NEO Coordination Centre

 

Precursor services

 

Please note that all SSA-NEO Services are under development

Last update: 2014-10-25 13:12:00 UTC
Current number of known NEOs:
11513
Current number of NEOs in risk list:
453

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Lost NEOs (part 2): how to find them… online!
 
02 Oct 2014
 
CFHT
 
The Canada-France-Hawaii Telescope on Mauna Kea, Hawaii. The images of 2008 CK70 taken used for the precovery discussed in the text were taken with this telescope, and located thanks to the Solar System Object Image Search tool of the Canadian Astronomy Data Centre. (Image credit: M. Micheli)
 
 
This post discusses a second component of our observational effort at the NEO Coordination Centre.
 
After discussing what to do to ensure that an important NEO is adequately monitored, we will now present a possible strategy to improve the orbit of old objects, that have not been properly observed in the past.
 
In the previous story we talked about how a large fraction of near-Earth objects are effectively lost. This term means that, even if they were discovered and observed in the past, our knowledge of their orbit is not sufficient to allow us to find them again with a telescope the next time they will become observable. This is clearly a concern particularly for the ones that have possible future collisions, because it prevents us from getting additional observations. These observations would be needed to refine the knowledge of their future trajectory to a level sufficient to exclude them from the risk list of dangerous asteroids.
 
We already discussed the cases where an object can be monitored or recovered with existing optical telescopes, either because it has been discovered recently, or because the uncertainty of its position is not too large. But what can we do if neither option is available?
 
Fortunately, there is a possibility. Every night, all over the planet, there are dozens of large professional telescopes observing the sky. Some of them may be taking very specific data on individual targets (e.g. performing spectroscopy, polarimetry, or using so-called adaptive optics to obtain high-resolution image data).  However, a large fraction will likely be operating in the most basic mode of astronomical observations of our time, namely taking images of a section of the sky with a digital camera. The goals of these observations can be very diverse, ranging from extragalactic astronomy to stellar astrophysics or cosmology, but the final product will often be the same: images of the sky taken in a particular filter, and with a given exposure time. After these images have been analyzed by the scientists requesting them, they are often made available to the public on the telescope's website. From there, anybody can download them for whatever additional purpose. 
 
However, there is a high chance that nobody paid attention to asteroids which may be visible in the field. If we have access to these large archives, with a tool which is capable of identifying the appropriate frames, then we may have a chance to find additional observations of an asteroid taken when the object was not yet lost. If that's the case we may be able to locate it, use these data to extend the observed arc, and "save" the object from getting lost. In other cases, these additional observations may at least be sufficient to determine that the object is not a danger for our planet, which is already an important result. This process is called "precovery", a combination of the word "recovery" and the prefix "pre", to suggest that it is based on existing data, and not on new images.
 
An interesting example of it is represented by an object precovered by our team a few months ago. Found in February 2008 and named 2008 CK70, it was at the time considered as one of the most dangerous known NEOs. It would have multiple chances of impact starting from the year 2079. Unfortunately, the available observations had all been obtained on only five days around the time of discovery, an arc far too short to successfully extrapolate its position to the current time, more than 6 years later. It was therefore effectively considered a lost object, and would probably have remained in such a state until somebody had rediscovered it by chance.
 
However, after a search in the databases of some large telescopes, we noticed a set of images taken by the Canada-France-Hawaii Telescope (CFHT) in Hawaii. These were taken almost one month before the object had been discovered and covered the area where the object could be. An accurate inspection of the frames allowed us to locate the asteroid, which was extremely faint (magnitude 24.5) at that time, but nevertheless clearly visible in the exposures thanks to the large aperture of the telescope and excellent sky quality of the site. We could accurately measure its position, and add this information to the orbital determination. The resulting significant improvement was sufficient to exclude all possible future impacts for the next century. At the same time it reduced the uncertainty of the sky position for the object to a level small enough to make it recoverable the next time it will come close to the Earth, in 2017.
 
