How big is big? You can still get used FE-5680A rubidiums on Ebay for a few hundred. They are about the size of a small book and need ~20 watts.
Not sure how good/useful/not broken they are since I've never had one, but over the last 10 years I've seen them in a good number of hobbyist projects.
Or you could just go for GPS. That's technically still atomic clocks, but in space!
Not sure how good/useful/not broken they are since I've never had one, but over the last 10 years I've seen them in a good number of hobbyist projects.
Or you could just go for GPS. That's technically still atomic clocks, but in space!