On-Ground Performance and Calibration of the ExoMars Trace Gas Orbiter CaSSIS Imager

The European Space Agency’s ExoMars Trace Gas Orbiter (TGO) seeks to investigate the biological or geological origin of trace gases found on Mars. The TGO carries a payload of four instruments in order to reach its scientific goals, including the Colour and Stereo Surface Imaging System (CaSSIS). CaSSIS is a colour and stereo telescopic camera that will be capable of taking high-resolution images of the martian surface. Before shipment of the instrument for integration onto the TGO, a detailed calibration campaign was performed, and a number of calibration products were gathered and utilised as part of the in-flight calibration campaign. This paper presents the results of on-ground calibration measurements carried out in order to assess the pre-flight performance of CaSSIS. All indications are that CaSSIS will perform very well on arrival at Mars and will be successful in reaching its scientific objectives

The BepiColombo Laser Altimeter

The BepiColombo Laser Altimeter (BELA) is the first European laser altimeter constructed for interplanetary flight. BELA uses a 50 mJ pulsed Nd:YAG laser operating at 10 Hz with a 20 cm aperture receiver to perform the ranging. The instrument also uses a digital approach for range detection and pulse analysis. The ranging accuracy is expected to be better than 2 metres and ∼20 cm in optimum conditions. With the given, only slightly elliptical, orbit, BELA should return a consistent data set for the most if not all of the planet. The instrument is required to function in an extreme environment with the thermal issues being particularly demanding. Novel solutions have been taken to resolve these issues. BELA is described in detail and its predicted performance outlined on the basis of pre-flight testing

The colour and stereo surface imaging system (CaSSIS) for the ExoMars Trace Gas Orbiter

The Colour and Stereo Surface Imaging System (CaSSIS) is the main imaging system onboard the European Space Agency’s ExoMars Trace Gas Orbiter (TGO) which was launched on 14 March 2016. CaSSIS is intended to acquire moderately high resolution (4.6 m/pixel) targeted images of Mars at a rate of 10–20 images per day from a roughly circular orbit 400 km above the surface. Each image can be acquired in up to four colours and stereo capability is foreseen by the use of a novel rotation mechanism. A typical product from one image acquisition will be a 9.5 km×∼45 km swath in full colour and stereo in one over-flight of the target thereby reducing atmospheric influences inherent in stereo and colour products from previous high resolution imagers. This paper describes the instrument including several novel technical solutions required to achieve the scientific requirements