Images Transmitted Today:
 
Part of the team flew to Pirrit Hills to find good future meteorite search sites.
 
Flying over Pirrit Hills
 
These are three digital camera photographs of a meteorite found at the nearby Martin Hills.
 

Nomad traversing.
 
Nomad traversed through whiteout conditions

These images show Nomad having problems with a few rocky areas:
 

Nomad's sensors were inspected to test their robustness under cold conditions. Additionally, Nomad's spectrometer had to be installed after the robot was sent to the Patriot Hills. Below are images of Nomad's sensor installation and testing.
 
Fogged hi-res camera Nomad's sensor mast
Installing the spectrometer
 
Some images of the various sites.
 
The main camp site The endurance tent
White out conditions at the main camp site The skidoo
A regelation porthole (rock melted into the ice) The camp site following Nomad's traverse

Finally, some images of the expedition team.
 
 

Steering Mechanism Defect Report from Michael Parris

During stowage of the Nomad chassis in the FACH hangar at Punta Arenas, the left rear wheel caught in a rough patch in the floor, causing the left rear steering rack to skip teeth with respect to the pinion gear. The rough patch was most likely the result thermal cycle spawling of the concrete floor. When the wheel caught, Mark Sibenac heard a noise from the wheel. He immediately released the enable button on the joystick, disengaging the drive motors. Mark alerted me to the problem he was having. After brief visual inspection, we continued to stow the chassis. Again, we heard a popping noise. It sounded like gears skipping. I inspected the steering motor mounting bracket and verified that the bolts were tight. This motor mount had loosened previously, allowing slippage of the gears. We noted no visible damage so we continued to stow the chassis. We again heard the noise. It seemed to have originated in the internal steering assembly, near the gearbox and steering racks. At this point we jacked up the left side of Nomad to assist in the stowage process. As the chassis approached the stowed position, I noted an inequality in the angular positions of the left front and left rear steering assemblies. The left front wheel had reached the full stowed position. The left front steering linkage bar had contacted the limit switch disabling the steer motor. The left rear wheel had not reached the full stowed position. It had stopped about 10 degrees short. The left rear steering rack appeared to have skipped teeth with respect to the pinion gear.

We deployed the left side of the chassis once again to inspect the steering racks, and gearbox. I counted exposed teeth on the racks to conclude that three teeth had been skipped on the rear rack. Both the racks and pinion gears appeared to be in good condition, i.e. no chipped teeth or visible cracks. All other components of the left steer assembly appeared to be in good condition as well. A slight misalignment of the wheels when in the deployed position was visible. This misalignment was not nearly as great as in the stowed position. When the left front wheel is aligned straight with respect to the body of the robot, the left rear wheel is misaligned by a 2 or 3 degree counterclockwise rotation.

I assessed the prospects of repair to the steering mechanism to realign the gear racks. We had not yet received confirmation of our departure to the ice, but FACH had requested that our equipment be packed and ready for loading by 19:30 that evening. This incident occurred at 18:30. I did not feel that we would be able to complete the repair within an hour. We speculated that the misalignment would not have great impact on our primary operations at Patriot Hills. Rather than risk missing our flight opportunity, we decided to leave Nomad as is. We could perhaps realign the racks, if necessary, after our arrival and set up of the work tent. After some discussion with Mark and Alex, we decided to transport Nomad in the deployed position on the C-130 to Patriot Hills. We had previously agreed to have Nomad fully assembled and functional for a wireless rollout at Patriot Hills. This was for reason of spectacle as much as logistics. Nomad had been fully assembled and tested at the FACH hangar prior to this incident. Late that night, we drove Nomad from the hangar and backed it onto the C-130. Upon arrival at Patriot Hills, Nomad rolled out of the C-130 and drove under wireless teleoperation around the aircraft loading area.

