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31  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 28, 2016, 07:31:27 PM
The values are in Radians, scalings are provided too along with some values in the comments, which I can't confirm make any sense.

#    FOR LUNAR ORBITS 504LM VECTOR IS NEEDED:
019587,000077:                                                                                            #   504LM   2DEC   -2.700340600 E-5 RADIANS
019588,000078:                                                                                            #   504LM+2   2DEC   -7.514128400 E-4 RADIANS
019589,000079:                                                                                            #   504LM+4   2DEC    2.553198641 E-4 RADIANS

-----------
Additional info:

 #    ITEMS AVAILABLE FROM LAUNCH DATA
052436,000052:                                                                                            #      504M = THE LIBRATION VECTOR L OF THE MOON AT TIME TIMSUBL, EXPRESSED
052437,000053:                                                                                            #      IN THE MOON-FIXED COORD. SYSTEM      RADIANS B0
052438,000054:


* 504M above is actually 504LM , so it refers to the same thing. Also the VLOAD in the later code also refers to 504LM so I'm certain.

I've been unable to answer what TIMSUBL is to my satisfaction, however it isn't a symbol directly referenced in the code. The routines that use the 504LM vectors don't seem to use any similar value. However a routine to generate a transformation matrix for the moon IS called. This routine references TIMSUBO which is an alias for TEPHEM. So I presume that te 504LM libration vector should be for time at TEPHEM.

--------------------------

32  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 28, 2016, 07:26:47 AM
I've been working on changing the coordinate system of most of the calculations done by the RTCC and RTCC MFD. Lots of work, but I think for the better. When I have finished that work it might still be full of bugs, but I'll give my best at finding most of them.

The effort is most certainly appreciated. I hope you're doing your PhD thesis on this work or something Very Happy

Quote
One more piece of information for you Kneecaps. I honestly can't remember how I came up with the engineering unit for the lunar libration vector being radians and not revolutions like AX and -AY. So you might have to research the proper scaling for the octal AGC units. The two LM pad loads we have don't say anything about the engineering value; probably because the values for the libration vector technically aren't angles. We probably would get smaller values than the actual pad loads, because even with the updated Moon config it won't have a fully realistic libration movement.

Okay, an examination of the code and other docs should reveal the truth. Thanks for the heads up.
33  Project Apollo - NASSP / Programming / Re: Apollo RTCC MFD (Formerly Apollo Rendezvous) on: July 27, 2016, 10:55:15 PM
The most recent version of the manual is part of NASSP, under \Doc\Project Apollo - NASSP\Programmers Notes. It's not exactly a great manual, if you still have questions after reading it, then feel free to ask them here.

Thank you. The one place I didn't look Very Happy
34  Project Apollo - NASSP / Programming / Re: Apollo RTCC MFD (Formerly Apollo Rendezvous) on: July 27, 2016, 08:02:52 AM
RTCC Lambert options  and Pad Request?

Is there a newer manual for RTCC ? I can only find one from Aug 2015. Lots of new/different options in Lambert and the Pad by the looks of things.

I'm especially interested in the Request option on the PAD and also how the Multi-Axis / X only option is working (looks to replace the old manual Z offset method?)

35  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 25, 2016, 05:17:27 PM
The configs are used by all scenarios, but there should be close to no difference to the old configs without precession for Apollo 7 and 8. But if you only change the configs and pad loads, the RTCC won't be able to precisely find Earth/Moon latitude and longitude for later missions. That's why I said only Apollo 7 and 8 can be tested without the code changes I have already done.

Understood. 

Quote
Yeah, the epoch change is just one day worth of Earth's precession and the precession period is 25,800 years. So a really small difference, not even significant for state vector updates. However, I would still like to have all Colossus249 scenarios with updated ephemerides for this new epoch. Won't make too much of a difference, but let's be precise where we can.

Agreed.

