STEP Workshop 2005: Schedule
STEP Workshop Schedule Travel to JPL Accommodation Participants

Monday 25th July

DAY 1 : Shear measurement methods

Session 1: 9.00 - 10.30
JPL Welcome15 mins
STEP IntroductionJason and Catherine 5 mins
KSB+ OverviewHenk Hoekstra 25 mins
E & B modes in the DPS in the context of STEP1Marco Hetterscheidt 15 mins
KSB+ discussion lead by Henk Hoekstra
  • What is the best way to implement the KSB+ formula?
  • What has been learnt from the comparison of different KSB+ implementations?
  • Is hfindpeaks or SExtractor optimal for KSB+ analyses?
  • Weighting schemes and source selection issues.
  • Has STEP 1 shown that we should now be focusing our efforts on new methods, or on understanding and further improving KSB+?
Session 2: 10.50 - 13.00
RRGJason Rhodes 20 mins
K2KHakon Dahle 20 mins
Shapelets 1Richard Massey 20 mins
Shapelets 2Konrad Kuijken 20 mins
Im2shapeSarah Bridle 20 mins
Session 3: 14.00 - 15.40
ElliptoVera Margoniner 20 mins
BJ02Gary Bernstien 20 mins
Testing the accuracy of weak lensing analysis: The case for BJ02Reiko Nakajima 25 mins
REGLENSRachel Mandelbaum 20 mins
Session 4: 16.00 - 17.30

General methods discussion and summary lead by Gary Bernstein

  • What are the fundamental differences between the different methods? (summary)
  • Are some methods optimal for certain weak lensing applications?
PSF fitting discussion lead by Mike Jarvis
  • PCA analysis (opening talk)
  • KSB and the ACS PSF (slides from Tim Schrabback, presented by Marco Hetterscheidt)
  • Improvements on simple polynomial models
  • PSF interpolation - is this more of a problem for shapelets/Im2shape etc than KSB?
  • How important is the data reduction method?

Tuesday 26th July

DAY 2 : STEP results and workshop discussion

Session 1: 9.00 - 10.30
Introduction to SkyMaker and the STEP 1 simulations Ludovic Van Waerbeke 20 mins
Introduction to Shapelet morphology and the STEP 2 simulationsRichard Massey 20 mins
Update on the shapelet space-based simulationsWill High 10 mins
A summary of the results from STEP 1Catherine Heymans 15 mins
Session 2: 10.50 - 13.00

The preliminary results of the STEP 2 analysis; Catherine Heymans.
Discussion on the STEP 2 results lead by Richard Massey.

  • What changes have been applied to the methods since STEP 1?
  • What are the differences in the results?
  • Is morphology playing an important role?
  • Weight bias
  • Selection bias
  • Drizzled/non-drizzled images
Session 3: 14.00 - 15.30

Discussion on the future of STEP lead by Catherine Heymans

  • What have we learnt from STEP so far?
  • Where do we go next? More simulations? Data exchange?
  • Should we form sub-groups to focus on particular issues?
  • New telescopes are creating data reduction pipelines that include weak shear measurement. Which method would you/we recommend them to use?
  • What information/software would people require in order to implement from scratch the different shear measurement methods discussed?
  • Publications
  • Future funding for STEP?
Session 4: 16.00 - 17.00

Discussion on future weak lensing surveys lead by Jason Rhodes.
Please bring a few paper slides with you to describe any upcoming projects that you are involved with. Are there any new concepts and ideas for surveys that aren't already in the pipeline?

Wednesday 27th July

DAY 3: Statistics and Theory

Session 1: 9.00 - 10.30
Higher order statistics and diagnostic statistical toolsLudovic Van Waerbeke 30 mins
Weak lensing simulationsMartin White 25 mins
Discussion item: What is the degree of independence between higher and lower order measures of shear?

Session 2: 10.50 - 12.00
Ray Tracing simulationsBhuvnesh Jain 25 mins
Weak lensing to distinguish dark energy. Plus new work on the non-linear power spectrumEric Linder 25 mins
Session 3: 14.00 - 15.30
Discussion on the theoretical issues facing weak lensing analyses lead by Martin White

N-body simulations

  • ray tracing vs born approximation
  • numerical convergence, accuracy/computational cost
  • grids and interpolation
Extra physics
  • how (much) will this limit us
  • approximate modeling of extra physics
Metrics to compare theory and data
  • for overall power, 2-pt shear xi(r) seems optimal
  • what is the best measure of non-Gaussian information?
  • + radical compression of huge amount of low S/N data
Intrinsic alignments, source contamination
  • how do we deal with issues like this in the D/A
Session 4: 15.50 - 16.30
Summary and conclusion from Richard Ellis

STEP Party: Evening, time TBD during meeting
Location: Chez Ellis, Pasadena

The SNAP meeting will continue on Thursday and Friday (28th-29th July) including a public lecture (Friday 12.00 - 13.00) by Gary Bernstein

STEP Workshop at JPL organised by:
Jason Rhodes: jrhodes[at]
Catherine Heymans: heymans[at]