Support NASSP: P23 Program Explanation

thermocalc

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Hi, actually sorry to give you wrong information, but as I said your video worked for me as a tutorial and thanks to it and your latest comments I understood what I was doing wrong all times when using P23 with landmarks; also the real G&C checklists at page 20 of the document "A8-CMP checklist-1004" where it describes P23 helped me a lot to make progresses (sorry I don't know how to put a link to this file) but I am sure you should have come across this doc already....if not, I downloaded it in the "document sections" of the virtual AGC website under Apollo 8 documents....checklists....if I am not mistaken - don't remember exactly where).

If I do as you have done I got more or less the same problems … I end up floating over the Pacific near Venezuela coasts.... but looking at the G&C checklist I was puzzled by the fact that upon entering information in F 05 70 it never asked for the F 06 89 to enter LAT/LONG/2 and ALT … as far as I have understood, for landmarks sighting/marking in Earth orbit you need to enter LAT-LONG/2 and ALT when asked for, while in lunar orbit you may use some LMK codes stored into the AGC … for Apollo 8 there is only code 01 which is the pseudo landing site B-1 (I used it many times in P22 while in lunar orbit, while for CP-1, -2 and -3 I entered their coordinates as written on the flight plan)…so I suppose that setting 00110 in R2 is wrong, as the code #10 is not supported while in Earth orbit … this seems to be confirmed also by the original checklists, where for star/landmark it says to enter: R1 000DE, R2 00100 (Earth orbit), R3 00000; while in Lunar orbit it says to set for R2 002XX where XX is the stored AGC LMK code....the G&C checklist in the doc format is no clear about that....

ANYWAY, here what I did and it worked well.

After V37E 23E I entered on F 05 70 the following information: 00015, 00100, 00000, after PRO I got F 05 89 and I entered the coordinates of Punta Yoyameko = P.Y. in short (+29039 -56292 +00010), after PRO I got the auto-maneuver done and the LMK was there in the SXT (I had to use RCS in impulse mode to center it and KILL ROT to keep it steady … I know cheating a little bit here), than OPT CMC and in the SCT I got star 15, back to SXT, “V” and superimpose, after the mark I got again F 05 71 with 00015, 00100, 00000 and after PRO I got again F 05 89 with the old P.Y. coordinates … PRO and I got DR=+00053, DV=+00017, which I accepted!

I repeated all over again with star 16, 00016, 00100, 00000, this time the coordinates of P.Y. where already there, I move the CSM out of alignment to check if the auto-maneuver was finding the LMK again and it did…some story, small IMP jests, kill rot, star acquisition and marking and I got 000xx errors again.

Last I tried to mark another LMK: I did all over again, star 15 and P.Y. coordinates and when centered to P.Y. I manually moved out of alignment to see/center in the SXT Punta Parinas (LMK 110 on Apollo Earth Landmark document in the NASSP doc folder) … I center it into the SXT, kill rot again, than OPT CMC, star 15 in the SCT, back to SXT view, V, superimpose and mark. At F 05 71 still the same information: 00015, 00100, 00000, and when F 05 89 the old P.Y. coordinates where there, but I entered the new coordinates of Punta Parinas, -04699, -40664, -00253 PRO and I got a DR and a DV of the order of 000xx again.

So you can change the LMK coordinates later on, after the mark is done, you don’t need to stick to the original LMK entered at the beginning (I suppose this freedom is there as you don’t know in real life if the LMK will be visible or not, so you must have the possibility to change and mark a visible one…)....by the way the same is valid also during P52....if you mark another stars different from the one chosen when in F 05 50 as soon as you notify to the AGC in F 05 51 the new star code used in reality you alignment is still valid.

What is suspicious is why there is the possibility to enter a CODE (DE) in R2 while in Earth Orbit, but as said at the beginning the original checklist for P23 didn't allow this entry: so I am still puzzled, as after all it seems that entering the code 10 (I mean R2 00110) the AGC do something, it moves the CSM, but maybe the coordinates stored under code 10 are not the ones corresponding to Punta Yoyameko that’s why after the auto-maneuver we always end up in the middle of the pacific near Venezuela cost…maybe it simply means that we were not suppose to enter such kind of code ...

out of curiosity let’s see if some developers will tell us more details or if we are doing right or wrong this time :)

thanks.

