Jason-2 carries five payload instruments and three 'passenger' instruments.
The lightweight platform (500 kilos at launch) is known as the 'Platforme Reconfigurable pour l'Observation, les Telecommunications Et les Usages Scientifiques' or PROTEUS. The three-axis stabilisation and nadir pointing is maintained by reaction wheels and magnetic torque rods.
See the Animation on Jason-2 instruments
Further details can be found in the Radar Altimetry Tutorial
Poseidon-3 (supplied by CNES) is the mission's main instrument, derived from the Poseidon-2 altimeter on Jason-1. It is a compact, low-power, low-mass instrument offering a high degree of reliability.
Poseidon-3 is a radar altimeter that emits pulses at two frequencies, 13.6 GHz (Ku-band) and 5.3 GHz (C-band), and analyses the return signal reflected by the surface. The signal round-trip time is estimated very precisely, to calculate the range after applying corrections.
The primary goal of the dual-frequency operation is to provide a precise ionospheric correction. Besides a differential ionospheric path delay, Ku- and C-band signals are differentially and significantly affected by geophysical quantities, such as atmospheric precipitation and sea surface roughness.
Advanced Microwave Radiometer (AMR)
The AMR, supplied by NASA, measures radiation from the Earth's surface at three frequencies (18, 21 and 37 GHz). These different measurements are combined to determine atmospheric water vapour and liquid water content. Once the water content is known, it is possible to determine the correction to be applied for radar signal path delays.
Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS)
DORIS, supplied by CNES, uses a ground network of 60 orbitography beacons around the globe, which send signals, in two frequencies, to a receiver on the satellite.
The relative motion of the satellite generates a shift in the signal's frequency (called the Doppler shift) that is measured to derive the satellite's velocity. These data are then assimilated in orbit determination models to keep permanent track of the satellite's precise position (within 3 cm) in its orbit.
Global Positioning System Payload (GPSP)
The NASA-supplied GPSP (Global Positioning System Payload), uses the Global Positioning System (GPS) to determine the satellite's position by triangulation. At least three GPS satellites are needed to establish the satellite's exact position at a given instant. Positional data are then integrated into an orbit determination model to continuously track the satellite's trajectory.
Laser Retroreflector Array (LRA)
The LRA, supplied by NASA, is an array of mirrors that provide a target for laser tracking measurements from the ground. By analysing the round-trip time of the laser beam, we can locate where the satellite is in its orbit and calibrate altimetric measurements.
- Environment Characterization and Modelisation-2 (Carmen-2) — studies radiation in the satellite environment (supplied by France.
- Light Particle Telescope (LPT) — studies radiation in the satellite environment (supplied by Japan).
- Time Transfer by Laser Link (T2L2) — consists of detectors for ultra-precise time transfer. T2L2 uses a laser link for high accuracy comparison and synchronisation of remote ground clocks (supplied by France) .