CHES will use high-precision relative astrometry technology in space to accurately measure the micro angular second level interplanetary distance changes of the target star's center position relative to 6-8 standard reference stars. Through these subtle changes, the displacement of the target star caused by planetary gravitational disturbance will be calculated, and the number, true mass, and three-dimensional orbit of habitable planets will be explored in detail.

The astrometry amplitude α caused by the planet around the target star can be expressed as：

The principle of relative astrometric measurement.

Target Stars :

The CHES project has preliminarily completed the selection of 100 F, G and K types of nearby stars as primary targets of the space mission with all stars located in 10 pc from the Earth.

                                              Distribution of CHES target stars within ∼10 pc.

Examples of the F, G and K Target stars and Number of Reference Stars.

6-8 reference stars are required for observation within the field of view, with reference stars brighter than 13.  

An example of the target star α Cen A with its reference stars.

Simulations of astrometric detection of two types of terrestrial planets.