Description of the payload

LXeGRIT is a balloon-borne Compton telescope employing a large volume liquid xenon time projection chamber (LXeTPC) as the central gamma-ray detector. It is designed to image gamma rays in the energy range of 200 keV to 20 MeV, with an angular resolution of about 3 degrees (1 sigma) at 2 MeV, within a field-of-view (FOV) of about 1 sr.

Details of the balloon flight and scientific outcome

Launch site: Scientific Flight Balloon Facility, Fort Sumner, (NM), US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon 800.000 m3 - SF3-29.47-.8/.8/.8NHR
Balloon serial number: W29.47-2X-35
Flight identification number: 491N

After difficult low-level wind conditions had postponed the flight several times, the NSBF team managed to find a slim launch window, during which the payload was smoothly put afloat. The balloon was released at 19:39 utc on October 4th, 2000, which was an unusual early-afternoon launch in NASA balloon base of Ft. Sumner. The balloon went straight up, heading East initially, but soon changing to a south-western and eventually western course. Due to the western course of the balloon, which is very unusual for a flight in early October, the science team was flown from Ft. Sumner to the downlink station in Holbrook, AZ, in the morning of October 5. The gondola landed softly about one hour west of Phoenix, Arizona, near a small town called Buckeye. The payload just tipped over without being dragged, thus producing only minor dammage to the gondola.

The long flight time, the perfect operation of all systems, and the wide field-of-view of the Compton telescope LXeGRIT, which was flown this time without any shields, allowed the science team to obtain data on all MeV gamma-ray sources within ~45 deg zenith angle. The main focus was imaging of the Crab nebula, but other strong sources such as 3C273 or Cygnus X-1 have also been in the field-of-view. During the flight were collected a total of almost 40 GB of event data, of which about 80% have been stored onboard, and the rest downlinked through two 500 kbps telemetry channels.

External references and bibliographical sources

Images of the mission

LXEGRIT Launch The balloon climbing up Balloon at float - Image obtained trough a telescope by an amateur astronomer near Tucson - Copyright Sam Rua Jr.