International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004 
  
Measurement bias is denoted in blue and the residual error is 
shown in red. Test case number zero denotes the minimum 
values for all parameters. Increasing test case number first 
increases in edge length, then noise standard deviation and 
finally edge magnitude. 
e 
Measurement Bias and Residual Error 
0.06 UT T T T T T 
Nyquist Frequency 
  
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Test Case Number 
  
Figure 4. Bias and residual error for Nyquist MTF 
2.3 Imagery 
2.3.1 Sensor: The OV-3 High Resolution Imaging Satellite 
acquires one-meter GSD panchromatic and four-meter GSD 
multispectral imagery from an orbital altitude of 470 km. The 
nominal ground sample distance values reported are for nadir 
acquisitions. OV-3 maintains a sun-synchronous orbit with an 
inclination angle of 97.25". The telescope is a 3-mirror 
anastigmat design with a 45 cm aperture. This paper focuses on 
the analysis of the panchromatic band as it is the more stressful 
case for MTF; the panchromatic focal plane is described below. 
The panchromatic detectors are 6.0 pm by 5.4 pm in the cross 
scan and along scan directions respectively. Even and odd 
parity detectors are offset in the along scan direction by 
approximately 4 pixels or 24 jum. The offset pixels are 
subsequently aligned during the image reconstruction process. 
Imagery is acquired at 11 bits per pixel (bpp) and is compressed 
for downlink to 2 bpp. 
Exposure is control is provided by 16 panchromatic imaging 
modes. The camera may be commanded to image at line rates 
of 5000 lines per second (Ips), 2500 Ips, 1000 Ips or 500 Ips. 
Additionally, the integration fraction or duty cycle for each line 
rate may be selected from full, one half, one quarter or onc 
eighth of a sample period. These modes provide broad control 
over dynamic range, signal to noise ratio and detector smear. 
The nominal revisit period for any point on the earth is 3 days 
within a 50° field of regard (FOR). The FOR may be reduced, 
however depending on product requirements. For this work, the 
look angle was restricted to 15°. 
2.3.2 Fixed Targets: Edges targets that are constructed 
specifically for MTF measurements are generally preferred for 
analysis. One such target has been constructed at the John C. 
Stennis Space Center. The target is of sufficient size to measure 
MTF of imaging systems with GSDs of 1 meter or less. Each 
painted edge is 20 m long by 20 m wide. An OV-3 image of the 
MTF target range is shown in Figure 5. Observe that two targets 
are available for along scan and cross scan measurements in à 
single acquisition. 
Edges 2 Edaes for 
for along scan 
CTOSS analysis 
scan 
analysis 
  
Figure 5. Edge targets at Stennis Space Center 
2.3.3 Urban Edges: Imaging opportunities for fixed targets 
are limited, particularly as near-nadir acquisitions are desired to 
reduce atmospheric effects. With careful selection, suitable 
edges can be found in urban areas. This allows many more edge 
samples to be used in the analysis. Measurements from 
individual edges are combined using a weighted least squares 
approach. This provides a straightforward way of including 
measurements from different target types. An OV-3 image of a 
building edge used for MTF measurement is shown in Figure 6. 
The ESF from this edge is presented in Figure 2. 
Edge Used 
for 
Analysis 
  
Figure 6. Building edge for MTF analysis 
3. RESULTS 
One dimensional MTF estimates are provided for the 
panchromatic band in the along scan and cross scan directions. 
MTF was calculated on the Basic image product, which is an 11 
bit, satellite geometry image. In general, a nominal sharpening 
or Modulation Transfer Function Compensation (MTFC) is 
applied to the image data prior to delivery. Results are 
presented both with and without sharpening applied for more 
direct comparisons to other imaging systems. 
A total of 36 edges were used for the MTF analysis presented 
here. Eighteen edges were used for cross scan measurement, 
with 6 edges being fixed, painted targets and 12 edges from 
urban scenes. Eighteen edges were used for along scan 
measurements as well with 6 edges from painted targets and 12 
edges from urban scenes. The 18 MTF estimates were 
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