Presentation on theme: "What is Pan-STARRS? Telescopes –4 x 1.8m –7 square degree FOV –possible sites on Mauna Kea and Haleakala Operation mode: –simultaneous imaging of the same."— Presentation transcript:
What is Pan-STARRS? Telescopes –4 x 1.8m –7 square degree FOV –possible sites on Mauna Kea and Haleakala Operation mode: –simultaneous imaging of the same field for transient/moving object detection –broad band optical imaging –multiple survey modes Detectors –1Bn pixels per camera –array of arrays –0.3 pixels –few second readout –<5e - read-noise Data-Processing System –Core pipeline will generate: snapshot images difference/summed images basic catalogs NEO system
Performance Summary Sensitivity (assuming 0.6 seeing) –T(R=24) = 58s –T(V=24.4) = 67s –T(R+V=24) = 31s 30s exposure -> 6000 sq deg / night Sky noise –7e/s/pixel from sky (R+V) –Read noise ~2-3e is negligible for t >~ 20s Astrometry –Sigma=0.07 (FWHM/0.6) / (SN/5) –Systematics limited by atmosphere
Small vs Large Apertures Why size matters: –small telescopes are cheaper for given collecting area –CCD costs scale with detector area (not N pixels ) Optimal design matches seeing to CCD resolution –rapid construction and low risk –Fast guiding for enhanced image quality –Low environmental impact
Trends Future dominated by detector improvements Total area of 3m+ telescopes in the world in m 2, total number of CCD pixels in Megapix, as a function of time. Growth over 25 years is a factor of 30 in glass, 3000 in pixels. Moores Law growth in CCD capabilities Gigapixel arrays on the horizon Improvements in computing and storage will track growth in data volume Investment in software is critical, and growing
For (D ~ 4 r 0 ) ~35% of light is in a single bright speckle guiding at ~10Hz gives PSF with diffraction limited core tip-tilt on large apertures is relatively ineffective D = 1.5m D = 8m D=4m
Detector Details – Orthogonal Transfer Orthogonal Transfer –remove image motion –high speed (few usec) Normal guiding (0.73) OT tracking (0.50)
File : C:\ZEMAX\panstars\PS-prelim-9.ZMX Title: Pan-STARRS preliminary design review Date : TUE DEC SURFACE DATA SUMMARY: Surf Comment Radius Thickness Glass Diameter Conic r**2 r**4 r**6 6 Primary MIRROR e-21 7 Secondary MIRROR e-19 9 LENS-1A F_SILICA LENS-1B LENS-2A F_SILICA LENS-2B FILTER-A Infin 20 F_SILICA FILTER-B Infin LENS-3A F_SILICA e e LENS-3B IMA CCD-ARRAY Infin 500 0
Performance in U and Y Optical Performance deteriorates at extreme ends of the optical region Using a curved filter helps by giving extra refractive power
Ghost Image Analysis Pupil ghosts Image ghosts
Fabrication of the aspheric Optics The asphericity of the mirrors is within established fabrication capability. Dewar window is an order of magnitude less aspheric than the Sloan window ( 1 mm vs. 8mm)
Listing of surface sag File : C:\ZEMAX\panstars\PS-prelim-9.ZMX Title: Pan-STARRS rounded Date : MON NOV Units are Millimeters. Semi diameter of surface 6: E+002. Best Fit Sphere curvature : E-004. Best Fit Sphere radius : E+003. Best Fit Sphere residual : E-002. (rms) Y-coord Sag BFS Sag Deviation Remove 0.0E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E E+000
Tolerance Analysis Sensitivity analysis of alignment Monte Carlo modeling
Wavefront Sensing and Telescope Collimation Tests with OPTIC using a calcite block to make extrafocal images OPTIC design has 0.5 disk at 4 separation PS design could be as much as an 8 disk at 10 separation, enough for resolution elements over pupil.
In/extra Focal Images for Pan-STARRS r = 1.6 deg, SS filter Nominal intra- and extra focal images, 4.4 diameter pupil 100 m secondary decenter 0.01 deg secondary tilt ExtraIntraExtra – Intra
Atmospheric Dispersion In the broad Solar System filter, atmospheric dispersion dominates other aberration for zenith distances over 10 deg.
PSF Area vs. Air Mass pixel trailing loss charge diffusion dispersion seeing
Design Pan-STARRS Post PDR 3, incorporating an ADC
A traditional ADC contains many additional air-glass surfaces and does not achieve acceptable image quality over the wide Pan-STARRS field. Therefore we did not seriously consider ADCs before PDR.
ADC Refractive indices match at 656 nm Zero deviation No added glass/air interfaces No large diameter rotating seals Relaxed tolerances on the flat surfaces Fused silica Siloxane Maximum correctionNo correction The design chosen has a rotating prism between fixed lenses. This avoids the large rotary seal and presents less of an engineering challenge and schedule risk.
ADC prototype during filling procedure
Design Pan-STARRS Final 2: ADC on maximum dispersion Note: Box is 5"x5"
At 75° zenith distance, the ADC fully corrects atmospheric dispersion