Paolo
 
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STS

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Hello, here the promised videos.
On the first one, I show a P23 execution using earth landmarks, having into account the observations from @thermocalc . I load the coordinates from the flightplan:
28.876ºN
56.292ºW
Alt 000.01
I run, P23 2+1 times, as per the flighplan. (2 sets and 1 set)

On the second video I show the execution of P23 with Stars and Earth horizons. On the first execution I had a Program alarm, and I show how to solve it (didn´t wait 15 seconds for the zero optics).

I do three marks per set.

As you can see the results are great.


 

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Nice videos. Seems to prove the idea that you don’t need to have the cross-hairs on top of both the lmk/horizon and star to get good results.
 

thermocalc

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Dear STS I watched and re-watched your two videos but still cannot figured out what you are aiming for when firing the RCS jests in min impulse mode…what do you want to accomplishes when you fire them?

I was used to do P23 star/horizon in the following manner (a sort of my interpretation of all suggestions to do correctly P23 I found around on the forum) but I always get inconsistent results that make me thing I am still doing something not correct.

  • at the end of the CSM auto-maneuver I can see the center cross hair of the SCT pointing very near to the limb of the Earth (or Moon) , going in SXT view sometime the limb of the horizon (I mean the sharp curved arc-line separating empty black space to Earth/Moon texture) is very near the SXT center view, maybe really at the center, but sometime it is displaced from it (by eyes I would say from 1-2mm to as high as 10-15mm – not in the center of the SXT at all), and of course it keeps drifting slowly in some directions as there is no KILL ROT in the real DAP. As you know at this stage you have the code 59 asking you to take the 1st mark… at this point I am faced with two choices.
  • I just do the Mark (independently from the relative position of the horizon with respect to the SXT center – meaning that the center can point to the black space or the blue homeplanet/gray moon) and then go on with OPT-CMC to let the AGC acquire the star;
  • Or I could center the “limb of the horizon” with min impulse mode in the SXT view before to take the mark.
  • Looking at your videos it seems to me you don’t bother where the actual horizon is “relatively to the center SXT view” at this stage, I suppose you just mark it at the end of the auto maneuver and then let the AGC find the star, so you follow the philosophy of step 2 above. Am I right here?
  • Once the star is found and centered into the SCT, moving to the SXT view and hitting the “V” key to superimpose it to the limb of the horizon what is still not clear to me is why are you firing sometime the RCS thruster in min impulse mode? Is it to bring the limb of the horizon to the center of the SXT view? So that the horizon is there at the center and after that, you “lower” the star close to it? But it seems to me you are not doing exactly like that…so I am attempted to say, if the relative position between the SXT center view and the limb of the horizon is not important but all you have to do is to lower the star to the horizon (independently from where the horizon is in the SXT view or with respect to the SXT center view) what are you aiming/looking for when moving the spacecraft by firing jets? What “visually” you want to see/achieve in the SX view? Do you want to see (bring) something in the SXT center view before to take mark? If so what? The limb of the horizon before lowering the star? The star and then lower it to whatever the horizon will go due to the jet firing or you don’t care at all to see “thing” in the SXT center?
  • I tried many combinations of the different steps above, sometimes I got DR,DV values of the order of 0000x “a la Lowel”, but sometime as high as 00xxx (maybe 00650 or even 00800), but if I stick to a specific procedure (way to take the mark) that gave me low values once, repeating the same procedure at a later time it gives me huge values, so it means maybe there is something else I have to take care or maybe I am still doing something wrong…but still cannot figured out…even after watching you nice videos.
Could you be so kind once more time to share your own “way to do the sighting” and tell me which steps described above are wrong, useless, not necessary or irrelevant to get a good mark score?

Thank you for you cooperation.

Paolo
 

STS

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Dear STS I watched and re-watched your two videos but still cannot figured out what you are aiming for when firing the RCS jests in min impulse mode…what do you want to accomplishes when you fire them?

