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ESA Science News
http://sci.esa.int

20 Jun 2003

SOHO shows first sign of aging

The ESA/NASA SOHO spacecraft, launched in 1995, has been delivering
outstanding data about the Sun for over eight years. Recently,
however, an anomaly on the pointing mechanism of its high-gain
antenna has been recorded. 

The high-gain antenna is required to transmit the large amounts of
data from SOHO's scientific observations to Earth. From SOHO's orbit,
the antenna has to be pointed in the proper direction -- like a
flashlight -- for the data to be received at Earth.

The exact nature of the antenna problem is not yet known, but the
experts think that a malfunction has occurred in its motor or in the
gear assembly that steers the antenna.

SOHO is safe, as the spacecraft has a low-gain antenna, used to
control the spacecraft and monitor both spacecraft and instrument
health and safety, which remains operational. However, if the
high-gain antenna problem persists, there will be periodic losses in
the real-time transmission of scientific data of about two and a half
weeks each three months. The first blackout is estimated to begin
sometime late in the week of 22 June 2003. 

A number of options are currently being investigated by the SOHO team
to fully recover or minimise any real-time scientific data loss. A
joint ESA/NASA press release will follow shortly.

USEFUL LINKS FOR THIS STORY

* More about SOHO
   http://sci.esa.int/soho/

SOHO is stationed 1.5 million kilometres away from the Earth,
directly in line of the Sun. There, it constantly watches the Sun for
activity, returning spectacular pictures and data of the storms that
rage across its surface. SOHO was launched in 1995 by a NASA
Atlas-IIAS/Centaur rocket and was designed to work for three years.
It is still working today.

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