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.


* More about SOHO

Artist’s impression of 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.