ALTAIR (Radar)

{{Short description|Radar station in Marshall Islands}}

{{Infobox radar

| name = ARPA Long-Range Tracking And Instrumentation Radar (ALTAIR)J. A. Nelson and K. R. Roth, History of Lincoln Laboratory at the Reagan Test Site, Lincoln Laboratory Journal Number 2 2012 ([https://archive.ll.mit.edu/publications/journal/pdf/vol19_no2/19_2_1_Nelson.pdf online PDF])

| image = Radar antenna.jpg

| caption = Cassegrain antenna of ALTAIR

| country = US

| designer = MIT Lincoln Laboratory

| manufacturer =

| introdate = 1969

| frequency = 162 and 422 mc

| PRF = 300 pps

| beamwidth = 1.1° (UHF)
2.8° (VHF)

| pulsewidth = 80 µsec

| range = 42,000 km

| diameter = {{convert|45.7|m|ft|abbr=on}}

| elevation =

| precision = {{convert|20|m|ft|abbr=on}}

| power = 5 MW

}}

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.[https://www.radartutorial.eu/19.kartei/01.oth/karte005.en.html Card Index of Radar Sets] in Radartutorial

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).S. Close, S. M. Hunt, F. M. McKeen and M. J. Minardi: “Characterization of Leonid meteor head echo data collected using the VHF-UHF Advanced Research Projects Agency Long-Range Tracking and Instrumentation Radar (ALTAIR)”, MIT Lincoln Laboratory, Lexington, Massachusetts, USA, in RADIO SCIENCE, VOL. 37, NO. 1, 1009, 10.1029/2000RS002602, 2002 ([https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.472.7520&rep=rep1&type=pdf online PDF])

The radar became operational in 1969.Sidney G. Reed, Richard H. Van Atta und Seymour J. Deitchman [https://books.google.com/books?id=lku2AAAAIAAJ&dq=ARPA+Long-Range+Tracking+And+Instrumentation+Radar+%22ALTAIR%22&pg=SA1-PA16 DARPA technical accomplishments : an historical review of selected DARPA projects], Institute for Defense Analyses, Alexandria, Va. und [1990-1991] 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,Sigrid Close et al.: “Simultaneous dual-frequency observations of meteor head echoes using ALTAIR”, In: Proceedings of the Third European Conference on Space Debris, 19–21 March 2001, Darmstadt, Germany. Ed.: Huguette Sawaya-Lacoste. ESA SP-473, Vol. 1, Noordwijk, Netherlands: ESA Publications Division, ISBN 92-9092-733-X, 2001, p. 237 - 242 ([https://conference.sdo.esoc.esa.int/proceedings/sdc3/paper/103/SDC3-paper103.pdf online PDF]) and to observe ionospheric irregularities and background densities.D.M.Towle: "VHF and UHF radar observations of equatorial F region ionospheric irregularities and background densities", Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, Massachusetts 02173, in Radio Science 1980, p. 71 ([https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/RS015i001p00071])