Taiwan America Occultation Survey Taiwan America Occultation Survey TAOSTAOS2002/8/282002/8/28

TAOS photometry using IRAFTAOS photometry using IRAF

Shao-Er ChuangShao-Er ChuangDepartment of Earth sciences, National Taiwan Normal University, Department of Earth sciences, National Taiwan Normal University,

SupervisorSupervisorJen-Hung Wang, Sun-Kun KingJen-Hung Wang, Sun-Kun King

Institute of Astronomy and Astrophysics, Academia Sinica Institute of Astronomy and Astrophysics, Academia Sinica

2002 ASIAA Summer Student Program

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OutlinesOutlines

IntroductionIntroductionData reductionData reductionPreliminary resultPreliminary resultConclusionConclusionfuturefuture

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IntroductionIntroduction

TAOS projectTAOS project To detect occultations cause by Kuiper Belt Objects.To detect occultations cause by Kuiper Belt Objects. The observation will help us to understand the planets forThe observation will help us to understand the planets for

mation and dynamical evolution of the outer solar systemation and dynamical evolution of the outer solar system. m.

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Unique observation techniqueUnique observation technique

zipper modezipper mode So require special analysis method.So require special analysis method.

What’s Zipper mode?What’s Zipper mode?

IntroductionIntroduction

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IIllustrationllustration

A simple illustration for occultation eA simple illustration for occultation eventvent

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IIllustrationllustration

Readout

shift

1

2

3

4

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TAOS Zipper mode imageTAOS Zipper mode imageRowblocks GIF animationRowblocks GIF animation

X

0 512256

512 768 1024

Y

Row block size : 2048 x 32 pixels

Exposure time : 0.2 sec

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TAOS Zipper mode imageTAOS Zipper mode image

Partial of original image size : 1024 x 768 pixels

Original image size : 2048 x 18048 pixels

File name : 020508_zipper_3002.fit

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TAOS Zipper mode imageTAOS Zipper mode image

Partial of original image size : 1024 x 768 pixels

Original image size : 2048 x 18048 pixels

File name : 020508_zipper_3002.fit

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Low signal to noise ratioLow signal to noise ratio

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Data reduction Data reduction

IRAF Aperture Photometry PackageIRAF Aperture Photometry Package IRAF ScriptsIRAF Scripts Fortran 90Fortran 90

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Photometry flowchartPhotometry flowchartInput Image & set parameter

Daofind

Phot Producereport

Calculate Mag StdDev

Row block image input

Append datato file

continue

Find Alarm

stop

Recheck

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Preliminary resultPreliminary result Zipper mode stars light curveZipper mode stars light curve

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Preliminary resultPreliminary result Zipper mode mag & mag error StdDev relatioZipper mode mag & mag error StdDev relatio

nn

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Suspected occultation event criteriaSuspected occultation event criteria

Magnitude are missing in IRAF phot result Magnitude are missing in IRAF phot result The mag of the star is shown as INDEF The mag of the star is shown as INDEF Magnitude fluctuation greater thanMagnitude fluctuation greater than 4 times of magnitude standard deviation 4 times of magnitude standard deviation

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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Some false alarmsSome false alarms

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ImageImage Photometry Photometry timestimes

SuspectedSuspected

OccultationOccultation

eventsevents

False False

alarmalarm

ratioratio

MagINDEFMagINDEF Mag>4Mag>4

020508_zipper1_3002.fit020508_zipper1_3002.fit 85x20085x200 33 2020 0.135%0.135%020508_zipper1_3003.fit020508_zipper1_3003.fit 89x20089x200 22 88 0.056%0.056%020508_zipper1_3004.fit020508_zipper1_3004.fit 82x20082x200 4242 99 0.310%0.310%010719_zipperc_a020.fit010719_zipperc_a020.fit 141x100141x100 66 2727 0.234%0.234%010719_zipperc_a021.fit010719_zipperc_a021.fit 144x100144x100 7777 1212 0.618%0.618%010719_zipperc_a025.fit010719_zipperc_a025.fit 139x100139x100 11 33 0.028%0.028%010719_zipperc_a030.fit010719_zipperc_a030.fit 132x100132x100 22 77 0.068%0.068%

SummerySummery

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Conclusion Conclusion Sky background is too bright Sky background is too bright A source exposes 0.2 sec, but the sky background exposes 12.8 A source exposes 0.2 sec, but the sky background exposes 12.8

sec .sec . Using zipper mode will lower S/N ratio of data. Using zipper mode will lower S/N ratio of data. Tracking errorTracking error How to reduce ?How to reduce ? (1) Enlarge Zipper mode shift pixel length, may use 128 pixels or (1) Enlarge Zipper mode shift pixel length, may use 128 pixels or 256 pixels .256 pixels . But it will cause the data will expand to 4 times or 8 times But it will cause the data will expand to 4 times or 8 times

large.large. (2) Put a mask in front of CCD, just allow target stars light go (2) Put a mask in front of CCD, just allow target stars light go through.through. It needs lots of masks, and lots tiny holes on those masks. It needs lots of masks, and lots tiny holes on those masks.

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No re-find center stars light curveNo re-find center stars light curve

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Re-find center stars light curveRe-find center stars light curve

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Sky background getting brighter and brighter Sky background getting brighter and brighter

Source expose 0.2secSource expose 0.2sec

Sky background expose 0.2 x 64 = 12.8secSky background expose 0.2 x 64 = 12.8sec

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Future works Future works To identify zipper mode field starsTo identify zipper mode field stars To estimate limit magnitude & calibrate by To estimate limit magnitude & calibrate by reference stars.reference stars.

Create a database of TAOS.Create a database of TAOS. Image process to improve S/NImage process to improve S/N Subtract dark current and bias .Subtract dark current and bias . To make photometry more efficient To make photometry more efficient To achieve real-time analyze.To achieve real-time analyze. Decide all criteria for TAOS imageDecide all criteria for TAOS image

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AcknowledgementsAcknowledgements

I would like to thank the members in IAA I would like to thank the members in IAA who gave me instructions ,precious opinwho gave me instructions ,precious opinions and helps.ions and helps.

Especially, thanks to Jen-Hung Wang, SuEspecially, thanks to Jen-Hung Wang, Sun-Kun King, Shiang-Yu Wang, Bau-Ching n-Kun King, Shiang-Yu Wang, Bau-Ching Hsieh, Frank, Joshua, Tony.Hsieh, Frank, Joshua, Tony.

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