Technology for Precision Gravity Measurements

Abstract

We discuss four technologies applicable to precision measurements inspace and on the ground. The first is our tracking frequency laserdistance gauge (TFG), which we developed ca. 1990 for a spaceborneastrometric optical interferometer, POINTS, and which we are using todayfor our principle of equivalence measurement (POEM), a laboratory testof the equivalence principle. The second is an extension of the TFG touse a semiconductor laser (SL-TFG) with the intention to make theinstrument more robust and applicable to space-based experiments. Inparticular, we wish to apply the SL-TFG to a version of POEM that couldoperate in space at substantially higher accuracy. Further, someversions of the SL-TFG have reduced complexity and thus have enhancedreliability and reduced cost. The third technology is an approach tousing the TFG as part of an extended spacebased optical instrument. Wediscuss the launching of multiple beams from a single device as a meansof achieving a {\ldquo}strong optical truss{\rdquo} without excesscomplexity or endpoint connection error. The fourth and final technologyis for creating a brief period of free fall in the laboratory, and beingable to repeat the free-fall rapidly. This technology is a key part ofPOEM.