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The means of storing multispectral, high resolution sensor data on an Earth observing satellite are studied. It is concluded that this is best done digitally on a multi-track, longitudinal, magnetic tape recorder. The machine proposed will store 8 X 10 to the 10th power bits of data on 1040 m of 51 mm-wide magnetic tape mounted on two co-planar reels.
The application of satellite high resolution infrared data was studied for mapping snow cover. The study has two objectives: (1) to determine whether existing radiometers onboard the Nimbus and ITOS satellites can provide hydrologically useful snow information, and (2) to develop analysis techniques applicable to future IR sensor systems on earth satellites. The IR measurements are being analyzed in conjunction with concurrent satellite photographs and conventional snow cover data.
Bragg-reflex images of small individual crystallites in the size range of 20-100 A diameter with known crystallographic orientation were used in a transmission electron microscope to determine in-situ: (a) the relationship between objective lens current (or accelerating voltage) changes in discrete steps and corresponding defocus, (b) the spherical aberration coefficient, and (c) the axial chromatic aberration coefficient of the objective lens. The accuracy of the described method is better than 5%. The same specimen can advantageously be used to properly aline the illuminating beam with respect to the optical axis.
Discussion of the theory of a technique for image restoration in the reconstruction of a spatial input scene mapped by a line scanner. Special attention is given to the application of this technique in reducing the data telemetered from the Infrared Scanning Radiometer of the Apollo 17 spacecraft. The technique is based on the theory of splines and uses the results of optimal approximation studies by Colomb (1959), Sard (1967), and Anselone (1968). A recursive algorithm is also developed to improve the reconstruction. The study treats a one-dimensional case, but the treatment can be readily extended to multi-dimensional situations.
This document describes the design and operation of a low resolution radar data recording system for precipitation measurements. This system records a full azimuth scan on seven track magnetic tapes every five minutes. It is designed to operate on a continuous basis with operator intervention required only for changing tape reels and calibration.
Development of a dual polarized L-band radar imaging system to be used in conjunction with the present dual polarized X-band radar is described. The technique used called for heterodyning the transmitted frequency from X-band to L-band and again heterodyning the received L-band signals back to X-band for amplification, detection, and recording.
A design study on adding a radar altimeter to the Pioneer Venus small probe is review. Block and timing diagrams are provided. The inherent and interface ambiguities, resolution, and data handling logic for radar altimeters are described.
Values of the solar constant and solar spectrum have been adopted as design standards for NASA space vehicles and as engineering standards by IES/ASTM. High resolution spectral data for the UV and visible range, normalized to these standards have been derived. Applications of these results for weather analysis, air pollution, ozone production, and atmospheric energy exchange are reviewed. Indications of possible variations in solar energy, total and spectral, and their influence on the earth-atmosphere system are examined. Programs for future studies of these variations from satellites and high-altitude aircraft are discussed.
High-resolution radar data, taken from over the 1500-km circular area that was at the center of the planetary disk on June 20, 1972, show that this part of Venus is nearly flat and cratered. The largest crater is 160 km across, but only about 500 m deep. The smallest craters that can be resolved are about 35 km across.
Systems incorporated into the SPANDAR to increase spatial resolution and data processing capabilities are described. They include a minicomputer that performs real-time formatting of video data, rapid antenna scan control, and control of a digital integrator; a frequency diversity technique for faster accumulation of independent video samples; the on-line calibration system for insertion of high and low calibration signals during every PRF interval; and utilization of a large capacity, high speed computer. The resultant data will be used to create statistical thunderstorm models for designing microwave communications systems.
Spectra from the satellite instrument Iris (infrared interferometer spectrometer) were examined to find the number of independent variables needed to describe the broad-band high-resolution spectral data. The radiated power in the atmospheric window from 771 to 981 per cm was the first parameter chosen for fitting observed spectra. At succeeding levels of analysis, the residual variability (observed spectrum minus best-fit spectrum) in an ensemble of observations was partitioned into spectral eigenvectors. The eigenvector describing the largest fraction of this variability was examined for a strong spectral signature; the power in the corresponding spectral band was then used as the next fitting parameter. The measured power in nine spectral intervals, when it was inserted in the spectral-fitting functions, was adequate to describe most spectra to within the noise level of Iris. Considerations of relative signal strength and scales of atmospheric variability suggest a combination sounder (multichannel, broad field of view) scanner (window channel, small field of view) as an efficient observing instrument.
