EnVisS: a full-sky camera for the Comet Interceptor ESA mission

Comet Interceptor is the first Fast mission of the European Space Agency (ESA); it has been selected in June 2019 and is conceived to study a long-period comet, or an interstellar object. On the B2 Comet Interceptor spinning probe, that will venture very near to the comet, the Entire visible Sky (EnVisS) camera will be mounted. EnVisS is being designed for mapping and studying the coma of the selected mission target via imaging the whole sky. EnVisS will allow to study the comet dust environment, the Field of View( FoV) of the instrument is designed to acquire the full sky thanks to the B2 spacecraft rotation. The camera will feature a flexible push-broom/push-frame imaging technique, thus acquiring slices of the sky, while the probe rotates; on-ground, the acquired slices will be stitched together to form a full-sky image. Three broadband filters, transmitting in the visible wavelength range from 550 to 800 nm, are foreseen for the camera: one "intensity" filter (i.e non-polarizing) and two polarizing ones. EnVisS will map the intensity, the degree of linear polarization and polarization angle orientation of the light scattered by the dust particles in the comet coma with a full 180° phase angle coverage. Such a measurement is unique, it has never been carried out in space; HOPE, onboard the Giotto spacecraft, had the chance to observe only a very narrow angle FoV in the direction opposite to the motion of the spacecraft. The monitoring of linear polarization provides some clues about dust particles properties (e.g. size and distribution, morphology and porosity,..). Furthermore, the coma investigation will be conducted throughout the full fly-by of the comet from an advantageous point inside the coma itself. The status of the project and the scientific capabilities of the EnVisS instrument will be presented.