Engineering topics
Publications and source records attributed to Lockhart, T. G..
We discuss client-side CORBA scripts implemented in Tcl, Perl, and Python. These are all technologies that are either currently being used on testbeds at JPL or being evaluated for future use. Finally, a Python example demonstrating implementation of a simple CORBA server is presented.
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VLBI observations of SS 433 at 2.3 GHz made on 12 days between 1979 May and 1980 August yield the following results: (a) the position angle of the radio 'jet' of angular size of about 0.1 arcsec varies approximately sinusoidally about a mean value of 100.2 + or - 1.7 deg with an amplitude of 19.3 + or - 3.4 deg for a period fixed at 163.6 days. This resolves the ambiguity in the two angles of the optical model of Abell and Margon and assigns the inclination of the axis of the precession cone to the 79 deg value; (b) the position angle of the radio structure on this scale lags that of the optical model by 17.4 + or - 1.6 days; and (c) at least some of the radio emitting material appears to propagate away from the core in blobs. Using the rate of change of angular separation of the blobs from the core obtained from measurements on four different days, and assuming that the radio emission is traveling at the speed derived for the optical jets from the kinematic model, a distance to SS 433 of 5.1 + or - 0.5 kpc is obtained.
The Project ARIES 9 meter transportable antenna was used as one element of very long baseline interferometer (VLBI) to begin monitoring locations of six sites in California relative to large diameter fixed antennas at the NASA Deep Space Network, Goldstone, California, and at the Caltech Owens Valley Radio Observatory, Big Pine, California. An accuracy of about 6 cm in the horizontal components was demonstrated by comparison with measurements of the National Geodetic Survey. The root of mean square scatter of the lengths of the baselines between any pair of antennas was about 3 cm except for the Goldstone-JPL (Pasadena) baseline. In the period August 1974 to August 1977 the length of this baseline increased by 15 + or - 5 cm as JPL moved westward relative to Goldstone at the rate of 6 + or - 2 cm/year. The baseline lengths were unaffected by the uncertainties of UT1, polar motion, and tropospheric water vapor, which are the limitations to present three dimensional vector accuracies.
Operation of the Astronomical Radio Interferometric Earth Surveying (ARIES) in a proof of concept mode is discussed. Accuracy demonstrations over a short baseline, a 180 km baseline, and a 380 km baseline are documented. Use of ARIES in the Sea Slope Experiment of the National Geodetic Survey to study the apparent differences between oceanographic and geodetic leveling determinations of the sea surface along the Pacific Coast is described. Intergration of the NAVSTAR Global Positioning System and a concept called SERIES (Satellite Emission Radio Interferometric Earth Surveying) is briefly reviewed.