Space Sunday: helicopters, craters and a sunny ISS

A perspective view of Korolev Crater, Mars. Measuring 82 kilometres across and located in the northern lowlands, this image of the crater was digitally created from pictures taken by the European Space Agency’s Mars Express orbiter. Story below. Credit: ESA / DLR / FU Berlin

Later this month an Atlas V launch vehicle should depart Canaveral Air Force Station at the start of what will be a 6+ month cruise to Mars for its payload, the Mars 2020 rover Perseverance. A twin to the Mars Science Laboratory (MSL) rover Curiosity that has been operating on the red planet since 2012, the Mars 2020 vehicle carries a range of updated systems and a science package designed, among other things, to investigate the possibility of past life on Mars, and the potential for preservation of biosignatures within accessible geological materials.

I’ll have a lot more to say about the rover – already nicknamed “Percy” in some circles – but here I’d like to focus on the rover’s travelling companion, Ingenuity, the perfectly named Mars helicopter.

Weighing just 1.8 kilogrammes, Ingenuity will make the trip to Mars mounted on the underside of Perseverance, where it will sit until such time in the rover’s surface mission – probably around the 60-day mark – will hopefully be in a position to deploy the helicopter ready to undertake up to five flights under its own power.

Mars Helicopter Ingenuity. Credit: NASA/JPL

The helicopter is very much a proof-of-concept vehicle, but if it proves successful, it will pave the way for future helicopter drones to assist in Mars surface missions. Such drones could, for example, be used to provide better terrain images and mapping when planning routes for future rovers to take, scout locations that may be suitable for more detailed study by rovers, and even undertake the recovery of samples obtained by other missions and left for collection, and return them to the craft that will carry them back to Earth for analysis.

Such future helicopter systems would likely be larger and heavier than Ingenuity, and capable of carrying their own science packages for use for studying things like the atmosphere around them. Further, their use is neither restricted to automated missions or to Mars. There is no reason why, if successful, Ingenuity shouldn’t pave the way for helicopter drones that could be used in conjunction with human missions on Mars, or in automated missions to Titan.

First, however, Ingenuity has to safely get to the surface of Mars – and that means experiencing the same “seven minutes of terror” of the entry, decent and landing (EDL) phase of the rover’s. mission. After that, it has to survive 60 days slung under the rover’s belly, with just 13 centimetres clearance between its protective shield and whatever is under the rover before it is liable to be a a location where it can be deployed. And then the fun begins.

Ingenuity stowed under Perseverance. The blue arrow shows the rotor mechanism, the red the helicopter’s body, as it sits on its side under the rover. Credit: NASA/JPL

Ingenuity has to be placed on ground that is relatively flat and free from significant obstacles – an area roughly 10 metres on a side. The shield protecting the helicopter will then be dropped by the rover at the edge of the location, and checks will be made to confirm the shield has fallen clear of both helicopter and rover and that the helicopter’s systems are in working order, a process that will take several days. After this, the rover will be commanded to roll forward several metres in readiness for actual helicopter deployment.

After this, the actual deployment process can commence. Due to its shape, the helicopter is stowed on its side under the rover, relative to the ground. This means the locking system that holds it in place must be released to allow the helicopter to drop through 90º, bringing two of its landing legs parallel to the ground. The remaining two legs will then be released to drop and lock into position, a the helicopter itself released from its restraining clips and literally drops down to the ground, and the rover drives clear, leaving Ingenuity to go through final checks head of its first flight.

The reason the helicopter is carried horizontally under the rover is because its rotor system makes it taller than it is wide, and the engineering team didn’t want to complicate the design by making it such that rotors would have to be unpacked / unfolded / deployed; they are instead ready for use once the helicopter is upright.

Ingenuity has two contra-rotating main rotors, one above the other. These not only provide lift and motion; the fact that they are contra-rotating means they each cancel the torque they would each induce in the helicopter’s body, something that would otherwise require a tail rotor to prevent it from also spinning when flying.

