ATLAS 3 Public Affairs Status Report #6
6:00 a.m. CST, Nov. 6, 1994
MET 2/19:00
Spacelab Mission Operations Control
Marshall Space Flight Center
Huntsville, Ala.

Atmospheric instruments of the ATLAS-3 Spacelab continue to 
use a variety of remote-sensing techniques to define the 
chemical composition of Earth's atmosphere.  The chemistry of 
the middle atmosphere is very complex, involving many gases.  
Accurate measurements of a large number of trace molecules 
are needed to verify computer models of how that chemistry 
works, so atmospheric changes which occur naturally can be 
distinguished from those that are induced by human activity.

The Atmospheric Trace Molecule Spectroscopy (ATMOS) 
instrument continued to view the sun's infrared radiation 
through the Earth's atmospheric limb during orbital sunrises 
and sunsets, making global measurements of the composition of 
the troposphere, stratosphere and mesosphere.  Already, the 
device has provided additional data on atmospheric trace 
gases in near real-time.

For the first time, scientists here at the Marshall Space 
Flight Center in Huntsville have been completing analysis of 
ATMOS' observations within 24 hours of acquisition and 
comparing their results with those obtained by the Total 
Ozone Mapping Spectrometer (TOMS) aboard the Russian Meteor 3 
satellite.  Such rapid data reduction represents a remarkable 
improvement over the previous flights of the ATMOS 
instrument.  According to ATMOS team member Mark Abrams, "by 
building automated data processing systems, we've been able 
to reduce the data processing time by more than a factor of a 
hundred....from months to hours."  ATLAS 3 marks the fourth 
flight of ATMOS aboard the Shuttle.

The Shuttle Solar Backscatter Ultraviolet Spectrometer 
(SSBUV) peered through the atmosphere to the Earth's surface 
to identify both the total amount of ozone present and its 
distribution by altitude.  The SSBUV team has already done 
preliminary processing of solar data taken by the instrument 
on Friday to determine how well it compares with data from 
previous missions.  So far, analysis has revealed that these 
measurements are of high quality and that they agree to 
within one or two percent with results from ATLAS 1 and 2.  
This information should help the scientists to distinguish 
those processes induced by solar activity from those caused 
by human activities.  During the current atmospheric 
observation period, SSBUV has completed 14 orbits of Earth 
views and 12 concurrent measurements with its sister 
instrument aboard the NOAA-9 spacecraft.  The primary purpose 
of SSBUV, now on its seventh flight , is to verify the 
accuracy of data being gathered by free-flying satellites.

After 30 hours of data collection, the CRISTA instrument had 
measured more than three million infrared spectra of trace 
gases in the Earth's atmosphere.  The device has completed 
over 6000 measurements of variations in the distribution of 
trace gases at heights between 30 and 150 km with a 
resolution of 1.5 km.  CRISTA continues to collect data at a 
rate of 26 spectra per second, and all parts of the system 
are working nominally.  The second instrument aboard CRISTA-
SPAS, the MAHRSI experiment, is measuring hydroxyl spectra in 
the middle atmosphere, and the observed spectral data shows a 
clear detection of hydroxyl.  Hydroxyl plays a key role in 
the natural destruction of ozone.  Both CRISTA and MAHRSI are 
very pleased with the quantity and quality of the data they 
have received.

Atmospheric observations will continue to be the primary 
focus of activity for the next shift, followed by another 
period of communication period with the CRISTA-SPAS 
spacecraft.  Then, the mission's second solar pointing period 
will begin.