Name: Jana Dee Strasburg
Email: jdstras@u.washington.edu
Affiliation: University of Washington, Dept. of Physics (grad)


Title:
Constraining the Weight of Gravity:  A Test of the Strong Equivalence
Principle using Lunar Laser-Ranging


Abstract:
The University of Washington has recently embarked on a Lunar Laser-Ranging
campagin aimed at measuring the earth-moon separation with millimeter
precision.  This will be the strongest test to date of the Strong Equivalence
Principle and other fundamental gravitational questions.  The Apache Point
Observatory Lunar Laser-Ranging Operation (APOLLO) will employ the 3.5 meter
telescope at the Apache Point Observatory in southern New Mexico.  This
instrument will result in the detection of several return photons per
outgoing laser pulse, a dramatic improvement over current signal rates.  This
improved signal rate will yield a better understanding of the systematic
errors involved as well as allow for operation during high-background
conditions such as the full moon and twilight.  In order to deal with the
high signal rate, an array of avalanche photodiodes will oversample the
return spot and time-tag each return photon.  A precision gravimeter will
also be placed at the site to measure the vertical crustal deformation due to
geophysical effect including solid earth tides and ocean, atmospheric and
ground water loading.  These measurements will be used to constrain the
modeling that will ultimately produce the final result.