Small Deep Space Transponder

Reliable X-Band and Ka-Band Deep Space Transmission

The Small Deep Space Transponder (SDST), developed by General Dynamics and NASA’s Jet Propulsion Laboratory, is a spacecraft terminal for X-Band and Ka-Band telecommunications with the NASA Deep Space Network (DSN). Making extensive use of MMICs, multichip modules, and a new signal processing ASIC, the SDST’s flexible design provides the capability to meet the telecommunication needs of nearly every deep space mission.

  • NASA's Deep-Space Network (DSN) Compatible
  • Radiation and SEU Tolerant
  • MIL-STD-1553 Interfaces – Standard and Low Power
  • Option for Ka-Band downlink (independent of X-band Functionality)

Current Missions

The Small Deep Space Transponder (SDST) is currently flying on multiple deep space missions totaling over 1,000,000 in-flight operational hours including:

Future Missions

  • Lucy
  • Psyche

Past Missions

  • Cassini
  • Spirit Mars Rover
  • Opportunity Mars Rover


The SDST has two configurations. The X/X configuration consists of an X-band receiver and an X-band 880F1 exciter. The X/X/Ka configuration consists of an X-band receiver, an X-band 880F1 exciter and an X-band 840F1 exciter. The 840F1 exciter drives an external x4, X-to-Ka-band multiplier mounted to the user’s Ka-band power amplifier, allowing interconnection by coaxial cable rather than waveguide. The SDST is designed for use with our 15 watt X-band Solid State Power Amplifier (SSPA) and other customer supplied X and Ka-band power amplifiers. The 15 watt X-band SSPA is designed to supply telemetry signals that can be connected directly to the SDST to make a complete transmitter/receiver with a single MIL-STD-1553B data interface.

  • Deep-Space Network Compatible
  • Redundant I/O for Cross-Strapping
  • X-Band Receiver, X and Ka-Band Exciters
  • 2.1 dB Typical Noise Figure @25°C
  • -158 dBm Typical Sensitivity @ 25°C
  • Temp Compensated Receiver VCO
  • Low Exciter Spurious, Phase Noise, and Allan Deviation
  • Radio Science Mode (using USO Input)
  • 6 ns Typical Ranging Delay Variation
  • 30 Mbps Max TLM Symbol Rate
  • 0.5 ns Typical Carrier Delay Variation
  • MIL-STD-1553 Interface – Standard and Low Power
  • External Power Converter Synchronization Capability
  • Operates Under Launch Environments
  • Radiation and SEU Resistant
  • Internal Telemetry Modulation Encoder
  • Internal Command Detector with External Baseband Input
  • Mounting in Either of Two Axes
  • Firmware Options:
    • Carrier Tracking Loop Bandwidth
    • Command Detector Subcarrier Frequencies and Data Rates
    • Custom Command/Telemetry Interface Format
    • Custom POR state




Small Deep Space Transponder Data Sheet



View Document


Mass 7.0 lbs (3.2 kg) maximum
Input Supply Voltage 22 to 36 VDC, or ±11 to ±18 VDC
Input Supply Power Receiver Only: 12.5 W nominal
Receiver + X-Band Exciter: 15.8 W nominal
Receiver + X and Ka-Band Exciters: 19.5 W nominal
Envelope Size 7.13”L x 6.55”W x 4.50”H
External Synch Frequency 125 kHz nominal
Radiation Total Dose 50 krads (Si) (part level), 100 krad optional
Operating Temperature -40 to +60° C