Once the surroundings of the lava tube entry hole are mapped, a convenient approach to the skylight is planned and all systems move towards the rim of the skylight. REU-3 is equipped with a deployable ballistic Payload Cube. The cube is deployed into the skylight by a mechanical deployment device (“propeller”). On the Moon, due to the low lunar gravity, the cube will drop at a relatively low speed and will be able to log data for a high-resolution image of the walls and the skylight floor with its on-board cameras and an integrated lighting device. In the analogue mission, the drop will be faster and thus the data recovered somewhat less detailed.

Before the deployment, the three REUs position themselves around the rim of the skylight and track the Payload Cube in-flight using their on-board sensors and the markers and light source of the Payload Cube. The sensor data are merged on REU-1 and used to create a precise trajectory analysis of the cube’s flight. The ADRES uses this data together with the data collected by the Payload Cube itself to compute a preliminary 3-D representation of the skylight. This representation is transmitted to the RMS.

The ADRES is able to select a feasible starting point for the exploration, and REU-1 and REU-2 move into position. REU-3 takes a position at the opposite side of the skylight. Its task is to monitor the descend of REU-2 in support of the coordination of the actions of REU-1 and REU-2.

REU-1 uses its manipulator arm to guide the tether and enable REU-2 to connect via the HOTDOCK interface to the Tether Management and Docking System (TMDS). The active suspension system of REU-1 can be used to lower the body of REU-1 to the ground if stable anchoring is required. Alternatively, the mobility of REU-1 can be used to establish a mobile anchor for improved mobility of REU-2. Once REU-2 is connected, REU-1 uses its arm to guide the tether in the Rapelling of REU-2 down the cliff into the skylight. The current concept for the tether/lander management foresees that the tether is stored on the lander side, i.e. on REU-2. This way, the tether can be spooled from REU-2 and tangling or rupture of the tether (when gliding over rocks) can be avoided.

On its way down, REU-2 uses its on-board illumination device to illuminate the scene and its sensors, including the GPR, to create a vertical visual profile of the cliffs, as well as a 3D reconstruction of the area it traverses.

For the exploration of the lava tube REU-2 disconnects from the tether and moves into the lava tube. REU-2 uses the GPR and the time-of-flight cameras on board to a.) create a 3-D model of the lava tube and b.) explore the consistency, porosity, and thickness of the lava tube walls. The latter is valuable information to answer the question of whether the lava tube can be sealed off and filled with an atmosphere at a later stage. In addition, if some water in the form of an ice crust is present, this will be detected.

The data from REU-2 are sent via the tether module and/or Payload Cube – which now acts as a relay beacon – to REU-1 and to the RMS. This allows to implement a redundant communication link.

After the mission in the lava tube is finished, REU-2 moves back to the tether and re-docks to the tether/lander unit. As energy can be sent from REU-1 through the cable, REU-2 may re-charge and thus effectively stay in the lava tube as a “resident rover” able to explore for an extended period of time. Alternatively, it may be lifted out of the lava tube with the help of REU-1. In the analogue mission, the latter will be demonstrated (3 times).

In this project, we will develop the concept of a re-docking interface based on HOTDOCK that is integrated into a lander/tether management unit and rappelled down into the Skylight with REU-2. In a real lunar (or even Martian) mission, the weight of this unit plus REU-2 would be manageable by REU-1 without a problem as a result of the lower gravity. In the analogue mission, we will apply extreme light-weight construction so that it can be handled by REU-1 (SherpaTT). With the exploration of a lava tube described above, the CoRob-X mission tackles one of the most difficult and complex, yet scientifically most rewarding challenges for robotic exploration. The mission scenario in CoRob-X is targeted for lunar exploration, but it is – with slightly altered system parameters due to the different gravity and atmospheric conditions – in principle also valid for the exploration of lava tubes or cliffs/canyons on Mars. In addition, if the ADRES can handle the entry of a rover into a lava tube via the skylight, it can also handle the descend into any lunar or Martian crater.

Finally weekend! Although this didn’t make a big difference for the CoRob-X team. Too many lines of software code to be optimized, motors and robot legs to be fixed, and tests to be run. Each minute of a field test like this one is precious, so that, after having recovered from the Friday-night BBQ, most team members put in another full day of work on Saturday.  

The DFKI team struggled to optimize the deployment of the Tether Management and Docking System (TMDS) and the deployment and re-docking of Coyote III. Both functionalities are needed for Mission Phases three and four, respectively. Meanwhile, Magellium, Space Applications, GMV, and UMS worked on some final bug-fixing and optimization of the software that allows our robots to become autonomous.

Tom and Tobi used the opportunity to make videos of the robots in action and to document life and work in the camp.  

On Saturday afternoon, two visitors from Dresden University in Germany joined the team. University Dresden is partnering with LATMOS on the development of the WISDOM Ground Penetrating Radar (GPR) for ESAs ExoMars mission. They were on the island already and seized the opportunity to do some testing of the radar in the vicinity of a real lava tube.  

Unfortunately, as GPRs do not work well in wet soil, they didn’t pick the best day for their experiments. Around noon and completely out of the blue, a heavy thunderstorm hit Lanzarote. Heavy rains accompanied by a severe hailstorm turned dry creeks into raging torrents and parts of the island into a snow-packed winter landscape. Fortunately, the test site was spared from serious damage and from thunderbolts.        

