FAST SPACECRAFT TO PROBE MYSTERIES OF THE AURORA
Don Savage, Jim Sahli
Data collected by “state-of-the-art” instruments on
NASA’s Fast Auroral Snapshot (FAST) Explorer satellite,
scheduled for launch on August 16, will probe the physical
processes that produce auroras, while adding significantly to
our understanding of the Earth’s environment in space.
Auroras have been a source of fascination and
superstition for centuries. In recent decades, however, the
phenomenon has become better understood through scientific
research, particularly with the aid of spaceflight
instrumentation.
“The purpose of the FAST spacecraft is to investigate the
physics of acceleration processes in nature. Specifically,
FAST will investigate how particles are accelerated in space
to create the aurora (or “northern and southern lights”),”
said Dr. Robert Pfaff, the FAST project scientist at NASA’s
Goddard Space Flight Center, Greenbelt, MD.
FAST will be launched from the Western Test Range, at
Vandenberg Air Force Base, CA, using a winged Pegasus-XL
launch vehicle. The development of the satellite cost a
total of approximately $45 million — $27 million for the
spacecraft and $18 million for the instruments. Launch
services will add approximately another $15 million to the
mission cost.
The five scientific instruments aboard FAST will
gather high time resolution “snapshots” of the electric
fields, magnetic fields, and energetic electron and ion
distributions at high altitudes of 1,200 – 2,600 miles and at
high latitudes (greater than 60 degrees) near the Earth’s
magnetic poles.
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The science to be conducted on FAST complements
many of the science objectives of other NASA satellites. The
recently launched NASA Polar spacecraft takes images of the
aurora from altitudes of eight Earth radii above the Earth’s
poles and shows how the auroral light is distributed within
the Earth’s high latitude regions. The FAST satellite, on
the other hand, will journey to the “heart” of the aurora,
the region about 1,250 – 6,250 miles above the Earth at high
latitudes, where charged particles are energized and where
they are subsequently accelerated down towards the upper
atmosphere where the auroral light is emitted.
The FAST satellite includes an onboard flight
computer which enables it to take high resolution “snapshots”
when it encounters interesting science events. In addition,
FAST will receive real time commands from scientists on the
ground to operate in certain modes and to revise the
selection criteria used to identify various unique features
of the aurora.
The science data from FAST will be directly down-
linked to several ground stations operated by NASA. These
include the transportable ground station in Poker Flat, AK,
and a ground station at NASA’s Wallops Flight Facility,
Wallops Island, VA. In addition, FAST data will be
downlinked to another NASA transportable ground station at
McMurdo Station, Antarctica and a European ground station in
Kiruna, Sweden.
The science analysis of the FAST data will be
carried out under the leadership of principal investigator
Dr. Charles Carlson at the University of California at
Berkeley.
FAST will carry the following instruments designed
to collect the necessary data to carry out the aurora
investigations: The Electrostatic Analyzers to measure
energetic electrons and ions, the Electric Field Experiment,
and the Instrument Data Processor Unit, provided by the
University of California at Berkeley; the Time-of-Flight
Energy Angle Mass Spectrograph, from the Lockheed Martin
Advanced Technology Center in Palo Alto, CA, the University
of New Hampshire in Durham, the University of California at
Berkeley and the Max-Planck Institute in Germany; and the
Magnetic Field Instrument, from the University of California
at Los Angeles.
The Pegasus-XL launch vehicle, built by Orbital
Science Corp., Dulles, VA, is a three-stage, solid-propellant
booster system carried aloft by an L-1011 jet aircraft and
released from the aircraft at an altitude of about 40,000
feet and an airspeed of Mach 0.8. The FAST launch window is
from July 15 to Sept. 10, 1996. The daily window is
approximately eight minutes in duration and opens at about
5:42 a.m. EST each morning.
FAST is the second of five missions in NASA’s Small
Explorer (SMEX) Project developed by Goddard. The SMEX
satellites are highly capable small observatories that are
being used to support quick response astrophysics and space
physics investigations.
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“Innovative engineering and new technology advances
have increased the potential scientific return of the SMEX
spacecraft to a level comparable to larger carriers. The
design has struck a balance between mission risk and cost
that has allowed for the development of an extremely capable
spacecraft within just three years time. The SMEX program
well embodies the faster, better, cheaper concept,” said
James Watzin, SMEX project manager at Goddard.
The spacecraft is a single string design and is
intended to operate at least for one year. The expected
satellite lifetime is limited due to the anticipated high
radiation environment and orbit decay.
Information on the Fast mission can be obtained
via the Internet World Wide Web at URL:
http://sunland.gsfc.nasa.gov/smex/fast/fast_top.html
