DARPA’s Video Synthetic Aperture Radar (ViSAR) program recently completed flight tests, successfully demonstrating a 233 GHz radar sensor that can capture real-time video through clouds.

The ViSAR program, which began in 2013, has been developing an extremely high frequency (EHF) targeting sensor that can operate through clouds as effectively as current electro-optical and infrared (EO/IR) sensors operate in clear weather. The program’s goal is to develop a cloud-penetrating EHF sensor in a moveable gimbal that can be mounted on a variety of aerial platforms and provide high resolution, full-motion video, for engaging moving ground targets in all weather conditions — cloudy or clear.

L3 Communications Electron Devices and Northrop Grumman were awarded contracts to develop the ViSAR sensor in 2013 and Raytheon is the system integrator, according to a DARPA spokesperson.

Bruce Wallace, program manager in DARPA’s Strategic Technology Office, said

The recent flight tests of the ViSAR sensor marked a major program milestone toward our goal, proving that we can take uninterrupted live video of targets on the ground even when flying through or above clouds. The EO/IR sensors on board the test aircraft went blank whenever clouds obscured the view, but the synthetic aperture radar tracked ground objects continuously throughout the flight.


Refining the ViSAR sensor’s visualization software to provide operators a representation they’re used to seeing is the next step in the program. We don’t want operators in the back of an aircraft to need special radar training to interpret the sensor’s data — we are working to make the visual interface as easy to interpret as existing EO/IR sensor displays.

Wallace noted that cloud-penetrating radar — such as from space or other operational systems — has existed in other formats, but not a synthetic aperture sensor that can fit in a standard EO/IR sensor gimbal on an aircraft and maintain frame rates fast enough to track maneuvering targets on the ground.

The recent ViSAR tests took place on a modified DC-3 aircraft that flew at low and medium altitudes, allowing researchers to collect and compare data from the ViSAR, EO and IR sensors mounted on standard sensor gimbals.

The ViSAR program has demonstrated and continues to push technology innovations in four technical areas:

  • compact flyable EHF-band exciters and receivers
  • compact flyable EHF-band medium-power amplifier
  • EHF-band scene simulation, and
  • advanced algorithms for EHF-band operation.

The primary frequency of the sensor is approximately 233 GHz.

The next phase of the ViSAR program is to integrate the sensor into an aircraft that includes a complete battle management system, capable of real-time target engagement.

More Information

Bruce Wallace published an online article at SPIE with more technical information about ViSAR.