Lake Bonney Expedition 2008

The lake's currently cloudy water made photographing the glacier face practically impossible. Still, it is possible to make out vague shapes and variations in color in these two photos taken by the bot's horizontal-facing camera today.

Here is the first image from above, digitally processed to show more detail.

A parting shot of our camp a Blood Falls before we start packing up

Wednesday
December 24, 2008

Today we decided that we would use our last day of mission runs to approach the glacier face for one final time this year. While we have been able to map the glacier surface with the DeltaT over the past several days, the murky water has prevented us from taking the photographs we had hoped to mosaic and overlay onto the 3D surface map we have. Still eager to get some good images despite the poor visibility, Kristof suggested sending the bot to within a few meters of the glacier, closer than our previous stand-off distance. Maybe closer to the face we would be able to get some good images, we hoped. To minimize the risk of any bumping or snagging hazards we decided to visit a flat, uncomplicated stretch of the face that we had spotted in the sonar data from the past few missions.

Since the navigation systems lost lock the last time we approached the glacier close-up, we were cautious in our approach this time. The bot continued to function properly during the entire mission but unfortunately the poor visibility in the water thwarted our attempts to take photos, even at our closer range. The bot returned home and we pulled it out of the icy drink for the last time this year. With our last mission now completed, all that remains for us is to pack up our equipment, break down the bot house and return home to finish processing all of the data that we've collected. Goodbye Lake Bonney - we'll see you again next year!

Santas jolly elves gather around the moon pool to sing us a carol

This image is a panorama south to north across the 1 km wide glacier face. We got more than 100 million sonar hits to build the map; only about 5 million are shown here to keep the file size reasonable. In the center portion it appears that the glacier is actually floating on the lake (there is an undercut cave at the bottom that runs about 1/3 the length of the image). You can also see moraine deposits at either end. This is a 2D end-on rendering of the glacier - the data are full 3D and we will be generating some "fly through" videos with the UIC electronic visualization lab over the next month that will give life to this and to the lake chemistry data.

here is a larger version of the image

Tuesday
December 23, 2008

In this morning's group meeting we discussed the possibilities for today's mission. We determined that if we gave the bot a fairly ambitious mission plan today we might be able to get the rest of our DeltaT glacier scans done by the end of the day. We decided to go for it.

Soon after starting to go through the bot's pre-launch checklist we heard someone hail us on the helo communications channel of our radio, accompanied by the distant beat of a helo rotor coming up the valley. We had been informed that there might be visitors today, so we figured we would be giving the grand tour to some folks from McMurdo or Scott Base (New Zealand's science station on Antarctica). The helo landed outside the bot tent and the visitors came in. To our surprise, however, these were not the normal kind of visitors we had seen before. These folks were decked out in red and green, jingle bells, and Santa hats. After marching into the Bot House and singing us a Christmas carol or two they presented us with gifts. The boxes contained the best thing you could bring to a bunch of researchers working on a frozen lake for over a month: food. There were fresh baked cookies, bread, and candies and, one of the most valuable and rare things in you can wish for here in Antarctica, fresh fruit.

Our jolly visitors departed, off to spread cheer to the other field camps, and we munched some cookies and got back to work. We completed the checklist and sent the bot on its way. There were no snags today and the bot succeeded in doing a continuous sonar sweep of the remaining glacier face. Chris took the bot's trip home as a chance to experiment with running the vehicle at higher speeds to find the most power-efficient speed. We took the bot up to a whopping .25 meters per second!

This panorama shows the complex surface of the Taylor Glacier face on the surface. In a few days we'll learn what it looks like underwater, too.

Monday
December 22, 2008

Today we continued our glacier exploration, this time doing a combination sonde drop and glacier-mapping run in the southernmost area of the glacier face. The mission plan took us first to the delta south of the glacier face where we did a few bonus sonde drops in the shallow waters there. Mission control had to do a little bit of maneuvering to avoid some underwater moraines.

From the southern delta, the bot traveled north along the glacier, scanning it with the DeltaT sonar. Things went smoothly until Leah reported that the fiber was feeding out, not in, meaning that the bot was snagged. We managed to unsnag by diving the bot down and then moving to the side to get out of the snag zone before continuing. As the bot proceeded to head home after that it snagged again and this time the diving trick didn't work. Instead, mission control directed the bot to back up past where, calculated from the distance markings on the fiber, they estimated the snag to be. After backing up, we tried diving again and managed to free the bot. Even with the extra time and battery power this delay consumed, the bot returned home after the six and a half hour mission. Now we have some great 3D data from the southern edge of the glacier face. Our job over the next few days will be to continue scanning the north end of the face.