Once ready to go, Ingenuity is expected to fly up to five times, as noted, reaching heights of between 3 and 10 metres and potentially covering 300 metres per flight. Data from each flight will be shared from the helicopter and the rover using the Zigbee wi-fi low-power communications protocol, with Perseverance acting as the helicopter’s communications relay with Earth. Cameras on the helicopter should also provide the first ever bird’s eye view of low-level flying above Mars.

An artist’s impression of Ingenuity flying free of Perseverance, seen in the background. Credit: NASA/JPL

Flight over Korolev Crater

Staying with Mars and flying, on June 20th, 2020, the European Space Agency released a video simulating a flight over the crater Korolev on Mars, built from stereo images captured by the High Resolution Stereo Camera (HRSC) aboard the agency’s Mars Express orbiter.

Korolev – named for the father of Russian / Soviet rocket systems, Sergei Korolev – is one of the most distinctive craters in the northern hemisphere of Mars. It measures some 82 kilometres in diameter and is an estimated 2 km deep and likely of impact origin. Located in the northern Planum Boreum, the northern polar plain which surrounds the north polar ice cap, the crater is distinctive because it is filled with water ice estimated to be up to 2,200 cubic kilometres in volume – or equivalent to Canada’s Great Bear Lake.

Korolev Crater (arrowed) and its proximity to the Martian northern polar regions. Credit: ESA

The video was created using an image mosaic constructed from single orbit observations made by HRSC as Mars Express directly overflew the crater during 2018. The images were then combined with topography data obtained through the stereo channels on HRSC to generate a 3D model of the crater, its rim and the surrounding land, which could then be rendered using data to simulate flying over the crater from different directions / perspective, edited together into the finished film.

Normally, water ice wouldn’t be able to survive on Mars like this; such is the extremely low atmospheric pressure on the planet, surface ice should simply sublimate away. However, Korolev is what is called a natural cold trap: the air  directly over the ice is cooled, causing it to condense and descend into the crater, forming a shield of cold atmosphere of the ice, preventing it from sublimating.

The white areas around both sides of the crater walls are not due to water ice, but as likely frozen carbon dioxide mixed with some water vapour found within the Martian atmosphere, which have been drawn out by the low temperatures to create Martian “frost”.

Craters like Korolev might in the future help humans establish permanent bases on Mars, providing as they do a fairly readily available source of water ice that could be put to a variety of uses.

ISS in Solar Transit

Thierry Legault is one of the world’s foremost astrophotographers. He started as a deep sky photographer, but in 1994 he came to world-wide attention photographing the collision of the remnants of comet Shoemaker-Levy 9 with the atmosphere of Jupiter in 1994.

Since then, he’s captured many remarkable images of the planets, deep space objects and space craft, one of the most remarkable being his 2009 image of the space shuttle Atlantis transiting across the face of the Sun, as seen from the Kennedy Space Centre during STS-125, the fifth and final shuttle mission to service the Hubble Space Telescope.

The space shuttle Atlantis transits the Sun as seen from Kennedy Space Centre in May 2009 during mission STS-125. Credit: Thierry Legault / NASA

On June 24th/25th, 2020 however, Thierry surpassed even this, capturing the International Space Station (ISS) in extraordinary detail as it transited the Sun. He photographed the station using a Olympus E M-1 II camera attached to a CFF apochromatic triplet 8″ refractor telescope, shooting at a continuous 60 frames per second. He’d previous calculated the best place in France to capture the images using ISS orbital data and Google Maps to show him possible locations along the station’s track – his best being some 300 km from his home in Paris.

He modestly states that such photographs are 50% weather conditions and 50% luck – however, the sheer clarity of the images clearly show he has a high degree of skill in making his calculations and in understanding his equipment.

A series of images of the ISS transiting the Sun, June 24th, 2020 with, inset, annotated details. Credit: Thierry Legault via Twitter

The individual frames of the series reveal the ISS in stunning detail – modules, solar panels – even the bullet form of the Crew Dragon can be seen, together with the 17.6 metre long Canadarm2 robot arm on the station, bent at the elbow as it manipulates an external pallet, or stowage platform, used to hold replacements units for elements of the station’s external equipment and parts.

For those keen on astrophotography, I recommend following him on Twitter, and keeping an eye on his website.