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Canopus is the Adaptive Optics bench of GeMS . Below we described the characteristics of the main component of Canopus.
Canopus is equipped with a set of calibration sources. These sources are used to perform all the day-time calibrations, and to exercise the system in a controlled environment. The set of calibration sources are:
GeMS uses three Deformable Mirrors (DMs) conjugated respectively at 0km, 4.5km and 9km. The characteristics of the DMs are summarized in the table below:
These DMs are based on a piezo-stack technology (developed by CILAS). The DM electronics was made by Cambridge Innovations.
The Tip/Tilt Mirror Assembly is composed of a custom Tip/Tilt stage, a Silicon Carbide lightweighted mirror, a kinematic mounting interface for the Tip/Tilt Stage, and the assembly aluminum mount. Our TT mirror is located just downstream from DM0, and has a stroke of +/- 1.4 arcsec, with a bandwidth of 400Hz. It's a Physik Instrument device.
Science Beam Splitter Assembly
The science dichroic let the NIR through to the science instrument and reflects everything downward of 1 micron into the WFSs environment. The mechanism has 2 positions: the second dichroic has a cutoff at 850nm, to allow science at z band.
Science Atmospheric Dispersion Compensator
At large zenith angle, a compensation for atmospheric refraction within the science instrument bandpass (for broadband filters) will be needed. This can be done via the science Atmospheric Dispersion Compensator (ADC). The Science ADC can be IN or OUT of the optical path. If it is not really required, it is recommended to leave it OUT, as it affects the transmission.
Laser notch filter
Canopus is using five Laser Guide Star Wave-Front Sensors (LGSWFS) each one looking at one LGS. Characteristics of these LGSWFS are described in the table below:
LGS WFS CCDs
LGS WFS Zoom
This device includes three TTWFS, each one a quadcell detector using Avalanche Photodiodes (APDs). Each one can be moved into position using X and Y linear stages. To facilitate dithering and insure the relative positioning of each probe w.r.t the other ones, probe #1 and #2 are actually located on top of probe #3. Thus, to dither, we need to move only probe #3 (#1 and #2 will move with it). Probe 3 can span the whole 2 arcmin field. Probe 1 is limited to the top-part, and probe 2 to the bottom part.
Slow Focus Sensor (SFS)