baalke@mars.jpl.nasa.gov (Ron Baalke) (01/19/90)
GALILEO MISSION STATUS
January 17, 1990
Today the Galileo spacecraft is just under 18 million miles
from Earth, and 8.7 million miles from Venus. Round-trip light
time to the spacecraft is about 3-1/4 minutes. During the next
week or so, there will be an approximate line-up between the Sun,
Venus, Galileo, the Earth and Jupiter. (Jupiter was at opposition
two weeks ago, and the spacecraft is several degrees above the
ecliptic plane.) Galileo has rolled up 141 million miles around
its orbit, at a velocity which has increased to 75,600 mph, and
with 44 million to go before Venus encounter February 9 at 10
p.m. PST.
The health of the spacecraft is very good; it is in a
"safed" cruise mode following an incident Monday in which the
attitude control computer invoked system fault protection
because of an incompatibility found while performing a star
calibration with the gyros off. The flight team analyzed the
incident quickly and are now working to gradually restore
various functions which were halted automatically during the
"safing" response. The spacecraft is spinning in all spin
mode at 2.89 rpm, and sending telemetry at 1200 bits per second.
On January 9, Galileo had its first demonstration
of "Delta DOR," a Very Long Baseline Interferometry technique
using two DSN stations simultaneously to produce very precise
angle tracking data. This will be added to doppler and
ranging to refine spacecraft navigation for the Earth and
Jupiter encounters, to improve targeting while saving
propellant. The DSN's large antenna in Spain, DSS-63, has
been down for several weeks to replace a bearing. Repairs
are progressing and the antenna is expected to be operating
in time for Venus encounter.
Last week the Project determined that no further
trajectory correction is needed for the Venus flyby; there
will be no TCM-3. Venus encounter and science will be part
of the operating sequence called EV-6, which will be
effective February 5-18.
Ron Baalke | baalke@mars.jpl.nasa.gov
Jet Propulsion Lab M/S 301-355 | baalke@jems.jpl.nasa.gov
4800 Oak Grove Dr. |
Pasadena, CA 91109 |