Science with small cameras: The Visual Monitoring Camera on-board Mars Express

The Visual Monitoring Camera (VMC) on board the European Space Agency's (ESA) Mars Express (MEX) orbiter was originally designed as an engineering camera whose purpose was to monitor the separation of the Beagle-2 lander in 2003. In 2007, the camera was switched on again for science outreach purposes, becoming "the ESA Mars Webcam". Following the subsequent use of VMC data for Mars atmospheric science [1,2] the VMC was designated a scientific instrument in 2016. The scientific success of this "webcam" around Mars highlights how small cameras on planetary missions can yield high science return, which has implications for potential future missions to Mars, including CubeSat and Small Sat missions. The VMC is a 640x480 pixel camera with a large field of view (FOV) of ~40 x 31°. The wide FOV allows the camera to capture both the entire disk of Mars within the image and to perform observations over a wide region of the limb. This combined with the elliptical orbit of MEX, which enables observations at various distances and local times, allows the study of regional and global scale atmospheric phenomena. Currently only VMC on MEX, the Imaging Ultraviolet Spectrograph (IUVS) instrument on NASA's Mars Atmosphere and Volatile Evolution (MAVEN), and the Mars Colour Camera (MCC) on the Indian Space Research Organisation's (ISRO) Mars Orbiter Mission (MOM) have these capabilities. For the past few decades a significant proportion of Mars science research has been focused on observations taken in sun-synchronous orbits and by high-resolution imaging, allowing scientists to observe changes in the same location and identify smaller features in the landscape. In contrast, the large-scale atmospheric dynamics of Mars are fast-paced, and a high temporal resolution of observations at different local times is needed to understand how these dynamics develop. VMC meets this need. For such large-scale phenomena, a wide FOV is also important for capturing the entire feature, such as the Arsia Mons cloud [3] and the recurrent double cyclone [4]. Owing to the high temporal resolution unique to VMC, the science team has been able to stack images from the same observation and also produce mosaics and videos showing the movements of aerosols. VMC images are small in data volume, so the information can be stored and received from VMC even when the available data rates are low. As more missions launch to Mars in the coming years, competition for antenna time on both NASA's Deep Space Network and ESA's ESTRACK network means returning the data to Earth will become an issue for Mars missions. If key science can be achieved with observations of lower data volume, this will help the science return of future missions. We therefore suggest that future missions would benefit from the inclusion of a VMC-like camera, taking into account the hardware improvements made over the last 2 decades. We will present the technical capabilities of VMC, the science that has been possible from this small camera, and discuss the implications for future missions to Mars. At the time of writing, VMC datasets are currently being prepared for ingestion into the Planetary Science Archive (PSA) and are expected to be released to the public by summer 2020. Further results will therefore be presented at COSPAR 2020. [1] Sánchez-Lavega et al., AAS/DPS, 48, 2016 [2] Sánchez-Lavega et al., Icarus 299, 194-205, 2018 [3] Hernandez-Bernal et al., Vienna, Austria, 3rd-8th May 2020, EGU 2020 [4] Sánchez-Lavega et al., J. Geophys. Res., 123, 3020, 2018