Jason-1
The Jason-1 satellite, a follow-on mission to TOPEX-Poseidon, was the first spacecraft to use the Proteus minisatellite bus, built in France through a collaboration of CNES, EUMETSAT, and NOAA.
Jason-1 carried five instruments: the Poseidon-2 altimeter, the mission’s main instrument, which measures sea level (the distance between the spacecraft and the Earth’s surface); the Jason Microwave Radiometer (JMR) which measures water vapor and liquid water content in the atmosphere; and three location systems: DORIS, LRA and TRSR.
DORIS
The DORIS instrument onboard Jason-1 provided real-time location and precise orbit determination. DORIS measurements are also used for geophysical studies, in particular through the International DORIS Service (IDS). DORIS is a dual-frequency instrument able to determine atmospheric electron content.
DORIS orbitography beacons transmit signals at two separate frequencies (2036.25 MHz and 401.25 MHz) to the satellite. The receiver onboard the satellite analyzes the received signal frequencies to calculate its velocity relative to Earth. This velocity is fed into orbit determination models to derive the satellite's position on orbit to within 2 centimeters on the radial component.
LRA - Laser Retroreflector Array
The Jason-1 LRA is used to calibrate the other location systems on the satellite with a very high degree of precision. It is a totally passive reflector designed to reflect laser pulses back to their point of origin on Earth. It consists of nine suprasil quartz retroreflectors arranged to provide a near-hemispherical response. The LRA allows the Jason-1 spacecraft to be tracked with centimeter accuracy by approximately 10-20 satellite laser ranging (SLR) stations which make up the International Laser Ranging Service (ILRS).
The small number of ground stations and the sensitivity of laser beams to weather conditions make it impossible to track the satellite continuously. That is why other onboard location systems are needed.
GPS - Global Positioning System
The Turbo Rogue Space Receiver (TRSR) is a high performance GPS receiver designed to provide backup precise orbit determination for Jason-1. It measures precise GPS "pseudorange" and continuous carrier phase data from up to 12 GPS satellites. The TRSR views the GPS satellites through an up-looking antenna which provides a nearly hemispherical field of view. There were two complete redundant TRSR systems carried on Jason-1.
Data from the TRSR are analyzed in post processing to produce continuous Jason-1 orbits.