Expand for details:
0- Make a backup of your Coalesced.ini
1- Download the Coalesced Editor* here: http://social.bioware.com/project/1854/#files
2- Click All BIOInput Sections
3- Expand [SFXGame.SFXGameModeBase]
4- Find the Bindings entries for PC_GalaxyKeyRotateLeft & PC_GalaxyKeyRotateRight
5- Increase "Repeat PlanetLeftRight -1" and "Repeat PlanetLeftRight 1" to higher values to speed up the planet rotation with the A & D keyboard keys.
6- Click "Rebuild Coalesced" and you are done.
This video was made using -14 and 14 or values close to those. Adjust to your liking.
*If you don't use this editor the game will crash on load. Notepad++ works as well, but you'll have to keep the character count the same. The Coalesced editor was created and uploaded by Iron Spine to BioWare's Mass Effect forums to get around this restriction.
Use at your own risk! If anything bad happens, replace your edited ini with the original one you backed up.