A Tale of Two Calibrators: Comparing Newtonian and Photon Calibration in Advanced LIGO after the Third Observing Run
Abstract
Precise calibration of LIGO's strain readout plays a vital role in our ability to extract information from gravitational-wave detections. We present a comparative analysis of two independent direct-force calibration methods: the Newtonian Calibrator (NCal) and Photon Calibrator (PCal) systems. Currently, LIGO relies solely on the PCal system as its absolute calibration reference. To facilitate comparison, a series of direct-force injections were performed using the NCal and PCal systems at the LIGO Hanford observatory just after the completion of the third observing run. We compute the ratio of the measured to expected strain amplitudes for every injection. For each injection frequency across a 30 Hz band, the ratios of NCal and PCal differ by ∼0.5-1%, demonstrating a small systematic difference between the two systems. This offset highlights the importance of maintaining multiple independent calibration references to validate LIGO's calibration.
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BibTeX
@misc{jones2026tale,
title = {{A Tale of Two Calibrators: Comparing Newtonian and Photon Calibration in Advanced LIGO after the Third Observing Run}},
author = {Dana Jones and Michael P. Ross and Ling Sun and Jeffrey S. Kissel and Dripta Bhattacharjee and Anthony Sanchez and Bram J. J. Slagmolen and Jens Gundlach},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.01917},
eprint = {2609.01917},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.01917},
}
RIS
TY - UNPB
TI - A Tale of Two Calibrators: Comparing Newtonian and Photon Calibration in Advanced LIGO after the Third Observing Run
AU - Dana Jones
AU - Michael P. Ross
AU - Ling Sun
AU - Jeffrey S. Kissel
AU - Dripta Bhattacharjee
AU - Anthony Sanchez
AU - Bram J. J. Slagmolen
AU - Jens Gundlach
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.01917
UR - https://arxiv.org/abs/2609.01917
AB - Precise calibration of LIGO's strain readout plays a vital role in our ability to extract information from gravitational-wave detections. We present a comparative analysis of two independent direct-force calibration methods: the Newtonian Calibrator (NCal) and Photon Calibrator (PCal) systems. Currently, LIGO relies solely on the PCal system as its absolute calibration reference. To facilitate comparison, a series of direct-force injections were performed using the NCal and PCal systems at the LIGO Hanford observatory just after the completion of the third observing run. We compute the ratio of the measured to expected strain amplitudes for every injection. For each injection frequency across a 30 Hz band, the ratios of NCal and PCal differ by ∼0.5-1%, demonstrating a small systematic difference between the two systems. This offset highlights the importance of maintaining multiple independent calibration references to validate LIGO's calibration.
ER -