Colour and Stereo Surface Imaging System
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| Operator | European Space Agency |
|---|---|
| Manufacturer | University of Bern, Switzerland |
| Instrument type | imaging system |
| Function | surface morphology, mineralogy and topography |
| Mission duration | Planned: 7 years.[1][2] Elapsed: 8 years, 2 months, 3 days |
| Began operations | 21 April 2018[3] |
| Website | www.cassis.unibe.ch |
| Properties | |
| Mass | 18.05 kg[4] |
| Dimensions | 13.5 cm primary mirror |
| Power consumption | 56.7 W (peak) 17.3 W (average) |
| Resolution | 4.67 m/px (scale) from 407 km |
| Spectral band | visible (4 filters, effective wavelengths of 500, 675, 836, and 937 nm) |
| Host spacecraft | |
| Spacecraft | ExoMars Trace Gas Orbiter |
| Operator | ESA |
| Launch date | 14 March 2016, 09:31 UTC |
| Rocket | Proton-M/Briz-M |
| Launch site | Baikonur 200/39 |
| COSPAR ID | 2016-017A |
Colour and Stereo Surface Imaging System (CaSSIS) is a colour and stereo imaging system on board the ExoMars Trace Gas Orbiter (TGO) launched to Mars orbit on 14 March 2016.
CaSSIS is designed to take images of the surface of Mars from orbit at a spatial scale of 4.5 m/px in colour and in stereo[5]. The instrument is used to study colour variegation on the surface (supporting the identification and emplacement of minerals on the surface), to monitor currently active processes on the surface (e.g. polar processes), and to characterize present and future landing sites. The Principal Investigator (PI) is Nicolas Thomas, from the University of Bern, Switzerland[6].
Overview[edit]
CaSSIS is one of four science instruments on board the European ExoMars TGO orbiter and is the main imaging system[7].
Since April 2018,[3] CaSSIS has been acquiring images of the surface of Mars in colour and stereo with a spatial scale of around 4.5 metres/px[8].
Objectives[edit]
The primary objectives of the instrument[9] are
1) to characterise sites which have been identified as potential sources of trace gases,
(2) to investigate dynamic surface processes (e.g. sublimation, erosional processes, impacts, and potential volcanism) which may help to constrain the atmospheric gas inventory, and
(3) to characterise potential future landing sites by measuring local (down to ∼10 m) slopes.
History[edit]
A NASA-ESA Joint Instrument Definition Team (JIDT) report (see [10]) for a mission to study trace gases at Mars suggested provision of very high spatial resolution imaging or mapping instruments (e.g., cameras and/or multi-beam active lasers) to provide geological context and location of small-area sources of trace gases should they exist (e.g., a volcanic vent, rift or crater). The definition team focused on a High Resolution Colour Stereo Camera (HRCSC) concept that would provide geological characterisation of potential trace gas sources. An Announcement of Opportunity (AO) was released jointly by NASA and ESA for provision of payload in January 2010[11].
A joint US-European team successfully responded to this AO [12]with an instrument called HiSCI [13]. However, following the loss of the attempted collaboration with NASA in ExoMars [14], both the programme and the payload were reconfigured in 2012 as a joint ESA-Roscosmos endeavour. The schedule for TGO was maintained with a payload of 4 instruments (2 Russian led, 2 European led) and an entry, descent, and landing demonstrator (subsequently called Schiaparelli). The Colour and Stereo Surface Imaging System (CaSSIS) became the main imaging system on the spacecraft replacing the HiSCI instrument[15].
Compromises were needed to meet the revised technical and programmatic constraints[16]. The reduced development time drove the use of a detector and proximity electronics previously developed for the BepiColombo SIMBIO-SYS instrument slated to fly on ESA’s BepiColombo mission to Mercury in 2018 [17]. This system operates in a “push-frame” mode (an intermediate approach between conventional line-scanners and framing imaging systems). In addition, a previously manufactured primary mirror for the telescope needed to be used to reduce delivery times[18]. A further consequence of the schedule was that a “proto-flight” approach to instrument development was adopted. In spite of these compromises, it was important that CaSSIS retain much of the capability of the original HiSCI concept and hence its scientific usefulness as a full-swath colour, stereo imaging system at a resolution exceeding most previous imagers with the exception of High Resolution Imaging Science Experiment (HiRISE) and the Mars Orbiter Camera (MOC).
