Radar Applied to Missions Large and Small—Part 2
Radars have a place amongst the stars and inside the home, with cutting-edge research highlighting uses that benefit from this century-old technology.
Check out Part 1 of this series.
Whether it is in space or in the home, radar technology has become a prevalent piece of sensing hardware for any environment as exhibited by researchers at the 2023 IEEE Radar Conference (RadarConf 2023). In day-to-day life, radar can be seen in applications ranging from vehicle sensing to biomedical monitoring, with new uses being found at an accelerating rate.
Radar can be found sporting massive antennas (left) or hidden inside a cell-phone. Despite the size disparity, both use the same fundamental physics to accomplish sensing. Images used courtesy of LiveScience (left) and Google (right)
This is not to say that radar is the be-all and end-all for every sensing application, but rather that radar sports fundamental characteristics that make it advantageous for a wide variety of sensors, especially those that require operation in low-light, occluded, or private environments.
Part 1 of this series highlighted two sensing applications, one large and one small, that leveraged radar in order to accomplish high-performance sensing. Here in part 2, we will look at two more applications presented at RadarConf 2023 that further highlight radar’s versatility and flexibility to give readers a sense of the state of the art of radar sensing, as well as provide insight into where the next generation of radars may be found.
NASA-ISRO SAR Mission
Extending NASA’s beneficial relationship with radar-enabled satellites, Dr. Paul A. Rosen gave a talk about an upcoming NASA JPL mission in partnership with the Indian Space Research Organization (ISRO). This mission, the NASA-ISRO Synthetic Aperture Radar (NISAR) mission, is expected to launch in 2024 and will provide scientists of all disciplines access to new sources of global information.
Synthetic aperture radar uses the motion of the radar to synthetically create a large antenna aperture to form fine-resolution images, while only requiring a single radar. Image used courtesy of NASA JPL
Synthetic aperture radar (SAR) has seen a considerable amount of use in satellite imaging of the Earth due to its ability to produce a high-resolution image with a relatively low-resolution radar. The NISAR mission, however, is the first of its kind to leverage two bands in order to provide more information (35 Tb/day for NASA).
The NISAR mission will ultimately be used to map and track the Earth’s dynamics with a new level of precision, allowing scientists to measure the motion of the Earth’s mass. Image from All About Circuits’ attendance of RadarConf 2023. (Click image to enlarge)
The craft uses an extendable reflector in order to focus the beam to a sufficiently small point, similar to that of the composite booms used in the DART mission. Using advanced signal processing, Dr. Rosen claimed that the final resolution would be much smaller than a wavelength.
“We’re talking about millimeters to centimeters kind of precision. Measurements that are really quite astounding.”
This level of precision creates accurate data that is readily available and rapidly updated thanks to the orbit of the payload. When discussing the measurement and orbit cycles of the NISAR mission, Dr. Rosen said, “We repeat [ascending and descending measurements] every 12 days for the life of the mission, which leads to around 1.6 petabytes of raw data per year,” helping to quantify the depth and breadth of climate and biomass information that will be available to scientists in the coming years thanks to advances in radar sensing technology.
Outside of planetary sensing, radar can also be used to enable new levels of accessibility in the home. Dr. Sevgi Gurbuz presented her work at RadarConf 2023, which highlights how radar can detect minuscule motions in order to perform smart sensing.
Using different techniques, radar can be used to detect motions down to a micrometer scale, which can be used for vital sign detection, gesture recognition, and a bevy of other applications. When paired with AI/ML, radar can also be a powerful tool for non-invasive in-home monitoring without compromising privacy.
Addressing the privacy aspect of radar, Dr. Gurbuz points out that radar data is difficult to interpret by the layman.
“Radar is perhaps one of the least understood sensors. If you use radar data or look at radar data, I think, outside of this room, there are very few people who would understand and interpret it.”
Dr. Sevgi Gurbuz reported how radar may be used to perform sign-language translation, with fluent signing showing a marked difference from copy signing. Image from All About Circuits’ attendance of RadarConf 2023.
The improved privacy afforded by radar sensing puts it in a unique position to enable new applications that were previously disregarded due to privacy concerns, including activity monitoring to autonomously scan for falls or injuries while at home. In addition, Dr. Gurbuz has reported improved word-level recognition of American Sign Language using radar, opening the doors for autonomous translation without requiring image processing.
Radar spectrograms illustrate the signatures of various activities such as walking, crawling, and falling that can be used to identify motions. Image used courtesy of IEEE Transactions on Aerospace and Electronics Systems. (Click image to enlarge)
Dr. Gurbuz feels that radar has only begun playing a role in the home. “Radar is uniquely situated in IoT because it is the only sensor that allows you to actively interrogate the environment,” she says. And with IoT technology growing in tandem, radar is in a prime position to become a common household appliance.
Sensing at Any Size
Although polling the attendees of RadarConf may lead to a biased result about the role that radar will play in the future, the innovations reported by industry and academia certainly make the future for the technology seem bright. As more applications are enabled thanks to the versatility of radar, the developments made to one sensor can ultimately benefit all radar designers.
So, while radar itself may never reach the size and resolution levels of top-of-the-line image or optics-based sensors, its unique benefits ensure that it will always have applications, both large and small, where it is the best solution.