An artist's rendering of Satellite with ARgos and ALtika - SARAL
|Mission type||Remote sensing|
|Mission duration||5 years (ARGOS)|
3 years (AltiKa)
|Manufacturer||ISRO Satellite Centre|
|Launch mass||407 kilograms (897 lb)|
|Start of mission|
|Launch date||25 February 2013, 12:31UTC|
|Launch site||Satish Dhawan FLP|
|Perigee altitude||790 kilometres (490 mi)|
|Apogee altitude||791 kilometres (492 mi)|
|Epoch||30 October 2013, 02:13:46 UTC|
|ALTIKA, DORIS, LRA, ARGOS-3|
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 performs altimetric measurements designed to study ocean circulation and sea surface elevation.
The payload modules were provided by CNES: ALTIKA (altimeter), DORIS, Laser Retro-reflector Array (LRA), and ARGOS-3 (Advanced Research and Global Observation Satellite) data collection system. ISRO is responsible for the platform (Indian Mini Satellite-2 bus), launch (Polar Satellite Launch Vehicle rocket), and operations of the spacecraft. SARAL was successfully launched into a Sun-synchronous orbit (SSO) on 25 February 2013, 12:31 UTC.
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.
ALTIKA, the altimeter and prime payload of the SARAL mission, is the first spaceborne altimeter to operate at Ka band. It was built by the French National Space Agency CNES. The payload is intended for oceanographic applications, operates at 35.75 GHz. 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.
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 around this problem by operating at a high frequency in Ka band. Another 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. (Although this could be exploited to perform crude measurements of precipitation).
It built by the French National Space Agency CNES. ARGOS contributes to the development and operational implementation of the global ARGOS Data Collection System. It will collect a variety of data from ocean buoys to transmit the same to the ARGOS ground segment for subsequent processing and distribution.
SARAL data products will be useful for operational as well as research user communities in many fields like