Citation
Abstract
A number of the proposals for supporting a Galileo S-band (2.3-GHz) mission involve arraying several antennas to maximize the signal-to-noise ratio (and bit rate) obtainable from a given set of antennas. Arraying is no longer a new tdea, having been used successfully during the Voyager encounters with Uranus and Neptune. However, arraying for Galileo’s tour of Jupiter is complicated by Jupiter’s strong radio emission, which produces correlated noise effects. This article discusses the general problem of correlated noise due to a planet, or other radio source, and applies the results to the specific case of an array of antennas at the DSN’s Tidbinbilla, Australia, complex (DSS 42, DSS 43, DSS 45, and the yet-to-be built DSS 34). The effects of correlated noise are highly dependent on the specific geometry of the array and on the spacecraft—planet configuration; in some cases, correlated noise effects produce an enhancement, rather than a degradation, of the signalto-noise ratio. For the case considered here—an array of the DSN’s Australian antennas observing Galileo and Jupiter—there are three regimes of interest. If the spacecraft—planet separation is <75 arcsec, the average effect of correlated noise is a loss of signal to noise (~0.2 dB as the spacecraft-planet separation approaches zero). For spacecraft—planet separations 275 arcsec, but x400 arcsec, the effects of correlated noise cause signal-to-noise variations as large as several tenths of a decibel over time scales of hours or changes in spacecraft—planet separation of tens of arcseconds; however, on average its effects are small (<0.01 dB). When the spacecraft is more than 400 arcsec from Jupiter (as is the case for about half of Galileo’s tour), correlated noise is a <0.05-dB effect.
Details
- Volume
- 42-111
- Published
- November 15, 1992
- Pages
- 129–152
- File Size
- 857.8 KB