P3K WFS development meeting #3 V VelurCaltech Optical Observatories Pasadena, CA /09/2007

Agenda TT sensor design. Multiple TT stars? - RTC issues, WFE budget. Truth sensor (for focus and astigmatism) - what kind? what band?

Plate scale selection for TT sensor: Native PALAO plate scale = 381  /arcsec. HgCdTe detector has 18  pixels i.e. raw plate scale = 47 mas/pixel H-band ( =1.65mm) spot size = /D = 68 mas So for a simple 2x2 quadcell this will work for I, J and H bands. The sensitivity goes up (at the cost of dynamic range) with wavelength. The idea is to see if we can use the whole chip mmx36.8 mm = 97 arcsec.

TT sensor concept The #s on the previous page suggest that it may be a possibility to go directly onto the chip and use the entire chip to acquire stars over a ~ 90 arcsec FoV. In principle we could use multiple TT stars if the RTC would allow it.

Zemax design (90” FoV)

Spot diagram