ALTAIR (Radar)

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.^[2]

ARPA Long-Range Tracking And Instrumentation Radar (ALTAIR)^[1]

Cassegrain antenna of ALTAIR
Country of origin	US
Designer	MIT Lincoln Laboratory
Introduced	1969
Frequency	162 and 422 mc
PRF	300 pps
Beamwidth	1.1° (UHF) 2.8° (VHF)
Pulsewidth	80 µsec
Range	42,000 km
Diameter	45.7 m (150 ft)
Precision	20 m (66 ft)
Power	5 MW

The antenna uses a steerable 150-ft dish (46-m-diameter) and employs a focal point VHF feed and multimode Cassegrain UHF feed in conjunction with a frequency selective sub-reflector (5.5 m diameter).^[3]

The radar became operational in 1969.^[4] The original task was to detect and track intercontinental ballistic missiles. It is currently used to measure satellite orbits and meteor echoes in low-Earth orbit,^[5] and to observe ionospheric irregularities and background densities.^[6]