# How closely may an artificial satellite orbit Earth without decaying appreciably each orbit?

Just what the title states. An artificial satellite will orbit Earth with some defined angular momentum. An aircraft,on the other hand, relies upon it's engines to provide continuous forward velocity & lift.

I understand the mass of the satellite, shape of the orbit may be a factor here. As also the factors mentioned in dmckee's comment below. To clarify, the intent here was indeed to determine atmospheric drag. Mike & Peter, I proffer my apologies.

How closely may an artificial satellite orbit Earth without decaying appreciably each orbit? Is there a definite formula/formulae to determine this by direct substitution of values, or is each such calculation unique?

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