SOHO spacecraft
Science & Exploration

19 June

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ESA / Science & Exploration / Space Science

2003: On 19 June 2003, the high-gain antenna (HGA) on ESA's SOHO spacecraft suffered a malfunction in its pointing mechanism - a stuck motor drive would not permit the antenna to move.

The HGA, which transmits high-speed data to Earth, became fixed in position. After this, astronomers had to rely on a slower transmission-rate signal, sent through SOHO's back-up antenna. However, this signal could not transmit all of SOHO's scientific data.

SOHO orbits a point in space, 1.5 million kilometres closer to the Sun than the Earth, once every six months. To re-position the HGA for the next half of this orbit, engineers rolled the spacecraft through a half-circle on 8 July 2003. On 10 July, the 34-metre radio dish in Madrid re-established contact with SOHO's HGA. Then on the morning of 14 July 2003, normal operations with the spacecraft resumed through its usual 26-metre ground stations, as predicted.

With the HGA now static, the blackouts from the HGA lasting between 9 and 16 days, continued to occur every three months. Engineers rotated SOHO by 180 degrees every time this occurred and this manoeuvre minimised data losses.

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