“Asteroids Will Kill You!” That was the title of a presentation that Bill Nye, CEO of The Planetary Society (TPS) who is also known as The Science Guy, gave on the final day of the 2013 Space Tech Expo at the Long Beach Convention Center in California.
Since today is the second annual Asteroid Day, which falls on the anniversary of the Tunguska Event in 1908, I thought I would share what I learned this year about the threat of asteroid impact, what efforts are being made to detect asteroids, and the ideas to defend the Earth from asteroid impact.
I presented the talk below about Defending Earth from Asteroids at the AIAA Orange County (OC) Aerospace Systems and Technology (ASAT) conference. Since I don’t have audio or video for the presentation, I’ve included my notes for each slide below.
Background: I gave a presentation about the problem of space debris (which I will post about in another blog) at the 2015 AIAA OC ASAT conference, and someone brought up this question of planetary defense against asteroids at the end of my talk. I had to admit that I hadn’t really looked into that subject, although I was vaguely aware of TPS’s laser bees project. That made me wonder what other projects there are concerning planetary defense. Background image: http://www.nasa.gov/mission_pages/asteroids/multimedia/pia16828.html
In his presentation, Bill emphasized that an asteroid impact is the only preventable natural disaster and talked about TPS’s planetary defense efforts. Through its Shoemaker Near-Earth Object Grant Program, The Planetary Society funds amateur observers, observers in developing countries, and professional astronomers to monitor near-Earth asteroids (NEAs).
Why would Bill Nye say something like “Asteroids will kill you!” other than to get everyone’s attention? Well, there are many asteroids that cross Earth’s orbit. The geologic record shows that many collisions have occurred in Earth’s history, and over 100 large impact craters (see Slide 4) are still visible across the globe. Color shows the age of formation divided into four groups. White stars depict the epicenters of two largest air blasts of the 20th century – Tunguska (1908) and Brasil (1930). Note: Time units are either in kiloannum (ka) or megaannum (Ma). Reference: http://tsun.sscc.ru/hiwg/data.htm
We had a reminder of the risk of asteroids in February of 2013. See a video about the Chelyabinsk meteor on slide 5.
Asteroids pass close to Earth quite often, as can be seen on NASA JPL’s Near-Earth Object (NEO) Close Approach Tables. I included a snapshot of the tables from April (slide 6) and noticed one asteroid, the third one on the list, was probably bigger than the Chelyabinsk meteoroid and going at about the same speed as well.
Slides 8 and 9 show asteroid detection programs in the U.S. and worldwide. The search program titles are links. Here are the programs mentioned:
- SPACEWATCH® is the name of a group at the University of Arizona’s Lunar and Planetary Laboratory. Spacewatch explores the various populations of small objects in the solar system finding potential targets for interplanetary spacecraft missions, providing follow-up astrometry of such targets, and finding and following up objects that might present a hazard to the Earth.
- Lincoln Near Earth Asteroid Research (LINEAR) is an MIT Lincoln Laboratory program funded by the United States Air Force and NASA. The goal of LINEAR is to demonstrate the application of technology originally developed for the surveillance of Earth orbiting satellites, to the problem of detecting and cataloging near-Earth asteroids—also referred to as Near Earth Objects (NEOs)—that threaten the Earth.
- The NEOWISE project is the asteroid-hunting portion of the Wide-field Infrared Survey Explorer (WISE) mission. Funded by NASA’s Planetary Science Division, NEOWISE harvests measurements of asteroids and comets from the WISE images and provides a rich archive for searching WISE data for solar system objects.
- Catalina Sky Survey (CSS) is a project to discover comets and asteroids, and to search for NEOs. More specifically, CSS is to search for any potentially hazardous asteroids that may pose a threat of impact.
- Pan-STARRS — the Panoramic Survey Telescope & Rapid Response System
- The Planetary Society’s Gene Shoemaker NEO Grant program seeks to assist amateur observers, observers in developing countries, and under-funded professional observers contributing to vital NEO research. Since 1997, the Society has awarded 43 Shoemaker NEO grants totaling about $270,000 to observers from 16 different countries on 5 continents.
- The Campo Imperatore Near Earth Object Survey (CINEOS) is a dedicated search and follow-up program of Near-Earth Objects, with special emphasis to the study of objects located at small solar elongations. It is carried out at the Campo Imperatore station of the Rome Observatory near the summit of the Gran Sasso Mountain, at about 2,150 meters of elevation.
- Asiago-DLR Asteroid Survey (ADAS) is a dedicated program to search and follow-up asteroids and comets, with special emphasis on NEO’s in cooperation and support of global efforts in NEO-research. The program is operated at the Schmidt-telescope at Asiago-CimaEkar, as a joint venture between the Department of Astronomy of the University and the Astronomical Observatory of Padova in Italy, and the DLR – Institute of Space Sensor Technology and Planetary Exploration, Berlin-Adlershof, Germany.
