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FAST SPACECRAFT TO PROBE MYSTERIES OF THE AURORA

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