Compromises connected with the design, installation, and 
maintenance of man-made targets often restrict their general useful- 
ness, particularly in the case of large targets. The uncertain 
radiometric and geometric properties of existing man-made or natural 
features make them undesirable for OTF measurements. A new, 
alternative technique that may be used to acquire the OTF has been 
investigated at the Optical Sciences Center. | 
The technique, called Scale Matching Analysis (SMA), is 
particularly applicable to measurements of the OTF of orbital earth 
resources sensors for two reasons. First, the low ground resolution 
typical of these sensors would necessitate prohibitively large 
special targets for testing. Second, it is common practice to under- 
fly the satellite with similar sensors installed in an aircraft 0 
to aid in interpretation of the satellite sensor imagery. The underflight 
imagery, which may have ground resolution that is an order of magnitude 
better than that of the satellite imagery, provides the additional 
information necessary for SMA. The underflight imagery can be con- 
sidered as the spatial distribution of radiance in the object plane 
of the satellite sensor. The satellite sensor forms a degraded 
image, by virture of the sensor's OTF, of that object. After accounting 
for the effective magnification between the object and image, the 
satellite sensor OTF can be obtained by forming the ratio of the 
spatial Fourier spectra of the satellite sensor imagery to that 
of the underflight imagery. 
SMA has been used to measure the OTF of two operational 
remote sensors 5,56,57 and has been compared in detail to an 
established procedure, Edge Gradient Analysis (EGA)?8, In the 
latter study, the average RMS errors for the OTF's calculated by 
SMA were determined to be + 0.06 in the modulus of the OTF (MIF) 
and + 0.03 cycles in the phase of the OTF (PTF) for a particular 
urban scene. For a particular desert scene, the errors were 9 
* 0.09 and. 0.06. cycles in the MIF and PTF, respectively. It was 
concluded that SMA is a satisfactory alternative to EGA and is particu- 
larly attractive when suitable ground targets are not available 
for EGA or other analysis. 
5.9.4.1 Manufacturing: In industrial practices, Perkin-Elmer 
employs both interferometric data reduction and MTF instrument 
determinations of optical system frequency response. The Eros 
III equipment is used for standard MTF measurements for systems 
With apertures of 30 cm (12 inches) or less. The interferometric 
data reduction analysis facility provide the capability for OTF 
determination for a full range of applications. System and computer 
Programs provide a combination of computer technology and optical