Curiosity, the latest man made object to occupy Mars is a marvel of technology. The robot, as big as a car, safely touched down on the red planet and almost immediately began its mission. One of the first things it did was to take photos and let us know it was safe and sound. To control the experiments, vehicle operations and everything else on the probe, NASA chose an advanced microprocessor: the G3 PowerPC chip.
The chip runs at 200mhz, which is more than fast enough to do what it needs to do. It has 256 megabytes of RAM and 2gb of Flash Memory for caching of data and photos for transmitting back to the orbiting observatory and, eventually, back to Earth.
If you do not know, the G3 is, now, a fairly old and slow processor, but, for what NASA needs, it is state of the art. The chip that NASA is using is a hardened chip. That means that the chip can withstand all of the dangers of space: radiation, cold, heat, cosmic rays, etc. If they used a normal chip, the craft probably would be useless by now.
The G3 is also the processor that Apple used in Macs, back in the day. The processor isn’t all that Curiosity shares with its Mac brethren: the operating system in the probe is VxWorks, the same operating system that is in use Apple’s Airport Extreme WiFi hub. VxWorks, while old, is a solid, stable and proven real time operating system. It is still being developed by Wind River Systems.
The system is smart enough to detect problems, such as hangs or software faults and can reboot itself. If the main CPU dies, a secondary CPU will take over. Software can be upgraded on the fly and add new functionality (provided the hardware can support it) on the fly. NASA has been able to do this since the Voyager craft lifted of decades ago.
One might wonder why NASA continues to use ‘old’ technology in its spacecraft. Well, the simple reason is that the craft are in planning stages for years, then they move onto the construction stages and, finally, they get launched. During that time, though, the software is developed and thoroughly tested. It is a bit difficult to send a programmer or technician to fix something post launch, so everything is tested and retested and tested again. It is probably the most bug free code deployed.
That this all works is almost as much as impressive as the landing of the craft on Mars is itself. My hats off to designers, builders, developers and testing people…well done!