2008 CK70
 
An animation of 2008 CK70 as seen in the precovery frames from CFHT. Can you spot the moving asteroid? Hint: it is very faint, but near the centre. (Image credit: CFHT Legacy Survey)
 
 
The chance of finding a situation like this, with good images taken at the right time with the right telescope, may not seem large. But, given the number of professional observatories in the world, it is still significant.  Over the past few months we were able to locate precovery observations for at least a dozen asteroids with non-zero impact probability with Earth. For most of them, this resulted in either a reduction of their impact probability or a total removal of the object from the risk list.
 
Moreover, with the increase of the number of survey telescopes that scan the sky every night, such as the Catalina Sky Survey, or the Pan-STARRS project, the number of exposures available to look for new data is growing fast. And, even if these survey telescopes are designed to look for asteroids, and their images are carefully searched for anything that moves, there is still a chance that something may have been missed. This is especially true if the object is faint, or slow. This is the reason why we need to keep looking into these archives, and why every telescope, big or small, at professional or amateur level, should consider making their data available to the community. You never know what may be hidden in your images, until you look at them from the right perspective!
 
References:
 
A more formal discussion of the follow-up and precovery efforts organized by the NEOCC can be found in an abstract presented at the ACM 2014 conference held last month in Helsinki (http://www.helsinki.fi/acm2014/pdf-material/Day-2/Session-4/Room-3/MICHELI-C4C2.pdf), and in a related paper soon to be published in the journal "Earth, Moon, and Planets" (http://link.springer.com/article/10.1007/s11038-014-9441-y).

ESA's bug-eyed telescope to spot risky asteroids

22 Sep 2014

Situational awareness

Spotting Earth-threatening asteroids is tough partly because the sky is so big. But insects offer an answer, since they figured out long ago how to look in many directions at once.
 
As part of the global effort to hunt out risky celestial objects such as asteroids and comets, ESA is developing an automated telescope for nightly sky surveys.
 
This telescope is the first in a future network that would completely scan the sky and automatically identify possible new near-Earth objects, or NEOs, for follow up and later checking by human researchers.
 
But a web of traditional telescopes would be complex and expensive because of the number required. Adding to the problem, the system must be able to discover objects many times fainter than the naked eye can perceive.
 
While no network can spot all potentially hazardous objects, under favourable conditions it should detect everything down to about 40 m in diameter at least three weeks before impact.
 
Fly-eye Telescope
 
One telescope, 16 lenses
 
The answer is a new, European telescope nicknamed ‘fly-eye' that splits the image into 16 smaller subimages to expand the field of view, similar to the technique exploited by a fly's compound eye.
 
The design is modular, and allows for mass and cheaper production and lower maintenance costs. It will be used to build the prototype, to be fielded by ESA's Space Situational Awareness (SSA) programme early next year.
 
"This novel technology is key to the future NEO survey network," says Gian Maria Pinna of the SSA office.
 
Performance equivalent to large telescope
These fly-eyed survey telescopes offer performance equivalent to a 1 m-diameter telescope, and provide a very large field of view: 6.7° x 6.7° or about 45 square degrees; 6.7° is about 13 times the diameter of the Moon as seen from the Earth.
 
"The new telescopes would provide the resolution necessary to determine the orbits of any detected objects," says Gian Maria Pinna.
 
 
 
 
"If the prototype confirms the expected performance, it will pave the way to full procurement and deployment of the operational network of telescopes."
 
This summer, ESA signed a contract for about €1 million with a consortium led by CGS S.p.A (Italy), comprising Creotech Instruments S.A. (Poland), SC EnviroScopY SRL (Romania) and Pro Optica S.A. (Romania) for the detailed design of the advanced telescope.
 
It is expected that the detailed design will be followed by several additional contracts with European companies valued at up to €10 million for building and deploying the first survey prototype telescope.
 
"The development of the first optical sensor specific to ESA's NEO search and discovery activities is a fundamental step toward Europe's contribution to safeguarding our planet from possible collisions by dangerous objects," notes Nicolas Bobrinsky, Head of the SSA Programme.

