Okay, I've finished the mission.
I have to confess I had to edit the comet, because the 1.5 navigation system simply won't show you a transfer to a 12.5 m radius body. So I made it 1250 m radius. Still, it was a pain to get to it...
Okay, so the rocket:
View attachment 43031
Errr... I meant, the shuttle.
In LEO:
View attachment 43032
Deploying the payload:
View attachment 43033
And the landing:
View attachment 43034
So, the game showed me the transfer window this time, but I couldn't get the encounter. So, I circularized in high Solar orbit:
View attachment 43036
And navigated to it just like you navigate to craft you want to dock with...
View attachment 43037
Look how laggy my trajectory is:
View attachment 43038
And finally...
View attachment 43039
View attachment 43040
Here we are:
View attachment 43041
In the surface of Comet Lovejoy.
After that I simply burned back to Earth:
View attachment 43042
That is Mission Completed for me.
If you want I can share you the Planet file I used for Comet Lovejoy.