Developed by the Delaware University in the early 90's is an instrument which measures the energy spectrum of comic ray electrons using mainly a permanent magnet and a spark chamber hodoscope to determine the charge sign of the electron.
As we can see in the scheme (click to enlarge) AESOP chambers contain 5 parallel aluminum plates connected, in alternate order, to ground and a high voltage pulser. The medium between plates is a slow moving noble gas mixture of neon and helium. As a charged particle transverses a chamber it leaves behind an ion trail in the gas. If the scintillator detectors, mounted above and below the chamber, detect coincidence light pulses from the resulting ionization track, a 10,000 volt pulser is triggered. In the presence of a high electric field, the ions in the gas are accelerated toward the plate surface producing more ions with each ion-atom collision. These multiple collisions form an ion cascade which ultimately results in a high voltage breakdown very near the original ion trail. This breakdown in each gap produces a bright red verticle spark which is digitized and recorded using a linear CCD camera.
The instrument was flown several times in a same gondola with another complementary instrument called LEE (Low Energy Electrons).
Balloon launched on: 6/6/2009 at 22:18
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 mil)
Flight identification number: 595N
End of flight (L for landing time, W for last contact, otherwise termination time): 6/10/2009 at 15:15
Balloon flight duration (F: time at float only, otherwise total flight time in d:days / h:hours or m:minutes - ): 3 d 17 h
Landing site: In the south of Ellesmere Island, Canada
The balloon was launched by dynamic method with assistance from launch vehicle (Hercules) on June 6th at 22:05 UTC. At launch part of the frame holding the solar panels struck the launch vehicle and was damaged, but besides that and after a nominal ascent phase, the balloon reached float altitude on June 7th at 1:10 UTC without troubles, starting a westward path as can be seen in the map at right (click to enlarge).
The crossing of the Atlantic Ocean took 3 days and 17 hours. The payload was separated from the balloon the southwestern part of the Ellesmere Island in Canada.
The rescue operation was acomplished by a team of the Columbia Scientific Balloon Facility deployed to Yellowknife a few days before the start of the Sweden campaign.
According to NASA sources the instrument performed very well during the entire trip.
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