Instruments

FAST's scientific instruments are designed to conduct detailed studies of the earth's aurora. They include the Electrostatic Analyzer (ESA), Electric Field Sensors, Time of Flight Energy Angle Mass Spectrometer (TEAMS), and AC/DC magnetometers. For information about how FAST collects data from its instruments, please see the data page.

The instruments are mounted on a single deck that coincides with the spin plane of the spacecraft. This design allows the electric field booms to be as long as possible. FAST is a hollow shell above and below the instrument deck; its sides are covered with solar panels. The idea was to maximize the solar array area within the constraints of the Pegasus rocket shroud.

The instruments have been a huge success; please see publications and nuggets that have come from the analysis of FAST data. One of the electric field booms did not deploy completely, but the other three are working properly and can determine the electric field vector in the spacecraft's spin plane. Despite FAST's trajectory through the Van Allen radiation belts, FAST's instruments have not shown degradation since launch. They continue to produce data that are helping scientists learn more and more about the nature of the aurora.

The general design philosophy, quoted from Pfaff et al. (An Overview of the Fast Auroral SnapshoT (FAST) Mission), is as follows:

1. The mass of the spacecraft, instruments, and all flight components would be made as light as possible in order to achieve the highest possible apogee within the capabilities of the designated launch vehicle.
2. The design and placement of all components would be such that the satellite moment of inertia would be optimized to maximize the length of the spin axis electric field booms.
3. A single flight computer would control all of the instruments and their data acquisition, provide one common memory for burst and data storage, provide all regulated power, and house all of the electronics boards not directly needed at the sensor locations.
4. A separate electronics system, the Mission Unique Electronics (MUE) would handle basic life-support functions for the spacecraft, such as attitude control, battery charge control, command ingest, and safing functions, leaving the instrument computer free to operate at its maximum capability.
5. In order to optimize shielding against radiation, the instruments and flight components would be situated within the spacecraft where they "make sense" (e.g., batteries on the outside, critical flight computer components on the inside).
6. No solar paddles or extended solar arrays would be used, as they disrupt the in situ measurements, block energetic particle orbits, cause unwanted shadows, and create deleterious wake effects.
7. Electrostatic and electromagnetic cleanliness would be a spacecraft priority. The solar array and all exposed surfaces must be conducting and kept at the same potential as the spacecraft internal ground.
8. A large solid state memory (1 Gbit) would be included instead of tape recorders.
9. The satellite would utilize a variety of downlink rates, for which the highest rate is 2.25 Mbps, and uplink commanding would be available at 2 kbps.
10. The spacecraft would be single string, with practically no redundancy.
11. A NASA "Class C" Quality Assurance Program would be utilized.
12. In order to detect flaws and verify system performance, the spacecraft would be vigorously tested with all components integrated.

The following is quoted from Carlson et al., The Fast Auroral Snapshot Mission.

"The analyzer heads are grouped in pairs on opposite sides of the spacecraft to obtain an unobstructed 360o field of view for each measurement. They are packaged into four ESA stacks located at 90 degree intervals around the spacecraft (see figure 1). Each ESA stack includes three Stepped ESA (SESA) analyzers that are operated as spectrographs to obtain the highest time resolution (1.7 ms) electron measurements in 16 pitch-angle bins. The remaining analyzer in each stack is configured as an ion or electron spectrometer (IESA or EESA), used to make high resolutions distribution measurements with 32 pitch-angle bins every 70ms. The spectrometer analyzers include deflection plates that automatically steer their field of view to track the measured magnetic field direction." For more information, please see The Electron and Ion Plasma Experiment for FAST, by Carlson et al.

"The electric field is derived from the voltage difference between two spheres. The spheres can also be operated in a Langmuir probe mode to measure plasma density. The fields signal processing spans a frequency band from DC to about 2 Mhz and has a dynamic range of 100 dB. Data products include continuous waveform capture at 2000 samples/s, burst waveforms as high as 2 x 10⁶ samples/s, and spectra between 16 Hz and 2 Mhz. Dedicated on-board processing functions include; a) a high frequency resolution, tracking, spectrum analyzer, b) a wave-particle correlator, and c) a digital signal processor for fast Fourier transforms and cross-spectral analysis." For more information, please see The FAST Satellite Electric Field and Magnetic Field Instrument, by Ergun et al. Also, please see Pankow et al., Deployment Mechanisms on the FAST Satellite: Radial Wires, Stiff Axials, and Magnetometer Booms.

"The search-coil magnetometer uses a three-axis sensor system that provides AC magnetic field data over the frequency range 10 Hz to 2.5 kHz on two axes while the third axis response extends to 500 kHz." For more information, please see The FAST Satellite Electric Field and Magnetic Field Instrument, by Ergun et al., and Magnetic Field Instruments for the Fast Auroral Snapshot Explorer, by Elphic et al.

"The TEAMS instrument is a high sensitivity, mass-resolving ion spectrometer with an instantaneous 360° x 8° field of view. It is designed to measure the full 3-dimensional distribution function of the major ion species (including H+, He+, He++, O+, O₂+ and NO+) during each half-spin period (2.5 s) of the spacecraft. Its energy range is between 1.2 and 12000 eV/charge and thus covers the core of all important plasma distributions in the auroral acceleration region. The detector consists of a "top hat" toroidal electrostatic analyzer followed by a time-of-flight analysis system and resolves 16 x 22.5o azimuthal angle bins." For more information, please see The Time-of-Flight Energy Angle Mass Spectrograph (TEAMS) Experiment, by Klumpar et al.

Webpage maintained by Webster.