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 now available, downloadable from our server on the GREAT3 Leaderboard web site.

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

The GREAT3 Final Meeting will take place 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), this challenge will play 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.

US Mirror downtime scheduled: 30 March 2014

The US Mirror for the GREAT3 data will be down for a period of 2-3 days beginning Sunday 30 March 2014. This is while the server at the California Institute of Technology undergoes a significant disk upgrade.

Anyone planning downloads from the US Mirror should avoid those days. We will send a reminder to all participants via the email list closer to the time, and inform everyone when the data is back up. The primary download site (based in the UK) will be accessible throughout this period.

Supplementary downloads for GREAT3 deep fields released

Darren Hester

In GREAT3 we have provided a small number of deep fields: longer exposure imaging that overlaps a subset of the main dataset. This sort of deeper imaging is often a part of wide area extragalactic survey strategy. Methods will be able to train using this sort of data in real life, and we wanted to reflect this in GREAT3.

However, those who wish to use the deep fields for the variable PSF or full branches in GREAT3 will find have found that the galaxy catalog files for the deep fields in those branches are missing some important information.

Scores updated after revision of GREAT3 metrics

This morning we recalculated the Q values in all GREAT3 leaderboards following revision of the definition of the metrics, so do not be perturbed if you saw a change in your submission score!

The scaling of the metrics has been revised in light of submission data to ensure that a score of Q~1000 indicates excellent performance, with some allowance for statistical uncertainties. More than one team now appears to be exceeding bias targets in some branches: this is a fantastic achievement.

URGENT: Weekend shutdown of the GREAT3 Leaderboard Server

Due to electrical testing and maintenance in the UCL server room, our GREAT3 Leaderboard Server will very likely be shut down over the weekend 14-16 February 2014, starting at 3pm GMT Friday.

We apologise sincerely for the short notice: the shutdown is due to the discovery of a significant electrical fault in the server room by UCL Estates yesterday.

All challenge data now available!

Servers

We are pleased to announce the release of the ‘variable PSF’ and ‘full’ simulations, which are the last 8 branches of the challenge dataset, as well as updated 'multiepoch’ simulations. As usual, you can download them from the challenge data download page.

A few other notable updates:

Example script for multiepoch data now available

Dumplings-AH
In GREAT3 we have always planned to release example scripts that provide a basic, but far from complete, solution to key parts of the challenge.

GREAT3 press releases

We have been lucky enough to receive coverage about the GREAT3 Challenge, from our partners Carnegie Mellon University, NASA Jet Propulsion Laboratory, and University College London!

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: http://great3.projects.phys.ucl.ac.uk/leaderboard/data

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.

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