The third GRavitational lEnsing Accuracy Testing challenge, or GREAT3, is a blind data analysis competition held by the world-wide weak lensing community to test weak lensing measurement algorithms.

All simulated data are available, downloadable from our server on the GREAT3 Leaderboard web site, where you can also find the scores of all the challenge participants.

The challenge began in October 2013 and ended on April 30, 2014 (see the timeline page).

The GREAT3 Final Meeting took place on 27-29 May 2014 at Carnegie Mellon University, Pittsburgh PA

With several major astronomical surveys beginning to make large-scale cosmological weak lensing measurements in 2013 in order to better understand our cosmological model (including the mysterious dark matter and dark energy), we hope this challenge will prove to have played an important role in identifying promising measurement algorithms and quantifying their performance.

For more information about the challenge, see the menu items above, particularly our links page where you can see how to access the data, submit results, get the software included with the release, and read the challenge handbook.

The GREAT3 "real_galaxy" experiment data are now available!

Hmmm Pizza!

Simulation data for the realistic galaxy morphology experiment in GREAT3 is now online and available via the GREAT3 Leaderboard site:

Three out of five of the GREAT3 experiment datasets are now fully public (control, multiepoch, & real_galaxy; A.K.A. Vanilla, Dim Sum, & Pizza!), with only the variable PSF (Pop Corn) and full (all effects: Buffet!) datasets still to go online within the next few weeks.

Mid-challenge Workshop January 2014

Meeting Information

The meeting was held at the University of Edinburgh's Institute for Astronomy, on Monday 6 & Tuesday 7 January, 2014.

Simulations available!

We are pleased to announce that half of the challenge dataset is now available on the GREAT3 Leaderboard site, which means that this is the start of the ~6 month challenge. The remainder of the simulated data will become available in approximately one month.

First announcement: GREAT3 Mid-challenge Meeting in Edinburgh, 6 & 7 January 2014

This is the first announcement for a GREAT3 meeting being held at The Royal Observatory Edinburgh, UK. Dates have just been confirmed. For more details, see the Workshop web page.

Location: Institute for Astronomy, University of Edinburgh, The Royal Observatory Edinburgh
Dates: Monday 6 & Tuesday 7 January 2014.

Registration now open for the GREAT3 Kickoff Meeting

The GREAT3 Kickoff Meeting will bring together international experts in the field of weak gravitational lensing measurement, for presentation and discussion of their research. It will also feature interactive sessions describing the GREAT3 data and how to participate in the GREAT3 Challenge!

First announcement: GREAT3 Kickoff Meeting in Pasadena, 20-22 August 2013

This is the first announcement for the GREAT3 Challenge Kickoff meeting being held in Pasadena CA, USA. Dates have just been confirmed, more details to follow shortly!

Dates: Tuesday 20 - Thursday 22 August 2013.

Registration open for the GREAT3 Working Meeting at CMU

You can now register for the October 2012 GREAT3 Working Meeting at Carnegie Mellon University.

For information on the meeting, and registration details, please see the new page Working Meeting Oct12.

First Announcement: GREAT3 Working Meeting at CMU, October 2012

Picture attribution: Ziplux

We are planning a GREAT3 Working Meeting this October at Carnegie Mellon University. The ~3 day meeting will be a combination of working discussions to define and finalize the GREAT3 Challenge, interspersed with workshop-style research talks.

We will post more details soon, with instructions for registration and information about local accommodation.

Dates: Wednesday 17 - Friday 19 October 2012
(Official meeting close midday Friday, with time for optional working groups in the afternoon)


Welcome to the inaugural webpage for the GREAT3 challenge! More information will be forthcoming as we get closer to the time of the challenge.


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