Detector Mosaic Design Detector Mosaic Design Considerations for a Wide FOV Considerations for a Wide FOV

Drift-Scan Survey TelescopeDrift-Scan Survey Telescope

John T. McGrawJohn T. McGrawMark R. AckermannMark R. Ackermann

Peter C. ZimmerPeter C. ZimmerUniversity of New MexicoUniversity of New Mexico

andandLt. Eric GoldenLt. Eric Golden

AFRLAFRL

The Near Earth Space Surveillance Initiative The Near Earth Space Surveillance Initiative (NESSI)(NESSI)

NESSI is a collaboration between the University of New Mexico (CTI) and McDonald Observatory of The University of Texas at Austin (HET). The project is funded by AFRL.

UNM/USAFA Cooperative ResearchUNM/USAFA Cooperative Research

Design and implementationDesign and implementation

Data reduction and analysisData reduction and analysis

Follow-up observationsFollow-up observations

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CTI USAFA Capilla

RR Lyrae Star

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The CCD/Transit Instrument (CTI)The CCD/Transit Instrument (CTI)

1.8-m, f/2.2 parabolic 1.8-m, f/2.2 parabolic primaryprimary

Paul-Baker optical Paul-Baker optical systemsystem 3.96-m focal length3.96-m focal length 52 arcsec/mm field 52 arcsec/mm field

scalescale Existing thermally-Existing thermally-

compensating compensating structurestructure

The Paul-Baker Optical SystemThe Paul-Baker Optical System

Very wide FOV

Excellent images

Compact design

Proposed for LSST

Time-Delay and Integrate (TDI) Readout ModeTime-Delay and Integrate (TDI) Readout Mode

Advantages:

Stable telescope does not move

Constant gravity load

Instrumental signature averaged over rows

“Features:”

Meridian TDI adds to the PSF

Differential track rate

CTI and HET Survey GeometryCTI and HET Survey Geometry

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HET and CTI FOV

Elements of an astronomical surveyElements of an astronomical survey

Discover new objects and phenomenaDiscover new objects and phenomenaSynoptically monitor objectsSynoptically monitor objects MotionMotion VariabilityVariability

Provide a statistically significant, unbiased Provide a statistically significant, unbiased sample of objectssample of objectsDiscover targets of opportunityDiscover targets of opportunity Enable follow up observationsEnable follow up observations

The CCD/Transit Instrument (CTI II)The CCD/Transit Instrument (CTI II)

Meridian-pointing 1.8-m telescopeMeridian-pointing 1.8-m telescope

Images formed on multiple CCDs operated in Images formed on multiple CCDs operated in TDI modeTDI mode no moving partsno moving parts multiple optical/IR colors each nightmultiple optical/IR colors each night

Fully automated operationFully automated operation

Photometric imaging over 1 - 2° FOVPhotometric imaging over 1 - 2° FOV surveys ~120°surveys ~120°22 each night each night VV22.5 nightly detection limit22.5 nightly detection limit

Science DriversScience DriversSupernova detectionSupernova detection

AGN ReverberationAGN Reverberation

IR AstrometryIR Astrometry

Optical and Near IR AstrometryOptical and Near IR Astrometry

Single-image astrometry Single-image astrometry includes stars 90° apart – includes stars 90° apart – parallaxesparallaxesGoal: 3 mas rms per night Goal: 3 mas rms per night stellar centroidsstellar centroidsHET spectra – spectral HET spectra – spectral type and radial velocitytype and radial velocity

SN Ia: The universe is expanding.SN Ia: The universe is expanding.

Doppler shift Doppler shift measurements give measurements give higher recession higher recession velocities for more velocities for more distant galaxies.distant galaxies.

The rubber band The rubber band experiment.experiment.

The universe is expanding – Hubble’s Law.The universe is expanding – Hubble’s Law.Hubble’s Constant is the slope of this line.Hubble’s Constant is the slope of this line.

The slope determines the “age” of the universe.The slope determines the “age” of the universe.

We see the remnant of the Big Bang that initiated the We see the remnant of the Big Bang that initiated the universe in the cosmic microwave background.universe in the cosmic microwave background.

One way of visualizing an open, flat or closed universe.One way of visualizing an open, flat or closed universe.