I was used to do P23 star/horizon in the following manner (a sort of my interpretation of all suggestions to do correctly P23 I found around on the forum) but I always get inconsistent results that make me thing I am still doing something not correct.

  • at the end of the CSM auto-maneuver I can see the center cross hair of the SCT pointing very near to the limb of the Earth (or Moon) , going in SXT view sometime the limb of the horizon (I mean the sharp curved arc-line separating empty black space to Earth/Moon texture) is very near the SXT center view, maybe really at the center, but sometime it is displaced from it (by eyes I would say from 1-2mm to as high as 10-15mm – not in the center of the SXT at all), and of course it keeps drifting slowly in some directions as there is no KILL ROT in the real DAP. As you know at this stage you have the code 59 asking you to take the 1st mark… at this point I am faced with two choices.
  • I just do the Mark (independently from the relative position of the horizon with respect to the SXT center – meaning that the center can point to the black space or the blue homeplanet/gray moon) and then go on with OPT-CMC to let the AGC acquire the star;
  • Or I could center the “limb of the horizon” with min impulse mode in the SXT view before to take the mark.
  • Looking at your videos it seems to me you don’t bother where the actual horizon is “relatively to the center SXT view” at this stage, I suppose you just mark it at the end of the auto maneuver and then let the AGC find the star, so you follow the philosophy of step 2 above. Am I right here?
  • Once the star is found and centered into the SCT, moving to the SXT view and hitting the “V” key to superimpose it to the limb of the horizon what is still not clear to me is why are you firing sometime the RCS thruster in min impulse mode? Is it to bring the limb of the horizon to the center of the SXT view? So that the horizon is there at the center and after that, you “lower” the star close to it? But it seems to me you are not doing exactly like that…so I am attempted to say, if the relative position between the SXT center view and the limb of the horizon is not important but all you have to do is to lower the star to the horizon (independently from where the horizon is in the SXT view or with respect to the SXT center view) what are you aiming/looking for when moving the spacecraft by firing jets? What “visually” you want to see/achieve in the SX view? Do you want to see (bring) something in the SXT center view before to take mark? If so what? The limb of the horizon before lowering the star? The star and then lower it to whatever the horizon will go due to the jet firing or you don’t care at all to see “thing” in the SXT center?
  • I tried many combinations of the different steps above, sometimes I got DR,DV values of the order of 0000x “a la Lowel”, but sometime as high as 00xxx (maybe 00650 or even 00800), but if I stick to a specific procedure (way to take the mark) that gave me low values once, repeating the same procedure at a later time it gives me huge values, so it means maybe there is something else I have to take care or maybe I am still doing something wrong…but still cannot figured out…even after watching you nice videos.
Could you be so kind once more time to share your own “way to do the sighting” and tell me which steps described above are wrong, useless, not necessary or irrelevant to get a good mark score?

Thank you for you cooperation.

Paolo

Sorry, I haven´t checked this thread until now.

I will process what you posted and give you an answer soon.
 

thermocalc

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HI, thanks for your reply.
No worries, I also checked the post only now, during the last few weeks I was (and still I am) quite busy with real life/family issues to deal with , so not sure when I may have again time to restart my missions .... hopefully sometime next week :-(
Paolo
 

Giuse101

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Hello, what can I do if the horizon is dark at that time? and it's impossible to define the horizon
 

Giuse101

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And another problem I ran into is that the automaneuver 99% of the time sets the SCT in a position that is not the correct one, so I have to maneuver manually and then mark. Is that the correct procedure? Then well I have the problem with the night time horizon.
 

MrFickles

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And another problem I ran into is that the automaneuver 99% of the time sets the SCT in a position that is not the correct one, so I have to maneuver manually and then mark. Is that the correct procedure? Then well I have the problem with the night time horizon.
If the horizon is on the dark side, you can try switching horizons. Instead of the near horizon, you use the far horizon and vice versa.

As for the automaneuver not pointing the telescope in the correct position, is your telescope zeroed? It should be pointed at the substellar point after automaneuver.
 
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