SARAL Satellite

SARAL or Satellite with ARgos and ALtiKa is a cooperative altimetry technology mission of Indian Space Research Organisation (ISRO) and CNES (Space Agency of France).

Saral will embark the AltiKa altimeter (working in Ka-band, 35 GHz), built by CNES, as well as a Doris instrument. Signal frequencies in the Ka-band will enable better observation of ice, rain, coastal zones, land masses (forests, etc.), and wave heights.

Its objectives are:

1. To carry out precise, repetitive global measurements of sea surface height, significant wave heights and wind speed, for:
2. developing operational oceanography;
3. improving understanding of the climate and developing forecasting capabilities;
4. Operational meteorology.
5. To ensure, in association with Jason-2, the continuity of the service currently provided by the altimeters onboard Envisat and Jason-1,
6. To meet the requirements expressed by various international ocean and climate study programmes, and contribute to building a global ocean observing system.

Payload developed by CNES composed of the following instruments:
a) AltiKa:

AltiKa is a Ka-band altimeter (35 GHz) developed by CNES. It is aiming to observe the ocean in as much detail and as accurately as current missions, only at lower cost, by flying the altimeter on a microsatellite that is cheaper to design, build and launch. Experience has shown that an altimetry platform must comprise an altimeter, radiometer and precise orbit determination system, with sufficient redundancy, as well as enough fuel to keep the satellite orbiting on a repeating ground track - at least with a 'conventional' altimetry mission.

The AltiKa altimeter will be a single-frequency Ka-band altimeter (operating at 35.75 GHz, weighing less than 20 kg and consuming less than 50 Watts). Alcatel Space developed a Ka-band altimeter between 1998 and 2000 which was based on the same technologies as those used for the Poseidon-1 and Poseidon-2 altimeters.

b) DORIS System

Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) is a French satellite system used for the determination of satellite orbits and for positioning. It is based on the principle that, a beacon is installed on the ground and emits a radio signal, which is received by the satellite. A frequency shift of the signal occurs that is caused by the movement of the satellite (Doppler Effect). From this observation satellite orbits, ground positions, as well as other parameters can be derived.

c) LRA (Laser Retro-reflector Array) instrument

It is used for precise calibration of other Polar Orbital Data (POD) instruments, through analysis of laser shots from the ground then reflected by the LRA mirrors.

d) ARGOS-3 instrument

ARGOS-3 is an element of the ARGOS system, dedicated to localization, acquisition and distribution of environmental data.

SARAL Satellite main features
Mass	350/400 kg platform: ~200 kg payload module: <165 kg="" span="">
Total power	570 W platform: ~205 W payload: ~195 W
Size	0.98 m x 0.98 m x 2.6 m solar panels: 1.2 m x 1.4 m (2x)
Data rate S-band	64 kbits/s for telemetry, 4 kbits/s for telecommande
Mission lifetime	5 years for ARGOS 3 years for AltiKa

The satellite will be put into orbit by a PSLV vehicle supplied by ISRO, and launched from the main ISRO launch base, the Satish Dhawan Space Centre, 100 km North from Chennai.