Apollo 10 P22 Landmark Tracking: REFSMMAT/Alignment Question

Wedge313

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Hi, I'm trying to do the P22s at approx. 82+00 on the flight plan. For some reason my alignment doesn't seem correct. (See attached images)

The last time I uplinked a REFSMMAT was back around 69+30, when we did a re-alignment to LLS-2.

The checklist has us maneuver to 000/326/000. There's a nice diagram that shows how the CSM/LM should be oriented at 82+04, basically the CSM pointing straight down at the lunar surface. But my orientation has me about 60 degrees off from that, heads down.

I maneuvered to what looked to be the correct orientation and end up with about 000/024/000 inertial. Continuing on from there the landmark (F1) shows up at T-1, and at T-2 the optics auto-track the landmark well. So my manually set attitude seems to have the ship oriented correctly to run the tracking.

But what have I messed up so that the 000/326/000 orientation has me so far off?

I've attached a .scn.

Thanks
 

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  • [D3D9Client] 11_22_2022 3_49_35 AM.png
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rcflyinghokie

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When was your LOI and LOI2 compared to the flight plan? I bet this has to do with you getting to the moon later than the flight plan called for which actually happened.
 

Wedge313

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I was about four minutes+ behind the flight plan time on LOI (mine was at 75:49:46, flight plan showed 75:45). About two minutes behind on LOI2 (mine 80:12:35 flight plan 80:10).

FWIW, when I did the P52 opt 1 LLS2 REFSMMAT at 94:50 I saw a big change in the FDAI pitch. So maybe I'm back on track?

EDIT: I snuck in a P22 at 96:39 using LMK 130, the orientation looked good. So you're probably correct about that initial LLS2 alignment.

Thanks
 
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indy91

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So the LS REFSMMAT that gets calculated and uplinked before MCC-4 uses a planned time of landing. That variable is initially loaded from a launch day specific RTCC config file and afterwards it's being saved and loaded in the RTCC. This variable is zero in your scenario instead of circa 100 hours. In 100 hours the Moon rotates about 53°, so that is the big change in FDAI pitch you are seeing when the LS REFSMMAT was calculated in lunar orbit. For that uplink a preliminary DOI solution is calculated, which will have recovered a good time of landing.

So the question is how the time of landing variable changed from launch to pre MCC-4. That really shouldn't happen, only a descent planning calculation in the RTCC MFD should be able to change the variable. Or if you manually change the time to zero on the REFSMMAT page. Did you do some stuff with the RTCC MFD on this mission?

One thing you could do is check your scenarios from this mission, search for RTCC_TLAND and look when that changed from about 362778 seconds (= 100 something hours) to zero. That would be very helpful, maybe it's still a bug I am not seeing!
 

Wedge313

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I don't think I played with the RTCC, at least I don't remember. But I'll dig around and see what happened to the TLAND value.
 

Wedge313

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One thing you could do is check your scenarios from this mission, search for RTCC_TLAND and look when that changed from about 362778 seconds (= 100 something hours) to zero. That would be very helpful, maybe it's still a bug I am not seeing!
After going back through all my saves, ALL my RTCC_TLANDs were zero.

I started this simulation using the Apollo - Mission Scenarios - 10 - 01 - Before Launch T-20min scenario. In that scenario the RTCC_TLAND is already zero. In fact TLAND is zero through the first five canned scenarios. It's not until the sixth scenario (Before MCC-1 TIG -15min) that TLAND shows 370031.0000.

Also, I don't know if this matters, but I did a little more digging... I looked at the Apollo 10 - Launch and Apollo 10 MCC - Launch scenarios and compared them to the Apollo 11 scenarios. There are three RTCC values missing from the Apollo 10 scenarios: RTCC_LOI, RTCC_LSAzi, and RTCC_TLAND. These values are also missing from the Apollo 9 scenario. I'd guess they aren't important if you don't plan to land on the moon, but I don't know when the TLAND would be generated to allow you to calculate the LLS2 REFSMMAT.

I'm using NASSP v1951.
 

indy91

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After going back through all my saves, ALL my RTCC_TLANDs were zero.

I started this simulation using the Apollo - Mission Scenarios - 10 - 01 - Before Launch T-20min scenario. In that scenario the RTCC_TLAND is already zero. In fact TLAND is zero through the first five canned scenarios. It's not until the sixth scenario (Before MCC-1 TIG -15min) that TLAND shows 370031.0000.

Ah yeah, I know how I broke it. Old scenarios first had zero saved in TLAND and then the MCC previously loaded the predicted time in its mission specific code, but not until the MCC-1 calculation. So old scenarios in that timeframe still had the zero and the current MCC wasn't updating it anymore. I'll fix those mission scenarios. This issue has been there already for 1.5 years, but I guess most people who flew a full Apollo 10 mission used the T-4h launch scenario which doesn't have this problem (no TLAND saved in the scenario, so it gets overwritten with the value from the config file).

Also, I don't know if this matters, but I did a little more digging... I looked at the Apollo 10 - Launch and Apollo 10 MCC - Launch scenarios and compared them to the Apollo 11 scenarios. There are three RTCC values missing from the Apollo 10 scenarios: RTCC_LOI, RTCC_LSAzi, and RTCC_TLAND. These values are also missing from the Apollo 9 scenario. I'd guess they aren't important if you don't plan to land on the moon, but I don't know when the TLAND would be generated to allow you to calculate the LLS2 REFSMMAT.

I'm using NASSP v1951.

You can delete the launch scenarios with the word MCC in them, they are not maintained anymore. All launch scenarios are now running the MCC by default, you just have the option to disable it. Or of course in the case of the later missions, there are no updates coming from the MCC.

So for Apollo 11 we have the TLI targeting parameters for alternate launch days July 18 and 21. We have launch scenarios for those days under fictional missions. So for Apollo 11 only I have tried to make the MCC support as generic as possible, which is why LOI and LS_Azi are in the Apollo 11 launch scenario, while for Apollo 10 they are hardcoded in the MCC code. I should probably delete the TLAND from the scenario though, that is an actual RTCC parameter (and not one I invented for MCC support) so that is loaded from a launch day specific RTCC config file and doesn't need to be in launch scenarios.
 
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