Tip-Tilt Guide Camera

The hardware for the SOAR Tip-Tilt Guide Camera consists of an E2V CCD39 detector mounted in a Peltier cooled head (small gold box), controlled by an SDSU-III controller (larger silver box). The two grey boxes contain the power supplies for the controller and Peltier cooler.	The Lab-VIEW based user interface for the Tip-Tilt guide camera developed at CTIO

The SOAR Tip-Tilt Guide cameras (TTGC) were built as turnkey systems by Astronomica Research Camera Inc. They are designed around the E2V technologies CCD39-01 CCD which has 80x80 24 microns pixels. This CCD has four very high performance low-readout noise amplifiers and a split-frame transfer architecture, allowing it to be read out at high speed with relatively low noise. The CCD is mounted in a small head including an integral 2-stage Peltier cooler. The CCD is controlled by an SDSU-III controller. It allos the CCD to be read out pixels rates as high as 2 microsec per pixel, allowing the full 80x80 image to be read out at ~240Hz, or a 32x32 pixel guide box to be read out at up to 900Hz while achieveing RON of < 4e-

The TTGC is controlled by custom LabVIEW based software developed by Rolando Cantarutti at CTIO. This allows the opperator to set the camera parameters (e.g. frame time, ROI size and binning), provides a real time display of the resulting image, and calculates the position of the guide star and guiding error signal which is used to drive the telescopes fast tertiary steering mirror, and provide slower corrections to the telescope mount in order to stay within the range of correction of the tertiary.

The basic performance parameters for the camera are given in the table below:

Detector Type	E2V technologies CCD-39-02 thinned, back Illuminated
Image Size	80x80
Pixel Size	24 microns/pixel = 0.077 arcsec/pixel
DQE	Wavelength (nm)  QE %    300  50  350  70  400  85  500  90  600  87  700  77  800  55  900  35  950  20  1000  10
Read Out Noise	3.5-3.8 e- RMS at 2 microsec per pixel
Dark Current	50e-/pix/sec @ -20C opperating temperature of Peltier Cooler
Read Out Rate	240Hz full frame, 900Hz for a 33x32 pixel centered ROI
Gain	1e/ADU
Charge transfer efficiency	99.9999

Actual Guiding performance remains to be characterised at this time.

Three seperate TTGC units are currently in use at SOAR, one for each Nasmyth ISB, and one for the SOAR Optical Imager. Because slightly different fore optics are used in each case the scale and field of view differs as shown in the following table.