Radio Science Subsystem
Encyclopedia
The Radio Science Subsystem (RSS) on a scientific spacecraft uses radio signals to probe a medium such as a planetary atmosphere. The spacecraft transmits a highly stable signal to ground stations, receives such a signal from ground stations, or both. Since the transmitted signal parameters are accurately known to the receiver, any changes to these parameters are attributable to the propagation medium or to the relative motion of the spacecraft and ground station.
The RSS is usually not a separate instrument; its functions are usually "piggybacked" on the existing telecommunications subsystem. More advanced systems use multiple antennas with orthogonal polarizations.
Radio science is commonly used to determine the gravity field of a moon or planet by observing Doppler shift. This requires a highly stable oscillator on the spacecraft, or more commonly a "2-way coherent" transponder that phase locks the transmitted signal frequency to a rational multiple of a received uplink signal that usually also carries spacecraft commands.
Another common radio science observation is performed as a spacecraft is occulted by a planetary body. As the spacecraft moves behind the planet, its radio signals cuts through successively deeper layers of the planetary atmosphere. Measurements of signal strength and polarization vs time can yield data on the composition and temperature of the atmosphere at different altitudes.
It is also common to use multiple radio frequencies coherently derived from a common source to measure the dispersion of the propagation medium. This is
especially useful in determining the free electron content of a planetary ionosphere.
Spacecraft using RSS
The RSS is usually not a separate instrument; its functions are usually "piggybacked" on the existing telecommunications subsystem. More advanced systems use multiple antennas with orthogonal polarizations.
Radio science is commonly used to determine the gravity field of a moon or planet by observing Doppler shift. This requires a highly stable oscillator on the spacecraft, or more commonly a "2-way coherent" transponder that phase locks the transmitted signal frequency to a rational multiple of a received uplink signal that usually also carries spacecraft commands.
Another common radio science observation is performed as a spacecraft is occulted by a planetary body. As the spacecraft moves behind the planet, its radio signals cuts through successively deeper layers of the planetary atmosphere. Measurements of signal strength and polarization vs time can yield data on the composition and temperature of the atmosphere at different altitudes.
It is also common to use multiple radio frequencies coherently derived from a common source to measure the dispersion of the propagation medium. This is
especially useful in determining the free electron content of a planetary ionosphere.
Spacecraft using RSS
- Cassini–Huygens
- Mariner 2Mariner 2Mariner 2 , an American space probe to Venus, was the first space probe to conduct a successful planetary encounter . The first successful spacecraft in the NASA Mariner program, it was a simplified version of the Block I spacecraft of the Ranger program and an exact copy of Mariner 1...
, 4,5,6,7,9, and 10 - VoyagerVoyager-Technology:*LG Voyager, a mobile phone model manufactured by LG Electronics*NCR Voyager, a computer platform produced by NCR Corporation*Voyager , a computer worm affecting Oracle databases...
1 and 2 - MESSENGERMESSENGERThe MErcury Surface, Space ENvironment, GEochemistry and Ranging space probe is a robotic NASA spacecraft in orbit around the planet Mercury. The spacecraft was launched aboard a Delta II rocket in August 2004 to study the chemical composition, geology, and magnetic field of Mercury...
- Venus ExpressVenus ExpressVenus Express is the first Venus exploration mission of the European Space Agency. Launched in November 2005, it arrived at Venus in April 2006 and has been continuously sending back science data from its polar orbit around Venus. Equipped with seven science instruments, the main objective of the...
Functions
- Determine composition of gas clouds such as atmospheres, solar coronas.
- Characterize gravitational fields
- Estimate masses of celestial satellites that do not have satellites of their own.
- To estimate particle size of particle fields
- Estimate densities of ion fields.
Specifications
- Given a deep space networkDeep Space NetworkThe Deep Space Network, or DSN, is a world-wide network of large antennas and communication facilities that supports interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected...
(DSN) of receivers and/or transmitters. - A Ka-band traveling wave tube amplifier (K-TWTA) amplifies signals to a transmitting antenna to be received by a distal radio- telescope.
- Ka-band translator (KAT) receives signal from a high-gain antenna and retransmits the signal back to DSN. In this way the phase and phase-shift resulting from signal modification
- Ka-band exciter (KEX) it supplies telemetry data.
- S-band transmitter is used for radio science experiments. The transmitter receives signal from the RFS, amplifies and multiplies the signal, sending a 2290 MHz signal to the antenna.
- Filter microwave emitter allow only microwaves of a given frequency to be emitted, there is a polarizing element. There are two-bypass filters and a wave-guide. The bypass filters allow different feed polarizations, receiving and transmitting.