HARPS uses a mosaic of two CCDs, one optimized for the red named Jasmine, or CCD # 78, and one optimized for the blue named Linda, or CCD # 77.
A slight tilt of the CCDs with respect of the horizontal plane allows to loose only one order (# 115) within the CCD gap.
The two CCDs are read by one amplifier each. A description of the detector system can be found in this page.
There are two readout modes currently offered. Their characteristics, as measured at the telescope, are displayed in the table below. They can differ slightly from what has been measured in the test bench in Garching. The mode of 50kpix/s has been abandoned because, as measured at the telescope, it shows a large readout noise.
|Readout mode||Readout frequency||Readout time||Average gain||Average RON (e-)|
Below are the links to the monitoring pages of the two CCDs. The CCD "health test" is performed once per week using LEDs located just above the CCDs. A more stable source like the beta light cannot be used as it would require to break the vacuum of the vacuum vessel, a lenghty operation that would compromise the stability of the instrument.