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 Npixels)• 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 m2, 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.

• Moore’s 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 r0) ~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 = 1.5mD = 1.5m D = 8mD = 8mD=4mD=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 9 2003

SURFACE DATA SUMMARY:

Surf Comment Radius Thickness Glass Diameter Conic r**2 r**4 r**6

6 Primary -7850 -2257.85 MIRROR 1800 -1.52934 2.24e-21

7 Secondary -6658 2057.85 MIRROR 900 -18.6695 4.68e-19

9 LENS-1A 994.5 60 F_SILICA 640 0

10 LENS-1B 1732.7 10 640 0

11 LENS-2A 801.7 45 F_SILICA 620 0

12 LENS-2B 540.0 815 620 0

13 FILTER-A Infin 20 F_SILICA 530 0

14 FILTER-B Infin 100 530 0

15 LENS-3A -1928.5 50 F_SILICA 520 0 4.02e-10 1.51e-15

16 LENS-3B -1790.1 198.07 520 0

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

Distortion

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.ZMXTitle: Pan-STARRS roundedDate : MON NOV 24 2003

Units are Millimeters.

Semi diameter of surface 6: 9.000000E+002. Best Fit Sphere curvature : -1.269040E-004.Best Fit Sphere radius : -7.879973E+003. Best Fit Sphere residual : 2.979204E-002. (rms)

Y-coord Sag BFS Sag Deviation Remove 0.0E+000 0.00000E+000 0.00000E+000 0.00000E+000 6.31004E-002 5.0E+001 -1.59234E-001 -1.58631E-001 6.03222E-004 6.37036E-002 1.0E+002 -6.36929E-001 -6.34545E-001 2.38346E-003 6.54839E-002 1.5E+002 -1.43305E+000 -1.42779E+000 5.25245E-003 6.83528E-002 2.0E+002 -2.54755E+000 -2.53848E+000 9.06295E-003 7.21633E-002 2.5E+002 -3.98035E+000 -3.96674E+000 1.36087E-002 7.67091E-002 3.0E+002 -5.73137E+000 -5.71275E+000 1.86243E-002 8.17247E-002 3.5E+002 -7.80049E+000 -7.77670E+000 2.37849E-002 8.68854E-002 4.0E+002 -1.01875E+001 -1.01588E+001 2.87063E-002 9.18067E-002 4.5E+002 -1.28924E+001 -1.28595E+001 3.29439E-002 9.60444E-002 5.0E+002 -1.59149E+001 -1.58790E+001 3.59936E-002 9.90940E-002 5.5E+002 -1.92549E+001 -1.92176E+001 3.72901E-002 1.00390E-001 6.0E+002 -2.29121E+001 -2.28759E+001 3.62077E-002 9.93081E-002 6.5E+002 -2.68862E+001 -2.68542E+001 3.20589E-002 9.51593E-002 7.0E+002 -3.11771E+001 -3.11530E+001 2.40945E-002 8.71949E-002 7.5E+002 -3.57844E+001 -3.57729E+001 1.15029E-002 7.46033E-002 8.0E+002 -4.07078E+001 -4.07144E+001 -6.59053E-003 5.65098E-002 8.5E+002 -4.59470E+001 -4.59782E+001 -3.11241E-002 3.19762E-002 9.0E+002 -5.15017E+001 -5.15648E+001 -6.31004E-002 0.00000E+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 50-100 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

100m secondary decenter

0.01 deg secondary tilt

Extra Intra Extra – 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 correction No 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

Telescope Studies

• Vertex RSI, Richardson TX

– Common alt-az

– Common equatorial

• EOST, Tucson AZ

– Common alt-az

– Independent alt-az

– Independent equatorial

Haleakala

Schematic of EOS Ice Dome as PS1 Dome

PS1EOS Ice Dome

MAGNUM

UKIRT

CFHT

Mauna Kea

Conceptual Configurations for Pan-STARRS-4 in the UH 2.2 m telescope building