DS1 Beacon

This is a photo of the downlink from the Deep Space 1 spacecraft displayed by an SSI (spectral signal indicator). This kind of display can be obtained quickly when the Deep Space Network antenna points to a spacecraft, since it does not require acquisition and processing of telemetry data. This makes it possible to use short periods of DSN tracking time to simply "look in" on the spacecraft's state of health.

The horizontal wiggly line represents mostly radio noise. The peak near the cursor labelled "AB" is the spacecraft's carrier at f_c (X-band center carrier frequency) near the middle of the display. A smaller peak can be seen near the cursor labelled 'C' on the right. This peak near 40 kHz above f_c and its counterpart on the left toward the "-50.000 kHz" label, constitutes a view of the beacon subcarrier. These labelled peaks can be seen to persist over time, while most of the smaller noise-peaks appear to change constantly. Simply viewing this display is enough to recognize which of a few different "beacon" signatures is present, therefore deducing the state of the spacecraft without having to lock up, process, and distribute telemetry data.