Quote
Yes, I think I will use the approach that isn't dependant on a specific epoch. So instead of converting everything to BRCS coordinates and do the calculations with that, I'll change it so that it uses the J2000 ecliptic coordinates most of the time. Only converted from the left-handed system Orbiter uses to the more standard right-handed system.

Makes sense. The left handed system still catches me out sometimes when I forget that's what Orbiter uses....
36  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 24, 2016, 07:32:00 PM

You can do it that way, sure. As said before, it was all accurately configured for Apollo 7 and 8 before, so the new configs should not change too much for those missions. The updated epoch is rather insignificant. So if you only use the new configs combined with the new padload values, you should be able to test Apollo 7 and 8. For anything beyond that, you will need the new builds with the updated RTCC calculations etc.



Ah okay, I must be mis-understanding. I thought the Moon and Earth CFG files would affect all scenarios.

Just to confirm, the lunar and solar ephemerides are already correct in the A7 and A8 padloads, or they are incorrect but...the one MJD difference doesn't affect too much.

Quote

What I have been working is adding support for the different epochs. Unfortunately the C249 epoch has been hardcoded and used by quite a lot of RTCC calculations. Often these functions are based on AGC routines and require the equatorial coordinate system of the AGC. So I have two options:

-Add an AGC epoch parameter to almost half of all functions in the RTCC class. Lots of work and some logic will have to implemented to ensure that the correct epoch is always used. Sometimes two different epochs during the same mission for CM and LM.
-Remove all references to the AGC epoch in the basic orbital mechanics functions. That way it would become a more versatile set of functions, that also work beyond the time frame of the Apollo program. But I would have to change the coordinate system used in most functions, probably to the ecliptic system used by Orbiter. So that is not an easy task either.

Both ways are much more complicated than I anticipated. Thoughts?

I think the second approach makes more sense. Would a valid approach be to perform all calculations in the J2000 frame and then provide a function that converts J2000 to BRCS (passing appropriate arguments for epochs etc, SOI) etc? These values could then be transformed as needed into other systems? So perhaps RTCC could work internally in a more standard system and then it's outputs be in BRCS or other required system (much like the AGC working in Metric internally but displaying Feet and NM as needed).

I'm much more comfortable with the coding elements than I am the Celestial Mechanics so apologies if I'm not making sense.

 
37  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 23, 2016, 06:06:22 PM
@indy

Does this sound like a viable test plan? I'll validate the new values by testing the new moon and earth configs along with the new padload values by updating my master branch only. Once those are validated I'll build the branch with the RTCC changes and re test?

38  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 22, 2016, 05:45:01 PM
Do you have something to generate the Solar and Lunar ephmerides?

LTFMD works very well for that. It has an "AGC Ephemeris" option and will put a text file with the ephemerides already in octal format in your Orbiter folder. You just need to get the 3 MJDs for the ephemerides right. The first two are dependant on the AGC version. The epoch for C249 is 40221.525 (and not 40222.525 like the default option) and TEphemZero is midnight July 1st, 1968 (MJD 40038). The last MJD should be at the midpoint of a mission. Usually noon 7 days after launch was used, so e.g. MJD 41165.5 for Apollo 15. That number is from the backup padload in the G&C Checklist.

The other AGC versions have different Epochs and TEphemZero, because the coordinate system used is a Nearest Besselian Year system, valid for one year. Here the numbers for the AGC versions we have:

Nearest Besselian Year 1969 (Apollo 8 CM (unused), Apollo 9 CM)

Epoch: 40221.525
TEphemZero: 40038.0

Nearest Besselian Year 1970 (Apollo 11 CM, Apollo 11 LM, Apollo 13 LM)

Epoch: 40586.767239
TEphemZero: 40403.0

Nearest Besselian Year 1971:

Only Apollo 14, but we have no AGC version for this. I don't have the numbers for NBY 1971 right now.

