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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Residual Gas Analyzer Calibration

A technique which employs known gas mixtures to calibrate the residual gas analyzer (RGA) is described. The mass spectra from the RGA are recorded for each gas mixture. This mass spectra data and the mixture composition data each form a matrix. From the two matrices the calibration matrix may be computed. The matrix mathematics requires the number of calibration gas mixtures be equal to or greater than the number of gases included in the calibration. This technique was evaluated using a mathematical model of an RGA to generate the mass spectra. This model included shot noise errors in the mass spectra. Errors in the gas concentrations were also included in the valuation. The effects of these errors was studied by varying their magnitudes and comparing the resulting calibrations. Several methods of evaluating an actual calibration are presented. The effects of the number of gases in then, the composition of the calibration mixture, and the number of mixtures used are discussed.

R H Lilienkamp↗
NASA NTRS1973

Apollo experience report: Flight instrumentation calibration

Three types of instrumentation-calibration data were used in the Apollo Program to provide the correct engineering data for tests and mission support. The command and service module instrumentation-component procurement specifications required individual-component calibration, and calibration data for these individual components (conventional-calibration data) were always used for mission data support. A mean standard type of calibration data derived from a statistical sampling of conventional-calibration data was used for test and checkout during the latter part of the Apollo Program. The lunar module instrumentation procurement specification permitted the use of standard-calibration data. These data were applicable to similarly instrumented measurements. The definition, merit, and application of each type of data are discussed.

Demoss, J. F.↗
NASA NTRS1983

The calibration and flight test performance of the space shuttle orbiter air data system

The Space Shuttle air data system (ADS) is used by the guidance, navigation and control system (GN&C) to guide the vehicle to a safe landing. In addition, postflight aerodynamic analysis requires a precise knowledge of flight conditions. Since the orbiter is essentially an unpowered vehicle, the conventional methods of obtaining the ADS calibration were not available; therefore, the calibration was derived using a unique and extensive wind tunnel test program. This test program included subsonic tests with a 0.36-scale orbiter model, transonic and supersonic tests with a smaller 0.2-scale model, and numerous ADS probe-alone tests. The wind tunnel calibration was further refined with subsonic results from the approach and landing test (ALT) program, thus producing the ADS calibration for the orbital flight test (OFT) program. The calibration of the Space Shuttle ADS and its performance during flight are discussed in this paper. A brief description of the system is followed by a discussion of the calibration methodology, and then by a review of the wind tunnel and flight test programs. Finally, the flight results are presented, including an evaluation of the system performance for on-board systems use and a description of the calibration refinements developed to provide the best possible air data for postflight analysis work.

Dean, A. S.↗
NASA NTRS1984

Prelaunch absolute radiometric calibration of the reflective bands on the LANDSAT-4 protoflight Thematic Mapper

The results of the absolute radiometric calibration of the LANDSAT 4 thematic mapper, as determined during pre-launch tests with a 122 cm integrating sphere, are presented. Detailed results for the best calibration of the protoflight TM are given, as well as summaries of other tests performed on the sensor. The dynamic range of the TM is within a few per cent of that required in all bands, except bands 1 and 3. Three detectors failed to pass the minimum SNR specified for their respective bands: band 5, channel 3 (dead), band 2, and channels 2 and 4 (noisy or slow response). Estimates of the absolute calibration accuracy for the TM show that the detectors are typically calibrated to 5% absolute error for the reflective bands; 10% full-scale accuracy was specified. Ten tests performed to transfer the detector absolute calibration to the internal calibrator show a 5% range at full scale in the transfer calibration; however, in two cases band 5 showed a 10% and a 7% difference.

Barker, J. L.↗
NASA NTRS1985

Verification of L-band SAR calibration

Absolute calibration of a digital L-band SAR system to an accuracy of better than 3 dB has been verified. This was accomplished with a calibration signal generator that produces the phase history of a point target. This signal relates calibration values to various SAR data sets. Values of radar cross-section (RCS) of reference reflectors were obtained using a derived calibration relationship for the L-band channel on the ERIM/CCRS X-C-L SAR system. Calibrated RCS values were compared to known RCS values of each reference reflector for verification and to obtain an error estimate. The calibration was based on the radar response to 21 calibrated reference reflectors.