As the weather get warmer, the lake ice gets rougher and rougher. This makes tracking a slower process

A screenshot of the visualizer program that shows us where the sonars are getting hits

Sunday
December 21, 2008

Recovered and ready to try another approach to the glacier face we sent the bot to the middle section of the glacier face, just south of our run on Friday. This would take the bot into the iceberg zone so the plan was to stop the vehicle periodically and do a sonar sweep to look for the subsurface portion of the icebergs. If we could, we would drive the bot into the channel between the glacier face and the icebergs.

To our surprise, the sonar scans showed nothing under the ice in the area where icebergs stood 2 meters high on the surface. It would seem that either the warm water entering the lake near the glacier has melted the subsurface portion of the bergs or that the surface bergs were formed ice that spalled off the glacier face never broke the surface of the lake ice in the first place. In any case, we were happy that this hypothesized snag hazard didn't exist.

The water continues to be murky so we were unable to take any visual images of the glacier but we racked up a ton of sonar data on the glacier face. With today's data and the data from our first glacier mission combined, we have mapped half of the glacier face so far.

Saturday
December 20, 2008

Today we took a day off.

The HID lights, forward camera, and DeltaT sonar were all placed on the front of the vehicle for the glacier mapping missions

This is a screenshot of the live feedback from the DeltaT sonar. It shows a profile view of the glacier face at this point. The top horizontal stretch is the ice at the lake surface, below that, the glacier wall starts as a curve on the left, the middle point is a ledge jutting out and below that the wall recedes again. Mission control found this pattern common

The forward camera took this image of the ice ledge the bot bumped into near the glacier

Water has started gushing out of a 3 meter wide hole in the glacier face. The waterfall is about 10 meters high

The visibility in the water has suddenly dropped from almost unlimited to almost 30 cm

Friday
December 19, 2008

Today we shifted gears from running sonde drops at grid points to mapping the face of the Taylor Glacier. The glacier ends at the head of West Lobe Bonney and the face of it extends down below the surface of the lake. Peter is interested in getting a 3D sonar map and, if possible, photos of the underwater glacier face.

We spent the morning re-arranging some of the sensors on the vehicle. During the profiler missions we had our multibeam “DeltaT” sonar facing downwards to map the lake floor as we went from point to point. For the glacier missions, we want the DeltaT to face the vertical glacier wall, so we mounted it sideways on the front of the vehicle. We also moved the horizontal camera and HID lights to face the same direction as the DeltaT, also on the front of the bot; previously they faced out from the aft direction of the vehicle to help us avoid obstacles as we drove the sonde from point to point.

We were worried that we would snag the fiber close to the glacier because the lake ice is somewhat broken up there and there are large icebergs sticking up out of the lake ice. Trying to avoid this, we drafted a mission plan where we would drive up to the glacier face, spin the vehicle slowly to get a sonar scan and then retreat along the same line we approached on. Then we would move sideways 25 meters, approach, scan, and retreat again. The resulting mission plan looked like a dinner fork, where each tine was an approach and retreat. It was not an efficient use of battery power but we hoped it would keep the bot from looping the fiber optic line around any obstacles out there. The northernmost section of the glacier face looked the most straightforward and hazard - free so we decided to start there.

We started to run the mission and as the bot approached the glacier, it became evident that somehow either the data on the mission plan map or in the bot’s navigation was incorrect. The coordinates that should have had the bot right against the glacier actually left the bot about 20 meters short of it. Bill and Vickie, who had been tracking the bot, hopped on the ATV to drive back to the Bot House and draft some extended coordinates. However, in the last few days, thanks to the warm weather we’ve been enjoying, the surface of the lake ice has morphed dramatically and the ATV got stuck in a water-filled ditch on the rough ice, leaving them soaked and walking back to the Bot House. Armed with an ice screw and some cargo straps, Maciej went out to retrieve the ATV as Vickie drafted new coordinates and Bill changed into dry clothes.

With the new coordinates the bot approached the glacier as originally intended and the sonar scans reported good data. Bill and Vickie continued to track the vehicle until Vickie suddenly broke through a layer of ice, getting wet to her knees, at which point they decided the ice near the glacier was too instable to follow the bot any further out.