Several scanner design parameters that greatly affect data rates were varied to determine overall effect on data rates. Bit rates were calculated for scanners with 10-, 15-, 20-, and 30-meter instantaneous fields of view; with 5, 7, and 10 channels; and with swath widths of 46.3, 92.6, 138.9, and 185.2 kilometers (25, 50, 75, and 100 nautical miles). The data were analyzed to determine whether they could be (1) recorded onboard the spacecraft with currently available equipment, (2) recorded onboard with the equipment proposed for the 1980-90 period, (3) transmitted to earth with current or proposed equipment; and (4) compressed and decompressed without significant degradation of classification accuracy. The effect of classifying 10-meter scanner data on the existing and the development pattern-recognition systems was examined.
Radiation from lightning in the RF band from 3-300 MHz were monitored. Radiation in this frequency range is of interest as a potential vehicle for monitoring severe storms and for studying the lightning itself. Simultaneous measurements were made of RF radiation and fast and slow field changes. Continuous analogue recordings with a system having 300 kHz of bandwidth were made together with digital records of selected events (principally return strokes) at greater temporal resolution. The data reveal patterns in the RF radiation for the entire flash which are characteristic of flash type and independent of the frequency of observation. Individual events within the flash also have characteristic RF patterns. Strong radiation occurs during the first return strokes, but delayed about 20 micron sec with respect to the begining of the return stroke; whereas, RF radiation from subsequent return strokes tends to be associated with cloud processes preceding the flash with comparatively little radiation occurring during the return stroke itself.
LANDSAT 1, launched in July 1972, and LANDSAT 2, launched in January 1975, are equipped with a similar complement of sensors. Each spacecraft has both a return beam vidicon camera system and a multispectral scanner for acquiring high resolution multispectral data of the Earth's surface on a global basis. A description is given of these imaging systems and the primary sensors on the LANDSAT 1 and 2 spacecraft.
A concept for determining the relative abundance of elements contained in cometary particulates was evaluated. The technique utilizes a short, high intensity burst of laser radiation to vaporize and ionize collected particulate material. Ions extracted from this laser produced plasma are analyzed in a time of flight mass spectrometer to yield an atomic mass spectrum representative of the relative abundance of elements in the particulates. Critical aspects of the development of this system are determining the ionization efficiencies for various atomic species and achieving adequate mass resolution. A technique called energy-time focus, which utilizes static electric fields to alter the length of the ion flight path in proportion to the ion initial energy, was used which results in a corresponding compression to the range of ion flight times which effectively improves the inherent resolution. Sufficient data were acquired to develop preliminary specifications for a flight experiment.
There is a strong rationale for increasing the rate of information return from imaging class experiments aboard both terrestrial and planetary spacecraft. Future imaging systems will be designed with increased spatial resolution, broader spectral range and more spectral channels (or higher spectral resolution). The data rate implied by these improved performance characteristics can be expected to grow more rapidly than the projected telecommunications capability. One solution to this dilemma is the use of improved onboard data processing. The use of onboard classification processing in a multispectral imager can result in orders of magnitude increase in information transfer for very specific types of imaging tasks. Several of these processing functions are included in the conceptual design of an Infrared Multispectral Imager which would map the spatial distribution of characteristic geologic features associated with deposits of economic minerals.
Measurements are presented showing strong tailward flow of ions along the dawn magnetopause as the Voyager 1 spacecraft crossed the earth's magnetosphere boundary following launch on September 5, 1977. With one exception all of the observed flows occur outside the magnetopause. The particle flux measurements at energies of at least about 30 keV, together with the observed magnetic-field signatures of the boundary crossing, are consistent with a minimum tailward ion energy flow of about (2-7) x 10 to the 17th erg/s at the time of observation. High-time-resolution particle data indicate that the ion flow can vary on a time scale of about 400 ms. These results, together with recent results from several other spacecraft, show conclusively that a source of energetic particles exists sunward of the dawn-dusk meridian
The sea surface heights above the reference ellipsoid were determined for several regions of the world's ocean using data from the radar altimeter on board the GEOS-3 satellite in conjunction with precise orbital position information derived from laser data. The resolution of the estimated sea surfaces varied from 0.25 degrees off the east coast of the United States to about 2 degrees in the Indian Ocean near Australia. The rms crossover discrepancy after adjustment varied from 30 cm to 70 cm depending on geographic location. Comparison of the altimeter derived mean sea surface in the North Atlantic with the 5 x 5 ft GEM-8 detailed gravimetric geoid indicated a relative consistency of better than one meter.