An experimental investigation of the changes of VLBI time delays due to antenna structural deformations
Abstract
Structural deformations primarily occur as functions of antenna elevation angle due to gravity loading. For a Cassegrain antenna, one of the major effects of structural deformation on measured VLBI time delays are those delay changes associated with axial subreflector displacement from its nominal position. Two types of time delay changes that occur when the subreflector is axially defocused are: a change which is a linear function of subreflector defocus position; and a cyclical change caused by multipath. Test results show that for the 64-m DSN antenna, the linear change is 1.8 times the subreflector defocus position, while the peak-to-peak change in cyclical variation is about + or - 3 cm when a spanned bandwidth of 38 MHz at 2290 MHz is used.
- Publication:
-
The Telecommunications and Data Acquisition Report
- Pub Date:
- April 1982
- Bibcode:
- 1982tdar.nasa....8O
- Keywords:
-
- Cassegrain Antennas;
- Deformation;
- Structural Strain;
- Superhigh Frequencies;
- Time Lag;
- Ultrahigh Frequencies;
- Very Long Base Interferometry;
- Deep Space Network;
- Parabolic Antennas;
- Spacecraft Tracking;
- Subreflectors;
- Tracking Stations;
- Communications and Radar