Fast Auroral Snapshot Explorer

• 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.

Latest Mission Information
Space Science Laboratory University of California at Berkeley.
Mission Operations

The Science

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.

Author: Jim Watzin (jim.watzin@gsfc.nasa.gov)
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The last time this page was updated was 11/21/97.