| INSTRUMENT_HOST_DESC |
This description was copied from the 'Stardust Mission Plan'
document with permission from the Stardust project. It has been
updated to reflect the completion of the primary mission.
SDN: This description has been updated for the Stardust-NExT
extended mission. The original description was left largely
intact and a short section added at the end for SDN. The prefix
'SDN' occurs before that section.
STARDUST was a 3-axis stabilized spacecraft designed to perform
its prime mission (Wild 2 encounter) at 1.9 AU from the sun and
2.6 AU from the earth. During the cruise periods to and from
this encounter, it was able to function adequately at a
maximum distance of 2.7 AU from the sun and 3.6 AU from the
earth.
The spacecraft was equipped with a power subsystem, fixed solar
panels and one rechargeable battery, capable of delivering a
minimum of 170 watts (W) during standard cruise operations at
aphelion and a minimum of 300 W at comet encounter. The solar
panels had a maximum off-sun pointing constraint of 60 degrees
to avoid problems caused by refraction of light.
Communications were achieved via either a high-gain, medium-gain
or one of three low gain antennas. During the mission, Deep Space
Network (DSN) support was provided with primarily 34-m
antennas with 70-m support being used during the close comet
encounter, trajectory correction maneuvers, and other special
activities. These antennas provided the capability for a minimum
of 4000 bits per second (bps), 7900 bps expected, at encounter
via the high-gain antenna and a 70-m DSN station. This data rate
could be increased to 22120 bps with additional tight attitude
control. At maximum Earth range, 40 bps could be achieved via the
medium gain antenna and a 34-m DSN station. The low-gain
antennae, in conjunction with a 34-m DSN antenna, were ideal for
near-Earth phases (Launch, Earth flyby and Earth return) when
Sun-Earth-spacecraft angles were near 90 degrees, especially since
they could support communications within 0.05 AU (+3 dB margin) of
the earth at a minimum data rate of 40 bps.
Attitude control and propulsive maneuvers were performed using a
redundant helium-fed mono-propellant (hydrazine) propulsion
subsystem. The subsystem was comprised of one titanium propellant
tank and a total of 16 thrusters (two strings of 8), all mounted
on the lower deck of the spacecraft (opposite the high-gain
antenna and solar panels - pointing toward the -z-axis of the
spacecraft). Eight of these were 0.2 lb-f (0.89 N) thrusters and
were used primarily for attitude control. The other eight are 1.0
lb-f (4.45 N) thrusters and were used for propulsive maneuvers. To
avoid potential contamination of the aerogel collector, placement
of thrusters on the upper deck (+z) was avoided. This
configuration, however, generated uncoupled thrusts during
attitude control burns and added complexity to trajectory
simulations.
The normal spacecraft attitude during the mission pointed the
+z-axis of the spacecraft to the sun. Deviations from the normal
attitude were performed during communication periods and
delta-velocity burns. Off-sun pointing was also permitted
during non-primary science experiments, comet and interstellar
dust particle collection, as long as the power generated by
the solar arrays was adequate at the desired off-sun angle. During
the comet encounter period, the +x-axis was pointed to the dust
stream.
Whipple shields were placed on the spacecraft to protect it from
high velocity dust impacts during the comet encounter. The barriers
were designed to stop a 1 cm size particle traveling at 6 km/s
(which was essentially equal to the comet encounter relative
velocity).
Science objectives were met using three science subsystems:
Aerogel Dust Collector and Sample Return Capsule (SRC), Cometary
and Interstellar Dust Analyzer (CIDA) and the Dust Flux Monitor
Instrument (DFMI). The imaging camera was also used for science
purposes but its main function was to perform optical navigation
prior to encounter with comet Wild 2.
The current best estimate of the mass breakdown of the flight
system is summarized in this table:
STARDUST Mass Element List (Rev. Z)
Component Mass (kg) Component Mass (kg)
S/C Power 33.378 Navigation Camera 12.686
S/C Harness 20.971 DFMI 1.530
S/C Telecom 19.222 CIDA 10.966
S/C ACS 9.951 SRC Avionics 1.992
S/C C&DH 10.394 SRC Harness 0.869
S/C Thermal 10.060 SRC Thermal 13.683
S/C Structures 104.412 SRC Structures 9.271
S/C Mechanisms 6.131 SRC Mechanisms 17.184
S/C Propulsion 19.538 SRC Parachute 4.194
Pressurant (He) 0.202 Total Dry 305.397
Propellant 85.000 Total Wet 390.599
SDN: Stardust-NExT update
==========================
Extended mission
----------------
The Stardust spacecraft flew by Earth in January, 2006 to
successfully return the SRC. The Stardust-NExT extended
mission was developed soon after and used SDU, without the SRC
and with an estimated 14kg+ of fuel, to fly the remaining
instruments (CIDA, DFMI, and NAVCAM) as a scientific
investigation past the comet 9P/Tempel 1 in February, 2011.
The limited fuel made flying the extended mission quite
challenging, but maneuvers and operations were optimized to
minimize fuel usage, and the spacecraft successfully encountered
Tempel 1 on 15 February, 2011 with all instruments in working
order.
Postscript
----------
In March, 2011 the project commanded SDU to perform a final
propulsive maneuver designed to burn the remaining fuel to
exhaustion to calibrate and/or validate the fuel estimation
techniques which had been used.
The final telemetry from the Stardust spacecraft activity
indicated that the fuel consumed during this activity was no more
than could be accounted for by the volume of the fuel system
lines. So at the end of two scientific missions, the Stardust
fuel tank was literally empty.
|
.png)
.png)
