Horus is a truck mounted, digital polarimetric phased array radar designed and operated by the University of Oklahoma's Advanced Radar Research Center in collaboration with the National Severe Storms Laboratory. Unlike other mobile phased array research radars including the Rapid-Scan DOW, MWR-05XP, and Atmospheric Imaging Radar (AIR), Horus is the first to utilize a fully digital phased array architecture and one of the first to have dual polarization. This makes Horus the most advanced research radar in the world. The radar is named after the Egyptian god of the sky Horus, whose eye is featured on the side of the vehicle.
History and deployment The Advanced Radar Research Center began work on developing phased array radars for weather research in the mid-2000s, with a detailed plan for the Atmospheric Imaging Radar (AIR) presented at the 33rd Conference on Radar Meteorology in 2007. By 2011, the AIR was completed and had its first operational test on August 8. AIR utilized a single polarization, fixed imaging subarray beamformer architecture, which offered low costs at the expense of having a fixed “fan” transmitting beam.
Shortly after completion of the AIR mobile radar, the Advanced Radar Research Center began work on developing new and more advanced phased array systems. These efforts culminated in the Cylindrical Polarimetric Phased Array Radar (CPPAR) and Horus, with other projects like the Parabolic Atmospheric Imaging Radar (PAIR) and Ka-band Mobile Rapid-Scanning Volumetric Imaging Radar (KaRVIR) still in development. Work on Horus began in the early 2010s with funding from NOAA, the Office of Naval Research, and the Army Research Laboratory. By 2018, the Advanced Radar Research Center had won over $15.2 million in government grants specifically related to the Horus project, with $6.4 million coming from NOAA and $8.8 million coming from the ONR and ARL. The first prototype was tested in 2019 and after several more years of development, Horus was completed in fall 2022. By December 2022, Horus became the first ever fully digital phased array radar to collect meteorological data. Because Horus is software limited rather than hardware limited, it has received continuous updates and development since its initial launch including the recalibration of existing scan modes and addition of new scan modes in early 2025. Horus has scanned a variety of meteorological phenomenon including lightning streaks, which were previously unobservable using traditional parabolic radars. During a severe weather event on May 11, 2023, Horus was able to conduct 582 radar scans containing lightning echoes over the period of 1 hour. These scans included rare lightning observations of positive channels propagating through negatively charged layers, which are notoriously difficult for lightning mapping arrays to detect. On April 27, 2024, Horus scanned its first tornadic circulation, a short lived QLCS tornado, during the tornado outbreak of April 25–28, 2024. On June 3, 2025, Horus scanned an EF-1 tornado moving southeast from Newcastle, Oklahoma to Norman, Oklahoma. Starting in 2026, Horus will take part in a 3-year research project called Phased Array Polarimetry for Electrification and Lightning (PAPEL), which aims to study lightning by combining the rapid scanning technology of Horus and RaXPol with the Oklahoma Lightning Mapping Array, electric field-change sensors and video observations.
Specifications Horus utilizes a planar two-dimensional (2D) fully digital polarimetric phased array radar (PPPAR) made of 25 panels consisting of 1600 individual elements. Each element is digitized and combined to form either one or multiple beams which are steered by software, allowing for Horus to quickly change its scanning mode without the requirement of physically altering the radar architecture. This also means that Horus doesn't use hardware based phase shifters and attenuators, meaning Horus is software defined and can be reconfigured and upgraded with changes to software. Horus's software is made of four primary layers, consisting of deterministic radar signal processing and control done in field programmable gate arrays (FPGAs), embedded software controlling the sub-panel architecture, back-end data processing on servers, and the operator interface running on computers. In early 2025, Horus was recalibrated after offsets between copolar H/V beams were found, resulting in new offsets of <0.1°, which is 1/30th of the beamwidth. Following the successful recalibration, new improvements are being tested, including mitigating clutter from wind turbines, improving clutter filtering, and new advanced waveform concepts.
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