The Small Deep Space Transponder is a

transponder In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

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 The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum defined as frequencies in the range 26.5–40 gigahertz (GHz), i.e. wavelengths from slightly over one centim ...

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 DBM or dbm may refer to: Science and technology * dBm, a unit for power measurement * DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB * Database Manager (DBM), a component of 1987's ''Extended Edi ...

. *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 MIL-STD-1553 is a military standard published by the United States Department of Defense that defines the mechanical, electrical, and functional characteristics of a serial data bus. It was originally designed as an avionic data bus for use with ...

. *Data interface via

EIA-422 RS-422, also known as TIA/EIA-422, is a technical standard originated by the Electronic Industries Alliance that specifies electrical characteristics of a digital signaling circuit. It was meant to be the foundation of a suite of standards that ...

(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 ''Deep Space 1'' (DS1) was a NASA technology demonstration spacecraft which flew by an asteroid and a comet. It was part of the New Millennium Program, dedicated to testing advanced technologies. Launched on 24 October 1998, the ''Deep Space ...

. 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 Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's hori ...

'' used a pair of SDSTs *

Mars Exploration Rover NASA's Mars Exploration Rover (MER) mission was a robotic space mission involving two Mars rovers, '' Spirit'' and '' Opportunity'', exploring the planet Mars. It began in 2003 with the launch of the two rovers to explore the Martian surface ...

s *

Mars Reconnaissance Orbiter ''Mars Reconnaissance Orbiter'' (MRO) is a spacecraft designed to study the geology and climate of Mars, provide reconnaissance of future landing sites, and relay data from surface missions back to Earth. It was launched on August 12, 2005, an ...

* MESSENGER * STEREO * Spitzer Space Telescope *A pair of SDSTs were used in the cruise stage of

Phoenix (spacecraft) ''Phoenix'' was an uncrewed space probe that landed on the surface of Mars on May 25, 2008, and operated until November 2, 2008. ''Phoenix'' was operational on Mars for sols ( days). Its instruments were used to assess the local habitabilit ...

. The lander used only UHF communication. *The

Mars Science Laboratory Mars Science Laboratory (MSL) is a robotic space probe mission to Mars launched by NASA on November 26, 2011, which successfully landed ''Curiosity'', a Mars rover, in Gale Crater on August 6, 2012. The overall objectives include investigati ...

includes two SDSTs, one on the descent stage and one on the lander itself. The SDST on the descent stage was the main transponder for the cruise and landing portions of the flight, with the SDST on the rover as a backup. The descent stage crashed after lowering the rover, and the SDST on the lander became the active transponder. As many tightly constrained, high-performance systems, the SDST has a number of idiosyncrasies in operation. 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. For

cubesat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats ...

missions, the SDST is too big, heavy, and power-hungry. For these missions, the Iris transponder could be considered instead.

References

{{authority control Jet Propulsion Laboratory Mars Science Laboratory Spitzer Space Telescope Mars Reconnaissance Orbiter

Functions

Missions

See also

References