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Author Topic: P51 problems with star selection  (Read 1643 times)
meik84
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« on: June 30, 2010, 12:39:43 PM »

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you can start over using P51/52
Does your P51 work? Mine is doing garbage -I get star angle differences beyond good and evil. But rapid IMU realign with V41N20 works out. By the way: the resp. procedure in the word-checklist is erroneous: do not use V40N20E (this would zero the IMU again), instead use V42E, E, E, E; continue with the rest.
Edit: digged around in the flagwords a little bit: neither REFSMMAT (this causes the 210-error) nor DRIFT flag are set. Did you enter P06 accidentally? Or V36?

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« Last Edit: November 11, 2010, 12:49:31 PM by Tschachim » Logged
Tschachim
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« Reply #1 on: July 01, 2010, 04:13:28 AM »

Does your P51 work? Mine is doing garbage -I get star angle differences beyond good and evil.

No, not with this scenario and Orbiter 2010, star difference of about 60° Shocked , I didn't test P51 with the launch scenario since some time, so I hope we don't have a new bug here. I'm still working on the Orbiter 2010 changes and some bugfixes, I'll try to test P51 with the Apollo 7 launch scenario before a new beta...

Thanks for checking the flagwords, I was too lazy for that, I'm still puzzled what happend in this scenario...

Cheers
Tschachim
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meik84
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« Reply #2 on: July 01, 2010, 08:02:22 AM »

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so I hope we don't have a new bug here
Bad news -I guess we have. I've not tested it 'from scratch' (the original launch scenario), instead I used a quicksave which is set short after orbit insertion, but even with this 'clean' scenario P51 is doing garbage -P52 works fine, though. This is no Orbiter 2010 problem, I'm still using the old 2006 version...
Quote
Thanks for checking the flagwords, I was too lazy for that, I'm still puzzled what happend in this scenario...
As I said: P06 or V36 inadvertently selected. I know what I'm talking about -killed my CMC this way (P06) the first time I went into orbit with NASSP... Ashamed
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Tschachim
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« Reply #3 on: July 02, 2010, 09:10:48 AM »

Bad news -I guess we have. I've not tested it 'from scratch' (the original launch scenario), instead I used a quicksave which is set short after orbit insertion, but even with this 'clean' scenario P51 is doing garbage -P52 works fine, though. This is no Orbiter 2010 problem, I'm still using the old 2006 version...

I can't remember using P51 myself, but it looks like the problem happens at least sometimes (but not every time) since some time:

http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=2067.0
http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=1938.0

I'll try to take a look, but any infos, personal experiences or comments about P51 are very welcome, I've no clue why this happens...

Cheers
Tschachim
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Tschachim
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« Reply #4 on: November 10, 2010, 11:34:32 AM »

Just for the record, as mentioned here: http://www.ibiblio.org/mscorbit/mscforum/index.php?topic=491.msg20281#msg20281, it's a "user error":

The problem with P51 is either that the angular difference between the 2 stars is greater that 66° (see Colossus source code) or the trunnion angle (as I figured out by testing) of either star is greater than 60°.
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meik84
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« Reply #5 on: November 10, 2010, 05:01:43 PM »

I.e. the best way to do P51 is to pick 2 stars which 1. are as close to each other as possible and 2. not to far away from the zero position of the SXT? Good to know that. Interestingly, neither GSOP nor AOH waste any words about that.
« Last Edit: November 10, 2010, 05:03:32 PM by meik84 » Logged
Tschachim
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« Reply #6 on: November 11, 2010, 01:04:41 PM »

Well, yes and no, if the stars are very close to each other, the resulting data are less precise. The only reference I know is the Colossus source code itself:

# Page 711
# PROGRAM NAME -- PICAPAR   DATE: DEC 20 66
# MOD 1            LOG SECTION: P51-P53
#            ASSEMBLY:  SUNDISK REV40
# BY KEN VINCENT
#
# FUNCTION
#   THIS PROGRAM READS THE IMU-CDUS AND COMPUTES THE VEHICLE ORIENTATION
#   WITH RESPECT TO INERTIAL SPACE.  IT THEN COMPUTES THE SHAFT AXIS (SAX)
#   WITH RESPECT TO REFERENCE INTERTIAL.  EACH STAR IN THE CATALOG IS TESTED
#    TO DETERMINE IF IT IS OCCULTED BY EITHER EARTH, SUN OR MOON.  IF A
#    STAR IS NOT OCCULTED THEN IT IS PARIED WITH ALL STARS OF LOWER INDEX.
#    THE PAIRED STAR IS TESTED FOR OCCULTATION.  PAIRS OF STARS THAT PASS
#   THE OCCULTATION TESTS ARE TESTED FOR GOOD SEPARATION.  A PAIR OF STARS
#   HAVE GOOD SEPARATION IF THE ANGLE BETWEEN THEM IS LESS THAN 66 DEGREES
#   AND MORE THAN 40 DEGREES.  THOSE PAIRS WITH GOOD SEPARATION
#   ARE THEN TESTED TO SEE IF THEY LIE IN CURRENT FIELD OF VIEW.  (WITHIN
#   33 DEGREES OF SAX).  THE PAIR WITH MAX SEPARATION IS CHOSEN FROM
#   THOSE WITH GOOD SEPARATION, AND IN FIELD OF VIEW.

