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astronautix.com Stardust


Class: Planetary. Type: Comet. Nation: USA. Agency: NASA. Manufacturer: Lockheed-Martin.

Stardust was scheduled to encounter comet Wild-2 early in 2004 and collect samples of cometary dust and volatiles while flying through the coma at a distance of 100 km on the sunlit side of the nucleus. It would then return the samples to Earth for analysis in 2006.

The Stardust spacecraft was derived from the SpaceProbe deep space bus developed by Lockheed Martin Astronautics. This new lightweight spacecraft incorporated components which were either operating in space or flight qualified and manifested to fly.

The total weight of the spacecraft including the propellant needed for deep space manoeuvres was 380 kilograms. The overall length of the main bus was 1.7 meters.

Science Payload

  • Aerogel Sample Collectors - Comet and interstellar particles were collected in ultra low density silica aerogel. More than 1,000 square centimetres of collection area was provided for each type of particle (cometary and interstellar).

  • Comet and Interstellar Dust Analyser (CIDA) - The CIDA instrument was a time-of-flight mass spectrometer that determined the composition of individual dust grains which collided with a silver impact plate.

  • Navigation Camera (NavCam) - The Navigation Camera was used for targeting the flyby of the Wild 2 nucleus, but also provided high-resolution science images of the comet.

  • Dust Flux Monitors (DFM) - The DFM instrument, mounted on the front of the Whipple shield, monitored the flux and size distribution of particles in the environment.

    Sample Return Capsule

    The Sample Return Capsule (SRC) was a 60-degree blunt body re-entry capsule for landing the returned sample on Earth. The capsule was encased in PICA and SLA-561 ablator materials to protect the samples stowed in its interior from the heat of re-entry. A parachute slowed its descent to the Earth's surface to prevent damage to the cargo of comet samples.

    Propulsion - Because it was on a low-energy trajectory for its flyby of comet Wild 2 and return to Earth, aided by a gravity-assisted boost manoeuvre 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.

    Attitude Control - The Stardust spacecraft was 3-axis stabilised in all mission phases, following separation from the launch vehicle. Stabilisation was 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 was via the star camera and the inertial measurement unit (IMU), and was backed up by analogue sun sensors. The IMUs were needed only during trajectory correction manoeuvres, and during the fly-through of the cometary coma when stars might be difficult to detect. Otherwise, the vehicle could be operated in an all-stellar mode.

    The Stardust spacecraft was 3-axis stabilised in all mission phases, following separation from the launch vehicle. The primary attitude determination was via the star camera and the inertial measurement unit (IMU), and was backed up by analogue sun sensors. The IMUs were needed only during trajectory correction manoeuvres, and during the fly-through 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 - The RAD6000 central processing 32-bit unit embedded in the spacecraft's Command and Data Handling (C&DH) subsystem provided computing capability for all spacecraft subsystems, including the payload elements. Electronic cards were provided to interface instruments and subsystems to the C&DH subsystem. 128 Mbytes of data storage was provided on the processor card, although the spacecraft used approximately 20% of this for its own internal programs. The rest of the space in the memory was 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 Analyser (CIDA) instrument, and 16 Mb by the Dust Flux Monitor (DFM).

    Telecommunications - Primary communication between the Earth and the orbiter was by use of the Deep Space Network (DSN) X-band (up/down) link and the orbiterís 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 - Two non-gimballed 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 provided 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.

    Thermal Control - The thermal control subsystem used 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 were used to control other temperatures. Where needed, radiators were used to take the excess heat out of the spacecraft components to keep them at their proper operating temperature.

    Structure - The Stardust spacecraft structure was 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 used graphite fibres with polycyanate as face sheets and aluminium honeycomb as the core.

    Redundancy - Virtually all spacecraft subsystem components were redundant with critical items cross-strapped. The battery included an extra pair of cells. A software fault protection system was used to protect the spacecraft from reasonable, credible faults but also had resiliency built into it so many faults not anticipated could be accommodated without taking the spacecraft down.

    Whipple Shield - The Whipple shield shadowed the spacecraft to protect it during the high speed encounter with particles in the cometary coma. Bumper shields were composite panels which disrupt particles as they impact. Nextel blankets of ceramic cloth further dissipated and spread the particle debris. Three blankets were used in the main body shield, and two were used in the solar array shields. The composite Catcher absorbed all of the debris for primary particles up to 1 cm in diameter for the shield protecting the spacecraft main body.


    Specification

    Total Mass: 370 kg.


    Stardust Chronology


    07 February 1999 Stardust Launch Site: Cape Canaveral . Launch Vehicle: Delta 7925. Mass: 370 kg.

    Stardust was to fly within 100 km of comet 81P/Wild-2 in January 2004 and recover cometary material using an aerogel substance. A return capsule would land on a lake bed in Utah in January 2006, returning the material to earth. The launch went as planned. The second stage ignited at 21:08 GMT and its first burn put the vehicle into a 185 km x 185 km x 28 degree parking orbit at 21:14 GMT. The second stage second burn at 21:25 changed the orbit to planned values of 178 km x 7184 km x 28.5 degrees. The Star 37FM solid third stage ignited at 21:29 GMT and placed the spacecraft into a 2 year period solar orbit. The spacecraft separated at 21:31 GMT. Meanwhile, the Delta 266 second stage burned a third time on its own, until its propellants were depleted, entering a final orbit of 294 km x 6818 km x 22.5 degrees.



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