Using DELPHI for Weak Lensing Measurements:

Science Return and Mirror Size

Using DELPHI for Weak Lensing Measurements:

Science Return and Mirror Size

Jes Ford, JPL, UNR

SURF 2007

8/21/07

Mentor: Jason Rhodes

Co-mentor: David Johnston

Jes Ford, JPL, UNR

SURF 2007

8/21/07

Mentor: Jason Rhodes

Co-mentor: David Johnston

DELPHI: BackgroundOriginally a midex mission planned by Jason Rhodes

DELPHI: BackgroundOriginally 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 deg2 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 deg2 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

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 StudiesDELPHI: 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

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 StatusDELPHI: 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 ParametersImage 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%€

γ=[0,0]

Image VariationsImage Variations

Mirror Sizes: range from 20 cm - 2.4 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 - 2.4 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 ImagesSample Images

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

Steps of AnalysisSteps 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

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

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

RESULTS 2: Measured Shear as a function of Mirror size

Continuing ResearchContinuing Research

Currently processing set of 143 simulations with

non-zero input shear:

- = 0, = -5, -3, -1, 0, 1, 3, 5 %

- = 0, = -5, -3, -1, 0, 1, 3, 5 %

- Mirror Sizes: 0.4 m - 2.4 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 %

- = 0, = -5, -3, -1, 0, 1, 3, 5 %

- Mirror Sizes: 0.4 m - 2.4 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.

€

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γ1

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γ2

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γ2

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γ= γ1,γ 2[ ]

AcknowledgementsMany many thanks to:

AcknowledgementsMany 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?Questions?