🚀 go-pugleaf

In article <1993Jan20.175137.15052@aio.jsc.nasa.gov> kjenks@gothamcity.jsc.nasa.gov writes:
>In article <00966AA0.C6BD3A40@SAMSON.PHYS.VIRGINIA.EDU> cole@SAMSON.phys.virginia.edu writes:
>>There seems to be a lack of the usual earth views
>>from the payload bay during the crew sleep period
>>on this mission.  Anybody at JSC care to comment?
>
>Good eyes!
>
>The Orbiter was in an unusual attitude for much of the mission.  We
>usually position the PLB toward the Earth for Earth Obs and for some
>thermal effects.  But this mission, the PLB was facing away from Earth
>(in an orientation called "+ZLV") for extended periods in support of
>the DXS experiment, which was apparently a "Deep Space X-ray"
>experiment.  So the PLB was pointing at deep space.  I don't know any
>details about the experiment.  I can dig more if anybody's really
>interested.
>
>I noticed especially that we lost sight of a really nifty thunderstorm
>when the PLBD obscured the view.
>
>References: 
>
>  NSTS-07700, Volume III, FLIGHT DEFINITION AND REQUIREMENTS DIRECTIVE
>    Rev L, Change 291, Table C-1, "Flight History"
>
>  JSC-10511, Attitude and Pointing Flight Procedures Handbook,
>    Rev A, 1985, Figure 5-4, page 5-5.
>
>-- Ken Jenks, NASA/JSC/GM2, Space Shuttle Program Office
>      kjenks@gothamcity.jsc.nasa.gov  (713) 483-4368
>
>     "NASA turns dreams into realities and makes science fiction
>      into fact" -- Daniel S. Goldin, NASA Administrator

The shuttle attitude for STS-54 was driven much of the time by the
DXS experiment.  This instrument, the Diffuse X-ray Spectrometer
(I'm the project scientist) is designed to look at the sky in x-rays
and measure the spectrum of the glow that comes from interstellar
space.  We have a large and unique data set to analyze; the quick look
shows that the solar system is embedded in a region of hot gas about
300 light-years in radius.

Since we wanted to look at deep space, the shuttle was put into an
inertial attitude (fixed relative to the stars), with the payload
bay facing deep space during orbit night, and facing earth during orbit
day.  This causes some of the equipment in the payload bay to get too
cold, so when the astronauts were awake, they maneuvered the shuttle
into a -ZSI attitude (bay to sun) during orbit day, and then back to
the DXS attitude during orbit night (2 maneuvers each 90-minute orbit!
Thanks, guys!)  So there was not much time when the crew could observe
the earth.