Larson, R. W.↗
NASA NTRS1986

A miniature remote deadweight calibrator

A miniature, computer-controlled, deadweight calibrator was developed to remotely calibrate a force transducer mounted in a cryogenic chamber. This simple mechanism allows automatic loading and unloading of deadweights placed onto a skin friction balance during calibrations. Equipment for the calibrator includes a specially designed set of five interlocking 200-milligram weights, a motorized lifting platform, and a controller box taking commands from a microcomputer on an IEEE interface. The computer is also used to record and reduce the calibration data and control other calibration parameters. The full-scale load for this device is 1,000 milligrams; however, the concept can be extended to accommodate other calibration ranges.

Supplee, Frank H., Jr.↗
NASA NTRS1988

Effects of switch leakages upon Nimbus-7 SMMR calibration

A calibration model for the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) is studied. This model not only removes major drawbacks of the current calibration model but also helps us understand the performance degradation of the aging instrument. The current Nimbus-7 SMMR calibration algorithm was derived without considering the interference effect between the two orthogonally polarized signals merging at a ferrite polarization selector switch. The resulting calibrated brightness temperatures, considered as a function of scan angle phi, are not symmetric around phi=0. However, neither the origin of the asymmetry nor the manner in which the two orthogonal components are mixed is fully understood. The proposed calibration model incorporates all the leakage factors associated with the ferrite switches along the signal paths. The resulting calibration equations clarify how the orthogonal components of surface brightness are coupled at radiometers. As a consequence, the origin of the asymmetry is clearly identified and explained. In addition, the feasibility of absolute calibration using in-orbit data is discussed.

Han, Daesoo↗
NASA NTRS1988

The absolute radiometric calibration of the advanced very high resolution radiometer

An increasing number of remote sensing investigations require radiometrically calibrated imagery from NOAA Advanced Very High Resolution Radiation (AVHRR) sensors. Although a prelaunch calibration is done for these sensors, there is no capability for monitoring any changes in the in-flight absolute calibration for the visible and near infrared spectral channels. Hence, the possibility of using the reflectance-based method developed at White Sands for in-orbit calibration of LANDSAT Thematic Mapper (TM) and SPOT Haute Resolution Visible (HVR) data to calibrate the AVHRR sensor was investigated. Three diffrent approaches were considered: Method 1 - ground and atmospheric measurements and reference to another calibrated satellite sensor; Method 2 - ground and atmospheric measurements with no reference to another sensor; and Method 3 - no ground and atmospheric measurements but reference to another satellite sensor. The purpose is to describe an investigation on the use of Method 2 to calibrate NOAA-9 AVHRR channels 1 and 2 with the help of ground and atmospheric measurements at Rogers (dry) Lake, Edwards Air Force Base (EAFB) in the Mojave desert of California.

Slater, P. N.↗
NASA NTRS1988

NASA Aircraft-Satellite Instrument Calibration Project

Ground based prelaunch calibration of satellite instruments usually is not adequate to provide an accurate characterization of the in-orbit performance of a satellite instrument. This is because the ground calibrations may not simulate the in-orbit environment observations of the satellite sensor, or because the sensor characteristics have changed during launch and in-orbit operations. One technique to obtain a meaningful in-orbit calibration of satellite sensors is to acquire simultaneous observations of an Earth scene with the satellite and a well calibrated aircraft or shuttle sensor which has similar characteristics to the satellite sensor. This is a direct in-orbit calibration technique and is usually called vicarious calibration. The experiment with the control instrument must occur above the sensible atmosphere as measured by the satellite sensor to provide a useful improvement to the calibration of the satellite sensor. Some observations on the experiments are made.

