§ 1.8 New Asteroids -- Discovering and Cataloging
 Up until the 1980s, asteroids catalogued were discovered accidentally on telescopes' photographic plates, showing up as a small streak. Most astronomers viewed an asteroid streak as a nuisance blemishing an otherwise perfect photographic plate, especially if the asteroid was streaking across the other image of interest to the astronomer. Most such streaks were unreported. (Astronomical observations use time exposure photography, exposing the film to the object in view for long periods of time, which is why the asteroid shows up as a streak. It's actually moving fairly slowly as viewed from Earth.)
In the 1970s and 1980s, electronic sensors started to replace film in certain telescopes, which ushered in the era of automated computer searches for asteroids. First, defense applications started using vidicon cameras to look for the satellites of adversaries (which could easily change their orbit to elude tracking). In defense applications, poring over photographs was a laborious task that left a lot to be desired in terms of thoroughness, fatigue and timeliness. (In fact, in detecting the streaks of adversaries' satellites, many asteroids would show up as a small streak.) Instead of film, this revolutionary new system was an electronic camera using a sensor array combined with computer analysis. It was very simple. A picture was taken of the sky. A few minutes later, another picture was taken, and a few minutes later still another picture. The images were stored in the computer, and as each image additional was taken, the computer would look for anything that moved.
In the 1980s astronomers started using more sensitive "CCD" sensors in cameras. (Soon thereafter, defense telescopes started upgrading.) CCD sensors have proven to be a key to accelerating the discovery of asteroids because it is automated, thorough and very fast -- and CCD sensors are extremely sensitive.
However, viewing an asteroid in one night is not enough to chart its orbit. Also, because of the shoestring budgets for asteroid searches (non-defense work), it is important to understand the physical science and political limitations of the current system. A historical approach can bring this all together.
Determining an asteroid's orbit
In order for an asteroid to be catalogued, we must determine its orbit, and hence there must be at least three viewings to chart its orbital elements, one viewing within a few days after the initial sighting, and another between about two weeks and a month later. Using the data from the second observation to chart a rough orbit, we must find the asteroid a third time to get better precision and thus increase our chances of finding the asteroid many years into the future. If we wait too long, we lose the asteroid. This third viewing usually gives us sufficiently precise orbital data so that we have a better chance of relocating the asteroid at a later date using a reasonable amount of telescope search time.
However, the best telescopes are booked months in advance, some of them years in advance, hence there are no followup viewings of most asteroids. If we wait more than a few days for a second viewing, good chance we won't find the asteroid.
Determining asteroid orbits has not been a highly respected desire in the astronomy and astrophysics communities compared to studying pulsating stars, galaxies, nebula, quasars, etc., which are all surrounded by profound theories. Scheduling a followup observation of a newly discovered asteroid requires fast, diligent efforts. As one veteran astrophysicist put it: "All these activities need to be done within about a month of the discovery, because as the asteroid moves away, it fades in brightness rapidly. Most of the discoveries are made when the asteroid is at its brightest, directly away from the sun [i.e., lined up with Earth and Sun], fully illuminated and closest to Earth." (53) "This usually requires alerting astronomers at other telescopes ... As in other fishing expeditions, the one-that-got-away happens all too often..." (54)
In 1990, just over 2,000 asteroids had been catalogued. Now it's up to about 10,000.
The Earth's atmosphere is a big problem, because the asteroid usually moves across the sky to the horizon in about a month and it's hard to see near the horizon due to the thickness of the atmosphere and the horizon glow from manmade sources. Most asteroids near Earth spend most of their viewable time near the horizon. When the Moon is out, its glare further reduces the detectability of faint asteroids by ground based telescopes, especially near the horizon.
The difficulty with photographic plates
If we are to discover asteroids using a telescope above Earth's orbit where we can look in any direction at any time, we would have to budget and launch up a dedicated telescope for searching for asteroids and studying them. Scheduling time on the Hubble telescope in low Earth orbit would be extremely difficult, as it's booked years in advance by very powerful interests.
The vast majority of asteroids on photographic plates are not even seen for weeks after the plate is taken, partly because they are small, faint streaks and not immediately apparent.
