A Chinese research team has demonstrated that a self-developed, transportable cold atom gravimeter can measure Earth’s gravitational pull with accuracy matching the world’s leading laser-interferometer instruments. During a two-month comparison organized by China’s Crustal Movement Observation Network (CMONOC) in Wuhan, the atom-based instrument, WAG-H5-2#2508, was tested alongside eight conventional absolute gravimeters. Its result differed from the group consensus value by only 1.4 microGal — approximately one billionth of surface gravity — confirming that wear-free atom interferometry is ready for high-precision, long-term gravity monitoring.

Absolute gravimeters measure local gravitational strength with extreme precision, supporting geodesy, resource exploration, earthquake studies, and gravity reference networks. Laser-interferometer instruments like the FG5X and A10 have dominated the field for decades by tracking falling objects as light bounces off them. These devices are reliable but experience mechanical wear over time, limiting unattended continuous monitoring.

Cold atom gravimeters offer an alternative approach. Rather than dropping a physical test mass, they launch laser-cooled rubidium atoms upward in a vacuum chamber and track quantum wave interference as atoms fall under gravity. Without mechanical free-fall mechanisms, these instruments experience no wear and can operate unattended for extended periods.

Putting the New Instrument to the Test

The research team at CAS Cold Atom Technology (Wuhan) Co., Ltd. developed the second-generation transportable atom gravimeter, WAG-H5-2. The instrument features highly integrated modular design with dimensions of 0.50 m × 0.23 m × 1.34 m, integrating active vibration isolation and magnetic shielding, while optical and electronic subsystems are configured as four modular 3U chassis. The prototype WAG-H5-2#2508 participated in the 2026 CMONOC Absolute Gravimeter Comparison held in Wuhan from January to March 2026, evaluated alongside five FG5X laser interferometer gravimeters, two A10 laser gravimeters, and one IGG-03B laser absolute gravimeter.

Over two measurement campaigns, nine instruments occupied five gravity sites at two geodetic observatories on Jiufeng Mountain. A superconducting gravimeter monitored gravity changes at one site around the clock, allowing measurements taken at different times to be corrected to a common reference epoch. Two relative gravimeters precisely mapped how gravity changes with height at each site, enabling every instrument’s reading to be transferred to a common reference height for fair comparison.

Results showed that all nine instruments agreed with comparison reference values within their stated uncertainties, with individual deviations ranging from -4.3 to 6.1 microGal. The WAG-H5-2#2508 showed a deviation of just 1.4 microGal, closely matching the roughly 3 microGal accuracy specified by its manufacturer.

Beyond the comparison, the team separately evaluated short-term sensitivity, precision, repeatability, and long-term stability. The gravimeter reached short-term sensitivity of 16.2 microGal per square-root-hertz, close to established laser gravimeters, and achieved measurement precision better than 1.0 microGal after 1000 seconds of averaging. Repeated day-long measurements after restarting agreed within 1.5 microGal, and after transportation over 1,125 kilometers from Wuhan to Tianjin, the instrument tracked half a month of continuous tidal gravity variation with residual scatter less than 10 microGal.

The authors note that because atom gravimeters do not require scale-factor calibration needed by relative, spring-based instruments and do not suffer mechanical wear of drop-based laser gravimeters, they are well suited to calibrating other gravity sensors and supporting continuous, long-term absolute gravity monitoring in the field. The team suggests that combining atom gravimeters, superconducting gravimeters, and relative gravimeters into an integrated hybrid observation network — an approach called “3G hybrid gravimetry” — represents a promising direction for future gravity reference systems.

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Journal: Earth and Planetary Physics
DOI: 10.26464/epp2026058
Article Title: Performance evaluation of the cold atom gravimeter WAG-H5-2#2508
Publication Date: 1-Jul-2026