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Galileo Orbiter

NSSDCA ID: 1989-084B

Telecommunications Description

Communications for Galileo were primarily through the 70 m DSN antennas. Because the high-gain antenna (HGA) could not be deployed early in the mission (due to the spacecraft's proximity to the sun), the 70 m antennas were required because communications had to be made utilizing one of the two low-gain antennas (LGA) at very low rates. If the HGA had deployed correctly after the Earth-1 flyby, communications during much of the interplanetary cruise phases, as well as at the asteroid and Earth-2 flybys, could have been partially supported (subject to availability) by the 34 m DSN antennas. However, because the HGA did not deploy, use of the two LGAs continued and thus the sensitivity of the 70 m antennas was still required. All attempts of freeing the frozen HGA ribs were unsuccessful, the last occurring on 22 March 1996. Some on-board storage capability (a tape recorder) was available.

Both X- and S-band transceivers were planned to be utilized for uplink and downlink communications. Use of the LGAs resulted only in the use of the S-band transceiver, originally intended for low-rate engineering data transmission. S-band transmission was at 2295 MHz and X-band at 8415 MHz. The majority of the telecommunications equipment was inherited from the Voyager spacecraft, the exceptions being the S/X antenna elements and the X/S downconverter.

To enhance the data return from Galileo, modifications were made to the Deep Space Network so that the antennas in Australia and California could be arrayed to permit a higher transmission data rate. This change in the configuration of the DSN antennas was expected to allow an increase in the data returned by Galileo at Jupiter by a factor of 10, enabling 70% of the science goals to be achieved. This alteration, along with data compression techniques used on the spacecraft, effectively increased the data returned from a mere 10 bps to 1,000 bps. The change in operation took place in November 1996 during Galileo's first flyby of Callisto.

Telemetry Path

Telemetry support via Deep Space Network (DSN)

Effective Telemetry

0.01 kbps

Telemetry Rates

0.01-134.4 kbps

Additional Information

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