Guenther, B. W.↗
NASA NTRS1989

On-orbit Metrology and Calibration Requirements for Space Station Activities Definition Study

The Space Station is the focal point for the commercial development of space. The long term routine operation of the Space Station and the conduct of future commercial activities suggests the need for in-space metrology capabilities analogous when possible to those on-Earth. The ability to perform periodic calibrations and measurements with proper traceability is imperative for the routine operation of the Space Station. An initial review, however, indicated a paucity of data related to metrology and calibration requirements for in-space operations. This condition probably exists because of the highly developmental aspect of space activities to date, their short duration, and nonroutine nature. The on-orbit metrology and calibration needs of the Space Station were examined and assessed. In order to achieve this goal, the following tasks were performed: an up-to-date literature review; identification of on-orbit calibration techniques; identification of sensor calibration requirements; identification of calibration equipment requirements; definition of traceability requirements; preparation of technology development plans; and preparation of the final report. Significant information and major highlights pertaining to each task is presented. In addition, some general (generic) conclusions/observations and recommendations that are pertinent to the overall in-space metrology and calibration activities are presented.

Cotty, G. M.↗
NASA NTRS1988

Effects of switch leakages upon Nimbus-7 SMMR calibration

A calibration model for the Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) is studied. This model not only removes major drawbacks of the current calibration model but also helps in the understanding of the performance degradation of the aging instrument. The current Nimbus 7 SMMR calibration algorithm was derived without considering the interference effect between the two orthogonally polarized signals merging at a ferrite polarization selector switch. The resulting calibrated brightness temperatures, considered as a function of scan angle, are not symmetric around scan angle = 0. However, neither the origin of the asymmetry nor the manner in which the two orthogonal components are mixed has been fully understood. The new calibration model proposed incorporates all the leakage factors associated with the ferrite switches along the signal paths. The resulting calibration equations clarify how the orthogonal components of surface brightness are coupled at radiometers. As a consequence, the origin of the asymmetry is clearly identified and explained. In addition, the feasibility of absolute calibration using in-orbit data is discussed.

Han, Daesoo↗
NASA NTRS1991

Preliminary calibration plan for the Advanced Particles and Field Observatory (APAFO) magnetometer experiment

Prelaunch and postlaunch calibration plans for the APAFO magnetometer experiment are presented. A study of tradeoffs between boom length and spacecraft field is described; the results are summarized. The prelaunch plan includes: calibration of the Vector Fluxgate Magnetometer (VFM), Star Sensors, and Scalar Helium Magnetometer (SHM); optical bench integration; and acquisition of basic spacecraft field data. Postlaunch calibration has two phases. In phase one, SHM data are used to calibrate the VFM, total vector magnetic field data are used to calibrate a physical model of the spacecraft field, and both calibrations are refined by iteration. In phase two, corrected vector data are transformed into geocentric coordinates, previously undetected spacecraft fields are isolated, and initial geomagnetic field models are computed. Provided the SHM is accurate to the required 1.0 nT and can be used to calibrate the VFM to the required 3.0- nT accuracy, the tradeoff study indicates that a 12 m boom and a spacecraft field model uncertainty of 5 percent together allow the 1.0 nT spacecraft field error requirement to be met.

Voorhies, C. V.↗
NASA NTRS1990

Hubble Space Telescope: Cycle 1 calibration plan. Version 1.0

The framework for quantitative scientific analysis with the Hubble Space Telescope (HST) will be established from a detailed calibration program, and a major responsibility of staff in the Telescope & Instruments Branch (TIB) is the development and maintenance of this calibration for the instruments and the telescope. The first in-orbit calibration will be performed by the SI Investigation Definition Teams (IDTs) during the Science Verification (SV) period in Cycle 0 (expected to start 3 months after launch and last for 5 months). Subsequently, instrument scientists in the TIB become responsible for all aspects of the calibration program. Because of the long lead times involved, TIB scientists have already formulated a calibration plan for the next observing period, Cycle 1 (expected to last a year after the end of SV), which has been reviewed and approved by the STScI Director. The purpose here is to describe the contents of this plan. Our primary aim has been to maintain through Cycle 1 the level of calibration that is anticipated by the end of SV. Anticipated accuracies are given here in tabular form - of course, these accuracies can only be best guesses because we do not know how each instrument will actually perform on-orbit. The calibration accuracies are expected to satisfy the normal needs of both the General Observers (GOs) and the Guaranteed Time Observers (GTOs).

