CSU-CHILL S- and X-band



CHILL S-band
Deployment Type Ground-based
Frequency 2.725 GHz (S-band)
Operating Modes ATSR, STSR, LDR
Range Resolution 30-150m
Typical Range 120-300 km
Antenna 8.5m (1 °)
Transmitter Dual Klystron (1 MW)
Receiver CSU CDP
Pdf_icon.gif CSU-CHILL Data Sheet Info_circle.png
CHILL S-band Solid-State
Frequency 2.725 GHz (S-band)
Operating Modes ATSR, STSR, LDR
Range Resolution 15-150m
Typical Range 50-300 km
Transmitter Dual Solid-State (24 kW)
Receiver CSU DXR
CHILL X-band
Frequency 9.41 GHz (X-band)
Operating Modes STSR
Range Resolution 15-90m
Typical Range 75-90 km
Antenna 8.5m (0.3 °)
Transmitter Magnetron (25 kW)
Receiver CSU/CASA Signal Processor

CSU-CHILL S- and X-band is a dual-wavelength S- and X-band, dual polarization scanning radar system located at the CSU-CHILL main site. The S-band transmitter can be selected between dual 1 MW Klystron transmitters or solid-state 24 kW transmitters. The X-band transmitter is a 25 kW magnetron. The antenna is an 8.5m dual-offset (1° at S-band, 0.3° at X-band).

The radar in its current form is designed to provide very high purity polarimetric data thanks to its unique offset-feed antenna design. The dual-wavelength capability with S- and X-band simultaneous operation is unique in the research radar community. The radar offers high spatial resolution at X-band thanks to the combination of short wavelength and large aperture antenna.

The radar site is located at the CSU-CHILL main site in Greeley, CO.

Technical Overview



CSU-CHILL has a unique dual-offset, dual-polarization, dual-frequency antenna system. The offset-fed Gregorian antenna offers very good sidelobe performance in excess of -35 dB since the antenna feed structure is entirely out of the path of the main beam. This presents the smallest obstruction to the main beam, and reduces the chance of diffraction along the antenna structure. This, combined with a symmetric ortho-mode transducer (OMT) provides exceptional cross-pol isolation in excess of 50 dB (at boresight). Integrated over the width of the main beam, the integrated cross-pol ratio (ICPR) is about -37 dB, which is verified through linear depolarization (LDR) measurements in light rain.

CHILL Antenna

The antenna is housed within an inflatable radome, for protection against wind loading and corrosion. The radome is 20 m (65 ft) tall, and 35 m (115 ft) in diameter. It is constructed from low-loss microwave-transparent materials, and is has a water-repellent (hydrophobic) coating. An inflated structure is chosen to minimize construction costs for such a large structure.

CHILL Radome and Airlock

Transmitter and Receiver

The radar hardware is housed within the radar trailer, which contains the transmitters, receivers and control subsystems. The digitized signals from the receiver are passed through fiber-optic cables to the operations shelter, which contains the signal processors and storage archives.

The S-band transmitters are controlled by a flexible digital waveform generator, which can synthesize a variety of polarization states. The low-noise receivers are connected to a customized signal processing system, which can output various polarimetric moments. Moment data, as well as raw time series data can be archived for later study.

CHILL Radome and transmitter shelters

Further reading

Technical details of the CHILL radar are described in the Pdf_icon.gif CSU-CHILL Technical Brochure Info_circle.png. A more detailed description of the hardware and software architecture of CHILL is given in the hardware description.


Main article: CSU-CHILL Projects and Deployments

CSU-CHILL has a long history of field deployments and projects in support of the scientific community.

Requesting Use of the Facility

Projects conducted at the facility can be classified into

Major Projects

These projects usually involve moving the radar, larger time scales of observation (typically in excess of 20 hours) and requires the involvement and funding from the National Science Foundation (NSF). Please contact the Scientific Director for details on requesting the use of the facility.


These are larger projects that do not involve funding from the National Science Foundation. A daily use fee will be charged during the data collection process. Please contact the Scientific Director for details on requesting the use of the facility.

20-hour Projects

20 hour projects were conceived as a method to provide simplified access to the radar for users with specific data collection requirements that can be supported with modest facility effort, typically, no more than ~20 hours of radar operational time. 20 hour project investigators (and often their students) also gain valuable experience in the overall planning and conduct of meteorological field research activities.

20 hour projects have secondary priority to the support of NSF-allocated research projects. Their support is also contingent upon scheduled radar maintenance/upgrade activities and facility staff availability. 20 hour project expenses are currently provided by the facility’s NSF base funding.

To request a 20-hour project, please Fill out the Small project application form.