A simple thermal imaging trick could let gravitational-wave detectors spot cosmic collisions from twice as far away.
By Science Blog Editorial Team · Edited by Justin Brown
Published · How we edit
University of California, Riverside physicists have developed a thermal-imaging method that could help the LIGO A+ gravitational-wave detectors operate closer to their intended sensitivity. In simulations reported in a paper published in Classical and Quantum Gravity, the method improved strain sensitivity by as much as 31% at the frequencies where laser shot noise has the greatest effect and increased the average binary neutron star detection range by about 10 megaparsecs, or 33 million light-years.
The proposed system uses commercially available infrared cameras positioned outside the detector’s vacuum chambers. By combining surface-temperature maps with a computer model of heat flow through each mirror, the researchers say LIGO could identify and correct optical distortions that existing sensors cannot fully measure. The gain remains a modeled projection rather than an improvement already demonstrated in an operating LIGO instrument.
LIGO detects gravitational waves by sending laser light through two perpendicular, 4-kilometer arms and measuring extraordinarily small changes in their relative lengths. Increasing the amount of circulating laser power can reduce photon shot noise, but it also increases the heat absorbed by the mirrors.
The mirrors reflect almost all the light that reaches them, yet even tiny absorption can change their surface shape by a few nanometers. Those distortions alter the laser wavefront and can prevent the detector from receiving the full benefit of higher power and stronger quantum squeezing. The challenge is not only correcting the distortion, but measuring it across the mirror’s full usable aperture.
LIGO already uses thermal compensation equipment and wavefront sensors, while researchers are also developing new mirror coatings and adaptive optics. Earlier UC Riverside work described a front-surface heating system designed to reshape LIGO mirrors, but a correction system needs a reliable signal showing how much heat to apply and where.
The new method begins with an infrared image of a mirror’s reflective surface. A finite-element model then separates the measured temperature pattern into contributions from the main laser beam and from two thermal actuators: LIGO’s ring heater and a proposed front-surface heating device known as FROSTI.
From that map, the algorithm estimates the absorbed laser power, the beam’s position on the mirror, and the power delivered by each actuator. The reconstructed thermal state can then be converted into a map of the optical distortion caused by surface deformation and changes in the glass’s refractive properties.
The study tested the method with simulated thermal images and realistic camera limits. The authors found that a commercial camera with a roughly 600-by-600-pixel sensor and temperature resolution of about 20 millikelvin could locate the beam to within 0.5 millimeters and estimate the relevant heating powers to within about 0.1% under the modeled conditions.
The calculation can run on millisecond timescales, much faster than the minutes-to-hours timescale over which the mirrors heat and cool. However, the model assumes a thermally steady mirror, largely uniform coating absorption, and no major central point absorbers. Those assumptions will have to be tested during instrument commissioning.
The headline number is a maximum improvement in strain sensitivity, not a 31% increase in LIGO’s average detection distance. The simulations found their largest effect at high frequencies, where quantum shot noise dominates, while the integrated gain for binary neutron star signals corresponded to an average range increase of about 10 megaparsecs.
That distinction matters because the draft’s earlier volume claim treated the 31% peak sensitivity figure as though it applied directly to distance. The paper does not report that the technique would double LIGO A+’s total survey volume. It reports a specific gain in binary neutron star range, and the resulting increase in accessible volume depends on the detector’s starting range and full sensitivity curve.
Even a smaller range gain can still produce more detections because the amount of space within reach grows with the cube of distance. A larger event sample would improve population studies of neutron stars and black holes, building on a gravitational-wave catalog that already more than doubled the previous detection count.
The proposed cameras would sit outside LIGO’s vacuum system, avoiding the need to place new imaging hardware beside the suspended mirrors. The researchers also modeled specifications available in commercial thermal cameras, which could reduce the amount of custom hardware development required.
That does not make implementation automatic. A working system would still need calibrated relay optics, a stable view of each mirror, integration with LIGO’s controls, and testing under real interferometer conditions. The study establishes a plausible sensing method and quantifies its potential benefit, but it does not show a completed detector upgrade.
The paper was written by Liu Tao, Pooyan Goodarzi and Jonathan W. Richardson of UC Riverside. Richardson, an associate professor of physics and astronomy, led the work, while Tao was a postdoctoral researcher in his laboratory and Goodarzi is a doctoral student. The National Science Foundation supported the research.
The same sensing problem becomes more important as gravitational-wave observatories move toward higher laser powers. LIGO A+ and the later A# concept are intended to develop technologies that could feed into Cosmic Explorer, a proposed U.S. observatory with arms as long as 40 kilometers.
Cosmic Explorer aims for an order-of-magnitude sensitivity improvement over current instruments. Its design would use higher optical power and much larger mirrors, making precise thermal-state measurements essential if wavefront errors are not to erase gains from quantum-noise reduction.
UC Riverside says the thermal-imaging approach is expected to form part of Cosmic Explorer’s baseline design, with Richardson serving as system design lead for mode sensing and control. LIGO would therefore act as the test bed where the cameras, models and control signals can be validated before they are scaled to a next-generation detector.
The immediate next step is experimental validation during future LIGO upgrades. As the UC Riverside announcement makes clear, the attraction is not that a camera alone makes LIGO 31% better, but that accurate thermal measurements could allow existing and planned correction hardware to perform much closer to its design limits.
Standards
Articles on Science Blog are produced with AI assistance and reviewed by editorial staff before publication. See our editorial standards and masthead.
Written by
Articles published under the Science Blog byline are produced and reviewed by our editorial team before publication. See our editorial policy for our review process and standards.
Clear science for curious people
A Brown Brothers Media publication. All rights reserved © 2026.
Clear science for curious people — free PDF, then our science email.
Also available via RSS.