UCB/NASA Solar Flare Study Satellite to Launch on June 14

June 1, 2001

Contact: Robert Sanders, UC Berkeley Public Information Office
510-643-6998, rls@pa.urel.berkeley.edu

Contact: Susan Hendrix, NASA’s Goddard Space Flight Center,

BERKELEY, CA--A satellite dedicated solely to the study of solar flares, designed, built and operated by an international consortium headed by scientists at the University of California, Berkeley, is set for launch on Thursday, June 7, by the National Aeronautics and Space Administration (NASA).

The High Energy Solar Spectroscopic Imager, or HESSI, will embark on a two- to three-year mission to look at high-energy X-ray and gamma ray emissions from solar flares--enormous explosions in the solar atmosphere. Though various satellites have made X-ray and gamma ray observations of flares, HESSI will be the first to snap pictures in gamma rays and the highest energy X-rays.

“With intense flares, we can take X-ray images with very high resolution, very fast, and create movies of flares lasting from 10 seconds to tens of minutes,” said Robert P. Lin, professor of physics in the College of Letters and Science at UC Berkeley and principal investigator for the mission.

Using these images, plus X-ray and gamma-ray spectra with unprecedented energy resolution, the scientists hope to discover what triggers flares and how energy stored in the solar magnetic fields is suddenly released to accelerate particles to very high speeds and to heat the gases in the solar atmosphere to tens of millions of degrees.

“From these hard X-ray and gamma-ray measurements, we can reconstruct the energy distribution of the particles and trace back to where everything was accelerated,” Lin said.

The mission begins near the peak of the sun’s 11-year cycle of activity, providing an unprecedented opportunity for study of these explosive events. What scientists learn will give insight into the processes that accelerate other particles whizzing at nearly light-speed through the universe.

HESSI is the sixth Small Explorer (SMEX) spacecraft scheduled for launch under NASA’s Explorers Program. Total cost for the mission, including the spacecraft, launch vehicle and mission operations, is about $85 million.

Solar flares, along with the often associated explosions called coronal mass ejections, are the solar events that most affect “space weather.” The intense energy associated with these events--up to the equivalent of a billion megatons of TNT--and the energetic particles they throw out impact the Earth’s magnetic field, compressing it and interfering with radio communications on Earth. Astronauts and cosmonauts aboard the International Space Station or the Space Shuttle also can receive dangerous doses of radiation from the high-energy particles.

“Coronal mass ejections sometimes have flares associated with them and sometimes don’t,” said Brian Dennis, HESSI mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “We don’t understand why this should be or what the relationship is between these two types of events.”

The 645-pound (293 kilograms) HESSI satellite will be launched atop a Pegasus XL rocket dropped from the belly of an L-1011 aircraft flying out of Cape Canaveral Air Force Station, Florida. After the plane reaches an altitude of about 40,000 feet over the Atlantic Ocean, the rocket will be released to free-fall in a horizontal position for about five seconds before igniting its first stage motor. The three-stage rocket will place the spacecraft into a circular orbit about 373 miles (600 kilometers) above the Earth, inclined at 38 degrees to the equator.

Once in orbit, the satellite comes under UC Berkeley’s control, with commands uplinked and data downlinked through a 36-foot (11 meters) radio dish perched in the wooded hills above UC Berkeley. From mission control in the nearby Space Sciences Laboratory, HESSI mission operators will monitor the automatic pointing of the satellite toward the sun, deployment of the four solar panels, and the spin-up of the satellite to about 15 revolutions per minute.

HESSI is the first Small Explorer (SMEX) spacecraft to be managed in a way that gives the principal investigator--in this case, Robert P. Lin, director of UC Berkeley’s Space Sciences Laboratory--responsibility for most aspects of the mission. This includes not only the scientific instrument but also the spacecraft, integration, all environmental testing, and operations and data analysis after launch. The Explorers Program Office at Goddard provides management and technical oversight for the HESSI mission under the direction of the Office of Space Science at NASA headquarters in Washington, D.C.

For more detail, link to UC Berkeley information at http://www.berkeley.edu/news/media/releases/2001/06/01_hess1.html or Goddard Space Flight Center information at http://hesperia.gsfc.nasa.gov/hessi/index.html

Editor’s notes:

Robert Lin can be reached at 510-642-1149 or boblin@ssl.berkeley.edu

Brian Dennis can be reached at the Laboratory for Astronomy and Solar Physics, Goddard Space Flight Center, 301-286-7983 or at Brian.R.Dennis.1@gsfc.nasa.gov.

Video is available both from NASA and UC Berkeley.

The NASA video file includes HESSI spacecraft animation, footage of spacecraft testing at JPL and the imager assembly at the Paul Scherrer Institut, plus interviews with Lin and Dennis. Also included are solar max and solar flare images captured by the Solar and Heliospheric Observatory (SOHO) spacecraft.

UC Berkeley has video interviews of Lin and fellow scientists Peter Harvey and Manfred Bester.

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