Spaceflight Now: Breaking News

SOHO sun-watching probe encounters new trouble
BY JUSTIN RAY
SPACEFLIGHT NOW

Posted: Dec. 1, 1999

  SOHO
Artist's conception of SOHO spacecraft in orbit. Photo: ESA
 
The joint U.S.-European solar probe SOHO lapsed back into an emergency safe mode Wednesday as controllers were trying to right the $1 billion craft.

The trouble began Sunday when one of the Solar and Heliospheric Observatory's attitude control units reset, causing the satellite to enter Emergency Sun Reacquisition mode. The ESR mode protects the observatory by keeping the solar panels pointed at the sun so onboard batteries can be recharged.

Officials still do not know what caused the control unit to reset, said Bernhard Fleck, European Space Agency's SOHO project scientist. A similar event occurred in November 1997, he said.

By Monday, controllers had commanded SOHO out of ESR and was making progress to return the observatory to normal operations.

But on Wednesday, as the probe was performing an orbital stationkeeping maneuver needed to properly point the observatory, a yet-unknown problem caused the onboard thrusters to shut down eight minutes into a planned 50-minute firing, Fleck said.

The craft was slowly rolling, which should not occur, and communications between the probe and Earth were lost. As SOHO reentered ESR mode, the satellite began transmitting via its low-gain antenna and contact with Earth was reestablished.

"We are analyzing telemetry and trying to determine what happened," Fleck said.

SOHO was launched four years ago Thursday aboard an Atlas rocket from Cape Canaveral Air Station in Florida.

Explore the Net
SOHO ESR status - Project's Web page providing summary of latest emergency mode aboard craft.

SOHO Web site - Solar and Heliospheric Observatory site with complete details on mission.

NewsAlert
Sign up for Astronomy Now's NewsAlert service and have the latest news in astronomy and space e-mailed directly to your desktop (free of charge).

Your e-mail address:

 


Station Calendar
NEW! This beautiful 12" by 12" wall calendar features stunning images of the International Space Station and of the people, equipment, and space craft associated with it, as it takes shape day by day in orbit high above the Earth.
 U.S. STORE
 U.K. & WORLDWIDE STORE

Baseball caps
NEW! The NASA "Meatball" logo appears on a series of stylish baseball caps available now from the Astronomy Now Store.
 U.S. STORE
 U.K. & WORLDWIDE STORE

INDEX | PLUS | NEWS ARCHIVE | LAUNCH SCHEDULE
ASTRONOMY NOW | STORE

ADVERTISE

© 2014 Spaceflight Now Inc.