Atacama III: meteorite search during the Nomad field tests: perspectives on automated field operations by teleoperated vehicles in extreme environments. Cabrol, N. A., Chong-Diaz, G., Dohm, J. M., Arredondo, M., Dunfield, G., Gulick, V. C., Jensen-Iglesia, A., Keaten, R., Lamelli, C., Landheim, R., Lee, P., Pederson, L., Roush, T., Schwehr, K., Stoker, C. R., & Zent, A. In Lunar and Planetary Institute Conference Abstracts, 1998.
Atacama III: meteorite search during the Nomad field tests: perspectives on automated field operations by teleoperated vehicles in extreme environments [pdf]Paper  abstract   bibtex   
Exploring ways to use automated vehicles to search for meteorites in extreme environments was one of the components of the 1997 Nomad Field Experiment. The purpose of this operation was to test visual and instrumental methods that will help to identify meteorites, and to explore new strategies that could benefit the meteorite search program in regions were sustaining the human presence is associated with risks. The rover located in the Atacama desert, Chile [1], was remotely operated from the NASA Ames Research Center. Two different types of operations were planned: (1) a visual search, using the imaging system onboard Nomad of meteorites planted on the field, (2) an instrumental search, using a magnetometer (see figure below). Fig.: The sensor was pulled behind Nomad, a position which proved not being optimal for a precise localization of the suspected meteorites. The presence of the panospheric camera minimized the inconvenience by enabling the Science Team to look backward. Rover Search Equipment: For the search in visual mode, the Science Team was using the rover imagery system capabilities [1], including the panospheric, stereo- color, stereo black and white, and close-up cameras. For the instrumental mode, Nomad was equipped with a towed sensor sled, with the following specifications: (a) Sled: about 15 cm thick 0.30 x 0.30 m HDPE (non metallic) sliding platform with a 2.40 m towbar, attached to the rear of Nomad, 0.9 m lip around front and side to surmount obstacles, (b) JW Fisher Pulse 8x metal, 0.20 m diameter search coil in the center of the platform. The sensitivy varied depending on the size and composition of the target, and was particularly sensitive to iron, (c) Two applied Physics Systems 3 axis magnetometers. The FSD was 1/6th of the earth field. They were mounted on post at the rear of the sled, behind the metal detector. One was mounted 10 cm from the ground (search sensor), and the other was about 5 cm up (reference sensor). The data were processed onboard the rover. The positioning of the sensor at the rear of the rover induced specific maneuver constraints that led the Science Team to recommend the sensor setting on the front of the vehicle for future operations. For instance, backward maneuvers were to be avoided, and the rover could not execute prolonged tight (inferior to 5-m radius) turns, as the towbar could have been snagged by the wheel. The Visual Search Strategy: The operation was limited to a 500 m2 area, in which three meteorites had been planted randomly. The number, size, composition, and position of the meteorites were not known by the Science Team at NASA Ames. Without this information, the strategy used was to try first to characterize the local geology in order to identify the meteorites, (i.e., by they morphology, texture, color that might be different from local rocks). The geology and morphology were, thus, analyzed in the surroundings of the search area, and also jointly during the search operation as the rover was moving along. The local geology at the base of the hills (see figure) was defined as colluvial and alluvial material. [2] Then, the Science Team decided to conduct the meteorite search following the standard strategy adopted by the US Antarctic Search for Meteorites program, ANSMET, (i.e., to perform a grid search by examining the ground in the immediate vicinity of the rover while traversing the search area in a zigzag pattern). Forward-facing high-resolution images of the ground were acquired at each stop, and every image was examined for any unusual object (i.e., morphology, geology, or texture) of resolvable size. Given the limited time available the stopping interval was relaxed to stopping only when a candidate meteorite was spotted while roving continuously. Although this approach might lead to overlooking a number of smaller-sized meteorites, this strategy was deemed preferable as it maximized the area covered in the time available, and hence, optimized chances of finding larger, easier-torecognize meteorites. Results of the Visual Search Mode: Three candidate meteorites, hereafter designated M1, M2, and M3 were encountered during the second track. The rocks were first seen in the forward direction in panoramic scenes, and then scrutinized using the close-up high-resolution color imagery, for shape, and texture characteristics. They appeared as relatively large and dark objects, contrasting with the smaller-sized, and/or lighter-colored background. M1 was revealed to be a dark-brown object, about 10 cm across, with relatively planar facets, rounded angles, and distinct thumb-sized (1-2 cm across) dimples on the facets (see figure below), suggesting the possibility of an iron-meteorite, the dimples being the reminiscent of regmaglyphs (shallow depressions characteristic of iron-meteorites, formed by erosion of their surface by turbulent vortices during atmospheric entry).
