Lunar and Planetary Laboratory
The University of Arizona
Tucson, AZ
[Spacewatch Telescopes on Kitt Peak]
The Spacewatch 1.8-meter and 0.9-meter telescopes
on Kitt Peak, 45 miles southwest of Tucson, Arizona.

Note: Spacewatch is looking for a new observer and programmer. Please see

SPACEWATCH® is the name of a group at the University of Arizona's Lunar and Planetary Laboratory founded by Prof. Tom Gehrels and Dr. Robert S. McMillan in 1980.  Today, Spacewatch is led by Dr. Robert S. McMillan.  The original goal of Spacewatch was to explore the various populations of small objects in the solar system, and study the statistics of asteroids and comets in order to investigate the dynamical evolution of the solar system.  CCD scanning studies the Centaur, Trojan, Main-Belt, Trans-Neptunian, and Earth-approaching asteroid populations.  Spacewatch also found potential targets for interplanetary spacecraft missions. Spacewatch currently focuses primarily on followup astrometry of such targets, and especially follows up objects that might present a hazard to the Earth.

CCD observations are conducted 24 nights each lunation with the Steward Observatory 0.9-meter Spacewatch telescope and the Spacewatch 1.8-m telescope, both on Kitt Peak. Emphasis today is on recovering faint solar system objects, especially Near Earth Asteroids which have been found to pose an impact hazard, such as the Virtual Impactors (VI's) and Potentially Hazardous Asteroids (PHA's). Other objects of interest include future Radar targets, possible targets of human exploration and objects discovered by the WISE and NeoWISE surveys which have valuable infrared estimates of their size. The 1.8-meter telescope allows us to observe objects more than 0.7 magnitudes fainter than the 0.9-meter telescope. To complement the deep penetration of the 1.8-m, we have put a mosaic of CCDs on the 0.9-m telescope. This permits us to cover sky at least six times faster than the pre-2002 system when in survey mode.

Spacewatch also uses other large telescopes such as the 4-meter Mayall telescope on Kitt Peak and the Steward Observatory 90 inch Bok Telescope on Kitt Peak to do systematic followup of Near Earth Asteroids such as virtual impactors, potentially hazardous asteroids, radar targets, possible spacecraft targets and objects discovered by the WISE and NeoWISE surveys.

Some of Spacewatch's distinctions:

  • First to use CCD-scanning routinely in astronomy
  • First to use CCDs to survey the sky for comets and asteroids
  • First near-Earth asteroid discovered with a CCD (1989 UP)
  • First astronomical group to develop automated, real-time software for moving-object detection
  • First to discover a near-Earth asteroid by software (1990 SS). See images and information page for 20th anniversary of this discovery
  • First to use a CCD to discover a comet, which was also the faintest comet at the time of discovery. (125P/1991 R2)
  • First automatic discovery of a comet (C/1992 J1)
  • Discovered the C or S type asteroid with closest approach to the Sun at time of discovery (1995 CR at 0.120 AU)
  • Identified two new asteroid populations - small NEAs and distant Centaurs
  • Discovered fastest rotating and most accessible asteroid at time of discovery (1998 KY26)

(This page updated 2017 February 03; See dates of update on individual pages to note currency of information posted)