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2002 ASIAA Summer Student Program. TAOS photometry using IRAF. Shao-Er Chuang Department of Earth sciences, National Taiwan Normal University, Supervisor Jen-Hung Wang, Sun-Kun King Institute of Astronomy and Astrophysics, Academia Sinica. Outlines. Introduction Data reduction
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2002 ASIAA Summer Student Program TAOS photometry using IRAF Shao-Er Chuang Department of Earth sciences, National Taiwan Normal University, Supervisor Jen-Hung Wang, Sun-Kun King Institute of Astronomy and Astrophysics, Academia Sinica
Outlines • Introduction • Data reduction • Preliminary result • Conclusion • future
Introduction • TAOS project To detect occultations cause by Kuiper Belt Objects. The observation will help us to understand the planets formation and dynamical evolution of the outer solar system.
Introduction • Unique observation technique zipper mode So require special analysis method. • What’s Zipper mode?
Illustration • A simple illustration for occultation event
4 3 2 1 Illustration shift Readout
TAOS Zipper mode imageRowblocks GIF animation Y X 0 256 512 512 768 1024 Row block size : 2048 x 32 pixels Exposure time : 0.2 sec
TAOS 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
TAOS 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
Data reduction • IRAF Aperture Photometry Package • IRAF Scripts • Fortran 90
Photometry flowchart Input Image & set parameter Calculate Mag StdDev Find Alarm Daofind Phot Row block image input Produce report Append data to file continue Recheck stop
Preliminary result • Zipper mode stars light curve
Preliminary result • Zipper mode mag & mag error StdDev relation
Suspected occultation event criteria • Magnitude are missing in IRAF phot result The mag of the star is shown as INDEF • Magnitude fluctuation greater than 4 times of magnitude standard deviation
Conclusion • Sky background is too bright A source exposes 0.2 sec, but the sky background exposes 12.8 sec . Using zipper mode will lower S/N ratio of data. • Tracking error • How to reduce ? (1) Enlarge Zipper mode shift pixel length, may use 128 pixels or 256 pixels . But it will cause the data will expand to 4 times or 8 times large. (2) Put a mask in front of CCD, just allow target stars light go through. It needs lots of masks, and lots tiny holes on those masks.
Sky background getting brighter and brighter Source expose 0.2sec Sky background expose 0.2 x 64 = 12.8sec
Future works • To identify zipper mode field stars To estimate limit magnitude & calibrate by reference stars. Create a database of TAOS. • Image process to improve S/N Subtract dark current and bias . • To make photometry more efficient To achieve real-time analyze. • Decide all criteria for TAOS image
Acknowledgements I would like to thank the members in IAA who gave me instructions ,precious opinions and helps. Especially, thanks to Jen-Hung Wang, Sun-Kun King, Shiang-Yu Wang, Bau-Ching Hsieh, Frank, Joshua, Tony.