Don't want to spoil the joke thread with a serious response, but -- what processor DOES the JWST use? How out of date is it given the project started in the 90s?

The primary compute bits include the science instrument data handling electronics, the Solid State Recorder (SSR) and the Command & Data Handling processor (C&DH).

NASA has plenty of publications about the design, I haven't found anything yet that covers the SSR or C&DH yet, but this is an interesting article about implementing SpaceWire reliable messaging in an FPGA.

The science data handling here is done in an Actel AX1000 FPGA.

@eqe has some details, including discussion of Rational Rose Real-Time UML and communication on the Spacewire bus.

@eqe and they can be modifid:

The fact that the OSS is written in JavaScript and stored on-board as text files is significant because this gives the operations personnel greater visibility, control and flexibility over the telescope operations. As they learn the ramifications and subtleties of operating the instruments, they can modify the JavaScripts and, after thorough testing in a ground facility, they can simply replace an onboard file to make the change.

@th @eqe we like the JWST. we do not mess with the JWST.

@uint8_t @eqe will the JWST JavaScripts framework be deprecated before it reaches L2?

@uint8_t @eqe (javascript jokes aside, that is a really wonderful document for space nerds about the compute and electrical components on the and the complexity of thermal management for 300K equipment near IR sensors at 50K or lower)

Running on PowerPC, which answers the original question I think. Foone has the details:

@th @eqe

@EdS @th @eqe A huge upgrade over the Hubble Space Telescope. I believe it's still running on an 80286 processor!

@EdS @th PowerPC is the architecture, doesn't answer what chip it is, probably it's a RAD750 since that's the most common for usgov space designs.

Ah and wikipedia confirms...

"James Webb Space Telescope, launched 25 December 2021, uses one RAD750 clocked at 118 MHz."

Foone's speculation of triple redundancy is unlikely, NASA only does that for human life critical systems and it's not mentioned in any of the jwst docs.

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