Stone Aerospace

Our Biggest Day Yet

After Fleet Ops and the Antarctic Support Divers kindly rescued ARTEMIS during our previous sea ice mission run without a robot safety line, we had some long and difficult discussions about the conditions leading up to the need for rescue. Much discussion focused on an effect we had anticipated long ago, but had perhaps not placed enough importance on: the forces on the robot when a large amount of data fiber is payed out in the water. Even though the data fiber is incredibly thin, over kilometers of line currents can build up significant forces, yanking the robot this way and that, and even threatening to snap the fiber completely. ARTEMIS spools fiber out of its tail to try to isolate some of these forces, but the system is not perfect. Additionally, the robot experiences a change in buoyancy and trim as more fiber is spooled out – the fiber is designed to sink to keep it away from gnarly ice “stalactites” we feared could tangle it on the ice ceiling during proximity operations, but this means that ARTEMIS tends to nose down and float upwards as fiber is removed (since the spool is at the rear). Hints of these effects had manifested themselves in our control instabilities during the previous sea ice mission (whose “fix” led to our need for rescue), but the tricky bit is that these effects had stayed minimal up to this point because all our missions using a safety line were confined to a relatively short 1km radius of the borehole (the length of the safety line). During a true 5 km mission, these effects could be much worse, but there was no present way to know how much worse without ditching the safety line and trying it.

So we debated the dangers long and hard, but we decided the science was too valuable to not try – ARTEMIS would dive again off tether. Science is about exploring the unknown, and the unknown is risky. This is what ARTEMIS was made for.

We decided to repeat the previous failed sea ice mission because we had already proven it was possible to rescue ARTEMIS under sea ice if it became disabled or lost, whereas under the ice shelf we had a larger chance of losing the robot permanently (the ice is too thick to drill). We set ARTEMIS out on the same track as last time. The objectives: Transect 5 km north of the borehole under sea ice at a ceiling standoff of 7 meters. Gather PAR (Photosynthetically Active Radiation), sonar maps, and other biological and oceanographic data along the way. At the 1 and 3 km marks, pause and rise to the ice ceiling so that the surface team could localize ARTEMIS using the magnetic beacon and ensure navigational accuracy with a GPS fix. At 3.3 km, approach closer to the ceiling and slow down to image the underside of Big John crack at high resolution using the sonars and the up-look camera. At the 5km mark, dive to 40m depth and perform a vertical upcast to the ceiling while taking water samples for later scientific analysis. At any point, if problems arose satisfying our mission abort criteria, we would turn around and come home immediately. We had Fleet Ops and the divers on standby in case another rescue operation was needed.

ARTEMIS creates a 3D sonar point cloud map underneath Big John Crack

The journey outbound went extremely smoothly, and we had a slight tail current to the NE, so we moved along quite quickly, and our battery reserves were high. We stayed as close as we safely could to the ice ceiling to gather PAR data. Our navigation performed admirably – each time we stopped to localize using the magnetic beacon, the surface team confirmed that our navigation error was less than 0.1%. On the way out, we missed Big John Crack because it looked underwhelming (the platelet ice had filled it in from below), so we drove past it thinking it was a smaller, less interesting crack. On the way back we did a good job of imaging it with our cameras and mapping it at high resolution with our sonars. We are very excited to analyze all the data in more detail.

Once we turned around, many of our fears about the fiber forces were confirmed. The robot started having control difficulties, so I took over driving manually with the joystick (an Xbox controller) as a precaution. At about 3km from home, things started getting really difficult to control because of fiber forces and buoyancy changes. The fiber tension on the surface was getting tighter and tighter, so we knew that the current/drag forces had gotten large enough that ARTEMIS was still spooling fiber during the return leg, instead of pulling back the fiber payed out on the outbound leg. We also knew that it was only a matter of time until this force became strong enough to snap the fiber. Next time, we should have fiber spoolers on both the surface and the robot. Finally, although it was fighting me the whole way, I was able to bring the robot back home and dock it to the docking bar, and we pulled it up the borehole with a great collective sigh of relief. No rescue needed this time. It was definitely the most stressful video game I have ever played… We cut the fiber on the robot side because it had too much tension to recover it, and a few minutes later, the surface side snapped of its own accord. Post-mission analysis showed that we had spooled out 12.6km kilometers for our 5km out-and-back run.

But we did the science we wanted, and we got the robot back. Definitely a success.

Reporting by Evan Clark

Aerial View Of SIMPLE Camp

SIMPLE camp as seen from a USAP helicopter. (photo: Peter Doran)

I was delighted to receive an aerial photograph of SIMPLE camp recently from Peter Doran. In addition to his work on the SIMPLE project, Peter does research in the dry valleys to the Northwest of McMurdo. He was able to spot SIMPLE camp and take this photo from a USAP helicopter while returning from the dry valleys.

The photo shows the big blue bot house, the yellow galley tent, the grid of sleeping tents, two black outhouses, the orange fish hut, and various equipment crates. A Pisten Bully can be seen on parked next to the main generator on the left, while two snow machines are parked at center. The ice shelf transition is barely visible, running close to horizontal through the top half of the frame. Faint vehicle tracks cross from camp up onto the ice shelf through a flagged “stargate”, visible as a few dark spots.

