SupportNASSP: P23 Program Explanation

Sverige

Member
I think I understand program 22 pretty well now. My next problem is program 23. Can anyone explain how to do? First, which star, landmark and horizon field I will choose? what is the difference in a landmark and horizonmark and where do I find horizonmarks. I am also expected to carry out a superimpose, star and landmark. How should I do this? As you can see, I have many questions, and I'm sure I do not really understand the procedure. Please help me!

Mikael

MrFickles

Active member
First, which star, landmark and horizon field I will choose?
The star/landmark/horizon to choose is on the flight plan. I don't recall any landmark sightings used on P23, maybe on Apollo 7 but I can't remember. Apollo 8 onwards only uses horizon sightings during the translunar coast.

what is the difference in a landmark and horizonmark and where do I find horizonmarks
Landmarks are points on the surface of either the Earth or Moon used for sightings.

There are 2 types of horizon used in P23, near or far horizon.
If you imagine a straight line from the star passing through the center of the earth/moon, the near horizon is where the line intersects with the horizon, the far horizon is on the opposite side of the body.

White dot is the near horizon. Pink dot is the far horizon.

I am also expected to carry out a superimpose, star and landmark. How should I do this?
Ensure you have a proper IMU alignment first, otherwise use P51 and P52 to align the IMU.
When entering P23, enter the star, landmark, horizon that will be used for the sighting.
V05 N70
R1 000AB
R2 XXC00
R3 XXCE0

AB = Star code
C = Earth (1) or Moon (2)
E = Near horizon (1) or Far horizon (2)

If you are using landmarks, R3 must be set to 00000. If using a horizon, R2 must be set to 00000.*

Hit PRO on the DSKY.

If you're using a horizon sighting. (R3 not 00000) skip this:
V06 N89
R1 +XXXXX (Latitude of landmark)
R2 +XXXXX (Longitude of landmark divided by 2)
R3 +XXXXX (Altitude of landmark)

Enter all the info and hit PRO

V50 N25
R1 00202
R2 (blank)
R3 (blank)

Hit PRO

V50 N18 (I'm sure you know how to let the AGC perform an auto maneuver, so I'll skip this part)

Once the CSM is in the correct orientation, hit ENTR.

V51 N(blank)
R1 (blank)
R2 (blank)
R3 (blank)

Zero your optics and take a look through the sextant, make sure it is pointed at whatever landmark or horizon you're taking sightings with. Hit MARK.

V06 N87
R1 (blank)
R2 +XXXXX (shaft angle)
R3 (blank)

Hit MARK again to update R2 if required. Otherwise, hit PRO.

V51 N(blank)
R1 (blank)
R2 (blank)
R3 (blank)

Switch the optics mode to CMC and allow the optics to slew to the star used for sightings. Switch to the sextant view and hit 'v' on your keyboard. You should see the view rapidly switch between the earth/moon and the star used for sightings. Use the WASD keys to move the view such that the star and the landmark/horizon are on the same part of the scope. (They don't have to be in the center of the scope. They don't even have to be on the scope for that matter...)

Blue circle is the body used, white dot should be where both the star and the landmark/horizon is.

Hit MARK.

V50 N25
R1 00016
R2 (blank)
R3 (blank)

Hit REJECT to return to the previous page and take the mark again. Otherwise, hit PRO.

V05 N70
R1 000AB
R2 XXC00
R3 XXCE0

Ensure the info is correct. Hit PRO.

V06 N49
R1 +XXXXX (delta R)
R2 +XXXXX (delta V)
R3 (blank)

Same page as on P22. Hit PRO to update state vector.

V37 N(blank)
R1 (blank)
R2 (blank)
R3 (blank)

Thats the end of the program. Hit 00 to return to P00.

