An absolute calibration system for millimeter-accuracy APOLLO measurements. (22nd November 2017)

• Record Type: Journal Article
• Authors: Adelberger, E G; Battat, J B R; Birkmeier, K J; Colmenares, N R; Davis, R; Hoyle, C D; Huang, L R; McMillan, R J; Murphy, T W; Schlerman, E; Skrobol, C; Stubbs, C W; Zach, A
• Is Part Of: Classical and quantum gravity. Volume 34:Number 24(2017:Dec.)
• Publication Date: 2017-11-22
• Subjects: lunar laser ranging -- experimental gravity -- calibration -- frequency standard -- SESAM laser; Quantum gravity -- Periodicals; Gravitation -- Periodicals; Relativity (Physics) -- Periodicals; Space and time -- Periodicals; Periodicals; 521.1
• DOI: 10.1088/1361-6382/aa953b
• Languages: English
• ISSNs: 0264-9381

Abstract

Abstract: Lunar laser ranging provides a number of leading experimental tests of gravitation—important in our quest to unify general relativity and the standard model of physics. The apache point observatory lunar laser-ranging operation (APOLLO) has for years achieved median range precision at the ̃2 mm level. Yet residuals in model-measurement comparisons are an order-of-magnitude larger, raising the question of whether the ranging data are not nearly as accurate as they are precise, or if the models are incomplete or ill-conditioned. This paper describes a new absolute calibration system (ACS) intended both as a tool for exposing and eliminating sources of systematic error, and also as a means to directly calibrate ranging data in situ . The system consists of a high-repetition-rate (80 MHz) laser emitting short ( < 10 ps) pulses that are locked to a cesium clock. In essence, the ACS delivers photons to the APOLLO detector at exquisitely well-defined time intervals as a 'truth' input against which APOLLO's timing performance may be judged and corrected. Preliminary analysis indicates no inaccuracies in APOLLO data beyond the ̃3 mm level, suggesting that historical APOLLO data are of high quality and motivating continued work on model capabilities. The ACS provides the means to deliver APOLLO data both accurate and precise below the 2 mm level.