Powerful radar systems have played a major role in the study of planets, moons, asteroids, and other objects in our Solar System for several decades, and now have a "unique role" to play in planetary defense - "providing protection to the nations of the world from devastating asteroid and comet impacts," according to the newly released Planetary Science and Astrobiology Decadal Survey 2023-2032. The National Radio Astronomy Observatory (NRAO) and the Green Bank Observatory (GBO) are developing new capabilities for the Green Bank Telescope (GBT) and the Very Long Baseline Array (VLBA) that will make them key instruments for meeting this need.
The survey's report, published by the National Academies of Sciences, Engineering, and Medicine, recounts the dangerous effects of impacts from Near Earth Objects (NEOs). These effects range from the asteroid impact 66 million years ago that wiped out the dinosaurs, to a Siberian impact in 1908 that had the explosive equivalent of 3 to 20 megatons of TNT, to a 2013 impact in Chelyabinsk, Russia, equal to 440 kilotons that injured more than 1,600 people. These are compared to the roughly 15-kiloton Hiroshima nuclear bomb.
The key to mitigating such dangers is to track the objects and measure their sizes and other characteristics to determine the probability that they will strike Earth and the effect they would have if they do. According to the survey, radar is an essential tool for this task.
"Ground-based radar observations of NEOs provide invaluable information for long-term tracking," the survey said. "Because NEO impact energy scales with density, diameter, and velocity, and radar can constrain all of these, planetary radar observations are an important post-discovery characterization technique," the survey added.
Prior to its collapse in 2020, the Arecibo telescope possessed the most powerful radar capabilities for the world's astronomical community, often working with the GBT and VLBA as receivers. The Next Generation radar system being developed for the GBT and VLBA, and later the Next Generation Very Large Array (ngVLA), will help replace the capabilities lost at Arecibo.
The survey recommended developing "a plan for ground-based planetary radar capabilities comparable to or exceeding those of the Arecibo Observatory necessary for achieving planetary defense objectives."
Since its dedication in 2000, the GBT has been a fundamental instrument for planetary science and planetary defense, observing NEOs and Potentially Hazardous Asteroids, the Moon, and the terrestrial planets as a receiver for radar projects. Now, thanks to new technology under development for the GBT, it is the largest fully steerable antenna in the world capable of transmitting radar signals for research.
The GBT's 100-meter diameter makes it an impressive tool for radar work. The location of the GBT and its maneuverability permits it to observe 85 percent of the celestial sphere, allowing it to quickly track objects across its field of view.
A recent article in the Microwave Journal reported on radar experiments done using the GBT and VLBA that successfully produced high resolution images of the Moon, and detected a Near-Earth Asteroid making a close flyby of Earth, more than 5 times farther away than the Moon - using less power than a microwave oven. In these tests, as a proof of concept, the GBT transmitted a 650-watt radar signal at 13.9 GHz that was received by VLBA antennas, producing radar images of the Moon's surface with unprecedented detail.
The National Science Foundation has awarded funds for the conceptual design of a higher-power radar system on the GBT - one that would be nearly 1,000 times more powerful than the proof of concept. In addition to a more powerful transmitter, NRAO and GBO, working with industry partners, will leverage new, solid-state amplifier and array receiving-system technologies to maximize the effectiveness of the new system. In parallel to this, as additional funding is allocated, the team plans to move to final design and construction activities, beginning in 2023.
The GBT's new radar capabilities will introduce a tool that astronomy has not had before, collecting data at higher resolutions and at wavelengths not previously available. NRAO and GBO also are developing advanced data reduction and analysis tools that have not been available before. The flexibility and increased performance of this new system will fill an important need for planetary defense, and also allow astronomers to observe asteroids, comets, planets and moons. The versatility of this system will contribute to many areas of science.
Responding to the report, U.S. Senator Joe Manchin (D-WV) said, "For many years, I have been committed to ensuring the Green Bank Observatory stays open for the next generation of young scientists in West Virginia and around the world. Through my seat on the Senate Appropriations Committee, I have strongly supported Green Bank's work observing and cataloging near-earth objects, including the development of new technology that would make it the world's largest moveable antenna and transmitter.
