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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 289 records · Page 16

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NASA NTRS1972

An H2-O2 auxiliary power unit for Space Shuttle.

Auxiliary power units operating on hydrogen and oxygen have the potential for significantly improved performance and payload for the Space Shuttle vehicles. In order to identify the technologies required for these units and to identify promising system configurations, contracted studies provided component and system-configuration screening analysis and detailed analysis of two preliminary system layouts. From these studies, Lewis Research Center has selected for further investigation a recuperated open-cycle hydrogen-oxygen turbine-driven APU concept with pressure-modulated reactant control. This paper discusses the reference system, the control mode, component arrangement, performance potential, and the technology program for this system.

Beremand, D. G.↗

NASA NTRS1990

Advanced Communications Technology Satellite (ACTS) and potential system applications

A description of the advanced communications technology satellite (ACTS) system is given with special emphasis on the communication characteristics. Potential satellite communications scenarios, including future operational ACTS-like satellite systems, are discussed. The description of the ACTS system updates previously published ACTS system references. Detailed information on items such as experimental ground stations is presented. The potential services can be generically described as voice, video, and data services. The implementation of these services on future operational ACTS-like systems can lead to unique quality, flexibility, and capacity characteristics at lower service costs. The specific service applications that could be supported range from low to high data rates and include both domestic and international applications.

Wright, David L.↗

NASA NTRS1970

A systems plan for an earth and ocean dynamics satellite applications program

A system for investigating phenomena associated with the earth's dynamical and crustal motions, and the sea surface is described. The proposed observing systems include the following facilities: (1) A network of fundamental stations, whose locations and motions, including polar, variations in the earth's rotational rate, and crustal motions, are determined by very long baseline interferometry, relative to the basic reference system of radio stars. The sites are all NASA Goddard stations with the exception of Kashima, Japan, a facility which has participated extensively in the ATS program. (2) A system of Geopause spacecraft in nearly circular polar orbits, normal to the ecliptic at a distance of about five earth radii with a period on the order of two thirds of a day.

Siry, J. W.↗

NASA NTRS2014

Maintaining Aura's Orbit Requirements While Performing Orbit Maintenance Maneuvers Containing an Orbit Normal Delta-V Component

The Earth Observing System (EOS) Afternoon Constellation consists of five member missions (GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura), each of which maintain a frozen, sun-synchronous orbit with a 16-day repeating ground track that follows the Worldwide Reference System-2 (WRS-2). Under nominal science operations for Aura, the propulsion system is oriented such that the resultant thrust vector is aligned 13.493 degrees away from the velocity vector along the yaw axis. When performing orbit maintenance maneuvers, the spacecraft performs a yaw slew to align the thrust vector in the appropriate direction. A new Drag Make Up (DMU) maneuver operations scheme has been implemented for Aura alleviating the need for the 13.493 degree yaw slew. The focus of this investigation is to assess the impact that no-slew DMU maneuver operations will have on Aura's Mean Local Time (MLT) which drives the required along track separation between Aura and the constellation members, as well as Aura's frozen orbit properties, eccentricity and argument of perigee. Seven maneuver strategies were analyzed to determine the best operational approach. A mirror pole strategy, with maneuvers alternating at the North and South poles, was implemented operationally to minimize impact to the MLT. Additional analysis determined that the mirror pole strategy could be further modified to include frozen orbit maneuvers and thus maintain both MLT and the frozen orbit properties under noslew operations.

Aqua↗

NASA NTRS2014

Maintaining Aura's Orbit Requirements Under New Maneuver Operations

The Earth Observing System (EOS) Afternoon Constellation consists of five member missions (GCOM-W1, Aqua, CALIPSO, CloudSat, and Aura), each of which maintain a frozen, sun-synchronous orbit with a 16-day repeating ground track that follows the Worldwide Reference System-2 (WRS-2). Under nominal science operations for Aura, the propulsion system is oriented such that the resultant thrust vector is aligned 13.493 degrees away from the velocity vector along the yaw axis. When performing orbit maintenance maneuvers, the spacecraft performs a yaw slew to align the thrust vector in the appropriate direction. A new Drag Make Up (DMU) maneuver operations scheme has been implemented for Aura alleviating the need for the 13.493 degree yaw slew. The focus of this investigation is to assess the impact that no-slew DMU maneuver operations will have on Auras Mean Local Time (MLT) which drives the required along track separation between Aura and the constellation members, as well as Auras frozen orbit properties, eccentricity and argument of perigee. Seven maneuver strategies were analyzed to determine the best operational approach. A mirror pole strategy, with maneuvers alternating at the North and South poles, was implemented operationally to minimize impact to the MLT. Additional analysis determined that the mirror pole strategy could be further modified to include frozen orbit maneuvers and thus maintain both MLT and the frozen orbit properties under no-slew operations

