The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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3. CARTOSAT-1 SENSOR 
3.1. Pan camera 
The pixel size of the images is 2.5m on the ground with 1024 
grey levels (10 bits). The time difference between the 
acquisition of the stereo images is about 52 seconds. The 
spacecraft body is steerable to compensate the earth rotation 
effect and to force both Fore and Aft cameras to look at the 
same ground strip when operated in stereo mode. 
Simultaneous stereo pair acquisitions are of great advantage 
since the radiometric parameters of the images will be 
identical. The stereo pairs have a swath of 26 km and a fixed 
B/H ratio of 0.62. Apart from the stereo mode, the satellite is 
also equipped to operate in the wide swath mode. When 
operated in this mode the satellite can be manoeuvred such 
that image strips will fall side by side so that wider swath 
images of 55 km are obtained by the cameras. The spacecraft 
also has a facility to provide various pitch-biases to vary the 
look angle conditions of the stereo pair. The cameras 
specifications are introduced in table 1. 
Figure 1. Warsaw test site and GCPs distribution 
Focal length (both cameras) 
1945 mm 
Integration time 
0,336 ms 
Quantisation 
10 bits (1024) 
Pixel size 
7x7 pm 
GIFOV Fore 
2.452m (across-track 
GIFOV Aft 
2.187(across-track) 
Table 1. Cartosat-1 camera specifications 
image because all along track images are treated as one iconic 
image where its coordinates are found if the acquisition time 
interval of the corresponding image from the first image is 
added (in general case of more than two images) on the 
framelet coordinates of each image. In other words, in Kepler 
model the transition factor from one image to the next is its 
acquisition time interval. 
3.2. Metadata file 
The metadata file of CARTOSAT which is attached with 
each image is in text format and provides basic information 
of the imagery. In this file navigation data of the satellite is 
not given. Fortunately, the acquisition time interval between 
the along track images is measured and included in this file, 
which should be known in order to implement the UCL along 
track model. 
The formulation of the UCL model for the along track motion 
of two images case is described by the following equations. 
The ground coordinates of the base framelet perspective center 
X c (t), Y c (t), Z c (t) of both images as a function of time is defined 
as follows: 
X e (t) = X 0 +u x -T- 
GM-X-T 2 
2'(Xg + Y 0 + Z 0 ) 3 
4. REFERENCE DATA 
The authors take part in the C-SAP as principal investigators 
with Test Site 3, which is the UCL test site in Aix-en- 
Provence, France. Also, UCL are co-investigators on TS-9 in 
Warsaw, Poland. Unfortunately additional GCPs should be 
measured in the Aix-en-Provence test site in order to have a 
appropriate number of GCPs within the area covered by 
Cartosat. On the other hand Mr. Zych (Goesystems Polska) 
who is Principal Investigator of TS-9 has provided the study 
team with DEMs and with 36 GCPs which are measured in 
the field. These GCPs are well distributed on the images. The 
area covered and the GCPs are shown on Figure 1. 
5. UCL SENSOR MODEL 
5.1. UCL Kepler model for along track motion 
The along track motion is described by the Kepler equation. 
The fundamental point of an along track model is to benefit, 
from the same orbit acquisition, in order to orientate 
simultaneously all the along track images. The simultaneous 
solution extends the narrow field of view of each satellite 
Y c (t) = Y 0 +u-T- 
GM-Y-T 2 
2 .(X 2 0 +Y 0 2 +Z 2 0 Ÿ 
(1) 
Z c (0 = Z o +u z -t 
GM Z„ • z 
2 ■ (X 2 + Y 0 + Z 0 y 
where 
i = t for the first image 
r = t + dt for the second image 
and 
t is the acquisition time a framelet which is defined in terms of 
each image coordinates 
dt is the time interval between the acquisition of the center 
framelet of the images. 
(Xo,Y 0 ,Z 0 ) is the position vector of the perspective center of 
the center framelet of the first image 
(u x ,u y ,u z ) is the velocity vector of the perspective center of the 
center framelet of the first image 
GM is the Earth gravitational parameter with value of 
398600,4415k?« 3 /s 2