Nearest Besselian Year 1972 (Apollo 15 CM)

Epoch: 41317.251625
TEphemZero: 41133.0

The different epochs aren't implemented yet for e.g. state vector updates. But when we have verified that the new configs plus the AGC correction angles for Earth and Moon are working correctly, then we can add the support for the different AGC epochs.

Thank you as always and apologies for my slow reply on this. I'm going to be working on this over the weekend. With the Wiki out of action would anybody object to us starting another Wiki for the time being? Perhaps just to document some of this 'advanced' navigation stuff ? Very Happy Trawling through the forum is vexing me Very Happy
39  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Anybody have admin access to the Wiki or Sourceforge? on: July 22, 2016, 05:42:28 PM
The wiki is on Ibiblio, and I have no special access there. I do have admin access to SF.


Hello, thanks for replying to this. Do you happen to have access to the Wiki itself at the moment? It's looking like we may end up having to almost 'screen scrape' the content to a new wiki. The MediaWiki version is so old it doesn't have the API which would permit me to export it properly. Sad
40  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 21, 2016, 12:02:45 AM

We don't need to generate completely new pad loads, all that needs to be changed in the launch scenarios, I think, is the AX/AY/AZO stuff, the L-Vector and the complete solar and lunar ephemerides. When I worked on the pad load stuff I also updated the worksheets, which you can find under \Doc\Project Apollo - NASSP\GNC Tools. The ephemerides are not correct in there. Also, don't bother with the non-LVDC scenarios, I don't think we need to update these anymore. The Apollo 7 and 8 scenario are in the main NASSP folder, the Apollo 9 scenario is under \Scenarios\Project Apollo - NASSP\Broken Scenarios\Virtual AGC.

Brilliant work, really brilliant!

Do you have something to generate the Solar and Lunar ephmerides?
41  Project Apollo - NASSP / Project Apollo - NASSP Development / Anybody have admin access to the Wiki or Sourceforge? on: July 20, 2016, 10:03:04 PM
The Wiki situation is now dire. The Wiki version is 10 years old (too old to be exported with any tools I know). I think the email may have stopped working because of php upgrades on the server at some point in the past.

Somebody with admin access should urgently take a backup. Then is there some way it can possibly be upgraded? That may fix the email issues. Failing that I can't see any other option but to export the data and import it elsewhere.
42  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 20, 2016, 08:51:40 AM
Okay good stuff Indy. I'm looking at the commit. I'll run a separate copy of orbiter with the modified CFG files. I need to read and digest the Orbiter forum thread you reference in your commit so I can really understand these parameters a little more on the Orbiter side of things.

Oh, that Orbiter Forum reference is from the normal Orbiter 2010 Earth and Moon configs, not me. I just copied them over. Before Orbiter 2010 was released, they worked out the rotational parameters for each body in that thread. Even with NASSP in mind. So we can almost use these Orbiter 2010 configs, with just a few small changes that I have made.

Also, the changes so far are more than just the configs, so you will need to build the development branch with Visual Studio yourself, to get the dll's. At least until BuildBot plays nice.

Ahh thanks for the clarification, it is a good thread though! I'll have to give the build a try tomorrow, late here and I'm not setup with Visual Studio (in fact haven't been since my last time here Very Happy. I have to re-familiarize myself with the build dependencies (.NET anything else?).
43  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 20, 2016, 08:21:35 AM
Okay good stuff Indy. I'm looking at the commit. I'll run a separate copy of orbiter with the modified CFG files. I need to read and digest the Orbiter forum thread you reference in your commit so I can really understand these parameters a little more on the Orbiter side of things.

