We imagine that in space missions all technology is the latest of the latest, but the truth is that in some cases that is not the case. The example we have in the CPU of the Perseverance rover that is currently traveling the surface of Mars.
That Perseverance rover processor is nothing new: it is based on the PowerPC 750 that were launched at the end of 1997 and that would end up being the heart of the legendary colored iMac (G3) that Apple launched in 1998 and that were one of the first surprises of that renewed company after the return of Steve Jobs.
200 MHz is enough for Perseverance rover on Mars (for now)
NASA itself confirmed the specifications of the Perseverance rover for the Mars 2020 mission long ago. In his article on the “brain” of the rover, he explained how the central computer, called the Rover Compute Element (RCE), has two identical units that allow the vehicle to continue operating even if one of the two units fails.
Those technical specs are surprising because they actually seem more typical of projects from 20 years ago. The processor is a RAD750 manufactured by BAE Systems Electronics, Intelligence & Support, a company specialized in the aerospace industry.
This processor was launched in 2001 and like the rest of the microprocessors in the family, it is prepared to withstand the extreme radiation that space missions face.
The RAD750 is basically a PowerPC 750 reoriented to these types of applications. It is the same processor that IBM and Motorola / Freescale launched and that was part of the 1998 iMac, although Apple renamed it to include it in the family of processors baptized as PowerPC G3 – which included other later variants of the PowerPC 750 – and applied it as much to those iMac like the PowerBook G3 or even the Power Macintosh G3.
Like this one, it is manufactured in 150 or 250 nm photolithography (when today’s most modern CPUs use 5 nm processes), and has 10.4 million transistors, a very modest number for the hundreds and even billions. transistors of current processors and GPUs.
It is also surprising how the RAD750 operates at 200 MHz , which NASA highlights by stating that this is “10 times the speed of the computers built into the Spirit and Opportunity rovers” that were also sent to Mars.
That processor has 256MB of RAM, a 256KB ROM, and a 2GB Flash storage drive. These processors may be old and modest in power compared to current ones, but that preparation to withstand extreme radiation while keeping them operational is not cheap: the cost of one of these processors is estimated to be around $300,000.
These processors have been part of numerous missions and space vehicles used by NASA, such as the Kepler space telescope, the Lunar Reconnaissance Orbiter or the Juno spacecraft, among others.
It is ironic how the processors of our mobiles are several orders of magnitude more powerful than the one included in the Perseverance but still that modest CPU is more than enough to fulfill its task on the red planet. In fact, the Ingenuity helicopter from that same mission is based on a Qualcomm Snapdragon 801 (much more powerful than the RAD750) and on Linux, as we saw recently.
