CSU-CHILL
{{Short description|US weather surveillance radar}}
{{Infobox radar
| name = CSU-CHILL
| image = CSU-CHILL.jpg
| caption = CSU-CHILL antenna and feed horn
| country = United States
| manufacturer =
| introdate =
| number = 1
| type = Weather radar
| frequency = 2735 MHz (S-band)
9415 MHz (X-band)
| PRF =
| beamwidth = 1.1°
| RPM = 0-33 deg s−1
| range =
| altitude =
| diameter = 8.5 m
| azimuth =
| elevation = 0°-90°
| precision =
| power = 800 kW - 25 kW (S and X-band)
| other names =
}}
Colorado State University - CHicago ILLinois radar, colloquially CSU-CHILL, is a semi-mobile, dual-frequency weather surveillance radar developed in 1970 by the University of Chicago{{cite book|author=Huanyao Dai, Xuesong Wang, Hong Xie, Shunping Xiao, Jia Luo|title=Spatial Polarization Characteristics of Radar Antenna: Analysis, Measurement and Anti-jamming Application|url=https://books.google.com/books?id=iSVhDwAAQBAJ&pg=PA17|date=20 June 2018|publisher=Springer|isbn=978-981-10-8794-3|pages=17–}} and the Illinois State Water Survey,{{cite book|author=National Science Foundation (U.S.)|title=Weather Modification: Annual Report|url=https://books.google.com/books?id=KgcIAAAAIAAJ&pg=RA4-PA52|year=1966|publisher=National Science Foundation|pages=4–}} which has since been moved to Colorado on behalf of Colorado State University.{{cite web|url=http://www.radartutorial.eu/19.kartei/10.weather/karte016.en.html|title=Radar Basics - CSU CHILL|first=Dipl.-Ing. (FH) Christian|last=Wolff|website=www.radartutorial.eu}} The radar was operated through a cooperative agreement with the National Science Foundation.{{cite book|author1=V. N. Bringi|author2=V. Chandrasekar|title=Polarimetric Doppler Weather Radar: Principles and Applications|url=https://books.google.com/books?id=4r7e6assEHwC&pg=PR14|date=30 August 2001|publisher=Cambridge University Press|isbn=978-1-139-42946-7|pages=14–}}
== Description ==
CSU-CHILL is used to study atmospheric principles and precipitation on a small scale with the use of two frequencies. It has a transmitter consisting of both S and X-bands, both using a klystron. Each transmitter can individually transmit its respective frequency through its own feed horn onto the 9m offset parabolic antenna. This configuration also aids in the ability to gather samples from various polarizations. From these, the type of precipitation can be easily discerned.{{cite web|url=http://www.chill.colostate.edu/w/Facilities|title=Facilities - CHILL|website=www.chill.colostate.edu}}
CSU-CHILL is protected by a pneumatic dome, and is close to its control buildings.{{cite journal|title=American Meteorological Society |journal=Journal of Atmospheric and Oceanic Technology |volume=17 |pages=1596 |publisher=Journals.ametsoc.org |doi=10.1175/1520-0426(2000)017<1596:ADOTCC>2.0.CO;2 |issn=1520-0426 |year=2000 |hdl=10217/68087 |hdl-access=free }} It is often positioned near Greeley, Colorado, but is semi-mobile, so that it is movable in separate pieces, and can be quickly assembled or disassembled to participate in a field study.{{cite web|url=http://www.chill.colostate.edu/w/Hardware_description|title=Hardware description - CHILL|website=www.chill.colostate.edu}}