One program, initiated in the mid-1980s by a not-for-profit group called the World Space Foundation, based in Pasadena, California, which included some key people otherwise affiliated with the Jet Propulsion Lab (JPL), and marketed by Dr. Robert Staehle, started a program whereby photographic plates at certain telescopes were examined in microscopic detail almost immediately after they were developed, largely by volunteers, working with the Schmidt telescope at Palomar Observatory in Southern California. However, this program has disappeared from view for various reasons.
An example of the difficulties is illustrated by an effort to "fine tune" the orbits of known asteroids by finding them again and logging their precise position just one additional viewing. Instead of booking future time on a telescope, one researcher calculated where known asteroids should be and reviewed the past 5 year log for a chosen telescope (Mt. Palomar's 48-inch Schmidt telescope) used for other research. He found that 35 of the known asteroids were potentially on 97 plates taken in the past 5 years. However, only 27 of the 97 plates were readily available to him. This reduced the number of asteroids to 10. Then, upon examination of the available film, only 6 of the 10 asteroids were found to be in the region predicted by their catalogued orbital data. Thus, four are lost due to lack of follow-up viewings, whereas six can be found again for many years to come without further viewings.
Another example is worth being aware of: Between 1932 and 1937, three asteroids were noticed and followed up on which were found to have passed within 3 million miles of the Earth. Of these three potentially catastrophic future Earth impactors, two were lost. The other one, named Apollo, was "recovered" only after a long, almost desperate search in 1973. (A whole class of asteroids had previously been named after this one asteroid, Apollo, as covered already, hence the extra effort to find it.)
In the 1980s and 1990s, a few asteroid researchers switched their efforts to building their own telescope to search for asteroids and keep track of them, called Spacewatch, discussed below. This is a good idea that could be copied. Having your own telescope gives you both greater telescope time and the ability to book followup observations instantly. Notably, one can search for small, faint asteroids when the moon is not in the sky to cause atmospheric glow, which is "prime time" when it comes to booking a telescope. Regarding follow-ups, cooperation with other conventional telescopes around the world is a daunting task even though it is a key to "keeping" an asteroid by collecting enough information to know where an asteroid is going in the future.
The smallest asteroid that can be detected by studying film is about 300 meters diameter when passing very close to Earth. However, using state of the art electronic sensors instead of photographic film, new telescopes are increasingly able to detect smaller asteroids at a given distance. Further, electronic sensors allow a computer to do the searching, as opposed to having researchers painstakingly look over film.
Electronic vs. photographic detection
The new method uses digital electronics, not film. The electronic camera automatically scans a section of the sky at different times, separated by around 30 minutes to 2.5 hours. The different star fields are recorded in a computer. The computer compares the images for points of light which have moved. Normally, it requires more than two exposures to distinguish a moving object from the effects of detector noise and cosmic rays. It has also been said that if the asteroid is very close to Earth, it could possibly travel a long enough distance in the sky in too short an amount of time so that there would be a chance it won't be detected, as the two points of light are too far apart on successive images for the computer to see them as related.
The camera uses light-sensitive silicon chip sensors called "charge coupled devices (CCDs)". The state of the art chips as of 1997 can record light 100 times more efficiently than the most sensitive photographic film. Electronic-digital beats chemical-analog in terms of sensitivity, though not in terms of imaging resolution.
The best search time is when the moon is not out. Around full moon, the camera tries to follow up on newly discovered objects. The atmosphere disperses a lot of light, which affects sensitive sensors underneath this "atmospheric ocean".
In the late 1980s, Dr. Tom Gehrels led an institution that organized support for "The Spacewatch Camera", now functioning, located on a 90 centimeter telescope at Kitt Peak, Arizona. It discovers about 20,000 moving objects per year, most of these being Main Belt asteroids, but about 30 per year being near Earth asteroids. A 1.8 meter telescope upgrade will be coming online soon (as of the end of 1998), delayed due to technical problems.
Spacewatch's first contribution was in showing that CCDs were effective at finding NEAs, a concept that some initially opposed in the early 1980s.
After the Spacewatch Camera came online, four asteroids were detected that came closer to the Earth than the Moon (actually, all within half the distance to the Moon) in the period from 1991-1994! The Spacewatch Camera is discovering about 3 NEA's per month and several thousand main belters. In 1998, they received additional funding to upgrade their optical electronics so that they could detect several times more asteroids.
In 1994, Spacewatch was the only telescope to detect an asteroid that passed within 60,000 miles of the Earth, i.e., less than one fourth the distance to the Moon. No other system saw it. If this asteroid had hit Earth, it would have been a major disaster.
