The HETE-2 MissionD. Q. Lamb (U. Chicago)

Outline of This Talk

HETE-2 Mission Goals and ProgramHETE-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 OperationsSummary of First Two Years of HETE-2 MissionHETE-2 Mission Future

HETE-2 International Science Team

Cosmic Radiation Laboratory Institute of Physical and Chemical Research

(RIKEN)

JAPAN

Masaru Matsuoka Nobuyuki Kawai Atsumasa Yoshida

Centre D’Etude Spatiale des Rayonnements (CESR)

FRANCE

Jean-Luc Atteia Michel Boer Gilbert Vedrenne

Brazil + India + Italy

(Burst Alert Station Scientists)

Joao Braga

Ravi Manchanda

Graziella Pizzichini

Los Alamos National Laboratory

Los Alamos, NM USA

Edward E. FenimoreMark Galassi

Space Science Laboratory

University of California at Berkeley, CA USA

Kevin Hurley J. Garrett Jernigan

Astronomy and Astrophysics Department University of Chicago, IL USA

Donald Q. Lamb Jr.

Carlo GrazianiTim Donaghy

Board of Astronomy and Astrophysics University of California at Santa Cruz, CA

USA

Stanford E. Woosley

Thomas L.Cline (NASA Project Scientist)

Goddard Space Flight Center Greenbelt, MD

USA

Center for Space Research Massachusetts Institute of Technology

Cambridge, MA USA

George R. Ricker (PI)Geoffrey B. Crew John P. Doty

Alan M. Levine Roland K. VanderspekJoel Villasenor

(Mission Scientist)

High Energy Transient Explorer

HETE~ 1st Dedicated -Ray Burst Satellite ~

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)

Mission Goals And Program

HETE During Ground Testing

Science Instrument Package

Soft X-ray Cameras (SXC): 2-10 keV; ~40” localizations

Wide-Field X-ray Monitor (WXM): 2-25 keV; ~5’-10’ localizations

French Gamma-ray Telescope (FREGATE): 5-400 keV; ~π FOV

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.

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.

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/

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

Non-GRB Results from Two Years of HETE-2 Non-GRB Results from Two Years of HETE-2 OperationsOperations

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).

GRB Results From Two Years ofHETE-2 Operations

“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) > 0In other respects, they are similar to “classical GRBs”

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)