• DOI:10.1088/1361-6382/aa953b
• Corpus ID: 9249369

An absolute calibration system for millimeter-accuracy APOLLO measurements

@article{Adelberger2017AnAC,
  title={An absolute calibration system for millimeter-accuracy APOLLO measurements},
  author={Eric George Adelberger and James B. R. Battat and Konrad Birkmeier and N. R. Colmenares and R. Davis and C. D. Hoyle and L. R. Huang and R. J. Mcmillan and Thomas W. Murphy and Else Schlerman and Christoph Skrobol and Christopher W. Stubbs and Adolf Zach},
  journal={Classical and Quantum Gravity},
  year={2017},
  volume={34}
}

• E. Adelberger, J. Battat, +10 authors A. Zach
• Published 29 June 2017
• Physics
• Classical and Quantum Gravity

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.