Using DELPHI for Weak Lensing Measurements: Science Return and Mirror Size Jes Ford, JPL, UNR SURF /21/07 Mentor: Jason Rhodes Co-mentor: David Johnston Jes Ford, JPL, UNR SURF /21/07 Mentor: Jason Rhodes Co-mentor: David Johnston

DELPHI: Background Originally a midex mission planned by Jason Rhodes  Orbit: 600 km Sun Synchronous, 97.79°  Estimated observatory mass (spacecraft plus instruments): 205 kg  Estimated payload power consumption: < 50 W  Mission duration and launch constraints: 2 years / Pegasus  Sky coverage: 21,000 deg 2 over two years  Frequency: Visible  Temperature: Telescope – ambient, Detectors – 170 K  Pointing requirements: ~ milliarcseconds  Data rate to ground: 54 GB/day  Orbit: 600 km Sun Synchronous, 97.79°  Estimated observatory mass (spacecraft plus instruments): 205 kg  Estimated payload power consumption: < 50 W  Mission duration and launch constraints: 2 years / Pegasus  Sky coverage: 21,000 deg 2 over two years  Frequency: Visible  Temperature: Telescope – ambient, Detectors – 170 K  Pointing requirements: ~ milliarcseconds  Data rate to ground: 54 GB/day TRADEOFFS:  Orbit Selection  L2 vs. Sun-Synchronous  Thermally stable orbits  Telecommunications requirements increase subsytem mass for L2 mission  Pegasus does not have the performance to place a s/c in an L2 halo orbit  Scanning Strategy  Drifting vs. Step-and-Stare  Drifting strategy works best with L2 orbit  Combination of integration time and sun-synchronous orbit require step-and-stare scanning

DELPHI: Trade Studies  Telescope Design  Mirror diameter  0.5 m, 0.75 m  Three-mirror anastigmat vs. Cassegrain  Plate scale and focal length  15 m, 20 m  Detector / Pixel Sizes  NIR HgCdTe Hawaii 2RG  E2V visible, frame transfer CCDs  Buses  Ball Aerospace  STP-IV  Orbital Science Corp.  MicroStar MIRROR SIZE IS A COST DRIVER!

DELPHI: Current Status  NASA recently announced small midex (SMEX) mission opportunity - not MIDEX  DELPHI cannot fit tight budget constraints  However, since Mirror size is main factor in the cost of a telescope, it is important to know how small of a mirror is still worthwhile to launch  MY PROJECT: what is the minimum mirror size that can recover weak lensing data reliably?  NASA recently announced small midex (SMEX) mission opportunity - not MIDEX  DELPHI cannot fit tight budget constraints  However, since Mirror size is main factor in the cost of a telescope, it is important to know how small of a mirror is still worthwhile to launch  MY PROJECT: what is the minimum mirror size that can recover weak lensing data reliably?

Image Simulation Parameters  Created using Shapelets  Pixels: 4096 x 4096 pix  Optical Filter: Wide filter centered on I-band  Input Shear:, no shear  PSF shape: roughly circular PSF, based on SNAP’s telescope design  PSF size: 2 pixels per FWHM  Throughput: peak throughput ~70%  Created using Shapelets  Pixels: 4096 x 4096 pix  Optical Filter: Wide filter centered on I-band  Input Shear:, no shear  PSF shape: roughly circular PSF, based on SNAP’s telescope design  PSF size: 2 pixels per FWHM  Throughput: peak throughput ~70%

Image Variations  Mirror Sizes: range from 20 cm m in diameter, in 20 cm increments  2 sets: - constant exposure time (1500s) - constant photon flux (varying exposure times, 1500s at 1.2 m)  Separate Galaxy and Stellar images created  Total of 23 star/galaxy image pairs  Mirror Sizes: range from 20 cm m in diameter, in 20 cm increments  2 sets: - constant exposure time (1500s) - constant photon flux (varying exposure times, 1500s at 1.2 m)  Separate Galaxy and Stellar images created  Total of 23 star/galaxy image pairs

Sample Images 2.0 m mirror, 1500s exposure 40 cm mirror, 1500s exposure

Steps of Analysis  Objects detected and catalogue created using Source Extractor  Object moments recalculated using RRG method  Stellar images used to measure the PSF moments  PSF is removed from the galaxy images (RRG)  Bad galaxies are cut based on: moments, ellipticity, size compared to PSF size, signal-to-noise ratio (RRG)  Shear and shear error are measured from the galaxy images (RRG)  Plots created to analyze number of useful galaxies (those that make the cuts) as a function of mirror size  Plots created to analyze measured shear and error as a function of mirror size  Objects detected and catalogue created using Source Extractor  Object moments recalculated using RRG method  Stellar images used to measure the PSF moments  PSF is removed from the galaxy images (RRG)  Bad galaxies are cut based on: moments, ellipticity, size compared to PSF size, signal-to-noise ratio (RRG)  Shear and shear error are measured from the galaxy images (RRG)  Plots created to analyze number of useful galaxies (those that make the cuts) as a function of mirror size  Plots created to analyze measured shear and error as a function of mirror size

RESULTS 1: Number of useful galaxies as a function of mirror size  Useful galaxies are those that survive the cuts and are used to measure the shear  Number of galaxies has been normalized to number per square arcminute of sky Diamonds: constant exposure time simulations Crosses: constant flux simulations

RESULTS 2: Measured Shear as a function of Mirror size

Continuing Research  Currently processing set of 143 simulations with non-zero input shear: - = 0, = -5, -3, -1, 0, 1, 3, 5 % - Mirror Sizes: 0.4 m m in 40 cm increments - one set at constant exposure time (1500s) - one set at constant flux  Images need to be analyzed by others using methods other than RRG… contact Jason Rhodes.  Currently processing set of 143 simulations with non-zero input shear: - = 0, = -5, -3, -1, 0, 1, 3, 5 % - Mirror Sizes: 0.4 m m in 40 cm increments - one set at constant exposure time (1500s) - one set at constant flux  Images need to be analyzed by others using methods other than RRG… contact Jason Rhodes.

Acknowledgements Many many thanks to:  Dr. Jason Rhodes, my mentor  Dr. David Johnston, co-mentor  Dr. Richard Massey, writer of Shapelets simulation pipeline  Dr. Jason Rhodes, my mentor  Dr. David Johnston, co-mentor  Dr. Richard Massey, writer of Shapelets simulation pipeline

Questions?