Asteroid Terrestrial-impact Last Alert System


Asteroid Terrestrial-impact Last Alert System
Observatory codeT05 (ATLAS-HKO)

The Asteroid Terrestrial-impact Last Alert System (ATLAS; Observatory codes T05 and T08) is a robotic astronomical survey and early warning system optimized for detecting smaller near-Earth objects a few weeks to days before they impact Earth.

Funded by NASA, and developed and operated by the University of Hawaii's Institute for Astronomy, the system currently has two 0.5-meter telescopes located 160 km apart, at Haleakala (ATLAS-HKO) and Mauna Loa (ATLAS-MLO) observatories.

ATLAS began observations in 2015 with one telescope and its two-telescopes version has been operational since 2017. Each of the two telescopes surveys one quarter of the whole observable sky four times per clear night, for a four-fold coverage of the observable sky every two clear nights.[1]

The project has obtained NASA funding for two additional telescopes in the Southern hemisphere. Once operational, those two telescopes will improve ATLAS's four-fold coverage of the observable sky from every two clear nights to nightly, and will fill its current blind spot in the far southern sky.[2]


Major astronomical impact events have significantly shaped Earth's history, having been implicated in the formation of the Earth–Moon system, the origin of water on Earth, the evolutionary history of life, and several mass extinctions. Notable prehistorical impact events include the Chicxulub impact, 66 million years ago, believed to be the cause of the Cretaceous–Paleogene extinction event.[3] The 37 million years old asteroid impact that caused Mistastin crater generated temperatures exceeding 2,370 °C, the highest known to have naturally occurred on the surface of the Earth.[4]

Throughout recorded history, hundreds of Earth impacts (and meteor air bursts) have been reported, with some small fraction causing deaths, injuries, property damage, or other significant localised consequences.[5] Stony asteroids with a diameter of 4 meters (13 ft) enter Earth's atmosphere approximately once per year.[6] Asteroids with a diameter of 7 meters enter the atmosphere about every 5 years, with as much kinetic energy as the atomic bomb dropped on Hiroshima (approximately 16 kilotons of TNT), of which their air burst represents about one third, or 5 kilotons.[6] These relatively small asteroids ordinarily explode in the upper atmosphere and most or all of the solids are vaporized.[7] Asteroids with a diameter of 20 m (66 ft) strike Earth approximately twice every century. One of the best-known impacts recorded in historical times is the 50 meter 1908 Tunguska event, which leveled several thousand square kilometers of forest in a very sparsely populated part of Siberia, Russia. Such an impact over a more populous region would have caused locally catastrophic damage.[8] The 2013 Chelyabinsk meteor event is the only known impact in historical times to have resulted in a large number of injuries, with the potential exception of the possibly highly deadly but poorly documented 1490 Ch'ing-yang event in China. The approximately 20 meter Chelyabinsk meteor is the largest recorded object to have impacted a continent of the Earth since the Tunguska event.

Future impacts are bound to occur, with much higher odds for smaller regionally damaging asteroids than for larger globally damaging ones. The 2018 final book of physicist Stephen Hawking, Brief Answers to the Big Questions, considers a large asteroid collision the biggest threat to our planet.[9][10][11] In April 2018, the B612 Foundation reported "It's a 100 per cent certainty we'll be hit [by a devastating asteroid], but we're not 100 per cent sure when."[12] In June 2018, the US National Science and Technology Council warned that America is unprepared for an asteroid impact event, and has developed and released the "National Near-Earth Object Preparedness Strategy Action Plan" to better prepare.[13][14][15][16][17]

Annually discovered NEAs by survey since 1995
Large NEAs (at least 1 km in diameter) discovered each year
  •   LINEAR
  •   NEAT
  •   Spacewatch
  •   LONEOS
  •   CSS
  •   Pan-STARRS
  •   Others

