IMFD TLI offset for polar lunar orbit

[flying coffin]

LRO launches NET Jun 2. I need to get new procedures together for that date. The lunar (polar) orbit targeting is done during TLI, with only a small
correction a few hours later.

The IMFD docs say what the Lon., Lat., and Rad. parameters affect for an
equatorial type orbit, but they act different for a polar orbit.
Does anyone know the best way to target a polar lunar orbit with these parameters?

Thanks in advance!

-Chris

 

[BrianJ]

Hi Chris,
well, I think you're the man to figure out the IMFD/Lunar Polar Orbit/TLI technique! But I'll give it a try myself and see if I can't figure out some likely settings.

On a related note - hooray for your LROC buddies for putting up a LRO launch clock on their website. I make the launch time 21:30:00 UTC, 2nd June.

BUT....some of the launch clocks I've seen on some websites assume my PC time(currently UTC+1hr) is actually the time in their time-zone (Arizona = UTC-4hrs ?) - so I'll be 5hrs out.

What do you make the launch time by the LROC website clock?

Cheers,
Brian

 

[flying coffin]

I'm just looking for a more logical way other than the trial and error method
I currently use, which takes some time. I'm thinking that if say, on launch day they discover a leaky flow control valve or something like that, and scrub for 24 hours, we may need to recompute these values fairly quickly.

"On a related note - hooray for your LROC buddies for putting up a LRO launch clock on their website. I make the launch time 21:30:00 UTC, 2nd June."

Yup, that's what I got. 2:30 PM here. Mountain Standard Time is UTC-7

 

[tblaxland]

My experimenting shows that the Offset function offsets the target point in the Course program according to the spherical coordinates entered in the Offset screen. When in velocity frame mode, the offset is such that Lat=0,Lon=0 makes the course program aim for a point that is ahead (ie, along the velocity vector) of the target by amount Rad. So to aim for a lunar polar orbit, you would want to increase (or decrease, depending on if you want to go over the north pole or south pole first) the Lat and Rad values so you are aiming for a point out of plane from the Moon and slightly ahead. I'll play with it some more and see if I can give more quantitative advice than that.

 

[flying coffin]

Thanks Tblaxland!

So far I can get a good EqI (South pole intercept) but need to get the PeA down.
It's around 50M and I need it ideally about 350k, when LRO is at an altitude of 32M above Earth