aura↗

NASA NTRS2015

Visual Stability of Objects and Environments Viewed through Head-Mounted Displays

Virtual Environments (aka Virtual Reality) is again catching the public imagination and a number of startups (e.g. Oculus) and even not-so-startup companies (e.g. Microsoft) are trying to develop display systems to capitalize on this renewed interest. All acknowledge that this time they will get it right by providing the required dynamic fidelity, visual quality, and interesting content for the concept of VR to take off and change the world in ways it failed to do so in past incarnations. Some of the surprisingly long historical background of the technology that the form of direct simulation that underlies virtual environment and augmented reality displays will be briefly reviewed. An example of a mid 1990's augmented reality display system with good dynamic performance from our lab will be used to illustrate some of the underlying phenomena and technology concerning visual stability of virtual environments and objects during movement. In conclusion some idealized performance characteristics for a reference system will be proposed. Interestingly, many systems more or less on the market now may actually meet many of these proposed technical requirements. This observation leads to the conclusion that the current success of the IT firms trying to commercialize the technology will depend on the hidden costs of using the systems as well as the development of interesting and compelling content.

virtual environment↗

NASA NTRS1980

High-power microwave optics for flexible power transmission systems

A large concave microwave mirror near the transmitter can magnify the apparent size of the Earth as seen from a phased array, and vice versa, permitting a small phased array to be coupled to a small rectenna while preserving the transmission efficiency (the reflection loss is slight) and peak power densities characteristic of the reference system. This augmentation of the phased array aperture with a large mirror gives the system greater resolution (in the optical sense), and opens new degrees of freedom in SPS design. The consequences of such an approach for a prototype satellite were explored. Its consequences for a mature SPS are discussed.

Drexler, K. E.↗

NASA NTRS2022

Development of LISA Laser System at NASA

NASA Goddard Space Flight Center (GSFC) is developing a master oscillator power amplifier (MOPA) laser transmitter for the Laser Interferometer Space Antenna (LISA) mission. The laser transmitter is one of the potential contributions to the LISA mission from NASA. Our development effort has included a master oscillator (MO), a power amplifier (PA), a frequency reference system (FRS), a power monitor detector (PMON), and laser electronics module (LEM). We are working on their design, performance evaluation, environmental testing, and reliability testing for space flight. We have built TRL 4 laser optical modules based on the MO and PA, which meets most performance requirements. One of the TRL 4 laser optical modules has been delivered to ESA for independent evaluation. TRL 6 versions of MO and PA are being built and evaluated at GSFC. TRL 5 and 6 versions of laser electronics are under development. In this paper, we will describe our progress to date and plans to demonstrate and deliver a TRL 6 laser demonstrator system to ESA by 2024.

