Comet C/2020 M3 (ATLAS) was discovered on 27 June 2020. The acronym ATLAS stands for Asteroid Terrestrial-Impact Last Alert System, based on the Hawaiian islands. Two telescopes of the robotic early warning system are designed to detect smaller near-Earth objects a few weeks to days before they might impact Earth. Since 2017, the scopes survey one quarter of the observable sky four times each clear night. The system is NASA funded and operated by the University of Hawaii.
Orbits near the Earth of objects larger than 1 km are well-known. Most are well documented and predicted years in advance of their close approaches to Earth. Objects down to 140 meters in size are harder to see. It is estimated ⅓ of them have been found. None of those found so far are predicted to threaten Earth in the next century.
Smaller objects less than 140 meters are detected only when they are much closer to Earth. Late discovery means there is the greater potential for a locally catastrophic collision with little warning time if they are on a collision course. ATLAS looks for these smaller objects. Comet C/2020 M3 (ATLAS) was discovered by this system.
The comet became a popular object for amateur astronomers to image. By November 2020 it was nearing the Orion constellation. This image on 6 Nov 2020 was by José J. Chambó at his web site Cometografia.es. I thought it would be interesting to image this comet several times as it passed through Orion.
The orbit brought the comet between Earth and Mars. This short video shows a 3-D perspective of the orbit in early November. From our viewing platform of Earth, the constellation Orion was in the distance beyond Mars in the opposite direction from the Sun. The comet would appear to pass through Orion from our point of view.
The path through Orion would take it toward the top of this image. I planned to used images requested from the Gemini robotic telescope operated by the University of Iowa in southern Arizona. My first requested image was on 5 Nov 2020 when the comet was near the bright star Rigel at the bottom-center of this image.
It turned out pretty well. The next requested image on 11 Nov was to see the comet aligned with the 3 stars in Orion’s belt making it easy to locate.
My request for that image got no response from the telescope. I tried again a few days later to no avail. The person coordinating image requests sent a message out to the users that the scope was down for an unknown time for repairs. I gave up on the project.
On 8 Feb, I got an email saying an image I had requested was ready. I wondered which image it was. A follow-up email from the coordinator said the computer controlling the robotic telescope started having software issues on 10 Nov. They tried to start up again on 18 Dec and discovered the motor on the drive of the telescope mount needed to be repaired. My image mentioned in the email was one of the tests to see if the system was operational again.
In the three months since I requested those images of C/2020 M3, it moved farther from the Sun and dimmed from magnitude 8 to magnitude 14. Was it even still visible? If so, it should be in the center of the small box in this image.
I adjusted the software and zoomed in hoping to see some evidence of the comet. There it was, barely visible. Time to say goodbye to C/2020 M3 (ATLAS).