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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

This interim report consists of four separate reports from our research on the receivers of NASA's Gravity And Magnetic Experiment Satellite (GAMES). The first report is entitled 'Analysis of phase estimation bias of GAMES receiver due to Doppler shift.' The second report is 'Background radiation on GAMES fine ranging detector from the moon, the planets, and the stars.' The third report is 'Background radiation on GAMES receivers from the ocean sun glitter and the direct sun.' The fourth report is 'GAMES receiver performance versus background radiation power on the detectors.'

Davidson, Frederic M.↗
NASA NTRS1995

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

Laser altimeters measure the time of flight of the laser pulses to determine the range of the target. The simplest altimeter receiver consists of a photodetector followed by a leading edge detector. A time interval unit (TIU) measures the time from the transmitted laser pulse to the leading edge of the received pulse as it crosses a preset threshold. However, the ranging error of this simple detection scheme depends on the received, pulse amplitude, pulse shape, and the threshold. In practice, the pulse shape and the amplitude are determined by the target target characteristics which has to be assumed unknown prior to the measurement. The ranging error can be improved if one also measures the pulse width and use the average of the leading and trailing edges (half pulse width) as the pulse arrival time. The ranging error becomes independent of the received pulse amplitude and the pulse width as long as the pulse shape is symmetric. The pulse width also gives the slope of the target. The ultimate detection scheme is to digitize the received waveform and calculate the centroid as the pulse arrival time. The centroid detection always gives unbiased measurement even for asymmetric pulses. In this report, we analyze the laser altimeter ranging errors for these three detection schemes using the Mars Orbital Laser Altimeter (MOLA) as an example.

Davidson, Frederic M.↗
NASA NTRS1996

Receiver design, performance analysis, and evaluation for space-borne laser altimeters and space-to-space laser ranging systems

We report here the design and the performance measurements of the breadboard receiver of the Geoscience Laser Altimeter System (GLAS). The measured ranging accuracy was better than 2 cm and 10 cm for 5 ns and 30 ns wide received laser pulses under the expected received signal level, which agreed well with the theoretical analysis. The measured receiver sensitivity or the link margin was also consistent with the theory. The effects of the waveform digitizer sample rate and resolution were also measured.

Davidson, Frederic M.↗
NASA NTRS2001

National Aeronautics and Space Administration Marshall Space Flight Center Space Transportation Directorate Risk Management Implementation Program

The US civil aerospace program has been a great contributor to the creation and implementation of techniques and methods to identify, analyze, and confront risk. NASA has accomplished mission success in many instances, but also has had many failures. Anomalies have kept the Agency from achieving success on other occasions, as well. While NASA has mastered ways to prevent risks, and to quickly and effectively react and recover from anomalies or failures, it was not until few years ago that a comprehensive Risk Management process started being implemented in some of its programs and projects. A Continuous Risk Management (CRM) cycle process was developed and has been promoted and used successfully in programs and projects across the Agency.

Duarte, Luis Alberto↗
NASA NTRS2021

Subcommittee on Space and Aeronautics Committee on Science, Space, and Technology: Statement by Dr. Gavin A. Schmidt Senior Advisor on Climate to the Administrator (Acting) National Aeronautics and Space Administration 117th Congress

NASA has long recognized that climate science and climate change are fundamental parts of our mandate, and for decades we have worked on fundamental and applied research in these areas. With the increasing evidence for serious impacts and the elevation of this topic by the Administration, it is time for a renewed focus on all the aspects of climate change that NASA works on and a commitment to ensure that the data and understanding that NASA has and will continue to accumulate will be used for the benefit of society.

Gavin A Schmidt↗
DOE OSTI2023

A Joint Roman Space Telescope and Rubin Observatory Synthetic Wide-Field Imaging Survey

