SOHO’s orbit places the satellite in the perfect position to observe the sun and its influence on the Earth. It is situated around the first Lagrangian point L1, a point in space where the gravitational pull of the sun and of the Earth-moon system are in stable equilibrium. L1 is located approximately 1.5 million kilometres from the Earth along the Earth-sun axis (the total distance between Earth and the sun is 150 million kilometres). From this vantage point, the satellite has a permanent view of the sun, towards which it is pointed with very great accuracy while at the same time being sheltered against dynamic perturbations.
The specific advantages of this rather unusual orbit are that it allows the sun to be observed from outside the Earth’s magnetosphere (and thus without disturbing the solar wind), and at the same time avoid interruptions during periods when the sun is eclipsed by the Earth or the moon. As well as permitting more or less continuous observation of the sun, this places the satellite in a very stable thermal environment.
TECHNICAL DATA
The satellite is 3.8 metres high and has a wingspan of 9.5 metres with its solar panels deployed. Its launch weight was 1850 kilograms.
EADS Astrium is Europe’s leading satellite system specialist. Its activities cover complete civil and military telecommunications and Earth observation systems, science and navigation programmes, and all spacecraft avionics and equipment.
EADS Astrium is a wholly owned subsidiary of EADS SPACE, which is dedicated to providing civil and defence space systems. In 2004 EADS SPACE had a turnover of €2.6 billion and 11,000 employees in France, Germany, the United Kingdom and Spain.
EADS is a global leader in aerospace, defence and related services.
In 2004, EADS generated revenues of €31.8 billion and employed a workforce of more than 110,000.
Press contacts:
EADS SPACE (FR), Rémi ROLAND +33 (0) 1 42 24 27 34
EADS SPACE (GER), Mathias PIKELJ +49 (0) 7545 8 91 23
EADS SPACE (UK), Jeremy CLOSE +44 (0)14 3877 3872
http://www.space.eads.net
SOHO: lost and found Rescue mission at 1.5 million kilometres from the Earth
25 June 1998: SOHO has disappeared from the screens of the mission control team at the Goddard Space Center. It is impossible to re-establish contact with the satellite, which was launched two and a half years earlier and had been functioning perfectly up till now. Over the next 4 months, a team of a dozen Astrium engineers who had helped to build the satellite will work side by side with ESA and NASA experts in an attempt to recover the spacecraft.
During the first few weeks, the team elaborates a variety of hypotheses and scenarios that might be able to shed light on the satellite’s possible state and whereabouts, on the basis of the last known remote sensing data (at what speed and in which direction was it rotating around its axis, on what path is it drifting?).
At the instant it disappeared from view, its solar panels were no doubt perpendicular to the sun, but as the months go by the position of the satellite with respect to the sun will change, hopefully enabling the solar panels to capture light again, and thus supply the energy that is needed for a subsequent rescue mission.
On 23 July, the large radiotelescope at Arecibo in Porto Rico reports detecting a radar echo from SOHO.
