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The HETE-2 Mission

The HETE-2 Mission. D. Q. Lamb (U. Chicago). Outline of This Talk. HETE-2 Mission Goals and Program HETE-2 Spacecraft and Instruments French Gamma Telescope (FREGATE) (6-400 keV) Wide-Field X-Ray Monitor (WXM) (2-25 keV) Soft X-Ray Camera (SXC) (2-10 keV)

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The HETE-2 Mission

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  1. The HETE-2 Mission D. Q. Lamb (U. Chicago)

  2. Outline of This Talk • HETE-2 Mission Goals and Program • HETE-2 Spacecraft and Instruments • French Gamma Telescope (FREGATE) (6-400 keV) • Wide-Field X-Ray Monitor (WXM) (2-25 keV) • Soft X-Ray Camera (SXC) (2-10 keV) • Spacecraft and Instrument Operations • Summary of First Two Years of HETE-2 Mission • HETE-2 Mission Future

  3. Los Alamos National Laboratory Los Alamos, NM USA Center for Space Research Massachusetts Institute of Technology Cambridge, MA USA Edward E. Fenimore Mark Galassi George R. Ricker (PI) Geoffrey B. Crew John P. Doty Alan M. Levine Roland K. Vanderspek Joel Villasenor Space Science Laboratory University of California at Berkeley, CA USA Cosmic Radiation Laboratory Institute of Physical and Chemical Research (RIKEN) JAPAN Kevin Hurley J. Garrett Jernigan Masaru Matsuoka Nobuyuki Kawai Atsumasa Yoshida Astronomy and Astrophysics Department University of Chicago, IL USA Donald Q. Lamb Jr. Carlo Graziani Tim Donaghy Centre D’Etude Spatiale des Rayonnements (CESR) FRANCE Board of Astronomy and Astrophysics University of California at Santa Cruz, CA USA Jean-Luc Atteia Michel Boer Gilbert Vedrenne Stanford E. Woosley Goddard Space Flight Center Greenbelt, MD USA Brazil + India + Italy (Burst Alert Station Scientists) Joao Braga Ravi Manchanda Graziella Pizzichini Thomas L.Cline (NASA Project Scientist) HETE-2 International Science Team (Mission Scientist)

  4. High Energy Transient Explorer HETE ~ 1st Dedicated g-Ray Burst Satellite ~ Mission Goals And Program • GOALS: • Locate GRBs Accurately (~10' - 10" ) • Distribute Locations in Near Real-Time (~10 - 100 s delay) • Measure multi-wavelength spectra • [ Soft X-ray ~ -ray; 2 keV ~ 400 keV ] • PROGRAM: • University-managed; NASA +Japan+France • University-constructed spacecraft and ground stations • Mission of Opportunity • 1/3 cost of NASA Small Explorer (SMEX)

  5. HETE During Ground Testing

  6. French Gamma-ray Telescope (FREGATE): 5-400 keV; ~π FOV Wide-Field X-ray Monitor (WXM): 2-25 keV; ~5’-10’ localizations Soft X-ray Cameras (SXC): 2-10 keV; ~40” localizations Science Instrument Package

  7. HETE-2 Launch • HETE-2 was successfully launched on 9 October 2000 from Kwajalein in the Marshall Islands. • Launch vehicle was a Pegasus rocket. • HETE-2 is in an equatorial orbit.

  8. HETE-2 Primary and Secondary Ground Stations • Three primary ground stations and 14 secondary ground stations designed, built, and maintained by the HETE-2 science team. • When HETE-2 detects a GRB, burst alert is sent by VHF radio to secondary ground station, then via Internet to MIT and to 700 astronomers and observatories around the world. • Thus HETE-2 pinpoints location of burst and provides it in “real time” to the astronomical community.

  9. HETE-2 Operations • FREGATE is now always on; WXM now on for ~ 55 minutes/orbit • Spacecraft instruments generally point anti-sun (every GRB localized by HETE-2 can be observed by ground-based and space-based optical, radio, and X-ray telescopes) • During May-August when Galactic Plane would be in FOV of instruments, HETE-2 “head nods:” • Before dusk terminator and after dawn terminator, HETE-2 slews as much as 40 degrees in order to keep Galactic plane (and esp. Sco X-1) out of FOV of instruments • Head nodding may also be done at other times for calibration purposes (e.g., using the Crab nebula, Sco X-1, and XRB sources) • The direction that HETE-2 will be pointing during the next 6 orbits is always available (and can be automatically downloaded) from the HETE-2 website: http:space.mit.edu/HETE/

  10. Non-GRB Results from Two Years of HETE-2 Operations • Soft Gamma Repeaters (SGRs): • 25 SGR events in Summer 2001 (14 triggered + 11 untriggered) • SGR1806-20, SGR1900+14 • 2 SGR events in Summer 2002 • X-ray Bursts (most XRBs do not trigger; thus, no GCN Burst Alert): • ~670 X-ray bursts detected: • 170 in Summer 2001 • 500+ in June-August 2002 • ~20 different XRB sources localized with WXM • ~10 different XRB sources localized with SXC

  11. GRB Results From Two Years ofHETE-2 Operations • Classical GRBs: • 33 GRB localizations by WXM • 9 optical counterparts; 7 redshifts (so far) • 1 “short, hard” GRB localized (GRB 020531) • Current HETE-2 localization rate ~ 25 localizations yr- (14 in past 6 months) • ~250 FREGATE GRBs (120 coincident w. other S/C). • “X-ray Rich GRBs:” • 23 detected and 14 localized with log (S_x/S_gamma) > -0.5 • 7 are “X-ray flashes” (XRFs: Heise et al. 2002); i.e., log (S_x/S_gamma) > 0 • In other respects, they are similar to “classical GRBs”

  12. HETE-2 Mission Future • HETE-2 spacecraft and instruments are working well • Many real-time WXM GRB localizations have been sent out • Real-time SXC localizations will soon be possible • “Gating” (using spacecraft and ground software) now exits that will enable HETE-2 to provide real-time localizations of XRFs (this will be difficult for Swift) • HETE-2 orbit is high enough that operations can continue for > 10 years, if spacecraft and instruments continue to function (HETE-2 is currently funded through FY04)

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