For TRACER (Transition Radiation Array for Cosmic Energetic Radiation)

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Launch site:Williams Field, McMurdo Base, Antarctica  
Launch team: National Scientific Balloon Facility (NSBF)
Balloon: Open balloon (zero pressure)
Volume: Raven W 39.570.000 cuft - (0.8 mil)
Serial number: -
Flight identification number: 526N
Campaign: - 
Payload weight: 3550 lbs
Gondola weight: -
Overall weight: 5966 lbs

The balloon was launched on December 12th at 6:09 UTC by dynamic method assited by launch vehicle. Following a nominal ascent phase, the balloon reached float altitude of 125.000 feet at 00:30 local time starting an anti-clockwise flight trajectory over the antarctic plateau.

After a few days of flight without incidents,on december 15th the balloon cross over the Vostok lake (considered the coldest place on earth) thus the balloon get cold and droped altitude to 120,000 ft. but continuing his travel until on December 20th it passed over the Ronne Ice Shelf. The more sunlight reflected off the ice warmed the balloon and thus it regained altitude to over 127,000 ft.

Fronm there, the travel continued without troubles until December 23th when the science team lose contact with TRACER instrument apparently due to the failure of the primary power system. This led to terminate the data taking phase of the flight.

On December 26th the balloon completed the full circle around the pole and passed within 80 miles of McMurdo Station at the same level flight of 127,000 ft. It appeared as a large white object in the sky remaining almost stalled for a period of hours over the Royal Society Mountains. Finally on December 27th the flight was terminated when the balloon was over Victoria Land on the East Antarctic Plateau. After separation, the instrument parachuted to earth but after landing the parachute failed to get dettached from it, so the wind inflated again the parachute's canopy resulting in the payload beeing dragged six miles across the snow. Finally the gondola stoped his drag within 100 miles of McMurdo Station.

A Twin Otter plane located the gondola on December 28th thanks to the 10 foot wide furrow in the snow. Although the incident the instrument itself was intact and was secured by the rescue team wich landed nearby and recovered the science data Hard Disks. The following days, bad weather conditions prevented the recovery of the rest of the payload wich lasted in the snow until January 2004 when the operation was completed and the instrument was shiped back to United States.  

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.