Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/DAILY_1/921223.DFC

Text File | 1992-12-23 | 17KB | 367 lines

23-Dec-92 Daily File Collection
   These files were added or updated between 22-Dec-92 at 21:00:00 {Central}
                                         and 23-Dec-92 at 21:00:12.

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KSC SHUTTLE STATUS REPORT 12/23/92







                   SPACE SHUTTLE STATUS REPORT
                   Kennedy Space Center, Florida

                   Wednesday, December 23, 1992


George H. Diller


Vehicle: OV-105/Endeavour   Mission Number: STS-54
Location: Launch Pad 39-B
Primary Payload: TDRS-F/IUS-13 + Diffuse X-ray Spectrometer (DXS)
Launch Timeframe: January 13  8:52 a.m. EST
Mission Duration: 5 Days 23 Hours 33 Minutes
Inclination: 28.45 degrees   Crew Size: 5
Nominal Landing: KSC  Jan. 19  8:24 a.m. EST


IN WORK TODAY:

- aft main engine compartment closeouts

- preparations for holiday work suspension/holiday outages


WORK COMPLETED:

- Flight Readiness Review (FRR)

- close and seal crew cabin for the holidays

- crew cabin leak check

- close payload bay doors for the holidays

- power off Space Shuttle vehicle for the holidays


WORK SCHEDULED:

- Pad B securing and walkdown for the holidays

- Complex 39 facility and system annual preventative maintenance


                              # # #
     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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12/23/92: NASA NAMES MINORITY BUSINESS RESOURCE ADVISORY COMMITTEE MEMBERS

Donald L. Savage
Headquarters, Washington, D.C.              December 23, 1992



RELEASE:  92-230

     NASA Administrator Daniel S. Goldin today announced the names of the
Chairman and 23 members selected to serve on the newly-formed NASA Minority
Business Resource Advisory Committee.

     The committee, comprised of members of the business community, will help
NASA identify more small, disadvantaged and women-owned firms which potentially
could do business with the space agency.  NASA has a goal of awarding 8 percent
of its contracts to small disadvantaged businesses (SDBs) by the end of fiscal
year 1994.

     "This committee will help disprove the notion that there are no high-tech
small and disadvantaged businesses.  We know they're out there, and we'll find
them and nurture them because we want to work with firms that have the desire
to reach for the American dream," Goldin said in announcing the committee last
September.

     The committee's first meeting is tentatively scheduled for Jan. 26, 1993,
at NASA Headquarters, Washington, D.C. All regularly scheduled meetings will be
open to the public and will be announced in the Federal Register.

     Goldin selected Henry Wilfong as Chairman of the committee.  Susan Borgo,
a NASA Headquarters employee, is the Executive Secretary.

     Wilfong is the former Associate Administrator for the U.S. Small Business
Administration; a former member of the Presidential Task Force on International
Private Enterprise- Agency for International Development, U. S. Dept. of State;
and former City Councilman, Pasadena, Calif. He is a Certified Public
Accountant and owned a CPA firm from 1963- 1983.  He currently is President of
Wilfong and Co., a small businesses consultant.

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     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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12/23/92: NASA EXCEEDS SMALL DISADVANTAGED BUSINESS CONTRACTING GOAL


Donald L. Savage
Headquarters, Washington, D.C.              December 23, 1992



RELEASE:  92-231

     NASA Administrator Dan Goldin today announced that the agency has exceeded
its 1992 goal of awarding 6.7 percent of the total value of the agency's prime
and subcontracts to small disadvantaged businesses.

     Over $865 million was awarded to minority organizations, representing 7.2
percent of the total $12 billion awarded during the last fiscal year.  In 1990,
NASA developed a plan to meet a goal of awarding 8 percent of the total to
small disadvantaged businesses (SDBs) by the end of fiscal year 1994.

     "This represents a major step forward to meeting and hopefully, exceeding
our 1994 goal in 1993," said Goldin. "We are continuing the momentum by
recently setting aside appropriate procurements for SDBs, including women-owned
firms, and we are developing an awards program for technical small businesses.

     "I have directed top NASA officials to take steps to substantively
increase SDB subcontracting in our top 100 contracts.  Also, I have made
reaching our 8 percent goal a part of the performance evaluations of NASA's
associate and assistant administrators and center directors," said Goldin.

     Other steps announced today to meet the goal are to direct that contract
consolidations which reduce prime awards to SDBs will be made only with the
concurrence of NASA's chief of staff and to challenge the Jet Propulsion
Laboratory, Pasadena, Calif., to double their SDB subcontracting in FY 1993.

    On Dec. 2, NASA announced that $310 million would be set aside under a
determinations and findings (D & F) to ensure that NASA reaches the goal.  The
D & F listed 26 requirements for contracts at NASA centers.

