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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part BI. Istanbul 2004 
  
  
Figure 4: Camera electronics 
Storage: Thanks to two adding up Solid State Data Recorder 
(SSDR) based on Power-PC processor and totalising 1Gbytes 
data and one redundant unit of 128Mbytes based on 
StrongARM (SA 1100) and acting as a backup unit. 
Each bank is linked to the three storage units via a synchronous 
serial input streams at nominal 20Mbit/s allowing a flexible 
satellite operation. 
3. QUALIFICATION TESTS 
For Alsat-1 mission, the storage units and the camera represent 
new modules (except SA1100 which was flown onboard a 
SNAP nanosatellite). Therefore, they follow all, several 
qualification tests (vibration, environmental test, thermal 
vacuum test, electromagnetic compatibility, etc.). 
3.1 Imager Alignment tests 
Because of their relative complexity with its six independents 
channels, the imager on Alsat-1 was the critical subsystem. It 
has a high demand on the optical and opto-mechanical 
alignment accuracies. Hence, two types of alignment were 
applied: 
Interchannel alignment: The central channel of the bank (red 
filter) was selected as reference then two by two alignments 
carried out with the two other channels. The goal was to have 
the three lines sensor parallels within an acceptable margin. A 
complex mechanical adjustment was done. 
Interbank Alignment: the same central channel was selected 
for both bank then an interbank alignment was achieved so the 
two same channels (i.e.: red) will have their sensor line aligned 
in continuity to achieve a double line sensor (within an 
acceptable margin). 
4. ALSAT-1 FIRST RESULTS 
We began the commissioning phase just after the launch. The 
camera and the SSDR showed their characteristics close to the 
nominal values. 
330 
The first successful image of the Algiers bay was obtained a 
week after the beginning of the imaging tests because of the bad 
meteorological conditions (it was winter in Algeria). 
A first commissioning review one month later showed that the 
equipments were reliable (no electric breakdown until now) but 
the orbit required a correction (due to a slight injection error of 
the satellite). This was achieved throughout six weeks (over 
March & April 2003) to pass from the elliptic orbit [684-745 
km] to a circular one with a 686km altitude. It did not affect in a 
visible way the images quality. 
The examination of the 300 images taken during the first year 
showed qualities close to those of Landsat. The spectral 
characteristics are almost identical on the other hand the images 
of Alsat-1 are geometrically less fine (in urban zones) as shown 
on the photo 5. 
vs 
A 
taken on 15 Mar. 1993 
© LANDSAT data 
  
    
    
Alsat-1 image on region of Oran taken on 28 May 2003 
© CNTS 2003 
Figure 5: Alsat-1 vs. Landsat images 
The images also showed the other distortions more classic like: 
The visible “vignettage” effects (unequal optical transmission 
factor between the centre and the edge of the optics) due to the 
exceptional wide swath width. This effect identified during the 
pre-flight tests was easily corrected. 
The visible "stripping" effects on both bank (more visible on 
bank0). This effect is created by the CCD sensor. It would result 
from bad "Reset" for pixels pairs (some electrons remains in the 
output stage increasing by a constant value the grey levels of