late 1950s, anticipating the introduction of artificial earth
orbiting satellites, the Smithsonian Institution developed an
ambitious program to track these satellites.
Almost every aspect of this major
endeavor was an innovation: the science of satellite orbits, the
technology of imaging and tracking, and the bureaucracy of this
complex global organization.
The specialized photographic
telescope developed for the purpose of imaging the track of a
satellite across the sky was the Baker-Nunn camera and and Joseph
Nunn used 55 mm Cinemascope film.
The optical system consists of a
three element modified Schmidt corrector with an aperture of
20-inches (50-cm) and a spherical primary mirror 30-inches in
diameter. The effective focal ratio of the system is very fast at
F/1 with the focal plane located inside of the Optical Tube
Assembly (OTA) between the corrector lens elements and the primary
A dozen f/0.75 Baker-Nunn cameras
with 20-inch apertures – each weighing 3.5 tons including a
multiple axis mount allowing it to follow satellites in the sky –
were used by the Smithsonian Astrophysical Observatory to track
artificial satellites from the late 1950s to mid 1970s.
Data from these cameras allowed the
rocket scientists to increase their success at the very difficult
task of orbiting a ground launched object, and in addition the
data provided a wealth of scientific information.