Coordination Team: THOMAS KITCHING, ADAM AMARA, SARAH BRIDLE, MANDEEP GILL, CATHERINE HEYMANS,

2. Coordination Team: THOMAS KITCHING, ADAM AMARA, SARAH BRIDLE, MANDEEP GILL, CATHERINE HEYMANS, RICHARD MASSEY, BARNABY ROWE, LISA VOIGT Advisory Team: SREE BALAN, GARY BERNSTEIN, MATTHIAS BETHGE, FREDERIC COURBIN, MARC GENTILE, STEFAN HARMELING, ALAN HEAVENS, MICHAEL HIRSCH, RESHAD HOSSEINI, DONNACHA KIRK, KONRAD KUIJKEN, RACHEL MANDELBAUM, BABACK MOGHADDAM, GULDARIYA NURBAEVA, STEPHANE PAULIN-HENRIKSSON, ANAIS RASSAT, JASON RHODES, BERNHARD SCHOLKOPF, TIM SCHRABBACK, JOHN SHAWE-TAYLOR, MARINA SHMAKOVA, ANDY TAYLOR, MALIN VELANDER, LUDOVIC VAN WAERBEKE, DUGAN WITHERICK, DAVID WITTMAN

3. The Challenge of Measuring Shapes • 

4. Typical galaxy used for cosmic shear analysis Typical star Used for finding Convolution kernel Slide from S. Bridle

5. Cosmic Lensing gi~0.2 Real data: gi~0.03 5/19 Slide from S. Bridle

6. Atmosphere and Telescope Convolution with kernel Real data: Kernel size ~ Galaxy size 6/19 Slide from S. Bridle

7. Pixelisation Sum light in each square Real data: Pixel size ~ Kernel size /2 7/19 Slide from S. Bridle

8. Noise Mostly Poisson. Some Gaussian and bad pixels. Uncertainty on total light ~ 5 per cent 8/19 Slide from S. Bridle

9. Need to measure shear to 10-3

10. Current Methods •  •  •    

11. STEP : Shear Testing Programme •  •  •  •  •  •  •  • 

12. Heymans et al., 2006; Massey et al., 2007 & Kitching et al., 2008 KSB

13.    •  •  •  •  •  • 

15. Quality Factor Kitching et al., 2008 (form filling functions); Amara & Refregier (2007)

16. 7 non-lensing participants Q~1000 in some regimes

17. GREAT08 : Stacking Procedure is Important Average Data Individual Object Statistic Ensemble Statistic Average Estimators Winning Methods (Q=1000) Stacked the Data

18. STEP 2006 2010 2008

19.  •  • 

20. Massey et al. 2008 Fu et al. 2008

22.  •  •  •  Bonus Star Challenge: Reconstruct the PSF at non-star positions

23. Take Part and Help Cosmology •  •  •  •  •  •  •  • 

24. http://www.greatchallenges.info/ GREAT10 Handbook, Kitching et al., 2010

25. http://www.greatchallenges.info/ “Every time the amount of data increases by a factor of ten we should totally rethink the way we analyze it” Jerome Freidman, Data Mining and Statistics, 1997