Posted on November 20, 2024November 20, 2024 by David Dickinson
How Scientists Repurposed a Camera on ESA’s Mars Express Mission
A camera aboard the Mars Express orbiter finds a new lease on life.
Sometimes, limitations can lead to innovation. A recent paper highlights how researchers are utilizing the VMC (Visual Monitoring Camera) aboard the European Space Agency’s (ESA) venerable Mars Express orbiter.
The work is a collaboration between the European Space Agency (ESA), the IAA-CSIC Institute of Astrophysics in Andalusia Spain, and the University of the Basque Country.
A Mars Webcam
Mars Express is ESA’s first Mars mission. Launched on a Soyuz rocket, Mars Express arrived in orbit around the Red Planet on Christmas Day 2003. The VMC was designed for one primary purpose: to monitor the departure of the ill-fated Beagle 2 lander, which was released from Mars Express on December 19th, just under a week prior to orbital insertion. The camera was switched off after the Beagle 2 release was complete, then brought back online in 2007.
“(The) VMC camera was originally intended to take only a few snapshots of the lander release,” Alejandro Cardesín-Moinelo (ESA Mars Express Science Operations) told Universe Today. “The camera was then ‘forgotten’ for a few years until it was switched on again in 2007 as an engineering test. This showed a great value for public outreach and so it started to be operated regularly. In recent years, VMC images started getting more and more popular and raised the attention of the community due to its scientific potential.”
A Unique Orbit
The VMC was initially only tasked with taking supplementary images of Mars. A 2016 collaboration saw a push to upgrade the camera for scientific use. In 2018, it found a role monitoring the Martian weather. Mars Express is in a nearly polar orbit. Its distant 11,560 kilometer apoapsis vantage point along its 7.5 hour orbit is ideal for full disk observations.
The VMC camera has a 40 by 30 degree wide field of view, which enables it to monitor full disk weather on Mars. Mars Express also offers the key advantage of a more flexible orbit versus other missions. The mission sees regions at different times and at varying illuminations.
Mars Express as a Weather Satellite
“VMC has proven to be a great asset in global monitoring of the Martian atmosphere, complementing all other scientific instruments and providing very useful information on meteorological phenomena, mostly atmospheric aerosols, ice clouds and dust storms,” says Cardesín-Moinelo. “Among the many scientific contributions, the main discovery was the striking Arsia Mons ‘elongated cloud’ spotted in 2018, a 1,500 kilometer cloud which had not been reported by any previous mission.”
The imaging workflow for VMC uses bias, flat, and dark frames, akin to methods utilized by amateur astrophotographers to process images. The VMC operates similarly to older webcams and produces smaller images, facilitating their transmission back to Earth. This not only allows the VMC to carry out serious science, but also enables it to be calibrated for full disk photometry, useful for tracking weather and changes on Mars.
Although VMC has a limited dynamic range, it employs various exposures to achieve HDR (High Dynamic Range) imaging needed to reveal elusive features, similar to techniques used in smartphone cameras.
Evolution of a Mars Camera
“VMC is analogous to a ‘cheap’ cell phone camera from the early 2000s, offering less than 0.2 megapixels,” states Cardesín-Moinelo. “While it may not provide an extensive level of detail, its unique positioning in an ‘extraordinary location’ allows us to capture numerous images of the full disk of Mars on a daily basis. This capability enables monitoring of atmospheric clouds and dust storms, which cannot be accomplished with any other instrument. The ongoing evolution of these 'cheap' wide cameras has proven tremendously valuable, prompting considerations of deploying an up-to-date camera in future missions with greater resolution and improved performance to enhance global planetary monitoring.”
Nonetheless, VMC was not without its challenges. The internal clock of Mars Express is not entirely accurate, and the VMC is fixed to the spacecraft's chassis, meaning it points where Mars Express points. The team utilizes star field shots to calibrate the spacecraft's position, as well as utilizing transits of the moons Phobos and Deimos across the disk of Mars to verify timestamps, ensuring accurate data collection.
VMC is not the only instrument monitoring Martian weather. The United Arab Emirates' Mars Hope is another mission conducting full disk imaging and gathering essential real-time data. These complementary perspectives are beneficial during the evolving dust storm season on Mars, enhancing data richness and scientific understanding.
Small Cameras for Small Missions
Consequently, these types of basic off-the-shelf cameras are becoming standard equipment on small satellites. Notable instances in planetary science include Mars Cube One (MarCO-A and B) that accompanied NASA's Mars Insight lander, as well as the Minerva-II landers aboard the Hayabusa 2 asteroid mission. The Italian Space Agency's LICIACube mission famously witnessed the DART impact into asteroid Dimorphos in 2022.
This signifies a transformative shift for Martian weather forecasts. It's intriguing to witness the extraordinary imagery of Mars provided by VMC, showcasing how aging technology in our solar system can discover a new practical purpose.