We have designed and realized a compact portable laser system for high-sensitivity mobile cold atom interferometers. The laser system is mounted on a single module with dimensions of $45\mathrm{cm}\times 45\mathrm{cm}\times 16\mathrm{cm}$ and emits lights directly on up to 13 fiber ports for a two-dimensional magneto-optical trap, atom fountain, Raman transition, and normalized detection. A double-sided optical structure and mounts without kinematic adjustment are designed to achieve high-level integration and stability. The laser system is applied to a mobile atom gravimeter and achieves a sensitivity of $28\mathrm{\mu Gal}/{\mathrm{Hz}}^{1/2}$. Experiencing 1200-km-long truck transportation, the laser system could be restored to good operating status without internal realignment.

We present a compact high-resolution absolute-gravity gradiometer based on dual ${}^{85}$$\mathrm{Rb}$ atom interferometers using stimulated Raman transitions. A baseline of $L=44.5$ cm and an interrogation time of $T=130$ ms are realized in a sensor head with a volume of only 95 l. Many experimental parameters are optimized to improve the short-term sensitivity, whereas interleaving measurements by reversing the direction of the Raman wave vector are implemented to improve the long-term stability. After an averaging time of 17 000 s, a phase resolution of $104\mu \mathrm{rad}$ is achieved, which corresponds to a gravity-gradient resolution of 0.86 E (1 E = $1\times {10}^{-9}$/${\mathrm{s}}^2$). After the evaluation and correction of systematic errors induced by light shift, the residual Zeeman shift, the Coriolis effect, the self-attraction effect, etc., the instrument serves as an absolute-gravity gradiometer and with it the local gravity gradient is measured to be 3114 (53) E. This instrument combines the merits of high-resolution, high-compactness and high-accuracy, and has good application prospects in many fields.

Gravity measurements have important applications in geophysics, resource exploration, geodesy, and inertial navigation. The range of classical gravimetry includes laser interferometer (LI)-based absolute gravimeters, spring relative gravimeters, superconducting gravimeters, airborne/marine gravimeters, micro-electromechanical-system (MEMS) gravimeters, as well as gravity satellites and satellite altimetry. Atomic gravimetry is a new absolute gravity measurement technology based on atom interferometers (AIs) and features zero drift, long-term stability, long-term continuous measurements, and high precision. Atomic gravimetry has been used to measure static, marine, and airborne gravity; gravity gradient; as well as acceleration to test the weak equivalence principle at the China Space Station. In this paper, classical gravimetry is introduced, and the research progress on static and airborne/marine atomic gravimeters, space AIs, and atomic gravity gradiometers is reviewed. In addition, classical and atomic gravimetry are compared. Future atomic gravimetry development trends are also discussed with the aim of jointly promoting the further development of gravity measurement technologies alongside classical gravimetry.

The precision of the weak equivalence principle (WEP) test using atom interferometers (AIs) is expected to be extremely high in microgravity environment. The microgravity scientific laboratory cabinet (MSLC) in the China Space Station (CSS) can provide a higher-level microgravity than the CSS itself, which provides a good experimental environment for scientific experiments that require high microgravity. We designed and realized a payload of a dual-species cold rubidium atom interferometer. The payload is highly integrated and has a size of $$460\,{\rm{mm}}\times 330\,{\rm{mm}}\times 260\,{\rm{mm}}$$460 mm × 330 mm × 260 mm . It will be installed in the MSLC to carry out high-precision WEP test experiment. In this article, we introduce the constraints and guidelines of the payload design, the compositions and functions of the scientific payload, the expected test precision in space, and some results of the ground test experiments.

The location-dependent Raman transition was investigated based on dual atom interferometers which were designed for gravity-gradient measurements. The cross talk between the Raman beam pairs generated by an electro-optical modulator make the Raman transition location dependent. Therefore, the fringe contrast also depends on the location where the Raman pulses interact with the atoms, so it is important to adjust the interaction location to optimize the precision of the gravity-gradient measurements. To further reduce the residual cross talk, the detuning of the Raman beams for ${}^{85}\mathrm{Rb}$ atoms was controlled using the saturated absorption spectra of the ${}^{87}\mathrm{Rb}$ atoms. The optimal location for the Raman transition was determined by theoretical analysis and modulation experiments, and the atomic trajectory was optimized and applied to the gravity-gradient measurements. The resolution of the differential gravity measurement evaluated by the Allan deviation was $4.9\times {10}^{-9}$ m/${\mathrm{s}}^2$ @ 15 000 s, and the corresponding resolution of the gravity gradient measurement was 7.4 E @ 15 000 s.

A dynamic gravimeter with an atomic interferometer (AI) can perform absolute gravity measurements with high precision. AI-based dynamic gravity measurement is a type of joint measurement that uses an AI sensor and a classical accelerometer. The coupling of the two sensors may degrade the measurement precision. In this study, we analyzed the cross-coupling effect and introduced a recovery vector to suppress this effect. We improved the phase noise of the interference fringe by a factor of 1.9 by performing marine gravity measurements using an AI-based gravimeter and optimizing the recovery vector. Marine gravity measurements were performed, and high gravity measurement precision was achieved. The external and inner coincidence accuracies of the gravity measurement were ±0.42 mGal and ±0.46 mGal after optimizing the cross-coupling effect, which was improved by factors of 4.18 and 4.21 compared to the cases without optimization.