Apollo 15 Post Orbital Insertion Procedures Question

rcflyinghokie

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No! I didn't know those existed. I'll get that done.

I misspoke, I did run P68 (V37E N68E), and that's the LAT/LON I get.
Ah ok just checking! Check your landing site using RTCC landing site update page and compare to P68
 

Wedge313

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OK so looking at my current visual it looks like I'm inside the the rille, on the west side. P68 F 06 43 gives me 02607 and 00365. The RTCC landing site update page gives me 26.074 and 3.654 initially, and 26.078 and 3.586 after I hit CLC. On the LROC map I'm using that has me inside the rille on the east side.

Is this an alignment issue? My last P52 went well, with a .00000 angle diff. And I did the LM SV uplink. Where could I have gone wrong here?

Thanks.
 

rcflyinghokie

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OK so looking at my current visual it looks like I'm inside the the rille, on the west side. P68 F 06 43 gives me 02607 and 00365. The RTCC landing site update page gives me 26.074 and 3.654 initially, and 26.078 and 3.586 after I hit CLC. On the LROC map I'm using that has me inside the rille on the east side.

Is this an alignment issue? My last P52 went well, with a .00000 angle diff. And I did the LM SV uplink. Where could I have gone wrong here?

Thanks.
So the LGC landed more or less where it thought it was targeted, which is a good sign. However Apollo 15 had a bunch of retargeting done which probably is why you landed where you did. Nothing went wrong, per se, you just never updated your landing site or targeting (N69) during PDI like the actual landing. And you had no direction to do so without reading into a lot of targeting documentation so you did nothing wrong based on the information you had.

EDIT: Upon looking at the locations, your LM landed long compared to the target site from RTCC MFD. Did you update your landing site vector and/or TLAND in the LM?
 

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Wedge313

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OK. Like I said after the first landing, at pitch over the LPD had me aimed into the rille (which apparently I was!), and I pitched back quite a bit to stay on the east side. That's when I picked up the large aft velocity, I was trying to work out what the LPD was trying to tell me vs what I had expected to see and I let it get away from me.

I'll try it again, this time I'll re-designate less aggressively and try to land to the east of the rille, and press on from there. I had plenty of fuel the first time, even after I put on the airshow maneuvering I touched down with 6% remaining.

Thanks again.
 

rcflyinghokie

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OK. Like I said after the first landing, at pitch over the LPD had me aimed into the rille (which apparently I was!), and I pitched back quite a bit to stay on the east side. That's when I picked up the large aft velocity, I was trying to work out what the LPD was trying to tell me vs what I had expected to see and I let it get away from me.

I'll try it again, this time I'll re-designate less aggressively and try to land to the east of the rille, and press on from there. I had plenty of fuel the first time, even after I put on the airshow maneuvering I touched down with 6% remaining.

Thanks again.
Did you update RLS and TLAND before PDI?
 

rcflyinghokie

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I remember having similar issues when I flew 15, would you mind posting a pre PDI scenario so we can look at it?
 

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OK....I think I got this ironed out. Kind of a two-part solution as you thought.

Part 1: You were correct that I hadn't uplinked the RLS to the LGC, I thought that was an AGS-only input (240 input 231 PAD). So I after uplinking the SV, in the RTCC I updated the landing site, then in the UPLINKS did 26 Landing Site Vector (this is the one I missed) and 28 LGC Descent Update.

Part 2: I installed the Apollo 15 Landing Site visual. This was important because (for some reason) after I had updated the landing site the first time I tried the landing without the visual update, and even though P68 showed me just west of Index Crater on the LROC map (I had manually input my LAT/LONG in the RTCC Landing Site Update) my visual showed me in the rille on the west side. After installing the visual update I ran it again (this time I just used the LAT/LONG that the RTCC Landing Site Update generated) and after landing P68 showed 026.07 and 003.69, the RTCC values were 26.079 and 3.623. I did re-designate after P64 pitch over, I got nervous because from 5000 ft the LPD looked like I was headed for the rille. But it was a relatively gentle correction. and after landing my visual coincided with the P68 coordinates and the LROC, just north of Rhysling.

