Citation
Abstract
A series of experiments has been conducted at the Jet Propulsion Laboratory during the last decade to develop a radio interferometric system capable of measuring crustal and rotational motions of the earth, as well as source positions for a reference frame based on compact extragalactic radio sources. With the exception of one session between Big Pine, Calif., and Westford, Mass., the observing stations were those of NASA’s Deep Space Network in California, Spain, and Australia. Approximately 2400 observations of extragalactic radio sources were made between August 1971 and February 1980 during 48 separate sessions. These consisted of 259 delay rate observations at 2.3 GHz (S-band), 796 delay and delay rate observations at either S-band or 8.3 GHz (X-band) and 1325 delay and delay rate observations recorded simultaneously at both S- and X-band. A single multiparameter fit has been applied to the observed values of delay and delay rate to extract astrometric and geophysical parameters from this decade-long sequence. The fit produced estimates of 784 parameters, including station locations, radio source positions, polar motion, Universal Time, the precession constant, and solid earth tides. The a priori model included gravitational bending, the 1980 IAU nutation series, the 1976 IAU expressions for Greenwich mean Sidereal time and precession, BIH estimates of Universal Time and polar motion, and monthly mean values for zenith troposphere delay. The rms residuals were 0.52 nsec for delay and 0.30 psec/sec for delay rate. Intercontinental baseline lengths have been determined with formal uncertainties of 5 to 10 cm. Universal Time and polar motion were measured at 49 epochs, with formal uncertainties (for the more recent data) of 0.5 msec for UTI and 6 and 2 mas, respectively, for the X and Y components of polar motion. Our 1971-80 data produced a formal estimate of the luni-solar precession constant that was smaller than the 1976 IAU value by -3.8.
Details
- Volume
- 42-73
- Published
- May 15, 1983
- Pages
- 128–155
- File Size
- 2.0 MB