For TRACER (Transition Radiation Array for Cosmic Energetic Radiation)

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Launch site:Fort Sumner Municipal Airport, New Mexico, US  
Launch team: National Scientific Balloon Facility (NSBF)
Balloon: Open balloon (zero pressure)
Volume: 800.000 m3
Serial number: W 39.57-3X-19
Flight identification number: 471N
Campaign: - 
Payload weight: 4042 lbs
Gondola weight: -
Overall weight: 12328 lbs

The launch (by dynamic method using launch vehicle) was complished at 16:36 utc. on September 20th.

After a nominal ascent phase at an average speed of 833 fpm, the balloon achieved float altitude of 121.000 feet, and then started a flight path heading east (click in the map at left to see the balloon flight path).

At the middle of the flight the balloon course changed slightly to the southeast and fliyng over west Texas. Then the final course was due west entering again to New Mexico by the south.

Finally, after near 32 hours of flight, the balloon was terminated when the cutdown command was sent.

The payload touched ground 13 nm Northwest of Artesia NM, without damage, being recovered by the NSBF team on september 23th.  

TRACER (Transition Radiation Array for Cosmic Energetic Radiation)

Responsable institution:  University of Chicago
Principal Investigator:  Prof. Dietrich Müller

An instrument created to make direct measurements of heavy cosmic ray nuclei (oxygen to iron) in the energy range of several eV. It measures the nuclear charge, the energy, and the trajectory of the cosmic ray particles through the instrument. For charge measurements, two layers of plastic scintillators (2 x 2 m2), and one Cerenkov counter (2 x 2 m2) are used. The two scintillators are placed on top and bottom of the detector stack acting as instrument trigger, and the Cerenkov counter made of acrylic plastic located at the bottom of the detector is used to reject non-relativistic particles. At left can be seen an sketch of the several layers that compose the instrument (click to enlarge).

For the energy measurement it uses a transition radiation detector system which determines the Lorentz factor. This approach permits the construction of large-area detectors without requiring an exorbitant detector mass.

To determine the trajectory of the incoming particles TRACER have eight double layers of proportional tubes which are oriented alternately in two orthogonal directions to permit corrections in the data pathlength variations.