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Lost NEOs (part 1): how to find them in the sky

 

15 Sep 2014

2014 DN112

A star field containing the near-Earth asteroid 2014 DN112, imaged by the ESO Very Large Telescope in Chile in March 2014. (Image credit: ESA/ESO)

The observational component of NEO science is an extremely important part of the impact mitigation effort, since observations are the input data for all the computational models used to predict future collisions. This post will summarize our effort to ensure that enough data are obtained, especially on the most important and challenging objects, during the short time when they are observable.

At the top of this page there is a counter with the number of objects in the current NEO risk list (their names and details are accessible via the "Risk Page" menu to the left). These are the most important objects to study if you are interested in the danger that asteroids can pose to our planet. This is because they have a non-zero chance of colliding with it over the next century.

However, only a small fraction of them are observable at any given time. And there is more: If you want to point a telescope and collect more data on any of them, you need to know precisely where they are in the sky. In most cases that is a big problem. Of all the known objects which could possibly impact the Earth in the future, approximately 90 % are lost again. This means that the next time they will come close enough to be observable from Earth, we will not know where they will be in the sky. This is  because the uncertainty with which their future position is known increases dramatically with time.

How can we address this problem? There are basically two approaches: we should first do our best to prevent the newly discovered NEOs from getting lost by collecting additional observations to improve the orbit determination process. Secondly, we should make an effort to "recover" some of the old objects the next time they come back, even if their position in the sky is poorly constrained. Because of the importance of these problems, ESA's NEO Coordination Centre organizes a systematic effort to involve multiple observatories and astronomers, in Europe and all over the world, in observing these dangerous asteroids.

Let us start with the most direct way of changing this situation of lost asteroids. On average, one new NEO is discovered every 8 hours. Most of them are found when they are close to us, quite bright and easy to see. Therefore many observations are performed around the time of discovery, both by professional and amateur astronomers worldwide. However, within a few weeks, the objects start receding from the Earth, becoming progressively fainter. When this happens it becomes very likely that no additional data will be obtained, because larger telescopes would be needed. It is not easy to obtain access to these, especially on short notice. This, in turn, means that no additional information may become available, and our evaluation of the danger of the object will not improve anytime soon.

To address this problem, we have or are developing agreements with various professional telescopes, including the ESO Very Large Telescope (VLT) in Chile. The VLT, with its 8.2 meter primary mirror, is one of the most powerful telescopes on the planet. It can easily detect asteroids down to magnitude 26, 100 times fainter than what even the most advanced amateur astronomers can do. Over the last six months we have obtained observations of about 15 such objects. For most of them our detections were sufficient to either clarify that they will not hit the Earth anytime soon, or at least ensure that we will be able to observe them again the next time they come close to the Earth.. Without our observations, most of them would have become new entries in the list of lost objects.

animation of our VLT images of 2014 GY44

An animation of two VLT images of 2014 GY44, when it had a visual magnitude of approximately 26. The object is the faint round dot moving diagonally between the two frames. The stars in the image appear as long trails, because the telescope was moving following the expected motion of the asteroid in the sky. (Image credit: ESA/ESO)

2014GY44 OVT

Plot of the relative position of 2014 GY44 and the inner planets at the time of the VLT observation (1 May 2014), generated using the ESA Orbit Visualization Tool (accessible via this website). The object has an estimated diameter of only 50 meters in diameter and was already more than 36 million kilometers away from Earth. (Image credit: ESA)

But what can we do when the problem arises from a large uncertainty in their position? If the area of the sky where they can be found is reasonably small, say up to a few degrees in size, one can attempt to use telescopes with a large field of view. These can image a significant fraction of this sky area in a short time, with multiple exposures. The object will likely be visible somewhere in these images. If we can locate it we can then measure its position and improve the orbit enough to make it observable again for years to come. This process, called "recovery", is another one of the goals we are  pursuing from the NEOCC, with the help of many cooperating observatories*.

