STARDUST Flight System Description
STARDUST Flight System Description
Key Spacecraft Characteristics
SpaceProbe Deep Space Bus Advanced Lightweight Composites Silicon Solar Cell Arrays No RTGs. No RHUs Fixed High-gain Antenna, x-Band Telecommunication Body-mounted Science (no scan platforms) Simple Hydrazine Monopropellant Propulsion Streamlined, Low-cost Sample Return Capsule (SRC) The STARDUST mission spacecraft is derived from the SpaceProbe deep space bus developed by Lockheed Martin Astronautics. This new lightweight spacecraft Encounter with Wild 2 incorporates components, virtually all of which are either currently operating in space or are flight qualified and manifested to fly on upcoming missions.
The total weight of the spacecraft including the propellant needed for deep space maneuvers is 380 kilograms. The overall length of the main bus is 1.7 meters, about the size of an average office desk.
The STARDUST spacecraft is scheduled to encounter comet Wild 2 early in 2004 and will collect samples of cometary dust and volatiles while flying through the coma at a distance of approximately 100 km on the sunlit side of the nucleus. It will then return the samples to Earth for analysis in 2006.
The scientific payload that is onboard the STARDUST spacecraft consists of the Aerogel Sample Collectors, Comet and Interstellar Dust Analyzer, Navigation Camera and the Dust Flux Monitor.
Science Payload
Aerogel Sample Collectors Comet and Interstellar Dust Analyzer (CIDA) Navigation Camera (NavCam) Dust Flux Monitor (DFM) Comet and interstellar particles are collected in ultra low density silica aerogel. More than 1,000 square centimeters of collection area is provided for each type of particle (cometary and interstellar). The CIDA instrument is a time-of-flight mass spectrometer that determines the composition of individual dust grains which collide with a silver impact plate. The Navigation camera is used for targeting the flyby of the Wild 2 nucleus, but also provides high-resolution science images of the comet. The DFM instrument, mounted on the front of the Whipple shield, monitors the flux and size distribution of particles in the environment.
Sample Return Capsule
Blunt Body Entry Vehicle Clamshell Mechanism to Open the Capsule Parachute and Mortar Unit The Sample Return Capsule (SRC) is a 60-degree blunt body reentry capsule for landing the returned sample on Earth. The capsule is encased in PICA and SLA-561 ablator materials to protect the samples stowed in its interior from the heat of reentry. A parachute slows its descent to the Earth's surface to prevent damage to the precious scientific cargo of comet samples.
Propulsion
Monoprop Propulsion System Because it is on a low-energy trajectory for its flyby of comet Wild 2 and return to Earth, aided by a gravity-assisted boost maneuver as it flies by the Earth for the first time, the Stardust spacecraft needs only a relatively modest propulsion system. This is provided by ultra pure hydrazine (N2H4) monopropellant.
Attitude Control
3-Axis Stabilized Eight 1-lb Thrusters, Plus Eight 0.2-lb Thrusters Thrusters are mounted in four clusters of 4 thrusters each. Star Camera + IMU, Analog Sun Sensors Backup The Stardust spacecraft is 3-axis stabilized in all mission phases, following separation from the launch vehicle. The primary attitude determination is via the star camera and the inertial measurement unit (IMU), and is backed up by analog sun sensors. The IMUs are needed only during trajectory correction maneuvers, and during the flythrough of the cometary coma when stars may be difficult to detect. Otherwise, the vehicle can be operated in an all-stellar mode.
Command & Data Handling
RAD6000 Processor 128 MBytes Data Storage The RAD6000 is a central processing 32-bit unit embedded in the spacecraft's Command and Data Handling (C&DH) subsystem and 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 is 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).
Telecommunications
Cassini Deep Space Transponders 15 Watt Radio Frequency Solid State Amplifiers One 0.8 meter High Gain Antenna (Transmit/Receive)
One Medium Gain Antenna (Transmit Only)
Three Low Gain Antennas (Receive Only) Primary communication between the Earth and the orbiter is by use of 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.
Power
2 Solar Array Panels of Special Silicon Solar Cells Nickel-Hydrogen CPV Batteries Two non-gimbaled solar arrays are deployed immediately after launch. They provide 6.6 square meters (71 sq. ft.) of solar energy to power the Stardust spacecraft, even when it is nearly three times farther from the sun than is the Earth. 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 are derived primarily from the Small Spacecraft Technology Initiative (SSTI) spacecraft development.
Thermal Control
Passive: Louvers, MLI, Paints, Dedicated Radiators Thermostatically and Computer Controlled Heaters 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 take the excess heat out of the spacecraft components to keep them at their proper operating temperature.
Structure
Composite structure, using Facesheets over Honeycomb The Stardust spacecraft structure is in the form of a rectangular box, with approximate dimensions of 1.6 meters long by a square cross-section of 0.66 meters on each side. Panels use graphite fibers with polycyanate as facesheets and aluminum honeycomb as the core.
Redundancy
Software Fault Protection Critical Items Cross-Strapped 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 but also has resiliency built into it so many faults not anticipated can be accommodated without taking the spacecraft down.
Whipple Shield
Multiple Separated Layers Bumper and Catcher Shields Nextel Blankets The Whipple shield shadows the spacecraft to protect it during the high speed encounter with particles in the cometary coma. Bumper shields are composite panels which disrupt particles as they impact. Nextel blankets of ceramic cloth further dissipate and spread the particle debris. Three blankets are used in the main body shield, and two are used in the solar array shields. The composite Catcher absorbs all of the debris for primary particles up to 1 cm in diameter for the shield protecting the spacecraft main body.