23 May 2012
Some people try to make the most of their spare time by exercising, volunteering or simply recharging their batteries. Others like to use that time to build robots that can be blasted to the moon and then set free to roam the lunar landscape. A group of engineers and researchers calling themselves Team Part-Time Scientists have chosen the latter, and are building a moon rover named Asimov they hope will win the coveted Google Lunar X PRIZE by early 2014.
As the name implies, at least half of Part-Time Scientists’ 100 members are holding down full-time jobs at industrial firms or universities. They are competing against 25 other teams to be the first to land a robotic rover on the moon and have it travel 500 meters over the surface, sending high-definition images and data back to Earth as they go.
Part-Time Scientists’ goals are representative of all the teams entering the competition—they are aiming for something more lasting than the $20-million first prize. After guiding Asimov beyond the 500-meter mark, the team plans to switch the rover into autonomous mode for the rest of its lunar exploration, making it the first bot built by anyone to navigate on the moon without human intervention. In addition, the team plans to be the first to use ultrafast graphical-processing units (GPUs)—known for their ability to render complex graphics for video games and scientific simulations—to help their Earth-bound command systems, Asimov’s landing vehicle and possibly Asimov itself gather, assess and act on information in as close to real-time as possible.
Autonomous travel is part of Part-Time Scientists’ strategy to design and test new technologies that could impact not just future moon travel but other interplanetary endeavors as well. “We don’t want to develop something specific for the moon that ultimately is of no use to anyone else,” says team founder Robert Böhme, who works as a cyber security advisor for the German government in Berlin. “We want to take useful technology with us and test it on the moon, which is one of the reasons the robot rover will operate autonomously.”
Other teams are developing autonomous technology for similar reasons, including Astrobotic Technology, Inc., led by legendary bot-maker William “Red” Whittaker, and the Juxtopia Urban Robotics Brilliant Application National (JURBAN) not-for-profit research organization. Astrobotic’s landing system will navigate autonomously by aligning real-time data from cameras and laser with existing satellite imagery of the moon. Meanwhile, JURBAN, like Part-Time Scientists, is designing its rover with autonomous capabilities.
Going for a touchdown
All the Lunar X PRIZE competitors have access to images and data collected by NASA’s Lunar Reconnaissance Orbiter (LRO) as well as from previous manned trips to the moon. Still, Asimov will not really know the specific terrain it needs to cross until it touches down on the lunar surface, says Wesley Faler, the team’s chief software developer. Based near Detroit, Faler’s day job is writing software, including programs for the U.S. Environmental Protection Agency.
“In those last few minutes before landing, we’ll be getting a tremendous amount of video data from the moon,” Faler says. In addition, the landing vehicle that will set Asimov down on the surface has integrated force-feedback sensors that can analyze soil composition around the landing area. “We’re hopeful this combination of visual and tactile data will [yield] an unprecedented level of lunar detail,” he says.
Asimov is to land somewhere in the vicinity of the Apollo 17 site, which has fine soil and few large rocks that might impede the rover’s progress. “We have an algorithm that calculates rock density that shows we can do a lot of exploring without getting into any trouble, such as getting stuck trying to get around [a rock],” Böhme says. Much of what scientists know about this site comes from the original mission as well as LRO flyovers.
Despite all of the preparation that goes into a moon landing, teams cannot be entirely certain of where their rovers will actually touch down. “We’re relying on relatively low-resolution data ahead of the mission and may later find out that there are bumps there that would tip over the lander,” Faler says. Böhme adds, “You need to make adjustments as you go, and to make those adjustments you need information.”
Move over, rover
The GPUs should give Asimov a distinct advantage over prior rovers, even those NASA has on Mars. The rovers there have performed commendably since setting down on the Red Planet in 2004, but Spirit (when it was operative) and Opportunity (which is still active) must pause frequently to gather, assess and act on information about their surroundings, Böhme says. The rovers require nearly three minutes to process a pair of images—a delay that causes them to move at an average speed of about one centimeter per second.
Working with the German Aerospace Center’s Institute of Robotics and Mechatronics, Part-Time Scientists has added an autonomous rover navigation system with the capacity to process multiple images per second. The institute is known for a number of research projects, including the “Justin” mobile robotic system, designed to perform long-range autonomous operations—albeit on terra firma—and the Robotics Component Verification on the ISS (ROKVIS) project on the International Space Station to study robots used in space.
Asimov’s navigation system uses a stereo camera to, in the absence of the Global Positioning System that can only be used on Earth, calculate in real-time its own motion, generate a 2.5-dimensional model of its surroundings, evaluate this model and pursue the path least likely to end in a collision. “A 2.5-D environment consists of flat polygons located in discrete distance bands,” Faler explains. “Consider driving along a road with trees nearby and mountains in the distance. In 2.5-D, all trees and mountains are at the same distance, in one flat plane.” If you were to get closer to one particular tree, for example, that tree would take on additional dimensions whereas the other trees would continue to look flat. For navigation, this amount of data is sufficient and drastically reduces the required computing power, Faler notes.
GPUs guide the way
Part-Time Scientists has several GPUs from NVIDIA Corp. at its disposal. GPU-based computers will play several key roles, including image filtering in transit through space and on the lunar surface; rapid mapping based on sensor and video data; calculating the best trajectory to the landing site; and optimizing communication with the rover despite a moon–Earth signal delay of a few seconds each way. GPU processors will also analyze radio-frequency signals on the moon, whose surface is made up of mostly metallic materials that interfere with these signals. This will help the team determine the best frequency to use for post-landing communications.
Although the details have not all been worked out, Böhme expects to integrate a GPU into the lander’s computer systems and says another GPU could be installed in the rover itself. Any GPU used in Asimov would not be switched on until after the rover reaches the 500-meter milestone and begins autonomous operation. “There is a high interest in making a GPU on the rover possible, but there is a chance that due to technical reasons like weight, shielding and temperature management we might have to just stick to a GPU only on the lander,” Böhme says.
Humans have not operated technology on the lunar surface in four decades, and today’s electronics are much more sophisticated—and delicate—than those used in the Apollo missions, Böhme says. Like any other piece of equipment, a GPU sent up in the lunar lander or Asimov would need to be hardened, which includes shielding against radiation as well as thermal management components to protect it from the extreme lunar temperature range.
Böhme acknowledges that it would be possible to address any of the mission’s needs without the use of a GPU, but emphasizes that one of his team’s goals is to push the limits of available technology and even help drive down the cost of space travel. “Nothing is to be gained by a one-shot, very expensive mission to the moon if it does not act as a proxy for a whole new set of technologies,” he says.