Animation of our VLT images of 2012 HP13

An animation of our VLT images of 2012 HP13, an NEO with a large uncertainty that we recovered two years after its discovery. The moving object at the center of the frame is a real asteroid, but it was not the target of our search. Can you spot the fainter one (which is the NEO we were looking for)? Hint: it is fainter than the central one, and near the bottom of the frame. (Image credit: ESA/ESO)

Unfortunately, there are some objects which are now too faint and too far to observe with even the most powerful telescopes on Earth. Next time they will become bright enough to see, their uncertainties will be huge, too large for even the largest cameras in the world. Some of them, such as the large asteroid 1979 XB, are so hopelessly lost that at their next apparition they can literally be anywhere in the sky!

Fortunately, at least in some cases, there is a way out. More on this in our next story… stay tuned!

 

*If you have access to a large telescope (anything that can reach magnitude 21 or fainter), and want to collaborate with us, please let us know.

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2014 RC - a close fly-by coming up
 
04 Sep 2014
 
 
In the evening of 07 September 2014, the newly discovered asteroid 2014 RC will have a very close fly-by of just above 30000 km to our planet. The object is estimated to be between 10 and 30 m in size. While the fly-by is very close, there is no chance that the object will hit the Earth.
 
2014 RC was announced as a newly discovered object by the Minor Planet Center in the US on 02 September 2014. Its fly-by velocity will be fairly slow, just around 11 km per second. The European NEODyS system finds a nominal fly-by distance to the Earth's surface of 33587 km, which is just inside the geostationary ring.
 
The close approach time will be between 18:00 and 18:15 UTC on 07 September 2014 (Update: the revised close approach time was 18:02 UTC).
The object will reach a magnitude of 11 which would make it in principle observable with a pair of binoculars or a small telescope. Unfortunately the object will not be visible over Europe.
 
This object is comparable in size to the object that entered the Earth's atmosphere over Chelyabinsk in Russia on 15 February 2013. Luckily it will fly by our planet safely.

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Happy Birthday NEOCC!

 

22 May 2014

AZT-24 Telescope at Campo Imperatore Observing Station

The AZT-24 Telescope at Campo Imperatore Station used for infrared observations of NEAs. (Image credit: INAF)

Today the NEO Coordination Centre (NEOCC) celebrates its first year of activities. On 22 May 2013 the Centre was formally inaugurated at ESRIN by Thomas Reiter, ESA Director of Human Spaceflight and Operations.
Since then, the Centre has regularly provided information and data on NEOs through its main services updated on a daily basis (Risk list, Priority list, Close Approaches and Physical Properties) and through its technical news service.

In addition, several campaigns for astrometric and physical observations of NEAs have been organized and successfully completed. A network of collaborating observatories has been created.

A good example for an astrometric and physical observation campaign was the case of 2013 QW1, a candidate NEO in an Earth-bound orbit whose nature, either natural or artificial, needed to be quickly determined. An observing alert triggered by the NEOCC resulted in rapid spectroscopic observations from the 3.5-metre Italian Telescopio Nazionale Galileo (TNG) in the Canary Islands, which contributed to exclude that 2013 QW1 was  a natural object because of the "artificial" appearance of its reflectance spectrum. We acknowledge Davide Perna, Antonella Barucci (Observatoire de Paris Meudon) and Elisabetta Dotto (INAF – Osservatorio di Roma) for having responded to our call.

The observing campaign of 2002 GT fits along the second type of activities done by the NEOCC, namely to coordinate observations. The observing campaign was organised by the Centre to characterise the target selected for the NASA EPOXI (formerly Deep Impact) mission during its last apparition before the then planned encounter with the spacecraft. A large community promptly responded: photometric and light-curve observations were performed from the 1-metre diameter C2PU telescope at the Observatoire de la Cote d'Azur, which allowed the calculation of the rotation period of the object (3.77 hours). Spectra and photometric data were collected from the Asiago Observatory (University of Padova and Observatory of Padova) allowing the determination of the asteroid type (Sq); infrared observations were provided from the Campo Imperatore Station of the INAF Rome Astronomical Observatory. Finally, several astrometric measurements were provided by six telescopes belonging to the Gaia Follow-up Network for Solar System objects (Gaia-FUN-SSO).
 

