Ghost 14: multiple disk backup on larger disk

I do have a simple question:

 

I have a Windows Vista Media Center equipped with three 500Gb disks. Now I want to make a full backup of the three disks to a 1,5Tb disk. Is this possible and if so can I schedule it so it will keep track of my changes or do I need a larger disk for that (in theory I don't have any extra space on the 1,5Tb disk when shadowcoping the three 500Gb disks)?

 

Please some advise would be nice!