Larger asteroids can be detected even while far from the Earth, and their orbits can therefore be determined very precisely many years in advance of any close approach. Thanks largely to Spaceguard cataloging initiated by a 2005 mandate of the United States Congress to NASA,[18] the inventory of the approximately one thousand Near Earth Objects with diameters above 1 kilometer was for instance 97% complete in 2017.[19] The estimated completeness for 140 meter objects is around one third, and slowly improving. Any impact by one of these known asteroids would be predicted decades to centuries in advance, long enough to consider deflecting them away from Earth. None of them will impact Earth for at least the next century, and we are therefore largely safe from globally civilisation-ending kilometer-size impacts for at least the mid-term future. Regionally catastrophic sub-km impacts, on the other hand, remain a possibility at this point in time.

Sub-150m impacting asteroids would not cause large scale damage but are still locally catastrophic. They are much more common and they can, by contrast to larger ones, only be detected when they come very close to the Earth. In most cases this only happens during their final approach. Those impacts therefore will always need a constant watch and they typically cannot be identified earlier than a few weeks in advance, far too late for interception. According to expert testimony in the United States Congress in 2013, NASA would presently require at least five years of preparation before a mission to intercept an asteroid could be launched.[20] This time could be much reduced by pre-planning a ready to launch mission, but meeting the asteroid and then deflecting it by least the diameter of the Earth after its interception will always need several uncompressible additional years.


The Last Alert part of the ATLAS name acknowledges that the system will find smaller asteroids years too late for potential deflection but would provide the days or weeks of warning needed to evacuate and otherwise prepare a target area. According to ATLAS project lead John Tonry, "that's enough time to evacuate the area of people, take measures to protect buildings and other infrastructure, and be alert to a tsunami danger generated by ocean impacts".[21] Most of the more than 1 billion rubles damage[22] and of the 1500 injuries[23] caused by the 17-m Chelyabinsk meteor impact in 2013 were from window glass broken by its shock wave.[24] With even a few hours advance warning, those losses and injuries could have been much reduced by actions as simple as propping all windows open before the impact and staying away from them.


The ATLAS project was developed at the University of Hawaii with US$5 million funding from NASA,[25] and its first element was deployed in 2015. This first telescope became fully operational at the end of 2015, and the second one in March 2017. Replacement of the initially substandard Schmidt corrector plates of both telescopes in June 2017 brought their image quality closer to its nominal 2 pixels (3.8") width and consequently improved their sensitivity by one magnitude.[26] In August 2018, the project obtained US$3.8 million of additional NASA funding to install two telescopes in the Southern hemisphere, one of which will be hosted by the South African Astronomical Observatory,[27][28] and the other most likely installed in Chile. This geographical expansion of ATLAS will provide visibility of the far Southern sky, more continuous coverage, better resilience to bad weather, and additional information on the asteroid orbit from the parallax effect.[29] The full ATLAS concept consists of eight telescopes, spread over the globe for 24h/24h coverage of the full nightsky.

As long as their radiant is not too close to the Sun, and for the current Hawaii-based system not too far into the Southern hemisphere, the automated system provides a one-week warning for a 45 metres (150 ft) diameter asteroid, and a three-week warning for a 120 m (390 ft) one.[25] By comparison, the February 2013 Chelyabinsk meteor impact was from an object estimated at 17 m (60 ft) diameter. Its arrival direction happened to be close to the Sun[30] and it therefore was in the blind spot of any Earth-based visible light warning system. A similar object arriving from a dark direction would now be detected by ATLAS a few days in advance.[31]

As a by-product of its main design goal, ATLAS can identify any moderately bright variable or moving object in the night sky. It therefore also looks for variable stars,[32] supernovae,[25] non-impacting asteroids, comets, and dwarf planets.

