According to Satobs, an aviation warning has been issued for an area near Hawaii for several hours during which time, USA193 will be passing overhead. It's believed that this is when it will be shot down.
http://www.satobs.org/seesat/Feb-2008/0337.html
Plot of orbit and are of interest:
http://satobs.org/seesat_ref/06057A/...unverified.pdf