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.