Could do with a few tweaks....
There were plenty of things I liked about this game but they were overshadowed by a couple of problems.
At first I thought the limited ammo was a good idea because it meant you had to be economical with your firepower while you raised money, rather than just blasting randomly. However, within a couple of levels I'd bought enough of the long-lasting larger satellites and was making money faster than I could spend it before I reached level 10. By that point the game had become just another random-blast-em-up; games aren't supposed to become LESS challenging as you progress!
I don't understand why some people are complaining about the limited ammo - without that, the screen would be full of satellites by about level 5. I reckon you should keep the limited ammo idea and emphasise strategic playing; with that in mind, you should give the player some control over which satellites fire, rather than having them all fire at once. If one of your satellites is running low on ammo, it's frustrating to have it firing needlessly into the side of the planet just because other satellites are shooting an enemy on the other side.
There's all sorts of stuff you could do with this game - upgrades, more varied satellites with different weapons, more enemies with different attacks, bosses, and so on. As it is, it starts off as a decent game that makes you think a bit, then later becomes an easy and repetitive snoozefest. Sorry if you included any exciting suprises after level 16 - I was bored by that time and quit.
Bring on the sequel!