- The ESA NEO Coordination Centre (NEOCC) is the operative centre of the SSA-NEO Segment. It is located at ESA’s establishment ESRIN (Frascati, Italy). Its aim is to coordinate and contribute to the observation of small Solar System bodies in order to evaluate and monitor the NEO hazard.
- The Spaceguard Foundation is an international, private organization that groups observers, both professional and amateur, as well as people and organizations with no particular astronomical background who want to contribute to the activity of the Foundation. Pursue the following purposes: to promote and co-ordinate activities for the discovery, pursuit (follow-up) and orbital calculation of the NEO at an international level; to promote study activities – at theoretical, observational and experimental levels – of the physical-mineralogical characteristics of the minor bodies of the solar system, with particular attention to the NEO; and to promote and co-ordinate a ground network (the Spaceguard System), backed up by possible satellite network, for the discovery observations and for astrometric and physical follow-up.
Slide 10 shows the cumulative number of known Near-Earth Asteroids (NEAs) versus time. Totals are shown for NEAs of all sizes, those NEAs larger than ~140m in size, and those larger than ~1km in size. (Captured on 4/21/2016)
“With over 90% of the near-Earth objects larger than one kilometer already discovered, the NEO Program is now focusing on finding 90% of the NEO population larger than 140 meters.” The number of asteroids is estimated by using data from NEOWISE – “like taking a poll before a big election”. Consider NEOWISE data to contain a representative sample of the asteroids. The researchers made a fake movie of a fake population of asteroids, then compared the fake sample to real sample. This process was repeated until survey movie matches what was really seen.
Slides 12 to 18 show ideas of how to mitigate the risk of asteroid impact. The titles of the slides link to the reference material. The ideas include:
- Laser Bees spacecraft swarming around a dangerous asteroid.
- A Directed Energy System for Targeting of Asteroids and exploRation (DE-STAR) which was presented at the Planetary Defense Conference in 2015. The presentation concluded that planetary defense is feasible with directed energy which is capable (according to lab tests) and scalable and able to deflect virtually all known threats. Pre-deployment is key to this response.
- Using a spacecraft as a gravity tractor. The downside of this idea is that it may take many years to change the asteroid’s course enough to avoid collision with Earth.
- Kinetic impact requires a spacecraft to either fire a projectile at an asteroid or to fly into the asteroid itself. The impact excavates a crater on the asteroid which eject material from the asteroid creating momentum. NEOShield is a European consortium proposing such a spacecraft for planetary defense.
- A nuclear standoff burst creates momentum when material is ejected from the resulting crater. This deflection method has never been tested and carries political and social stigmas since it involves the use of nuclear explosives.
- A Hypervelocity Asteroid Intercept Vehicle (HAIV) mission architecture, which blends a hypervelocity kinetic impactor with a subsurface nuclear explosion for optimal fragmentation and dispersion of hazardous NEOs, has been developed with the help of two rounds of NIAC funding. Again the nuclear option presents political and social hurdles.
- The Asteroid Impact and Deflection Assessment (AIDA) mission is being planned by an international collaboration. “The mission concept involves two independent spacecraft – the Double Asteroid Redirection Test (DART), led by the John Hopkins University Applied Physics Laboratory, and the Asteroid Impact Monitor (AIM), led by the European Space Agency (ESA). The primary objective of the AIDA mission would be to demonstrate a kinetic-impact deflection and characterize the binary near-Earth asteroid 65803 Didymos (1996 GT). A close-Earth encounter of Didymos in October 2022 provides the optimal opportunity for such a mission, allowing an impact on Didymos’ secondary body to change its orbital period around the primary by an amount measurable both from ground observatories and from a rendezvous spacecraft. The DART spacecraft would be the asteroid impactor, and the AIM spacecraft would be the rendezvous spacecraft.”
There are some additional good resources available, including the NEO Deflection App announced earlier this year, a joint project between Aerospace Corporation and NASA JPL.
NASA announced a Planetary Defense Coordination Office in January of this year to coordinate its “ongoing program for detecting and tracking near-Earth objects (NEOs)”. NASA also has an Asteroid Grand Challenge to encourage multidisciplinary collaborations to work on the problems of asteroid detection, tracking, characterizing, and mitigating impact.
The International Acadamy of Astronautics (IAA) holds a Planetary Defense Conference every 2 years. It was last held in April 2015 in Frascati, Italy, and the next one is scheduled for May 2017 in Tokyo, Japan.