 | | | | |
| | | | | |
|
| ESA's water mission SMOS Science Mission Data Publications Services CalendarSubscribeContact us
| | | | | | | SMOS mission overview
SMOS measurement principle
For optimum results, SMOS will measure microwave radiation emitted from Earth's surface within the L-band (1.4 GHz) using an interferometric radiometer.
Measurement principles
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.
Interferometry principle
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.
Mission approach
| Mission | SMOS |
| 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: 2 November 2009 | |
| | SMOS launch Track SMOS Access SMOS data More information SMOS - ESA's water mission (BR-288)SMOS - la misión del agua de la ESA
(BR-278)SMOS – mission de l'ESA dédiée au cycle de l'eau (BR-278)SMOS factsheetSpecial features  SMOS: ESA's water missionFrom a technological perspective Technology leaps let SMOS follow Earth’s waterRelated links Thales Alenia SpaceCNESEADS-CASACESBIO SMOS pageIfremer-Cersat Salinity CenterGerman SMOS Project OfficeSMOS Barcelona Expert CentreSMOS Level 3/4 Processing Centre, SpainInternational Soil Moisture Network
|
