backing up thunderbolt drive to time capsule
I have a 2TB Time Capsule which I use for my wi-fi network and for backing up my circa mid-2011 iMac. My iMac drive is pretty full and I am looking into purchasing a Thunderbolt drive to supplement storage since I expect to buy a new computer within a couple of years; and am a little concerned about tackling a swap of the iMac internal hard drive. My question is this; is it possible to use the Time Capsule to also regularly back up the Thunderbolt drive?
Thanks for whatever help you can provide.
iMac, OS X Yosemite (10.10.2)