Deep Space 1 Mission Status

Mike DiMuzio (
Thu, 12 Nov 1998 00:42:54 +0000

PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

                Deep Space 1 Mission Status
                    November 11, 1998

     After operating as expected for approximately 4-1/2 minutes
after startup Tuesday, November 10, Deep Space 1's xenon ion
engine turned off for reasons that are still under investigation.
After the startup at 11:30 a.m. PST and subsequent shutdown
Tuesday, the operations team sent a number of commands to try to
restart the ion propulsion system.  Each time, the system went
through its normal startup routine, but was unable to achieve
thrusting. Valuable diagnostic data were collected, and the team
observed that the rest of the spacecraft behaved exactly as
planned during the brief interval of thrusting and during
subsequent attempts to restart the thruster.

     Engine turn-off behavior has been observed in the past in
solar electric propulsion systems both in Earth-based test and on
Earth-orbiting spacecraft.  Deep Space 1 is designed to test and
validate the use of such propulsion in deep space for the first
time, so the ongoing diagnosis of Tuesday's behavior is in
keeping with the mission's goals.

     Tuesday's planned activities had included stepping up the
thruster through different throttle levels over more than 16
hours, taking the engine to its peak thrusting level.  This would
allow the team to assess the overall performance of the
spacecraft and the ion propulsion system at increasingly powerful
levels and to measure the power needed from the spacecraft's pair
of solar arrays to achieve each thrust level. Concurrently,
ground-based radio navigation was to take Doppler data to measure
the amount of thrust imparted by the ion engine system at each
throttle level.  These activities will be conducted once the
resolution of Tuesday's premature shutdown is found.

     Today, other technology validation activities will continue
while a portion of the team analyzes Tuesday's data and
formulates a plan for subsequent ion propulsion system
operations. Much of the key testing will be completed within the
first eight weeks after launch; the technologies on which the
spacecraft depends for its basic operation -- such as its solar
arrays and the transponder or radio transmitter/receiver -- were
proven to work within the first hours after launch.

     To prepare for Tuesday's planned activities, the spacecraft
successfully executed a large turn Friday, October 30, to point
the ion engine toward the Sun. Sunlight heated portions of the
xenon feed system and the ion thruster core (which reached about
110 C (230 F)), and baked off some contaminants that held the
potential to interfere with the engine's operation. While the
spacecraft remained in that orientation, a small amount of xenon
from the ion propulsion system was allowed to flow through the
system to assure there were no blockages. The spacecraft returned
to its previous orientation the next day.

     On Thursday, November 5, a heater inside the thruster's
cathode was turned on and the xenon system was pressurized. As a
final test before thrusting, xenon was ionized inside the
thruster on Monday, November 9, but was not accelerated.
Engineering data show that the test went as planned. The suite of
diagnostic sensors onboard to measure the effects of the ion
propulsion system on the local space environment worked as

     Once Tuesday's behavior is diagnosed and resolved, the
engine is scheduled to be turned on intermittently for the
remainder of the mission, which ends in late September 1999.

     The ion engine is among 12 technologies being tested on Deep
Space 1, the first mission of the New Millennium Program,
designed to validate new technologies so that they may be used on
space missions of the 21st century.



Mike DiMuzio