Design and operation

The full ATLAS concept consists of eight 50-centimeter diameter f/2 Wright-Schmidt telescopes, spread over the globe for full-night-sky and 24h/24h coverage, and each fitted with a 110 Megapixel CCD array camera. The current system consists of two such telescopes operating 160 km apart on Haleakala and Mauna Loa in the Hawaiian Islands, ATLAS1 and ATLAS2,[33] with the third telescope under construction at the South African Astronomical Observatory[34][35] and a fourth planned in Chile. These telescopes are notable for their large 7.4° field of view — about 15 times the diameter of the full moon — of which their 10 500 × 10 500 CCD camera images the central 5.4° × 5.4°. This system can image the whole night sky visible from Hawaii with about 1000 separate telescope pointings. At 30 seconds per exposure plus 10 seconds for simultaneously reading out the camera and repointing the telescope, each ATLAS unit can therefore scan the whole visible sky a little over once each night, with a median completeness limit at apparent magnitude 19.[36] Since the mission of the telescope is to identify moving objects, each telescope actually observes one quarter of the sky four times in a night at approximately 15-minute intervals. The four exposures allow to automatically link multiple observations of an asteroid into a preliminary orbit, with some robustness to the loss of one observation to overlap between the asteroid and a bright star, and to predict its approximate position on subsequent nights. Apparent magnitude 19 is classified as "respectably but not extremely faint", and is approximately 100 000 times too faint to be seen with a naked eye from a very dark location. It is equivalent to the light of a match flame in New York viewed from San Francisco. ATLAS therefore scans the visible sky in much less depth, but much more quickly, than larger surveying telescope arrays such as University of Hawaii's Pan-STARRS. Pan-STARRS goes approximately 100 times deeper, but needs weeks instead of half a night to scan the whole sky just once.[25] This makes ATLAS better suited to finding small asteroids which can only be seen during the just few days that they brighten dramatically when they happen to pass very close to the Earth.

NASA's Near Earth Observation Program initially provided a US$5 million grant, with $3.5 million covering the first three years of design, construction and software development, and the balance of the grant to fund the systems operation for two years following its entry into full operational service in late 2015.[37] Further NASA grants fund continued operation of ATLAS until 2021[38] and the construction of two Southern telescopes.[27]

When completed in 2021, the new ATLAS site will restore the current lack of coverage in the Southern hemisphere (see Asteroid impact prediction). Sited around 120° (8 hours) east of existing surveys, the planned ATLAS South Africa and NEOSTEL telescopes will also provide warnings during the Hawaii and California daytimes. This mostly matters for small asteroids which become bright enough for detection for at most a day or two.


  • SN 2018cow, a relatively bright supernova on 2018-06-16.
  • 2018 AH, largest asteroid to pass so close to Earth since 1971 on 2018-01-02.
  • A106fgF, a 2–5 m asteroid which either passed extremely close or impacted Earth on 2018-01-22.
  • 2018 RC, near earth asteroid on 2018-09-03 (notable because it was discovered more than a day prior to closest approach on 2018-09-09).[39]
  • A10bMLz, unknown space debris, so-called "empty trash bag object" on 2019-01-25.[40]
  • 2019 MO, an approximately 4 m asteroid which impacted the Caribbean Sea South of Puerto Rico in June 2019[41]
  • C/2019 Y4 (ATLAS), comet
  • 2020 VT4, a 5–10 m object which passed closer to Earth than any other known near-miss asteroid

