Table 1 of DSN Telecommunications Link Design Handbook, 201, Rev. B, Frequency and Channel Assignments gives Spacecraft Transponder Turnaround Ratios that are supported by the Deep Space Network. These are the PLL controlled divide-by ratios that a spacecraft uses when receiving a carrier frequency from the DSN and retransmitting a different frequency back to Earth which is still phase-coherent, for the purposes of precise doppler shift measurements as part of a determination of a (usually deep space) spacecraft's trajectory. Read more about this in How does a three-way doppler shift measurement work?.

Some of the supported ratios are within-band and close to unity; X to X-band, Ka to Ka-band and S to S-band. This means that the spacecraft must simultaneously receive a very weak signal and transmit a very strong signal at frequencies that are very close, and this requires more frequency rejection in the spacecraft's receive circuit.

Question: Are there any deep-space spacecraft which actually support within-band turn-around for Earth-based doppler measurements? Are these spacecraft using one dish for simultaneous receive and transmit within the same band?

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1 Answer 1


Yes, and yes. The standard Doppler data type on deep-space spacecraft is X-band to X-band, and transmit and receive are on the same antenna. Most deep-space spacecraft only have X-band transceivers. A few have more than one band, usually for either radio science reasons and/or higher data rate on Ka (accepting some added risk of weather interference). S-band is passé.


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