On Sunday, the day after the storm, the weather was bright and warm as ever and at least some members of the team could take parts of the day off to enjoy the beauties of the island, such as Timanfaya National Park and the famous Playa Famara.   

Today we had another excellent day in our field test campaign on Lanzarote. We started the day with perfect weather conditions and were able to continue the experiments from yesterday straight away.

In the morning, our colleagues from LATMOS went to the cave to perform more tests for mission phase four and additional data collection for the WISDOM GPR. Together with Tobi and Christopher, I (Tom) prepared the area around the Skylight, and we shot some footage for the project video on autonomous cave exploration after the LATMOS team was done with their experiments.   

We ended the second field test week with an absolute highlight: autonomous exploration in the first mission phase was fully achieved today and demonstrated with LUVMI-X and SherpaTT. The colleagues from GMV, DFKI, Space Applications and Magellium were incredibly proud to have completed this complex mission scenario.   

The plan for the final chapter of our field trials on Lanzarote is to enhance mission phases three (rappel maneuver) and four (cave exploration) within the next week and demonstrate all four mission phases to our VIP guests.   

Tonight, we are going to have another barbecue in the apartments where the DFKI team is staying and meet up with all the people who arrived after last weekend's great party. During the weekend we plan to record more footage for the CoRob-X mission video and work on the TMDS mission.

The sandstorm that started yesterday continued today and we could hardly see the sea or the sun. Nevertheless, it was mild weather, and we were able to continue our test campaign – space rovers have to cope with even harsher conditions than the "Calima".  

Our camp morale is at an all-time high thanks to the neighbor's dog, who seems very interested in space robotics, experiments (and of course our lunch). His curiosity is justified, as we made some great progress today.  

LATMOS conducted more experiments with Coyote III and the GPR. After burying metallic nodes in the ground, they were able to generate the first relevant data sets. Coyote III will soon be ready to join the first mission phase scenario.  

LUVMI-X had a special mission today. Space Applications and Magellium conducted some preliminary experiments for the second mission phase. After some autonomous exploration at the Skylight, LUMVI-X was positioned close to the crater and processed data generated by the sensor cube that was roped into the hole by our dedicated colleagues. We captured some great images in the process.

SherpaTT and the avionics box also worked great today and DFKI and GMV were pleased with the results of today's experiment day. For tomorrow, we hope that the sandstorms will be gone, and we can perform more experiments with all systems.

Depending on their qualifications and responsibilities, the weekend offered very different highlights to the CoRob-X team members: While some of us could take a break and enjoy the spectacular landscape and attractions of Lanzarote, others had to toil at the camp to fix things that got broken during the first week of field trials.

Jorge and Raquel from GMV spent long hours identifying and fixing a hardware bug in the avionics box. The pan-tilt unit for the stereo cameras would not work because a cable connection was broken. Fortunately, with the support of DFKI’s master-of-hardware, Tobi, the error could be identified and fixed. The avionics box can now again do what it is supposed to do, i.e., collect sensor data and run the software that enables SherpaTT to act autonomously.  

Another, even more serious problem was related to the robotic arm mounted on SherpaTT. After the cracks in the arm’s carbon-composite elbow could be fixed with glue, pipe-clamps, and a lot of hot air from a portable electric heater, one of the joints stopped working. Without the guidance of Sherpa’s arm, rappelling Coyote into the skylight would be very difficult if not impossible. Obviously, the team got a bit nervous and immediately started to search for and repair the error. Only after some long hours, updates of software drivers and exchange of electronics components, a very relieved DFKI repair team could convince the arm to flex its electric muscles again. Let’s hope that it stays that way until Mission Phase 3 is successfully completed.  

Overall, the weekend helped both humans and robots to recharge their batteries and assemble the energy and determination that will be needed to successfully complete the coming, second week of the Lanzarote field trials. 

We have completed the first week of the CoRob-X field trials just now. Once again, we had bad luck with the weather conditions. It rained most of the day and we couldn't get our rovers out in the field today. Our team has already gained a lot of experience, so covering the non-waterproof robots against the rain was done in no time ...   
 
We also encountered more serious problems today: During an experiment with the TMDS (Tether Management and Docking System) deployment, SherpaTT accidentally pushed the TMDS into the ground. Fortunately, we are working on loose soil and the TMDS is still intact. However, Sherpa's manipulator arm was significantly damaged and our mechanics will need to work on the arm over the next few days to make it functional again.   
 
It was not just the DFKI team that was affected by technical problems. LUVMI-X also had problems with its power supply, so that our colleagues from Space Applications could only conduct some experiments in the morning and had to spend the rest of the day with repairs. Currently, the team is waiting for a replacement part – hopefully it will arrive on Monday so they can perform further tests for the first and second mission phase.  

Today marked the official start of our field trials on Lanzarote 2023. After setting up the camp yesterday, we were able to release our three robotic exploration systems DFKI’s SherpaTT, and Coyote III as well as LUVMI-X from Space Applications. We had a rainy night, so we were forced to work on wet ground again. The wind is still strong and we are struggling with sand that is constantly blown into our tent (and our laptops ;-)).

Today the teams from Space Applications, Magellium, SINTEF and GMV joined us at the campground. After an initial check of our systems, we found that we were having some issues with SherpaTT and Coyote III regarding our network structure at the site. Some of our colleagues have decided to stay on site and work on these issues – we will report on this tomorrow.

In the evening Christopher and I (Tom) prepared dinner for the crew and brought it to the site along with a few beers :-)