Mark J. Carlotto

On September 15, 1991, live video showing multiple objects moving in unusual trajectories was captured by cameras aboard the Space Shuttle Discovery (STS-48). The video, which was being broadcast over NASA Select TV, was recorded by Mr. Donald Ratsch. Later, after rewinding and viewing the tape for the first time, Mr. Ratsch observed what he believed to be four anomalous events. One of those events was recorded by a camera in the shuttle's payload bay between 20:30 and 20:45 GMT near the west coast of Australia. The event involves perhaps as many as a dozen objects moving in different directions relative to the spacecraft. One of the objects, which has been referred to as the "target", appears at a point near the horizon and moves in a path that seems to follow the horizon. After a flash the target, along with several other objects, abruptly change direction and speed. This is followed a few seconds later by a streak that moves rapidly across the field of view towards the target. At the end of the event, the camera pitches down revealing several objects moving below the shuttle. One of the objects appears to have a triangular shape. Within days Mr. Ratsch provided copies of his original recording along with detailed descriptions of four anomalous events to various investigators including NASA. Two months later after reviewing the video, NASA agreed with his descriptions of the events but disagreed with his interpretations (i.e., that they were UFOs). NASA concluded the objects seen in the video were either ice particles or orbiter-generated debris illuminated by sunlight. Concerning the event considered in this presentation they stated:

"The objects seen are orbiter-generated debris illuminated by the sun. The flicker of light is the result of firing of the attitude thrusters on the orbiter, and the abrupt motions of the particles result from the impact of gas jets from the thrusters." In the following presentation we examine this event in detail in order to determine if the objects in question are indeed debris in close proximity to the shuttle disturbed by a thruster firing as contended by NASA or more distant objects moving independently of the shuttle.

  • Background
  • Overview of Event
  • Trajectory Analysis - 2D Motions
  • Correlated 2D Motions
  • Did the Shuttle Fire a Thruster?
  • Target Object - Overview
  • Appearance of Target Object
  • Motion of Target Along Horizon Line
  • Motion of Target Across Airglow
  • The Streak
  • Model of Target Motion
  • Is the Target Near the Shuttle?
  • Is the Target at the Horizon?
  • Strongest Evidence
  • Object Below Shuttle
  • Conclusion

  • To view a reprint of Carlotto's original paper on the STS-48 video published in the Journal of Scientific Exploration, click here.

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