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The Lambda-Point Experiment (LPE) flew on the USMP-1 (U.S. Microgravity Payload) mission on Space Shuttle Columbia. The launch occurred on October 22, 1992. The goal of the experiment was to measure the singularity in the specific heat of helium around the lambda transition at 2.177 K, with nano-Kelvin resolution. The instrument was developed by Professor J. Lipa and his team at Stanford University. The flight instrument was built under a contract to Ball Aerospace in Colorado. The Jet Propulsion Laboratory (JPL) provided the cryostat facility and overall management of the experiment. The cryogenic system, functions, and performance are described in detail below. Before flight, over 100 cryo-servicing operations, covering a 20-month period from the first cool-down, were performed. The cryostat’s performance in space exceeded expectations, primarily because of the low outside-shell temperature. The temperature stability of the cryostat was maintained by passive control with a liquid/vapor phase separator. |
