When the Arecibo Observatory dish in Puerto Rico collapsed in 2020, astronomers lost a powerful radio telescope and a unique radar instrument to map the surfaces of asteroids and other planetary bodies. Fortunately, a new, next-generation radar system called ngRADAR is under development, to eventually be installed at the 100-meter (328 ft.) Green Bank Telescope (GBT) in West Virginia. It will be able to track and map asteroids, with the ability to observe 85% of the celestial sphere. It will also be able to study comets, moons and planets in our Solar System.<\/p>\n
\u201cRight now, there is only one facility that can conduct planetary radar, the 70-meter (230-foot) Goldstone antenna that is part of NASA\u2019s Deep Space network,\u201d said Patrick Taylor, the project director for ngRADAR and the radar division head for the National Radio Astronomy Observatory. \u201cWe had begun this process of developing a next generation radar system several years ago, but with the loss of Arecibo, this becomes even more important.\u201d<\/p>\n
<\/p>\n Planetary radar can reveal incredibly detailed information about the surfaces and makeup of asteroids, comets, planets, and moons. The ngRADAR system could provide unprecedented data on these objects. In fact, a recent test with a low-power prototype of ngRADAR at the GBT produced some of the highest resolution planetary radar images ever captured from Earth. But the hallmark of the new system will be seeking out near Earth asteroids and comets to evaluate any hazard they might present to our planet.\u00a0<\/p>\n \u201cRadar is really powerful in determining the orbits of these asteroids and comets,\u201d Taylor told Universe Today in an interview, \u201cand the new system will deliver very precise data that will allow us to predict where these small bodies will be in the future. That will be one of the highest priority uses for the next generation radar system, where we can track and characterize near-Earth asteroids and comets to evaluate any hazard they might present to Earth in the future.\u201d<\/p>\n Usually, radio telescopes collect weak light in the form of radio waves from distant stars, galaxies, and other energetic astronomical objects \u2013 including black holes or cold, dark objects that emit no visible light. While radio telescopes don\u2019t take pictures in the same way visible-light telescopes do, the radio signals detected are amplified and converted into data that can be analyzed and used to create images.\u00a0<\/p>\n But radio telescopes can also be used to transmit and reflect radio light off planetary bodies in our Solar System. This is called planetary radar or Solar System radar.<\/p>\n What is planetary radar and how does it work?<\/p>\n \u201cEssentially we have a flashlight that works in radio waves,\u201d Taylor explained. \u201cOur narrow flashlight beam does not look at the whole sky, but we point it in a very precise location \u2013 the surface of an asteroid or moon. We know very well what our flashlight\u2019s properties are, so we know exactly what we send out. When we receive the echo back from wherever we pointed our flashlight, we analyze that signal and see how it changed compared to what we transmitted.\u201d<\/p>\n That\u2019s what makes planetary radar so powerful and different from any other type of astronomy. \u00a0<\/p>\n \u201cWhen astronomers are studying light that is being made by a star, or galaxy, they\u2019re trying to figure out its properties,\u201d Taylor said. \u201cBut with radar, we already know what the properties of the signals are, and we leverage that to figure out the properties of whatever we bounced the signals off of. That allows us to characterize planetary bodies \u2013 like their shape, speed, and trajectory. That\u2019s especially important for hazardous objects that might stray too close to Earth.\u201d<\/p>\n In the past, planetary radar has been used to image asteroids, but also precisely measure the position and motion of the planets, allowing us to land spacecraft on Mars and to explore the outer Solar System. The technique has also made surprising discoveries, such as the finding the presence of water ice on Mercury. \u00a0<\/p>\n Because radio waves are much longer than visible light waves, radio astronomy requires large antennas. The 70-meter Goldstone antenna located in California\u2019s Mojave Desert, is primarily used to communicate with spacecraft as part of NASA\u2019s Deep Space network. But it is also frequently used for planetary radar to study near Earth asteroids, and \u2014 as previously mentioned \u2014 is the only facility currently available to perform planetary radar. Previously, the workhorse for planetary radar was the 1,000-foot-diameter (305 meters) Arecibo Observatory, which was about 20 times more sensitive and could detect asteroids about twice as far away than Goldstone.