There are three main current ground-based surveys which have microlensing as a significant or primary component of their science program, outlined here. The science produced by all of these surveys is too extensive and varied to reasonably report here; instead we recommend interested readers refer to the publications listed on the survey websites.


Principle InvestigatorAndrzej Udalski, University of Warsaw, Poland
Websites OGLE Website
OGLE Early Warning System OGLE Photometry Database OGLE Extinction calculator OGLE Collection of Variable Stars
Telescope aperture1.3m Warsaw Telescope
SiteLas Campanas Observatory, Chile
Field of view1.4 square degrees (OGLE-IV camera)
Pixel scale0.26 arcsec/pixel
PassbandsV, I

OGLE is one of the most established surveys in microlensing, having been in continuous operation since 1992. During this time the total area footprint of the survey has dramatically increased thanks to upgrades to its primary imaging camera, now on its 3rd version. The OGLE survey is outstanding in particular for the quality of its photometry and for its long baseline of observations. This has enabled the group to compile deep reference images and catalogs of known variable stars which are used to exclude false-positive detections. As a result, OGLE issue a very reliable stream of public alerts of microlensing events in progress, which are available via their website or by subscribing to the OGLE mailing list.


Principle InvestigatorTakahiro Sumi, Nagoya University, Japan
Website MOA Website
MOA alerts
Telescope aperture1.8m
SiteMt. John Observatory, New Zealand
Field of view2.2 square degrees (MOA-II)
Pixel scale0.58 arcsec/pixel
PassbandsWide-band red, Bessell-V, -I

The MOA project represents a long-standing multi-national collaboration between Japan, New Zealand and the USA, beginning in 1995 with the 0.6m Boller & Chivens Telescope, and progressing to the purpose-built 1.8m telescope in 2003, which greatly increased the survey footprint, photometric depth and resolution. MOA operates a particularly rapid-response public alert system for microlensing events and cataclysmic variable stars, available via their website and their mailing list. They have also pioneered the introduction of alerts sent to a cell phone app, available for the Android platform.


Operated byKorea Astronomy and Space Science Institute, South Korea
Director of microlensing programAndy Gould, Max Planck Institute Heidelberg, Germany
Website KMTNet Website
Telescope apertureThree 1.6m telescopes
SitesSiding Spring, Australia,
Cerro Tololo Inter-American Observatory, Chile,
South African Astronomical Observatory, South Africa
Field of view2 x 2 degrees
Pixel scale0.40 arcsec/pixel
PassbandsV, R, I

KMTNet is the newest ground-based survey in microlensing and promises to be ground-breaking thanks to its combination of three wide-field telescopes at longitudinally-separated sites around the southern hemisphere. This means it can monitor microlensing survey fields 24/7 for a large part of the season, dramatically improving the photometric coverage of events and hence the probability of discovering planets. KMTNet began operations in 2013-2014, and does not issue alerts at the current time.

Large Synoptic Survey Telescope (LSST)

Operated byLSST Corporation
Lead of microlensing subgroup of science collaboration:Rosanne Di Stefano (CfA Harvard) and Rachel Street (Las Cumbres Observatory)
Websites: LSST Website LSST Microlensing Groups Website
Telescope aperture8.4m telescope, effective collecting area 6.67m
SitesCerro Tololo Inter-American Observatory, Chile
Field of view3.5 degrees in diameter
Pixel scale0.20 arcsec/pixel
Passbandsu, g, r, i, z, y

LSST is currently under construction in Chile, and is due to begin full survey operations in 2023. It will conduct a very large, multi-filter imaging survey of all regions of the sky accessible from its site. Though the original survey design generally avoided imaging in the Galactic Plane due to concerns over the data reduction, this is in the process of review. LSST is designed to maximize time domain science by rapidly issuing alerts on all targets that change brightness or move within its field of view, at a rate expected to be of the order of tens of millions per night, at least at the start of the project.