Towards the landing of MASCOT on the asteroid Ryogo from the spacecraft Yabosa 2: the operation manager talks about the planning

If all goes as planned, in October 2018 the first lander to leave the Yabosa 2 spacecraft will land (before it itself lands) and for the first time use equipment specially designed for landing on an asteroid 

From the website of the German space agency DLR, translation: Victor Bar, The Israeli "Asteroid Day" community

For almost four years, the scientists and engineers of the German Space Center (DLR) waited until the Japanese Yabusa 2 spacecraft and the all-terrain vehicle developed by the German Space Center DLR reached their destination at the asteroid Ryugu. After arriving on June 27, 2018, the landing is now within reach. Probably in the first week of October 2018 - according to the current plans - MASCOT will be for the first time a soil laboratory Scientifically, with instruments aimed at the asteroid, the Japanese space agency JAXA is currently making gravity measurements, which should determine the density of the asteroid more precisely. This information is very important for MASCOT's landing.

On the asteroid's surface, MASCOT will take measurements from more than one location. It will "decide" autonomously and activate the devices as needed. Project manager Tra-Mi Ho of the Space Systems Institute at DLR explains in an interview how the team prepares the SUV for its mission, how its work will be carried out in the celestial body - and what risks await it. The interview was conducted by Manuela Brown from DLR

When Mascot was launched on December 3, 2014, asteroid Ryugu was still an uncharted region. It is now visible through the Yabusa 2 camera at a distance of at least six kilometers. How does this information help the crew prepare themselves and the crew for the landing?

We are getting more and more of a feel for the asteroid. Most of the information is still under evaluation - so we will discuss two phases on August 14 and 17, 2018 and choose which landing site is the right one. We know we can't land at the higher latitudes and since Ryugu's Hibusa 2 research is focused on sampling the asteroid, there are of course limitations on MASCOT, as MASCOT cannot interfere with the sampling. However, after first evaluating the data, there are still enough interesting regions in the mid-latitudes to be of interest.

In the current images you can clearly see that the asteroid is covered with large rocks and there are also large craters on its surface. Will it affect the landing?

The crater does not worry us - we can land there. However, there are other criteria such as the physical properties of Ryugu that we need to consider – for example, the thermal conditions on the asteroid. If it gets too hot for MASCOT, that's a negative: the devices can only work optimally at their intended operating temperatures, otherwise you get too much noise from the recorded data. And temperatures that are too high or too low are not good for the battery either, otherwise it gets dangerously hot or loses its capacity.

MASCOT's landing process and its action on the asteroid are repeatedly tested by simulations. What does the MASCOT team need to know about asteroid Ryugu to best prepare the SUV for its mission?

The Japanese space agency JAXA is currently conducting gravity measurements on the asteroid - that's why we are waiting for the exact values ​​of Ryogo's gravity. This affects the bounce behavior, and MASCOT's recovery and therefore also the final point where the SUV will stop after landing. As I said, the information about the thermal properties of the asteroid is still missing and being studied. Another important aspect is the size of the rocks on Ryugu, MASCOT can get stuck if the rocks are a certain size.

With each new piece of information about Ryugu, the mission becomes more possible to plan and execute. What adjustments and decisions has the team already made?

For example, in our last simulation, we found that jumping a long distance, that is, jumping more than ten meters, would waste a lot of time in the impact phase until MASCOT comes to rest. This time it's important because we only have 16 hours of life. And we also have to remember that MASCOT also needs to upload its data to the Hibusa2 mother spacecraft. From a scientific point of view, it also seems like the composition of the asteroid's surface is not that different, so we don't need big jumps to find something more interesting at a distant measurement point - so the jump distance will be one to several meters.

What is being done here on the ground in the labs or computers, so that the landing and the scientific work can automatically proceed smoothly?

On the one hand, the finding of a correct landing place. For us engineers it is important that the thermal conditions are suitable, but the mascot must also land in a place where the change of day and night of the asteroid is good. Night means: we cannot see Hayabusa2 and cannot upload and save data on the spacecraft.

