Mars rovers: Better, safer, faster
- By Sarita Chourey
- Apr 16, 2004
NASA officials say they are already seeing the results of a just-completed software upgrade to enhance safety, productivity and durability for the Mars rovers.
The space agency had allocated about 24 hours across four sols, or Martian days, for the transplant. But uploading files to the rovers ultimately took less time than needed -- about 16 hours over three sols.
"The rovers are in really good shape healthwise, and the deep sleep mode for Opportunity allows us to conserve energy rather than using it on the heater," said Jan Chodas, flight software manager for the project and an employee of the California Institute of Technology's Jet Propulsion Laboratory. "As the mission goes on, Mars moves away from the sun and the energy available each day drops. So it's more important to conserve energy to run the rover everyday. This enables more data gathering."
A sol is 40 minutes longer than an Earth day.
Following the completion of the three-day software update on April 14, Spirit awakened from its dormancy to the song "Where is My Mind?" by the Pixies. Opportunity heralded the completion of its transplant with the Ramones' "Teenage Lobotomy."
Engineers expect the rovers to cover a greater distance per sol than before. Spirit already had gone father than the mission's original target of 600 meters before the upgrade; now NASA officials hope it can reach an area that scientists named Columbia Hills, a cluster east of the rover landing consisting of seven hills dedicated to the final crew of the space shuttle Columbia. Each hill is about three kilometers apart.
"It's a race against time," Chodas said. "Something will break eventually. But the rover will be healthier than if we had gotten there later. We can go faster now."
They'll be able to travel longer distances autonomously thanks to updated navigation software. Rather than getting stuck when they encounter an obstacle, the rovers will be able to turn in place in order to navigate a path around the hazard. The updates will also enhance memory capabilities. By compressing flash directories, Spirit increased its capacity from 2M of memory to 3.3M.
The newest software is a more advanced version of the code installed in December. "If [the rover] saw something, like driving up a pitcher's mound, it decided it's not going to go there," said Chodas about the previous software. "Now we've got experience," she said. "We made it a little more aggressive, but still safe... [In the past] it used hazard cameras, but now it can also use navigation cameras to let it see farther."
Engineers also expect that the new software will dramatically increase the rovers' productivity by reducing the amount of redundant images collected. The rovers used to move 35 centimeters, gather images, analyze them, and then move another 35 centimeters and repeat its operations. Now they can continue moving if the landscape has not changed, rather than gathering images identical to those from the last stop. Wednesday marked the first use of this capability.
"Sure enough it covered a greater distance because it wasn't retaking the pictures, which takes time to process," Chodas said. "We're not losing out because we understand the terrain well enough and we understand what the rock hazards look like. We gave the mobility software more options and more ways of commanding the driving."
Part of the flight software update also includes a safety net. Engineers have equipped the rovers to better recover from incidents such as the one that temporarily cut off communication with Spirit soon after it landed in January, when NASA engineers believe it ran out of random access memory.
The third major change protects Opportunity from losing battery power. In allowing the rover to go into a deep sleep mode, the software will disconnect the batteries from controlling the stuck heater switch on the rover's instrument deployment device, so the battery will not be drained. If such a capability becomes necessary for Spirit, NASA officials will load the software onto that rover as well, agency officials said.