[hawkesnest]

The part that caught my eye was redundancy on memory.

>> Hubble’s operators initially thought a memory module was at fault but switching to one of three backup modules produced the same error.

Apparently Hubble has 4 memory modules which are switchable! I'd love to see how that works. Actually, I'd be fascinated to get a walkthrough of the overall architecture. It might give insights for how we keep business continuity by first accepting that hardware and software will fail.

[belter]

Posted this before here. Maybe worthwhile to post again...

Fig 5-10 is the Data Management Subsystem

https://asd.gsfc.nasa.gov/archive/sm3a/downloads/sm3a_media_...

Concerning the computers:

- First they had a DF-224 flight computer and a

- Science Instrument Control and Data Handling (SI C&DH)

Initially DF-224 between missions got installed a coprocessor:

https://asd.gsfc.nasa.gov/archive/hubble/a_pdf/news/facts/Co...

During another servicing mission they replaced it with something called the Advanced Computer with Intel 80486:

https://asd.gsfc.nasa.gov/archive/hubble/a_pdf/news/facts/FS...

There are some 50,000 lines of code in the C and Assembly programming languages. https://www.nasa.gov/pdf/327688main_09_SM4_Media_Guide_rev1....

They also have a Help Desk...

"Welcome to the Hubble Space Telescope Help Desk"

https://stsci.service-now.com/hst?id=hst_index

[Nition]

Classic movie scenario. Hubble's down, and we need it now. No-one can solve the errors. Old guy walks in, worked on Hubble 30 years ago.

"There's a backup module, with an override command to activate it, but it won't work with the system down. You'll have to use the manual override switch - on the telescope."

[garaetjjte]

It was 64k of core memory originally, but it was later replaced by redundant 4x 64k CMOS memory.

https://youtu.be/RWUnC2uf3XY?t=406