The commitment from all sides to build the instrument came relatively late with delivery to ESA occurring just 5 months before launch[19][20] well after the delivery of the flight units of the other instruments on TGO.
Imaging Approach[edit]
CaSSIS is a push-frame imaging system designed to take images of the surface of Mars in four colours and with the capability to obtain stereo by using a rotation mechanism[21]. It takes small images (called framelets) very quickly as the spacecraft flies over the surface. These framelets are transmitted to Earth, calibrated and then assembled into long swaths that cover typically 9.5 km × 40 km of the Martian surface per image. The time between each framelet is in the range of 350 to 400 milliseconds which is derived from the properties of the telescope and the detector[22].
CaSSIS is also designed to take stereo images[23]. It does this by an off-pointing of the telescope by 10° from the nadir direction. A motor is used to rotate the telescope so that it is aligned with the ground-track but pointing forward. Once the image is acquired, the telescope is rotated by 180° about the nadir-pointing axis so that the telescope points backwards. It has 45 seconds to perform this rotation before the next image must be acquired in order to have overlap of the two images. This leads to a stereo convergence angle of 22.4° (on average and taking into account the curvature of Mars) and provides excellent stereo imagery of the surface.
Team[edit]
Engineering Team[edit]
The development of CaSSIS was led by the Space Research and Planetology Division of the Physikalisches Institut of the University of Bern. Sub-systems of the instrument[24] were provided by RUAG Space, Zurich (now Thales Alenia Space, Switzerland), the Astronomical Observatory, Padova (sub-contracting to Leonardo S.p.A.), and the Space Research Centre, Warsaw (sub-contracting to CreoTech, and in collaboration with SGF, Budapest[25]
Science Team[edit]
The science team[26] comprises scientists from several countries in Europe. Gabriele Cremonese from Padova is the co-PI for the instrument in recognition of the Italian contribution to the instrument (see below). The original members of the HiSCI team (including those from the United States) are co-investigators (co-Is) in the CaSSIS team.
Operations Team[edit]
The operation of the instrument is led by the team at the University of Bern. Operational planning is supported by the Open University, Milton Keynes while many elements of the planning software is based on software developed for HiRISE and provided by the Lunar and Planetary Laboratory of the University of Arizona. The US Geological Survey in Flagstaff, Arizona has also developed software for data processing. The stereo processing and digital terrain model production from the images is coordinated by the Astronomical Observatory in Padova who also archive the topographical data. The data are archived by the European Space Astronomy Centre (ESAC) near Madrid.
Example of Images[edit]
As of December 2022, CaSSIS has taken over 35,000 images of the surface of Mars. The image here is of Juventae Chasma and was obtained and released in October 2018.[27]
Book[edit]
Some of the best images from the CaSSIS instrument have been published in Bilder vom Mars published by [Werd&Weber Verlag] in Thun. The descriptions in the book are provided in five languages (English, French, German, Italian, and Russian).
See also[edit]
References[edit]
- ↑ "ExoMars Trace Gas Orbiter and Schiaparelli Mission (2016)". European Space Agency. 16 October 2016. Retrieved 24 October 2016.
- ↑ Allen, Mark A.; Witasse, Olivier (2011). 2016 ESA/NASA ExoMARS/Trace Gas Orbiter. Mars Exploration Program Assessment Group. 15–16 June 2011. Lisbon, Portugal. hdl:2014/42148.
- ↑ 3.0 3.1 Mitschdoerfer, Pia; et al. (9 April 2018). "ExoMars poised to start science mission". European Space Agency. Retrieved 18 June 2018.
- ↑ [https://link.springer.com/article/10.1007/s11214-017-0421-1 Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ "CaSSIS mission: The camera capturing Mars' craters and canyons". BBC News. 13 February 2021.
