Citation
Abstract
We investigate the effects of Deep Space Network (DSN) antenna-pointing errors on the measured phase stability and interferometric delay. The results are based on point-source focal plane scans of various DSN antennas. These are combined with an analytical model to estimate the stability of the measured phase in the presence of time-varying errors in the pointing within the central lobe of the antenna beam. The results suggest that phase fluctuations due to pointing errors are not yet a limiting factor in phase stability for 34-m antennas at frequencies below 12 GHz, but may become important at higher frequencies. For Cassini radio science measurements at 32 GHz (Ka-band), the need for closed-loop pointing control to meet the phase stability requirements is confirmed. For very long baseline interferometry, the effective phase and group delay errors that result from the mutual pointing errors of two antennas are the important quantities. We have estimated the effects of pointing fluctuations on 2.3-/8.4-GHz (S-/X-band) delay and find that, under normal conditions, they are well below the limits imposed by uncertainty in the tropospheric delay. At higher frequencies, using large antennas, pointing-induced delay errors may become important under conditions of poor pointing stability.
Keywords
Details
- Volume
- 42-132
- Published
- February 15, 1998
- Pages
- 1–19
- File Size
- 623.5 KB