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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

LANDSAT-4 sensor performance

Preflight and in-orbit sensor and data measurements indicate that TM meets or exceeds most specifications. Measured spectral band edges meet instrument specifications in 12 out of 14 cases; there is ample dynamic range. The signal-to-noise ratio exceeds specifications, except for band 3, channel 4; and band 7 channel 7 is very noisy but still meets specifications. The modulation transfer function of channel 4, band 2, is smaller than specified. Registration errors between the primary focal plane (PFP) and the cold focal plane (CFP) are about 0.75 pixels along-scan and 0.2 pixels across scan. Forward and reverse scan discontinuities, are well within ground-processing capabilities to rectify. Instrument gain variability, up to 7% for band 5, requires use of the internal calibration (IC) system to assure radiometric accuracy. Preliminary applications evaluation of image contents indicates that TM provides much better definition of edges than MSS.

Barker, J. L.↗
NASA NTRS1982

APQ-102 imaging radar digital image quality study

A modified APQ-102 sidelooking radar collected synthetic aperture radar (SAR) data which was digitized and recorded on wideband magnetic tape. These tapes were then ground processed into computer compatible tapes (CCT's). The CCT's may then be processed into high resolution radar images by software on the CYBER computer.

Griffin, C. R.↗
NASA NTRS1984

Radiometric Accuracy Assessment of LANDSAT-4 Multispectral Scanner (MSS) Data

The LANDSAT-4 mission has unique characteristics relative to previous LANDSAT missions. The spacecraft is new; the orbit is lower with a more frequent repeat cycle; and the ground processing facility consists of new hardware with different algorithms being applied. How some of these changes affect the character of the radiometric data quality is explored. Banding effects; radiometric differences between LANDSAT 3 and 4; and the woodgrain pattern observed visually in the images are considered.

Alford, W. L.↗
NASA NTRS1984

Prelaunch absolute radiometric calibration of LANDSAT-4 protoflight Thematic Mapper

Results are summarized and analyzed from several prelaunch tests with a 122 cm integrating sphere used as part of the absolute radiometric calibration experiments for the protoflight TM sensor carried on the LANDSAT-4 satellite. The calibration procedure is presented and the radiometric sensitivity of the TM is assessed. The internal calibrator and dynamic range after calibration are considered. Tables show dynamic range after ground processing, spectral radiance to digital number and digital number to spectral radiance values for TM bands 1, 2, 3, 4, 5, 7 and for channel 4 of band 6.

Barker, J. L.↗
NASA NTRS1983

Landsat 4 results and their implications for agricultural surveys

Progress on defining the minimum Landsat-4 data characteristics needed for agricultural information in the U.S. and assessing the value-added capability of current technology to extract that level of information is reported. Emphasis is laid on the thematic mapper (TM) data and the ground processing facilities. TM data from all 7 bands for a rural Arkansas scene were examined in terms of radiometric, spatial, and geometric fidelity characteristics. Another scene sensed over Iowa was analyzed using three two-channel data sets. Although the TM data were an improvement over MSS data, no value differential was perceived. However, the development of further analysis techniques is still necessary to determine the actual worth of the improved sensor capabilities available with the TM, which actually has an MSS within itself.

Erickson, J. D.↗
NASA NTRS1982

Application of a recursive distortion estimator to the geodetic correction of thematic mapper imagery

It is pointed out that the higher resolution provided by the Thematic Mapper increases the demands on the accuracy needed by the ground processing in correcting for geodetic errors deriving from internal misalignments and uncertainties in the knowledge of spacecraft ephemeris and attitude. In addition, the Thematic Mapper will also process longer imagery intervals than previous missions. The recursive distortion estimator to be used is a Kalman filter. Here, a minimum variance spacecraft state error vector is estimated for known initial covariance of the elements of that vector and known image noise. Tests of the recursive distortion estimator with various spacecraft models carried out using a simulation of real world state vector dynamics are described. A determination is made of the density of control points needed to meet specified geometric correction requirements; it is expressed as a function of imagery interval length and control point measurement error.

Arnold, P.↗
NASA NTRS1984

An overview of the evolution of Landsat-4

Landsat-4 was launched on July 16, 1982, from Vandenberg Air Force Base in California. This launch culminated over a decade of planning, design, and implementation effort. During this period, many decisions and choices had to be made involving such items as the characteristics of the second-generation observing instrument named the Thematic Mapper (TM), the orbital altitude and coverage pattern, the configuration of the ground processing systems, etc. In total, the design and operation of Landsat-4 depart substantially from those of the successful Landsat 1, 2, and 3 series. Results derived from the operation of Landsat-4 systems and analyses of data products indicate that there have been very significant successes associated with Landsat-4. The TM provides observations that are considerably improved over the Multispectral Scanner (MSS). The middle-infrared bands at 1.6 and 2.2 micrometers, for example, are providing land-cover classification results that meet or exceed expectations. It is now hoped that successful operation of Landsat-4, Landsat-D' (D-prime), and the Tracking and Data Relay Satellite System (TDRSS) will permit the acquisition of a worldwide set of TM and MSS observations.

