The Upper Atmosphere Monitoring Program (nicknamed Project Ashcan because of the classical shape of the first sampling unit used) was initiated in 1956 as an answer for the pressing need for information concerning the nature, concentration and distribution of radioactive debris injected into the stratosphere during nuclear weapons tests. The main instrument of the project was an impactor collector that was carried out by a stratospheric balloon to obtain samples at preset altitudes between 50.000 and 90.000 feet.
General Mills engineers designed the first "Ashcan" filter sampler (left) which was flown operationally from November 1956 until December, 1959. This sampler utilized a Torrington 403 blower to pull air through five square feet of low background, low pressure drop filter paper. Sampling rate depended upon altitude and voltage applied, but averaged between 500 and 600 cubic feet per minute. After discovery in the laboratory of some inconsistencies in the volumes measured, in later models of this instrument were incorporated 40-foot exhaust ducts to prevent re-entrainment of sampled air. Also in later years the collector unit was modified and improved many times.
ASHCAN program was run in a monthly basis, with regular flights from Alaska, Australia, Brazil, Panama, and in several sites of the United States. Also special missions were performed to analize certain events like the debris left by the reentry of soviet satellites carrying small nuclear reactors, or after volcanic eruptions. The program was terminated in 1983.
Balloon launched on: 3/27/1959
Launch site: Sioux City Airport, Iowa, US
Balloon launched by: 1110th Balloon Activities Squadron, USAF
Balloon manufacturer/size/composition: Zero Pressure Balloon
Flight identification number: I-51
There was a controversy with regard to the date of this flight: in the publications of the US Atomic Energy Comission (HASL-84 & HASL-69 among others) it was apparently launched on March 30, however after checking the sample number with the ASHCAN database, it was found that the correct date was March 27. This fact was reflected in later publications like HASL-115.
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