Some of these asteroids are also very economically attractive.
The Spacewatch Camera looks into the sky only part of the 24-hour day. There was also a push to create two new Spacewatch Cameras in India and in the Pacific to provide constant coverage of the sky, but that plan was abandoned due to lack of success in raising the necessary funding, and efforts were concentrated on the Arizona Spacewatch facilities.
Other NEO detection programs in the 1990s
In the early 1990s, the Jet Propulsion Laboratory developed the Near Earth Asteroid Tracking (NEAT) system, with principal investigator Dr. Eleanor Helin, the most famous asteroid discoverer to date. The NEAT camera is set up on a 1.0 meter telescope in the crater at the summit of the Mt. Haleakala volcano on the island of Maui, Hawaii, as a part of the U.S. Air Force (USAF) Ground-based Electro-Optical Deep Space Surveillance (GEODSS) program (discussed later in this section). The project is co-sponsored by NASA/JPL and the U.S. Air Force. JPL designed, fabricated, and installed the NEAT camera for mounting upon the Air Force's telescope. The telescope is operated by the Air Force's contractor, PRC, Inc., though it is in effect managed by NASA's JPL under the money strings of NASA's Office for Space Science in Washington, D.C. Anyone on the internet can get an update on the latest asteroid discoveries of NEAT as well as historical data from its inception, thanks to webmaster Dr. Steven H. Pravdo, at http://huey.jpl.nasa.gov/~spravdo/neat.html.
The NEAT camera went online in December, 1995. Even though cloudiness often prevented it from operating at good efficiency, in its first 12 day clear-weather observing run it spotted 2,400 objects, including a comet and four asteroids crossing Earth's orbit. (For comparison, less than 2,000 asteroids had been catalogued in all the time up to the year 1980.) Only a fraction of these 2,400 objects were Earth-crossing asteroids. Enough follow-up observations were performed on 200 of the objects to give them formal asteroid designations, including Earth-crossing asteroids ranging in size between 100 meters and 3 kilometers (1.8 miles) wide. The orbits of these Earth-crossers had been followed up on astronomers in Australia, Japan and the Czech Republic. The orbits were later refined by radar tracking using the Arecibo radar dish in Puerto Rico. (The big Arecibo dish is the first dish in the movie Contact.)
It is expected that the NEAT instrument should be capable of detecting between 50 and 70 asteroids crossing Earth's orbit each month if fully utilized. In comparison, as of 1980, only 47 total Earth crossers were known total (out of 1,800 asteroids total). However, the NEAT instrument has been hindered by lack of an agreement between NASA and the Defense Department (JPL and the Air Force) to guarantee NEAT access to a GEODSS (discussed below) telescope. NEAT has been on hiatus as of the time of this writing (November 1998) as the Air Force has not allowed observations by NEAT for Sept-Oct 1998.
In 1996, NEAT was given 12 nights per month centered around the new moon period for asteroid searches. In 1997, this was reduced to 6 nights per month. Those are Defense Department telescopes with competing demands, despite the end of the Cold War... Weather often reduces the viewing time even further. There was talk of plans to scale up this project to 18 nights per month on 3 Air Force telescopes, but funding decisions were still pending as of late 1998.
It is a goal in the asteroid searching community to detect and map about 80 to 90% of Earth-crossing asteroids of size one kilometer or larger within 10 years. However, the current NEAT and LINEAR (mentioned below) telescopes are not capable of the 10 year, 90% goal without significant upgrades, and funding to support this goal was still elusive as of late 1998.
This goal would not include the much greater numbers of objects less than 1 km in size which are hard to track by a telescope on the surface of the Earth but which would also cause catastrophic impacts if they hit Earth.
Spacewatch and NEAT were each funded at less than a million dollars per year until recently, and it now looks as if they may have topped the one million dollars figure. Most of this funding supports development of new detectors and software for automated sky searches.
Another telescope with great potential to further near Earth asteroid discoveries is called LINEAR, for Lincoln Near Earth Asteroid Research (LINEAR) project, under the direction of the MIT Lincoln Laboratory. It is NASA-funded but exclusively uses Air Force hardware and Air Force contractor personnel. It has two advantages over NEAT: a camera that costs 10-100 times the NEAT camera that was designed for the Air Force but too expensive for the Air Force to use, and it controls its own telescope, typically observing three times longer each month than NEAT.
