However, this approach has two limitations, the dynamic range is limited by the electron well depth of the pixel, and long exposure times are not suitable for tracking fast occurring events such as falling asteroids or space debris.
In addition, since where or when asteroids or debris will fall cannot be known, tracking these kind of objects requires a unique combination of wide ﬁ eld of view, very high sensi-tivity and speed.
Driving CCD camera at 20 frames per second greatly reduces its sensitivity and the amount of collected photons. Only EMCCDs are capable of achieving fast frame rates required for this application, while maintaining good sensitivity levels thanks to the em-bedded on-chip Electron Multiplication (EM gain) which eliminates the readout noise. See Figure 1 and Figure 2, EMCCD allows a gain of sensitivity of up to 4 stellar magnitudes compared to a traditional CCD.
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