The folks at mission control were getting enticing images from the horizontal camera so they decided to approach the face a little closer to get more footage. When they did so, the bot unexpected bumped into an ice ledge, which knocked out the readings from the DVL (Doppler Velocity Log). The DVL is a key sensor in the bot’s navigation system so if it loses lock momentarily the bot becomes entirely disoriented, even after it regains lock. So now, with the bot in a place where we could not track it, the bot didn’t know where it was. Luckily, Chris was able to watch the sonar feedback and camera images and manually drive the bot away from the wall. The programmers estimated how much the bot might have drifted before the DVL regained lock and sent the bot an estimated location and told it to navigate back to the last point flagged by the tracking team. As it approached this flag, Bill and Vickie tracked the bot and reported the error, a few meters, in the bot’s calculation of where the flag was. Mission control reset the location using this groundtruth data and sent the bot home.

To make matters even more interesting, by now the batteries were getting low and the bot was still several hundred meters from the melt hole. In addition, the visibility in the water had been decreasing all day and by this point in the mission, the water was quite murky. The warmer weather has been melting the glacier ice and there is now a waterfall blasting out a tremendous amount of water from the glacier face into the lake. Also, the flow in the Santa Fe stream next to our camp has increased. This influx of water is stirring the lake up and carrying in very fine grained sediments. The result is that the crystal clear water we saw this morning is now a milky stew. The loss of visibility means that the visual homing program, where the bot follows a blinking light up the melt hole does not work because it is not be able to see the light.

Exhausted from the stressful mission, we resorted to our recovery strategy of tugging the bot in by its tether. We navigated to within a few meters of the melt hole and then Kristof slowly and carefully pulled the fiber optic line. To everyone’s relief, we soon saw a dark shadow rising up through the murk. In a few seconds the shadow became an orange blob and then the bot was home.

Upon closer inspection we were happy to find that the bot suffered no major damage from its bump into the wall. The DVL bumped the ice shelf directly but none of the sonar transducers on it were scratched and the HID light mounted just to the left of the DVL had been bumped and was aiming upward but it was not even dented.

Despite the chaos today, we had a successful mission. We navigated to the glacier face for the first time, got a lot of sonar data and images, and navigated home. A few more data collection runs from the glacier face and we will have accomplished our objectives here at Lake Bonney.

Vickie poses next to Potato Rock on the north shore of West Lobe Lake Bonney. It is rocks like this that had us worried about bringing the bot close to shore in this area of the lake

The sonde camera took this image of a large rock near the north shore, it was about 2 meters tall. We avoided this obstacle and happily didn’t find any others

Our status at the end of Mission 7. We have hit all of our sonde targets for this year!

Thursday
December 18, 2008

Mission 7. While yesterday’s mission was pretty long and took us far from home, the plan for Mission 7 was even more aggressive today — 1730 meters long, and again about 700 meters straightline distance from the Bot House. Also we would be operating close to shore again. The north shore of the lake is a steep talus slope that tops out in a large cliff face about 600 meters vertical distance above the lake. This slope is littered with huge boulders and it seemed quite likely that the slope under the ice would have some big rocks, too, hazards for the bot. So, just like the start of every mission, we had some reasons to be a little nervous.

We topped the batteries off, dropped the bot in the water and started off. Vickie and Bill tracked the bot as it traveled between sonde points. The phono plug on one of the beacon receiver headsets broke about halfway through the mission and since time is of the essence with these longer missions, Kristof hopped on the ATV and raced out to the tracking team to give them a replacement headset so that there would be no delay in locating the bot.

As the bot approached the north shore in the second half of the mission, mission control kept a close watch on the water depth and the obstacle avoidance sonars. As predicted, we encountered a large rock on the bottom that was big enough to halt our progress to shore. We did the sonde drop from the safe point we stopped at and then proceeded parallel to the shore line, approaching more closely once we passed the rock.

In no time the bot had run through the remaining sonde points without further incident. On the 350 meter journey back to the Bot House, we ran the bot on a course parallel to and 30 meters offset from the path it took out in the morning. This provides us with a patch test for the multibeam sonar, basically calibration data we can use when we post-process the sonar data.

The bot made it home safe and sound. With the exception of a couple of sonde points we might grab later when we are running missions to the glacier face, we are done with all of our 2008 sonde point targets; we have succeeded with a large part of our job here this year and our spirits are high today. Tomorrow we start on another objective: mapping the glacier face.

