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National
Aeronautics and Space Administration
HESSI Mission
Dolores
Beasley Susan
Hendrix George
Diller Robert
Sanders For Release: June 1, 2001 Back to top Dolores
Beasley Susan
Hendrix HESSI SPACECRAFT TO STEAL SECRETS OF SOLAR EXPLOSIONS WITH X-RAY VISION A new NASA spacecraft will soon be studying gigantic explosions in the atmosphere of the Sun with a unique kind of X-ray vision, producing the first high-fidelity color movies of solar flares in their highest energy emissions. "The Sun has a trick that nobody totally understands," said Dr. Richard Fisher, Chief of the Laboratory for Astronomy and Solar Physics at NASA's Goddard Space Flight Center, Greenbelt, MD. "It can take magnetic energy and turn it into a stunningly powerful blast of heat, light and radiation. NASA’s High Energy Solar Spectroscopic Imager (HESSI) will finally unlock the secrets of the initiation and onset of flares." HESSI is scheduled to take off at 9 a.m. EDT June 7 from Cape Canaveral Air Force Station, FL aboard a Stargazer L-1011 aircraft. The Stargazer cradles HESSI under its belly, stored inside a Pegasus rocket. At 10:05 a.m. EDT, the aircraft should release the Pegasus and deliver the spacecraft to its circular orbit 373 miles (600 kilometers) above the Earth, inclined at 38 degrees to the equator. Within the gigantic flare explosions, magnetic fields twist, snap and recombine, blasting particles to almost the speed of light and firing solar gas to tens of millions of degrees. This action causes the solar atmosphere to sizzle with high-energy X-rays and gamma rays and accelerates proton and electron particles into the solar system. Radiation and particles from solar flares sometimes affect spacecraft, interfering with communications, and astronaut activities. In order to understand what triggers a solar flare and how it explosively releases energy, scientists must identify the different kinds of particles being accelerated, locate the regions where the acceleration occurs and determine when the particles get accelerated. The most direct tracer of these accelerated particles is the X-ray and gamma ray radiation they produce as they travel through the solar atmosphere. To understand the physical processes and conditions inside flares, HESSI will create images in gamma rays and the highest energy X-rays emitted by the flare. These images will be the first to simultaneously measure the location and energy content of radiation from the flare material. This kind of data is expected to improve predictability of flare occurrence at the Sun and the subsequent consequences we experience here on Earth. Using the Sun as a laboratory, where such high-energy events take place, will provide scientists insight into interpreting similar high-energy activity that originates elsewhere in the universe. Because HESSI has the finest angular and spectral resolution of any hard X-ray or gamma ray instrument ever flown in space, it will enable researchers for the first time to look at the development of high-energy reactions in flares. Powerful X-rays and gamma rays penetrate all materials to some extent, and cannot be easily focused, so researchers are using another technique to form images. HESSI’s sole instrument – an imaging spectrometer – will construct a flare image from patterns of light and shadows produced by high-energy radiation that passes through the telescope’s grids while the spacecraft rotates. Using this new method, HESSI is expected to gather data on thousands of flares during its two-to-three-year mission. Working together with other solar spacecraft – Yohkoh, the Solar and Heliospheric Observatory (SOHO), Geostationary Operational Environmental Satellites (GOES), and the Transitional Regional and Coronal Explorer (TRACE) for flare radiation, and Wind, the Advanced Composition Explorer (ACE), Ulysses, and Voyager for particle detection – HESSI will provide vital insight into the impulsive energy release and particle acceleration processes at the Sun. The HESSI mission cost about $85 million, which includes the spacecraft, launch vehicle, mission operations and data analysis. NASA’s Office of Space Science, Headquarters, Washington, DC, provided funding for HESSI, and the Explorers Program Office at Goddard provides management and technical oversight for the mission. For more information on the Internet about the spacecraft and science mission, go to: http://hesperia.gsfc.nasa.gov/hessi http://hessi.ssl.berkeley.edu/ Media Services Information Back to top NASA Launch Coverage NASA
TV will provide live coverage and commentary of the HESSI launch June 7 beginning
about 8 a.m. EDT. The L-1011 Stargazer aircraft is scheduled to take off at A live webcast of the take off and drop will be available from KSC’s web site at: www.ksc.nasa.gov Press Briefings A pre-launch press conference will be held at KSC on L-1 beginning at 12:30 p.m. EDT to discuss details of the launch vehicle, spacecraft readiness and weather for launch day. A science briefing will immediately follow - beginning about 1 p.m. EDT - to address the science payload and science objectives for the HESSI mission. News Center/Status Reports NASA Public Affairs will staff the News Center at KSC beginning on L-2 and continuing about two hours after a successful launch. Recorded status reports also will be available beginning two days before launch by dialing 321-867-2525 or 301-286-NEWS. Media Credentials Media seeking launch accreditation should fax their requests at least two days prior to launch to: George
