Dual-wavelength extreme ultraviolet camera (EUC) for the Chang’E-7 mission: Scientific objectives and system design

The dual-wavelength extreme ultraviolet camera (EUC) onboard the Queqiao-2 relay satellite of the Chang’E-7 (CE-7) mission will be used to investigate the global structure and dynamics of the Earth’s magnetosheath and plasmasphere by simultaneously capturing emissions at 30.4 and 83.4 nm. In geospace, there are two emission sources at 30.4 nm: resonantly scattered emissions from plasmaspheric He+ions and solar wind charge-exchange in the Earth’s magnetosheath. The sources of 83.4 nm emission include the ionospheric outflow O+and the plasmaspheric O+ions, both of which resonantly scatter sunlight at this wavelength. Global images at these wavelengths will enhance understanding of mass and energy transportation in solar wind-magnetosphere-ionosphere couplings, crucial for comprehending space weather. The Moon is an ideal platform for global imaging, allowing the EUC’s two optical heads operating at 30.4 and 83.4 nm, each with a circular field of view of 20° to capture spatial resolution of ∼0.1REfor the plasmasphere, ∼0.3REfor the magnetosheath, and ∼0.3REfor the ionospheric outflow in the meridian plane perpendicular to the Earth-Moon line. The sensitivities are as follows: 0.1 counts s−1Rayleigh−1at 30.4 nm channel for an angular resolution of 0.1° and 0.07 counts s−1Rayleigh−1at 83.4 nm channel for an angular resolution of 0.3°. Sufficient sensitivity was achieved to obtain plasmaspheric images every 10 min, magnetosheath images every 10–20 min, and ionospheric outflow images every 10 min. All of the original photon signals are transmitted to the ground, allowing for flexible processing of spatial and temporal resolutions.