So I'll keep playing with this, as I said I want to get a grip on AGS, but I think you ironed out why my landing targeting was off. Thanks.
 

rcflyinghokie

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No problem! Would you mind still posting a pre pdi scn so we can take a look at the targeting? Just want to make sure things were behaving correctly.

For the RLS the reason you give it to the AGS is so it has an idea where you are expected to be after landing and you use 413+1. It's significantly more important for the LGC as that's where it wants to take you. You will see those updates in the flight plan I believe as the landing sire was usually better defined after a few orbits and CSM ground marking instead of just relying on the padloaded RLS.

Regarding the AGS, the docs I posted along with the procedures at the end if the G&N dictionary should give you an idea of what's doing what. You will get a much greater AGS workout on ascent.

Feel free to keep the questions coming!
 
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Wedge313

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I spoke too soon. I guess didn't install the landing site visual correctly, it looks like I have two different visuals going on at the same time. I'm back to the point where the LM is targeting correctly, the LAT/LONG in P68 looks good, but the visual is off. Again it looked like I was headed for the inside of the rille, I redesignated and landed just east of the rille. But the LAT/LONG doesn't jibe with the picture. Also, as I descended just before landing I "passed through" the surface, and touched down a few seconds later on a second surface. I took a screenshot, you can see the LM on the surface but the LM shadow is displaying on the other surface (this effect was more obvious while looking out the window during landing).

Also, here's my scenario from about 2 min before PDI.
 

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indy91

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Ah, I know why your LM is trying to land long. Your LGC clock time is off by about 1.2 seconds. In the LGC activation procedure you first enter a rough time with V25 N36 and then afterwards a more precise time with the help of the CMC and using V55. Did you not do that second part? Maybe something went wrong.

In any case, since not so long ago the RTCC MFD now also has the ability to check and uplink a clock time correction for CMC and LGC. That is definitely easier and faster. But first I would adjust the liftoff time in the RTCC MFD, as that is the reference for the ground elapsed time. In the RTCC MFD go to the Configuration page and press the UPD button (can be done in CSM or LM). That "downlinks" the liftoff time (TEPHEM) from CMC/LGC to the RTCC. It's only a 0.06 seconds correction in your scenario, but I would do it anyway.

Then go to uplinks and for the LGC you choose number 24 (LGC Time Increment). On the left side is a tool to calculate the clock error. Press CLC and it should show you that 1.2 seconds I talked about earlier as the DELTA T. The calculation tool doesn't automatically generate the uplink, so you have to press INP and input the same time in the format HHH:MM:SS.SS. So "0:0:1.21" in your case. Then the INCREMENT display and octals for the uplink should populate with the time update. And lastly of course UPL button for the uplink itself. Afterwards you can press CLC again to do another check, which should now be zero (or one centisecond off, that is normal).

In addition to this probably procedural error, we have also found out that the AGC clocks are drifting in NASSP due to some frame rate issue which is quite difficult to fix. Usually that is about 0.6 seconds off in 200 hours of mission time, although in your case it seems to be larger, as your CMC already is off by 0.6 seconds at this time. Maybe unstable frame rate makes it worse or something like that. So it wouldn't hurt to do a clock increment for the CMC as well (number 7 in the uplink menu). 0.6 seconds off would already violate mission rules for rendezvous. And it's not even that unrealistic, some small clock increments were uplinked during the actual missions, too.
 

Wedge313

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Your LGC clock time is off by about 1.2 seconds.
The dreaded LGC/CMC Clock Sync/TEPHEM Update procedure. I struggled with this on Apollo 11, and that time I had the automatic checklist to to help me with the back-and-forth between the LM and CSM. It doesn't surprise me that I botched it up again. If I go back to a save point before starting P63 and correct the clock, will that work? Or do I need to go back to the Activation Checklist portion?

And regarding the landing site visual, the directions were to unzip the files into the "Orbiters top program". Where exactly do they mean?

Thanks for looking at this.
 

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If I go back to a save point before starting P63 and correct the clock, will that work? Or do I need to go back to the Activation Checklist portion?

