The EnVisS camera for the Comet Interceptor ESA mission

Abstract

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 interstellar object.

The EnVisS (Entire Visible Sky) camera is being designed for mapping and studying the coma of the selected mission target via imaging the whole sky.

1. Introduction

Comet Interceptor will fly-by a truly pristine comet, i.e. an object very likely entering the inner Solar System for the first time, or, possibly, an interstellar object originating at another star [1].

The present Comet Interceptor mission configuration comprises a spacecraft and two probes. The spacecraft, called A, will make remote and in-situ observation of the target from afar. The two probes, one provided by the Japan Aerospace Exploration Agency (JAXA), called B1, and the other one provided by ESA, called B2, will venture near to the target.

The EnVisS instrument is foreseen to be mounted on B2. EnVisS is an all-sky camera specifically designed to study the coma of the object over the entire sky.

The B2 probe will be a spinning spacecraft, thus a rotational push-broom or push-frame imaging technique can be adopted for EnVisS to scan and image the whole scene around the spacecraft. Filter strips directly bonded to the detector, or mounted very near to it, can be foreseen for studying the target in different wavelength ranges ([2] [3]) or performing polarimetric imaging. Having no moving parts, this solution allows for a compact, low mass and low complexity camera to be implemented. Moreover, since EnVisS is imaging the whole sky, no specific pointing requirements are to be requested for the fly-by geometry.

The EnVisS instrument features a fish-eye lens [5] coupled to a commercial space-qualified detector from 3D-Plus [4] and ad-hoc power and data handling units and software. A prototype of the EnVisS fish-eye lens optical head will be realized, in the coming months, by Leonardo SpA in Florence (Italy) [6].

2. The EnVisS camera concept

EnVisS will feature a push-frame imaging technique, thus acquiring slices of the sky, while the probe rotates (see Figure 1); the slices will be stitched together after acquisition to obtain a full sky image.

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