On August 14, 2021, the small near-Earth asteroid 2021 PJ1 became on this occasion the 1.000e asteroid close to Earth to be observed by radar. The 1.001e of these objects, 2016 AJ193, followed a week later.
Since the first radar observation of an asteroid, namely (1566) Icarus in 1968, this technique has enriched our knowledge of theobjects (asteroids and ) close to Earth, providing data to extend calculations of their future motion from decades to centuries, and helping to definitively predict whether an asteroid will strike Earth or not. For example, recent radar measurements of the have allowed on Earth for the next 100 years.
In addition, they can provide scientists with detailed information on propertieswhich could not be obtained otherwise than for . Depending on the size and distance of an asteroid, radar can be used to with intricate details while determining its size, , and whether or not he is accompanied by one or more .
In the case of 2021 PJ1, the asteroid was too small (20 to 30 meters wide) and the observation time too short to acquire images. However, as 1.000e a near-Earth asteroid detected by radar, it highlights efforts to study objects passing near our planet.
« Even at this distance (1.7 million kilometers, editor’s note), the planetary radar is powerful enough to detect it and measure its speed with great precision, which has considerably improved our knowledge of its future movement. », Explains Lance Benner who directs, Jet Propulsion Laboratory, NASA’s asteroid radar research program.
Benner and his team led this effort using the 70-meter antenna at Deep Space Station 14 (DSS-14) of the Deep Space Communication Complex ofof Deep Space Network (deep space communication network) near Barstow, California, to transmit waves to the asteroid and receive radar reflections, or “echoes.”
Echoes full of information
More than half of the asteroids observed by radar were observed by the305 meters from the observatory of , in Puerto Rico, before it was and in 2020 and that the antenna shortly after. Goldstone’s DSS-14 and DSS-13 (34 meters) antennas have observed 374 near-Earth asteroids to date. Fourteen others, also close to our planet, have also been observed in Australia using antennas from the Canberra Deep Space Communication Complex of Deep Space Network to transmit radio waves to asteroids andAustralian Telescope Compact Array and CSIRO’s Parkes Observatory in New South Wales to receive radar reflections.
The most recently observed asteroid by radar did not approach Earth until a week after 2021 PJ1. Between August 20 and 24, Goldstone has2016 AJ193 as it passed 3.4 million kilometers from Earth. Although this asteroid did not approach as much as 2021 PJ1, his radar echoes were stronger because 2016 AJ193 is about 40 times bigger, with a diameter of about 1.3 kilometers. Radar images revealed considerable detail on the object’s surface, including , small , from , concavities and possibly .
Shantanu Naidu, scientist of the Jet Propulsion Laboratory (JPL) who led the 2016 AJ sightings193 of August 22, states: ” [Cet astéroïde] has a cometary orbit, suggesting that it could be a. But we knew little about him before this ( , editor’s note), apart from its size and the proportion of solar reflected by its surface, so we planned this observation campaign years ago ».
The missionfrom NASA had already measured the size of 2016 AJ193, but Goldstone’s observations revealed more details: It is a very complex and interesting object that rotates with a period of 3.5 hours.
« In addition to statements that useand to detect and track nearly 27,000 near-Earth objects throughout our solar system, the is an important tool for monitoring approaching asteroids Said Kelly Fast, director of the Near Earth Object Observation Program at the Planetary Defense Coordination Office at NASA headquarters in Washington. “ Reaching this milestone of just over 1,000 radar detections of near-Earth asteroids underscores the important contribution that has been made to the characterization of this dangerous population, which is fundamental to our planetary defense efforts. »
What you must remember
- In August 2021, 2021 PJ1 and 2016 AJ193 became the 1.000e and 1.001e asteroids close to Earth to be observed by radar. The first asteroid observed by radar was (1566) Icarus, in 1968.
- Radar observation of asteroids makes it possible to better understand their orbit, to image their surface, to determine the size, shape and speed of rotation, and whether or not they are accompanied by one or more small satellites.