Asteroid Terrestrial-impact Last Alert System

Lore & Background

ATLAS began observations in 2015 with one telescope at Haleakala, and a two-Hawaii-telescopes version became operational in 2017. Replacement of the initially substandard Schmidt corrector plates of both telescopes in June 2017 improved their image quality and sensitivity by one magnitude. In August 2018, the project obtained US$3.8 million of additional NASA funding to install two telescopes in the Southern Hemisphere, which became operational in early 2022. The newest telescope at Teide Observatory in Spain was commissioned in February 2025, but as of May 2025 does not show results on the ATLAS web page.

Each telescope surveys one quarter of the whole observable sky four times per clear night. The addition of the two southern telescopes improved ATLAS's four-fold coverage of the observable sky from every two clear nights to nightly, as well as filled its previous blind spot in the far southern sky. The full ATLAS concept consists of eight telescopes, spread over the globe for 24h/24h coverage of the full night sky.

Reader's Guide

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.' Most of the more than 1 billion rubles (approximately $33M USD at the time) damage and of the 1500 injuries caused by the 17-m Chelyabinsk meteor impact in 2013 were from window glass broken by its shock wave. 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.

As long as their radiant is not too close to the Sun, 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. 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 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 be detected by ATLAS a few days in advance.

Did You Know?

• ATLAS currently has five 0.5-meter telescopes, with the newest at Teide Observatory in Spain commissioned in February 2025.
• The Chelyabinsk meteor of 2013, which caused over 1 billion rubles in damage and 1500 injuries, was from a 17-meter object arriving from near the Sun, a blind spot for ATLAS.
• ATLAS's two southern telescopes, added in early 2022, filled its previous blind spot in the far southern sky and improved coverage to nightly.

Mission & Design Philosophy

ATLAS is a robotic survey system designed specifically to spot smaller near-Earth objects during their final approach to our planet. Unlike larger asteroids that can be tracked years or even decades ahead, the sub-140-meter objects that pose a regional threat are only visible when they are already very close to Earth. ATLAS fills this critical gap by providing a last-chance warning window of a few weeks to days before impact. The system is optimized for this specific detection challenge, scanning the sky repeatedly to catch objects that other surveys might miss in their final approach. The "Last Alert" designation in its name reflects this reality: by the time ATLAS spots these smaller bodies, there is no time left for deflection missions, which would require years of preparation and travel. The warning instead serves to alert populations in the impact zone, allowing for emergency response and damage mitigation.

Global Telescope Network & Phased Expansion

The ATLAS network has grown from a single instrument to a five-telescope global array. Observations commenced in 2015 with one 0.5-meter telescope at Haleakala on Maui. By 2017, a second Hawaiian telescope at Mauna Loa brought the system to a two-site configuration. NASA subsequently funded two additional telescopes in the Southern Hemisphere, which came online in early 2022: one at Sutherland Observatory in South Africa and another at El Sauce Observatory in Rio Hurtado, Chile. The most recent addition, at Teide Observatory in Spain, was commissioned in February 2025, though as of May 2025 it had not yet published results on the ATLAS web page. Each individual telescope surveys one quarter of the observable sky four times per clear night. The two southern sites were particularly important because they eliminated ATLAS's previous blind spot in the far southern sky and improved the system's four-fold sky coverage from every two clear nights to nightly.

The Threat Landscape ATLAS Addresses

The motivation for ATLAS stems from a sobering statistical reality: stony asteroids roughly four meters across enter Earth's atmosphere about once per year, while seven-meter objects arrive roughly every five years, carrying kinetic energy comparable to the Hiroshima bomb. Twenty-meter asteroids strike approximately twice per century. The 2013 Chelyabinsk event, involving a roughly 20-meter object, remains the largest continental impact since the 1908 Tunguska event and the only historical impact known to have caused widespread injuries. Stephen Hawking identified a large asteroid collision as the greatest threat to our planet in his 2018 book, and the B612 Foundation declared in the same year that a devastating impact is a certainty. The US National Science and Technology Council warned in June 2018 that America was unprepared for such an event. While kilometer-class asteroids are now 97% cataloged and none will hit Earth for at least a century, the smaller, more frequent, and harder-to-detect objects remain an ongoing and unmitigated risk.

Institutional Framework & Operational Model

ATLAS is funded by NASA but developed and operated by the University of Hawaii's Institute for Astronomy, representing a public-university partnership in planetary defense. The system is fully robotic, meaning it operates without the need for human operators at the telescope sites, enabling consistent and automated sky surveys across its distributed network. Each telescope carries a specific observatory code—T05 for Haleakala, T08 for Mauna Loa, M22 for Sutherland, W68 for El Sauce, and R17 for Teide—reflecting its integration into the broader astronomical survey infrastructure. The project's growth was phased: initial Hawaiian operations were followed by a NASA-funded expansion into the Southern Hemisphere, demonstrating a deliberate strategy to build global coverage incrementally. The system's design philosophy prioritizes breadth of sky coverage and frequency of observation over the depth of individual measurements, making it well-suited to catching fast-moving, faint objects in their final approach rather than precisely characterizing well-known asteroids.