Part: CubeSense V3
Doc: User Manual
Ver:
1.11
Page: 17
4.
Important Usage Considerations
4.1
Detection thresholding
Sun/Nadir-sensors need to differentiate the sun/earth from the background of space in the
images that they take. In both cases this is done by comparing the brightness of the pixels in
the image to each other, in order to locate the sun and the edges of the earth. These
algorithms require a threshold and sensitivity value to execute. By setting the threshold high
enough, unwanted artefacts in the image taken by the camera are discarded, and only the
relevant celestial body is identified.
The threshold is set to a default value optimized for robust measurements. If the user wishes
to change the threshold values, telecommand 40 can be used. It is however recommended
that the default values be used.
4.2
Image exposure settings
The exposure times for the image sensors are key to their successful operation. The default
exposure settings for the sensors are set to values for robust operation and it is recommended
that the client do not alter these values. If, however the client wishes to use the Nadir sensor
as a greyscale imager, the exposure can be set by using telecommand 43. For correct detection,
the exposure should be set to acquire images similar to Figure 6.
Figure 6
–
Images of earth (left) and sun (right) from orbit