44  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: Virtual AGC on: July 19, 2016, 06:06:20 PM
Anyone up for a Virtual AGC project? Kneecaps, what about you? You've stated you want to help with the Virtual AGC. It's not strictly speaking something required for Apollo 7 and 8, but for later missions. What I am talking about is nothing less than changing the NASSP Universe. Very Happy

The Earth and Moon config files we currently use are still pre-Orbiter 2010. In these files the rotational state of the bodies is defined, including things like rotation period, axial tilt etc. Before Orbiter 2010 was released, our configs were configured in such a way, that they are quite realistic for Apollo 7 and 8. These configs are what we are using right now. Orbiter 2010 introduced precession. This is especially helpful for the Moon, which has a very short precession period. I have done some analysis and if we want to use Earth and Moon config files that are accurate enough throughout the Apollo program and work with all AGC versions, then we need to do some changes. Right now our Moon is barely accurate enough to properly perform landmark tracking for Apollo 10. The Moon fixed coordinates where the CSM or LM actually are, are quite a bit off from what the AGC thinks. Here two graphs showing the difference between the AGC and the NASSP/Orbiter 2010 Moon. For this example the Apollo 11 landing site coordinates were used:



Theoretically I've already worked out most of the changes we need to do. For the Moon it is sufficient to use the config file that comes with Orbiter 2010, as you can see. Together with small padloaded correction angles it will be very accurate. So we can use the Orbiter 2010 parameters for NASSP. The Earth config from Orbiter 2010 can be used with two small changes, to the rotational offset and maybe axial tilt. A related topic is that our Colossus249 coordinate system is slightly wrong (one day worth of Earth's precession off, to be precise). I want to change this too. While it probably is an almost unnoticable change, it requires changes to PAMFD and RTCC MFD for state vector uplinks and any coordinate system calculations and also pad load changes for the solar and lunar ephemerides.

Git has a good workflow for these changes, we can simply create an independent development branch for it and if everything is changed, improved and most importantly tested, then it can be commited to the master branch, before or after a release. We don't have to hurry with these changes, but they are nice to have and I consider them required for the Apollo 9/10 release.

I'll need beta testers for this project. I would provide the changes to the code and a few pad load changes and testers would try everything in the Virtual AGC that is related to coordinate systems and landmarks/landing sites. So basically the programs P21, P22, P23, P52. Mostly P22 in Earth and lunar orbit I guess. We'll also need to create new solar and lunar ephemerides for the coordinate system, LTMFD is a good tool for that. After we have confirmed the changes to work for Apollo 7-9, I can introduce the different coordinate systems of Comanche055 and Artemis072 and whichever coordinate system our two LGC versions use. The Basic Reference Coordinate System of the AGC was only valid for a year, so there is a small but significant coordinate system difference between flights. Also, Artemis072 has fixed constants that were erasable pad loads in the earlier AGC versions, so this issue can't be fixed by loading an unrealistic, but functional pad load.

Great post. Yes this looks like something that is exactly up my street Very Happy. I had actually been thinking about the ability to create better pad loads and also the Artemis072 issue. I think it may be possible to actually provide an updated 'virtual rope' with any ephemerides that we care to include, but lets cross that issue later. I'm at work at the moment so will fully digest the post. I'd really like a working wiki again so we can document this stuff centrally (the forum makes a poor documentation system). But that said I'm really keen to work on this as it satisfies both my astro navigational and AGC interests Very Happy 
45  Project Apollo - NASSP / Project Apollo - NASSP Development / Re: What needs done? on: July 16, 2016, 07:45:50 PM
So I have most of the maneuver/navigation up to LOI finished and am about to fly it to LOI to test, however I cannot find a good resource on housekeeping such as cryo stir's or FC purging other than the voice transcript.  The two flight plans I have do not include these.  Anybody know of any documentation that has the appropriate/approximate times these were supposed to be done during the flight? 

Now I wouldn't stake my life on this but....prior to 13 , the stirs on H2 and O2 were fairly regular and routine. However after 13 I believe that stirs on the O2 tanks were not performed at all. I've taken a quick look through some of the Flight Journals for 14 and 15 and don't see any sign of stirs on O2. However I'm prepared to be proved wrong on this.

That said the flight journals could provide a realistic schedule, but the stirs were decided by EECOM procedures based on need. 
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