NASA Orbital Debris Observatory, Astronomical observatory in Lincoln National Forest, United States.

NASA Orbital Debris Observatory occupies a site in the Lincoln National Forest near Cloudcroft, New Mexico, about 23 km northeast of Alamogordo. Completed in 1962 as the Cloudcroft Electro-Optical Research Facility, it consists of a main dome that housed a 3 m liquid-mirror telescope and a smaller portable 32 cm CCD debris telescope. The facility is now privately owned by Embry-Riddle University.

Completed in 1962 as the Cloudcroft Electro-Optical Research Facility, the site was also known as the Cloudcroft Observatory. NASA funded and operated two debris telescopes there from 1995 to 2002. The 3 m liquid-mirror telescope, finished in 1994 at Johnson Space Center and moved to Cloudcroft the next year, ran until June 2002; the 32 cm CCD Debris Telescope operated from October 1997 to December 2001. Embry-Riddle University now owns the facility.

The site's name shifted with its use: completed in 1962 as the Cloudcroft Electro-Optical Research Facility, later the Cloudcroft Observatory, then NODO. The 3 m liquid-mirror telescope also served the UBC-NASA Multi-Narrowband survey of galaxies at moderate redshifts, and after retirement some of its parts went into the 6 m Large Zenith Telescope in British Columbia.

The observatory stands in the Lincoln National Forest about 23 km (14 mi) northeast of Alamogordo, reached by road from Cloudcroft. It is privately owned by Embry-Riddle University and is not open to the public, so the domes are seen from outside or from the surrounding forest roads.

The liquid mercury telescope was an engineering marvel because the spinning metal surface naturally formed a perfect parabolic mirror. This unusual approach allowed engineers to build a massive instrument far more cheaply than traditional glass-mirror designs would permit.