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STARDUST Update - May 28, 1999

                       STARDUST STATUS REPORT
                           May 28, 1999

The STARDUST spacecraft and subsystems continue to perform nominally as
flight sequence SC005 started on Tuesday when the spacecraft was 1.4 AU 
from the Sun and 0.4 AU from Earth.  Both the University of Chicago Dust
Flux Monitor Instrument (DFMI) and the Max Planck Institute Cometary
and Interstellar Dust Analyzer (CIDA) continue to be pointed into the
interstellar dust stream.

With only one communication session per week, the flight team at
Lockheed Martin Astronautics (LMA) determined that CIDA had rebooted
itself late last week and was operating nominally within its rebooted
state, which is not its operational state.   During the communication 
session, sufficient time was not available to transmit all CIDA data 
down and the data around the time of reboot still remains on the spacecraft.
Commands will be sent to download the remaining CIDA data and also set 
CIDA back to its operational mode late next week.

LMA also observed that the Solid State Power Amplifier (SSPA) started
to show signs of trapped charges again where the SSPA exhibits low
amplitude variations in gain and temperature (~2 dB in signal strength
and 4 degrees C), within nominal operating values.  Concern exists that 
over the 7 year mission lifetime this behavior could reduce the reliability 
of the SSPA.  The project is therefore considering powering off the SSPA
during non-contact time periods (over 90% of the time) starting in
flight sequence SC006, allowing the trapped charges to dissipate as was
successfully done previously by power cycling the SSPA.

A team of DFMI, LMA and JPL experts was formed to analyze the DFMI
anomalous behavior which occurred a few weeks ago after which the DFMI
was powered off and remains off.  The symptoms of the DFMI behavior
resemble a "galloping" power converter which causes large amplitude and
high frequency changes to the output power.  Detail circuit modeling
studies and tests of the engineering unit in a varying thermal
environment are underway.  The DFMI operated nominally for 2 months at
near room temperature.  The temperature dropping to -20 degrees C a
few weeks ago when the spacecraft was turned to point DFMI and CIDA
into the interstellar dust stream.   At the present time the anomalous
behavior of the DFMI performance has not been tied to this large
temperature change, but this is under study.

Near-term activities for the next few months include setting CIDA back
to its operational state, turning the DFMI and Navigation Camera back on, 
and going to all stellar attitude.

For more information on the STARDUST mission - the first ever comet sample
return mission - please visit the STARDUST home page:

http://stardust.jpl.nasa.gov

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