Just before launch, Maciek leans out over the bot to remove as small chunk of syntactic that has broken off and become stuck in the mesh above one of the vertical thrusters

With the batteries back on charge after our aborted launch, Bill works on adjusting the bot’s buoyancy for round two of today’s mission

Bill tracks the bot’s radio beacon with a loop antenna while pulling a sled with the flags and kovacs drill needed to mark the sonde drop points

Bill drills a hole in the ice for the bamboo pole that will flag this sonde drop point

Our status at the end of Mission 6. The grid is almost done

Thursday
December 17, 2008

Now that we have our act together on these profiler missions, it is time to do the riskier missions. In our previous missions we have picked off almost all of the nearby, easy grid points and now we have to go further out. The mission plan for today was a 1620 meter long loop, with 11 grid points. It’s the farthest distance we’ve planned to traverse, by over 100 meters. According to Bart’s mission planning worksheet, it cuts into our reserve battery power. We decided that if we are very efficient with our launch procedure, we should have enough battery power to run the mission safely. The second concern is the sheer straight-line distance from the Bot House to the furthest point on the plan, 704 meters. If the fiber gets caught that far out, we don’t have enough fiber to drive it all the way back still connected. Everything needed to go right today.

We got off to a good start, getting the bot into the water quickly. The buoyancy, which mysteriously changes a little bit from day to day, was adjusted and looked good. Just before diving the bot down to the bottom of the melt hole, we noticed a small white object in the vertical thruster mesh. Since we didn’t want this foreign object to interfere with the thruster, Maciek got into a harness and leaned out over the bot to pick the object out of the mesh, it was a small chunk of syntactic that must have broken off. We took the bot down under the ice, went through the rest of our launch checklist and the bot started off to the first point for the day. When it got there, the ice-picking maneuver, where the thrusters turn off and the bot floats up to rest against the ice ceiling, didn’t work. With the thrusters off the bot was slowly sinking instead of rising. Somehow, the buoyancy was off. Given our tight battery budget for the mission we could not afford to keep the thrusters on to hold the bot against the ceiling, nor could we dally, find some other solution and then continue on the mission. The only choice was to go straight back home, take some lead off the bot and then recharge the batteries to full capacity and start the mission over.

The bot’s buoyancy in Lake Bonney has consistently been a bit of a pain. One would think that if we could get the buoyancy just right one day then, with no changes to the ballast or the bot, the buoyancy should be the same the next day, but that has not been the case. There are probably several factors in play here, the bot’s temperature when it goes in the water, the water temperature and density in different parts of the lake, microbubbles and so on. For this reason, we’ve been in the habit of checking the ice-picking maneuver right at the beginning of every mission, just beyond the melt hole. Today the ice-picking worked during the launch check but wasn’t working at the grid point. We couldn’t establish a cause for this problem so we decided to just deal with the situation by removing two pounds of lead.

After we had charged the batteries for a few hours we were back to full charge and ready for Take Two of our mission. This time we were able to launch the vehicle in even less time and in a flash we were cruising back out to the first grid point on our mission plan.

This time the bot ice-picked normally, we did the sonde drop and were off to the next point. By this time in our field season here, all of our repetitive tasks have become second nature. Chris, Shilpa and Kristof are able to do sonde drops more efficiently now and Bill and Vickie have no trouble keeping up while tracking the bot and flagging the sonde drop points.

On the return leg of the loop there was a moment of concern when the fiber appeared to be caught but a short dive with the bot cleared up this problem. When the bot returned to the Bot House, we still had several amp hours of battery life left, more than we expected. What’s more, today the bot went as far away from the melt hole as it will go in Lake Bonney and it returned home successfully.

Blog entries from previous weeks can be found below:

Week 1 - Nov 26, 2008 - December 2, 2008

Week 2 - Dec 3, 2008 - December 9, 2008

Week 3 - Dec 10, 2008 - December 16, 2008

Personnel:

Dr. Peter Doran is the Principal Investigator for the Endurance project. He has been studying the lakes in the Antarctic Dry Valleys for 15 years and is a professor at the University of Illinois, Chicago.

Dr. Bill Stone is a Co-Investigator for Endurance. He is also the president and CEO of Stone Aerospace, the engineering company that designed and built the Endurance vehicle.

Dr. John Priscu is a Co-Investigator from the University of Montana. He has been studying the lakes in the Antarctic Dry Valleys for over 20 years.

Bart Hogan is a mechanical engineer for Stone Aerospace.

Dr. Kristof Richmond is a programmer for Stone Aerospace, focusing on navigation.

Shilpa Gulati is a programmer for Stone Aerospace, focusing on the system executive and machine vision. She is also a PhD student at University of Texas, Austin.

Chris Flesher is the vehicle manager, programmer, and electronics technician for Stone Aerospace. He is a Masters student at UT Austin.

Bob Kenworthy is an electronics technician for Stone Aerospace.

Vickie Siegel is chief vehicle technician and logistics manager for Stone Aerospace.

Maciek Obryk is a graduate student at the University of Illinois at Chicago.

Annika Taylor is a Masters student at at the University of Illinois at Chicago.