Dante in the crater of Mt. Spurr, Alaska, July 1994
Dante in the crater of Mt. Spurr, Alaska, July 1994
For 20 years, scientists have studied Antarctica's Mt. Erebus volcano and its effect on the Antarctic atmosphere, but have been unable to collect pure gas samples from the crater directly. In January 1993, Dante, an eight-legged, rappelling robot, attempted to explore the crater of Mt. Erebus. Although a failure in Dante's tether cord prevented the robot from reaching the crater floor, many other aspects of the mission-such as remote operation of the robot from the continental U.S. were successful. Since the Mt. Erebus mission, the undaunted Dante has been refined and improved for an investigation of the crater floor of Mt. Spurr, Alaska, another active volcano 80 miles west of Anchorage. Dante II returns with stronger legs, a different gait and leg configuration, and a stronger winch and rappelling cable. Its software and vision system have also been refined, but its mission is largely unchanged: rappel and walk autonomously over rough terrain in a harsh environment; receive instructions from remote operators; demonstrate sophisticated communications and control software; and determine how much carbon dioxide, hydrogen sulfide, and sulfur dioxide exist in the steamy gas emanating from fumaroles in the crater. Dante II's leg configuration has changed from four legs on each side to four legs each in front and back. This front-and-back positioning of the legs supports the robot more steadily than before and enables structural and control advantages. The legs themselves have also been improved for a nearly three-fold increase in their strength and stiffness. Like the original Dante, Dante II combines tether and leg motion to rappel down or back up steep slopes and even sheer cliffs. The tensioned tether cable, which assists the robot's balance, is anchored to the crater rim and spooled by a winch on-board the robot. The winch contains sensors to monitor the cable's travel and tension. Because Dante rappels as well as walks, its descent routes are fairly linear, making only minor side-to-side detours when avoiding untraversable terrain. Also connected to the tether cable is a generator and a satellite dish. Via satellite, Dante II sends back visual information and other data, as well as receives instruction from human operators at control stations in Anchorage, Washington D.C., and the NASA Ames Research Center in San Francisco. Through eight video cameras mounted on the robot, remote viewers (students, press, robot operators, and volcanologists) at the three base stations can monitor Dante II's progress using virtual reality interfaces and graphical computer displays. Dante II itself views the terrain through a laser rangefinder, which maps terrain in a circular region around the robot within a radius of six meters. An on-board computer uses this terrain map to determine a safe path for Dante II, which walks over objects as high as one meter and around objects higher than one meter. With every step, sensors in the robot's legs continuously gauge the force on each foot, allowing the robot to adjust each step to the geometry and firmness of the terrain. Dante II saves volcanologists from having to enter the craters of active volcanoes. It also demonstrates the technology necessary for a robot to explore the surface of the moon or planets. That is, the robot must be able to walk on rough terrain in a harsh environment, receive instructions from remote operators about where to go next, and reach those commanded goals autonomously.
Dante II and its mission to Mt. Spurr are funded by NASA. .
