Object docking in Space How do objects dock in space?
There's a recent piece of news that Keppler would dock to the ISS sometime this week. I want to know the operational aspects of it - considering the velocity of the objects involved and also the lack of references.
 A: Well, I am pretty sure Kepler is not docking with ISS, because Kepler is orbiting Sun and ISS is in low Earth orbit. But in general, docking is performed over several days with slow adjustment of velocities so orbits match with final stage docking performed with small thrusters usually called linear RCS. What is important when docking is relative velocities which are usually ~ 10cm/s in final stage of docking. The fact that both vehicle are racing with 7km/s around Earth or 30 km/s around the Sun or 200km/s around the Galaxy OR 600km/s vrt. CMB is quite irrelevant. Also, it may be interesting to note that docking spaceships is quite fun. Do try googling for "orbiter" which is a simulator of newtonian spaceship. There, you can launch your space shuttle and dock with ISS. True fun for any real geek :)  
A: You might be amused to know that this is the subject of Buzz Aldrin's PhD thesis at MIT, "Line-of-sight guidance techniques for manned orbital rendezvous" (six years before he walked on the moon).
There is a wikipedia page titled "space rendezvous" which will probably lead you to what you are looking for; or perhaps consider the book "Automated rendezvous and docking of spacecraft".
A: Orbiting mechanics are funny. If I am trailing a satellite in orbit, in order for me to catch up with it I need to slow down. Then I drop into a lower orbit with less orbital period which moves me ahead faster than my target. Then when the time is correct I speed up and jump back to the higher orbit where I can match speeds.
So apply thrust to move back, and apply drag to move forwards. Makes sense!!!
Back in 1989 I wrote a computer program/game to do just that. Trying to catch up in orbit with something by adding or removing speed. It was loads of fun to try out different techniques for docking.
