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G. Nixon (Purdue, Harvard-Smithsonian CfA), J.D. Phillips, R.D. Reasenberg (Harvard-Smithsonian CfA)
The Principle of Equivalence Measurement (POEM), under development at the Smithsonian Astrophysical Observatory (SAO), is intended to test the Equivalence Principle of general relativity to an accuracy ten times better than previously achieved. POEM requires ultra-precise determination of two test masses' relative heights during free fall. The displacement of the test masses will be measured using an interferometric laser distance gauge, the Smithsonian's Tracking Frequency Gauge (TFG). The TFG was originally developed for the proposed POINTS mission in the early 1990's and is currently being modified for use in POEM.
We recently demonstrated the use of a new ``hopping" loop controller for the TFG. The hopping controller adds two features of interest to POEM---absolute distance measurements and the ability to track arbitrarily large changes in distance. Each of these features has been demonstrated with the new hopping controller, and components are being added to improve its functionality.
This work was funded by the National Science Foundation through the Research Experiences for Undergraduates (AST-9731923) program, and by the Smithsonian Astrophysical Observatory.
The author(s) of this abstract have provided an email address for comments about the abstract: gnixon1@purdue.edu