Re-scheduled launch of HESSI on Feb. 5 leaves scientists optimistic that satellite can meet scientific objectives despite delay

Press Release From: University of California Berkeley
Posted: Friday, February 1, 2002

NOTE: Check below for a detailed agenda of pre-launch press briefings and launch-day activities.

Berkeley - The long-delayed launch of a UC Berkeley/NASA satellite to study violent explosions on the sun is now set for next Tuesday, Feb. 5, from the belly of an Orbital Sciences Corp. plane over the Atlantic Ocean.

The High Energy Solar Spectroscopic Imager, or HESSI, designed, built and operated by an international consortium led by scientists at the University of California, Berkeley, will embark on a two- to three-year mission to look at high-energy X-ray and gamma ray emissions from solar flares. Though various satellites have made X-ray and gamma ray observations of flares, which are enormous explosions in the solar atmosphere, HESSI will be the first to snap pictures in gamma rays and the highest energy X-rays.

HESSI was originally scheduled for launch in July 2000, but was postponed after the satellite suffered damage during vibration testing. Since then, flight delays due to launch vehicle failures have affected the launch date. However, officials have since cleared the way for next Tuesday's scheduled launch.

Robert P. Lin, professor of physics in the College of Letters & Science at UC Berkeley and principal investigator for the mission, is optimistic that HESSI will achieve its original scientific goals.

"We were aiming for the peak of solar activity in mid-2000, so we have been lucky that, with the slip of our launch date by a year and a half, solar activity has continued to stay high," Lin said. "The sun had another peak of activity at the end of 2001. We still think we will image around a thousand solar flares, though whatever we see will be new and interesting."

HESSI, whose total mission cost is $85 million, is the sixth Small Explorer (SMEX) spacecraft scheduled for launch under NASA's Explorers program.


NOTE: Details of the mission and the physics of solar flares can be found on the Web at UC Berkeley's news site, NASA's HESSI press kit is available at

Robert Lin can be reached at (510) 642-1149 or Brian Dennis can be reached at the Laboratory for Astronomy and Solar Physics, Goddard Space Flight Center, (301)286-7983 or at

For information from NASA Goddard, contact Susan Hendrix at (301) 286-7745.

Also check out UC Berkeley's HESSI Mission Web site at

Hessi's education Web site is at


WHAT: At Kennedy Space Center, a combination mission and science briefing. Participants will discuss the overall mission, the launch vehicle, spacecraft health, and timeline between separation from the Pegasus rocket through start of science operations. Scientists will discuss details of the science payload and science objectives for the mission.

NASA will provide live broadcast via NASA-TV. The news conference also will be streamed through the web from the KSC Web site at

WHO: Robert P. Lin, UC Berkeley principal investigator for HESSI
Brian Dennis, HESSI mission scientist at Goddard
Bill Wagner, NASA's Sun-Earth Connection program manager

NOTE: West Coast reporters may view the Florida news briefing from the conference room at the University of California, Berkeley's Space Sciences Laboratory beginning at 10:30 a.m. PST. Several HESSI scientists will be at the lab. The lab is at the top of Centennial Drive near its intersection with Grizzly Peak Boulevard. Please check in at the front office for parking permit.



WHAT: Live NASA-TV coverage and commentary of the HESSI launch, including L-1011 take-off from Cape Canaveral, Fla., and drop of the Pegasus rocket. The launch as seen from a chase plane will be on NASA-TV or on the Web at

WHEN: Coverage begins at about 2:00 p.m. EST. L-1011 take off is at 2:30 p.m., with Pegasus drop scheduled for 3:26 p.m. EST.


WHAT: Viewing of the launch at UC Berkeley's Space Sciences Laboratory via live satellite feed from NASA-TV. HESSI scientists in the Mission & Science Operations Center (MSOC) will provide regular updates. The main update will be given after the satellite's first pass over Berkeley, at about 2 p.m. PST. By then, HESSI scientists should have information about the health of the spacecraft.


Robert P. Lin, HESSI principal investigator, UC Berkeley professor of physics, director of UC Berkeley's Space Sciences Laboratory
Manfred Bester, lead scientist in HESSI Mission Operations Center, UC Berkeley
David Smith, spectrometer development scientist, UC Berkeley

WHEN: 10:30 a.m. - 3 p.m. PST

WHERE: Conference room, first floor of Silver Laboratory Addition, UC Berkeley.


NOTE: Recorded status reports will be available beginning Sunday, Feb. 3, at (321) 867-2525 or (301) 286-NEWS.

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