spacetoday.net: Partial solution found for SOHO antenna problem

Posted: Fri, Jul 4, 2003, 9:37 AM ET (1337 GMT)
SOHO spacecraft illustration (ESA)

Engineers have found a partial fix to the high-gain antenna problem with the NASA-ESA Solar and Heliospheric Observatory (SOHO) spacecraft by using larger ground antennas to receive signals from the spacecraft, project officials reported this week. SOHO has experienced a problem for several weeks with the motor that points its high-gain antenna towards Earth; without it, the spacecraft has blackout periods when that antenna no longer is aimed at Earth. However, engineers have found a way to use 34- and 70-meter antennas on Earth to receive medium- and high-rate data transmitted by the spacecraft's omnidirectional low-gain antenna, normally used only for spacecraft telemetry in emergencies. This solution reduces the spacecraft blackout period to "moderate fractions per day" rather than a continuous 2-3 weeks. Instruments on the spacecraft that had been put into safe mode in late June in preparation for the blackout period are running again, and the high-gain antenna will be usable again around July 14, after the spacecraft performs a 180-degree maneuver on July 8 to reorient the antenna towards Earth. Engineers also continue to look for ways to fix the problem with the antenna motor.