Berkeley – An ultraviolet telescope designed and built in a
collaboration between University of California, Berkeley, and South
Korean scientists is scheduled for a Sept. 26 launch from Russia as
the main payload of South Korea’s first scientific satellite.

According to UC Berkeley astrophysicist Jerry Edelstein, the primary
payload, called Spectroscopy of Plasma Evolution from Astrophysical
Radiation (SPEAR), will capture the first far ultraviolet pictures of
hot and glowing gas in the Milky Way galaxy, providing clues to the
course of the galaxy’s evolution.

SPEAR will measure the glow over the whole sky from gas between the
stars that has been heated by supernova blast waves, blazing hot
stars and colliding interstellar clouds.

The experiment will fly aboard the Korean STSAT-1 (Space and
Technology Satellite 1), which will carry other experiments to
measure energetic particles bombarding the Earth’s atmosphere and
causing auroras. SPEAR also will work in conjunction with these
experiments by looking downward to capture the auroral ultraviolet

In the violent ebb and flow of gas within the Milky Way galaxy, the
death of stars is marked by supernova explosions belching out
1,000,000 degrees Kelvin gas bubbles moving in blast waves at 500,000
miles per hour (200 km/sec). The hot gas smashes into surrounding
galactic matter, slowing and somehow cooling into wispy interstellar
clouds of a mere 10,000 degrees Kelvin. Completing the galactic life
cycle, the gas finally condenses into massive, thick and frigid 10
degree Kelvin clouds that ultimately collapse with gravity, birthing
new stars.

While satellites such as Chandra have seen the X-ray glow from the
million-degree Kelvin gas, and the Hubble Space Telescope has
produced beautiful pictures of the cooler 10,000 degrees gas glowing
in visible light, the telltale ultraviolet glow from galactic gas at
the “warm” in-between temperatures – from 30,000 to 500,000 degrees
Kelvin – is barely understood, Edelstein said.

“Supernovas inject energy into the galaxy, and we’re looking at what
happens to that energy over the life cycle of the galaxy,” said
Edelstein, a senior fellow at UC Berkeley’s Space Sciences
Laboratory. “We know where the hot and cold stuff are, but how you
get from hot to cold has been a mystery for 40 years.”

These data will help astronomers determine what the Milky Way galaxy
looks like. Is it filled with bubbles of hot gas created by
supernovas, much like a Swiss cheese, or do the supernovas blow hot
gas out of the disk of the galaxy which then cools and falls back
into the disk like a fountain? Alternatively, does the hot gas mingle
into the galactic disk, creating a glowing plasma that permeates the
middle of the galaxy?

“We know that warm gas exists in the galaxies, but we don’t really
understand where. The only way to find this stuff is to look in the
ultraviolet. SPEAR will map the ultraviolet sky glow from atoms of
hot oxygen, carbon and nitrogen gas, showing us both where this gas
is and how it cools off,” Edelstein said.

Because cooling plays a role on a larger scale in the evolution of
galaxies, SPEAR may also provide clues to the origins of large-scale
structure in the universe. It may be that the “voids” found in the
distant universe are actually filled with gas at a temperature of
around 100,000 Kelvin and will glow in the ultraviolet.

In January, NASA launched a small UC Berkeley satellite called CHIPS
(Cosmic Hot Interstellar Plasma Spectrometer) to measure the
temperature of the low-density interstellar bubble of hot gas
surrounding the sun. SPEAR will complement CHIPS by completing the
thermal picture of the local region and extend this to the entire

The Korean STSAT-1 is one of six satellites to be launched aboard a
liquid-fueled Russian Cosmos rocket from Plesetsk cosmodrome,
Russia’s busiest launch site, located 400 miles northeast of St.
Petersburg. The Korean satellite, about the size of a washing
machine, was put together by the Korea Advanced Institute of Science
& Technology (KAIST), South Korea’s leading engineering university.

> From its orbit 440 miles (700 kilometers) above the Earth, SPEAR will
gaze away from the sun and, during the course of a year, steadily
scan a thin wedge of the sky from north to south, moving one degree
each day to complete a full-sky map in the far ultraviolet. For the
second year, SPEAR will stare at particularly fascinating features in
the sky that were identified in the all-sky survey.

SPEAR was designed by Edelstein and his Space Sciences Laboratory
colleagues, including project scientist Eric Korpela, in
collaboration with scientists at the KAIST’s Satellite Technology
Research Center (SaTReC) and the Korea Astronomical Observatory. The
instrument carries two photon-counting spectroscopes, each sensitive
to a different range of wavelengths in the far ultraviolet.
Edelstein’s Korean colleagues include Professor Kyoung Wook Min of
KAIST and Dr. H. W. Han of the Korea Astronomical Observatory.

The UC Berkeley SPEAR effort is funded by $1.5 million from the U.S.
National Aeronautics and Space Administration (NASA). The mission is
funded by additional monies from the Korean Ministry of Science and
Technology. The entire $13 million cost for payloads, satellite and
launch is about a quarter of the cost for a comparable U.S.-built
mission, Edelstein said. NASA funds for the SPEAR payload came
through the “research carriers” program that traditionally supports
the training of scientists and engineers using sounding rocket and
ballooning payloads.

The low cost of the mission means that the small UC Berkeley and
SaTReC teams often used off-the-shelf instead of custom-made parts,
but Korpela said that hard work and built-in redundancy will
hopefully make SPEAR reliable beyond its planned two-year mission

Edelstein has studied ultraviolet emissions from the sky for more
than 20 years, having participated in sounding rocket, space shuttle
and satellite missions such as that of UC Berkeley’s Extreme
Ultraviolet Explorer satellite. That satellite was launched in 1992
and, after a successful mission mapping the extreme ultraviolet
emissions from nearby hot gas, fell to Earth in 2002.


NOTE: Jerry Edelstein leaves for Russia on Sept. 16 and may be
difficult to reach until his return on Sept. 29. Reporters can try
e-mailing him at His office phone is (510)
642 0599; his U.S. cell phone is (650) 224 7274. His Iridium phone in
Russia will be 8816-2141-9505. Eric Korpela can be reached at (510)
643-6538 or via e-mail at