Arecibo Planetary Radar Returns to Action with Images of Asteroid Phaethon
Columbia, MD and Puerto Rico—December 22, 2017. After several months of downtime in the aftermath of Hurricane Maria, the Arecibo Observatory Planetary Radar returned to normal operation providing the best images to date of near-Earth asteroid 3200 Phaethon, which is thought to be the parent body for the Geminid meteor shower. The radar images, which are subtle at available resolution, reveal the asteroid is spheroidal in shape and has a large concavity at least several hundred meters in extent near the leading edge and a conspicuous dark, circular feature near one of the poles. Arecibo’s radar images of Phaethon have resolutions as fine as about 250 feet (75 meters) per pixel.
“These new observations of Phaethon show it may be similar in shape to asteroid Bennu, the target of NASA’s OSIRIS-REx spacecraft, but 10 times larger,” noted Dr. Patrick Taylor, Group Lead for Planetary Radar for Arecibo Observatory. “The dark feature could be a crater or some other topographic depression that did not reflect the radar beam back at us.”
Radar images obtained at Arecibo indicate Phaethon has a diameter of about 3.6 miles (6 kilometers) -- roughly 0.6 mile (1 kilometer) larger than previous estimates. Phaethon is the second largest near-Earth asteroid classified as "Potentially Hazardous." Near-Earth objects are classified as potentially hazardous asteroids (PHAs), based on their size and how closely their orbits approach Earth.
“Arecibo is an important global asset, crucial for planetary defense work because of its unique capabilities,” said Dr. Joan Schmelz, Director at Universities Space Research Association (USRA) and Deputy Director of Arecibo Observatory. “We have been working diligently to get it back up and running since Hurricane Maria devastated Puerto Rico.”
The Arecibo Observatory has the most powerful astronomical radar system on Earth. The telescope suffered minor structural damage from the category 4 hurricane, the strongest to hit the island since 1928. Some days after the storm, the telescope resumed radio astronomy observations, while planetary radar observations, which require high power and diesel fuel for generators at the site, resumed operations in early December after commercial power returned to the observatory.
Asteroid Phaethon was discovered on Oct. 11, 1983, by NASA's Infrared Astronomical Satellite (IRAS). Observations of Phaethon were conducted at Arecibo from Dec. 15 through 19, 2017, using the NASA-funded planetary radar system. At time of closest approach on Dec. 16 at 3 p.m. PST (6 p.m. EST, 11 p.m. UTC) the asteroid was about 6 million miles (10 million kilometers) away, or about 26.8 times the distance from Earth to the moon. The encounter is the closest the object will come to Earth until 2093.
Radar has been used to observe hundreds of asteroids. When these small, natural remnants of the formation of our solar system pass relatively close to Earth, deep space radar is a powerful technique for studying their sizes, shapes, rotation, surface features, and roughness, and for more precise determination of their orbital path.
The Arecibo Planetary Radar Program is fully funded by NASA through a grant to USRA from the Near-Earth Object Observations program. The Arecibo Observatory is a facility of the National Science Foundation operated under cooperative agreement by SRI International, Universities Space Research Association (USRA), and Universidad Metropolitana.
NASA's Planetary Defense Coordination Office is responsible for finding, tracking and characterizing potentially hazardous asteroids and comets coming near Earth, issuing warnings about possible impacts, and assisting coordination of U.S. government response planning, should there be an actual impact threat.
More information about the National Science Foundation’s Arecibo Observatory can be found at: http://www.naic.edu
More information about asteroids and near-Earth objects can be found at:
For more information about NASA's Planetary Defense Coordination Office, visit:https://www.nasa.gov/planetarydefense
For asteroid and comet news and updates, follow AsteroidWatch on Twitter: Twitter.com/AsteroidWatch.
For updates on planetary radar observations at Arecibo Observatory, follow AreciboRadar on Twitter:
Founded in 1969, under the auspices of the National Academy of Sciences at the request of the U.S. Government, the Universities Space Research Association (USRA) is a nonprofit corporation chartered to advance space-related science, technology and engineering. USRA operates scientific institutes and facilities, and conducts other major research and educational programs, under Federal funding. USRA engages the university community and employs in-house scientific leadership, innovative research and development, and project management expertise. More information about USRA is available at www.usra.edu.
The Arecibo Observatory is a facility of the National Science Foundation operated under cooperative agreement by SRI International, Universities Space Research Association (USRA), and Universidad Metropolitana. The Arecibo Planetary Radar Program is fully funded by NASA through a grant to USRA from the Near-Earth Object Observations program. More information about the Arecibo observatory can be found at www.naic.edu
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Edgard G. Rivera-Valentín
Universities Space Research Association