Deep Impact Launch

Deep Impact lifts off from pad 17-B at Cape Canaveral Air Force Station, Fla., bound for Comet Tempel 1. (Image credit: NASA/KSC)

Building up on these early experiences, a framework agreement with ESO's Very Large Telescope (VLT) has been established, which has allowed the Centre to start a focused observational effort to obtain astrometric observations of high-risk objects. This collaboration allowed the NEOCC team to obtain critical observations of almost a dozen dangerous objects, which in most cases led to their removal from the list of possible future impactors; a few recent examples have been the early recovery of 2009 FD (currently the highest-rated known possible impactor) and the challenging follow-up observations of 2014 AF16.

The regular availability of the ESA Optical Ground Station (OGS) Telescope for ESA's NEO programme turned out to be extremely useful to perform routine observations of newly discovered objects, with a specific focus on the urgent targets suggested by the NEOCC Priority List.
 

ESA OGS Telescope

The ESA Optical Ground Station (OGS).  (Image credit: ESA)

The Centre keeps growing. The technical and scientific team behind the NEOCC is working on the implementation of new services and on the improvement of the existing ones, which will be soon available.  Meanwhile, a well-timed gift is already on the way for celebrating the second birthday of the NEOCC: the 4th IAA Planetary Defence Conference will be hosted at ESA/ESRIN on 13 - 17 April 2015. See you then!


External links:

ESA/ESO Collaboration Successfully Tracks Its First Potentially Threatening Near-Earth Object. ESO Announcement, 21 January 2014. http://www.eso.org/public/announcements/ann14004/
 
Target Asteroid Tracked by European Teams. ESA SSA News, 18 July 2013. http://www.esa.int/Our_Activities/Operations/Space_Situational_Awareness/Target_asteroid_tracked_by_European_teams
 
Space Oddity: The Mystery of 2013 QW1. ESA SSA News, 19 September 2013. http://www.esa.int/Our_Activities/Operations/Space_Situational_Awareness/Space_oddity_the_mystery_of_2013_QW1

Publications related to NEOCC activities:

E. Perozzi, D. Koschny, R. Dominguez-Gonzalez, G. Drolshagen, N. Sanchez-Ortiz. The SSA NEO Segment and Gaia: present opportunities and future developments. In proc. ‘2nd Gaia-Follow-Up Network for Solar System Objects'. P. Tanga and W. Thuillot eds. IMCCE/Observatoire de Paris, 2013.

E. Perozzi. The Near Earth Object Hazard and Mitigation. In proc. ‘Mathematical Methods for Planet Earth'.A. Celletti, U. Locatelli, E. Strickland eds, Springer. 2013 (in press).

E. Perozzi, F. Bernardi, A. Milani, G.B. Valsecchi. "Vicini ma non troppo". Le Scienze, July 2013.
 
E. Perozzi, F. Bernardi, E. Foschi, G. Drolshagen, D. Koschny, G.B. Valsecchi: Observing small and accessible NEOs: the importance of newly discovered objects. Stardust Virtual Workshop, Glasgow 6-9 May 2014.
 

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A good year to find a comet

 

12 February 2014
 
Comet P/2014 C1 seen from Argentina
 
Comet P/2014 C1 seen from Argentina's Pierre Auger Observatory on 4 February 2014 (Image credit: FRAM/GLORIA/Martin Masek)
 
A team of European astronomers has found a previously unknown comet, detected as a tiny blob of light orbiting our Sun deep in the Solar System.
 
The comet was unexpectedly discovered on 1 February during a routine set of observations using the 1 m-diameter telescope at ESA's Optical Ground Station, Tenerife, Spain.
 
The confirmation was announced by the International Astronomical Union's Minor Planet Center, the international clearing house for all such discoveries, on 4 February, after eight other observatories confirmed the sighting.
 
The tiny object is extremely faint, and its orbit was determined to lie between Jupiter and Mars – it will not come close to Earth.
 
Comet year
 
"All comets are interesting especially as they are thought to have played a role in bringing water to Earth in the distant past," says Detlef Koschny, responsible for near-Earth object (NEO) activities at ESA's Space Situational Awareness (SSA) programme office.
 
