Apollo 9 Problems

rcflyinghokie

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Here in a scenario
If it is a bad state vector, is that fixable?
Looks like you had a side lobe lock on. So your state vector has drifted.

In a nutshell what you need to do is manually slew the RR until you max out the signal strength, then switch to auto track and verify lockon, then switch to LGC and PRO through the DSKY and you will get a few 06 49's telling you its adjusting the SV.
 

indy91

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And what the heck is a side lobe lock on?

Typical_Antenna_Pattern.jpg


It can happen that the RR locks onto and tracks one of the side lobes instead of the main lobe. Usually happens when the locking on was done manual, or if the LGC was doing it, the initial state vectors being a little off. This picture is just from Wikipedia and not for the RR specifically, but you get the idea.
 

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I got it locked back on... correctly I think this time, however I think there may still be something wrong as I am still getting 525s. Also, when I press PRO to go from 16 45 to 06 58, I get a COMP ACTV light for a loooong time, then I get a 611 with the COMP ACTIV light still on. When I clear the 611, I end up back at 06 57!

According to this
611 means "No TIG for given elevation angle", but that helps me not because I don't know what to do about it!

Could I have a bad SV as well since I am still getting 525s?
 

rcflyinghokie

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I got it locked back on... correctly I think this time, however I think there may still be something wrong as I am still getting 525s. Also, when I press PRO to go from 16 45 to 06 58, I get a COMP ACTV light for a loooong time, then I get a 611 with the COMP ACTIV light still on. When I clear the 611, I end up back at 06 57!

According to this

611 means "No TIG for given elevation angle", but that helps me not because I don't know what to do about it!

Could I have a bad SV as well since I am still getting 525s?
Those 525s means your radar is not pointing at the same place it thinks the command module is, so the state vector is still off in all likelyhood.

Your 611 is probably a result of either a bad state vector or bad CSI and CDH burns propagating to a poor TPI solution. If you were side lobe locked the whole rendezvous then you likely need to redo your CSI/CDH burns. You can post a scn I can take a look and see?
 

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Here is a scenario. There were was CSI or CDH in the checklist, after undocking it had me do a phasing burn with the AGS, then went right to TPI.
 

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rcflyinghokie

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Here is a scenario. There were was CSI or CDH in the checklist, after undocking it had me do a phasing burn with the AGS, then went right to TPI.
Oh that's TPI0, you actually don't burn that one, its a quick way back should something be wrong.

So yeah likely your SV, I will take a look and edit this post.

EDIT: Can tell right away you have a side lobe lock on, so the bad SV is the culprit.
 
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rcflyinghokie

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Good! I thought that meant I had to do more than one rendezvous!
So yeah you had bad state vectors and a bad P20 going on because of it.

I have updated your SVs but because of how close to TPI0 you were I did not have time to compute it. So your mission starts off right after TPI0 with good state vectors.
 

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Max-Q

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When I run that scenario, everything works fine until I go to P20. The radar is in LGC mode, I get the 50 18 maneuver request as expected, the maneuver completes correctly, but then the radar slews way off down and to the right, the signal strength goes to zero, and after a few minutes P20 gives me a 503. If I try and manually reacquire, I get more 525s.
 

rcflyinghokie

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When I run that scenario, everything works fine until I go to P20. The radar is in LGC mode, I get the 50 18 maneuver request as expected, the maneuver completes correctly, but then the radar slews way off down and to the right, the signal strength goes to zero, and after a few minutes P20 gives me a 503. If I try and manually reacquire, I get more 525s.
Are you making sure you are keeping the CM bore sighted? Remember on Apollo 9 the LGC did not automatically keep the LM facing the CM you need to maneuver yourself to center the RR error needles
 

rcflyinghokie

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How do I do that if I can't see the CSM?
So basically you need to compare where the LGC is pointing you to where the RR needles are. Since you have good state vectors right now you can slew the RR needles center then move it back to LGC.

Also, have you looked out the forward COAS? You can sometimes catch the sun glinting off the CM as a backup. Additionally you can enable orbiter HUD mode as a backup backup and see where the CM is.
 

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So I go from LGC to slew mode and manually center the needles, I get a very, very weak signal. As soon as I go back to LGC, it slews down and right again and I get a 503.
 

rcflyinghokie

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So I go from LGC to slew mode and manually center the needles, I get a very, very weak signal. As soon as I go back to LGC, it slews down and right again and I get a 503.
Try slewing up or down until you get the highest signal peak, then switching to auto track and see where it is, then maneuver to center those needles and switch back to LGC.

Also if it helps you can pop into the spaceflight discord where we have a dev presence....can utilize screenshots and streaming to better show you these steps as they can be convoluted to the uninitiated :) https://discord.gg/n8YvgGWG
 
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