ATLAS 3 Public Affairs Status Report #14
6:00 a.m. CST, Nov. 10, 1994
MET 6/19:00
Spacelab Mission Operations Control
Marshall Space Flight Center
Huntsville, Ala.

The ATLAS 3 solar instruments completed the sixth and final orbit of their
solar observation period at around 9:25 p.m. CST, and then last night's
scheduled communications with the CRISTA-SPAS satellite started.  This was
the third of four periods planned during ATLAS 3 for the Shuttle's cargo
bay to point at the sun.  By accumulating data during multiple observation
periods, scientists can make extremely precise measurements of the sun's
total energy output and its dispersion.  Multiple solar periods also allow
them to study short-term solar variations.  All the solar instruments
collected very high quality data. 

Two University of Colorado students participated in science planning
meetings in Huntsville during the last three solar observation periods. 
The students represented a Colorado Space Grant Consortium project, the
second Experiment of the Sun for Complementing the ATLAS Payload and for
Education (ESCAPE-II), housed in a Get-Away-Special canister in the
Shuttle cargo bay. 

A secondary payload co-manifested for the ATLAS 3 mission, ESCAPE-II is
making observations concurrently with the ATLAS solar instruments, in
particular with the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM),
which also measures solar ultraviolet radiation in the same wavelength
ranges.  The experiment was designed, managed and built entirely by 60
undergraduate and graduate students at the University of Colorado in
Boulder.  ESCAPE II is a follow-on payload to the Extreme Ultraviolet
Solar Complex Autonomous Payload Experiment (ESCAPE I), also known as the
Solar Ultraviolet Experiment (SUVE), which flew in April 1993 onboard the
Space Shuttle Discovery as part of the STS-56/ATLAS 2 mission. 

Instruments on ESCAPE II include a Far Ultraviolet Spectrometer (FARUS)
and a digital Lyman Alpha Spectrum Imaging Telescope (LASIT), which obtain
digital images of the solar disk in extreme ultraviolet, 121.6 nanometer,
wavelengths in which little research has been done over the last 20 years. 
The experiment is expected to shed new light on how the sun's extreme
ultraviolet wavelengths affect the upper atmosphere, as well as providing
for the ESCAPE II students what instrument Team Leader Kathy Wahl called
"a hands-on education that you do not get in any classroom experience." 

The Active Cavity Radiometer Irradiance Monitor (ACRIM) monitored solar
irradiance in its ongoing effort to determine possible fluctuations in the
sun's total output of optical energy.  The Upper Atmosphere Research
Satellite (UARS) also carries a similar ACRIM instrument, and the two
ACRIM's have been making cooperative observations throughout the mission. 
At the close of the last solar observation period, ACRIM team member Roger
Helizon observed, "the sun is very stable this year.  This gives us flat
data plots, allowing us to do very tight collaborative measurements with
UARS." 

After the end of the solar period and during the communications between
the orbiter and the CRISTA-SPAS instruments, atmospheric observations
resumed as the Middle Atmosphere High Resolution Spectrograph
Investigation (MAHRSI) switched from measuring hydroxyl to measuring
nitric oxide at heights of 60 to 84 miles (100-140 km). 

At around 3:30 a.m. CST, the MAHRSI science team at the Marshall Space
Flight Center in Huntsville used an Internet connection to research data
records of the International Ultraviolet Explorer (IUE), a satellite
launched in 1978, to obtain an old ultraviolet spectrum observation of the
Moon.  In order to compare and validate their spectral measurements of
hydroxyl, the MAHRSI team looks for an ultraviolet spectrum, that is free
from atmospheric interference, to use as a reference.  Ultraviolet spectra
of the Moon are ideal for such purposes, and the data records of IUE
furnished this reference.  "For us, it's a real breakthrough in the
analysis of our data," commented MAHRSI Principal Investigator Robert
Conway .

Meanwhile, the Cryogenic Infrared Spectrometers and Telescopes for the
Atmosphere (CRISTA) instrument continued collecting infrared spectra of
trace gases.  CRISTA has taken a total of over ten million spectra so far,
an amount that would fill more than six thousand computer discs with raw
data.  Both the CRISTA and MAHRSI instruments continue to perform well,
amassing valuable atmospheric data. 

The Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument continued
observing orbital sunrises and sunsets to identify and measure molecules
and their vertical distribution in the atmosphere.  ATMOS acquired good
spectral data on key atmospheric molecules, especially chlorine-containing
gases, that it is intended to measure as part of its science objectives. 
The ATMOS science team reports that the experiment's onboard data recorder
is over eighty-five percent full and that they are trying to take as many
of their measurements via live down link in order to conserve the
remaining recorder space for the rest of the mission.  The Shuttle crew
made occasional maneuvers of Atlantis during the night to help facilitate
this live down link. 

Atmospheric observations will continue throughout the next twelve hours as
ATLAS 3 approaches its eighth day of flight.