EDIT:
The last picture is not 100% accurate. In order to find the substellar point of the Earth/Moon to the selected star, you'll want to place the star on the top or bottom tangent point of the body. (Either the highest part or lowest part of the body when looking through the sextant depending on whether near or far horizon is used)

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Sverige

Member
Thank you for this amazingly comprehensive response. This was just what I needed. :tiphat:

Mikael

---------- Post added 07-06-18 at 08:07 AM ---------- Previous post was 07-05-18 at 06:55 PM ----------

For those using NASSP v8 and orbiter 2016 running apollo 7, this document may be of great help when running programs 22 and 23.

https://www.ibiblio.org/apollo/Documents/A8-Landmark maps+photos-1004.pdf

Mikael

Sverige

Member
After practicing many times on P22 and P23 I still wonder how I know when I have succeeded. What is meant by

V06 N49
R1 +XXXXX (delta R)
R2 +XXXXX (delta V)

What does delta R and delta V mean and what should I expect and what are optimal numbers? Thanks!

Cheers
Mikael

indy91

It's a bit more complicated than that, but basically those numbers are how much you would be changing the onboard state vector in position (R) and velocity (V) by incorporating the data from the mark you did into the state vector. So that of course makes the optimal numbers +00000 and +00000. Even with perfect accuracy it would take a few marks to achieve that. And due to various reasons you probably can't achieve perfect accuracy in Orbiter anyway. The Apollo 8 CMP Checklist suggests to only incorporate the data when both DR and DV are smaller than +00500. Really good values that have converged after a few marks would be something with +0000X, but that is quite difficult to achieve.

On that display (V06 N49) you have to press PRO to allow the state vector being updated or do V37E XXE to reject it. Either starting P23 again there to try another mark or P00 to stop the marking sequence.

Sverige

Member
Thanks, now I understand a little more about the importance of V06 N49 and what the numbers say. I tend to be well below +00500.

/Mikael

Petter

New member
Split screen

Hi !

I'm sure I'm missing out some tiny detail somewhere, but when I press "v" to activate the split screen nothing happens. If I start to move the opitcs around the earth, stars etc. starts to "jump up and down" (I'm sure there is a better description of this behavior somewhere).

Any inputs to what might cause this?

Best regards
Petter

Thymo

I like breaking things
That's the split line of sight from the optics.
With the real optics you could use that to superimpose the star on the horizon.

Orbiter doesn't support this, so as a work around the line of sight gets switched every other frame.

Mojave

60% Ethanol
Moderator
O-F Staff Note: Changed name of thread to elaborate topic, and make it easier for the OP to receive aid from NASSP users.

Cavalier

New member
V51 N(blank)
R1 (blank)
R2 (blank)
R3 (blank)

Zero your optics and take a look through the sextant, make sure it is pointed at whatever landmark or horizon you're taking sightings with. Hit MARK.

Ok, hopefully this will be simple enough.

When I get to this step, the SCT can not be manipulated, so does the horizon need to be centered crosshairs, or does the correct horizon just need to be generally in view? With it just generally in view, I'm lining the star up nicely on the horizon as noted further on, but the deltas are failing. Any thoughts?

Thymo

I like breaking things
You need to center both the star and the horizon in the crosshairs.
Use normal optics to point at the star and then switch to SLOS and maneuver the horizon to the center with RCS.

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Cavalier

New member
I do thank you for you're very Mission-controllesque response, i.e. *smak! head lolls forward into the FDAI 1 witha resounding thud* "You know better then that! Why'd they even let you into this program! *walking away* "ROOOKIIIEEES!

No, much better, your response makes great sense, and yet I take the plunge: I have the Earth's horizon parallel to the M line (I think it's the M line), and now I can use the optics to bring that misbehaving star right to the cross-hair, BANG! But, hm, the Substallar point should be a line drawn straight from the star to the center of the Earth. So.
Is it still a valid entry, or do I need to maneuver between Earth and the star so that the line from the star passes straight though my reticent before crabbing the star over with the optics for the mark? Sorry, my full training team is working on the Apollo 21 launch, and have no time to explain such trivial questions.

STS

Well-known member
Hello. I am practising Apollo 8 procedures, using Nassp 7.
I am having difficulties when it comes to perform the first P23´s using Earth Landmark 10.

On this video, I show you that I do all the steps correctly, as I understand. For some reason, after entering the codes, the AGC switches directly to F50 25 (R1 00202) instead of F 06 89 with the coordinates. Is this correct as per the Apollo 8 AGC software version?