LINEAR, like NEAT, is riding on the back of the US Space Surveillance network which has been run by the U.S. Air Force since the 1970s. The automated system is called the Ground-based Electro-Optical Deep Space Surveillance (GEODSS). As discussed before, its main purpose was to detect satellites of adversarial nations. In the late 1990s, the effort to modernize this system to CCD cameras was still underway. (paper ref.)
GEODSS has three sites: New Mexico, Korea, and the island of Diego Garcia in the Indian Ocean. How many of these will be upgraded is unknown. Testing of the new LINEAR equipment is conducted at the Experimental Test Site (ETS) telescope at the White Sands Missile Range. The results of testing the new CCD camera on the test GEODSS telescope were excellent (paper ref.). The LINEAR website at http://www.ll.mit.edu/LINEAR maintains current statistics on asteroid discoveries using this telescope. As of October 15, 1998, it had detected 106 confirmed near-Earth objects. This telescope is pictured below.
The GEODSS telescopes are largest asteroid-searching telescopes equipped with 1-meter mirrors which view a 2 sq/deg field of view and collect light for approximately 100 seconds per camera view.
The Spacewatch system, with a 0.9 meter mirror and a 1.8 meter mirror under construction, and upgrades to its CCD camera, may contribute more than LINEAR and NEAT in the long run, since Spacewatch is privately owned and operated. However, we need all the telescopes we can get, and a combined effort to cover as much of the sky as we can.
Another state of the art CCD camera is in the process of being manufactured and assembled by the Lowell Observatory in Flagstaff, Arizona (in the same state as the Spacewatch Camera), called the Lowell Observatory Near Earth Object Search, or LONEOS. LONEOS thinks that it could detect 1000 ECA's within 10 years, and about 2,000 ECA's of less than 1 km diameter. For comparison, LONEOS personnel estimate that there are about 1600 so-called ECAs (Earth-crossing asteroids) larger than 1 km in diameter (of which only about 100 are known).
Still another Arizona based asteroid search program is the Catalina Sky Survey (CSS) using a Schmidt telescope equipped with a CCD camera at the Steward Observatory. It's a relatively small effort, but soon after it started up, it discovered the large Apollo asteroid 1996 JA1 which passed close to the Earth -- about the same distance as the Moon -- in May 1996. Updates on CSS are available at http://www.lpl.arizona.edu/css. As of mid-1998, the telescope was being upgraded, and it was hoped to be back online by the end of the year.
Pictured above is LINEAR, the Air Force telescope under the direction of the MIT Lincoln Lab and some NASA funding. A good feel for its size is given by the front door and the one-level building on the side.
Additional CCD telescope/camera systems are being developed by EUNEASO, the EUropean Near-Earth Asteroids Search Observatories, a cooperation between European observatories and institutes organizing a large-scale NEO search program.
For example, within the framework of the EUNEASO program, there is OCA-DLR Asteroid Survey (O.D.A.S.), a joint venture between the Observatoire de la Cote d'Azur (OCA) of Nice, France, and the German Aerospace Center (DLR) Institute of Planetary Exploration. It operates a 90 cm Schmidt telescope of the OCA at Calern, north of Nice, in southern France, using a 2k CCD camera in combination with an automated asteroid detection software package. It began observations in October 1996 and observes for about 15 nights each month using the weeks of first and last quarter of the Moon. Updates on discoveries are maintained on their webpage at http://pentium.pe.ba.dlr.de/odas/odas.htm
In the Czech Republic is the Klet Observatory, located on top of Klet Mountain in the Alps of Southern Bohemia. This 40 year old, state supported research institute has research projects based on outside grants. It is engaged in discovery of near Earth asteroids and follow-up confirmations, with the latest information available at http://www.ipex.cz/klet The Ondrejov NEO Photometric Program, reachable at http://sunkl.asu.cas.cz/~ppravec has as its main goal "to increase the sample of rotational and shape properties of near-Earth Asteroids. We try to obtain photometric lightcurve observations for each NEA which makes a favorable apparition in the northern celestial hemisphere."
