SOHO shows First Signs of Ageing
20 June 2003
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.