     The goal includes small disadvantaged businesses, women- owned businesses,
Historically Black Colleges and Universities and minority educational
institutions.  The congressionally-mandated goal was included in the FY 1990
NASA appropriations bill.

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     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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HERBIG-HARO OBJECTS/THE ORION NEBULA

SPACE SCIENCE SHORTS

Herbig-Haro Objects

    Among the many classes of astronomical objects known to astronomers,
Herbig-Haro Objects provide us with our closest example of how stars are born.

    Astronomers George Herbig and Guillermo Haro discovered these curious
objects in the 1950's while investigating several nearby nebulae and
star-forming regions.  They found more than 100 bright, but irregular knots of
glowing gas near dense, dark interstellar clouds.

    This discovery may sound rather unimpressive.  After all, a good
photograph of any bright nebula, such as the Orion Nebula, reveals many clumps
of gas within these vast luminous gas clouds.  However, Herbig-Haro objects are
peculiar for several reasons.

    They are usually quite small, and in some cases look like irregularly
shaped stars.  A careful study of Herbig-Haro Objects also shows that they
change in brightness over the course of several years.

    Hind's Nebula, one of the first to be studied in detail, was first
detected in 1852; it disappeared in 1868, and then was rediscovered in 1890
with a telescope nearly five times larger than the one used initially.

    This type of behavior for a nebula was unprecedented.  During the
1950's, astronomers believed variable Herbig-Haro Objects were fledgling infant
stars struggling to light their nuclear furnaces.  But the theory ultimately
proved incorrect.

    By analyzing the light from Herbig-Haro objects through a spectroscope,
astronomers discovered that they contained hot gases, such as oxygen, nitrogen,
iron and hydrogen, that had been ionized or stripped of one or more electrons.

    This would have been consistent with the hot gases near a forming star,
but the rest of the light from the young star was missing completely.  This
would be like seeing the faint corona of the Sun, but not seeing its blinding
disk of light.  These objects couldn't be individual young stars after all;
instead they resembled shock wave-heated gas.

    Where did the shock waves come from?  At first, scientists thought that
the shock waves came from the nearby T Tauri-type stars nearly always found
near Herbig-Haro objects.  Stars of the T-Tauri class are variable, and produce
powerful ionized-gas winds, which travel at thousand of miles a second.  When
these winds collide with nearby clumps of gas, they shock the gases, causing
the ionization.

    This very plausible explanation did not explain why, for example, the
brightness changes in the stars did not match the brightness changes in the
accompanying Herbig-Haro Object. Scientists believed that any flareup on the
star should cause changes in the strength of the wind coming from its surface.


    If the theory were accurate, the change would show up several years
later in a brightening of the accompanying Herbig-Haro Object. When these
correlated brightness changes failed to happen, astronomers began to question
the stellar wind explanation.

    The infrared and radio observations later showed the faint but
unmistakable light from sources buried deep within dark clouds of interstellar
gas near the Herbig-Haro objects.  Astronomers soon identified them as the heat
from infant stars no more than 100,000 years old.

    This new puzzle piece now leads to the modern story of star formation.
Once a star forms, it ejects powerful jets of gas into space.  These jets
collide with clumps of gas in the environment of the forming star and cause
shock waves in the gas.

    The gas becomes ionized and glows in the manner characteristic of
Herbig-Haro Objects. The star, itself, is completely hidden from view to
astronomers using optical telescopes.

    The presence of variable T Tauri stars nearby only means that other
stars have gone through this process within the same dust cloud and now are
visible.

 The Orion Nebula

    This great cloud of interstellar gas some 1,500 light years from Earth
also is called Messier 42.  One of the most spectacular objects visible to the
naked eye beyond our solar system, the Orion Nebula has been the subject of
thousands of scientific papers and symposia.

    Although it appears as a simple cloud of gas, it contains an assortment
of objects, including the Orion Molecular Cloud, the Trapezium stars, T-Tauri
stars, Herbig-Haro objects...and PIGs.

    The gas cloud, itself, is only a surface blemish on a much larger dark
gas cloud called the Orion Molecular Cloud. This larger celestial body, which
spans a distance of about 10 light years, is located behind the smaller cloud
(as seen from Earth). Within the Orion Molecular Cloud, dust grains glow from
the heat of hundreds of luminous, recently formed stars detectable only by the
infrared light they emit.

    Near the surface of the Orion Molecular Cloud, on the side that faces
Earth, a cluster of young, luminous stars has begun to burn away the gas that
once enveloped it.  These stars, called the Trapezium, are each thousands of
times more luminous than the Sun, with surface temperatures of close to 30,000
K.  They are so hot, in fact, that they emit most of their radiation in the
form of    ultraviolet light.  This radiation has a devastating effect on any gas
and dust in the vicinity.

