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| CE-1 and 
  
CE-2 images are presented to demonstrate the effectiveness of 
the proposed methods. 
2 RIGOROUS GEOMETRIC MODEL OF CE-1 AND 
CE-2 CCD IMAGES 
2.1 Interior Orientation 
We have developed the interior orientation model of CE-1 CCD 
camera to calculate focal plane coordinates from pixel coordi- 
nates using Equation (1) (Peng et al., 2010). 
x=(x, —ccd_line) - pixsize - x, 
y =(y, — col) - pixsize — y, 
where pixsize stands for the pixel size of the CCD array; col is 
the pixel position in column direction; (x,, y,) are the center 
position (511.5, 255.5) of the actual imaging area (1024 rows 
by 512 columns); (xp, yo) represent principal point position in 
the focal plane frame; (x, y) is the focal plane coordinate of 
forward-, nadir-, or backward-looking images. ccd line is 11, 
512, and 1013 for forward-, nadir-, and backward-looking im- 
ages respectively. 
Unlike the CE-1 CCD camera implemented on an area array 
CCD sensor, the CCD camera (shown in Figure 1) carried by 
CE-2 is a two-line push-broom sensor assembled on a focal 
plane separately. The two CCD arrays share the same optical ax- 
is with a focal length of 144.3mm. Each CCD line array has 
6,144 pixels. The primary technical parameters are listed in Ta- 
ble 1 (Zhao et al., 2010b). 
backward-looking 
7 7 forward-looking 
TS 
1 
  
      
Figure 1. CE-2 stereo camera imaging configuration 
  
  
  
  
  
  
Orbit 100X 100 km 100X 15 km 
Index circular orbit elliptical orbit 
Nominal swath 43km 6.45km 
Nominal resolution 7m 1.05m 
Viewing angle Forward +8° ; backward -17.2° 
  
  
Table 1. Technical parameters of CE-2 CCD camera 
291 
» X {flight direction} 
CITE TITI forward-iooking 
  
  
  
  
CLETITITTTITTITITI backward-looking 
Figure 2. Focal plane of CE-2 CCD camera 
According to the focal plane configuration of CE-2 CCD cam- 
era shown in Figure 2, we can derive the following interior ori- 
entation equation to calculate focal plane coordinates from pixel 
coordinates. 
x = X, — tan(0)- 
0 (8): f i Q) 
y 7 y, - (col — s): pixsize 
where © represents the viewing angle, which is 8° for for- 
ward-looking images and -17.2° for backward-looking images: 
fis the focal length; col is the column position of an image 
point; S, is the center of CCD, pixsize stands for the pixel size 
of the CCD array, which is 10.1 pm (Zhao et al., 2010b); (x, yo) 
represents the principal point position in the focal plane frame; 
(x, y) is the focal plane coordinates of forward- or backward- 
looking images. 
2.1 Exterior Orientation 
For push-broom sensor, exterior orientation parameters (EOPs) 
are interpolated from original telemetry data for each scan line. 
Lagrange polynomials are used in the interpolation (Liu and Di, 
2011). 
Given the interior orientation model and EOPs after interpola- 
tion, we developed the rigorous sensor model of CE-1 and CE-2 
CCD imagery in the form of collinearity equation: 
X 
=4 Rz Rz Rp X. (3) 
X— 
Y-Y 
Z- wf 
Z 
s 
s 
where (x, y) are focal plane coordinates of an image point; f is 
the focal length; (X, Y, Z) and (Xs, Ys, Zs) are the 3D ground co- 
ordinate and the camera center position in lunar body-fixed 
(LBF) coordinate system; R;, is the rotation matrix from image 
space coordinate system to spacecraft body coordinate system 
(BCS); R,, is the rotation matrix from BCS to orbit coordinate 
systems (OCS); R,, is the rotation matrix from OCS to LBF, A 
is a scale factor. 
In Equation (3), (Xs, Ys, Zs) for each scan line are obtained 
from spacecraft ephemeris and interpolation; R;, and R,, are 
obtained from telemetry data.