% F/A-18E model was conducted in the NASA Langley Research Center (LaRC) 16-Foot Transonic Tunnel (16-Ft TT) to investigate the Abrupt Wing Stall (AWS) characteristics of this aircraft. During this test, both steady and unsteady measurements of balance loads, wing surface pressures, wing root bending moments, and outer wing accelerations were performed. The test was conducted with a wide range of model configurations and test conditions in an attempt to reproduce behavior indicative of the AWS phenomenon experienced on full-scale aircraft during flight tests. This paper focuses on the analysis of the unsteady data acquired during this test. Though the test apparatus was designed to be effectively rigid. model motions due to sting and balance flexibility were observed during the testing, particularly when the model was operating in the AWS flight regime. Correlation between observed aerodynamic frequencies and model structural frequencies are analyzed and presented. Significant shock motion and separated flow is observed as the aircraft pitches through the AWS region. A shock tracking strategy has been formulated to observe this phenomenon. Using this technique, the range of shock motion is readily determined as the aircraft encounters AWS conditions. Spectral analysis of the shock motion shows the frequencies at which the shock oscillates in the AWS region, and probability density function analysis of the shock location shows the propensity of the shock to take on a bi-stable and even tri-stable character in the AWS flight regime.

Schuster, David M.↗

NASA NTRS2008

Mars Reconnaissance Orbiter Navigation During the Primary Science Phase

The Mars Reconnaissance Orbiter began science operations in November 2006, with a suite of seven instruments and investigations, some of which required navigation accuracies much better than previous Mars missions. This paper describes the driving performance requirements levied on Navigation and how well those requirements have been met thus far. Trending analyses that have a direct impact on the Navigation performance, such as atmospheric bias determination, are covered in detail, as well as dynamic models, estimation strategy, tracking data reduction techniques, and residual noise.

MRO↗

NASA NTRS2018

Hi-5: A Potential High-Contrast Thermal Near-Infrared Imager for the VLTI

Hi-5 is a high-contrast (or high dynamic range) infrared imager project for the VLTI. Its main goal is to characterize young extra-solar planetary systems and exozodiacal dust around southern main-sequence stars. In this paper, we present an update of the project and key technology pathways to improve the contrast achieved by the VLTI. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 μm) and advanced fringe tracking strategies. We also address the strong exoplanet science case (young exoplanets, planet formation, and exozodiacal disks) offered by this wavelength regime as well as other possible science cases such as stellar physics (fundamental parameters and multiplicity) and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed.

exozodiacal dust↗

NASA NTRS2018

Smallsat Navigation via the Deep Space Network: Inner Solar Systems Missions

The space industry has seen an explosion in the number of operational SmallSats in Earth orbit, with a natural interest in extending SmallSat capabilities outside of low Earth orbit. As with larger missions, near-term deep-space SmallSats will rely on the Deep Space Network or similar facilities. Given the predicted growth in the number of deep space missions, effective use of DSN resources will be more critical than ever. Our investigation provides an initial survey of expected inner Solar System navigation performance for DSN radiometric data types, from two-way Doppler and ranging to one-way equivalents, including delta differential one-way range and alternative tracking strategies.

Wood, Lincoln J.↗