How to cope? Hmm you just do unfortunately whether you want to or not!
My Dh is in the army, has been away since May. we've done the 6 months stints etc but this has been the hardest time of my life being pregnant and having a sick toddler (Jack has been in and out of hospital) as well as DH having a breakdown and leaving (luckily we're working on things and that doesn't look like it'll be happening).
Anyway... usually I get into crafts etc, like painting (I'm not artistic, but sometimes I trace drawings, paint them up and sell them on TM), come on OhBaby lol, do baking, and also usually make a point of catching up with someone I haven't seen in a while (usually someone different every week - something to look forward to).
If you can use Skype that's awesome. Lucky for your wee one. We talk on the phone so Jack 'talks' to his dad about once a week, but yep its hard if they realise their dad's not there at such a young age (Jack throws a tanty when he sees his father isn't in bed in the morning etc). I guess being the age Heidi is, she won't really know too much of what's going on, which will probably be good for you to cope, hard for your DH though. DH was away for a few stints of 3-4 weeks last year and Jack never really changed his habits/routine too much, it wasn't until this time around that things went haywire. But that was also to do with the fact that I couldn't function let alone be a good mum so I think you should be fine
Um... what else? Pull in all the support around you. Don't ever say no to help or to someone giving you a break from your daughter (you'll probably need one). It's hard not having a sleep in to look forward to, and not having adult conversation. A lot of us forces mummies have gone through it all though so at least you know you're not alone and if you ever want to chat, you know where to find us