"The new decadal survey underscores Green Bank's importance in planetary research for many more decades to come, and I am proud of the scientists and the entire staff at Green Bank and look forward to seeing their continued efforts to advance our studies of the cosmos."
U.S. Senator Shelly Moore Capito (R-WV) said, "One of the great benefits of the research and capabilities at Green Bank is the ability to meet the challenges scientists identify at the time. Here again Green Bank stands ready to advance scientific discovery to meet a national concern."
"At NRAO and GBO, we have a long history of participation in planetary radar studies, and we look forward to adding new capabilities to the GBT and VLBA to produce a next-generation radar system that will serve as an essential tool for researchers in planetary science and planetary defense," said Patrick Taylor, radar division head for NRAO and GBO.
After the meeting of the ESA Council at Ministerial Level last weekend, ESA Director General Jan Woerner made the following statement: There was one aspect which detracted from the otherwise positive mood: AIM (short for Asteroid Impact Mission) failed to get the financial support it needed. AIM had been intended as a learning exercise that would form part of a joint NASA-ESA activity to evaluate the technical possibilities of changing the flight path of a tiny asteroid moon. It was an example of ESA at its absolute best: daring, innovative and ambitious all at once. Although, in the beginning, very promising subscriptions were given, the withdrawal of the biggest single amount at the very last minute proved devastating to an important mission with great potential for worldwide visibility. Following on from Rosetta, AIM had the ability to inspire the public by investigating how to deal with an object hurtling towards the Earth. The overall mission costs were estimated to be just about 2.5% of the overall subscriptions; the direct needs were only 1%. Ultimately – and this I very much regret – the difficult discussions among member states and a focus on direct applications and short-term return led inevitably to a situation in which I had no choice but to announce the proposal’s cancellation. The door was slammed shut but as I am convinced of the necessity of such a project, I will try to find a way back in through a window again. It is simply too important.
Rosetta's OSIRIS camera team has launched a new website to showcase their recent images of Comet 67P/Churyumov-Gerasimenko. The high-resolution images, taken either with the narrow- or wide-angle scientific imaging camera, will show the comet as recently as the day before. They will be posted to a dedicated website but followers can also subscribe to a mailing list to receive the images directly via email. The cadence of the images released will depend on the scientific operations of the spacecraft and in particular on the as-run OSIRIS observations on any given day, along with the availability of images downloaded from the spacecraft. A minimum of an image per week should be expected, up to an image a day if they are taken daily. "Following perihelion and a far excursion, we are now back at closer distances - about 100 km - to the comet, providing a view similar to that when we first arrived on 6 August 2014," says Holger Sierks, principal investigator for the camera at the Max Planck Institute for Solar System Research in Gottingen, Germany. "We'd like to share this view with the community and the general public, in near-real time, as we re-approach and eventually descend to the surface of the comet." The images will be released by a robotic system in JPG format, raw or calibrated as available, following a brief pre-selection by OSIRIS scientists. Basic 'metadata' stating the date, time, distance to the comet and the Sun, and the resolution of the image will be included with each. There will not be a detailed scientific description of the images because the goal is to provide up-to-date 'postcards' of the comet. Traditional image releases with scientific interpretation will still be made, separately, in the usual way. The images will also be added to our ESA galleries and shared on our Rosetta social media channels. In addition, we plan to showcase them in a weekly blog post alongside our regular navigation camera (NavCam) CometWatch feature. "This new initiative is a welcome addition to our long-established NavCam CometWatch releases, and gives us another way to enjoy riding along with Rosetta as it follows the comet through the Solar System," notes Patrick Martin, ESA's Rosetta mission manager. "Now that we're closer to the comet again we're looking forward to seeing its surface in more detail. We're also looking forward to sharing a fantastic view as Rosetta descends to the surface of the comet next September," says Matt Taylor, ESA's Rosetta project scientist.
Both major assemblies (Base and optical tube) have now been wrapped, and are in storage at Laminating Technologies. They will remain in "care and preservation" until the dome is ready.
Since the weather has put a stop to groundwork for the dome, attention has turned to the telescope itself.
Powys County Council has granted us planning permission to build the dome for the 24" Schmidt Camera.
Well, the telescope is in Wales and secure. Here’s how it happened.