A very strange optics issue...

Max-Q

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So I had something very strange happen during a P52. I followed all the steps up until I was supposed to center the star in the SXT crosshairs. When I move the optics, they won't move very far, then as soon as I let go, they bounce back to the original position!
Yes, I am on opt mode Manual, and the DSKY shows F51.
If I exit P52, the optics work as expected in Manual mode.
The only way I can complete a P52 is to not give the optics to the CMC at all, and center on the selected star totally manually.
All of my P52s worked as expected until I did a P52 option 1. That one worked fine, but I have had this problem ever since.
 

indy91

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I've definitely seen this before. The CMC is allowed to use the optics in manual, it's just the software that sees the switch in manual mode and usually doesn't do that. What sometimes screws this up is some P40 exit settings (SPS TVC uses the optics CDUs) not working right. I don't know how or why though. It seems like more of a CMC software issue than NASSP code, but I haven't read anything about this in the historical documentation. Maybe it only affects some missions? But I think what would fix it is the next SPS burn and exiting P40. I don't remember how to fix it without that, probably some flagword to set or so.
 

Max-Q

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It happened on Apollo 8 right after MCC4 (RCS, P41)? I pressed on through LOI-1 and the issue is still there. I will try LOI-2 and report back. This also happened on Apollo 7.
Since the CMC software for 7 is not available, 7 and 8 use the same CMC software, correct? If so, that might explain the issue happening on both missions.

Here is a scenario. Just run a P52 opt 3.
 

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Miriam

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When I remember right, I solved the problem by putting the CMC in standby via P06 and power it back up immediately. You could try that, doesn't hurt.
 

Thymo

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When I remember right, I solved the problem by putting the CMC in standby via P06 and power it back up immediately. You could try that, doesn't hurt.
If you do this you do need to reset the REFSMMAT and DRIFT flags though, apart from that there's no side effects.
 

Miriam

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Right, go through the 'P06 inadvertently selected' stuff, I forgot.😅
But still strange, isn't it? As if P40 doesn't end a task or forgets to deactivate the TVC DAP. Maybe it could help to turn the DAP off and on again: Call V48, set R1 of N46 to 0XXXX, cycle through the rest of the routine (this should kill any DAP jobs), call V48 again, set R1 of N46 back to 1XXXX again, cycle through the rest, key V46E. Worth the try.
Edit: tried it, won't work. P06 does, though, V36, too. Really looks like some zombie job stays alive after P40.
Edit2: Narrowed it down to Channel 12: I get 00040 in P00. In P52 it gets stuck in 00042 once the auto-optics routine sees that the Mode sw is in CMC. The 4 (enable IMU error counter) shouldn't be there in the first place, the 2 (enable optics error counter) should change depending on the Mode and Zero sw -it doesn't. Very interesting.
 
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Max-Q

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go through the 'P06 inadvertently selected' stuff
How do I do that?
Also how do I do a V36? Meaning, do I just key it in, or will I need to reset some other stuff after?
 
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Miriam

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How do I do that?
Set the DRIFT and REFSMMAT flags again:
V25N7E, 76E, 40000E,1E (that's DRIFT)
V25N7E, 77E, 10000E,1E (that's REFSMMAT)
I'm not quite sure, but AFAIK the RCS DAP isn't restart-protected, so you'd have to cycle through V48 once and do a V46E, too.
Also how do I do a V36? Meaning, do I just key it in, or will I need to reset some other stuff after?
Yes and yes: V36E will cause a restart, after which you'll have to set those flags again.
 

Thymo

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Edit2: Narrowed it down to Channel 12: I get 00040 in P00. In P52 it gets stuck in 00042 once the auto-optics routine sees that the Mode sw is in CMC. The 4 (enable IMU error counter) shouldn't be there in the first place, the 2 (enable optics error counter) should change depending on the Mode and Zero sw -it doesn't. Very interesting.
The IMU error counters are used to display IMU error from the desired DAP attitude on the FDAI, that's why that's on.

I haven't yet figured out what the cause of this issue is. In order to watch some memory locations while making DSKY inputs I have constructed an EMP to put a location in unswitched erasable on the downlink list as ALARM 3 (R3 of noun 9). This can be viewed using NASSP's telemetry client: https://github.com/orbiternassp/telemetryClient/blob/master/GroundStation.exe

Here's the EMP: https://gist.github.com/ThymoNL/68565ebe876eaa90b2a351a0e464368d
 

Max-Q

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P06 CMC standby worked. The issue never reoccurred, even after TEI.
Thanks for helping me through this! Funny thing is though, I have flown a bunch of missions in NASSP, and this issue only appeared on the last two! (This run of 503, and my last go at 205)... Go figure.
 
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