Camera and filter postflight spectrum analysis for Apollo 9 multiband photography experimen

Keenan, P. B.

Schowengerdt, R. A.

Slater, P. N.

English

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TECHNICAL MEMORANDUM 2
	 N%% 14 19 ^*
INTERIM POST-FLIGHT CALIBRATION REPORT ON
APOLLO 9 MULTIBAND PHOTOGRAPHY EXPERIMENT S065
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P. B. Keenan
R. A. Schowengerdt
P. N. Slater
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iINTERIM POST-FLIGHT CALIBRAI
	
REPORT ON
APOLLO 9 MULTIBAND PHOTOGRAI' _ .;' EXPERIMENT S06S
P. B. Keenan
R. A. Schowengerdt
P. N. Slater
Optical Sciences Center
The University of : ,.rizona
Tucson, Arizona 85721
15 June 1970
IINTRODUCTION
This report supplements Technical Memorandum 1 1
 ar. l includes the bulk of the
spectral analysis on the cameras and filters used in the Apollo 9 S065 multiband
photography experiment. Some additional data on registration errors, film flatness,
format size, and resolution are inclucled.
This report is divided into three sections. The first includes the spectral
transmittance measurements made to date. The second section covers registration and
image height errors. The final section summarizes resolution measurements made with the
complete camera system.
All work reported here was conducted under contract NAS 9-9333, "Post-Flight
Analysis and Calibration of Camera System for Apollo Experiment S065," from the
Manned Spacecraft Center, Houston, Texas. Mr. G. L. Kraus is the technical monitor on
the contract.
N
2SPECTROPHOTOMETRIC MEASUREMENTS
The data presented in this section were obtained with a 2.4-m, f/8 collimator
system or a Cary Model 14 spectrophotometer. The collimator shown in Fig. 2 of
Technical Memorandum 1 was used with the integrating sphere replaced by a ground glass
screen and the monochromator placed after the light source. The collimator was used for
spectral transmittance measurements of the lenses and the filters. These results are given
in Fig. 1. No significant difference was noticed among the four lenses. The curves are
considered accurate to within ±0.03.
The spectral transmittance curves of the filters were verified by use of a Cary
Model 14 spectrophotometer. The check was performed mainly because the transmittance
between 600 nm and 650 nm for No. 58 is not typical of Wratten filtem. However, these
are Photar filters and not Wratten gelatin filters. Photar filters consist of a dye suspended
in the cement between two sheets of glass, and the variance from Wratten filters can be
attributed to the difference in construction.
The variation of spectral transmittance with field angle was measured using the
collimator system. In each band there was no significant variation with wavelength, the
only significant variations being due to vignetting and Cosa
 losses. The relative
illuminance values given in Table 1 are considered accurate to within ±0.03 at all
wavelengths of interest.
In Fig. 2 the normalized spectral sensitivity is plotted for the three black-and-white
camera systems. The values of relative sensitivity are noted on the figure. These data are
believed accurate to ±0.05. Film sensitivity data were taken from Kodak.' Kodak it film
5424 was assumed to be spectrally identical to film type SO-246.
Table 1
Relative illuminance vs field angle
Camera
	 AA	 BB	 CC	 DD
Lens No. 4488988 4489010 4591824 4593532
Filter	 15
	
