Small Deep Space Transponder

The Small Deep Space Transponder is a transponder designed by JPL specifically for deep space probes. It unifies a number of communication functions - receiver, command detector, telemetry modulator, exciters, beacon tone generator, and control functions - into one 3-kg package. The SDST is designed to handle X band uplink and both X band and Ka band downlink. JPL estimates that performing the same functions with separate units (as was done previously) requires over twice the mass and 4 or 5 individual subassemblies.

Functions

The capabilities of the SDST include:

• X-band receiver/downconverter capable of carrier tracking at or below −156 dBm.
• Command detector unit function.
• Telemetry modulation function.
• X- and Ka-band exciters.
• Beacon mode operation.
• Coherent and noncoherent operation choice.
• X- and Ka-band ranging.
• Differential one-way ranging (DOR) for both X-band and Ka-band.
• Command and Data Handling (C&DH) communication via MIL-STD-1553.
• Data interface via EIA-422 (also known as RS-422).
• External ports for temperature sensors.
• External port for an analog signal.

Missions

SDST has been used in the following missions:

• Deep Space 1. This was a developmental mission that used the transponder for the first time, as part of an effort to qualify new technologies for flight.
• Deep Impact (space mission)
• Dawn (spacecraft)
• Mars Exploration Rovers
• Mars Reconnaissance Orbiter
• MESSENGER
• STEREO
• Spitzer Space Telescope
• The cruise stage of Phoenix (spacecraft).
• The yet to be launched Mars Science Laboratory