    It causes the gas surrounding the stars (up to five light years away)
to glow in green, blue, red and yellow.  Dust grains are destroyed and great
shock waves are driven out from the Trapezium, forming the delicate filaments
we see in optical photographs.

    The Orion Nebula isn't just a birthplace for stellar giants, like the
stars making up the Trapezium. Throughout the Nebula and its vicinity,
astronomers also have identified hundreds of so-called "T Tauri" stars -- stars
with about the same mass as our Sun, but probably no more than a few hundred
thousand years old.  These stars often are referred to as Pre-Main Sequence
(PMS) stars.

    Curious features known as "Herbig-Haro Objects" also have been seen,
which implies that the Orion Nebula is the birthplace of stars resembling our
own Sun (see related space science short).

    Among the most exciting recent discoveries made by ground-based
telescopes is the discovery of small clumps of gas not much larger than our own
solar system.  In 1987 using the Very Large Array Radio Telescope in New
Mexico, astronomer Edward Churchwell, of the University of Wisconsin, counted
dozens of these "radio stars." They subsequently were dubbed
partially-ionized globules ("PIGs") by Guido Garay at the European Southern
Observatory in Chile.

    HST has now confirmed that PIGS are, in fact, protoplanetary disks.
They recently formed within the Orion Molecular Cloud, and are now coming into
view as the material disperses in the cloud facing Earth.

    The intense ultraviolet radiation from the Trapezium stars appears to
be ionizing and evaporating the PIGS, perhaps before they will have had time to
form into stars and eventually planets.

Protoplanetary Disks (Proplyds)

    For more than a century, astronomers have suspected that planets evolve
from great, circulating clouds of dust and gas.  Since mathematicians first
proposed the idea in the 19th century, detailed calculations seem to bear out
this belief.

    Stars form from clumps of dense gas in what astronomers call vast
interstellar clouds.  As these clumps collapse under their own weight, they
form flattened, rotating disks, with most of the matter located in the central
regions.  After millions of years, the central region of the disk collapses to
form an infant star.

    The remaining gas and dust in the disk, which extends many times the
diameter of our own solar system, circulates around the young star.  It is
within this remaining material that the conditions appear ideal for planet
forming.

    Theories predict that the disk's inner regions are very hot as
tremendous frictional energies within the rapidly moving gas dissipate into
heat.  More distant reaches, however, are only tens of degrees above absolute
zero.  Over this great range of temperatures, chemical reactions give birth to
a variety of compounds out of which the forming planets will later evolve.

    One of the exciting features of these theoretical models is that they
predict the compositions of planets.  For example, within an Earth-like orbit,
where temperatures reach nearly 1500 K, planets consisting of water ice could
not form, but rocky planets rich in silicon and iron compounds could.  At
distances beyond Jupiter's orbit, on the other hand, the chemistry will favor
planets made of various ices, as is the case of Jupiter and Saturn's moons.

    Despite the theoretical models, up until 10 years ago no astronomer had
ever seen a protoplanetary disk -- the largest structure believed to harbor
forming planets.  This all changed with the advent of sensitive ground-based
observatories and the Infrared Astronomical Satellite, launched in 1983.  While
exploring nearby star forming nurseries, astronomers began to discern the
flattened, disk-like shapes of the material located around very young stars.

    They also began to detect with increasing frequency great jets of cold
gas being ejected at hundreds of thousands of miles per hour from these young
stars.  The disks themselves contained more than enough matter to make hundreds
of planets like Jupiter.

    Closer to home, astronomers also began to uncover in orbit around
dozens of nearby stars, such as the bright summertime star Vega, the feeble
vestiges of what may once have been these protoplanetary disks or proplyds.
These disks of rubble extend nearly 100 times the diameter of our solar system,
and curiously contain very little material at their centers.  Could planets
have formed around these stars, leaving behind only a few stray asteroids?

    How do planets form?  No one knows for certain especially since
astronomers have yet to observe what a young planet looks like.  However,
theoreticians predict that they form by the accumulation of dust and gas within
these protoplanetary disks.

    First, the microscopic dust grains collide and stick together, growing
into clumps several inches across.  Then these clumps fall into the mid-plane
of the disk, where they continue to collide until they become planet-sized
bodies.     The entire process is believed to take only a few hundred thousand
years from dust grain to planet.

    The predictions also suggest that planet formation requires a delicate
balance between many opposing forces.  If the collisions between the clumps are
too violent, planets would be shattered as fast as they are being built.  If
the disk is too close to a very luminous star, the star's radiation might
evaporate the disk before any planet had a chance to form.
     Source:NASA Spacelink    Modem:205-895-0028  Internet:192.149.89.61
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