You can do it any time in P00. You can almost do it in this PDI minus 2 minutes scenario, but it's probably too short of a time to exit to P00, uplink and go back into P63, even if you use 0.1x time acceleration. But any previous scenario is fine.
 

Wedge313

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Your clock fix worked, I didn't touch anything throughout P64 and the LGC brought me down right where it wanted me to be, P68 showed 26.07N 003.65E, the RTCC showed 26.074/3.654 before hitting CLC and 26.080/3.659 after.

Zooming out on my visual, and comparing where I am to where those coordinates show me on the LROC map seems to match up well, about 150m NNW of Domingo.

Now if I can figure out what's going on with my visual I'd be happy. I tried to install the Apollo 15 landing site visual, and now it looks like I've got at least two different visuals fighting each other. If I zoom in/out I can see different craters appear/disappear. The LM is on the surface but it looks like there's another surface just below.

I never installed the hi-res terrain, I've been using the microtextures. It seems like these two (microtex and Apollo Landing Site) are both there at the same time, but not sync'd up?

The updated Apollo 15 landing site visual is definitely a better look, I'd like to fix this if possible. Or I could just remove it and live without it.

Anyway thanks for the clock fix and everything else.
 

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MrFickles

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The dreaded LGC/CMC Clock Sync/TEPHEM Update procedure. I struggled with this on Apollo 11, and that time I had the automatic checklist to to help me with the back-and-forth between the LM and CSM. It doesn't surprise me that I botched it up again. If I go back to a save point before starting P63 and correct the clock, will that work? Or do I need to go back to the Activation Checklist portion?

And regarding the landing site visual, the directions were to unzip the files into the "Orbiters top program". Where exactly do they mean?

Thanks for looking at this.
I agree with you that using the checklist and switching back and forth can get rather confusing. There's a possibility that you'll go out of sync between the two checklists and get something wrong. But it's actually not too bad if you understand what is going on during the clock sync procedure.

Entering V06N65 on both the CMC and LGC displays the GET the moment DSKY enter is pressed.
You then use the PAMFD ENT button in order to simultaneously press DSKY enter on both CMC and LGC, which updates the times displayed.
Using the CMC time as the reference, find out how much difference there is by subtracting the displayed LGC time from the CMC time.
V55 and enter the calculated difference.
Both clocks should now be synchronized. You can double-check by repeating the first 2 steps.

TEPHEM updating is similar, except you read off the memory on the CMC, then simply copy the same values over to the LGC.
 

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But it's actually not too bad if you understand what is going on during the clock sync procedure.
I'd agree it's not too bad...for most normal people. I'd swear I did everything the way you described, I remember coming up with a difference between the LGC and CMC times and then V55 to enter the difference. But yet somehow I got it wrong. Because this stuff bugs me I'm going to go back to a save spot before I did this the first time and try it again.

But then, my improper LGC programming skills let me exercise my LM piloting skills to avoid landing in the rille, so there's that :unsure: .

Thanks.
 

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The error could be as simple as a wrong sign for the V55. If the CMC clock time is ahead (larger) than the LGC clock then the V55 needs to be positive in order to increase the LGC clock to the CMC time.
 

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The error could be as simple as a wrong sign for the V55
This might be it. I looked at my notes, when I did the clock sync I had the CMC at 98:19:34.82, and the LGC at 98:19:34.24, a 0.58 difference. If I use the wrong sign I'd double down on the error, 1.16. Which is close to 1.2.

I feel like that scene in Animal House, with Belushi's "syncronized" watch.....
 

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Wedge313

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A question about the power-down battery configuration. My LM seems to have a slightly different setup than Falcon did, is there a way to set things up to somewhat closely achieve the end result?

And on the Lunar Surface Checklist Pg 2-9, they recorded values for battery amp-hours. My Ohms law knowledge is shaky, but I can read the volts and the amps, and from that figure out how many watts, but how do I get an amp-hr value with that info?

And on the same subject, after configuring for power down, how many watts should I be burning? There are some systems cycling on/off but my watts vary anywhere between 1000 and 1700. Seems like a lot?
 
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