IT plays key role in Mars Pathfinder mission
- By Heather Harreld
- Jul 13, 1997
Almost every aspect of the Mars Pathfinder mission is driven by information technology - hardware and software that has exceeded expectations for performance and helped to drive down the exorbitant costs of space exploration.
Although the first few days of the mission have passed with apparent ease producing spectacular images of the barren planet scientists and engineers have breathed a collective sigh of relief with each individual success. That is because this mission is geared toward pushing technology to its "bleeding edge" and has taken calculated risks in an attempt to complete the ambitious project for about $270 million. By contrast previous space missions have cost more than $1 billion.
One of the main components of the mission is the on-board processor that guided the Pathfinder Lander's journey to Mars controlled its landing and now governs its operations from the planet's surface. The processor a radiation-hardened version of IBM Corp.'s 32-bit RISC System/6000 was adapted for the mission by Lockheed Martin Federal Systems in Manassas Va.
The chip is the first radiation-hardened commercial processor to guide a NASA mission. The RAD6000 as it was renamed by Lockheed was responsible for crucial elements of the flight to Mars such as cruise altitude control. The chip also managed the Lander's entry events including deploying the parachutes and air bags that cushioned the Lander's fall to Mars. And since the successful landing it has been transmitting information from surface operations from Earth to Mars and back.
Since Pathfinder's December launch the RAD6000 has processed radio signals from Earth interpreting the signals into maneuvers and course-change commands. For the Lander's five-minute catapult toward the surface of Mars the processor was responsible for controlling 57 explosive events said Lloyd Keith cognizant engineer for the Mars Pathfinder flight computer and operating system in an interview before the successful landing.
"If any of those [events] fails then the mission fails " he said. "We're essentially going in just like a bullet. It's a time of dark and utter terror. It is very probable that at some point something will go wrong. There is no guarantee that all of this will work. We're trying to establish a way to get to Mars in a faster and cheaper way. There are certain risks that we've had to take."
Although using a commercial processor as the basis for the Pathfinder flight computer has cut development costs dramatically the approach did not eliminate the need for Lockheed Martin engineers to adapt it for the harsh conditions found outside the Earth's atmosphere. Aside from the fluctuating temperatures - ranging from minus 55 degrees Celsius to 70 degrees Celsius - the primary danger to the electronics is the high-energy particles that would shred any electronic component once it leaves the protection of the Earth's atmosphere.
While many attempts have been made to create shields or "bulletproof vests " for electronic equipment in space Lockheed designers took a unique approach to warding off the deadly particles said Vic Scuderi business area manager for space processing products at Lockheed Martin Federal Systems. "The idea is to harden the electronics - to not shield the particles but to withstand them " Scuderi said. "The `bullet' can still go through the processor and it never affects it."
Despite its radiation-hardened state the commercial version of the processor provides the Pathfinder mission with 22 million instructions per second (MIPS) of processing power. The RAD6000 can provide an unprecedented space throughput capability of up to 35 MIPS according to Lockheed officials.
In addition to the processor chip the flight computer contains a sealed memory unit that also uses commercial off-the-shelf technology with tweaks to allow it to survive the energy particles. Although the mission required 128M of dynamic RAM this type of memory space is not available in the hardened state Scuderi said. The processor's memory unit detects any damage done by the particles and heals itself through a special error-correction process.
The use of COTS products allowed Lockheed Martin to keep mission costs down by taking advantage of all the hours already devoted to the commercial processor and also resulted in a shorter development cycle Scuderi said. "We have a solid design in space because we took a COTS product and through government funding evolved it into a radiation-hardened space processor " he said.
Software Controls for the Rover
The Mars mission's Rover which is collecting rock and soil samples and providing close-up surface images is being controlled by a software architecture designed by Telos Corp. and is operated by Jack Morrison a Telos software engineer and one of two Rover drivers.
Despite the appearance of the Rover being operated in real time by remote control the Rover actually must operate without direct human control because of time delays in the communications between Mars and Earth Morrison said in an interview last week. After receiving daily information regarding the types of data or images scientists hope to gather Morrison or the other driver sends the Rover a sequence of commands once or twice a day."The Rover has to run automatically a lot of the time " Morrison said. "It really needs to think for itself [about] what it's doing to make sure it doesn't get into trouble."
To help the Rover protect itself Morrison and other engineers designed a control station used to view 3-D images of the rugged terrain to plot the safest course for the Rover. The Rover's software however is designed to allow the unit to reliably circumnavigate unexpected environmental conditions and adapt to minor hardware or software glitches. The software architecture also includes instructions for the Rover periodically to check its own health including its power supply and temperature he said.
The 3-D images that help guide the Rover are generated on Onyx2 visualization supercomputers from Silicon Graphics Inc. The first image data returned to NASA scientists was processed by the Onyx2 system which then generated the model of the Martian surface. The image data is then overlaid onto the model to create a highly realistic representation of the terrain the Rover drivers can then take a virtual flight over the terrain and interact with a virtual Rover before sending commands to the actual Rover.
SGI workstations also will allow scientists to digest the massive amount of data being beamed back to Earth from the Rover. In Pasadena Calif. two SGI O2 workstations and eight Octane workstations will allow NASA officials to analyze the images and data generated from the various instruments as it is transmitted from the Red Planet.
Morrison's team also found innovative ways to perform tasks required for mission planning such as using intranets to pass information between team members instead of manually passing design specifications between people.
Networking Gear Aids Mission
Networking products from Cabletron Systems Inc. also are playing a central role in the Pathfinder mission allowing mission specialists in California Australia and Spain to transmit commands to the Rover. All the computers in the three stations connect to Cabletron Smart-Switches which are intelligent connectivity devices designed to facilitate computer communication.
In addition to supplying various Cabletron products to provide increased bandwidth and eliminate jittery delayed data delivery the company also provides a security mechanism to protect transmissions from overlapping other transmissions and from unauthorized access.