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Authors Suppressed Due to Excessive Length

but the whole-disk brightness of a bright planet is measured with a high signal to
noise ratio.

2.2.1 CCD– and CMOS–based cameras
Two major technologies are found for digital matrixes: CCD (Charge Coupled
Device) and CMOS (Complementary Metal-Oxide-Semiconductor). From the astronomer point of view, CCDs are based on charge displacements, pixel-to-pixel
towards a readout amplifier that converts charges into analog voltages. The digital
conversion is made by another electronic chip. The pixels of CMOS sensors are
able to keep their charge when they are read. This allows an increase of readout
speed but a part of the pixel area is used for microelectronics, so the pixel is less
sensitive to the photons compared to CCDs. Recent improvements of CMOS, particularly the reduction of the readout noise, lead to the concept of sCMOS (the s
means Scientific) terminology used by some camera manufacturers. There are three
main families of charge transfer technologies for CCDs [124]: the full frame (no
frame buffer), the frame transfer (a buffer matrix is used to store the image before
reading), the interline transfer (column buffers store the image before reading). A
full frame CCD does not lose any area of the matrix to record photons but it must
use a mechanical shutter to avoid smearing of charges during the transfer.
The CCD and CMOS technologies continue to be improved. The use of microlenses over the pixels now increases their quantum efficiency. Meanwhile CCD
chips now often use the interline transfer technology which prevents the utilization
of mechanical shutters. Interline CCDs with on-ship microlenses are currently the
basis of analog video cameras used in stellar occultation observations (see Sec. 5.3)
and in other fields (see Sec. 4.1, 4.2 and 4.4), when a fast acquisition with a very accurate timing is required (video astronomy is indeed one of the hardware solutions
for this issue see Sec. 2.4). The different models Watec 902H or PC164C are thus
sensitive and inexpensive cameras. A few others video cameras, such as the Watec
120N or the new Watec 910HX provide an additional integrating function allowing reaching deeper magnitudes at the price of time resolution. On the other hand,
digital Single Lens Reflex cameras (DSLR) use mainly CMOS. Manufacturers propose various acquisition functions via a dedicated data processing chip. The price is
attractive but the images rate is generally too low for planetary imaging.

2.2.2 EMCCD technology
One of the main constraints for groundbased high-resolution planetary imaging is
the limitation of angular resolution due to atmospheric turbulence distortion. The
main seeing parameters dependence (time, angular isoplanarity patch, and Fried
parameter dependence) shows that to overtake turbulence limitation, without the
use of expensive adaptive optics, the solution is to decrease exposure time and,
at the same time, increase the sensibility of the detector. CMOS technology due