Missile defense is a controversial subject. One reason is with present technology there is no reliable way to intercept attacking missiles. Missiles with different range raise different challenges. One challenge with long range missiles (several thousands km range ) is their velocity (several km/s). Another is the fact that they can have "penetration aids" i.e. the attack ca be designed to fool the defense. Efficient countermeasures against such tactics do not exist. Short range missiles (hundreds of km range or less) on the other hand raise very different challenges: they travel much slower (a few km/s or less). There are much smaller objects. The challenge is that their flight time is very short ( a few minutes at best) and there is no efficient intercepting mechanisms yet for them. High power lasers are being developed which in the long run may have the potential to do the job. Other techniques may be developed. If one takes the case of Israel, whose security is seriously affected by short range missiles, such as Katyushas or Qassams, defense systems should be in a state of permanent alert and able to react instantaneously. The problem is not only having an adequate interceptor, but also an adequate warning mechanism. This will be the focus of this research: what is the limit of the possible in speedy warning? We will explore the possibility of using early warning satellites coupled with ground based tracking systems and see what demands architectures like that would put of the rest of the defense system, in terms of speed of reaction and footprint of the defense system.