LISA, Space Lasers↗

DOE OSTI2025

BCARS Simulated Phantom Dataset for Evaluation of Processing Pipelines

Broadband coherent anti-Stokes Raman scattering (BCARS) microscopy is a powerful label-free biological imaging technique, but the raw signal requires careful processing. The vibrationally resonant (Raman) fingerprint signal is usually small compared with instrumental noise sources and the nonresonant background (NRB) inherent in the BCARS signal. Fortunately, the NRB exhibits a systematic phase relationship with the coherent Raman response, acting as a heterodyne amplifier for the weak fingerprint signal. Due to this heterodyne effect, the Raman response can be recovered quantitatively and invariantly across different instruments, provided the NRB shape is known. Even with heterodyne amplification, the amplitudes of fingerprint signal components are often comparable to system noise. Singular value decomposition (SVD), which utilizes spatial information, is often employed for additional noise filtering. Consequently, finding optimal processing parameters to properly distinguish the NRB and Raman responses and suppress noise in the complex BCARS signal requires a reference system that realistically represents the spectral and spatial properties of BCARS signals obtained from biological samples. We present a digital tissue phantom that meets these criteria as a tool for testing candidate signal processing pipelines. The digital phantom is generated with simulated hyperspectral Raman images having system-specific noise and background characteristics. Here, we analyze phantom datasets with differing background and signal-to-noise conditions to evaluate their impact on the performance of multiple signal processing pipelines. Specifically, we investigate the application of a Butterworth filter-based routine to directly estimate the NRB from the BCARS signal. Additionally, we evaluate a Lorentzian wavelet transform as an alternative to the Hilbert transform for extracting the Raman spectrum from the BCARS signal. While we demonstrate this phantom for BCARS, it can be used for any spectroscopic Raman imaging approach.

Dixon, Jessica Z. [Georgia Institute of Technology↗

NASA NTRS1982

LANDSAT imagery: Description of products available from the CSIR Satellite Remote Sensing Centre

An overview of the LANDSAT system is provided along with information to assist prospective users in establishing whether imagery for their areas of interest is available and how to obtain such imagery. Spectral bands, spatial resolution, and digital data are explained as well as worldwide reference system indexing and the identification number assigned to images. The sizes and scales of standard black and white imagery and of false color composite imagery are listed. The format is given for computer compatible tapes and standard enhanced imagery is described. Other information available to users include LANDSAT index maps, catalogs of available imagery, a schedule of overpass dates, and a list of product prices.

Source record↗

NASA NTRS1978

Strapdown system redundancy management flight demonstration

The suitability of strapdown inertial systems in providing highly reliable short-term navigation for vertical take-off and landing (VTOL) aircraft operating in an intra-urban setting under all-weather conditions was assessed. A preliminary design configuration of a skewed sensor inertial reference system employing a redundancy management concept to achieve fail-operational, fail-operational performance, was developed.

Source record↗

NASA NTRS1994

SATS: Small, Automated Tracking System - - Elements of a Better System for Satellite Tracking and Telemetry

JPL has been exploring applications of precise Global Positioning System (GPS) techniques to navigation and data communication for Earth orbiting spacecraft. GPS tracking can be exploited in several different ways, depending on the orbital altitude of the spacecraft of interest, to support orbit and trajectory determination. At low-Earth orbits below 3000 km, 'upwards-looking' GPS tracking analogous to ground-based GPS tracking can be used to provide real-time orbit determination for navigation. At Earth orbiting altitudes between 3000 km and 8000 km, visibility of GPS rapidly decreases and it becomes advantageous to add a nadir pointing antenna in order to continuously see enough GPS signals to navigate an orbiter. For orbits above 8000 km, JPL has developed the GPS-like tracking (GLT) technique which dispenses with the on-board GPS receiver in favor of a transmitting beacon whose phase is tracked, simultaneously with normal GPS signals, by a ground network of 'enhanced' GPS receivers. The systems referred to above all have the potential to provide inexpensive and autonomous navigation/orbit production and, in some cases, integrated data communication for a wide class of Earth orbiters and should be of interest to designers of NASA, military, and commercial space systems.

GPS Global Positioning System navigation spacecraf↗

NASA NTRS1982

Antenna optimization of single beam microwave systems for the solar power satellite

A generalized antenna design technique is applied to the unique environmental requirements pertaining to solar power satellite (SPS) systems. Optimal illumination tapers and antenna/rectenna sizings are generated which allow increased transmit powers and lower electricity costs while minimizing sidelobe levels to meet a 0.01 mW/sq cm environmental standard. These optimal tapers also provide other advantages over the 10 dB Gaussian reference system.

Kerwin, E. M.↗

NASA NTRS2000

Initial Performance of the Attitude Control and Aspect Determination Subsystems on the Chandra Observatory

The aspect determination system of the Chandra X-ray Observatory plays a key role in realizing the full potential of Chandra's X-ray optics and detectors. We review the performance of the spacecraft hardware components and sub-systems, which provide information for both real time control of the attitude and attitude stability of the Chandra Observatory and also for more accurate post-facto attitude reconstruction. These flight components are comprised of the aspect camera (star tracker) and inertial reference units (gyros), plus the fiducial lights and fiducial transfer optics which provide an alignment null reference system for the science instruments and X-ray optics, together with associated thermal and structural components. Key performance measures will be presented for aspect camera focal plane data, gyro performance both during stable pointing and during maneuvers, alignment stability and mechanism repeatability.

