Space Sci Rev DOI 10.1007/s11214-017-0404-2 On-Ground Performance and Calibration of the ExoMars Trace Gas Orbiter CaSSIS Imager V. Roloff 1,2 · A. Pommerol 1,2 · L. Gambicorti 1,3 · A. Servonet 1 · N. Thomas 1,2 · M. Brändli 1 · A. Casciello 4 · G. Cremonese 5 · V. Da Deppo 6 · M. Erismann 1 · I. Ficai Veltroni 7 · M. Gerber 1 · M. Gruber 1 · P. Gubler 1 · T. Hausner 4 · M. Johnson 4 · P. Lochmatter 4 · E. Pelò 4 · B. Sodor 8 · S. Szalai 8 · G. Troznai 8 · D. Vernani 4 · T. Weigel 4 · R. Ziethe 1 · C. Zimmermann 1 Received: 28 November 2016 / Accepted: 1 August 2017 © Springer Science+Business Media B.V. 2017 Abstract The European Space Agency’s ExoMars Trace Gas Orbiter (TGO) seeks to in- vestigate 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 indi- cations are that CaSSIS will perform very well on arrival at Mars and will be successful in reaching its scientific objectives. Keywords ExoMars ESA mission · Trace Gas Orbiter · CaSSIS · Calibration · Mars · Imaging ExoMars-16 Edited by Håkan Svedhem and Christopher T. Russell B V. Roloff victoria.roloff@space.unibe.ch 1 Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland 2 NCCR PlanetS, Sidlerstrasse 5, 3012 Bern, Switzerland 3 Present address: ATG Europe B.V. on behalf of ESA—European Space Agency, ESA—ESTEC/TEC—MMO, Keplerlaan 1, P.O. Box 299, 2200 AG Noordwijk, The Netherlands 4 RUAG Space, Schaffhauserstrasse 580, 8052 Zürich, Switzerland 5 INAF-Osservatorio Astronomicodi Padova, Vicolo Osservatorio 5, 35122 Padova, Italy 6 CNR-IFN Padova, Via Trasea 7, 35131 Padova, Italy 7 Selex ES, Via A. Einstein 35, 50013 Campi Bisenzio, FI, Italy 8 SGF Technology Associates Co. Ltd., Pipiske u. 1-5/20, 1121 Budapest, Hungary