Near Earth Asteroid Flyby (2012 TC4)

[bystander]

Asteroid Flyby Will Benefit NASA Detection & Tracking Network
NASA | JPL-Caltech | Planetary Defense Coordination Office | 2017 Jul 28

[img3="On Oct. 12, 2017, asteroid 2012 TC4 will safely fly past Earth. Even though scientists cannot yet predict exactly how close it will approach, they are certain it will come no closer to Earth than 4,200 miles (6,800 kilometers). Credits: NASA/JPL-Caltech"]https://www.nasa.gov/sites/default/file ... raphic.jpg[/img3][hr][/hr]

NASA scientists are excited about the upcoming close flyby of a small asteroid and plan to use its upcoming October close approach to Earth as an opportunity not only for science, but to test NASA's network of observatories and scientists who work with planetary defense.

The target of all this attention is asteroid 2012 TC4 -- a small asteroid estimated to be between 30 and 100 feet (10 and 30 meters) in size. On Oct. 12, TC4 will safely fly past Earth. Even though scientists cannot yet predict exactly how close it will approach, they are certain it will come no closer than 4,200 miles (6,800 kilometers) from the surface of Earth. The asteroid has been out of range of telescopes since 2012.

"Scientists have always appreciated knowing when an asteroid will make a close approach to and safely pass the Earth because they can make preparations to collect data to characterize and learn as much as possible about it," said Michael Kelley, program scientist and NASA Headquarters lead for the TC4 observation campaign. "This time we are adding in another layer of effort, using this asteroid flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid threat." ...

NASA's Planetary Defense Coordination Office

Upcoming Asteroid Flyby Will Help NASA Planetary Defense Network
University of Arizona | Lunar and Planetary Laboratory | 2017 Jul 28

For the first time, an actual, but harmless, space rock will be used for an observational campaign to test NASA's network of observatories and scientists who work with planetary defense.

[bystander]

A Very Close Encounter
ESO Announcement | 2017 Aug 09

[c][imghover=https://cdn.eso.org/images/screen/ann17052b.jpg]https://cdn.eso.org/images/screen/ann17052a.jpg[/imghover]Credit: ESO / ESA NEOCC / Olivier Hainaut (ESO),
Marco Micheli (ESA) and Detlef Koschny (ESA)[/c][hr][/hr]

Back in October 2012, the near-Earth asteroid 2012 TC4 had a close encounter with Earth. It passed our planet at a distance only a quarter of that between the Earth and the Moon. In October 2017, this small asteroid, with a size of only about 15 to 30 metres, will return for another very close fly-by, making it the perfect object to test the asteroid detection and tracking network.

As 2012 TC4 could not be observed for several years, its orbit was not very well known. In particular, astronomers could not yet predict just how close it will come to Earth during its next fly-by in 2017. So finding it again and observing it in detail are crucial to learning more about how close it will get to Earth and refining our understanding of the path it will take.

Because the asteroid is so small and is still far away it is very faint and hence hard to spot. Nevertheless, using ESO’s Very Large Telescope (VLT), astronomers were able to obtain this image of our future visitor for the first time in many years, and to compute its trajectory. This new observation implies a fly-by distance from the surface of the Earth of about 44 000 kilometres, corresponding to 6.85 Earth radii, on 12 October 2017.

ESO’s VLT is not the only telescope observing 2012 TC4. A major international observational campaign to identify and study this object is currently under way, taking advantage of its very close encounter. Now that the VLT has found 2012 TC4 again, a new, updated orbit is available. Various telescopes all over the world are now able to locate the asteroid, and will soon start to observe it, taking advantage of this rare opportunity to study an asteroid in such detail.

[bystander]

Astronomers Complete First International Asteroid Tracking Exercise
NASA | JPL-Caltech | 2017 Nov 03

An international team of astronomers led by NASA scientists successfully completed the first global exercise using a real asteroid to test global response capabilities.

Planning for the so-called “TC4 Observation Campaign” started in April, under the sponsorship of NASA’s Planetary Defense Coordination Office. The exercise commenced in earnest in late July, when the European Southern Observatory’s Very Large Telescope recovered the asteroid. The finale was a close approach to Earth in mid-October. The goal: to recover, track and characterize a real asteroid as a potential impactor -- and to test the International Asteroid Warning Network for hazardous asteroid observations, modeling, prediction and communication.

The target of the exercise was asteroid 2012 TC4 -- a small asteroid originally estimated to be between 30 and 100 feet (10 and 30 meters) in size, which was known to be on a very close approach to Earth. On Oct. 12, TC4 safely passed Earth at a distance of only about 27,200 miles (43,780 kilometers) above Earth’s surface. In the months leading up to the flyby, astronomers from the U.S., Canada, Colombia, Germany, Israel, Italy, Japan, the Netherlands, Russia and South Africa all tracked TC4 from ground- and space-based telescopes to study its orbit, shape, rotation and composition. ...

[neufer]

[b][color=#0000FF]The delay-doppler radar images had a resolution of 1.9 meters/pixel, the highest resolution ever obtained using Goldstone transmissions.[/color][/b]

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<<On 12 October 2017 at 5:42 UT, the asteroid 2012 TC4 passed 50,151 km from Earth. Paul Chodas of NASA's Center for Near-Earth Object Studies, and Vishnu Reddy of the University of Arizona's Lunar and Planetary Laboratory, viewed the 2017 flyby (inside of the orbit of the Moon) as a way to test and refine the global asteroid detection and tracking network designed to give warning of objects heading toward Earth.

The asteroid was not expected to become bright enough to be recovered with automated astronomical surveys until early September, but it was recovered with the Very Large Telescope on July 27, 2017 at apparent magnitude 26.8 while the asteroid was 0.4 AU from Earth, making it one of the dimmest asteroid recoveries ever. As such, 2012 TC4 has become the first known asteroid ever to be observed passing less than 1 Lunar distance from Earth twice in a row. As a result of the 2017 recovery observations, it was known that on October 12, 2017 at 5:42 UT, the asteroid would pass 50,150 km from Earth. 2012 TC4 reached a maximum apparent magnitude of 12.9 just prior to its closest approach, soon after which it came too close to the Sun to be seen with telescopes. The Earth approach of 2017 increased the asteroid's orbital period from 1.67 years to 2.06 years.

Studies of the asteroid's light curve in October 2012, found it to have a rotation period of 12 minutes and 14 seconds with a brightness variation of 0.93 magnitude. 2012 TC4 is a fast rotator, which is rather typical for its small size: ~15 m long & ~8 m wide.. The fastest rotator currently known is 2014 RC, a similarly-sized NEO, with a period of only 16 seconds. Lightcurves obtained during the 2017 encounter confirmed that 2012 TC4 is in a non-principal axis rotation. The spin axis varies on timescales of minutes, with a second period of 8.5 minutes. The lightcurve amplitude suggests a ratio of largest to smallest axis of at least 2.30.>>