SARAL |
|
| Operator | ISRO and CNES |
|---|---|
| Major contractors | ISRO Satellite Centre, CNES |
| Mission type | Earth sensing |
| Launch date | Early 2011 |
| Carrier rocket | PSLV |
| Launch site | Satish Dhawan Space Centre |
| Mission duration | 5 years (ARGOS); 3 years (AltiKa) |
| Mass | <450 kg[1] |
| Power | TBD |
| Batteries | TBD |
| Orbital elements | |
| Inclination | 98.55° (planned) |
| Altitude | 814 km |
| Instruments | |
| Main instruments | AltiKa, DORIS, LRA, ARGOS-3 |
| Transponders | |
| Transponders | Ka band 35 GHz[2] |
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). The ISRO built satellite with payloads modules (AltiKa altimeter, DORIS, Laser Retroreflector Array (LRA) and ARGOS-3 (Advanced Research and Global Observation Satellite) data collection system provided CNES will be launched by Indian Polar Satellite Launch Vehicle rocket into the Sun-synchronous orbit (SSO). ISRO will be responsible for the platform, launch, and operations of the spacecraft. A CNES/ISRO MOU (Memorandum of Understanding) on the SARAL mission was signed on Feb. 23, 2007.[3][1]
The SARAL satellite, carrying AltiKa and an Argos-3 instrument2, is scheduled to be launched in early 2011.[4][5]
The SARAL mission is complementary to the Jason-2 mission of NASA/NOAA and CNES/EUMETSAT. It will fill the gap between Envisat and the Sentinel 3 mission of the European GMES program. The combination of two altimetry missions in orbit has a considerable impact on the reconstruction of sea surface height (SSH), reducing the mean mapping error by a factor of 4.[6]
AltiKa, the altimeter and prime payload of the SARAL mission, will be the first spaceborne altimeter to operate at Ka band. AltiKa is set to take over ocean-monitoring from Envisat. It is the first to operate at such a high frequency, making it more compact and delivering better performance than the previous generation.[7]
While existing satellite-borne altimeters determine sea level by bouncing a radar signal off the surface and measuring the return-trip time, AltiKa operates at a high frequency in Ka band. The advantage of this is twofold. One, the earth’s atmosphere slows down the radar signal, so altimetry measurements are skewed and have to carry additional equipment to correct for this error. Since AltiKa uses a different system, it does not have to carry an instrument to correct for atmospheric effects as current-generation altimeters do.
AltiKa gets round this problem by operating at a high frequency in Ka band, which also means it doesn’t have to carry an instrument to correct for atmospheric effects as current-generation altimeters do
The second advantage of operating at higher frequencies is greater accuracy. AltiKa will measure ocean surface topography with an accuracy of 8 mm, against 2.5 cm on average using current-generation altimeters, and with a spatial resolution of 2 km.
The disadvantage, however, is that high-frequency waves are extremely sensitive to rain, even drizzle. 10% of the data is expected to be lost.