<\/p>\n However, because Arecibo\u2019s dish was stationary and built inside a round sinkhole, it was fixed to the Earth and could only view whatever part of the sky happened to be straight overhead. That meant Arecibo\u2019s dish could only see about one-third of the sky. Goldstone is fully steerable, can see about 80 percent of the sky, can track objects several times longer per day, and can image asteroids at finer spatial resolution.<\/p>\n The Robert C. Byrd Green Bank Telescope is the world\u2019s largest fully steerable radio telescope. The maneuverability of its large 100-meter dish allows it to quickly track objects across its field of view, and see 85% of the sky.<\/p>\n The GBT\u2019s new radar system will introduce a high-resolution tool that will be a vast upgrade, collecting data at higher resolutions and at wavelengths not previously available. Scientists at GBT and the National Radio Astronomy Observatory (NRAO) are also developing advanced data reduction and analysis tools that have not been available before, providing astronomers with unprecedented planetary radar capabilities.<\/p>\n To test out the proof of concept, Taylor and his team worked with the company Raytheon \u2014 a long-time developer of radar systems for both the military and science applications, and specifically the Raytheon Intelligence & Space (RIS)division \u2014 to build a small version of the transmitter, with a lot less power.<\/p>\n \u201cOur friends at Raytheon built a transmitter that could output 700 watts, so about half the power of a microwave oven,\u201d Taylor said. \u201cUltimately, we want to build a system with 500 kilowatts, so up by a factor of a thousand. But even with 700 watts, we were able to do some really impressive observations.\u201d<\/p>\n GBT\u2019s planetary radar was aimed at the Moon, specifically at the Apollo 15 landing site in Hadley Rille, and at the giant Tycho Crater. \u2019s surface, and radar echoes were received with NRAO\u2019s ten 25-meter VLBA antennas. At Tycho, the crater was captured with 5-meter resolution, showing unprecedented detail of the Moon\u2019s surface from Earth. Taylor said the resolution with the ngRADAR prototype approached the optical resolution on Lunar Reconnaissance Orbiter, taking images with its high-resolution cameras from orbit around the Moon.<\/p>\n \u201cThe images of the crater floor were actually breathtaking,\u201d Taylor said. \u201cIt\u2019s pretty amazing what we\u2019ve been able to capture so far, using less power than a common household appliance.\u201d<\/p>\n Additionally, the prototype radar also detected a potentially hazardous asteroid named (231937) 2001 FO32, which happened to be flying past Earth at about six times more distant than the Moon during their radar pings. The asteroid is considered potentially hazardous because of its size, approximately 1 kilometer in diameter, along with how close it can get to Earth, at just over 2 million kilometers away. The asteroid\u2019s detection appeared as a spike in their data.<\/p>\n \u201cJust from the spike in our data, we can now figure out how fast this object is moving, determine its orbit, and figure out its trajectory in the future,\u201d Taylor explained. \u201cWe can determine its impact risk and assess how much of a hazard it is, and even constrain its spin state, its size, its composition, its scattering properties, and so on. So, even though the data spike doesn\u2019t look like much, that one little detection can tell you a lot of information about the asteroid.\u201d<\/p>\n Radar signals transmitted by the GBT will reflect off astronomical objects, and those reflected signals will be received by the Very Long Baseline Array (VLBA), a network of ten observing stations located across the United States.<\/p>\n \u201cThe idea is for GBT is to do the transmitting almost constantly and the VLBA \u2014 either all ten of those or any subset of those telescopes \u2014 doing the receiving,\u201d Taylor said. \u201cThis new system will allow us to characterize the surfaces of many different objects in a different frequency or wavelength that hasn\u2019t been used before.\u201d<\/p>\n Next: Part 2 of this series will look at the details of ngRADAR, the history of planetary radar, and take you up close to the GBT. <\/strong><\/p>\nA Radar Flashlight<\/h2>\n
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ngRADAR<\/h2>\n
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Like this:<\/h3>\n