Diller, KSC/PAO ***Requests must be submitted on the letterhead of the news organization and specify the editor making the assignment to cover the launch***
HESSI Quick Facts Back to top Spacecraft Payload HESSI’s sole instrument – an imaging spectrometer – will construct a flare image from patterns of light and shadows produced by high-energy radiation that passes through the telescope’s grids as the spacecraft rotates. The spectrometer separates the light electronically into its component "colors," which correspond to different wavelengths and energy levels. X-ray and gamma-ray detectors onboard the spacecraft count the number of photons passing through the grids and measure their energy very precisely. When combined with the imaging information, scientists can reconstruct high-resolution "color" pictures of solar flares using computers back on the ground. This new approach will significantly advance our understanding of the solar flare phenomenon. Spacecraft Dimensions HESSI measures 85 inches tall (2.16 m) by 227 inches wide (5.76 m) after solar panel deployment. During launch, the spacecraft’s solar panels are folded to 43.3 inches (1.1 m) in width in order to fit inside the Pegasus rocket fairing. Spacecraft Weight – 645 lbs. (293 kg) Science Payload – X-ray and gamma-ray imaging spectrometer Onboard Memory – 4.0 gigabytes Spacecraft Telemetry – Up to 2 gigabytes/day Mission Lifetime – Two to three years Orbit – 373-mile (600-kilometer) circular orbit, inclined at 38 degrees to the equator. Launch Site – Cape Canaveral Air Force Station, Fla. Take off and Pegasus Drop – June 7, 2001 at 9 a.m. EDT. Pegasus drop scheduled for 10:05 a.m. EDT. Launch Vehicle – A Pegasus XL rocket, Orbital Sciences Corporation. Additional information can be obtained from their web site at: http://www.orbital.com/LaunchVehicles/Pegasus/pegasus.htm First Signal Acquisition – Should occur about 80 minutes after the L-1011 aircraft is airborne. Mission Costs – Total mission costs are approximately $85 million for the spacecraft, instrument payload, launch vehicle, data analysis, ground operations and mission operations. Mission Oversight –HESSI is the sixth Small Explorer (SMEX) mission. The Explorers Program Office at Goddard provides management and technical oversight for the mission in accordance with NASA’s Office of Space Science in Washington, DC. Spacecraft and Instrument Design/Operation – The University of California, Berkeley (UC Berkeley), as principal investigator institution for this mission is responsible for most aspects of the mission, including the instrument and spacecraft, integration and environmental testing of the spacecraft, and operations and data analysis after launch. The instrument was a joint effort involving UC Berkeley, the Lawrence Berkeley National Laboratory, GSFC, and the Paul Scherrer Institut in Switzerland. Spectrum Astro, Inc., of Athens, Ohio built the HESSI spacecraft. Launch Operations – Kennedy Space Center is responsible for launch operations at Cape Canaveral Air Force Station. Payload Operations Centers – The mission and science operations centers are located at UC Berkeley’s Space Sciences Laboratory.
HESSI Science Objectives Back to top Solar flares, which occur in the atmosphere of the Sun, are the solar system’s most powerful eruptions. During a flare, large numbers of electrically charged particles are rapidly accelerated to high energies and gas is quickly heated to tens of millions of degrees. Studying solar flares is essential because they are often accompanied by the eruption of gas and energetic particles from the Sun called coronal mass ejections. These energetic particles can be particularly dangerous to spacecraft that leave the protection of the Earth’s magnetic field. X-rays from flares can alter the structure of the Earth’s ionosphere (electrically charged upper atmosphere), affecting radio communications that depend on reflection by the ionosphere for transmission to distant receivers. This mission will allow researchers to find out where in the solar atmosphere these particles are accelerated, when in the flare explosion the particle acceleration occurs, and what energies are achieved by the accelerated particles, vastly advancing our understanding of the fundamental high-energy processes that produce solar flares. Pegasus Rocket Line Drawing Back to top
(Image courtesy of Orbital Sciences Corporation)
HESSI Spacecraft Image Back to top
NASA Management: Headquarters Office of Space Science: Science Program Director/Sun-Earth Connection - Dr. George Withbroe HESSI Program Scientist - Dr. William J. Wagner HESSI Program Manager - Dr. George G. Albright
Goddard Space Flight Center: HESSI Mission Manager - Frank Snow, Explorers Program Office HESSI Mission Scientist - Dr. Brian Dennis, Laboratory for Astronomy and Solar Physics
UC Berkeley Project Management: HESSI Principal Investigator - Dr. Robert Lin, Space Sciences Laboratory HESSI Project Manager - Peter Harvey, Space Sciences Laboratory HESSI Spacecraft Manager - Rick Wanner, Space Sciences Laboratory
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