RIGOROUS PHOTOGRAMMETRIC PROCESSING OF CHANG’E-1 AND CHANG’E-2
STEREO IMAGERY FOR LUNAR TOPOGRAPHIC MAPPING
Kaichang Di*, Yiliang Liu, Bin Liu, Man Peng
Institute of Remote Sensing Applications, Chinese Academy of Sciences
P. O. Box 9718, Datun Rd, Chaoyang District, Beijing 100101, P.R.China
(kcdi, ylliu, liub, pengman)@irsa.ac.cn
Commission IV, WG IV/7
KEY WORDS: Planetary, Topographic Mapping, Rigorous Sensor Model, Chang'E-1, Chang'E-2, CCD image, Model Refinement
ABSTRACT:
Chang’E-1(CE-1) and Chang’E-2(CE-2) are the two lunar orbiters of China's lunar exploration program. Topographic mapping us-
ing CE-1 and CE-2 images is of great importance for scientific research as well as for preparation of landing and surface operation of
Chang E-3 lunar rover. In this research, we developed rigorous sensor models of CE-1 and CE-2 CCD cameras based on push-broom
imaging principle with interior and exterior orientation parameters. Based on the rigorous sensor model, the 3D coordinate of a
ground point in lunar body-fixed (LBF) coordinate system can be calculated by space intersection from the image coordinates of con-
jugate points in stereo images, and the image coordinates can be calculated from 3D coordinates by back-projection. Due to uncer-
tainties of the orbit and the camera, the back-projected image points are different from the measured points. In order to reduce these
inconsistencies and improve precision, we proposed two methods to refine the rigorous sensor model: 1) refining EOPs by correcting
the attitude angle bias, 2) refining the interior orientation model by calibration of the relative position of the two linear CCD arrays.
Experimental results show that the mean back-projection residuals of CE-1 images are reduced to better than 1/100 pixel by method
1 and the mean back-projection residuals of CE-2 images are reduced from over 20 pixels to 0.02 pixel by method 2. Consequently,
high precision DEM (Digital Elevation Model) and DOM (Digital Ortho Map) are automatically generated.
1 INTRODUCTION
Chinese Lunar Exploration Program (CLEP), usually known as
the Chang’E program is a program of robotic and human mis-
sions to the Moon undertaken by the China National Space
Administration (CNSA) (Wikipedia, 2012). Chang’ E-1(CE-1)
and Chang’E-2(CE-2) are the two lunar probes in phase I of
CLEP which is called orbital mission.
CE-1 orbiter is the first lunar probe of China launched on Octo-
ber 24, 2007. It carries a three-line push-broom CCD camera
which has a ground resolution of 120m and a swath width of
60km at 200km orbit altitude. It is implemented on an area ar-
ray CCD sensor and uses only the 11th, 512th and 1013th rows
to generate the forward-, nadir-, and backward-looking images
simultaneously in the flight direction (Li et al., 2010; Peng et al.,
2010).
CE-2 orbiter, launched on October 1, 2010, is the follow-up or-
biter of CE-1. As a mission highlight, a local image map at Si-
nus Iridum, the pre-selected landing site of Chang’E-3 lunar
rover produced using CE-2 CCD images was released on No-
vember 8, 2010(NAOC, 2010). CE-2 was broadly similar to the
CE-1 mission, but had important differences. CE-2 flew at two
kinds of orbit altitude, 100 X 100km circular orbit at which the
CCD camera can reach a resolution of 7m and 100 X 15km el-
liptical orbit with a resolution of 1.5m around the perilune. The
former kind of orbit provides high resolution global image cov-
erage of the Moon for various scientific researches, while the
latter mainly provides more detailed information for Chang’E-3
lunar landing and surface operation (Zhao et al., 2010b).
* Corresponding author
CE-2 CCD stereo camera adopts a stereo imaging solution with
the single lens and two angles of view in the same track and a
self-push-broom imaging mode with high sensitivity time delay
integration (TDI) CCD (Zhao et al., 2010a). Comparing with
the three-line array mode of CE-1 CCD camera, CE-2 adopts a
two-line push-broom camera to reduce the pressure of mass da-
ta, and meanwhile, assures stereo imaging condition (Zhao et al.,
2010b). It can acquire forward- and backward-looking images
simultaneously to consist stereo pairs.
At present, a global image mosaic of the Moon using CE-I
CCD images and laser altimeter (LAM) data has been produced
(Li et al., 2010). A global image map of the Moon with a reso-
lution of 7m has also been released by the CLEP on February 6,
2012 (Xinhua News Agency, 2012). But there’s no CE-2 topo-
graphic products (e.g., DEM and DOM) released so far. In our
previous research, we developed a rigorous sensor model for
CE-1 stereo imagery has (Peng et al., 2010) and methods of au-
tomatic DEM and DOM generation, and co-registration of CE-1
CCD images and LAM data (Di et al., 2010).
In this paper, we elaborate the rigorous sensor model of CE-2
CCD camera. Firstly, interior orientation model of CE-1 and
CE-2 CCD cameras including parameters and structure of the
camera are introduced in detail. Secondly, the formulas of exte-
rior orientation model are given to constitute a rigorous geomet-
ric model for both CE-1 and CE-2 cameras. After analyzing the
distribution patterns of back-projection residuals, we propose
two methods to refine the sensor model: 1) refining EOPs by
correcting the attitude angle bias, 2) refining the interior orien-
tation model by calibration of the relative position of the two
linear CCD arrays. Finally, experimental results with CE-1 and
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