ALTAIR (ARPA Long-Range Tracking And Instrumentation Radar) is a radar tracking station on Roi-Namur island in the north part of the Kwajalein atoll in the Marshall Islands.

It is a high-sensitivity, wide-bandwidth, coherent, instrumentation and tracking radar that is capable of collecting precise measurements on small targets at long-ranges.

ALTAIR supports several operating modes, including tracking and signature collection at VHF and UHF.

It is part of a network of contributing radar sensors that perform deep-space tracking.

[4] The original task was to detect and track intercontinental ballistic missiles.