Transponder:
The system will incorporate two redundant small deep-space transponders (SDST’s) , developed by General Dynamics and NASA’s Jet Propulsion Laboratory. This device combines a number of communication functions – receiver, command detector, telemetry modulator, exciter, beacon generator and control functions all into one package. This transponder has Ka-band capability as well for future missions, which comprises of a second X-to-Ka band multiplier.
Envelope Size: 7.13”L x 6.55”W x 4.50”H
Mass: 7.0 lbs (3.2 kg)
Input Supply Power:
Receiver Only: 12.5 W
Receiver + X-band Exciter: 15.8 W
Amplifiers:
Two 17 W, 8.4 GHz solid-state power amplifiers, manufactured by General Dynamics will be implemented as smaller, lighter and less expensive alternative to the traveling-wave-tube X-band amplifier. These amplifiers are designed for use as a ‘companion unit’ to the SDST and can supply telemetry signals that can be connected directly to the SDST to make a complete transmitter/receiver with a single data interface.
Maximum dimensions: 6.85”L x 5.275”W x 1.85”H
Mass: 3.02 lbs (1.37 kg)
Data interface: MIL-STD-1553B data interface
Other components:
Other smaller components include a diplexer, attached to the high-gain amplifier, which will allow the S- and X- band transmitter to use the same antenna, as well as allowing the antenna to be used for transmissions on one band and receive on another band. The system will also require a coupler to assign the amplifiers to the respective antennas as well as a hybrid coupler between the amplifiers and the transponders to allow either transponder to drive either amplifier without requiring active switching.
Issues in Deep Space Communications:
Compared with normal satellite communications, deep-space communications present a significant challenge – specifically from the distance resulting in low signal-to-noise ratio, propagation delays, corruption as well as environmental factors such as temperature variations and electromagnetic radiation. The satellite will be passing behind the Sun for a period of time, it is important to note that communication will be masked for a substantial period of time. One possible solution is to take advantage of NASA’s STEREO (Solar TERrestrial Relations Observatory) satellites in orbit around the sun to provide a link between the satellite-comet intercept point and Earth while the satellite is obscured.
Bibliography
General Dynamics. (n.d.). Small Deep-Space Transponder (SDST). Retrieved 10 26, 2012, from General Dynamics: Advanced Information Systems: www.gd-ais.com/space
General Dynamics. (n.d.). Space Electronics: Mission Data Links. Retrieved 10 26, 2012, from X-Band Solid State Power Amplifier (SSPA): http://www.gd-ais.com/Products/Space-Electronics/Mission-Data-Links
NASA/California Institute of Technology. (2005, 12 05). Deep Space Network: FAQ. Retrieved 10 23, 2012, from Jet Propulsion Laboratory: http://deepspace.jpl.nasa.gov/dsn/faq-data.html
RUAG. (2009, 10). High Performance Reflector Antennas. Retrieved 10 24, 2012, from Satellite Communication Equipment - Antennas: http://www.ruag.com/space/Products/Satellite_Communication_Equipment/Antennas
RUAG. (2009, 10). Wide Coverage Antennas. Retrieved 10 24, 2012, from Satellite Communication Equipment - Antennas: http://www.ruag.com/space/Products/Satellite_Communication_Equipment/Antennas
(NASA/California Institute of Technology, 2005)
(RUAG, 2009) – Wide coverage antenna
(RUAG, 2009) – High-gain antenna
(General Dynamics) - SDST
(General Dynamics) - Amplifier