We present and validate 20 deg(2) of overlapping synthetic imaging surveys representing the full depth of the Nancy Grace Roman Space Telescope High-Latitude Imaging Survey (HLIS) and 5 yr of observations of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). The two synthetic surveys are summarized, with reference to the existing 300 deg(2) of LSST simulated imaging produced as part of Dark Energy Science Collaboration (DESC) Data Challenge 2 (DC2). Both synthetic surveys observe the same simulated DESC DC2 universe. For the synthetic Roman survey, we simulate for the first time fully chromatic images along with the detailed physics of the Sensor Chip Assemblies derived from lab measurements using the flight detectors. The simulated imaging and resulting pixel-level measurements of photometric properties of objects span a wavelength range of similar to 0.3-2.0 mu m. We also describe updates to the Roman simulation pipeline, changes in how astrophysical objects are simulated relative to the original DC2 simulations, and the resulting simulated Roman data products. We use these simulations to explore the relative fraction of unrecognized blends in LSST images, finding that 20-30 per cent of objects identified in LSST images with i-band magnitudes brighter than 25 can be identified as multiple objects in Roman images. These simulations provide a unique testing ground for the development and validation of joint pixel-level analysis techniques of ground- and space-based imaging data sets in the second half of the 2020s - in particular the case of joint Roman-LSST analyses.

gravitational lensing↗
NASA NTRS1978

Statement of Doctor Noel Hinners, Associate Administrator for Space Sciences, National Aeronautics and Space Administration

Leadership in space exploration is an important part of the nation's prestige. There is a large science component in what are called applications and visa versa. Space science can provide the basis for some of the steps and bridges to possibilities envisioned for the year 2000 and forward. Both chemistry and physics are basis priorities in NASA missions and research activities. Current programs are concerned with developing the capability to put more weight in space, to provide for revisiting facilities such as the space telescope and provide for on-orbit repair or retrieval. Programs requiring the construction of facilities in space require higher levels of energy than those currently available. The prospective development of low-thrust propulsion in the 1980's will reduce transportation time. Data from Skylab and that to be obtained from Spacelab as well as investigations of solar-terrestrial interactions will benefit space tourists and inhabitants.

Hinners, N.↗
NASA NTRS1980

Space Operations Center - Next goal for manned space flight

The paper discusses the concept of the Space Operations Center, a Shuttle-serviced permanent manned LEO space station. The SOC has the mission-oriented role of construction, assembly, and servicing of space systems and spacecraft. Previous space-station concepts are reviewed; future space goals are compared; and objectives for the future Space Operations Center and its initial analysis are described.

Covington, C.↗
NASA NTRS1985

Space test program of high-voltage solar array-space plasma interactions

Future spacecraft, notably the proposed Space Station, will require power systems much larger than have previously been flown. It is recognized that at higher voltages, and at the relatively high plasma density present at low Earth orbital altitudes, undesirable interactions between the high voltage solar array and the space plasma will occur. Space experiments on high voltage solar array space plasma interactions in low Earth orbit are an absolute requirement for confident design of a higher voltage solar array. Experiments are presently being identified to provide the necessary space data for calibration of ground testing, validation of analytical models, and development of design guidelines required for confident design of high voltage solar arrays in space. A proposed flight experiment program which is designed to obtain the required data is summarized.

Carruth, M. R., Jr.↗
NASA NTRS1984

The Space Station - Mankind's permanent presence in space

The present discussion is concerned with developments which led finally to the announcement of a new U.S. national commitment in January 1984. According to this announcement, plans are to be developed for the establishment of a permanently manned orbiting Space Station to be deployed within the decade. Early concepts regarding a space station go back to 1869, when a story was published in the 'Atlantic Monthly' about a large earth-orbiting sphere, built of brick, in which people lived and worked. Some decades later, the idea was taken up by Oberth in Germany and Tsiolkovsky in Russia. Their work had a decisive influence on Goddard in the U.S. and von Braun in Germany, who developed basic propulsion systems. Attention is given to rocket developments during and after the Second World War, the trip to the moon, the post-Apollo program, the Space Shuttle and the 1970's, planning for the Space Station, opposition to the Space Station, the Space Station debate, international and commercial interest, and the President's decision.

Mark, H.↗
NASA NTRS1986

Methodology of design and analysis of external walls of space station for hypervelocity impacts by meteoroids and space debris

The development of criteria and methodology for the design and analysis of Space Station wall elements for collisions with meteoroids and space debris at hypervelocities is discussed. These collisions will occur at velocities of 10 km/s or more and can be damaging to the external wall elements of the Space Station. The wall elements need to be designed to protect the pressurized modules of the Space Station from functional or structural failure due to these collisions at hypervelocities for a given environment and population of meteoroids and space debris. The design and analysis approach and the associated computer program presented is to achieve this objective, including the optimization of the design for a required overall probability of no penetration. The approach is based on the presently available experimental and actual data on meteoroids and space debris flux and damage assessments and the empirical relationships resulting from the hypervelocity impact studies in laboratories.

Batla, F. A.↗