Small deep space transponder

The Small Deep Space Transponder is a transponder designed by JPL specifically for deep space probes.^[1] 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.^[2]

Functions

The capabilities of the SDST include:^[3]

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:^[4]

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
Dawn used a pair of SDSTs^[5]
Mars Exploration Rovers
Mars Reconnaissance Orbiter
MESSENGER
STEREO
Spitzer Space Telescope
A pair of SDSTs were used in the cruise stage of Phoenix (spacecraft). The lander used only UHF communication.^[6]
The yet to be launched Mars Science Laboratory. This includes 2 SDSTs, one on the descent stage and one on the lander itself. The SDST on the descent state is the main transponder for the cruise and landing portions of the flight, with the SDST on the rover as a backup. During the landing, the descent stage will crash after lowering the rover, and the SDST on the lander becomes the active transponder.^[7]

As do many tightly constrained, high performance systems, the SDST has an number of idiosyncrasies in operation.^[5] However, as the Dawn telecom 'lessons learned' section points out, the use of common hardware such as the SDST allows knowledge of these characteristics from previous projects.^[5]

References

^ Sam Zingales. "Small Deep-Space Transponder Development". JPL. http://deepspace.jpl.nasa.gov/technology/TMOT_News/DEC95/zingales.htm.
^ "Technology: SMALL DEEP SPACE TRANSPONDER". JPL. http://nmp.nasa.gov/ds1/tech/transponder.html.
^ Chien-Chung Chen, Shervin Shambayati, Andrew Makovsky, F. H. Taylor, Martin I. Herman, Samuel H. Zingales, Carl Nuckolls, Keith Siemsen. "Small Deep Space Transponder (SDST) DS1 Technology Validation Report". http://nmp-techval-reports.jpl.nasa.gov/DS1/SDST_Integrated_Report.pdf.
^ "NMP (New Millennium Program) Scorecard". http://nmp.nasa.gov/TECHNOLOGY/scorecard/scorecard_results.cfm.
^ ^a ^b ^c Jim Taylor (August 2009). "Dawn Telecommunications". JPL. http://descanso.jpl.nasa.gov/DPSummary/090924dawn-FinalCorrex--update5G.pdf.
^ Jim Taylor, Stan Butman, Chad Edwards, Peter Ilott, Richard Kornfeld, Dennis Lee, Scott Shaffer, Gina Signori (August 2010). "Phoenix Telecommunications". JPL. http://descanso.jpl.nasa.gov/DPSummary/PhxArticle_--RC101013DocX_COMPRESSED_AcronFixBU.pdf.
^ Andre Makovsky, Peter Ilott, Jim Taylor (2009). "Mars Science Laboratory Telecommunications System Design". JPL. http://descanso.jpl.nasa.gov/DPSummary/Descanso14_MSL_Telecom.pdf.