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(ATMoB:Discuss) Baker-Nunn telescope camera
Some of you may remember when Dr. Baker, codesigner of the Baker-Nunn
telescopic camera, spoke at ATMoB and NHAS meetings a few years ago.
My parents visited me recently and brought a box of books of mine,
some dating back to my childhood, which had be stored in their
basement for years. Amongst these books is a series of thin
paperbacks labeled SCIENCE SERVICE - SCIENCE PROGRAM - NELSON
DOUBLEDAY INC. The individual books in the series are on various
aspects of space flight, with some concerning astrononmy / planetary
science.
One book in this series, SPACE FLIGHT COMMUNICATIONS, which is
copyright 1969, caught my attention. Although as you might suspect
the book deals a lot with radio communications and radar tracking,
it does discuss other means of communicating with and tracking
spacecraft. Here's a brief excerpt which concerns the Baker-Nunn
telescopic camera that some of you may find interesting:
> Help from the Smithsonian
>
> AS A FURTHER METHOD of obtaining the position of an earth
> satellite, the Smithsonian Astrophysical Observatory operates,
> under a grant from NASA, twelve optical tracking stations. Each
> station has a Baker-Nunn telescopic camera. The instrument has a
> five-by-thirty-degree field of view, with a twenty-inch focal
> length lens, and is mounted on a three-axis pedestal to photograph
> satellites against a star background together with a time
> reference.
> From the photograph, the angular direction of the satellite can
> be accurately determined, since the position of the stars at a
> particular time is quite accurately known. The angular accuracy
> under good conditions is approximately three seconds of arc, better
> than any current radio tracking system. The sensitivity of the
> instrument is also good; for example, the six-foot-long Orbiting
> Geophysical Observatory was photographed at a distance of 23,000
> miles.