NASA Switches Curiosity Rover To Backup Computer Following Glitch (extremetech.com)

NASA has switched its Curiosity rover over to its backup computer system after the main system started experiencing errors last month. "Many NASA spacecraft and surface missions have redundant systems built-in," reports ExtremeTech. "Once they've launched from Earth, there's no way to repair damage to critical systems, so it makes sense to double-up on the vital components. That includes Curiosity's computers, which were designed specifically for the harsh environment on Mars." From the report: The rover has a pair of identical brains running a 5-watt RAD750 CPU. This chip is part of the PowerPC 750 family, but it has been custom designed to survive high-radiation environments as you'd find on Mars or in deep space. These radiation-hardened CPUs cost $200,000 each, and NASA equipped the rover with two of them. Each computer also has 256 kB of EEPROM, 256 MB of DRAM, and 2 GB of flash memory. They run identical VxWorks real-time operating systems. When Curiosity landed on Mars in 2012, it used the "Side-A" computer. However, just a year later in 2013 (Sol 200), the computer failed due to corrupted memory. The rover got stuck in a bootloop, which prevented it from processing commands and drained the batteries. NASA executed a swap to Side-B so engineers could perform remote diagnostics on Side-A. In the following months, NASA confirmed that part of Side-A's memory was unusable and quarantined it. They kept Curiosity on Side-B, though. With Side-B experiencing problems preventing the rover from storing key science and engineering data, NASA switched Curiosity back to Side-A while it investigates the problem, which it can only do when the other computer is active. "NASA hasn't said how much of Side-A's RAM is bad, and it only had 256MB to start, but the team does intend to move Curiosity operations back to Side-B if possible," the report adds. "For now, the mission is functioning normally on Side-A."

Comments

Only?

[xonen]

it only had 256MB

What a strange use of the world `only`. 256MB is a lot, really a lot.

We could run our desktop computers with 256MB RAM at ease if we wanted to. As comparison: When windows 2000 was released (around 2000...) most computers only had around 64MB of memory, and that would already be a reasonable beefy computer. Windows 2000 liked a bit more, around 128, but would run on this 64MB just fine albeit a bit slow. And this same windows 2000 offered a desktop experience not much different from the (windows) desktops we are using today, including proper plug and play support, multimedia and whatever fancy you liked. When XP came a couple of years later, most people still hadn't updated to 256MB of memory.

Now, compare that to an embedded computer that does not have to waste any memory on fancy graphics, user interfaces and what more, and you will notice that 256MB is a lot. Really a lot. Try writing code to fill that up - a single human couldn't, even a whole team can't. Obviously it'll need some memory to store images etc, but this 2GB of flash is also a lot and comparable to what the first digital camera's came with..

And for those saying 'long time ago long time ago' - even today it's pretty common to write software that has no more than a single kilobyte of RAM memory available, for embedded purposes. With all the modern webcrap using gigabytes of memory for trivial tasks people seem to have lost the feeling for quantity. 256MB are more bits than i can count in my lifetime..

Re:Only?

[xonen]

You can count pretty fast then, must be my age. If i count one number each second, it would take me around 66 years to count 2 billion bits. I hope i'll live that long but if i'd start now, i doubt i'll complete the task. And that's without adding some time to sleep each day.

Back to school you.

Re:Only?

[Mal-2]

It's a data collection instrument. That data has to sit somewhere, it doesn't have a continuous uplink to the MRO. Photos take space.

Re:Only?

[ls671]

Seriously?

You didn't work too hard on that one :)

https://en.wikipedia.org/wiki/...

Each camera has eight gigabytes of flash memory, which is capable of storing over 5,500 raw images, and can apply real time lossless data compression.[62] The cameras have an autofocus capability that allows them to focus on objects from 2.1 m (6 ft 11 in) to infinity.[65] In addition to the fixed RGBG Bayer pattern filter, each camera has an eight-position filter wheel. While the Bayer filter reduces visible light throughput, all three colors are mostly transparent at wavelengths longer than 700 nm, and have minimal effect on such infrared observations.[62]

Re:Only?

[FaxeTheCat]

Mythoughts as well.
I used to have a Dell CPx laptop with 256 MB in the early 2000's, and that worked quite well. Not to even mention Windows 3.1 on 4 MB.

Just out of cutiosity, I googled the RAM requirements for vxorks, and Version 6 from 2004, has the following requirements:
VxWorks CISC processors require 1 MB of RAM for a development system that includes the standard VxWorks features, such as the shell, network, file system, loader, and others.
RISC processors typically require more RAM space: 2 MB of RAM is the minimum; 4 MB is encouraged. For a scaled-down production system, the amount of RAM required depends on the application size and the options selected.

So 256 MB leaves most of the RAM available for the applications.

Re:Only?

[ls671]

Would you guys please stop this? :)

256MB is like 640MB when it used to be 640KB for the job it has to do. Do you figure the guys who sent it there were on some kind of budget or that they were imbeciles?

I already posted with arguments and links and I don't want to repeat myself but the rover has many gigabytes of memory.

Then again, we could blame click-bating summaries but that's another story.

The next rad-hard cpu will be ARM based

[Required Snark]

Boeing to develop next-generation radiation-hardened space processor based on the ARM architecture

It will be used by NASA and the military and should be available in 2020.

Re:The next rad-hard cpu will be ARM based

[DanDD]

Your link is circular back to this same slashdot article, but a google search of your link title finds this:

https://www.militaryaerospace....

This is cool, thanks!

Also interesting:

An alternate approach that doesn't require expensive radiation hardening also seems to have worked with a half-day transition through the Van Allen belt. It will be interesting to see if their approach can stand up over time on a long mission.

Re: The next rad-hard cpu will be ARM based

[religionofpeas]

Even if radiation on Mars surface is limited, the computers still have to survive the trip from Earth to Mars. The problem is that the cosmic radiation causes permanent damage to the crystalline structure of the semiconductors, building up over time until they stop working completely. COTS processors simply wouldn't survive, and redundancy doesn't help much if they are all getting damaged at the same rate.

Re:The next rad-hard cpu will be ARM based

[religionofpeas]

Also, triple redundancy only helps to protect against SEE (Single Event Effects), those are cases where an ionizing particles changes some charge, and flips a bit in the memory. These are recoverable errors. The processor can reset the faulty bit, and continue normally.

The problem is that part of the cosmic radiation consists of heavy element nuclei, flying at near speed of light. These don't just flip some bits, they have enough energy to permanently dislocate atoms in the crystal silicon lattice. Due to this damage, the processor will get higher leakage currents, and will eventually stop working altogether as the damage accumulates.

Shielding is impractical, because a thin layer of metal (good enough to block gamma radiation), can't stop these highly energetic particles. Even if the particle hits the shielding, it doesn't stop it, instead you get a shower of secondary particles, still strong enough to cause damage. Radiation hardened processors use a different technology that is less sensitive to damage (at the cost of lower logic density)

Re:"... drained the batteries..." what?

[K. S. Kyosuke]

The RTG on the rover is "right-sized" to provide the necessary *average* consumption, as anything more would be wasting plutonium. However, since momentary consumption fluctuates, there's a battery buffer to smooth over the load profile.

Re:"These radiation-hardened CPUs cost $200,000 ea

[FaxeTheCat]

Or "developing specialized semiconductors with extreme testing requirelents and a sales potential in the (at best) double digits is extremely expensive."