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Because it was on a low-energy
trajectory for its flyby of comet Wild 2 and return
to Earth, and aided by a gravity-assisted boost
maneuver as it flew by the Earth for the first
time, the Stardust spacecraft needed only a relatively
modest propulsion system. This was provided by
ultra pure hydrazine (N2H4) monopropellant, a
system often used in spacecraft, including the
Space Shuttle. |
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The Stardust spacecraft is 3-axis
stabilized in all mission phases, after separation
from the launch vehicle. Stabilization is accomplished
using eight 0.45 kgf thrusters and eight 0.1 kgf
thrusters mounted in four clusters of 4 thrusters
each. The primary attitude determination is accomplished
using the star camera and the inertial measurement
unit (IMU), with backed up from analogue sun sensors.
The IMUs are only needed during trajectory correction
maneuvers, and during the fly-through of the cometary
coma when stars might be difficult to detect.
Otherwise, the vehicle can be operated in an all-stellar
mode. |
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The RAD6000 central processing
32-bit unit embedded in the spacecraft's Command
and Data Handling (C&DH) subsystem provides
computing capability for all spacecraft subsystems,
including the payload elements. Electronic cards
are provided to interface instruments and subsystems
to the C&DH subsystem. 128 Mbytes of data
storage are provided on the processor card, although
the spacecraft uses approximately 20% of this
for its own internal programs. The rest of the
space in the memory is used for science programs
and data storage for sending back to Earth 600
megabits (Mb) of images taken by the navigation
camera, 100 Mb by the Comet Interstellar Dust
Analyzer (CIDA) instrument and 16 Mb by the Dust
Flux Monitor (DFM). |
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Primary communication between
the Earth and the orbiter is through the Deep
Space Network (DSN) X-band (up/down) link and
the orbiter's deep space transponder developed
for the Cassini spacecraft, a 15 Watt RF solid
state amplifier, and a 0.6 meter (2 ft) diameter
fixed high gain parabolic antenna. |
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Two non-gimbaled solar arrays
were deployed immediately after launch. They provide
6.6 square meters of solar energy to power the
Stardust spacecraft. One nickel-hydrogen (NiH2)
16 amp-hour battery using common pressure vessel
(CPV) cell pairs provides power during eclipses
and for peak power operations. The electrical
power control electronics were derived primarily
from the Small Spacecraft Technology Initiative
(SSTI) spacecraft development. |
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The thermal control subsystem
uses passive methods and louvers to control the
temperature of the batteries and the solid state
power amplifiers. Passive coatings as well as
multi-layer insulation blankets are used to control
other temperatures. Where needed, radiators are
used to draw excess heat out of the spacecraft
components to maintain a proper operating temperature. |
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The Stardust spacecraft structure
is the shape of a rectangular box, with approximate
dimensions of about 5 feet (1.7) meters long by
a square cross-section of about 1 1/2 feet (0.66)
meters on each side. Panels use graphite fibers
with polycyanate as face sheets and aluminum honeycomb
as the core. |
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Virtually all spacecraft subsystem
components are redundant with critical items cross-strapped.
The battery includes an extra pair of cells. A
software fault protection system is used to protect
the spacecraft from reasonable, credible faults.
It also has resiliency built into it so many unanticipated
faults could be accommodated for without disabling
the spacecraft. |
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Last updated November
26, 2003 |
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