- ↑ "ESA - Robotic Exploration of Mars - TGO's colour and stereo camera: An interview with Nicolas Thomas, Principal Investigator of CaSSIS".
- ↑ "ESA - Robotic Exploration of Mars - ExoMars Trace Gas Orbiter Instruments".
- ↑ "CaSSIS mission: The camera capturing Mars' craters and canyons". BBC News. 13 February 2021.
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ Zurek, R.~W., A. Chicarro, M.~A. Allen, J.-L. Bertaux, R.~T. Clancy, F. Daerden, V. Formisano, J.~B. Garvin, G. Neukum, and M.~D. Smith, (2011), Assessment of a 2016 mission concept: The search for trace gases in the atmosphere of Mars, Planetary and Space Science, 59, 284, doi:10.1016/j.pss.2010.07.007.
- ↑ "ESA - Robotic Exploration of Mars - Announcement of Opportunity for ExoMars Trace Gas Orbiter Instruments".
- ↑ "Instruments selected for Mars".
- ↑ McEwen, A.~S., N. Thomas, J. Bridges, S. Byrne, G. Cremonese, W. Delamere, C. Hansen, E. Hauber, A. Ivanov, L. Kestay, R. Kirk, N. Mangold, W. Markiewicz, M. Massironi, S. Mattson, C. Okubo, and J. Wray, (2011), The High-resolution Stereo Color Imager (HiSCI) on ExoMars Trace Gas Orbiter (TGO), EPSC-DPS Joint Meeting 2011, 2011, 1352, doi:. McEwen, A., N. Thomas, J. Bridges, S. Byrne, G. Cremonese, W. Delamere, C. Hansen, E. Hauber, A. Ivanov, L. Kestay, R. Kirk, N. Mangold, W.~J. Markiewicz, M. Massironi, S. Mattson, C. Okubo, and J. Wray, (2011), HiSCI Experiment on ExoMars Trace Gas Orbiter, 42nd Annual Lunar and Planetary Science Conference, 2270, doi:.
- ↑ "ExoMars co-operation between NASA and Esa near collapse". BBC News. 6 February 2012.
- ↑ https://elib.dlr.de/91920/1/Thomas_et_al.CaSSIS.Mars_8_2014.pdf
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ Flamini, E., F. Capaccioni, L. Colangeli, G. Cremonese, A. Doressoundiram, J.~L. Josset, Y. Langevin, S. Debei, M.~T. Capria, M.~C. de Sanctis, L. Marinangeli, M. Massironi, E. Mazzotta Epifani, G. Naletto, P. Palumbo, P. Eng, J.~F. Roig, A. Caporali, V. da Deppo, S. Erard, C. Federico, O. Forni, M. Sgavetti, G. Filacchione, L. Giacomini, G. Marra, E. Martellato, M. Zusi, M. Cosi, C. Bettanini, L. Calamai, M. Zaccariotto, L. Tommasi, M. Dami, J. Ficai Veltroni, F. Poulet, Y. Hello, and Simbio-Sys Team, (2010), SIMBIO-SYS: The spectrometer and imagers integrated observatory system for the BepiColombo planetary orbiter, Planetary and Space Science, 58, 125, doi:10.1016/j.pss.2009.06.017.
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ "Swiss camera to launch to Mars". 20 November 2017.
- ↑ https://www.cassis.unibe.ch
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ "Hardware Industrial Partners". 9 March 2016.
- ↑ Thomas, N., and 60 colleagues, (2017), The Colour and Stereo Surface Imaging System (CaSSIS) for the ExoMars Trace Gas Orbiter, Space Science Reviews, 212, 1897, doi:10.1007/s11214-017-0421-1.
- ↑ "Science Team". 7 March 2016.
- ↑ https://www.esa.int/var/esa/storage/images/esa_multimedia/images/2018/10/layered_mound_in_juventae_chasma/17836106-1-eng-GB/Layered_mound_in_Juventae_Chasma_pillars.jpg
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