content long 25-March-2019 21:50:23

The ExoMars Rover Instrument Suite

CLUPI - Close-UP Imager

Illustration of CLUPI mounted on the ExoMars rover. Credit: Space Exploration Institute

The Close-UP Imager (CLUPI) will be part of the instrument payload on the ExoMars rover, scheduled for launch in 2020.

CLUPI is a camera system designed to acquire high-resolution, colour, close-up images of outcrops, rocks, soils, drill fines and drill core samples. The visual information obtained by CLUPI will be similar to what a geologist would get using a hand lens – if they were on Mars!

The camera system will take images of rock and unconsolidated material at the tens of micrometres to centimetre scale. These images will help scientists determine the environment – for example: aqueous, volcanic, etc. – that gave rise to the rocks that are analysed. This will provide the geological context and therefore improve the scientists' ability to interpret the results obtained by the other rover instruments.

Another very important objective of CLUPI will be to search for morphological biosignatures on outcrops. The primitive types of microorganisms that could have existed on Mars would be very small, probably less than a micron to not more than a few microns in size, but their colonies and biofilms are much larger. Traces of these features may be preserved in the Martian rocks either as mineral-replaced structures and/or as carbon remains trapped in the Martian sediments and encased in a mineral cement. Although the individual cells will be too small to be recognisable in outcrop by CLUPI (complex sample preparation and use of powerful microscopes is necessary for this), the Close Up Imager will be able to image concentrations of colonies forming a spotted, carbon-rich texture called thrombolitic, or forming laminar biofilms.

CLUPI will be an imager with the ability to focus from 10 cm to infinity. At a distance of 10 cm from the object, the resolution of the images will be high – about 7 µm/pixel. To give colour images, the camera will have three layers of pixels – red, green and blue.

CLUPI will also have the possibility to perform z-stacking (or focus stacking) of images when necessary. Z-stacking is a processing technique that combines multiple images taken at different focus distances. The portions that are in focus are extracted to create a new image that has a greater depth of field than any of the original individual images.

CLUPI instrument characteristics
Detector type Full colour APS (Active Pixel Sensor)
Image dimension 2652 pixels × 1768 pixels; 3 colours
Field of View 14° ± 2° diagonal (11.9° × 8.0°)
Image resolution
Viewed area
7 µm/pixel at 10 cm distance, viewed area 1.9 cm × 1.3 cm
39 µm/pixel at 50 cm distance, viewed area 10 cm × 7 cm
79 µm/pixel at 100 cm distance, viewed area 21 cm × 14 cm
Focal length Varying, can take sharp images from 10 cm to infinity
Exposure time Up to 1024 seconds
Spectral range 400 – 700 nm
On-board data processing Automatic exposure time; autofocusing; binning 2×2 and 4×4; z-stacking (between 2 and 16 images); windowing

CLUPI will be located on the drill box of the rover. By using the degrees of freedom provided by both the rover and the drill box, CLUPI will be angled and raised so it can observe in a variety of viewing modes. The use of two fixed mirrors – one flat and one concave – will provide three fields of view (FOV).

Illustration of CLUPI's fields of view.
Credit: Space Exploration Institute

For the geological survey, CLUPI will observe the area immediately in front of the rover, using one of the fields of view – FOV1. This will allow scientists to characterise the physical properties of rocks, such as texture, structure and morphology. In this mode the soil, and in particular the rover's track marks, can also be examined in great detail.

For close-up outcrop observation, CLUPI will look to the side, using another field of view – FOV2. In this mode, and by using the rover's motion, CLUPI can be panned across a rock surface to image its structure. A major goal of this observation mode is to identify water-related information. Colour and layering variations will help to determine a target's geological history and its potential for preserving biosignatures.

The observation of the drilling area will also involve CLUPI's FOV2. As the drill box is rotated, CLUPI can either be in a low position or in a high position. In the low position, it may be able to help characterise rocks and structures, such as crystals in igneous rocks, fracture mineralization, secondary minerals, sediment components and soil particles. In the higher position, CLUPI can achieve a wider coverage, albeit with a somewhat lower resolution.

While the drilling operation is being performed, CLUPI's third field of view - FOV3 - can be used to monitor the process and observe the mound of fines that is generated. Colour and textural variations can be used to infer if the drill has encountered a different type of material or deposit. FOV3 can also be used to obtain information on the soil's mechanical properties, such as grain size, shape and cohesion.

After the drilling operation has been completed and the drill has been retracted, FOV2 can be used to image the state of the surface after drilling, the amount of dislodged fines, their colour and physical properties. From the high position, CLUPI will be able to observe the borehole to a depth of approximately 10 cm, depending on the local illumination conditions; from the low position the visible borehole depth will be 6 cm.

Finally, CLUPI's FOV3 will be used to image the collected core prior to delivery to the rovers' analytical laboratory for further processing and studies. Whereas the PanCam high-resolution camera can obtain a total-view image of the core sample, only CLUPI can image the sample at very high resolution. This will be important for recording the sample's shape, colour, homogeneity, texture, mineral grain size and colours. This information can then be used to compare the core sample with the sampling area, providing a link between surface and subsurface analyses.

CLUPI participants
Principal Investigator
Jean-Luc Josset, Space Exploration Institute, Neuchâtel, Switzerland

Co-Principal Investigator
Frances Westall, Centre de Biophysique Moléculaire, Orléans, France

Co-Principal Investigator
Beda Hofmann, Natural History Museum, Bern, Switzerland
ESA contact
ExoMars instrument engineer
Frederic Haessig, Directorate of Science and Robotic Exploration, European Space Agency
More instrument details
The Close-Up Imager Onboard the ESA ExoMars Rover: Objectives, Description, Operations, and Science Validation Activities
Josset J.-L., et al., Astrobiology, July 2017, 17(6-7), 595-611


Last Update: 25 August 2017

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