January 02, 2007
Updating Software: And You Thought Your Job was Tough
When it comes to software, updating is a matter of "when," not "if." Just this weekend, for instance, I was going over a soon-to-be-published Dr. Dobb's article by Jack Purdum which described how he took his Microstat, a 1980-era CGA-based program for MS-DOS, and updated it to .NET.
Of course, Dr. Dobb's has published all kinds of articles about updating software. Among those that come to mind are:
But I'm the first to admit that updating desktop software is child's play compared to what's involved in updating software that's anywhere from 35 million to 250 million miles away. That's something that Glenn Reeves found out when finding and fixing the Priority Inversion problem the Mars Pathfinder spacecraft experienced a few years ago.
Still, that's what NASA recently did when updating the software for Spirit and Opportunity, the twin Mars rovers. Spirit will begin its fourth year on Mars on January 3, and Opportunity on January. 24. In addition to their continuing scientific observations, the updated software lets them test new skills, including letting spacecraft examine images and recognize certain types of features. This is based on software developed for NASA's Space Technology 6 "thinking spacecraft."
For instance, Spirit has photographed dozens of dusty whirlwinds in action, and both rovers have photographed clouds. Until now, however, scientists on Earth have had to sift through many transmitted images from Mars to find those few. With the updated software, the rovers can recognize dust devils or clouds and select only the relevant parts of those images to send back to Earth. This increased efficiency will free up more communication time for additional scientific investigations.
To recognize dust devils, the new software looks for changes from one image to the next, taken a few seconds apart, of the same field of view. To find clouds, it looks for non-uniform features in the portion of an image it recognizes as the sky.
Another updated feature, called "visual target tracking," lets a rover keep recognizing a designated landscape feature as the rover moves. Visual target tracking can be combined with a third new feature -- autonomy in calculating where it is safe to reach out with the contact tools on the rover's robotic arm. The combination gives Spirit and Opportunity a capability called "go and touch," which is yet to be tested on Mars. So far in the mission, whenever a rover has driven to a new location, the crew on Earth has had to evaluate images of the new location to decide where the rover could place its contact instruments on a subsequent day. After the new software has been tested and validated, the crew will have the option of letting a rover choose an arm target for itself the same day it drives to a new location.
The new software also improves the autonomy of each rover for navigating away from hazards by building better maps of their surroundings than they have done previously. This new capability was developed by Carnegie Mellon University and JPL.
"Before this, the rovers could only think one step ahead about getting around an obstacle," said JPL's John Callas, project manager for the Mars Exploration Rovers. "If they encountered an obstacle or hazard, they'd back off one step and try a different direction, and if that direction didn't work they'd try another, then another. And sometimes the rover could not find a solution. With this new capability, the rover will be smarter about navigating in complex terrain, thinking several steps ahead. It could back out of a dead-end cul-de-sac. It could even find its way through a maze."
This is the most comprehensive of four revisions to the rovers' flight software since launch. One new version was uplinked during the cruise to Mars, and the rovers have switched to upgraded versions twice since their January 2004 landings.
Posted by Jon Erickson at 10:28 AM Permalink
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