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Author Topic: AGC Mission Time  (Read 2688 times)
ADT
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« on: November 19, 2009, 10:32:22 AM »

Hi Guys, I have a small problem thought I would ask for some advice!

Have been running an Apollo 8 scenario using the latest flight plan over a period of weeks, by saving the flight every few hours. Came to do the final MCC using the SPS, and always got TIG +59 59 when running P30, even though the GET input was for less than 1 hour ahead. I thought that there might be a discrepancy between elasped time in the AGC and the mission timer. Sure enough they appeared to be off by about 36 hours. I then tested the theory by using my GET calculated for P30, minus 36 hours and got the result I was expecting, TIG -45 etc.

My question is: Is it possible to manually update the clock, either through the .scn file or the AGC itself?

Kind Regards,

Alex
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irnenginer
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« Reply #1 on: November 19, 2009, 12:33:12 PM »

An interesting issue. I wonder if its a bug. Based on your saved states did it happen once or has it been getting progressively worse over time?

To fix it:
There is a way to increment the clock using V73 but it requires a lot of math in octal to do. The easiest fix is to fix the clock in the scenerio.

Go to the CMC Update Spreadsheet and enter in the Apollo8 8 LAUNCH MJD and the Current MJD into the 1_State Vectors Page
record the value in EMEM1516 and 1517
Go into the scenario and edit lines

EMEM0024  [Value from EMEM1516]
EMEM0025  [Value from EMEM1517]

That should fix the time. You should do a state vector update to fix any issues with the sate vectors. Check the time V16N36E

If that does not work let me know. 
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Tschachim
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« Reply #2 on: November 19, 2009, 12:57:17 PM »

You can use ProjectApolloMFD for clock update, too, similar to the state vector update, click on TELE, then CLK and follow the on-screen checklist.

But I also wonder why there is this huge discrepancy at all. Did you turn off the AGC during the mission?
If not, do you use the multi-threading option for the AGC?

Cheers
Tschachim
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ADT
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« Reply #3 on: November 19, 2009, 03:32:25 PM »

Tried using ProjectApolloMFD and worked perfectly!
Yeah, I think I did pull the cb's before to allow a little time accelleration. Guess that would cause the clock to reset!   Duh!

Thanks for your help!
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ADT
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« Reply #4 on: November 21, 2009, 11:26:16 AM »

Something strange has ocurred...... What?

Carried out the uplink as described above, times all updated perfectly. Now came to run P30 and get a PROG light every time. Tried to run the alignment programs as well with the same result. Any ideas?

Haven't got time now but will try a computer reset and manual state vector update when I get the chance.
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irnenginer
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« Reply #5 on: November 21, 2009, 12:48:06 PM »

Did you try a state vector update after the time update?
Also do a V05N09E to see what the error is
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Coussini
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« Reply #6 on: November 21, 2009, 02:00:25 PM »

You can try the Checklist MFD too. it's provide the Mission Elapsed Time (MET) using MET button

See the next post

http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=1459.msg18780#msg18780





* CHECKLIST.jpg (30.28 KB, 356x301 - viewed 188 times.)
« Last Edit: November 21, 2009, 02:02:36 PM by Coussini » Logged

Have a nice day
ADT
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« Reply #7 on: November 22, 2009, 06:58:31 AM »

Thanks for your input guys.

Did a manual state vector update right after correcting mission time, and still getting program alarms. Alarm code is: 01520

Will try a CMC restart next, see if that helps!
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irnenginer
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« Reply #8 on: November 22, 2009, 06:24:13 PM »

1520 is "V37 not allowed at this time". Usually a few seconds and it will let you do it. The fact that is sustained is interesting. You might post the scenario sometime for some looking into what might be going on.

I think for you doing a restart may be the quickest way to get going again.
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ADT
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« Reply #9 on: November 27, 2009, 06:35:01 AM »

Sorry for not posting this for a few days. Normal life intervened somewhat.

The scenario contains the conditon after completing both clock and state vector updates, and getting the 'V37 not allowed' error.

Am home for a few days now so will try the CMC restart procedure.

Thanks again!

* Apollo 8 - CMC FAULT 2.scn (73.84 KB - downloaded 129 times.)
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ADT
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« Reply #10 on: November 28, 2009, 10:36:57 AM »

Yet another strange occurrence! Attempting to restart the CMC, and following the steps detailed in AP8 mission flight plans, I get hung up at coarse alignment of the ICDU's. The NO ATT light will not extinguish maybe due to my misunderstanding the procedure steps, but equally might be due to the issue above!
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