SMOS SMOS mission satellite   Proteus - deployment of solar arrays   The SMOS instrument MIRAS is carried on a standard 'spacecraft' bus called Proteus, which was developed by the French space agency CNES (Centre National d'Etudes Spatiales) and Alcatel Alenia Space. It is a generic platform with well-defined interfaces so that with a little modification, the SMOS scientific instrument was mounted on the top of the spacecraft through four interface pods.   Although the spacecraft bus is small, measuring just one cubic metre, it acts as a service module accommodating all the subsystems that are required for the satellite to function.       SMOS orbital path     After launch, when the spacecraft separateded from the launcher, there was an automatic start-up sequence, which resulted in the deployment of two symmetrical solar arrays. A Sun-synchronous, dawn-dusk orbit is required to obtain the optimum data on soil moisture and ocean salinity. The solar arrays will always be illuminated, except for short eclipse periods in winter.     Proteus uses a GPS receiver for orbit determination and control, which provides satellite position information, and a hydrazine monopropellant system for four 1-Newton thrusters that are mounted on the base of the spacecraft. Nominal attitude control is based on a gryo-stellar concept. The Star Tracker is accommodated on the payload and provides accurate attitude information for both the instrument measurements and the satellite attitude control. Three 2-axis gyroscopes are used to measure the change in the spacecraft orientation, and thus provide the accurate attitude knowledge needed to fulfil stability and pointing requirements. Four small reaction wheels generate torque for attitude adjustment. In safe mode, a less precise attitude is maintained using magnetic and solar measurements, namely with two 3-axis magnetometers and eight coarse Sun sensors, while magnetotorquers act as the only actuators.       Fairing opening during launch sequence   SMOS was launched by one of the modified Russian Intercontinental Ballistic Missile (ICBM) SS-19 launchers, which were decommissioned as a consequence of the Strategic Arms Reduction Treaty (START). Launch was from the Plesetsk Cosmodrome in northern Russia on 2 November 2009.       Last update: 2 November 2009  •  SMOS launch (http://www.esa.int/SPECIALS/smos/index.html)  •  Track SMOS (http://www.esa.int/esaLP/SEMF4965P1G_LPsmos_0.html)  •  Access SMOS data (http://earth.esa.int/SMOS/) More information  •  SMOS - ESA's water mission (BR-288) (http://esamultimedia.esa.int/multimedia/publications/BR-288/pageflip.html)  •  SMOS - la misión del agua de la ESA (BR-278) (http://esamultimedia.esa.int/docs/SMOS/SMOS(Spanish)_28.9.pdf)  •  SMOS – mission de l'ESA dédiée au cycle de l'eau (BR-278) (http://esamultimedia.esa.int/docs/SMOS/BR-278_French_web.pdf)  •  SMOS factsheet (http://esamultimedia.esa.int/docs/SMOS/SMOS_factsheet_22Jun09.pdf) Special features  •  SMOS: ESA's water mission (http://download.esa.int/mpeg/smos_web_movie.mpg) From a technological perspective  •  Technology leaps let SMOS follow Earth’s water (http://www.esa.int/SPECIALS/Technology/SEM7I5XRA0G_0.html) Related links  •  Thales Alenia Space (http://www.thalesgroup.com/)  •  CNES (http://www.cnes.fr/web/CNES-en/455-cnes-en.php)  •  EADS-CASA (http://www.eads.net/1024/en/casa/casa.html)  •  CESBIO SMOS page (http://www.cesbio.ups-tlse.fr/us/indexsmos.html)  •  Ifremer-Cersat Salinity Center (http://www.salinityremotesensing.ifremer.fr/home)  •  German SMOS Project Office (http://www.smos.zmaw.de)  •  SMOS Barcelona Expert Centre (http://www.smos-bec.icm.csic.es/)  •  SMOS Level 3/4 Processing Centre, Spain (http://www.cp34-smos.icm.csic.es/)  •  International Soil Moisture Network (http://www.ipf.tuwien.ac.at/insitu/)