 
Orbit of comet P/2014 C1 TOTAS
 
Orbit of comet P/2014 C1 TOTAS (Image credit: TOTAS) 
 
"Later this year, Rosetta will meet up with another comet, 67P/Churyumov–Gerasimenko, and study its nucleus and surrounding gas and dust, so it's especially fitting that a European team has found a new comet this year."
 
This latest discovery was, in fact, made by software, which compares successive images to find ‘movers' – objects that move against the star field background. The find was confirmed by Rafal Reszelewski, working as part of the team to verify possible new objects automatically flagged by the  software.
 
Since 2010, the TOTAS team has been working in collaboration with ESA's SSA office to conduct periodic sky surveys to find and confirm asteroids and other NEOs that orbit close to Earth. In 2011, it found asteroid 2011 SF108, which does orbit much closer to Earth.
 
 

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TOTAS survey finds its first comet

 

6 January 2014

In a fruitful collaboration between ESA and a group of amateur astronomers, the first comet was discovered by the so-called TOTAS survey. The comet is called P/2014 C1 (TOTAS) and has an orbit between Jupiter and Mars.

TOTAS stands for 'Tenerife Observatory Teide Asteroid Survey'. The survey name is derived from the name SOHAS = Starkenburg Observatory Heppenheim Asteroid Survey. SOHAS was initiated by M. Busch, a software developer and active amateur astronomer at the public observatory in Heppenheim, Germany (called Starkenburg-Sternwarte). Already in 2009, M. Busch adapted his telescope control and asteroid search software to work with the 1-m telescope of ESA on Tenerife, the Optical Ground Station, and renamed it TOTAS.

When the SSA-NEO programme learned about this, a long and fruitful collaboration started in March 2010. During a survey test campaign very close to the morning horizon on 01 February 2014, the automatic processing software picked up a special object. R. Reszelewski, one of the team of amateur astronomers who check the images generated by the computer software, was the first to detect the cometary nature
(Figure 1).

 

Image of Comet P/2014 C1 (TOTAS)

Figure 1: Animation of the comet (Image credit: TOTAS/ESA)

The observations were immediately submitted to the Minor Planet Center. On 04 February, after confirming messages of eight other observatories securing the orbit, the Minor Planet Center announced the discovery of comet TOTAS (http://www.minorplanetcenter.net/mpec/K14/K14C11.html).

The comet orbits the Sun between Jupiter and Mars and will not come close to the Earth. Its orbit is shown in Figure 2.

 

Comet P/2014 C1 (TOTAS) orbit

Figure 2: Comet P/2014 C1 (TOTAS) orbit (Image credit: M. Bush/EasySky)

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Getting ready for asteroids

 

31 January 2014
 
 
Asteroids passing Earth 
 
With a mandate from the UN, ESA and other space agencies from around the world are about to establish a high-level group to help coordinate global response should a threatening asteroid ever be found heading towards Earth.
 
For the first time, national space agencies from North and South America, Europe, Asia and Africa will establish an expert group aimed at getting the world's space-faring nations on the ‘same page' when it comes to reacting to asteroid threats.
 
Its task is to coordinate expertise and capabilities for missions aimed at countering asteroids that might one day strike Earth.
 
Of the more than 600 000 known asteroids in our Solar System, more than 10 000 are classified as near-Earth objects, or NEOs, because their orbits bring them relatively close to our path.
 
 
Asteroid trace over Chelyabinsk
 
Dramatic proof that any of these can strike Earth came on 15 February 2013, when an unknown object thought to be 17–20 m in diameter arrived at 66 000 km/h and exploded high above Chelyabinsk, Russia, with 20–30 times the energy of the Hiroshima atomic bomb.
 
The resulting shock wave caused widespread damage and injuries, making it the largest known natural object to have entered the atmosphere since the 1908 Tunguska event, which destroyed a remote forest area of Siberia.
 
Coordinating global efforts
 
The Space Mission Planning and Advisory Group (SMPAG – pronounced ‘same page') was established by Action Team 14, a technical forum with a mandate from the UN Committee on the Peaceful Uses of Outer Space (UNCOPUOS) to develop a strategy on how to react on a possible asteroid impact threat.
 
