ALTAIR (Advanced Research Project Agency (ARPA) Long Range Tracking and Identification Radar)

From fas.org:

ALTAIR (Advanced Research Project Agency (ARPA) Long Range Tracking and Identification Radar) is a high-resolution radar located at Kwajalein Atoll in the western Pacific that provides precision metric, signature, and imaging for deep-space operations, satellite observations, strategic reentry missions, and multiple-intercept engagement tracking. ALTAIR is a near earth and deep space tracking radar. As one of the three radars composing the Space Surveillance Network, ALTAIR can track one third of the objects in the geosynchronous belt, more than 42,000 tracks per year. The other two radars are the ALCOR (ARPA Lincoln Band Observable Radar) and the TRADEX (Target Resolution and Discrimination Experiment). ALTAIR is unique because it is the only radar in the Space Surveillance Network with an equatorial location.