If I follow the steps, my sextant always ends up on south america, instead of mexico. I also have difficulties to align the star with a landmark for example 110.

You need to center both the star and the horizon in the crosshairs.
Use normal optics to point at the star and then switch to SLOS and maneuver the horizon to the center with RCS.

I just read this. Do I need to move the spacecraft using RCS?

What exactly am I doing wrong?

kuddel

Donator
Donator
A flashing verb 50 noun 25 is used to indicate a checklist option to the user... checklist number is in R1.

STS

Well-known member
Yeah, there it´s requesting the 3D maneuver to the crew.
But what I was asking there, is if that is correct or if instead it should show F 06 89 with the landmark coordinates, as per the word G&C Checklist.

thermocalc

Active member
Hi not sure if you have already figured out by yourself, but as far as I understood looking at your video (GREAT BY THE WAY....nice tutorial) you entered the LMK code 00110 and the star 15, but later on when you superimpose the start 15 on the LMK, i saw that you put it onto the LMK with code 209 (if I am not mistaken) ... and then when you get back to the flushing verb and noun 71 to confirm the mark you took you still have star 15 in R1 and LMK code 110 in R2 .... I think you should load at that point the LMK code that you indeed marked and not the one that you were aiming for , the 110 .... but as I said, I didn't try by myself to prove that I am correct .... actually when I was running the simulation of A8 at the same stage I saw somewhere (maybe flight plan? can't remember) start 15 and LMK 10 ..... so I entered 00015 / 00010 / 00000 ... but than I NEVER saw the LMK number 10 showing up and I didn't know what to do, so I just skip that sighting.....later on somebody told me about the possibility I mentioned to you, but I still didn't tried it.
kind regards, Paolo

thermocalc

Active member
actually, if I may ask, it would be possible for you to put also a similar video for P23 when you have to mark a star and an horizon ??? as you know during TLI and TEI there are a lot of marks to do but I always got troubled results with DR and DV .... sometimes 0000x and sometime even more than 00600 with all possibilities in between .... but I could not figured out WHEN i got good and bad results .... so I still cannot understand "which is the correct rule" to use to get consistent results ... maybe if you are so kind to show in a video the correct procedure (where and when to manually control the spacecraft before taking the mark, or which kind of alignment "tricks" are you using to ensure you are correctly aligned before taking the mark.....) I think it would be extremely useful.....I red a lot of posts about P23 but still cannot figured out when I do correct and when not ... anyway, sorry to bother you with this request....please forgive/excuse me if I asked too much....but a video would be worth of many words and posts

thermocalc

Active member
actually sorry again, I rechecked you vdieo, I think you superimpsoe the start 15 to the LMK 210, but when F05 71 you still has in R2 the old code 110 .... so surely if you load V22E 00210E I think you Dr and Dv should be much less than before.

STS

Well-known member
Well, first of all the video I posted is not intended to be a tutorial, it´s an illustration on my experience on running P23 with earth landmark.

At F 05 70 (step 4) I entered R1 15 and R2 110 because as per the flightplan we have to use Star 15, Earth landmark 10, and as per the word G&C checklist I am entering 001DE (1 for Earth, 2 for Moon):
4 F 05 70 R1 000DE STAR ID

R2 00CDE LMK ID

R3 00CD0 HOR ID

STAR/ENH STAR/LNH STAR/EL

000DE 000DE 000DE

00000 00000 001DE

00110 00210 00000

STAR/EFH STAR/LFH STAR/LL

000DE 000DE 000DE

00000 00000 002DE

00120 00220 00000

I superimposed the star with landmark 209 because that is the only nearby landmark I could see on the sextant, and the only one I could maneuver it to. I expected to see on my sectant the landmark 10, that is the reason I was asking why my sextant / scanning telescope always pointed to south america instead of mexico. Do I need to maneuver the spacecraft after it auto maneuvers to the required attitude?

Didn´t try to change the landmark code after the mark sequence. Will see what happens.

For P23 with stars and horizon options, the posts above helped me a lot. Will do a video about it. The required values, as stated on earlier posts and as on checkist MFD and Apollo 8 CMP checklist, should be below 00500

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