Planetary Defense

Planetary Defense
Name	Planetary Defense
Caption	Artistic depiction of a kinetic impactor deflection test.

Planetary Defense refers to the methods and strategies employed to protect Earth from potential impacts by near-Earth objects such as asteroids and comets. This multidisciplinary field involves the detection, tracking, characterization, and potential deflection of hazardous celestial bodies. Coordinated efforts are led by agencies like NASA and the European Space Agency, supported by international treaties and observational networks like the Catalina Sky Survey.

Overview

The primary goal is to prevent catastrophic events similar to the Chicxulub impactor that contributed to the Cretaceous–Paleogene extinction event. Modern programs were significantly catalyzed by the 1994 impact of Comet Shoemaker–Levy 9 on Jupiter. Key coordinating bodies include the International Asteroid Warning Network and the Space Mission Planning Advisory Group, which operate under the auspices of the United Nations Committee on the Peaceful Uses of Outer Space. The Planetary Defense Coordination Office at NASA Headquarters oversees United States efforts.

Detection and Tracking

Global surveys systematically scan the skies to identify and catalog potentially hazardous objects. Major ground-based facilities include the Pan-STARRS telescopes in Hawaii, the Asteroid Terrestrial-impact Last Alert System, and the Vera C. Rubin Observatory under construction in Chile. Space-based assets like the NEOWISE mission have provided crucial infrared data. Tracking and orbit determination are refined by networks such as the Goldstone Deep Space Communications Complex and the European Space Tracking system. The Torino Scale and the Palermo Technical Impact Hazard Scale are used to communicate potential impact risks.

Deflection and Disruption Techniques

Several theoretical and tested methods aim to alter the trajectory of a threatening object. The Double Asteroid Redirection Test successfully demonstrated a kinetic impactor technique by striking the moonlet Dimorphos of the asteroid 65803 Didymos. Other proposed concepts include the gravity tractor, which uses a spacecraft's gravitational pull, and ion beam deflection. More energetic options, such as a stand-off nuclear explosive device, have been studied by entities like the Lawrence Livermore National Laboratory but present significant policy challenges under treaties like the Partial Nuclear Test Ban Treaty.

Preparedness and Mitigation

Preparedness involves impact scenario modeling and developing civil response protocols. Regular exercises, such as those conducted at the International Academy of Astronautics Planetary Defense Conference, simulate detection to response timelines. Mitigation for smaller, unavoidable impacts focuses on regional evacuation planning and disaster management, leveraging agencies like the Federal Emergency Management Agency. Research into impact effects, such as tsunami generation or atmospheric entry shock waves, is conducted at institutions like the Los Alamos National Laboratory.

International Cooperation and Policy

Collaboration is essential due to the global nature of the threat. The United Nations Office for Outer Space Affairs facilitates dialogue and the implementation of the International Asteroid Warning Network. Bilateral agreements, such as those between NASA and the European Space Agency for the Hera mission, are common. Legal and policy frameworks are shaped by existing space law, including the Outer Space Treaty, and discussions at forums like the Conference on Disarmament regarding the use of nuclear deflection methods.

Notable Missions and Projects

Key missions have advanced both detection and deflection capabilities. NEAR Shoemaker was the first to orbit and land on an asteroid, 433 Eros. The Hayabusa and Hayabusa2 missions by the Japan Aerospace Exploration Agency returned samples from 25143 Itokawa and 162173 Ryugu, respectively. The OSIRIS-REx mission collected material from 101955 Bennu. For deflection, the landmark DART (spacecraft) mission was followed by the planned Hera mission to study the aftermath. Future concepts include the NEO Surveyor space telescope and the Comet Interceptor mission.

Category:Astronomical events Category:Space hazards Category:Space policy