Here are photos of the ice shelf stargate and tent rows that I took a few weeks ago.

A flagged “stargate” marks a safe spot for us to cross the transition from sea ice to the ice shelf. Our tracking teams use the stargate every time ARTEMIS goes beneath the ice shelf. (photo: Peter Kimball)

The SIMPLE camp tents sit in a neat grid. (photo: Peter Kimball)

Reporting by Peter Kimball

Ups and Downs

Well, a crazy work schedule and poor internet connection have made this post rather late. It has been an eventful past few days. Our operations have been smoothing themselves out, and by last Monday, we finally had successfully performed the tests we’d set to say the ARTEMIS was ready to venture out beyond a 1 km radius of the borehole. The under-ice environment was scouted, we had worked out the kinks in our launch and recovery operations through the sea ice, figured out how to run long missions and get the desired science and engineering data, and worked through several bugs and issues with sensors and systems in the under-ice environment in the McMurdo Sound.

ARTEMIS dives away from the borehole to begin a mission in this view from our real-time sonar data visualizer. A skeleton depiction of ARTEMIS is in grey in the center, mapped portions of the ice ceiling show up in red, the docking bar assembly can be seen in orange towards the right with a part of the borehole culvert extending up above it. (image: Kristof Richmond)

So we decided to make a long run under the sea ice as a rehearsal for under-shelf runs. This way, if anything went wrong, we’d have a chance of getting through the ice to pull ARTEMIS out. And we’d be able to gather some unique data on the sea ice environment to boot.

We were fortunate to have Michelle from the PolarTReC program to join us and help document the day (she even helped us out with robot operations and cooked a mean pesto pasta—thanks Michelle!). Check out her blog to learn more about PolarTReC and Michelle’s journalling on the impacts humans are having on Antarctica.

Launch and mission initialization went quite well. We began the long transect under the sea ice north of the bot house. Everything going quite smoothly, but we detected that ARTEMIS was not controlling its trajectory as well as it had been on previous missions–likely due to the removal of some ballast weight to ensure it would float up against the ice ceiling in case something went wrong and some last minute tweaking on the vehicle hull to try to reduce drag. I attempted to send some commands to adjust parameters in the vehicle control system, and inadvertently triggered a previously-undiscovered bug that ultimately resulted in voltage spikes on the power system, bringing down the main vehicle processors. We were able to receive data from vehicle subsystems (cameras and the like), but could not get the main processor to respond, leaving ARTEMIS without a way to gather navigation information or actuate the thrusters.

However, we had a back-up plan in place for precisely such an occasion: we were intentionally under the thinner sea ice (still 4 m thick), and had Mel and the reed drill, as well as the McMurdo divers Rob and Steve on standby. Brian was out tracking the vehicle and was able to quickly localize the magnetic beacon when it came on in emergency mode, and we hand-drilled a small hole to put a camera down and found ARTEMIS only a few meters away. Mel was soon on the scene and drilled out an access hole, and soon after Rob went in with a safety line and hooked ARTEMIS.

In a surprisingly short amount of time (only a few hours), ARTEMIS went from being stranded under the ice to back warm and safe in the bot house. The bug that triggered the power fault was fixed, and several other improvements to the system identified. We will need one more run on our safety line to validate these fixes, but then are aiming for the ice shelf, which is too thick for anyone to drill through and rescue the vehicle. But that is what we came here for: to explore the unknown.

Time Flies

Well, we haven’t been updating much since Justin and Peter (and his beautiful photography equipment) left. We are working hard with reduced personnel. It is hard to believe, but I am leaving in two days as well. In the meantime, I thought I’d share some cell-phone snapshots of the activities around here.

We did have a bit of a break over the weekend, when McMurdo takes two days off (instead of the standard one day per week) to celebrate Thanksgiving. We have been working almost non-stop for several weeks in a row, and decided it was time for the team to relax for a day as well.

We all showed up in the evening to the town Thanksgiving feast. Most people here are far from family, and really go all out to make the celebration special. The galley went all out to make the day happen, even flying in fresh strawberries for dessert.

​Early the next day, a few of us headed out to the observation tube (see Peter’s earlier post) just outside town and crawled down to take in the serenity and beauty of the ice underside that ARTEMIS experiences every time its out.

Our time on the ice is short, and we are pushing to get as many missions as possible in before the beautiful weather makes moving equipment on the ice unsafe. The team will be working hard for the remaining time here.

Reporting by Kristof Richmond

Scenes From Under the Ice

The environment beneath the ice in McMurdo Sound is other-worldly. Literally. That’s part of the reason we are studying it – because it provides one of the best terrestrial analogs to what things might be like on Europa. ARTEMIS has 3 active cameras on board, and has been busy capturing scenes of the world below during our missions. Some of these scenes are incredibly beautiful – I can now understand why Antarctic divers reverently call going beneath the ice “entering The Cathedral.”

ARTEMIS flies under a school of fish while gazing up at the ice ceiling. It’s amazing how the world below the ice can be so alien, and yet so the same – the fish look like birds underneath a bank of clouds.

ARTEMIS approaches a sizable jellyfish which swam past our borehole.

Reporting by Evan Clark