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Jeff Norris, a senior computer scientist at NASA's Jet Propulsion Laboratory who headed development of the rovers' open source-heavy Science Activity Planner (SAP), said the mission extension was a steal for taxpayers, whose space and research support has shrunk along with NASA budgets.
"If you've got two functioning rovers sitting on Mars, the money involved in that extension is the greatest bargain in the world," Norris told NewsForge. "They can go and explore things and see things that have never been seen before every single day."
Norris -- who has highlighted the rovers' open source components, their advantages and OSS potential at NASA -- said while the rovers were built to travel a maximum of 600 meters, the slow, deliberate space buggies have each logged about 3.5 kilometers to date.
"The thing we're most excited about is the performance of the rovers that has far exceeded expectations," Norris said. "There are so many pictures [the rovers have already delivered], but there is so much more to see."
Open and able
After surviving an unEarthly-cold, Martian winter solstice over the last couple of weeks -- during which neither Spirit nor Opportunity were given commands for activities or movement -- both rovers are now being revved up again by NASA engineers on Earth who are relying on open source systems for much of the rovers' functionality.
|The Mars rover, the Red Planet, and a view of the Blue Hills.|
Norris said open source proved to be the most economical solution as he and his team looked to give taxpayers more bang for the buck in the rovers.
"We're not being funded to go write databases and solve problems that other consortiums and other open source groups are already doing well," he said. "We may be good at driving rovers, but we're not good at database programming, using an XML parser, or building a framework. The biggest benefit of open source is you don't develop what already exists at a much better quality than we can produce."
While both Spirit and Opportunity have proven agile vehicles as they maneuver around the bumpy, rocky terrain of Mars, Norris said the use of open source software gave his team agility as it developed the rovers' systems.
Norris said open source software is not necessarily onboard the Martian rovers, but is instead here on Earth controlling them and communicating with them. He explained that during development, NASA engineers were able to focus on their mission rather than those components that were going to rely on open source.
"It let us say, OK, we don't have to start development on this or that so we reserved the investment for the things we had to do," Norris said. "We were betting on open source tools to cover things, and it was easy for us to let that capability go to open source."
Mission critical required source
Norris also praised the agility of the open source communities and developers that rover engineers worked with in building Spirit and Opportunity functionality.
The JPL engineer said that because the rovers' systems were all mission critical -- a term that takes on more urgency when the hardware is being sent to space with no return ticket -- the rover systems' designers demanded access to all of the source code involved, including for some commercial components.
"We didn't use anything in our systems that we couldn't get access to source for," Norris said.
The commercial components that were used for rover systems involved obtaining and paying for source code, but Norris said the team found the open source software used in the project to be comparatively superior.
"Among the components we used, we found the open source components to be of far greater quality," he said.
The responsiveness of open source developers was also impressive, according to Norris, who compared turnaround times of hours for open source to months for commercial providers.
"All they could really guarantee us was some developers were looking at it and it might be in the next release in six months," Norris recalled. "We had to fix it ourselves and it was a potential integration nightmare if they did release a new version."
Response on fixes or workarounds from open source developers, conversely, was immediate, Norris said.
"I'm not saying we'll never use a commercial component again, but it certainly was a bad experience for us," he added.
Small step for software, giant leap for open source
The rovers running on Mars today and the Earthbound systems that control them may be NASA's biggest use of open source software to date, but Norris indicated there is more on the way.
Despite the typical resistance to and apprehension over open source -- and the added challenges of working on space stuff that is often categorized as weaponry -- NASA is getting there, Norris said.
"People are obviously wanting and using open source and becoming more aware of open source," he said. "We are making great strides in that direction."
Norris referred to NASA's "Roverware" project, which is aimed at open sourcing some of the products that were used in Spirit and Opportunity. Although it may be limited to a source-available release that will require a Caltech license to incorporate into a commercial product, Norris said the space agency hopes to release as many as three of the components as open source by the end of the year.
The first and most likely is the source code for SAP, which is known as Maestro, and is available for download in limited form today. Norris said NASA also hopes this year to open source CLARAty -- a software infrastructure for rover research -- and Roams, which is a simulator to help teach rover driving here on Earth.
As for the extended mission for Spirit and Opportunity, Norris said as long as the rovers are running, they are likely to get funding from NASA to continue their travels on Mars.
"As long as they can move and take pictures, I can't imagine them turning them off," he said. "You never know what you're going to see over the next hill."