Tracking Methods of Comets, Asteroids and Meteorites

Hollywood movies have depicted many times planetary disasters as a consequence of cosmic collisions. These grotesque situations seem to be the domain of the science fiction, but that is only because none of them has actually occurred during the history of mankind. But they have hit the Earth before humans, and not only once. It is just a matter of time before one such cosmic body will threaten the planet with extinction, and the only thing we know for sure is that it will happen sometime in the future. For humanity, tracking asteroids, meteorites, and comets is the first most important step in avoiding a hazardous collision. This paper provides an overview of the recent tracking history, as well as currently available and future tracking methods.

Despite their hazardous characteristic, tracking comets, asteroids and meteorites did not become urgency until the 1970s, when photometry, radiometry, and spectroscopy developed, contributing to the advances in the field, allowing better detection. [1] The Spacewatch program happened at the beginning of the 1980s, and marked the use of electronic techniques for asteroid tracking and observation, but their hazardous aspect was not to be acknowledged until the 1990s, especially after the impact of the comet Shoemaker-Levi into Jupiter in 1994. [2] The first program dedicated exclusively to the study of the flying rocks started as an idea in 1969 with the decision to build a telescope only for this purpose. Since very few scientists gave importance to this subject, it took years for the project to come into existence. A multi-mirror telescope was used until 1993 when the first Spacewatch 1.8 meter telescope was finally built. [3] The mission of the Spacewatch program was to continue the work done before by using photography, but implementing new technology, using faster detectors and charge-coupled scanning devices (CCD scanning), as well as computer processing. [4]

New technology helped the science of astronomy in tracking NEOs with impact possibility. Being able to observe and accurately calculate their trajectories is of crucial importance. Therefore, NASA has established the Near-Earth Object Program at the Jet Propulsion Laboratory. Its mission is to find asteroids that post the most serious threats to Earth. [5] Part of the Near-Earth Object program is NEAT – Near-Earth Asteroid Tracking. In cooperation with the US Air Force, NEAT uses a GEODSS telescope located in Hawaii to track NEOs. The telescope has a state of the art charge-coupled scanning (CCD) camera and computer system, and the data on any newly discovered Near-Earth object is immediately sent to JPL for analysis. A telescope equipped with three CCD cameras, and located at Palomar Mountain in California also joined the NEAT team, followed by the SkyMorph system allowing the search for moving objects, and in charge of archiving all images, so that no NEO gets lost. [6] Since the Near-Earth Object program started in 1998, more than 5500 asteroids and comets have been identified, of which about a thousand are potentially hazardous objects (PHA). PHAs are rocks that can come 7.5 million kilometers or closer to Earth in their trajectory around the sun, and are larger than 150 meters. [7]

Another method of tracking flying stones involves the use of the delay-Doppler radar, a very powerful tool that searches for asteroids and conveys information on their orbits, as well as and two-dimensional images of their physical characteristics. The precision of this method is invaluable in refining orbit prediction. [8] The first radar detection of an asteroid (1566 Icarus) occurred in 1968. Since then, the results of radar detection have grown exponentially. Until December 2011, the radar has detected 128 objects from the Asteroid Belt, 286 Near-Earth Asteroids, and 15 comets. One of the accomplishments of the delay-Doppler radar for the year of 2011 is the first detection of a comet since 2006, comet 45P/Honda-Mrkos-Pajdusakova. [9]

However, tracking can now be done by everybody. NASA has just announced the newest method of tracking meteoroids: the new iPhone and iPad Meteor Counter application. Using this free app, everyone interested can contribute to tracking the flying stones. The data collected from people using this app will be used to find new meteor showers, but also to keep track of these stones flying around Earth’s orbit. [10]

As far as future plans are concerned, the Large Synoptic Survey Telescope (LSST) intended to be functional by 2015 will take a picture of the sky every three nights in search for the faintest flying objects. LSST’s main mission will be to map small objects in the solar system, particularly near-Earth asteroids and Kuiper belt objects. LSST is planed to find about 80 percent of all the flying rocks of the solar system in one decade. [11] However, telescopes have blind spots, including the LSST, mainly when looking towards the sun, and can miss. Tracking comets, asteroids and meteorites can be faulty and incomplete. To avoid the blind spot issue, a suggestion was to place an infrared asteroid observatory in a Venus-like orbit that could make an inventory of all NEOs. Such a complete inventory would be valid for about a century. [12] This may be the technology of tomorrow in terms of detecting and tracking comets, asteroids and meteorites.

