| Article 35037
From: [email protected] (Peter E. Yee)
Newsgroups: sci.space
Subject: Solar-A Launched (Forwarded)
Date: 30 Aug 91 08:23:03 GMT
Sender: [email protected] (USENET Administration)
Organization: NASA Ames Research Center, Moffett Field, CA
[Also forwarded for Yoshiro Yamada of the Yokohama Science Center. -PEY]
* The Solar-A Launched *
According to ISAS (Institute of Space and Astronautical Science),
The Solar-A spacecraft was launched at 02:30 UTC on August 30
and put to orbit with the following parameters:
-- perigee 520 km
-- apogee 770 km
-- orbital inclination 31.3 deg
-- period 98 min.
Solar-A was nicknamed 'YOHKOH' (sunlight) after launch.
Equipment installed in the spacecraft is functioning normally.
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(The following description on Solar-A is based on fax message
from Y. Ogawa, ISAS.)
The Solar-A spacecraft carries instruments for the observation
of solar flares in X- and gamma- radiation. The primary experi-
ments will make high-resolution images of flares in hard X-
rays (15-100 keV) and soft X-rays (4-40 angstrom);the former uses
Fourier-transform op- tics and the latter a grazing-incidence
telescope with a "super- polish" finish. The soft X-ray telescope
features a 1024 x 1024 virtual-phase CCD as its image
readout device. In addition to these experiments, two other in-
struments will observe the soft X-ray emission-line spectrum
and obtain the time series of hard radiations from flares. The
Solar-A scientific instrumentation has a strongly international
flavor, with instruments provided by the U.S. and the U.K.; as
the only solar-flare satellite in this exceptional maximum of
solar activity, we expect that Solar-A will be the focus of con-
siderable scientific interest.
To accomplish these objectives, a spacecraft with three-
axis stabilization is required. Solar-A will be the first ISAS
spacecraft with three-axis stabilization of sufficient precision
for the accurate pointing of high-resolution telescopes; the re-
quirement on stability rate of 1 arc sec/sec on short time
scales, and 7 arc sec/min to permit long integrations of faint
soft X-ray sources. A magnetic bubble data recorder will permit
the storage of 80 Mb per readout cycle; a combination of
telemetry readouts at the ISAS Kagoshima Space Center and NASA's
Deep Space Network will allow us to dump this data recorder
approximately once per orbit (96 minutes), permitting regular
coverage the evolving solar structures.
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Post-Launch Status Report (9/24/91)
Project officials at the Marshall Space Flight Center in
Huntsville, Ala. report that NASA's Soft X-Ray Telescope is
operating routinely and the telescope continues to collect solar
data 5-6 orbits a day as it proceeds through scientific checkout
procedures.
Telescope project manager John Owens at Marshall Center that
"all spacecraft activation and control operations are continuing
successfully at Kagoshima Space Center in Southern Japan. On
Sept. 10, the scientists started taking their first scientific
test images of the Sun. We hope to have all spacecraft
instruments up and collecting science by October 1."
The telescope is one of four instruments aboard the Yohkoh
spacecraft that was launched into Earth orbit aboard a Japanese
launch vehicle August 30 by the Institute of Space and
Astronautical Science (ISAS) from Kagoshima.
Yohkoh, which means sun-beam in Japanese, is currently in an
orbit inclined 31-degrees to the equator at an altitude of 490 X
315 nautical miles (719 X 506 kilometers). Its orbital period is
98 minutes.
The purpose of YOHKOH is to study high energy phenomena in
solar flares during the current solar maximum period. The mission
will last for three years, according to NASA officials.
Other instruments flying on the spacecraft are the Japanese
Hard X-Ray Telescope, the Bragg Crystal Spectrometer from the
United Kingdom, and the Wide-Band Spectrometer from Japan.
The Marshall Center Payload Projects Office was responsible
for managing the development of the Soft X-ray Telescope that was
built by Lockheed Palo Alto Research Laboratory in Palo Alto,
Calif. The instrument was integrated into the spacecraft in Japan
by the Nippon Electric Company of Japan, the spacecraft
manufacturer.
Under a co-operative agreement between NASA and ISAS of
Japan, Dr. Loren Acton of Lockheed Palo Alto Research Lab in
California is the U.S. principal investigator, and Professor
Tadashi Hirayama of the Tokyo Astronomical Observatory, Japan, is
the Japanese principal investigator. U.S. co-investigators for
the Soft X-ray Telescope are from Stanford University, Calif., the
University of Hawaii and University of California at Berkeley.
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| Michael Braukus
Headquarters, Washington, D.C. September 30, 1991
EDITORS NOTE: N91-68
The Soft X-ray Telescope, one of four instruments on the Japanese
Solar-A spacecraft launched Aug. 30, 1991 from Japan's Kagoshima Space
Center, has taken its first soft X-ray image of the Sun. A prime purpose of
the Solar-A mission is to study high energy phenomena in solar flares
during the current period of maximum solar activity. The spacecraft was
named Yohkoh after successfully achieving orbit. Yohkoh means sun-ray or
sun-beam in Japanese. The Soft X-ray Telescope is the product of
international collaboration between the U.S. and Japan.
The photograph shows the intricate structures of the X-ray corona,
which extend far above the sun's surface. The sun's magnetic field
constrains the hot coronal gases along loop-like structures in so-called
"magnetic bottles". Brightness of the loops reflects temperature and
density of gasses they contain.
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