@inproceedings{ cabrol1998c,
  author = {N. A. Cabrol and G. Chong-Diaz and J. M. Dohm and M. Arredondo and G. Dunfield and V. C. Gulick and A. Jensen-Iglesia and R. Keaten and C. Lamelli and R. Landheim and P. Lee and L. Pederson and T. Roush and Kurt Schwehr and Carol R. Stoker and A. Zent},
  title = {Atacama III: meteorite search during the Nomad field tests: perspectives on automated field operations by teleoperated vehicles in extreme environments},
  abstract = {Exploring ways to use automated vehicles to search for meteorites in extreme environments was one of the components of the 1997 Nomad Field Experiment. The purpose of this operation was to test visual and instrumental methods that will help to identify meteorites, and to explore new strategies that could benefit the meteorite search program in regions were sustaining the human presence is associated with risks. The rover located in the Atacama desert, Chile [1], was remotely operated from the NASA Ames Research Center. Two different types of operations were planned: (1) a visual search, using the imaging system onboard Nomad of meteorites planted on the field, (2) an instrumental search, using a magnetometer (see figure below). Fig.: The sensor was pulled behind Nomad, a position which proved not being optimal for a precise localization of the suspected meteorites. The presence of the panospheric camera minimized the inconvenience by enabling the Science Team to look backward. Rover Search Equipment: For the search in visual mode, the Science Team was using the rover imagery system capabilities [1], including the panospheric, stereo- color, stereo black and white, and close-up cameras. For the instrumental mode, Nomad was equipped with a towed sensor sled, with the following specifications: (a) Sled: about 15 cm thick 0.30 x 0.30 m HDPE (non metallic) sliding platform with a 2.40 m towbar, attached to the rear of Nomad, 0.9 m lip around front and side to surmount obstacles, (b) JW Fisher Pulse 8x metal, 0.20 m diameter search coil in the center of the platform. The sensitivy varied depending on the size and composition of the target, and was particularly sensitive to iron, (c) Two applied Physics Systems 3 axis magnetometers. The FSD was 1/6th of the earth field. They were mounted on post at the rear of the sled, behind the metal detector. One was mounted 10 cm from the ground (search sensor), and the other was about 5 cm up (reference sensor). The data were processed onboard the rover. The positioning of the sensor at the rear of the rover induced specific maneuver constraints that led the Science Team to recommend the sensor setting on the front of the vehicle for future operations. For instance, backward maneuvers were to be avoided, and the rover could not execute prolonged tight (inferior to 5-m radius) turns, as the towbar could have been snagged by the wheel. The Visual Search Strategy: The operation was limited to a 500 m2 area, in which three meteorites had been planted randomly. The number, size, composition, and position of the meteorites were not known by the Science Team at NASA Ames. Without this information, the strategy used was to try first to characterize the local geology in order to identify the meteorites, (i.e., by they morphology, texture, color that might be different from local rocks). The geology and morphology were, thus, analyzed in the surroundings of the search area, and also jointly during the search operation as the rover was moving along. The local geology at the base of the hills (see figure) was defined as colluvial and alluvial material. [2] Then, the Science Team decided to conduct the meteorite search following the standard strategy adopted by the US Antarctic Search for Meteorites program, ANSMET, (i.e., to perform a grid search by examining the ground in the immediate vicinity of the rover while traversing the search area in a zigzag pattern). Forward-facing high-resolution images of the ground were acquired at each stop, and every image was examined for any unusual object (i.e., morphology, geology, or texture) of resolvable size. Given the limited time available the stopping interval was relaxed to stopping only when a candidate meteorite was spotted while roving continuously. Although this approach might lead to overlooking a number of smaller-sized meteorites, this strategy was deemed preferable as it maximized the area covered in the time available, and hence, optimized chances of finding larger, easier-torecognize meteorites. Results of the Visual Search Mode: Three candidate meteorites, hereafter designated M1, M2, and M3 were encountered during the second track. The rocks were first seen in the forward direction in panoramic scenes, and then scrutinized using the close-up high-resolution color imagery, for shape, and texture characteristics. They appeared as relatively large and dark objects, contrasting with the smaller-sized, and/or lighter-colored background. M1 was revealed to be a dark-brown object, about 10 cm across, with relatively planar facets, rounded angles, and distinct thumb-sized (1-2 cm across) dimples on the facets (see figure below), suggesting the possibility of an iron-meteorite, the dimples being the reminiscent of regmaglyphs (shallow depressions characteristic of iron-meteorites, formed by erosion of their surface by turbulent vortices during atmospheric entry).},
  booktitle = {Lunar and Planetary Institute Conference Abstracts},
  url = {http://vislab-ccom.unh.edu/~schwehr/papers/atacamaIII.pdf},
  year = {1998}
}
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