The science of comet, asteroid and meteorite observation and tracking has indeed developed tremendously in the past century, and has reached a quite trustworthy level. Earthlings can be confident that possible hazardous objects would be detected before catastrophic impacts. However, there is still work to do in order to detect almost all, if not all such hazardous objects. Time is precious in terms of detection, because the earlier a possible impact is discovered, the better and more precise its deflection will be. Keeping an eye on all the flying rocks is an important milestone in the survival of our species.

Asteroid Studies and Technological Developments

Human curiosity and eagerness for exploring the unknown has provided the species with an impulse towards always doing better, understanding more, and discovering new things. While from the very beginning people gazed at the sky and wondered about its mysteries, generation after generation humanity looked for new ways to support its thirst of knowledge. This is the reason behind all discoveries done my man, from fire and the wheel, to the telescope and ultimately spaceflight. New technology has not always been around to allow space exploration, but nevertheless, people have used whatever tools at hand to explore the heavens, and asteroids equally captured human attention. This paper provides an overview of the asteroid studies timeline, as well as of the latest technological developments that have influenced this field of study over the past century.

It all started in 1776 when Johann Titius of Wittenburg formulated the Titius-Bode planetary law, and concluded that, given the distances between planets, there must be an undiscovered one between Mars and Jupiter. This conclusion led to a passionate search for a missing celestial body. [1] In 1801 Giuseppe Piazzi discovered the asteroid Ceres, marking the beginning of asteroid studies. The discovery of Pallas in 1802, and of Juno in 1804 followed, and it became evident that there was not a single planet missing, but rather a whole bunch of small ones, later on acknowledged as the “asteroid belt”. At that time, the only means to conduct such studies were ground telescopes and spectroscopes. Discoveries were conducted visually and slowly, and resources were limited to observing the surface of an object, but not at all analyzing its composition. [2] 1807 marked the discovery of Vesta by Heinrich Olbers, but Vesta had to wait until 1994 when the Hubble Telescope had the means to look at its complete rotation. [3] In 1891 Max Wolf used photography for the first time to conduct asteroid observations, leading to the discovery of the first NEA (near-earth asteroid), Eros. However, the first proposals to focus on these potential hazardous objects and organize space missions to explore them did not come until the 1970s. In the seventies the development of photometry, radiometry, and spectroscopy contributed to the advances in the field, allowing the discovery of new structural characteristics in asteroids. [4] The beginning of the 1980s brought the Spacewatch program, and marked the use of electronic techniques for asteroid observation, but their hazardous aspect was not to be acknowledged until the 1990s, especially after the impact of the comet Shoemaker-Levi into Jupiter in 1994. [5] Later on, the space probe Dawn entered Vesta’s orbit in July of 2011, in order to answer questions about the origins of the solar system. After orbiting Vesta for a year, Dawn will move on to orbit Ceres for further studies. [6]

The first program dedicated exclusively to the study of the small objects in the solar system started as an idea in 1969 with the decision to build a telescope only for this purpose. Since very few scientists gave importance to this subject, it took years for the project to come into existence. A multi-mirror telescope was used until 1993 when the first Spacewatch 1.8 meter telescope was finally built. [7] The mission of the Spacewatch program was to continue the work done before by using photography, but implementing new technology, using faster detectors and charge-coupled scanning devices (CCD scanning), as well as computer processing. [8]

Obviously, the development of rocket and spacecraft technologies has further led to a revolution in asteroid studies. Missions were designed to have exploration of asteroids as primary goal (NEAR, MUSES-C, Dawn) or as secondary goal (Galileo, Deep Space 1, Stardust). [9] The next goal in space exploration is human landing on an asteroid by 2024. The Near-Earth Asteroid Rendezvous (NEAR) was the first NASA mission studying NEOs, orbiting and landing on an asteroid, providing the best ever taken images of Eros and Mathilde. [10] MUSES-C, a mission of the Japanese Institute of Space and Aeronautical Science, had as primary mission to obtain asteroid samples and return them to Earth. Launched in 2007, Dawn is in search for clues about the formation of the solar system, by visiting Vesta and Ceres. [11] Missions having asteroid research as secondary goal have also brought important contributions in the field. Galileo was the first NASA mission to come close to asteroids, by taking pictures of Gaspra and Ida, as well as discovering Dactyl. [12] Deep Space 1 conducted a flyby of Braille, coming as close as 26 kilometers away from the asteroid, while Stardust encountered Annefrank. [13] Such missions have tremendous contributions to expanding the knowledge and understanding of asteroids, generating huge advances in asteroid studies in the past couple of decades.