58
	
89B
	
25A
Aperture	 f/8
	
f/4
	
f/16
	
f/4
Field angle Relative Illuminance
00 1.00 1.00 1.00 1.00
5° 0.98 0.99 0.99 0.98
100 0.93 0.94 0.93 0.94
15° 0.85 0.87 0.85 0.86
200 0.76 0.71 0.76 0.70
250 0.65 0.46 0.66 0.45
4
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WAVELENGTH (nm )
Figure 1. Spectral transmittance of the lens and
filters used on Apollo 9 S06S experiment
0.19	 0.68	 1.00
400
	 500	 600	 700	 800
WAVELENGTH (nm )
Figure 2. Relative spectral sensitivity of lens, film, and filter
combinations for the three monochrome bands
used on Apollo 9 5065 experiment
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4
REGISTRATION ERRORS
Fig. 3 gives the image height error, as a function of field angle, for the lens alone,
and Fig. 4 gives the registration error for the lens-film combinations as a function of field
angle. These curves were derived from data presented in Technical Memorandum 1.
A large fraction of the image height error for the AA and CC cameras is due to the
change of scale resulting from the focus setting used. Plotted in Fig. 5 are the estimated
image height errors that would have reulted if all four cameras had been used at infinity
focus. The improvement for this is considerable, reducing the maximum registration error
by a factor of four.
Fig. 6 represents the measured values of registration error for the flight
photography. The measurements were supplied by R. Weber , 3 and were made on the four
simultaneous exposures of frame AS9-26A-3799. Each frame is effectively superimposed
at the center and the numbers represent x-y distances of each point to the corresponding
point in the A frame, arbitrarily chosen as the reference frame. Distances labeled + are
farther from the center and those labeled — are closer. The frame key is A for color ir, B
for green band, C for black-and-white it band, and D for red band.
Owing to difficulty in determining the location of the same ground feature on each
frame, the original data were considered accurate to only ±60 µm. This large error
prevents any realistic correlation with the data in Fig. 4.
Figure 3. Lens test with plates. Image error is
due to lens alone. Values are plotted with
respect to distortion-free 80-mm lens
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Figure 4. Lens-film cor
for flight conditions
to the green
150	 209	 250
ANGLE
abination. Registration errors
are plotted with respect
(No. 58) camera
i
Figure S. Estimated infinite focus image height errors
from center to corner of format for various
lens-filter-Min combinations are plotted
with respect to green (No. 58) band
6a
n
Figure 6. Frames A, B, C, D correspond to magazines AA, BB, CC, DD.
Values are the differences (µm) in x•y coordinates of each
point from the corresponding point in the A frame
7Table 2 gives the expected values of registration error due to various causes. These
errors are not necessarily strictly addi tive and in some instances will tend to cancel with
one another, reducing the over-all error.
Table 2
Registration errors (center to corner of format)
Typical magnitude Resulting image
Type of error	 of error	 height error
Chromatic variation
in focal length 500 µm 250 µm
Chromatic variation
in distortion 12 µm 12 µm
Filter tiredge 3 arc min 20 gum
Film flatness 100 µm 50 µm
Boresighting 10 300 µm
The results of film flatness measurements are presented in Table 3. The data were
obtained by loading each magazine with about 1.5 meters of the appropriate film and by
focusing a microscope on the emulsion surface at several points over the frame to
determine the contour of the film surface. The microscope consisted of a 32X objective
and a 6.3X eyepiece; the depth of field was approximately t 1 µm.
The data in Table 3 represent a 5 by 5 array of points across the frame for each
magazine. The spacing between the values was 12 mm and extended to within about 3
mm of the flange edge. A refence plane through three corners of the frame was
arbitrarily chosen, and the distances from this plane were calculated. The error in the
values is about ±10 µm, due to film sag during measurement. The large deviations for
magazin e,, AA were attributed by further investigation to the magazine and not the film
type. It should be realized that weightlessness and changing temperatures and humidities
during the S065 mission preclude accurate predictions of the 
film 
contours during the
flight.
Finally, the meas arements of frame size, shape, and spacing are given in Fig. 7.
They were made on simultaneously exposed frames from each magazine, two consecutive
frames being averaged for each dimension. The error in measurement is t0.1 mm, and the
edges of the frames are straight within this value. There was little or no variation from
the beginning to the end of several feet of film.
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1
RESOLUTION
Resolution measurements were made on cameras CC (black-and-white it band) and
DD (red band), with filters, film, f/numbers, etc. identical to flight conditions. Camera
BB (green band) was not tested because the film drive motor had failed, necessitating its
return to the factory.
The tests were made with a tungsten light source and a USAF 1951 three-bar
target. Area-weighted average resolution (AWAR) values were calculated as described ic:
MIL-STD-150A, and ground resolution values are given for an altitude of 200 km (108 n.
mi.). The data are given in Table 4. Flight altitudes ranged between 180 kin (97 n. mi.)
and 246 km (133 n. mi.).
Table 4
Resolution
M
Radial Ground
Target Focus or AWAR resolution
contrast	 Camera setting tangential 0° 7.5° 15° 22.5° 1p/mm m(ft)
>100:1 R 67 75 41 40
DD 00 51 50(160)
T 67 69 53 38
R 37 36 28 30
CC 33 ft 31 80(270)
T 37 35 31 26
R 40 38 39 37
CC 36 70(230)
T 40 37 33 30
R 54 62 34 34
T 54 53 49 34
R 32 27 24 21
T 32 25 24 21
R 31 30 30 29
T 31 28 29 31
2.6:1
DD	 00
CC	 33 ft
CC	 CC
43	 60(190)
24	 100(340)
29	 85(280)
12
Using the formula RM = RoMn given by Mayo" where Ro is the resolution at a
target modulation > 0.98, M is the target modulation, R M is the resolution at M, and n
is an experimental number characteristic of a given lens-film combination, we find :hat
the values of n for the above lenses and films are:
DD, SO-164	 n = 0.23
CC, SO-246	 n = 0.30
The estimated values of resolution at a target contrast of 1.6:1 were calculated,
and are presented in Table 5.
Table 5
Estimated low contrast resolution
Ground
Target	 Focus	 AWAR resolution
contrast Camera setting	 (lp/mm) [m(ft)I
1.6:1	 DD	 o0	 36	 70(230)
CC	 33 ft	 20	 125(400)
CC	 00	 23	 110(360)
A through-focus series was made with camera CC, with the highest AWAR
occurring at infinity focus. This fact, combined with the misregistration introduced at a
focus setting of 33 feet for camera CC, indicates that this camera should have been at
infinity focus during the flight.
The above supersedes data previously presented on high-contrast resolution and
estimates of low-contrast resolution. It should be emphasized that the ground resolutions
listed above are estimates based on laboratory tests of the flight equipment. Also the data
are given in terms of three-bar --esolution, an artificial but generally accepted criterion.
There will be departures from the data listed above depending principally on target
contrast and shape, film exposure, and processing.
Under an extension of the present contract we will analyze the original
photography and up to fourth-generation duplicates. We will then be able to estimate the
actual resolution obtained in the flight photography taking into account atmospheric
contrast attenuation, spacecraft window degradation, exposure and processing conditions,
etc. We will also estimate the resolution lc::s i;, each generation copy.
13
REFERENCES
i P. B. Keenan, and P. N. Slater, "Preliminary post-flight calibration report on Apollo 9
multiband photography experiment 5065," Optical Sciences Center Technical
Memorandum 1, 14 pp., Sept. 1969.
Z Eastman Kodak Company, 1961 to date, Manual of Physical Properties: Aerial and
Special Materials, Data Section 19, Eastman Kodak Company, Rochester, New
York.
3 R. Weber, NASA/Manned Spacecraft Center, Houston, Texas, private communication.
4 J. W. Mayo III, "Photographic resolving power of aerial reconnaissance lenses as a
function of target modulation," Optical Sciences Center Technical Report 28, p.
21, Aug. 1968.


Apollo 9 multiband photography experiment 5065 Interim post-flight calibration report

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