ALTAIR is a combination VHF-UHF high power radar. The acronym stands for ARPA (Advanced Research Project Agency) Long Range Tracking and Identification Radar).
Located at Kwajalein Atoll in the western Pacific, ALTAIR is a near earth and deep space tracking radar. It has two missions, Anti-Ballistic Missile (ABM) testing and space surveillance. 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, plus keep tabs on "foreign launches". The other two radars are the ALCOR and the TRADEX.