SMOS mission overview
For optimum results, SMOS will measure microwave radiation emitted from Earth's surface within the L-band (1.4 GHz) using an interferometric radiometer.
Moisture and salinity decrease the emissivity of soil and seawater respectively, and thereby affect microwave radiation emitted from the surface of the Earth. Interferometry measures the phase difference between electromagnetic waves at two or more receivers, which are a known distance apart – the baseline.
The SMOS radiometer will exploit the interferometry principle, which by way of 69 small receivers will measure the phase difference of incident radiation. The technique is based on cross-correlation of observations from all possible combinations of receiver pairs. A two-dimensional 'measurement image' is taken every 1.2 seconds. As the satellite moves along its orbital path each observed area is seen under various viewing angles.
From an altitude of around 758 km, the antenna will view an area of almost 3000 km in diameter. However, due to the interferometry principle and the Y-shaped antenna, the field of view is limited to a hexagon-like shape about 1000 km across called the 'alias-free zone'. This area corresponds to observations where there is no ambiguity in the phase-difference.
SMOS will achieve global coverage every three days.
|Launched||2 November 2009|
|Duration||Minimum 3 years|
|Instrument||Microwave Imaging Radiometer using Aperture Synthesis - MIRAS|
|Instrument concept||Passive microwave 2D-interferometer|
|Frequency||L-band (21 cm-1.4 GHz)|
|Number of receivers||69|
|Receiver spacing||0.875 lambda = 18.37 cm|
|Polarisation||H & V (polarimetric mode optional)|
|Spatial resolution||35 km at centre of field of view|
|Tilt angle||32.5 degrees|
|Radiometric resolution||0.8 - 2.2 K|
|Angular range||0-55 degrees|
|Temporal resolution||3 days revisit at Equator|
|Instrument data rate||89 kbps H & V pol.|
|Mass||Total 658 kg launch mass comprising: platform 275 kg, payload 355 kg, fuel 28 kg|
|Orbit||Sun-synchronous, dawn/dusk, quasi-circular orbit at altitude 758 km. 06.00 hrs local solar time at ascending node.|
|Launcher||Rockot, KM-Breeze upper stage|
|Bus||Proteus (1 m cube)|
|Power||Up to 1065 W (511 W available for payload; 78 AH Li-ion battery.|
|Spacecraft Operations Control Centre||CNES,Toulouse, France|
|S-Band TTC link||4 kbps uplink, 722 kbps downlink|
|Payload Mission and Data Centre||ESAC, Villafranca, Spain|
|X-Band data downlink||16.8 Mbps|
Last update: 6 November 2013