Stereo images plot the surface of Mars
Stereo images plot the surface of Mars
RICK NELSON AND ANDREW WILSON
Launched last December, the NASA Pathfinder landed on Mars, as scheduled, on July 4. Roaming the planet`s surfaces, the Lander and Rover, stereo camera systems, RISC-based CPUs, and real-time operating systems joined forces to obtain the first ground-level images of the red planet.
For guidance, the Rover uses two Kodak KAI-0371 stereo monochrome sensors mounted up front to provide stereo maps of the Mars surface. The sensors also help the Rover safely traverse the Martian terrain and navigate around rocks. In addition, a single KAI-037M sensor located on the rear of the Rover furnishes color images of ground and soil samples. Supported by a progressive-scan color-CCD camera with square pixels, the sensor digitizes 640 ¥ 480-pixel images that are relayed to the Lander for transmission to Earth.
Because data from the cameras are collected in real time and the Lander simultaneously maintains communications with Earth and the Rover, the Jet Propulsion Laboratory (JPL; Pasadena, CA) selected a radiation-hardened IBM-RAD-6000 central processing unit (CPU) to control the system. To run a real-time operating system on the processor, JPL contracted Wind River to port VxWorks to the CPU. "Image data (typically, 4-kbyte JPEG files) start their way to Earth as 8-GHz signals at the Pathfinder`s high-gain antenna," explains Leif Harcke, a JPL telecommunications systems analyst. On Earth, JPL`s Deep Space Network 34-m-diameter antenna receives the signal after a 190 million-km journey and downlinks the data at a 40-bit/s rate.
To provide widespread access to the data, JPL engineers developed an applet called WITS (Web Interface for Telescience) to permit worldwide public viewing of data and images on the Internet. At Mars mission control in Pasadena, CA, stereo image data are visualized using a CrystalEyes stereoscopic system from StereoGraphics. As the mobile Rover traverses the Martian surface, stereo images viewed by NASA scientists provide accurate depth and perspective as the craft is piloted along the Martian surface.