PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
January 2016
9
Ondrejka, who succeeded Aschenbrenner as ITEK’s chief
photogrammetrist, told the authors that the Gamma Rectifier
Model 1 at first treated Corona images made with a single
camera. Later, Model 2, treated dual camera imagery.
According to (Hilbert 2005), twelve Model 2 rectifiers were
made. A number of changes after Model 1 were introduced.
Model 3 corrected Earth curvature with a curved glass easel
instead of the curved metal easels in Models I and 2 visible
as (6) in the Gamma Rectifier image in Figure 6. Ondrejka
stated that only a single prototype was made (Gamma
Rectifier III 1966).
Figure 4. The ITEK EN-71 Panoramic projection transforming printer.
Figure 5. Aschenbrenner (left) and the EN-71 team. . From ITEK
newsletter May 24, 1962. (courtesy R. Ondrejka)
A ground “footprint” of the distortion due to Panorama, Earth
Curvature and Camera Tilt has been calculated (Figures 17-
47a and 17, 48, Ondrejka (1980). See Kawachi (1966) for
distortion equations at lower altitudes.
The Gamma Rectifier was classified as “top secret” in January
1966 and declassified only in 2003. Its existence was partly
revealed by Hilbert (2005). Only those involved in its design
and construction had access to the mathematics of the optical
system. These were not available for publications written
even after declassification of the imagery itself in 1996, e.g.
Sohn (2004), author of two widely used correction methods.
Such methods require many control points for accuracy at
the ends of Corona film strips where distortion is greatest.
According to Hilbert (2005), a modified KH4-B camera pair
(KA-80) and a Gamma Rectifier were used for Moon mapping
by the Apollo15 to 17 Lunar Orbiters. No information from
Flagstaff on its ultimate fate or documentation could be
obtained. The first author of this paper obtained an 128
page photocopy of the Gamma Rectifier 1 Report, containing
the optical design from the CIA with a request made under
the Freedom of Information Act in 2015. (Gamma Rectifier
Report 1966).
Figure 6. An ITEK Gamma Rectifier Model 1.
The aero-triangulation
software used was various
editions of MUSAT
(Multiple Station Analytical
Triangulation) developed by
the Automatic Operation.