In Canada, "the University of Victoria/ Dominion Astrophysical Observatory near-Earth object astrometry program is designed to provide real-time astrometric confirmation, recovery, and follow-up of newly-discovered Earth approaching objects (comets and asteroids). The program's primary instruments include the 0.5-m reflector and 0.25-m Schmidt Cassegrain telescopes at the Climenhaga Observatory (University of Victoria) and the 1.82-m Plaskett telescope at the Dominion Astrophysical Observatory. All Instruments utilize charge-coupled device (CCD) detectors." Updates and interesting information can be found on the page maintained by Dave Balam at http://astrowww.phys.uvic.ca/~balam. This project is partially funded by the National Research Council of Canada, the National Science Foundation, and FINDS (discussed below).
In China, about 180 km northeast of Beijing, is the Schmidt [kind of telescope] CCD Asteroid Program (SCAD), which is used to discover near Earth asteroids and comets. SCAD is located at the Beijing Astronomical Observatory and is funded by the Chinese Academy of Sciences. Updates can be found at http://vega.bac.pku.edu.cn/~zj/scap/scap.html.
To keep up with major active observational programs all over the world, and hot news, stay tuned to The Near Earth Object (NEO) Page, at http://cfa-www.harvard.edu/iau/NEO/TheNEOPage.html.
Amateur astronomers can help discover asteroids, as well as assist with followup observations of newly discovered asteroids to confirm them and help chart their orbits. Indeed, amateur astronomers are needed around the world. The Japanese amateurs have been remarkably productive.
Indeed, the limitations now seem to be on follow-ups.
All the results from all the survey groups, including discoveries of asteroids, are reported at the end of each night of observing to the Minor Planet Center (MPC) at the Smithsonian Astrophysical Observatory, which is responsible for the collection and dissemination of astrometric observations and orbits for minor planets and comets on behalf of the International Astronomical Union. That information is public domain.
LONEOS estimates that it will probably discover between 5 and 10 potential ECO's (Earth crossing objects) on each full night of observing. "Each of these objects requires several follow-up observations in order to accurately determine the object's orbit. The LONEOS Schmidt could be used to do the follow-up but the number of NEO's discovered will greatly decrease if we must spend the required time in following-up all discoveries." You would need to buy a CCD camera capable of detecting objects of magnitude 17 or greater, and send e-mail to koehn@lowell.edu to get linked into the group communications webpage. If interested in helping (or becoming an amateur astronomer!), one helpful place to get information is TASS (The Amateur Sky Survey).
Followup observations must be done quickly in a decentralized way. A key WWW page is maintained by the aforementioned Minor Planet Center (MPC), called the Near Earth Objects (NEO) Confirmation Page, whereby followup observatories can get the latest information and, after their followup, post their updates. "If objects remain unconfirmed, they will normally be removed (and noted as being lost) five days after the initial posting."
Entrepreneur James Benson jim@spacedev.com announced on June 10, 1997, the Benson Prize for the first 10 amateur astronomers to discover a near Earth asteroid, which awards $500 to each discoverer. The first winner discovered an asteroid 18 days later. Roy Tucker of Tucson, Arizona, using a 14-inch telescope in his backyard, and who had started looking for near Earth objects just the previous month, detected an object moving at 1.1 degrees per day (twice the angular size of the Moon). He reported the position of the asteroid on the two nights to the Minor Planet Center who in turn added it to the NEO Confirmation Page.
Other observers could not find the asteroid at first, which is thought to be due to its faintness, up through Mr. Tucker's third report on its position on July 1. Later that day, Japanese observers reported detecting the asteroid. The Minor Planet Center decided to wait for additional observations before announcing a discovery. Over the next 10 hours, additional observations came from the Czech Republic, Australia, Italy and the USA. By July 2, its orbit was determined and the asteroid was named 1997MW1.
The asteroid is an Aten type (i.e., whose orbit keeps it inside Earth's orbit most of the time), the rarest type of known asteroid. Its size is between roughly 250 and 600 meters across.
This was just the second near-Earth asteroid to be detected by an amateur. Amateurs have been discovering asteroids since the 1970s, initially by photographic means but now by using commercially available CCD cameras. Amateur discoveries of asteroids in the US has lagged behind the Japanese, Italians and English. Teams of amateurs have also been increasingly popular, which should be bolstered by the movies Impact and Armageddon.
Mr. Tucker, 46, is sole proprietor of Southwest Cryostatics, a company offering construction of homebuilt charge-coupled device (CCD) detectors, which is a side hobby/business, as he has a regular job at another company in Tucson, Arizona.