Salomonson, V. V.↗
NASA NTRS1984

Landsat-4 sensor performance

Preflight and in-orbit sensor and data measurements indicate that TM meets or exceeds most specifications. Measured spectral band edges meet instrument specifications in 12 out of 14 cases; there is ample dynamic range. The signal-to-noise ratio exceeds specifications, except for band 3, channel 4; and band 7 channel 7 is very noisy but still meets specifications. The modulation transfer function of channel 4, band 2, is smaller than specified. Registration errors between the primary focal plane (PFP) and the cold focal plane (CFP) are about 0.75 pixels along-scan and 0.2 pixels across scan. Forward and reverse scan discontinuities are well within ground-processing capabilities to rectify. Instrument gain variability, up to 7 percent for band 5, requires use of the internal calibration (IC) system to assure radiometric accuracy. Preliminary applications evaluation of image contents indicates that TM provides much better definition of edges than MSS.

Barker, J. L.↗
NASA NTRS1985

Payload transportation at KSC

Cargo ground processing at John F. Kennedy Space Center (KSC) involves either a horizointal or vertical mode of assembly and processing of the STS payloads. Consequently, cargos are commonly referred to as horizontal or vertical payloads. The process flow for each mode requires different facilities and transportation requirements. Occasionally, a mixed mission cargo containing both horizontal and vertical payload elements will require a combination of horizontal and vertical transportation between facilities. Some of the engineering challenges and innovative solutions to satisy the unique on-site payload transportation requirements at KSC. In particular, some of the more demanding design requirements of the multiuse mission support equipment are presented, and the resulting engineering designs and unique solutions are outlined.

Donahue, M. E.↗
NASA NTRS1985

An Analysis of the High Frequency Vibrations in Early Thematic Mapper Scenes

The motion of the mirrors in the thematic mapper (TM) and multispectral scanner (MSS) instruments, and the motion of other devices, such as the TDRSS antenna drive, and solar array drives onboard LANDSAT-4 cause vibrations to propagate through the spacecraft. These vibrations as well as nonlinearities in the scanning motion of the TM mirror can cause the TM detectors to point away from their nominal positions. Two computer programs, JITTER and SCDFT, were developed as part of the LANDSAT-D Assessment System (LAS), Products and Procedures Analysis (PAPA) program to evaluate the potential effect of high frequency vibrations on the final TM image. The maximum overlap and underlap which were observed for early TM scenes are well within specifications for the ground processing system. The cross scan and scan high frequency vibrations are also within the specifications cited for the flight system.

Kogut, J.↗
NASA NTRS1985

Thematic Mapper Data Quality and Performance Assessment in Renewable Resources/agriculture/remote Sensing

Analysis of the early thematic mapper (TM) data indicate the TM sensor and associated ground processing are performing equal to the high expectations and within advertised specifications. The overall TM system with improved resolution, together with additional and more optimumly placed spectral bands shows much promise for benefits in future analysis activities. By selecting man-made features of known dimensions (e.g., highways, airfields, buildings, and isolated water bodies), an assessment was made of the TM performance relative to the specified 30-meter (98-foot) resolution. The increase of spatial resolution of TM (30 m) over MSS (80 M) appears to be significant not only in resolving spectrally distinct classes that were previously undefinable but also in distinguishing within-field variability. An Important result of the early TM evaluation and pre-TM analyses was the development of an integrated system to receive LANDSAT-4 TM (as well as MSS) data and analyze the data via various approaches.

Bizzell, R. M.↗
NASA NTRS1985

Some experiences with botanical experiments in the orbiter middeck

The use of the Plant Growth Unit for botanical flight experiments on the STS-3 and 51-F flights is described. Inadequate temperature control on the STS-3 flight required a modification which eliminated the cooler night cycle on the 51-F flight. In-flight photography was added to the 51-F flight procedures because the postflight recovery period was sufficiently long to produce a gravity-induced bending in some plants. Ground processing at Dryden Flight Center was accomplished but improvements in the facilities available would be desirable.

