Solar/Space Observation Satellites
FAST
The Fast Auroral SnapshoT Explorer (FAST), the second mission in NASA's Small Explorer Satellite Program (SMEX), is a satellite designed to study Earth's aurora. This highly successful spacecraft has helped scientists answer fundamental questions about the causes and makeup of the aurora. FAST was launched on August 21, 1996 from a Pegasus rocket into a highly elliptical orbit. It crosses Earth's auroral zones (donut shaped regions centered on the poles) four times each orbit, and only collects high-resolution data ("snapshots") while in those zones. It ventures high into the charged particle environment of the aurora to measure the electric and magnetic fields, plasma waves, energetic electrons and ions, ion mass composition, and thermal plasma density and temperature. The FAST instrument set consists of sixteen electrostatic analyzers, four electric field langmuir probes suspended on 30 m wire booms, two electric field langmuir probes on 3 m extendible booms, searchcoil and fluxgate magnetometers and a time-of-flight mass spectrometer. The science investigation makes extremely temporal and spatial resolution measurements of the auroral plasma at apogee altitude. The instrument hardware consists of the sensor assemblies and an instrument data processor. The instrument electronics include a 32-bit data processing unit that performs the science data processing and recording in a one gigabit, solid-state memory. The stored data are transferred to the ground at one of three selectable high data rates of 900 Kbps, 1.5 Mbps or 2.25 Mbps. The instruments weigh 51 kg; the total observatory mass is 191 kg. The FAST mission is in a 351 x 4175 km orbit with an 83? inclination. The FAST observatory is a 12 rpm, spin-stabilized spacecraft with its spin axis oriented parallel to the orbit axis. Spin rate and spin-axis orientation are maintained by two magnetic torquer coils, one spinning Sun sensor, one horizon crossing indicator and a spacecraft magnetometer. The Attitude Control System (ACS) provides closed-loop spin-rate control. Spin-axis precession is performed open loop and is closed via ground commands. After computation on the ground, attitude knowledge is accurate to within one degree. The body-mounted solar array contains 5.6 m2 of solar cells that can distribute 52 W of orbit average power to the spacecraft and instruments. The orbit average power consumption of the spacecraft hardware is 33 W. The instruments consume 19 W orbit average power, 39 W when operating. Instruments are frequently powered off in order to maintain a positive energy balance. The data system for the FAST mission consists of dual 8085, 8-bit spacecraft computers. The spacecraft computers perform health and safety functions, power distribution, data encoding/decoding and launch vehicle interface. A multi-element micropatch antenna mounted on a boom above the spacecraft supports ground communications. Commands are uplinked at 2 Kbps. Health and safety data is telemetered to the ground at 4 Kbps. A Transportable Orbital Tracking Station (TOTS) was placed in Alaska to collect real-time science telemetry while the spacecraft is passing through the northern aurora. TOTS is highly automated and portable; it has an 8 m antenna with 200 W of uplink power and can be packed for shipment in three ISO containers. The FAST instruments consist of: Electric Field Experiment: The electric field experiment is composed of three orthogonal boom pairs. Spherical sensors deployed on radial wire and axial stacer booms will provide information on the plasma density and electron temperature. Magnetic Field Experiment: The magnetic field experiment consists of two magnetometers mounted 180? apart on deployable graphite epoxy booms. The search coil magnetometer uses a three-axis sensor system to provide magnetic field data over the frequency range of 10 Hz to 2.5 kHz. The flux gate magnetometer is a three-axis system using high, stable, low noise, ring core sensors to provide magnetic field information for DC to 100 Hz. Time-of-Flight Energy Angle Mass Spectrograph (TEAMS): The TEAMS instrument is a high sensitivity, mass-resolving spectrometer that measures full three-dimension distribution functions of the major ion species with one spin of the spacecraft. The TEAMS experiment covers the core of all plasma distributions of importance in the auroral region. Electrostatic Analyzers (ESA): Sixteen ESAs configured in four stacks will be used for both electron and ion measurements. The four stacks are placed around the spacecraft such that the entire package is provided a full 360? field of view. The ESAs can provide a 64-step energy sweep, covering approximately 3 eV to 30 KeV up to 16 times per second. For more information, see: http://sprg.ssl.berkeley.edu/fast/ Group: Platform_Details Entry_ID: FAST Group: Platform_Identification Platform_Category: Solar/Space Observation Satellites Short_Name: FAST Long_Name: Fast Auroral Snapshot Explorer End_Group Group: Synonymous_Platform_Names Short_Name: Explorer 70 Short_Name: SMEX/FAST Short_Name: Small Explorer/FAST Short_Name: 24285 Short_Name: 1996-049A End_Group Group: Platform_Associated_Instruments Short_Name: MFS/FAST Short_Name: EFS/FAST Short_Name: ESA/FAST Short_Name: TEAMS End_Group Group: Orbit Orbit_Inclination: 83 degrees Period: 133 m Perigee: 350 km Apogee: 4175 km Orbit_Type: HEO > Highly Elliptical Orbit End_Group Online_Resource: http://sprg.ssl.berkeley.edu/fast/intro.html Sample_Image: http://sprg.ssl.berkeley.edu/fast/graphics/fast.gif Group: Platform_Logistics Launch_Date: 1996-08-21 Launch_Site: Vandenberg Air Force Base, USA Primary_Sponsor: NASA End_Group End_Group