Physical Sciences Inc. (PSI) is developing, with Navy SBIR Phase II funding, a hardware in the loop Global Positioning System (GPS) receiver Testbed. A computer simulation will "fly" a re-entry body (RB) along its trajectory and compute plasma properties that produce GPS signal attenuation and pseudo-range changes for each GPS satellite in view for the specified day and time. (The specified day and time determine the locations of the GPS satellites relative to the RB.) The simulation will compose digital instructions that specify GPS signal attenuation and pseudo-range change. The instructions will be sent to a GPS signal simulator via Ethernet using UDP. The GPS signal simulator generates analog RF electronic signals that are fed into a real, physical GPS receiver, thus emulating what would occur on an RB in flight. The GPS receiver navigational output will be compared to the input trajectory to determine the accuracy of the GPS receiver. Because attenuation of the GPS satellite signals will be, in general, different for each satellite, the effect of sequential loss of signal from various GPS satellites and the degradation on GPS trajectory determination will be part of the capability. In addition, when the RB goes into and returns from plasma blackout, the simulation can be continued to determine the time required for the GPS receiver to acquire and establish navigational capability.
The FLIR video recorded by the FBI on 19 April 1993, records the final assault on the Branch Davidian compound in Waco, Texas, and the fire in which some 80 members of the sect died. Attention has focused on a number of flashes recorded on the videotape. The author has examined the 1993 videotape and the recorded videotapes of the re-enactment conducted at Fort Hood, Texas on 19 March 2000. The following conclusions have been reached: 1) The flashes seen on the tape cannot be weapons muzzle flash. Their duration is far too long and their spatial extent is far too great. They are almost certainly the result of solar energy or heat energy form nearby vehicles reflected toward the FLIR by debris or puddles. 2) The FLIR video technology has a very low probability of detecting small arms muzzle flash. 3) As a consequence of 2) above, the absence of muzzle flash detection on the FLIR tape does not prove that no weapons were actually fired during the final assault. Indeed, there is ample evidence (not presented here) that the Davidians fired at the federal agents, but none of their muzzle flashes are detectable on the videotape.