In addition, we define as one day the operational sequence of MASCOT. The rover is operated independently on the asteroid and must work well with these sequences for the science measurements to take place. During the mission, MASCOT independently decides how and when to initiate these sequences. Inside the SUV is built software that gives the tool autonomy and then determines when MASCOT has reached rest and measurements can begin.

Should MASCOT make decisions completely independently?

Exactly, MASCOT decides on its own. However, we also limit it in terms of time, if MASCOT makes a wrong decision, because, for example, the information from the sensors is not ideal for it, it will nevertheless start the measurements after a given time difference, we do not want to lose time unnecessarily.

The landing is planned for the first week of October 2018. What does it depend on, and how certain is the landing date?

The specific date depends on various criteria. The landing will be coordinated with the Hayabusa2 spacecraft project team. For the Mascot separation, the spacecraft has to descend to the surface of the asteroid and eject the lander at a certain point in time and in a certain location. The landing site also has an impact on the schedule. There may also be unexpected constraints: for example error messages we receive that must be landed later. However, it depends on how serious these error messages are and what steps need to be taken to fix the error. However, there is also a "point of no return" – a point in time from which you cannot stop the landing.

The Space Experiment Control Center (MUSC) at DLR also has a model of MASCOT that is continuously tested. Until when can you still implement changes in MASCOT's configuration?

The deadline will be during September until shortly before landing. Probably about two weeks before MASCOT is launched for landing. As we will be uploading more sequences it will still be possible to upload before the actual landing process begins. We did a sanity check and activated devices and subsystems. The health of the SUV is nominal as expected. Until landing, we will have two more communications with MASCOT. We design them specifically for the chosen landing site.

With Ritgo's photo from six kilometers up, the first team saw up close the place where MASCOT could land and work. What was the reaction to that?

We were finally relieved that it was not a celestial body like Comet Churyumov-Gerasimenko, on which the Philae rover landed in November 2014. At least Ryugu is smoother than Comet Churyumov-Gerasimenko. Of course, it is worrying to see the many rocks - and ask if it is not very challenging for MASCOT...

What would be the worst or most dangerous thing that could happen during the mission?

The worst glitch is if MASCOT is not separated - it just gets stuck inside hayabusa2. Or if the SUV cannot roll over on the surface of the asteroid - whether it is stuck between rocks or lands on very soft ground. These are two scenarios that everyone is afraid of, but if MASCOT is ejected and we get the first signals and know that it has already started taking measurements during the free fall - then it will be a great relief for us.

On the Hibusa 2 spaceship and the Mascott SUV

Hayabusa2 is a JAXA space mission to the near-Earth asteroid Ryugu. The German-French all-terrain vehicle found on Hibusa 2 was developed by the German Center for Aeronautics and Space (DLR) and built in close cooperation with the French space agency CNES. The scientific experiments on MASCOT were donated by the University of Astrophysics in Braunschweig, Germany. Operation and control of the MASCOT all-terrain vehicle and its experiments are carried out by the DLR with the support of CNES and constant knowledge sharing with JAXA.

At DLR's Space Systems in Bremen, the SUV was developed and tested. The Institute for Composite Structures and Adaptive Systems in Braunschweig was responsible for the stable structure of the SUV. The Institute for Robotics and Mechatronics at the Oberpfaffenhofen center developed the rocker arm, which allows the asteroid to be probed. The Institute for Planetary Science Research in Berlin contributed the MASCAM camera and the MARA radiometer. The supervision and operation of the SUV on the asteroid is done from the Space Experiment Support and Control Center at DLR in Cologne.

More of the topic in Hayadan:

• The spacecraft is Japanese, its landing computer is Israeli
• The space missions of 2018: from the world's most powerful launcher to the successor to the Kepler space telescope
• This morning, Japan launched the Yabusa-2 spacecraft to a near-Earth asteroid
• Vigilance for the inspection of the cargo brought by the spacecraft Yabusa (1) from the asteroid Itokawa