ARG%SU-AI@sri-unix.UUCP (11/23/83)
From: Ron Goldman <ARG@SU-AI>
a051 0327 23 Nov 83
PM-Satellite, Bjt,420
Orbiting Telescope Dying of the Heat
By HARRY F. ROSENTHAL
Associated Press Writer
WASHINGTON (AP) - NASA has announced the imminent, untimely death of
an orbiting telescope that is rewriting astronomy books. Age, 10
months. Cause of death: At 448 degrees below zero, it's overheating.
The focal plane on the Infrared Astronomical Satellite telescope has
to be cooled to a temperature of 2.5 degrees above absolute zero -
minus 455 degrees Fahrenheit. On Monday night the superfluid helium
used for cooling ran out and the focal plane - the point where the
image is in focus - began warming at the rate of four-tenths of one
degree an hour.
Since its launch last January, the Infrared Astronomical Satellite
has:
-Produced direct evidence that ours is not the only solar system.
-Discovered five comets and recorded more than 200,000 objects in
the heavens.
-Found three giant rings of dust in the solar system, huge dust
shells around the star Betelgeuse and a mysterious object - possibly
an asteroid or a dead comet - that passes nearer to the sun than any
planet or known asteroid.
-Successfully surveyed 95 percent of the sky, found a ring of solid
material around the star Vega, bands of dust around the sun between
the orbits of Mars and Jupiter, and taken a new look at our own
galaxy, the Milky Way.
-Returned more than 200 billion bits of data to Earth, allowing
scientists see beyond the dust veils that normally obscure stars in
formation or in their death throes.
As it moved through a polar orbit, 563 miles high above Earth, with
the telescope chilled properly, the telescope's infra-red detector
recorded radiation from cold masses of gas in space. From Earth, such
radiation is filtered out by the atmosphere and can't be measured.
Useful scientific observations can continue until the temperature
rises to minus 448 degrees, early next week.
The satellite, known as IRAS, was launched Jan. 25 carrying 165
pounds of refrigerant. Before launch, engineers estimated the helium
would last only seven months, but they revised their estimate after
seeing how much was being used, predicting the satellite would operate
into January 1984.
However, the Rutherford-Appleton Laboratories at Didcot, England,
which operates the IRAS tracking station, said IRAS depleted its
supply at 8:30 p.m. EST Monday.
''Considering the uncertainties in the calibration estimates in the
flow rate of helium usage, the achieved lifetime is within about 10
percent of predictions,'' NASA said.
IRAS is a joint venture of the United States, the Netherlands and
Great Britain. The United States contributed $150 million to the $200
million total cost.
ap-ny-11-23 0625EST
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