Design and calibration of the grid-based energetic neutral atom imager (GENA) for the Queqiao-2 mission

The grid-based energetic neutral atom imager (GENA) onboard the Queqiao-2 satellite is designed to capture high spatiotemporal resolution data of the Earth’s ring current from a lunar orbit at a distance of 380000 km. The instrument operates based on the time-of-flight (TOF) method and the grid-based encoding modulation principle. Key specifications of GENA include the following: detection of H atoms with an energy range of 4–200 keV, detection of O atoms with an energy range of 8–250 keV, an energy resolution of better than 1 keV @ 10 keV, a field of view (FOV) of 19.72°×45.07°, an angular resolution of 0.43°, and a geometric factor of 19.2 cm² sr. This paper presents some ground calibration results obtained during the testing of the proposed imager. GENA is expected to perform energetic neutral atom imaging of the Earth’s magnetosphere and provide crucial data for studying particle injection from the magnetotail into the ring current region, as well as the generation and evolution of geomagnetic storms.