Merek, E. L.↗
NASA NTRS1984

Spacelab Mission Implementation Cost Assessment (SMICA)

A total savings of approximately 20 percent is attainable if: (1) mission management and ground processing schedules are compressed; (2) the equipping, staffing, and operating of the Payload Operations Control Center is revised, and (3) methods of working with experiment developers are changed. The development of a new mission implementation technique, which includes mission definition, experiment development, and mission integration/operations, is examined. The Payload Operations Control Center is to relocate and utilize new computer equipment to produce cost savings. Methods of reducing costs by minimizing the Spacelab and payload processing time during pre- and post-mission operation at KSC are analyzed. The changes required to reduce costs in the analytical integration process are studied. The influence of time, requirements accountability, and risk on costs is discussed. Recommendation for cost reductions developed by the Spacelab Mission Implementation Cost Assessment study are listed.

Guynes, B. V.↗
NASA NTRS1986

Rarefied flow lift-to-drag measurements of the Shuttle Orbiter

This report presents a discussion of the analysis and the results of sensitive micro-g accelerometry measurements on the Shuttle Orbiter in the rarefied flow flight regime, that is, from altitudes of 60 km to 160 km. A brief description of the experimental apparatus called High Resolution Accelerometer Package (HiRAP) is given along with a description of the ground processing to obtain the lift-to-drag ratio (L/D) from the flight measurements. The flight results of L/D from six missions are presented and discussed. Comparisons are made with preflight wind tunnel data in the near continuum viscous interaction regime and preflight analytical estimates in the rarefied transition regime. Excellent agreement is obtained between flight and wind tunnel data in the viscous regime, but differences are noted between flight and preflight predictions in the transition regime. Free molecule flow F/D data are also obtained on each mission. Comparisons of flight data with classical theory show that complete diffuse reflection is not an appropriate model for rarefied aerodynamic coefficient calculations, and, for the Shuttle, some specular fraction is required. Surface reflection laws are explored to define the sensitivity of the L/D measurements to gas-surface molecule interactions.

Blanchard, R. C.↗
NASA NTRS1986

Radiometric calibration of the Shuttle Imaging Radar (SIR-C) system

The radiometric calibration accuracy of the Shuttle Imaging Radar (SIR-C) sensor is discussed. The analysis includes the antenna, RF electronics, the digital data handling system, the platform attitude control, attitude determination accuracy, and orbit effects. The radiometric distortion of the image products by the ground processing system used for the image formation is also considered. Since the SIR-C system is a dual-frequency quad-polarized system (i.e., 8 channels), the amplitude and phase error is considered over all possible operating modes and environments for absolute and relative (long-term and short-term) calibration within a channel and across channels.

Curlander, John C.↗
NASA NTRS1987

Development of the helium signature test for orbiter main propulsion system revalidation between flights

This paper presents the development of a test technique for revalidation of the Space Shuttle Orbiter Main Propulsion System during ground turnaround operations between flights of the Space Transportation System (STS). The Main Propulsion System consists of the three Space Shuttle Main Engines (SSME's) and the Main Propulsion System (MPS) connecting the SSME's to the orbiter/ground and orbiter/External Tank (ET) interfaces. The Helium Signature Test (HST) performs an end-to-end leak check of the MPS/SSME subsystems that serves as a final validation of those systems for reuse. The test was initially developed during the ground processing flow prior to the STS-6 launch of orbiter Challenger. The test was developed to fulfill a requirement for an overall subsystem leak check as a result of experience gained during the STS-6 Challenger Flight Readiness Firing (FRF) series, during which leaks were encountered in the SSME's that were not detected by routine fluid joint leak checks. The HST technique is described in detail, including orbiter and test equipment configuration, and compared to other leak detection methods used to revalidate MPS/SSME systems for reuse. The HST data base accumulated since STS-6 is summarized and future test applications are described.

Bilardo, Vincent J., Jr.↗
NASA NTRS1986

Contamination control of the space shuttle Orbiter crew compartment

Effective contamination control as applied to manned space flight environments is a discipline characterized and controlled by many parameters. An introduction is given to issues involving Orbiter crew compartment contamination control. An effective ground processing contamination control program is an essential building block to a successful shuttle mission. Personnel are required to don cleanroom-grade clothing ensembles before entering the crew compartment and follow cleanroom rules and regulations. Prior to crew compartment entry, materials and equipment must be checked by an orbiter integrity clerk stationed outside the white-room entrance for compliance to program requirements. Analysis and source identification of crew compartment debris studies have been going on for two years. The objective of these studies is to determine and identify particulate generating materials and activities in the crew compartment. Results show a wide spectrum of many different types of materials. When source identification is made, corrective action is implemented to minimize or curtail further contaminate generation.

Bartelson, Donald W.↗