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While not as dramatic as "cross-circuiting to A" in the video, The NASA JPL news item Curiosity Rover to Temporarily Switch 'Brains' indicates that Curiousity has been switched back to "brain A" due to some issues related to storing data for later relay to Earth.

Since the initial launch of the Mars Science Laboratory, how many times has Curiosity switched between its two redundant computers?

Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, this week commanded the agency's Curiosity rover to switch to its second computer. The switch will enable engineers to do a detailed diagnosis of a technical issue that has prevented the rover's active computer from storing science and some key engineering data since Sept. 15.

Like many NASA spacecraft, Curiosity was designed with two, redundant computers -- in this case, referred to as a Side-A and a Side-B computer -- so that it can continue operations if one experiences a glitch. After reviewing several options, JPL engineers recommended that the rover switch from Side B to Side A, the computer the rover used initially after landing.

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tl;dr: Four times.

  • A (1st boot perhaps)

  • A → B during the interplanetary transfer

  • B → A during the August 2012 landing

  • A → B March 2013 (memory fault)

  • B → A and now in September 2018, we have the 4th switch.

From the report, it says the the only other time a memory switch was attempted due to faulty memory was back in March 2013, when it officially switched to the B-side from the A-side, but this was the 2nd switch between the 2 memories, as the 1st one was probably at the interplanetary transit phase which used the Side B for part of the flight, meaning that it used A(1st boot,maybe) and switched to B during the transit(1st switch), then switched back to A(2nd Switch) during the August 2012 landing and the glitch forced it to switch to B in March 2013(3rd switch) and now in September 2018, we have the 4th switch. There maybe have been more switches conducted during testing right after it went into orbit before it began the interplanetary transfer, but I couldn't find much information on it.

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  • $\begingroup$ Hey, I improved the answer, uhoh @Aaron . Hope it helps clear things up $\endgroup$
    – Rajath Pai
    Oct 5 '18 at 2:23
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    $\begingroup$ @uhoh I remark upon the most commonly known memory switches and then explain where the other ones were. However, I started them first somewhere in between and explain the sequence. Sorry for the poor formatting $\endgroup$
    – Rajath Pai
    Oct 27 '18 at 8:23
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    $\begingroup$ I've cleaned up old comments, thanks for the answer! $\endgroup$
    – uhoh
    Oct 27 '18 at 9:37

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