LAPEX (Large-Area Phoswich balloon Experiment for hard-X-ray astronomy)

The LAPEX detector is designed to perform spectral and temporal analysis of X-ray radiation emitted from X-ray sources in the 20-300 keV spectral range. The basic detection unit of the LAPEX experiment consists of a (145 x 145) mm phoswich detector.

A phoswich detector consists of a sandwich of a 6 mm thick NaI(Tl) crystal optically coupled
with a 50 mm thick CsI(Na) crystal. The phoswich is coupled to a photomultiplier tube that collects and amplifies the light pulses produced by the scintillation process in the crystal. In addition, an hexagonal tube rocking collimator with a field of view of 3 degrees (FWHM) is placed above the phoswich unit.

Sixteen of these basic units are assembled in groups of four, enclosed in a box of plastic
scintillator that acts as an active shield against charged particles.

The sources observed by the LAPEX detection unit during the 1995 flight were MKN463, NGC4151, MKN463, CYG X-3, CYG X-1, DENEB, and GROJ2057+43.

Balloon launched on: 10/6/1995 at 15:11 utc
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 SF3-459.37-080-NSXC-ST
Balloon serial number: W39.57-2-12
Flight identification number: 404N
End of flight (L for landing time, W for last contact, otherwise termination time): 10/7/1995 at 23:00 hs
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 14 h 30 m
Landing site: 22 miles ESE of Roswell, Nuevo Mexico, US
Payload weight: 2000 kgs

The balloon was launched at 15.00 UT (9.00 am local time).

Approximately three hours after launch, at 18.00 hrs (U.T.) the payload reached the float altitude of 125 kft (~40 km).

The whole flight duration from start to termination was approximately 14 hours with approximately 11 hours of flight at floating altitude.

Termination was at 5h 00m.

Landing occured at 5h 40m.

• LAPEX experiment: general description and pointing issues TESRE-CNR Internal Report (2001)
• NASA Balloon Flights (1989-1998) in NASA Historical Data Book, Vol. VII: NASA Launch Systems, Space Transportation, Human Spaceflight, and Space Science, 1989-1998