The new advances in technology also support the science of astronomy in detecting asteroids and NEOs with impact possibility. This is a crucial step for mitigation. The next step is precise calculation of asteroid orbits which again can be done with accuracy by computers. If deflection is required, the latest rocketry advances and missile encounters are well-founded and ready. In the same time, nuclear methods of deflection are considered to alter the orbit of a hazardous object. The Planetary Society is building its own spacecraft for testing solar sailing, a safer method of nudging an asteroid, and one day, a fleet of such laser spacecraft could orbit Earth and constantly protect the planet from NEOs. [14]

According to the newly released issue of Scientific American Magazine, nobody is actually in charge to save humanity if an impact should occur soon. [15] Prediction is crucial, but telescopes have blind spots, mainly when looking towards the sun, and can miss. To avoid the blind spot issue, a suggestion was to place an infrared asteroid observatory in a Venus-like orbit that could make an inventory of all NEOs. Such a complete inventory would be valid for about a century. [16] This may be the technology of tomorrow in terms of detection and prediction. Deflection however is another story.

The science of asteroid observation has indeed developed tremendously in the past century, and has reached a quite trustworthy level. Earthlings can be confident that possible hazardous objects would be detected before catastrophic impacts. However, there is still work to be done on deflection methods. It all depends on how much time is left to a possible impact. Either way, this field should be a priority of space exploration. After all, if such an impact occurs, there might be no more science or space exploration left to be done by the human species.

 

Notes

[1] Hobden, Heather. Asteroids - their history. http://www.cosmicelk.net/asteroids.htm (Accessed November 16, 2011), para. 1-3.

[2] Jet Propulsion Laboratory. Dawn – A Journey to the Beginning of the Solar System. Modern Era of Asteroid Study. http://dawn.jpl.nasa.gov/dawncommunity/flashbacks/fb_12.pdf (Accessed November 16, 2011), para. 1.

[3] Hobden, Heather. Asteroids - their history. http://www.cosmicelk.net/asteroids.htm (Accessed November 16, 2011), para. 14.

[4] Gehrels, Tom. History of Asteroid Research and Spacewatch. March 9, 1999. http://spacewatch.lpl.arizona.edu/arsw_tg.html (Accessed November 17, 2011), para 1.

[5] Ibid, para. 5.

[6] Hobden, Heather. Asteroids - their history. http://www.cosmicelk.net/asteroids.htm (Accessed November 16, 2011), para. 15.

[7] Gehrels, Tom. History of Asteroid Research and Spacewatch. March 9, 1999. http://spacewatch.lpl.arizona.edu/arsw_tg.html (Accessed November 17, 2011), para 18.

[8] Gehrels, Tom. History of Asteroid Research and Spacewatch. March 9, 1999. http://spacewatch.lpl.arizona.edu/arsw_tg.html (Accessed November 17, 2011), para 20.

[9] Jet Propulsion Laboratory. Dawn – A Journey to the Beginning of the Solar System. Modern Era of Asteroid Study. http://dawn.jpl.nasa.gov/dawncommunity/flashbacks/fb_12.pdf (Accessed November 16, 2011), para. 2.

[10] Ibid, para. 6.

[11] Ibid, para. 9.

[12] Ibid, para. 3.

[13] Ibid, para. 7.

[14] The Planetary Society. Organization’s Official Website. Projects. http://www.planetary.org/programs/list/ (Accessed November 18, 2011), para. 7.

[15] Lu, Edaward T. "Stop the Killer Rocks". (Forum). Scientific American 305, no. 6 (December 2011): 8.

[16] Ibid, 8.

 

Bibliography

Gehrels, Tom. History of Asteroid Research and Spacewatch. March 9, 1999. http://spacewatch.lpl.arizona.edu/arsw_tg.html (Accessed November 16, 2011).

Hobden, Heather. Asteroids - their history. http://www.cosmicelk.net/asteroids.htm (Accessed November 16, 2011).

Jet Propulsion Laboratory. Dawn – A Journey to the Beginning of the Solar System. Modern Era of Asteroid Study. http://dawn.jpl.nasa.gov/dawncommunity/flashbacks/fb_12.pdf (Accessed November 16, 2011).

Lu, Edaward T. "Stop the Killer Rocks". (Forum). Scientific American 305, no. 6 (December 2011).

The Planetary Society. Organization’s Official Website. Projects. http://www.planetary.org/programs/list/ (Accessed November 18, 2011).