Cameron, R.↗

NASA NTRS1997

Kinematic principles of primate rotational vestibulo-ocular reflex. II. Gravity-dependent modulation of primary eye position

The kinematic constraints of three-dimensional eye positions were investigated in rhesus monkeys during passive head and body rotations relative to gravity. We studied fast and slow phase components of the vestibulo-ocular reflex (VOR) elicited by constant-velocity yaw rotations and sinusoidal oscillations about an earth-horizontal axis. We found that the spatial orientation of both fast and slow phase eye positions could be described locally by a planar surface with torsional variation of <2.0 +/- 0.4 degrees (displacement planes) that systematically rotated and/or shifted relative to Listing's plane. In supine/prone positions, displacement planes pitched forward/backward; in left/right ear-down positions, displacement planes were parallel shifted along the positive/negative torsional axis. Dynamically changing primary eye positions were computed from displacement planes. Torsional and vertical components of primary eye position modulated as a sinusoidal function of head orientation in space. The torsional component was maximal in ear-down positions and approximately zero in supine/prone orientations. The opposite was observed for the vertical component. Modulation of the horizontal component of primary eye position exhibited a more complex dependence. In contrast to the torsional component, which was relatively independent of rotational speed, modulation of the vertical and horizontal components of primary position depended strongly on the speed of head rotation (i.e., on the frequency of oscillation of the gravity vector component): the faster the head rotated relative to gravity, the larger was the modulation. Corresponding results were obtained when a model based on a sinusoidal dependence of instantaneous displacement planes (and primary eye position) on head orientation relative to gravity was fitted to VOR fast phase positions. When VOR fast phase positions were expressed relative to primary eye position estimated from the model fits, they were confined approximately to a single plane with a small torsional standard deviation ( approximately 1.4-2.6 degrees). This reduced torsional variation was in contrast to the large torsional spread (well >10-15 degrees ) of fast phase positions when expressed relative to Listing's plane. We conclude that primary eye position depends dynamically on head orientation relative to space rather than being fixed to the head. It defines a gravity-dependent coordinate system relative to which the torsional variability of eye positions is minimized even when the head is moved passively and vestibulo-ocular reflexes are evoked. In this general sense, Listing's law is preserved with respect to an otolith-controlled reference system that is defined dynamically by gravity.

NASA Discipline Neuroscience↗

NASA NTRS1973

Coordinate systems and lunar observing station positions

Satellite geodesy has yielded the locations of more than fifty stations in a single coordinate system referred to the earth's center of mass with accuracies in the five to ten meter range. The different methods used at Goddard to accomplish this are described, and estimates of the accuracies of the satellite determinations are discussed. Theoretical aspects of coordinate systems associated with the earth and the moon are also considered.

Siry, J. W.↗

NASA NTRS1980

Environmental assessment for the satellite power system-concept development and evaluation program-microwave health and ecological effects

Potential health and ecological effects of the microwave beam from the microwave power transmission system (MPTS) of the satellite power system (SPS) are discussed. A detailed critical review of selected scientific articles from the published literature on the biological effects of nonionizing electromagnetic radiation is provided followed by an assessment of the possible effects of the SPS, based on exposure values for the reference system.

Source record↗

NASA NTRS1994

Global and regional kinematics from SLR stations

The stations of the Global Laser Tracking Network have significantly contributed to the measurement of plate kinematics. The expanding network of progressively improved instruments clearly demonstrates the systems' centimeter positioning accuracy. Several satellite laser ranging (SLR) analysis groups have adopted techniques to distill geodynamic information from the Lageos-1 satellite observations using orbital arc lengths from an hour to a decade. SLR observations now provide the scale for the International Terrestrial Reference System and help to define the Earth's polar motion in this system. Agreement between positions separately determined with SLR, VLBI and GPS systems has been established at the level of a few centimeters in position and a few millimeters per year in horizontal velocity.

Dunn, Peter J.↗