using delphi for weak lensing measurements: science return and mirror size
DESCRIPTION
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. Orbit: 600 km Sun Synchronous, 97.79 ° Estimated observatory mass (spacecraft plus instruments): 205 kg - PowerPoint PPT PresentationTRANSCRIPT
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.
€
γ1
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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?