See also


  1. ^ Tonry; et al. (28 March 2018). "ATLAS: A High-Cadence All-Sky Survey System". Publications of the Astronomical Society of the Pacific. 130 (988): 064505. arXiv:1802.00879. Bibcode:2018PASP..130f4505T. doi:10.1088/1538-3873/aabadf. S2CID 59135328. Accessed 2018-04-14.
  2. ^ Watson, Traci (2018-08-14). "Project that spots city-killing asteroids expands to Southern Hemisphere". nature international journal of science. Springer Nature Limited. Retrieved 17 October 2018.
  3. ^ Becker, Luann (2002). "Repeated Blows". Scientific American. 286 (3): 76–83. Bibcode:2002SciAm.286c..76B. doi:10.1038/scientificamerican0302-76. PMID 11857903.
  4. ^ Dvorsky, George (2017-09-17). "The Hottest Known Temperature On Earth Was Caused By An Ancient Asteroid Strike". Gizmodo. Retrieved 2017-09-17.
  5. ^ Lewis, John S. (1996), Rain of Iron and Ice, Helix Books (Addison-Wesley), p. 236, ISBN 978-0-201-48950-7
  6. ^ a b Robert Marcus; H. Jay Melosh; Gareth Collins (2010). "Earth Impact Effects Program". Imperial College London / Purdue University. Retrieved 2013-02-04. (solution using 2600kg/m^3, 17km/s, 45 degrees)
  7. ^ Clark R. Chapman & David Morrison; Morrison (January 6, 1994), "Impacts on the Earth by asteroids and comets: assessing the hazard", Nature, 367 (6458): 33–40, Bibcode:1994Natur.367...33C, doi:10.1038/367033a0, S2CID 4305299
  8. ^ Yau, K., Weissman, P., & Yeomans, D. Meteorite Falls In China And Some Related Human Casualty Events, Meteoritics, Vol. 29, No. 6, pp. 864–871, ISSN 0026-1114, bibliographic code: 1994Metic..29..864Y.
  9. ^ Stanley-Becker, Isaac (15 October 2018). "Stephen Hawking feared race of 'superhumans' able to manipulate their own DNA". The Washington Post. Retrieved 26 November 2018.
  10. ^ Haldevang, Max de (14 October 2018). "Stephen Hawking left us bold predictions on AI, superhumans, and aliens". Quartz. Retrieved 26 November 2018.
  11. ^ Bogdan, Dennis (18 June 2018). "Comment - Better Way To Avoid Devastating Asteroids Needed?". The New York Times. Retrieved 26 November 2018.
  12. ^ Homer, Aaron (28 April 2018). "Earth Will Be Hit By An Asteroid With 100 Percent Certainty, Says Space-Watching Group B612 - The group of scientists and former astronauts is devoted to defending the planet from a space apocalypse". Inquisitr. Retrieved 25 June 2018.
  13. ^ Staff (21 June 2018). "National Near-Earth Object Preparedness Strategy Action Plan" (PDF). Retrieved 25 June 2018 – via National Archives.
  14. ^ Mandelbaum, Ryan F. (21 June 2018). "America Isn't Ready to Handle a Catastrophic Asteroid Impact, New Report Warns". Gizmodo. Retrieved 25 June 2018.
  15. ^ Myhrvold, Nathan (22 May 2018). "An empirical examination of WISE/NEOWISE asteroid analysis and results". Icarus. 314: 64–97. Bibcode:2018Icar..314...64M. doi:10.1016/j.icarus.2018.05.004.
  16. ^ Chang, Kenneth (14 June 2018). "Asteroids and Adversaries: Challenging What NASA Knows About Space Rocks - Two years ago, NASA dismissed and mocked an amateur's criticisms of its asteroids database. Now Nathan Myhrvold is back, and his papers have passed peer review". The New York Times. Retrieved 25 June 2018.
  17. ^ Chang, Kenneth (14 June 2018). "Asteroids and Adversaries: Challenging What NASA Knows About Space Rocks - Relevant Comments". The New York Times. Retrieved 25 June 2018.
  18. ^ Staff (21 June 2018). "George E. Brown, Jr. Near-Earth Object Survey ActNational Near-Earth Object". GovTrack. Retrieved 15 December 2018.
  19. ^ Matt Williams (October 20, 2017). "Good News Everyone! There are Fewer Deadly Undiscovered Asteroids than we Thought". Universe Today. Archived from the original on 2017-11-04. Retrieved 2017-11-14.
