Date

2017

Department or Program

Physics

Primary Wellesley Thesis Advisor

James Battat

Abstract

Capable of testing Einstein’s theory of General Relativity, Lunar Laser Ranging measures the orbit of the Moon around the Earth by pulsing laser light from a telescope on Earth to five passive lunar reflectors placed on the Moon by Apollo astronauts and Russian rovers. One such operation, APOLLO (the Apache Point Observatory Lunar Laser-ranging Operation) has achieved millimeter precision measurements of the Earth-Moon distance, allowing for 10 times more stringent constraints of gravitational parameters. Until recently, however, there was no way to assess the measurement ac- curacy. In order to test gravitational models with greater accuracy, APOLLO implemented the Absolute Calibration System (ACS), an internal calibration laser, which pulses light at a frequency stable at the part per trillion level. My thesis research centered around making improvements to one component of the ACS, the Laser Slicer Board (LSB), which acts as a very fast ON/OFF gate for light from the ACS calibration laser. In preparation for this work, I redesigned the Opto-isolation and Tiltmeter Board (opto-tilt board) for APOLLO, replacing a previous opto-isolation board that had not been electrically functioning and combining it with an accelerometer-based tiltmeter to conserve space. After developing the schematic and layout of this board, I populated, tested, and installed the board at Apache Point Observatory in January 2017. As a theoretical exercise, I also took advantage of the time measurements from APOLLO’s two clocks – one GPS-disciplined to behave as if it were at sea level and the other counting time at an altitude of 2.8 km – to explore the phenomena of Gravitational Redshift and its effects on measuring time.

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