Stanley, Peggy↗
NASA NTRS1992

Improved HIRAP flight calibration technique

A method of removing non-aerodynamic acceleration signals and calibrating the High Resolution Accelerometer Package (HiRAP) has been developed and improved. Twelve HiRAP mission data sets have been analyzed applying the improved in-flight calibration technique. The application of flight calibration factors to the data sets from these missions produced calibrated acceleration levels within +/- 5.7 micro-g of zero during a time in-flight when the acceleration level was known to be less than 1 g. To validate the current in-flight calibration technique, the atmospheric density results, specifically the normal-to-axial density ratios, have been compared with the analysis results obtained with the previous in-flight calibration technique. This comparison shows an improvement (up to 12.4 percent per flight) in the density ratio when the updated in-flight calibration technique is used.

Moats, Christina D.↗
NASA NTRS1992

An atlas of selected calibrated stellar spectra

Five hundred and fifty six stars in the IRAS PSC-2 that are suitable for stellar radiometric standards and are brighter than 1 Jy at 25 microns were identified. In addition, 123 stars that meet all of our criteria for calibration standards, but which lack a luminosity class were identified. An approach to absolute stellar calibration of broadband infrared filters based upon new models of Vega and Sirius due to Kurucz (1992) is presented. A general technique used to assemble continuous wide-band calibrated infrared spectra is described and an absolutely calibrated 1-35 micron spectrum of alpha(Tau) is constructed and the method using new and carefully designed observations is independently validated. The absolute calibration of the IRAS Low Resolution Spectrometer (LRS) database is investigated by comparing the observed spectrum of alpha(Tau) with that assumed in the original LRS calibration scheme. Neglect of the SiO fundamental band in alpha(Tau) has led to the presence of a specious 'emission' feature in all LRS spectra near 8.5 microns, and to an incorrect spectral slope between 8 and 12 microns. Finally, some of the properties of asteroids that effect their utility as calibration objects for the middle and far infrared region are examined. A technique to determine, from IRAS multiwaveband observations, the basic physical parameters needed by various asteroid thermal models that minimize the number of assumptions required is developed.

Walker, Russell G.↗
NASA NTRS1993

Flight calibration assessment of HiRAP accelerometer data

A flight derived method of calibrating the High Resolution Accelerometer Package (HiRAP) flight data has been developed and is discussed for Shuttle Orbiter missions STS-35 and STS-40. These two mission data sets have been analyzed using ground calibration factors and flight derived calibration factors. This flight technique evolved early in the flight program when it was recognized that ground calibration factors are insufficient to determine absolute low-acceleration levels. The application of flight calibration factors to the data sets from these missions produced calibrated acceleration levels within an accuracy of less than +/- 1.5 microgravity of zero during a time in the flight when the acceleration level was known to be less than 1.0 microgravity. This analysis further confirms the theory that flight calibrations are required in order to obtain the absolute measurement of low-frequency, low-acceleration flight signals.

Blanchard, Robert C.↗
NASA NTRS1992

SAR calibration - An overview

Remote sensing with synthetic aperture radars (SAR's) is a rapidly developing field. Calibration of these sensors is required for the establishment of relationships between radar backscatter and geographical parameters. A review of recent progress in SAR calibration is presented. The quantities measured by SAR are defined and mathematical formulations of the three basic types of SAR images are developed. The establishment of scientific requirements for calibration and the difficulties involved are discussed. Image quality assessment is reviewed and the problems of radiometric calibration of SAR images using the radar equation and internal and external approaches are considered. Polarimetric radar calibration and the development of the necessary algorithms are described. Interferometric phase calibration and its associated problems are reviewed and future challenges in SAR calibration are discussed.

Freeman, Anthony↗
NASA NTRS1991

Calibration for the SAGE III/EOS instruments

The calibration plan for the SAGE III instruments for maintaining instrument performance during the Earth Observing System (EOS) mission lifetime is described. The SAGE III calibration plan consists of detailed preflight and inflight calibration on the instrument performance together with the correlative measurement program to validate the data products from the inverted satellite measurements. Since the measurement technique is primarily solar/lunar occultation, the instrument will be self-calibrating by using the sun as the calibration source during the routine operation of the instrument in flight. The instrument is designed to perform radiometric calibration of throughput, spectral, and spatial response in flight during routine operation. Spectral calibration can be performed in-flight from observation of the solar Fraunhofer lines within the spectral region from 290 to 1030 nm wavelength.

Chu, W. P.↗