To all those wondering how the Americans claim to know what happened, try reading these Wiki references. Surface radar observations are not required.
MASINT
Space-Based Infrared System
Space Tracking and Surveillance System
Trumpet (satellite)
These systems would tell the US exactly where the missile was launched, track the missile in flight, observe the explosion, analyse the spectral traces of the missile efflux and the warhead detonation, and record the SAM radar emissions. The missile's speed and trajectory and the characteristics of the efflux, warhead and radar can all be used to identify the missile system.
With all this information to hand, you can understand why Obama was in a position to point the finger only hours after the news broke. The accident site will yield more information; explosive residues, missile parts, etc, and those will be the sticks with which the international community beats Russia in due course. The US will almost certainly keep its MASINT secret because:
1) Those who already know what happened (e.g. Putin) will merely have their knowledge of US MASINT capabilities enhanced;
2) Those who disbelieve everything the US says will just say the US is lying;
3) Those who believe the US don't actually need to see the evidence in order to trust what Obama said.
So I think there is little chance we'll ever see any of this highly-classified intelligence. But perhaps the conspiracy theorists might consider that the US case against the separatists is based on evidence more substantial than a few tweets, a Facebook post and a (allegedly) doctored telephone conversation.