Since then, Nomad has driven nearly 15km (my estimate) without any major mechanical problems. The major implication of this misalignment is the inability to completely stow the chassis. Other implications would include:
  1. Inability to properly calibrate the alignment of the steering mechanism. Nomad requires manual calibration of the steering mechanism to align the four wheels in the straight position with respect to the body of the robot. This calibrated position is preset into the encoder registers in the real time cage. The manual calibration process involves a spotter at the robot relaying commands to an operator. This calibration is based on the spotter's visual verification that the wheels are aligned. As a result of this incident, the left wheels do not properly align. The longitudinal alignment of the front and real wheels does not coincide with the longitudinal axis of the body of the robot. The best we can do is to align the left front wheel with the body of the robot, in which case the left rear wheel is misaligned by a measured 3.5 degrees. Or alternatively, split the difference by having both the front and rear wheels slightly off in opposite directions. The latter alignment method allows the robot to drive a straight when commanded. We have verified this through plotting of the gps position data.
  2. Increased wear on the left wheel components due to slight but constant lateral slip. The misalignment of the left wheels induces a slight but constant lateral load on the wheel components. This lateral load could, over time, lead to increased wear of the components. On November 8, Stewart reported a noise coming from the left side of the robot. I went out to inspect and found that the noise had come from inside the left rear wheel. Again, this noise sounded like slipping gears. I removed the hubcap to find that the motor mount bolts had loosened, allowing separation and slip between the drive gears. The loosening of these bolts is a recurring problem. We had experienced this throughout the Atacama Desert Trek. We had implemented a temporary fix in the atacama by sandwiching the motor mount to the axle with steel plates and long bolts. We had redesigned the mounting assembly based on last year's fix. Since then, we have experienced the loosening of the motor mount bolts, but normally attributed it to assembly error, rather than wear. This occurrence may have been due to the misalignment, but it is my sense that it was not. I will continue to monitor the wear of the drive assembly.
  3. Increased power consumption in the left drive motors (or all drive motors). Another possible implication of the misalignment of the left wheels is an increase in power consumption. Preliminary locomotion test results show increased power draw to the left wheels of the robot. It is too early to make any claims. I will investigate this further. Conclusion: The misalignment of the left wheels due to a steering gear rack slippage does not have significant impact in the operations of the robot. Most driving modes, explicit steer, deployed skid steer, and point turn, function normally. Stowed skid steer driving is probably possible, but not advisable due to the increased angular misalignment of the wheels in the stowed position. It is unlikely that any repair attempt will be made before return to Pittsburgh.

Expedition Report from William Cassidy

23. Nov. 18, 1998, Wednesday: Patriot Hills Camp

Moderately windy today, but the temperature seems a little higher.

Almost since they arrived, the Chileans have been searching north of their camp for all of their equipment that blew away in the chaotic first days here. Today they found a lot of stuff about 8 km away, and among this debris was one end of our Polarhaven shelter. So now we have the complete frame and one end. This gives us hope that we will find more during our remaining days here. This testifies again to the force of the winds here during the Antarctic winter. The Polarhaven was stowed in three heavy canvas bags, and these were stored in a large shipping crate. This package was judged to be the most massive of all the boxes we left in the cache, and was positioned in the upwind direction under the assumption that it would shield all the other stuff. The crate must have come apart, exposing the three bags inside. The bag containing the frame only traveled 25-30 feet, and was recovered intact. The bag containing the endpiece that we just recovered must have actually ripped open, scattering its contents over the landscape. Assuming the other bag remains intact, it is probably somewhere between the cache and the point where the endpiece was found.

Matt started Nomad at 10:15 a.m. Stewart and Nicolas went out to it around noon. Stewart will drive it up to Camp Crickett, where Liam will give its spectrometer a quick test to see how it is working. Lots of blowing snow during the afternoon.

We had an all-hands conference tonight in the Endurance tent to decide on our agenda for the next few days. Nomad is at Camp Crickett and Liam plans to run his baseline tests tonight, with Nomad running, but stationary. In the best of all possible outcomes, he will establish an array of rocks and meteorites, collect spectroscopic data on them and confirm that the spectrometer, now mounted on the robot, is functioning as planned. Liam left with Mike, Sib and Nicolas for Camp Crickett.

Stewart estimates that it will take a minimum of 2 days for Nomad to travel from Camp Crickett to the Independence Hills moraine, which is our next goal. He will do a Kim-type search pattern along the way. If Liam finds problems tonight that must be fixed, however, we will keep Nomad at Camp Crickett until those problems have been corrected.

Once in the valley, Nomad will be surrounded by hills and in an ideal spot for Matt to exercise the panospheric camera. He has taken two photo series and would like to get 8 more. Approaching the Independence Hills moraine, Liam will get another chance to run spectrometric measurements on rocks in situ.

The return trip, hopefully in autonomous mode, will then require a minimum of 5 days.

Liam obtained 12-13 spectra before he, Mike and Sib returned to Patriot Hillls camp around 3 a.m. He seems to be greatly pleased by the results. Among other nice things, the program classed Ralph's two "meteorwrongs" as rocks; not meteorites.