Astro-2 Public Affairs Status Report #4
6:00 p.m. CST (1/17:22 MET), March 3, 1995
Spacelab Mission Operations Control
Marshall Space Flight Center
Huntsville, Ala.

	The three Astro-2 telescopes have begun their methodical
exploration of the ultraviolet universe, as scientists aboard the
Shuttle Endeavour and at Spacelab Mission Operations Control fine-tune
the Astro-2 equipment and procedures to optimize pointing stability.

	This afternoon, payload controllers eliminated a drift in that
had been detected in the Instrument Pointing System by adjusting the
target acquisition procedure.

	The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE)
got its first turn as the primary instrument this morning.  Its
observations of a calibration star, Beta Cassiopeiae, showed that the
instrument optics, spectrometer and motion compensation system are
working well.  The team also will use the star as an unpolarized
standard against which other observations can be measured.

	The WUPPE team also made the first of several planned
observations of the supergiant star P Cygni.  These observations will
help scientists determine how this type of star ejects material into
interstellar space, whether uniformly in the shape of a shell, or in
the form of plumes or blobs of material.  Team members say this is an
interesting time to observe P Cygni, because recent ground-and
space-based observations indicate the star, which has been relatively
inactive for the past 100 years, has entered a more active phase of
its life.  Because the star can vary on a day-to-day basis,
observations made later in the mission will give astronomers an
important set of measurements over a relatively short time.

	During its time block, the Hopkins Ultraviolet Telescope (HUT)
observed a celestial "odd couple," two stars with radically different
temperatures in orbit around one another, called a symbiotic star
system.  The system HUT observed today, EG Andromedae, is made up of
an orange-colored giant star co-orbiting with a tiny, exceptionally
hot blue star.  Astronomers had not realized how hot the smaller star
is until an instrument aboard one of the Voyager planetary probes
picked up its strong ultraviolet emissions.

	The HUT team also checked out the sensitivity of their
spectrometer by viewing a white dwarf star, known as HZ 43, which they
had observed during Astro-1.  At a very late stage of its evolution,
the star has burned up nearly all of its fuel.  Astronomers understand
physical conditions in the atmospheres of HZ 43 and similar white
dwarfs well enough that they can calculate very precisely how much
ultraviolet light they emit.  This makes such stars useful for
confirming the HUT instrument's calibrations.

	The Ultraviolet Imaging Telescope (UIT) observations included
images of globular clusters, massive spherical concentrations of stars
that are the oldest class of objects in our Milky Way Galaxy.  "These
clusters appear to be 16 to 19 billion years old, despite recent
Hubble indications that the universe is only about 10 billion years
old," said UIT astronomer Dr. Steve Maran.  "UIT images of globular
clusters from Astro-1 revealed a previously unknown class of stars,
visible only in the ultraviolet, which may have skipped a stage in
stellar evolution as we had understood it.  We're hoping follow-up
observations of globular clusters during Astro-2 will give us a better
understanding of stellar physics."

	Science teams here in Huntsville are planning their
observational sequences on a day-to-day basis, much as astronomers
would in a ground- based observatory.  Each instrument team is
assigned two-orbit, or three-hour, blocks of time to take the lead in
selecting the celestial objects they wish to view from Astro's menu of
potential targets.

	Observations planned for overnight include more calibration
targets for HUT and WUPPE, a spiral galaxy, and an observation of the
planet Jupiter.