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Geodetic satellite observation systems comparisons
Minitrack measurements compared to optically determined orbit for calibrating Minitrack antenna arrays
Long arc orbital solutions from Geos-1 satellite used to evaluate range and range rate tracking system
Comparing measured ranges from range rate tracking systems with optical reference orbits
Photography of Geos 1 flashes with Baker-Nunn and K-50 geodetic cameras
Goddard range and range rate tracking system at Rosman, N.C., evaluated using Explorer 29 /GEOS 1/ long arc orbital solutions
Minitrack and optical tracking networks compared using Explorer 29 /GEOS 1/ long arc orbital solutions
US Army SECOR and optical tracking networks compared using Explorer 29 /GEOS 1/ long arc orbital solutions
Atmospheric refraction formulas computed and evaluated for use in geodetic satellite tracking
Orbital solutions based on critical optical tracking and Doppler observations, comparing with GEOS 1 and 2 satellite orbits
Detailed temporal measurements of the solar flux at one location are performed. These data are then analyzed and compared to the potential of space measurements which allow one to consider the flux falling on areas of the earth. An important result of the research is that the temporal characteristics of the flux in the presence of a real atmosphere would be difficult to obtain from space and that the variations in the flux can be highly significant in regard to most solar conversion schemes. The detailed results of the research are presented. The instruments developed to separate the direct and scattered solar flux, the computer analysis methods developed, and the results of the research, presented as both graphical and tabular data, are discussed.
Using NASA facilities in space (OSO-7) and on the ground (Goddard multi-channel spectrophotometer at Sacramento Peak, New Mexico) an active region has been mapped. By combining these ultraviolet, X-ray, and visible data, a physical picture of this structured region was constructed from the photosphere to the corona, corresponding to temperature regimes from 4500 K to 4,000,000 K. The morphology of the active region was studied by comparing grey-shaded images in which fine details stand out more clearly than in the contour plots. One result of the study is that gross similarities persist from the low photosphere up to high in the transition region, while some changes occur in the corona.
Number-density data obtained at orbital 'crossover' points with the neutral-gas mass spectrometers aboard the Esro 4, Aeros A, AE-C, and Aeros B satellites are intercompared. All the mass spectrometers were designed to measure the ambient number densities of atomic oxygen, molecular nitrogen, helium, and argon. It is found that the agreement for N2 and O is satisfactory within the experimental errors and that the He measurements exhibit unexpectedly large discrepancies far outside the error range. Calibration and instrument sources of error are considered.
Recent experiments are described which directly intercompare very long baseline interferometry (VLBI) with laser ranging to artificial satellites by measuring the vector lengths of the same intercontinental baselines. These experiments are part of the VLBI/Laser-Intercomparison Project, a continuing task to assess the suitability of VLBI to various geophysical applications.
A series of dual-instrument vertical ozone soundings was carried out for the purpose of comparing the Electrochemical Concentration Cell Ozonesonde with different ozonesondes used by the international scientific community. Total ozone overburdens at the time of the soundings were also measured with a Dobson spectrophotometer.
The in-situ rocketsonde for ozone profile measurements developed and flown for geophysical research and satellite comparison is reviewed. The measurement principle involves the chemiluminescence caused by ambient ozone striking a detector and passive pumping as a means of sampling the atmosphere as the sonde descends through the atmosphere on a parachute. The sonde is flown on a meteorological sounding rocket, and flight data are telemetered via the standard meteorological GMD ground receiving system. The payload operation, sensor performance, and calibration procedures simulating flight conditions are described. An error analysis indicated an absolute accuracy of about 12 percent and a precision of about 8 percent. These are combined to give a measurement error of 14 percent.
Measurements and time biases of the GEOS 3 tracking systems in the Atlantic calibration area were determined in relation to the Goddard lasers. In collocation tests the lasers agreed with each other to about 10 cm. Early RAMLAS laser data contained an apparent time bias of 647 microsec. Later, in a laser collocation test, RAMLAS differed from MOBLAS 2 by +11.3 cm and -28 microsec. An overlooked correction reduced the -28 microsec to -8 microsec. The geoceivers initially had range rate biases of 3-6 m/s and constant time biases of several milliseconds. During the first month of GEOS 3 operations the range rate biases decreases monotonically by 2.5 + or - 1.0 m/s. The C band radar biases relative to the lasers were usually within several meters and several tenths of milliseconds. The unified S band system relative biases were usually within + or - 4 mm/s and + or - 0.1 ms. The average and scatter of the altimeter biases recovered on 18 laser reference arcs was - 5.3 + or - 0.6 m.