Purpose of the flight and payload description

LEE is an instrument which measures the energy spectrum of comic ray electrons. In the picture at left we can see a scheme of it (click to enlarge). It detects incoming electrons with 3 plastic scintillators (T1, T3 and G in the drawing) the last one for anticoincidence and a gas Cherenkov detector (T2). It measures the electron energy in a cesium iodide (T4) and leadglass (T5) calorimeter. Another Scintillator (T6) also assists in particle identification and energy determination by counting the number of particles that escape the calorimeter.

The LEE instrument was developed in the late 60's at the University of Chicago and made his first flight in 1968. Over the years, regular ballon flights have been made from Northern Canada yearly during the years 1968 to 1975 and approximately bi-annually until 1979. Then, the experiment was transfered to the University of Delaware, wich now operates it.

The observations from LEE provide one of the few more precise measurements of the electron spectrum over an extended period of time.

Video footage of the launch

Details of the balloon flight

Balloon launched on: 5/17/2009 at 2:26
Launch site: European Space Range, Kiruna, Sweden  
Balloon launched by: Columbia Scientific Balloon Facility (CSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Winzen 39.570.000 cuft (0.8 Mils) 1 Cap (0.8 mils)
Balloon serial number: Winzen 39.57-2-66
Flight identification number: 593N
End of flight (L for landing time, W for last contact, otherwise termination time): 5/21/2009 at 12:29
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): ~ 4 d
Landing site: On Devon Island, North of Canada
Payload weight: 600 kgs

The balloon was launched by dynamic method at 2:26 utc on May 17th under near perfect meteorological conditions, and after an initial ascent phase it reached a height of 43.5 km wich according sources from the Swedish Space Corporation was a record with such a heavy payload (about 600 kg of the payload and the entire flight train).

Once at float altitude the balloon started a westward flight path crossing over Sweden and Norway and then entering in the Atlantic Ocean at a stabilized flight height of 41 km.

The mission endured 4 days, 10 hours, and 56 minutes until termination which ocurred at 12:29 utc on May 21. The termination and parachute cutaway were successfully performed using MIP/Iridium procedures, as adverse cloud cover in the termination area prevented use of the chase aircraft. The payload landed in Devon Island in the north of Canada and was recovered days later in its entirety with a single Twin Otter trip to the impact site.

The science group reported excellent data collection throughout the flight. The primary science objective of the flight was to make a definitive determination of the cosmic electron energy spectrum from below 50 to above 5GeV during a Solar Minimum A-magnetic polarity to compare the previous determinations. The results would also provide an important cross-calibration reference for measurements obtained from orbit by the PAMELA instrument launched in June 2006.

External references

Images of the mission

Close view of the gondola before launch (Courtesy: CSBF) View of the inflation of the balloon (Courtesy: CSBF) The balloon at release time (Courtesy: CSBF) Initial ascent phase (Courtesy: CSBF) Impressive image of the LEE balloon fully expanded while flying at 41 km  (Courtesy: CSBF)

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