As you can see, the angular difference between the 2 stars should be 40°-66°, a rather tight margin. Greater than 66° isn't working at all, but smaller than 40° is at least possible (i.e. no errors) however less precise.

Also, in reality the max. field of view = max trunnion angle seems to be 33°. We don't have that restriction, but for trunnion angles greater than 60° P51 isn't working anymore. This restriction is irrelevant in reality obviously, so it isn't denoted in the docs I suppose.

Cheers
Tschachim
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meik84
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« Reply #7 on: November 11, 2010, 05:13:36 PM »

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Also, in reality the max. field of view = max trunnion angle seems to be 33°. We don't have that restriction
Then we should have it. You can't display the OCDU angles when you are in R53, so from what should we know that we're out of limits?
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Tschachim
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« Reply #8 on: November 15, 2010, 10:01:44 AM »

OK, I've put it on my list...  Happy
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Tschachim
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« Reply #9 on: August 10, 2012, 01:57:51 PM »

A little bit late, but I added a limit of 59° (so it's "really smaller" than 60°) for manual trunnion control, change is in CVS.
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meik84
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« Reply #10 on: August 13, 2012, 05:45:53 PM »

No luck. I still can cause P51 to do garbage. No I'm just wondering, but why can I see a star when I'm in the 'full left' position as well as in the 'full right' position?
Oh, just one thing: the PGNCS light in the LEB does not trigger a master alarm. It has nothing to do with the CWS, it's not more then an OR link of the TEMP, GIMBAL LOCK, PROG and RESTART lights of the LEB DSKY. The only ways the CMC can trigger a master alarm is via the CMC and ISS WARNING "pins".
« Last Edit: August 13, 2012, 06:16:26 PM by meik84 » Logged
Tschachim
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« Reply #11 on: August 14, 2012, 03:53:41 AM »

You still need to make sure that the angle between the stars is smaller than 66°, perhaps this was the problem? Also, I only introduced a trunnion limit (up/down), no shaft limit (left/right). AFAIK there's no shaft limit.

Do you have a reference for the PGNCS not triggering a master alarm by chance?  Happy
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Tschachim
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« Reply #12 on: August 14, 2012, 03:57:19 AM »

As you can compile the modules by yourself: You can go to void CMOptics::TimeStep(double simdt) and change the trunnion limit to 33° (look for "(RAD*59.0)" and change it to "(RAD*33.0) or (RAD*32.9)") and try again, in this case the max. star angle can't be bigger than 66° I think...
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meik84
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« Reply #13 on: August 14, 2012, 04:23:58 AM »

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You still need to make sure that the angle between the stars is smaller than 66°
Interestingly, it seems to be better to mark on stars which are very close to each other then on stars which are more distant from each other. And even more interstingly, P52 is happy with it -it pinpoints the stars perfectly! Confused
Quote
Do you have a reference for the PGNCS not triggering a master alarm by chance?
Here->http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730060780_1973060780.pdf, pp. 238/239 and 278/279: only CMC and ISS warning lights are wired in the MA trigger circuit, PGNCS isn't (it's not even in the schematics of the CWS). P. 399 shows that it's simply activated by the paralleled contacts of the switching relays for the DSKY lights and does not have any connection to the CWS.
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Tschachim
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« Reply #14 on: August 15, 2012, 12:40:42 PM »

As you can compile the modules by yourself: You can go to void CMOptics::TimeStep(double simdt) and change the trunnion limit to 33° (look for "(RAD*59.0)" and change it to "(RAD*33.0) or (RAD*32.9)") and try again, in this case the max. star angle can't be bigger than 66° I think...

Forget about that, P52 picks stars with a trunnion angle greater than 33°, just had one with 37°. EDIT: new "record" 45° Happy

Interestingly, it seems to be better to mark on stars which are very close to each other then on stars which are more distant from each other. And even more interstingly, P52 is happy with it -it pinpoints the stars perfectly! Confused

As I said, they need to be closer than 66°. P52 seems to have at least less problems with bigger angles, but I don't know why, I still can't read AGC code.  Ashamed

Thanks for the PGNCS CWS stuff, I'll fix it.

Cheers
Tschachim
« Last Edit: August 15, 2012, 02:04:05 PM by Tschachim » Logged

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