MOMS-02. The technical features of the MOMS-02 camera 
are oriented toward the requirements of today's photo- 
grammetric and thematic applications. Characteristic features 
of the sensor design include: 
e three-line stereo imagery 
e  along-track stereo imagery 
e high resolution imagery 
e multispectral imaging 
e combination of stereo - and multispectral imaging 
Figure 2 shows the MOMS-2P imaging geometry and the 
resulting ground track. The swath width for the high resolution 
channel is between 44 and 50 km, depending on the recording 
mode, and between 90 and 105 km for the other channels, 
depending on a nominal orbit altitude between 390 and 420 
km. Because of the viewing angle of 21.4? of the two off-nadir 
stereo channels, the image swath on the earth's surface for 
these channels is separated from the swath of the nadir 
channels by about 130 km. 
Figure 3 gives a schematic representation of the MOMS-02/2P 
optical concept. In order to fulfil the different user 
requirements a modular concept was selected. The system 
consists of five lenses, three were designed for stereoscopic 
applications, whereas the other two enable the acquisition of 
multispectral data sets. The central lens, with a focal length of 
660 mm, forms the core of the camera system. This camera 
acquires the high resolution imagery with a ground pixel size 
of 5 m x 5 m. In combination with the central high resolution 
lens, there are two other stereo lenses, each with a focal length 
of 237.2 mm. Because of their tilt angle of 421.4? and -21.4°, 
respectively, relative to the direction of flight, threefold 
stereoscopic imagery is enabled. The focal length of these 
lenses was selected in a way to obtain a 1:3 ratio for the ground 
pixel size of the high resolution and the tilted stereo channels. 
In addition, two other lenses, each with a focal length of 220 
mm, enable the multispectral imaging of a total of four 
channels. 
MOMS-2P was designed for spectral data acquisition in the 
VIS and NIR range (four channels) and for along-track stereo 
recording using a panchromatic channel for one nadir and two 
off-nadir looking modules. A ground pixel size of 15 m x 15 m 
for the spectral channels was a sound compromise between a 
high spectral resolution and a sufficient signal-to-noise ratio. In 
addition, the IFOV of the spectral bands and the tilted modules 
is an integer multiple of that of the panchromatic nadir module, 
which significantly simplifies the merging of simultaneously 
recorded data. Figure 4 shows the position and width of the 
spectral bands of MOMS-02/2P. 
The stereo module of MOMS-02/2P allows to reconstruct high 
quality 3D products. The most important property of the sensor 
is the along-track stereo capability (Bodechtel et al. 1984). An 
automatic procedure for generating Digital Terrain Models 
(DTM) from three line stereo was developed (Ackermann et 
al., 1989). To achieve DTM's with high accuracy the camera 
had to combine the along-track imaging with the three line 
principle. Significant is further the combination of high 
resolution nadir imaging with lower resolution tilted imaging 
(5 m versus 15 m). The accuracy of automatic derived DTM's 
is better than 5m absolute. For stereo mapping from satellite 
the MOMS stereo module provides unique possibilities. 
  
   
   
     
  
  
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150m x 15,0 m 
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Fig. 2: MOMS-2P imaging geometry 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996 
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