The scientific objectives of JASON-1 are:

Oceanography and ocean forecasting: Ocean variability is the central focus of the Jason-1 mission. The satellite's orbit-identical to Topex/Poseidon-has been defined to cover 90% of the world's ice-free oceans every ten days. Real-time data delivery will make it possible to issue ocean bulletins in much the same way as we do weather forecasts today.
Climatology and climate prediction: Altimetric data yield vital information for studying and predicting climate, in particular climatic phenomena such as El Niñño. Jason-1's ability to measure mean sea level with millimetre accuracy will be a key asset for monitoring climate change.
Marine meteorology: Jason-1 will deliver sea-state data (wave heights and wind speed) within three hours. This information will help us to better understand and predict weather conditions over the oceans.
Geophysics: The Earth's gravity field affects sea level. By measuring the ocean's dynamic topography, we can learn more about plate tectonics, bottom topography, movements of the Earth's mantle and many other geophysical phenomena. Altimetric data are also used to study ice, lakes and rivers, and relief in desert zones.

To fulfill these scientific objectives, the payload consist in the following subsystems :

Poseidon-2 altimeter: Poseidon-2 is the mission's main instrument. Poseidon-2 is a radar altimeter that emits pulses at two frequencies (13.6 and 5.3 GHz, the second frequency is used to determine the electron content in the atmosphere) and analyses the return signal reflected by the surface. The signal's round-trip time is estimated very precisely in order to calculate the range, after applying the necessary corrections (Instrument supplied by CNES).
JMR (Jason-1 Microwave Radiometer): This instrument measures radiation from the Earth's surface at three frequencies (18, 21 and 37 GHz). Measurements acquired at each frequency are combined to determine atmospheric water vapour and liquid water content. Once the water content is known, we can determine the correction to be applied for radar signal path delays (Instrument supplied by NASA).
DORIS (Doppler location): This system uses a ground network of orbitography beacons spread around the globe, which send signals at 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 (to within three centimetres) on its orbit (Instrument supplied by CNES).
TRSR (Turbo Rogue Space Receiver): It uses the Global Positioning System (GPS) to determine the satellite's position by triangulation, in the same way that GPS fixes are obtained on Earth. At least three GPS satellites determine a mobile object's (in this case, the satellite's) exact position at a given instant. Positional data are then integrated into an orbit determination model to track the satellite's trajectory continuously (Instrument supplied by NASA).
LRA (Laser Retroreflector Array: laser tracking): It 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 on its orbit (Instrument supplied by NASA).

JASON-1 flies on the same orbit than TOPEX/POSEIDON to ensure a continuity and an optimal inter comparison for long term observations. The data processing is integrated to the Cnes "SALP" (Système d'Altimétrie et de Localisation Précise) Ground Segment, which already operates TOPEX/POSEIDON, ENVISAT, GFO altimetry missions, which data are distributed on AVISO web site.