The following article was written by Brent Barbee, an Aerospace engineer and Asteroid Day 100X Signatory.
On May 15 to 19, 2017, engineers and scientists from around the globe will gather in Tokyo, Japan, to save the world.
They will be working together at the 5th International Academy of Astronautics (IAA) Planetary Defense Conference PDC) (http://pdc.iaaweb.org/), to learn more about how to defend our planet from dangerous asteroids and comets that might otherwise do us harm. The first PDC was held in 2004, and the conference has been held at venues around the world every other year since 2007. The IAA began sponsoring the PDC in 2009.
Over the past couple of decades, the importance of planetary defense studies has grown tremendously, along with our understanding of the threats and opportunities presented to us by the near-Earth objects (NEOs) of the solar system. NEOs are asteroids and comets whose orbits closely approach Earth’s orbit, and the growing number of known NEOs has recently exceeded 15,000, due in large part to the efforts of NASA’s NEO Program. That program began in 1998, at which time about 900 NEOs were known, and NASA-funded NEO surveys have been responsible for approximately 95% of NEO discoveries since then.
Some NEOs are classified as Potentially Hazardous Objects (PHOs) if their orbits pass within 7.5 million km (about 20 lunar orbit distances) of Earth’s orbit, and some objects are classified as potentially accessible (for spacecraft missions) if trajectories to visit them meet certain space mission design criteria. The definitions for these various types of NEOs can be found on NASA’s NEO Program website, http://neo.jpl.nasa.gov/, which also provides detailed information about current efforts to discover, track, monitor, and understand NEOs, including systems that automatically check for any possibilities of NEO collisions with Earth for the next 100 years. Information on all known NEOs is also available at ESA’s NEO Coordination Centre at http://neo.ssa.esa.int/.
Additional information is available on NASA’s Planetary Defense Coordination Office (PDCO) website: https://www.nasa.gov/planetarydefense
The most significant asteroid impact event on Earth in modern times occurred on February 15, 2013 (a mere 2 months before the 2013 IAA Planetary Defense Conference in Flagstaff, Arizona) when an NEO approximately 17 to 20 m in size collided with Earth at about 19 km/s and exploded around 29 km above the ground. That event released approximately 0.5 Megatons of energy and produced a shockwave that damaged about 7,200 buildings and injured about 1,600 people. Fortunately, there were no fatalities.
On the same date, an NEO approximately twice the size of the Chelyabinsk impactor, and packing much more mass and energy (assuming similar density), passed within 27,700 km of Earth’s surface (closer than our geosynchronous satellites). That close approach event was discovered a year in advance and was unrelated to the Chelyabinsk impactor, for which there was no warning at all (the Chelyabinsk impactor approached from our daytime sky, where current telescopes cannot look for NEOs).
The mission of the planetary defense conference series is to help our world prepare to work together to provide as much advance warning of impending NEO impacts as possible, and to know what to do when an impending NEO impact is discovered. The topics of the conference papers and presentations span NEO population modeling, NEO detection and tracking methods, design of missions to deal with NEOs, preparations for emergency disaster response in the event of an NEO impact, the effects of NEO impacts on Earth, key aspects of the international decision-making processes, and public education about NEOs.
Telescopes around the world continue to improve their search capabilities for NEOs, and the annual NEO discovery rate has reached around 1,500 per year (and climbing), but there is much more work to be done. While we believe that most of the 1 km size and larger NEOs have been discovered (and found to not pose an Earth impact threat during the next century), much less than a percent of the several-hundred-meter size and smaller NEOs have been found (including NEOs as small as several meters in size). While we believe that we have the fundamental technology needed to stop an NEO from colliding with Earth (with sufficient advance warning), there is much work to be done to streamline the mission design process, test the NEO mitigation techniques, and establish procedures for effective international response to a threatening NEO.
The conference series directly addresses these frontiers in the planetary defense field, not only by bringing together experts to present and discuss the latest research results, but also by conducting a detailed NEO threat response exercise involving a fictitious NEO that may be on an Earth-impacting orbit. The initial details of this exercise scenario are available on the aforementioned NASA NEO Program website at http://neo.jpl.nasa.gov/pdc17/, and researchers are already actively studying this fictitious scenario in preparation for submitting abstracts to the conference, which are due on January 6, 2017. A similar exercise conducted at the 2015 IAA Planetary Defense Conference is fully documented online at http://neo.jpl.nasa.gov/pdc15/.
While the 2017 conference is sure to offer a wide range of fascinating presentations by worldwide experts and an exciting hypothetical threat exercise that will unfold day by day during the conference, perhaps the best part of the conference is that it brings us together now, before a threatening NEO is discovered, to learn how work together for the defense of our planet against what is perhaps the only natural disaster that we have the technology to prevent.
By having the foresight and willingness to learn how to work together now, rather than waiting to prepare until we’re faced with an emergency, we’re giving ourselves the best chance to succeed when nature puts us to the test, and this represents a substantial milestone for our species and our planet.