Condign volumes 1 to 3

Read from the scan by GLM-OCR; expect the odd misread word.

SIGHTLINE RATES OF FLYING OBJECTS

## INTRODUCTION

1. This brief paper is intended to relate to frequent UAP reports where objects cross through the observer's field of view at what are often, reportedly, extra-ordinarily high velocities. Typical examples are those of satellites and meteorites.

## SIGHTLINE RATE GEOMETRY

2. The basic geometry assumption is that, from the initial visual contact, the object continues in a straight line until it goes out of sight due to some local obscuration or reaches the observer's visual horizon. The largest angle through which an object can pass is from horizon to horizon. Usually the angular sector crossed (or at least seen by the observer) is much less. The angle crossed is usually viewed either in azimuth or elevation. On occasions the object is diving and often disappears during the process - and these are usually explainable as burning-up meteorites or space debris. The greatest tangential velocity occurs when either the object is passing exactly overhead or when at a $ 9 0^{\circ} $ azimuth offset. Velocities always appear to be greater when objects are closer to the observer, even though they are identical to those at greater range which pass through the same enclosed angle but take longer because the distance subtended is greater. The human perception of speed is often distorted by any accompanying sound. Many UAPs are reported as 'silent'. However, it is borne in mind that if any sound is present it can give added perception of speed (see Working Paper Nos. 1 and 8).

3. On the spur of the moment, accounting for surprise and even incredulity, later embellishment, misunderstanding and over or under estimation; it is clear that the time and velocity figures given by a UAP witness can be wildly inaccurate. Further, more than one witness at the same event may provide

conflicting evidence. Often, events are reported as duration of 'about ten seconds' or 'two to five seconds' and through small angles. Further, those not regularly concerned with aircraft can only be expected to give very approximate altitudes (ranges). However, the evidence cannot be ignored, as taken together with other information from the same sighting and with other witnesses, which may come from nearby. Crude target track construction can be made - hence a process of elimination of options is assisted. Further, untrained observers regularly have difficulties with range assessments and grossly misrepresent objects as being "beyond the moon", or "about 2 fields away".

4. The Field of View(FOV) available is clearly much larger when the observer is in an advantageous position, e.g. open countryside, on a hill, or (without obscuration) viewing over the sea or, finally, in the air. Even so, for often inexplicable reasons, and with clear FOVs, objects are sometimes only seen fleetingly. Velocity discrimination/estimation is much more difficult - even for aircrew in this case, unless in a parallel course or catchup/overtake/being overtaken scenario.

## PARAMETERS

5. The attached plots at Figures 1 and 2 although accurate, are intended as a guide in the analysis of a UAP sighting, where the witness provides one or more of the following.

- Start (elevation angle) and finish (elevation angle)

- Time of observation together with some idea of the angle passed-through

- Time and altitude of an objects' passage.