Observations for the Two Micron All-Sky Survey (2MASS) was begun in 1997 and completed in 2001 at two telescopes located one each in the northern and southern hemispheres (Mt. Hopkins Arizona and Cerro Tololo/CTIO Chile, respectively) to ensure coverage of the entire sky. The most ambitious project to map the night sky to date, the final (post-processing) data release for 2MASS occurred in 2003. The whole sky was covered in three infrared wavebands around 2 (microns), J (), H (), and Ks ().
The goals of this survey included:
- Detection of galaxies in the "zone of avoidance," a strip of sky obscured in visible light by our own Galaxy, the Milky Way.
- First detection of brown dwarfs.
- An extensive survey of low mass stars, the most common type of star both in our own galaxy and others.
- Cataloging of all detected stars and galaxies.
The resulting data from the survey is currently in the public domain, and may be accessed online for free by anyone at  (although interpretation and use of this data may require an advanced degree). There is also a list of 2MASS science publications with links to free pre-publication copies of the papers.