It will coordinate the technological knowhow of agencies to recommend specific efforts related to asteroid threats, including basic research and development, impact mitigation measures and deflection missions.
 
 
Control room of ESA's observatory on Tenerife
 
"SMPAG will also develop and refine a set of reference missions that could be individually or cooperatively flown to intercept an asteroid," says Detlef Koschny, Head of the NEO Segment in ESA's Space Situational Awareness (SSA) programme office.
 
"These include precursor missions or test and evaluation missions, which we need to fly to prove technology before a real threat arises."
 
The first-ever meeting will be hosted by ESA on 6–7 February at its operations centre in Darmstadt, Germany.
 
Thirty-plus representatives from 13 agencies, seven government ministries and the UN will share knowledge and the latest research related to impact case studies, and will develop a work plan for the next two years.
 
"As a first step, the group will study each agency's organisational and operational capabilities, specific technologies and scientific abilities, and propose options that make best use of who can do what, the best," says Detlef.
 
 
ESA Space Situational Awareness: detecting space hazards
 
The group will work in close cooperation with another Action Team 14-mandated committee: the International Asteroid Warning Network (IAWN).
 
Each will study and recommend specific actions to deal with different aspects of the asteroid threat – IAWN to coordinate the global search for threatening NEOs, understand their effects in case of a collision, and interface with disaster preparation and civil response agencies; and SMPAG for the technology and space mission aspects.
 
Current threats, future scenarios
 
The critical first step is to spot potential threats in the sky with as much advance warning as possible.
 
"ESA is already doing a great deal to support the global effort to address the asteroid threat," says Nicolas Bobrinsky, ESA's SSA Programme Manager.
 
The Agency is now developing the capability to integrate Europe's current NEO tracking assets – as well as new technology such as automated, wide-field-of-view telescopes – into a coordinated and more efficient NEO system that can provide nightly sky surveys and advanced warnings.
 
Among other recent developments, starting in late 2013, ESA will make use of observing time at the European Southern Observatory in Chile to conduct quick and accurate confirmations of the most hazardous NEOs.
 

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The Recovery of 2009 FD, a Potentially Hazardous Asteroid

 

21 January 2014

VLT Telescopes

The VLT telescopes on the Paranal mountain in Chile (credit: ESO).

The first recovery campaign carried out by the ESA NEO Coordination Centre in coordination with ESO, using the Very Large Telescope (VLT) turned out to be a success. Before the campaign, asteroid 2009 FD was ranked among the top five objects in the risk list. Now the associated value on the so-called Palermo scale (http://neo.jpl.nasa.gov/risk/doc/palermo.html) has dropped by almost a factor of ten to a value of -2.6 (from -1.8 on the logarithmic scale).

The observations were performed by a team including Olivier Hainaut (ESO), Detlef Koschny (ESA), and Marco Micheli (NEOCC team, ESA/Serco), with the FORS2 camera on the 8.2-meter VLT telescope on Cerro Paranal in Chile. Images of the area of the sky where the object was located were obtained on five different nights, between 30 November and 5 December 2013.

It was a challenging recovery. Although it was possible in the first night to locate the asteroid position with good accuracy, the following two nights the observing conditions were worse. The faint "clump of pixels" indicating the position of 2009 FD was still detectable but the quality of the astrometric data degraded. In the following nights bad seeing and technical reasons prevented further improvements. Nevertheless, a detailed re-examination of the data resulted in good-quality astrometric data which has been accepted by the Minor Planet Center, the central clearing house for asteroid astrometry. The object's observations were finally taken into account in their 'daily orbit update' of 11 December 2013.

Screenshot of asteroid 2009 FD, at a magnitude of ~24.

Both the European NEODyS system and the JPL-based Sentry system performed orbit determination and impact monitoring using the new observations. These computations showed that there are still some low-probability impact solutions, ranging from the years 2185 to 2198. Yet they are likely to disappear within the next few months, when 2009 FD will become progressively brighter, peaking at a magnitude of V=19 in mid-March 2014, thus ensuring a proper astrometric coverage.

