NASA Small Explorer Program - FAST Mission

FAST ON ORBIT

FAST was successfully launched on August 21, 1996. See the launch site updates for more information on launch activities.

FAST is in orbit and doing well. For the latest information, see the Berkeley FAST page or the latest Goddard status reports.

The aurora with North American lights below and the illuminated earth and stars at the top.

This server system is being developed to provide information about the NASA Fast Auroral Snapshot Explorer (FAST) Satellite. It is maintained by the NASA Goddard Space Flight Center Small Explorer Program in Greenbelt Maryland.

The information will include project overview, user documents, general FAST spacecraft pictures in GIF format, illustrations, experiment summaries, etc.

FAST Mission Overview

FAST is the second of the Small-Class Explorer (SMEX) missions. It will investigate the plasma physics of the auroral phenomena which occur around both poles of the earth. This will be accomplished by taking high data rate snapshots with electric and magnetic fields sensors, and plasma particle instruments, while traversing through the auroral regions.

FAST will orbit in a near-polar, highly elliptical orbit. Apsoidal rotation caused by this orbit configuration will position apogee over the northern pole approximately four months after launch thus providing optimal science conditions. FAST's one year mission duration will be highlighted by this period of intense spacecraft and scientific activity. The measurements made by FAST will address a a broad range of scientific objectives in such areas as:

The NASA/Goddard supplied FAST spacecraft is a 12 rpm classical spinner that will keep its spin axis continually aligned with the orbit-normal vector. Orbit altitude will be approximately 350 km x 4200 km at an inclination of 83 degrees. FAST was originally scheduled to be launched in August, 1994; unfortunately this launch was delayed due to problems with the Pegasus XL launch vehicle.

The FAST payload consists of four experiment packages:

  1. Electric Field Experiment: The electric field experiments 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.
  2. Magnetic Field Experiment: The magnetic field experiment (pictured here) consists of two magnetometers mounted 180 degrees 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.
  3. Time-of-Flight Energy Angle Mass Spectrograph (TEAMS): The TEAMS instrument is a high sensitivity, mass-resolving spectrometer that will measure full three-dimension distribution functions of the major ion species with one spin of the spacecraft. The TEAMS experiment cover the core of all plasma distributions of importance in the auroral region.
  4. 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 degree 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.

FAST Spacecraft Description

The FAST Mission requires a spacecraft which is compact, lightweight, and extremely power efficient. The design which has been developed is a classical, roughly cylindrical shaped spinner with a large body mounted solar array. The solar array utilizes Gallium Arsenide (GaAs) solar cells with a heavy 60 mil coverglass to protect the cells from the harsh radiation environment. An axial boom extends out both the positive and negative spin axis. Four wire booms extend out radially around the belly band of the spacecraft. Two diametrically opposed magnetometer booms also extend radially from the spacecraft. All of the booms support science instrument sensors. The ACS magnetometer is mounted near the elbow of the instrument fluxgate magnetometer boom.

Internally, the spacecraft configuration is very simple. All of the spacecraft electronics and instruments are mounted to a single deck. The deck is centrally located and distributes the boxes in such a manner so as to maximize the spin moment of inertia and minimize the transverse moments of inertia. The deck is a machined aluminum structure covered with a continuous skin so as to provide shielding from orbital radiation. This deck and its supporting thrust cone are the primary load carrying elements of the structural design. Mounted atop the boxes is a non-load carrying sheet of aluminum called the radiation disk. This disk, together with the belly band portion of the solar array, and the deck completely encapsulate the electronics to protect them from the orbital radiation environment. The boxes are heat-sunk to both the deck and the radiation disk.

The solar array is broken into two major elements, an upper cup and a lower cup. These array elements utilize an aluminum honeycomb substrate. They are self-supporting and attach to the edge of the deck.

The spacecraft electronics architecture is also very compact. All spacecraft functions are performed in one centralized box, the MUE. The MUE utilizes two Harris 80C85 rad hard microprocessors and some analog circuitry to control the spacecraft. It provides Attitude Control System (ACS), data encoding/decoding, spacecraft stored commands, spacecraft health and safety, spacecraft clocks, short term spacecraft data storage, spacecraft power distribution, pyro control, and battery charge control. The Instrument Data Processing Unit (IDPU) provides the long term bulk data storage.

The ACS is very simple. Spin rate control is done closed-loop onboard. Spin axis precession is done open-loop by daily uplinked stored command. All attitude determination is done by the ground. The ACS utilizes its own magnetometer, a digital sun sensor, and a horizon crossing indicator to sense vehicle attitude. Two air coil torquers and a nutation damper are used to control spacecraft attitude.

The Radio Frequency (RF) system uses a conformal, cylindrical microstrip patch antenna array that is mounted atop the vertical boom housing. An S-band transponder is used for command reception and telemetry broadcast.

The thermal design is passive in order to conserve power. It is anticipated that all internal spacecraft surfaces will have a black finish. Since the sun vector will move throughout the body axis during the mission, maintenance of a tight range of box temperatures is quite difficult. Because of this effect, the spacecraft attitude will be constrained such that the sun vector never gets closer than 30 degrees to the spin axis. The spacecraft sun vector constraint is also necessary in order to keep a sufficient area of the solar array illuminated for proper power generation.

FAST Spacecraft Development

Click here for an illustrated record of the FAST spacecraft fabrication and integration.

Fast Auroral Snapshot Explorer Images

The image files in this area are of Fast Auroral Snapshot Explorer spacecraft and associated ground equipment.

  1. FAST Logo
  2. Spacecraft suspended prior to Thermal Vacuum
  3. Spacecraft outfitted with solar panels
  4. Closeup of spacecraft solar panels
  5. Spacecraft electronics on deck
  6. FAST Faces

1996 I&T Trending Data and plots are available and on-line!

Other FAST pages

More Information

What good is this science?

In addition to the value of expanding human knowledge (and the unanticipated spin-offs), better understanding of the aurora will lead to reduced costs and improved reliability for the power industry.

Contact Information

The FAST Auroral Snapshot Explorer (FAST) Project is located at NASA Goddard Space Flight Center (GSFC) in Greenbelt, Maryland (near Washington, D.C.). The mission manager for FAST is Jim Watzin. The principal investigator is Dr. Charles Carlson of the University of California, Berkeley.

To contact the FAST Project:

To send E-mail comments to the Project, click here.

Acknowledgments

Unless otherwise stated, photographic images are courtesy of Anne Koslosky.

Back to the SMEX project home page or the GSFC home page.
Author: Charles Melhorn/HSTX (melhorn@sunland.gsfc.nasa.gov)
Curator: Tim Singletary (tsingle@sunland.gsfc.nasa.gov)
Revision: October 29, 1996