Interim Letter Report: Unidentified Target of AN/FPS-17(XW-2) Radar Mission 164

This document is an interim letter report regarding an unidentified radar target detected by the AN/FPS-17(XW-2) radar at the Laredo Test Site in Texas on October 11, 1958. The radar was intended to track the Russian satellite Sputnik III (1958 Delta 2), but the observed target did not match expected satellite characteristics. The target appeared suddenly in three radar beams at 07:21:44.0 Universal time and remained visible for a total duration of 28 seconds. Analysis of the radar data indicated the target consisted of two distinct sections: an initial 0.75-second segment with a rapid range change, followed by a 27.3-second segment with a slower range rate. The target was estimated to be at an altitude of 64 nautical miles, placing it within the meteor band. The report evaluates several potential explanations, including a rocket launch from White Sands Proving Grounds, a satellite, or meteors. Rockets were eliminated because they would have been detected earlier and for a longer duration. Satellites were ruled out because the observed trajectory and range rate were inconsistent with known satellite behavior, and no satellites were expected at that altitude. The report concludes that the most probable explanation is that the target was a meteor, potentially exhibiting both a head echo and a specular reflection from its trail, or two meteors occurring simultaneously. The author recommends verifying if any rocket firings occurred at White Sands on that date and suggests consulting the Harvard College Observatory for any photographic records of meteors in the vicinity at the time of the incident.