CHANCES Instrument Overview

CHANCES (Colour High-resolution Apophis Narrow-angle CamEra System) is, as its name suggests, a camera system designed to capture high-resolution colour images of the asteroid Apophis. ESA selected the Bernese instrument as a "payload of opportunity" for RAMSES in April 2025, to characterize the shape, scrutinize the surface of the asteroid and to detect possible subtle changes before, during and after its close-encounter with Earth.

The compact, lightweight yet powerful CHANCES camera system combines earlier developments from the University of Bern—such as CoCA, the main camera of ESA's Comet Interceptor mission, or the Bernese Mars Camera CaSSIS, which has been providing high-resolution images of the surface of the Red Planet since 2018—with innovative aspects that are tailored to the specific objectives of the mission, ideally complementing RAMSES' baseline payload.

© University of Bern

Capabilities

Instrument Capabilities

High-Resolution

CHANCES will be able to offer detailed high-resolution views of the asteroid's surface with a Ground Sampling Distance (GSD) of 6cm/px from 5 km.

The resolution capabilities of the CHANCES instrument in comparison with the baseline AFC resolution. © Martin Jutzi and Antoine Pommerol (WP/University of Bern)

Refocusing

The instrument has refocusing capabilities for very short range sharp imaging. Varying distances are a challenge for long-focal length narrow-angle cameras (NAC)—using a refocus-filter allows for 1.5 cm/px from 1.2 km. The possibility of including one filter for very close distance (500 m) is being considered.

Multispectrality

CHANCES has multispectral capabilities at visible range (Vis) and short-wavelength infrared (SWIR). Its wavelength range is 400 - 1700 nm and includes 6 different bandpasses.

Polarisation Sensing

By analysing how the sunglight is scattered and polarised by regolith particles over a range of phase angles, polarimetry can reveal variations in regolith properties and composition that are not easily detected through traditional spectral imaging alone, including surface porosity. For this reason, CHANCES is equipped with two crossed linear polarisers.

Very High SNR & Dynamic Range

CHANCES has a signal-to-noise ratio (SNR) of >200 and a high dynamic range.