VLBI Observations of ALSEP Transmitters

The technique of differential very-long-baseline inteferometry (VLBI) Apollo Lunar Surface Experiments Package was used to measure the relative positions of the (ALSEP) transmitters at the Apollo 12, 14, 15, 16, and 17 lunar landing sites with uncertainties less than 0.005 sec of the geocentric arc. These measurements yielded improved determinations of the selenodetic coordinates of the Apollo landing sites, and of the physical libration of the moon

Analysis of lunar laser ranging data for Earth dynamics applications

The effects of elasticity and of tidal friction within the Moon were incorporated into the numerical model of the Moon's rotation which was used in an effort to determine the axial rotation of the Earth, as measured by Universal Time. Some 2,651 normal points representing ranges measured to Lunokhod 2, and to the Apollo 11, 14, and 15 retroflectors were analyzed. Smoothed estimates derived from the lunar rangefinding were compared with smoothed values published by the International Bureau of Time, in the 1968 and 1969 systems. The derived values at the observation sight were connected to corresponding values at the Conventional International Origin, using the BIH data for polar motion. Differences are discussed

Precision selenodesy and lunar libration through VLBI observations of ALSEPs

Data from 500 observation series, each one representing about five hours' continuous observation of a pair of ALSEPs by differential very long baseline interferometers (VLBI) have been compiled on magnetic tape. The theoretical models used to calculate the rotation of the earth, the orbit of the moon, the libration of the moon, and the basic VLBI observable were improved substantially. Analysis of data from long spans of VLBI observations was begun

Applications to Earth physics: Very-long-baseline interferometry and data analysis

A range of very long baseline interferometry experiments applied to Earth physics are covered

Analysis of the Capability and Limitations of Relativistic Gravity Measurements Using Radio Astronomy Methods

The uses of radar observations of planets and very-long-baseline radio interferometric observations of extragalactic objects to test theories of gravitation are described in detail with special emphasis on sources of error. The accuracy achievable in these tests with data already obtained, can be summarized in terms of: retardation of signal propagation (radar), deflection of radio waves (interferometry), advance of planetary perihelia (radar), gravitational quadrupole moment of sun (radar), and time variation of gravitational constant (radar). The analyses completed to date have yielded no significant disagreement with the predictions of general relativity

Miniature interferometer terminals for earth surveying

A system of miniature radio interferometer terminals was proposed for the measurement of vector baselines with uncertainties ranging from the millimeter to the centimeter level for baseline lengths ranging, respectively, from a few to a few hundred kilometers. Each terminal would have no moving parts, could be packaged in a volume of less than 0.1 cu m, and would operate unattended. These units would receive radio signals from low-power (10 w) transmitters on earth-orbiting satellites. The baselines between units could be determined virtually instantaneously and monitored continuously as long as at least four satellites were visible simultaneously

Spin-orbit resonance of Mercury.

Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. Thesis. 1969. Ph.D.MICROFICHE COPY ALSO AVAILABLE IN AERO LIBRARY.Lacking p. 83-84 and 97-98. Vita.Bibliography: leaves 64-66.Ph.D

Precision surveying using very long baseline interferometry

Radio interferometry measurements were used to measure the vector baselines between large microwave radio antennas. A 1.24 km baseline in Massachusetts between the 36 meter Haystack Observatory antenna and the 18 meter Westford antenna of Lincoln Laboratory was measured with 5 mm repeatability in 12 separate experiments. Preliminary results from measurements of the 3,928 km baseline between the Haystack antenna and the 40 meter antenna at the Owens Valley Radio Observatory in California are presented

Polar motion and UT1: Comparison of VLBI, lunar laser, satellite laser, satellite Doppler, and conventional astrometric determinations

Very long baseline interferometry observations made with a 3900 km baseline interferometer (Haystack Observatory in Massachusetts to Owens Valley Observation in California) were used to estimate changes in the X-component of the position of the Earth's pole and in UT1. These estimates are compared with corresponding ones from lunar laser ranging, satellite laser ranging, satellite Doppler, and stellar observations

Application of very long baseline interferometry to Astrometry and Geodesy: effects of frequency standard instability on accuracy

The accuracy of geodetic and astrometric information obtained from very long baseline interferometry (VLBI) observations is dependent upon the stability of the frequency standard, or clock, used at each site of VLBI array. The sensitivities of two hydrogen maser frequency standards of different design to pressure, temperature, and magnetic field variations were measured; and, for one of the standards, sensitivity was found to be severe enough to degrade the information content of VLBI measurements. However, the effect on the geometric and astrometric information of such clock instabilities, with time scales of hours or greater, can be sharply reduced through the use of differencing techniques