A key to the formal discovery of this asteroid was the precision and accuracy of Mr. Tucker's measurements regarding its position.
A formal account of this discovery is given in a Press Information Sheet by the Harvard-Smithsonian Center for Astrophysics.
Plenty of inspiraton can be found in between the two Arizona asteroid search sites, the LONEOS site in Flagstaff and the Spacewatch site at Kitt Peak, in the form of the Barringer Meteor Crater, a 1.2 km wide crater near Winslow, Arizona caused by the impact of a small, 30 meter asteroid about 40,000 years ago, well preserved by the Arizona desert environment.
Where is Washington, D.C., based NASA funding in all this? Funding for asteroid searches is new to NASA. With government budget cuts and entrenched interests fighting for the shrinking pie, getting funding has not been easy. As discussed elsewhere, there had been several events which have led to Congress pressuring NASA to divert significant funding to asteroid searches, but most of what has come out of it has been cheap workshops culminating in reports whose recommendations have been shelved more or less. (The first workshop was headed by Dr. David Morrison of the NASA Ames Research Center, and the report which came out in 1992. The second was a follow-up study chaired by the late Eugene Shoemaker of the Lowell Observatory, completed in 1995.)
In a bizarre way, the Hollywood movies Impact and Armageddon influenced Congress into pressuring NASA to address the problem, with some results.
The best option - orbital telescopes
Ultimately, the best search device would be a telescope located above Earth's atmosphere, i.e., in orbit. Telescopes on the ground look mainly in the direction away from the sun, of course during the night. Asteroids in orbits within or similar to Earth's orbit would spend the vast majority of their time outside of the range of an Earth-based telescope. A telescope in orbit would allow us to look in any direction. It would also allow viewing 24 hours per day, rather than just nighttime, and would not suffer from the attenuating effects of the Earth's atmosphere or blockage from clouds, nor from the effects of city lights and the Moon (making the Earth's atmosphere glow and drown out faint signals), nor the "horizon glow" of looking through thicker atmosphere when not looking straight up. One could expect that a telescope in Earth orbit dedicating to searching for asteroids near Earth would find them at a rate much faster than a telescope on the ground, and would find smaller asteroids.
A partial analysis of the advantages of a detector above Earth's atmosphere is included in a paper reference by Gregory H. Canavan of Los Alamos National Laboratory. With the aim of detecting asteroids and comets, Canavan discusses "improvements in ground- and space-based search sensors and strategies that could provide adequate search capability and derives their search, detection and completeness rates. It also discusses cost-optimized combinations appropriate for both long- and short-warning threats."
Asteroid searches are also biased because asteroids are easiest to detect when they are lined up with the Earth and the Sun, and hence brightest -- similar to the "full moon", they are "full asteroid". If they don't happen to pass by in that way, but are seen in a phase (e.g., "half asteroid", analogous to half moon vs. full moon), they are less likely to be detected. This makes small asteroids as well as dark volatile rich asteroids even harder to detect.
Infra-red vs. visible light telescopes
One solution is an infra-red telescope, to detect asteroids by their heat. This method does not depend upon reflected sunlight, only heat radiated by the asteroid. The one big problem is that such a detector must be placed in orbit, above the atmosphere.
In 1983, the Infra-Red Astronomical Satellite was launched into low Earth orbit. It was in orbit for less than a year, but provided almost all our useful infrared observational data on near Earth asteroids and comets. Indeed, the IRAS data was not analyzed to discover unknown asteroids, and if that data were reanalyzed, we would probably add quite a few new asteroid discoveries to our catalogs.
The planned Space Infra-Red Telescope Facility (SIRTF) is also of great potential use in searching for near Earth asteroids, as well as having an infrared spectrograph which would help characterize asteroid surface minerology. However, it is heavily booked throughout its lifetime by other interests. It would be better to order a second copy of this telescope and dedicate it to an asteroid search and spectroscopic analyses. Of course, a second copy would cost substantially less than the first, once the design process is finished and the manufacturing facility is set up for the first.
There is a page on converting Star Wars telescope materials into a space-based telescope.
The Spaceguard Foundation is an international group formed at a conference in Rome in 1996 with the purpose of helping to protect Earth from asteroid impacts by promoting and coordinating discovery programs, as well as research of near-Earth asteroids.
|
Discovering
Back to 
Forward to