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Contact Lost With SOHO Spacecraft

Looks like we lost SOHO. That is too bad.  SOHO had discovered about
50 new sun-grazing comets.

Ron Baalke
----------------------------------------------------------------------

Don Savage
Headquarters, Washington, DC                      June 26, 1998
(Phone:  202/358-1727)

Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5017)

Franco Bonacina
European Space Agency Headquarters, Paris, France
(Phone:  33-1-5369-7713)

RELEASE:  98-112

SOHO SPACECRAFT OBSERVATIONS INTERRUPTED

       Ground controllers lost contact with the NASA/European Space 
Agency (ESA) Solar and Heliospheric Observatory (SOHO) spacecraft June 
24 during maintenance operations.

     SOHO went into emergency sun reacquisition mode, and ground 
controllers lost contact with the spacecraft at 7:16 p.m. EDT on June 
24.  This mode is activated when an anomaly occurs and the spacecraft 
loses its orientation toward the Sun.  When this happens, the spacecraft 
automatically tries to point itself toward the Sun again by firing its 
attitude control thrusters under the guidance of an onboard Sun sensor.   

       Efforts to re-establish contact with SOHO did not succeed and 
telemetry was lost.  Subsequent attempts using the full NASA Deep Space 
Network capabilities have so far also not been successful.

       Engineers from NASA and ESA are attempting to reestablish contact 
with the spacecraft.  

       SOHO is a joint mission of the European Space Agency and NASA.  
It was launched aboard an Atlas IIAS rocket from Cape Canaveral Air 
Station, FL, on Dec. 2, 1995, and mission operations are directed from 
NASA's Goddard Space Flight Center, Greenbelt, MD.

       In April 1998, SOHO successfully completed its nominal two-year 
mission to study the Sun's atmosphere, surface and interior.  Major 
science highlights include the detection of rivers of plasma beneath the 
surface of the Sun; the discovery of a magnetic "carpet" on the solar 
surface that seems to account for a substantial part of the energy that 
is needed to cause the very high temperature of the corona, the Sun's 
outermost layer; the first detection of flare-induced solar quakes; the 
discovery of more than 50 sungrazing comets; the most detailed view to 
date of the solar atmosphere; and spectacular images and movies of 
coronal mass ejections, which are being used to improve the ability to 
forecast space weather.

       More information and images from SOHO can be found on the 
Internet at:
                 http://sohowww.nascom.nasa.gov/

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