The fate of the universe is determined by what’s in it.The fate of the universe is determined by what’s in it.

Type Ia supernovae are “standard candles.”Type Ia supernovae are “standard candles.”

Type Ia supernovae can measure cosmological distances.Type Ia supernovae can measure cosmological distances.

Supernovae at large distance map the former conditions of Supernovae at large distance map the former conditions of the universe.the universe.

The history of cosmic expansion provided by SNe Ia.The history of cosmic expansion provided by SNe Ia.

Interpreting cosmological parameter space can be tricky.Interpreting cosmological parameter space can be tricky.

The annotated version of the previous figure.The annotated version of the previous figure.

Active Galactic NucleiActive Galactic Nuclei

Discovery of Discovery of QuasarsQuasars

Quasar LensingQuasar Lensing

AGN ReverberationAGN Reverberation

Active Galactic NucleiActive Galactic Nuclei

The Nature of QuasarsThe Nature of Quasars

Active Galactic NucleiActive Galactic Nuclei

The “Standard Model”The “Standard Model” Accretion disc scale ~ 1 pcAccretion disc scale ~ 1 pc

Active Galactic NucleiActive Galactic Nuclei

AGN phenomenon is AGN phenomenon is ubiquitousubiquitous Milky Way?Milky Way? All galaxies?All galaxies? Evolution?Evolution?

Active Galactic NucleiActive Galactic Nuclei

Mapping: Model, Orientation, Time HistoryMapping: Model, Orientation, Time History Light travel timescale ~ 3 yearsLight travel timescale ~ 3 years Dynamical timescale ~ r/V ~ 10 – 100 yearsDynamical timescale ~ r/V ~ 10 – 100 years

The Obscure UniverseThe Obscure Universe

The outsider’s view of The outsider’s view of gravitational lensing:gravitational lensing:

The Obscure UniverseThe Obscure Universe

Geometry of Different Geometry of Different Optical pathsOptical paths Source geometrySource geometry Lens geometryLens geometry Source dust chemistrySource dust chemistry

Well-sampled light Well-sampled light curvescurves Optical path length Optical path length

measurementmeasurement Effects of microlensingEffects of microlensing Dust in lensesDust in lenses

The Obscure UniverseThe Obscure Universe

Luminosity variabilityLuminosity variability Days to yearsDays to years

Intrinsic variabilityIntrinsic variability

Optical path lengthOptical path length

MicrolensingMicrolensing Colley et al. 2002Colley et al. 2002

Active Galactic NucleiActive Galactic Nuclei

AGN ReverberationAGN Reverberation Mapping the scale, structure, and Mapping the scale, structure, and

time-dependent structure changes in time-dependent structure changes in the environs of massive black holesthe environs of massive black holes

Testing the standard model of AGNsTesting the standard model of AGNs Examples: N1275, N7742Examples: N1275, N7742

Active Galactic NucleiActive Galactic Nuclei

QuasarsQuasars 1° wide strip, 1° wide strip, αα = 8 hours (NGC) = 8 hours (NGC) 120°² 120°² 25 quasars/°² to B = 21 25 quasars/°² to B = 21 3000 quasars3000 quasars

Conservatism: 2° FOV, tilt to cover 10°, B fainter than 22 at Conservatism: 2° FOV, tilt to cover 10°, B fainter than 22 at S/N = 10, 2df data S/N = 10, 2df data all quasars all quasars

Galaxies (same geometry, B = 19.7)Galaxies (same geometry, B = 19.7) 18000 galaxies18000 galaxies

SNe (same geometry, B = 21 point source)SNe (same geometry, B = 21 point source) 100 ~ SNe/year100 ~ SNe/year

PSF Analysis: Motion-induced componentsPSF Analysis: Motion-induced components

Model input: 0.85 arcsec FWHM Moffatt function

Small Pixels Ameliorate Motion-Induced BlurSmall Pixels Ameliorate Motion-Induced Blur

Deconvolution Deconvolution kernel is fully kernel is fully deterministicdeterministic