  20. ^ U.S.Congress (19 March 2013). "Threats From Space: a Review of U.S. Government Efforts to Track and mitigate Asteroids and Meteors (Part I and Part II) – Hearing Before the Committee on Science, Space, and Technology House of Representatives One Hundred Thirteenth Congress First Session" (PDF). United States Congress. p. 147. Retrieved 26 November 2018.
  21. ^ Clark, Stuart (20 June 2017). "Asteroids and how to deflect them". The Guardian. Retrieved 2013-02-22.
  22. ^ Ущерб от челябинского метеорита превысит миллиард рублей [Damage from Chelyabinsk meteorite exceeds one billion rubles] (in Russian). 15 February 2013. Archived from the original on 13 May 2013.
  23. ^ Число пострадавших при падении метеорита приблизилось к 1500 [The number of victims of the meteorite approached 1500] (in Russian). РосБизнесКонсалтинг [RBC]. 18 February 2013. Archived from the original on 2 May 2013. Retrieved 15 December 2018.
  24. ^ Heintz, Jim; Isachenkov, Vladimir (15 February 2013). "Meteor explodes over Russia's Ural Mountains; 1,100 injured as shock wave blasts out windows". Postmedia Network Inc. The Associated Press. Archived from the original on 2013-05-13. Retrieved 2017-05-28. Emergency Situations Ministry spokesman Vladimir Purgin said many of the injured were cut as they flocked to windows to see what caused the intense flash of light, which was momentarily brighter than the sun.
  25. ^ a b c d University of Hawaii at Manoa's Institute for Astronomy (18 February 2013). "ATLAS: The Asteroid Terrestrial-impact Last Alert System". Astronomy Magazine. Retrieved 2013-02-22.
  26. ^ Henry Weiland (18 February 2013). "New Schmidt Correctors Installed!". Archived from the original on 2020-03-28. Retrieved 2017-10-12.
  27. ^ a b Project that spots city-killing asteroids expands to Southern Hemisphere.
  28. ^ "SAAO to contribute to the global effort to detect Near Earth Objects."
  29. ^ Atlas: How it works. Asteroid Terrestrial-impact Last Alert System.
  30. ^ Zuluaga, Jorge I.; Ferrin, Ignacio (2013). "A preliminary reconstruction of the orbit of the Chelyabinsk Meteoroid". arXiv:1302.5377 [astro-ph.EP]. We use this result to classify the meteoroid among the near Earth asteroid families finding that the parent body belonged to the Apollo asteroids.
  31. ^ [1] Breakthrough: UH team successfully locates incoming asteroid
  32. ^ Heinze, A. N; Tonry, John L; Denneau, Larry; Flewelling, Heather; Stalder, Brian; Rest, Armin; Smith, Ken W; Smartt, Stephen J; Weiland, Henry (2018). "A First Catalog of Variable Stars Measured by the Asteroid Terrestrial-impact Last Alert System (ATLAS)". The Astronomical Journal. 156 (5): 241. arXiv:1804.02132. Bibcode:2018AJ....156..241H. doi:10.3847/1538-3881/aae47f. S2CID 59939788.
  33. ^ ATLAS Telescope 2 Installed on Mauna Loa, Ari Heinze [2] Retrieved April 7, 2017.
  34. ^ Our SAAO colleagues have completed the assembly of the ATLAS dome! [3] Retrieved December 14, 2020.
  35. ^
  36. ^ ATLAS Technical Specifications
  37. ^ Oliver, Chris. ATLAS Project Funded by NASA, Nā Kilo Hōkū (newsletter), Institute for Astronomy, University of Hawaii, No. 46, 2013, p. 1. Retrieved August 2, 2014.
  38. ^ ATLAS Update #18: 2017 March [4] Retrieved April 14, 2017.
  39. ^ Minor Planet Center records for 2018 RC
  40. ^ "Mysterious Object Spotted In Earth's Atmosphere". IFLScience. Retrieved 2020-03-31.
  41. ^ "Breakthrough: UH team successfully locates incoming asteroid". Retrieved 2020-03-31.

External links

  • Official website
  • ATLAS: The Asteroid Terrestrial-impact Last Alert System
  • Planetary Defense Conference 2017, (starts at 1h 10m 29s) on YouTube, Japan, 15 May 2017
  • asteroid List and Updates