Blur caused by:1. Discrete shifting of pixels

2. Curved celestial trajectories – α and δ

3. Differential track rate – all TDI operations

Design CriteriaDesign Criteria

Fully sample the PSF at the R bandpassFully sample the PSF at the R bandpassInclude near-IR bandpassesInclude near-IR bandpassesV, R and I optical bandpassesV, R and I optical bandpassesMultiple devices for greater dynamic rangeMultiple devices for greater dynamic rangeConfigure optics/focal plane to take advantage Configure optics/focal plane to take advantage of modal 0.85 arcsec seeing at McDonald of modal 0.85 arcsec seeing at McDonald ObservatoryObservatoryObserve Galactic north pole (Observe Galactic north pole (δδ=28°)=28°)Strip must intersect HET field of regardStrip must intersect HET field of regard

Analysis of Three Optical DesignsAnalysis of Three Optical Designs

Paul-BakerPaul-Baker And variants involving refractive correctorsAnd variants involving refractive correctors

Prime focusPrime focus Variants include differing numbers of refractive Variants include differing numbers of refractive

corrector elementscorrector elements

GregorianGregorian And variantsAnd variants

Astronomical Lidar for ExtinctionAstronomical Lidar for Extinction Photometric engineering dataPhotometric engineering data

The CCD/Transit Instrument (CTI II)The CCD/Transit Instrument (CTI II)Strawman Focal Plane MosaicStrawman Focal Plane Mosaic

Focal Plane Mosaic Strawman Alternatives (EEV CCDs)Focal Plane Mosaic Strawman Alternatives (EEV CCDs)

The CCD/Transit Instrument (CTI II)The CCD/Transit Instrument (CTI II)PerformancePerformance

CTI S/N (Strawman Mosaic)CTI S/N (Strawman Mosaic)

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The CCD/Transit Instrument (CTI II)The CCD/Transit Instrument (CTI II)PerformancePerformance

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Current Survey ComparisonsCurrent Survey ComparisonsVital StatisticsVital Statistics

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Sloan Digital Sky SurveySloan Digital Sky Survey SDSSSDSS 1500015000 0.400.40 ugrizugriz r < 23r < 23 11

2-micron All-Sky Survey2-micron All-Sky Survey 2MASS2MASS 4000040000 2.002.00 JHKJHK J < 15.8J < 15.8 11

Palomar-Quest SurveyPalomar-Quest Survey PQPQ 1500015000 0.880.88 UBIR/rizzUBIR/rizz R < 21R < 21 11

PAN-STARRSPAN-STARRS PSPS 1500015000 0.340.34 V+R/grizV+R/griz V+R < 24V+R < 24 1010

Large Synoptic Survey Large Synoptic Survey TelescopeTelescope LSSTLSST 1500015000 0.200.20 UBVRIUBVRI R < 24.5R < 24.5 3030

CCD/Transit Instrument IICCD/Transit Instrument II CTI IICTI II 300300 0.340.34 BVRIJHBVRIJH R < 22.5R < 22.5 100100

CTI II Bottom Line:Visible to mid-IR photometry in a single surveyComparable resolution and depth to other surveysSignificantly greater repeat observations for variability/astrometrySmaller total area, but widely distributed in galactic latitude and longitude due to nature of transit instrument surveySignificant increase in dynamic rangeSpectroscopic follow-up to same limiting magnitude with HET

The CCD/Transit Instrument (CTI II)The CCD/Transit Instrument (CTI II)SummarySummary

CTI II is being designed and builtCTI II is being designed and built Frontline Research – Science DriversFrontline Research – Science Drivers Technology transfer to other sky survey telescopesTechnology transfer to other sky survey telescopes

The “niche”The “niche” Photometric and astrometric precisionPhotometric and astrometric precision Repeated observations with one sidereal day cadenceRepeated observations with one sidereal day cadence Spectroscopic observations, including real-time targetsSpectroscopic observations, including real-time targets

Issues:Issues: Final optical design – f/5.5Final optical design – f/5.5 Detector mosaicDetector mosaic

Detector size, pixel size, need for deconvolutionDetector size, pixel size, need for deconvolution Curved channel, OTA devicesCurved channel, OTA devices

Bandpasses – optical and IRBandpasses – optical and IR

The CCD/Transit Instrument (CTI)The CCD/Transit Instrument (CTI)A Sample SweepA Sample Sweep

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