The successful recovery of 2009 FD shows that having access to a large telescope such as the VLT is a great opportunity for the NEO Coordination Centre, since it gives a chance to obtain astrometric observations of very faint objects (down to visual magnitude 25.5) which only very few people and instruments in the world can do.  

Links:

Palermo scale: http://neo.jpl.nasa.gov/risk/doc/palermo.html

The Very Large Telescope: http://www.eso.org/public/teles-instr/vlt/

ESA's SSA-NEO Coordination Centre: http://www.esa.int/Our_Activities/Operations/Space_Situational_Awareness/About_SSA-NEO_Coordination_Centre

European Southern Observatory: http://www.eso.org

ESA/ESO Collaboration Successfully Tracks Its First Potentially Threatening Near-Earth Object: http://www.eso.org/public/announcements/ann14004/

 

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Observing 2013 NJ: A study case

 

4 December 2013

Pan-STARRS of 2013 NJ
 
Discovery images of 2013 NJ, obtained on 1 July 2013 by the NASA-funded Pan-STARRS telescope in Hawaii.
 
If an asteroid is discovered which could come very close to Earth, it is important to coordinate observational activities quickly to better know its precise flyby distance.This is illustrated by the following case of near-Earth asteroid (NEA) 2013 NJ.
 
2013 NJ is a 100-meter class object (absolute magnitude H = 22) discovered in early July 2013. It had a close encounter with the Earth on 26 November 2013, 1 million kilometers away from our planet. Even if the object was carefully tracked by observers around the time of discovery, its observational geometry then kept it close to the Sun for the past few months, making it unobservable from the ground until after its current close encounter with the Earth.
 
As a result, when the object became observable a few days ago from the Southern hemisphere, its position in the sky was poorly known. Without immediate additional astrometric observations the asteroid position in the sky would not have been constrained enough to allow pointing narrow-field instruments devoted to physical characterization (i.e. spectrometers, polarimeters) to the asteroid. Luckily, with a peak visual magnitude of 14 this object was bright enough to be easily reobserved even with small telescopes. It was actually recovered from Cerro Tololo in Chile, less than 24 hours after its close approach, providing the astrometric information needed to significantly improve its orbit and predict its path in the sky for the following days. But what would have happened if 2013 NJ were a much smaller object?
 
Things would not have proceeded as smoothly as they did. Such an asteroid would have been at risk of being lost, unless the object would have been recovered when still on the southern hemisphere - difficult, as there are not so many telescopes there. Physical characterization needed also to be planned in a timely manner and attempted quickly. The asteroid would be going through a much fainter magnitude range, thus implying more demanding observational requirements in terms of time scale and telescope performances.
 
This "study case" scenario demonstrates that a quick coordinated response, able to ensure challenging astrometric and physical follow-up of small objects, is essential for the future developments of NEA research and mitigation. Even more since the US and European NEO space programmes are increasingly focused on small accessible asteroids, which are likely to be discovered in circumstances resembling that of 2013 NJ, forcing astronomers to react on short timescales and organize their observations during very short visibility windows.
 

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2013TV135 UPDATE. NO LONGER IN THE IMPACT RISK LIST

 

09 November 2013

On 8 November 2013 asteroid 2013TV135 has been removed from the Risk Page. The non-zero impact probability spotted by monitoring systems just after its discovery (on 8 October 2013) dropped essentially to zero. The bulk of astrometric data collected by astronomers during exactly one month of observations helped to improve our knowledge of its orbit, that eventually turned out to be a safe one.

With respect to the impact monitoring analysis, the case of 2013TV135 is a very typical one. Statistically speaking, almost every NEA initially found to have non-zero impact probability will eventually turn out to be actually safe for the Earth. And this is even more true for the bigger ones.

Every time new astrometric data become available from observations, the characterization of the asteroid orbit improves and the estimated impact probability is re-computed. This may happen in the days, weeks, months or even years following the discovery date, depending on the availability of observational data.

A typical pattern is that as the orbit becomes more precisely determined, impact probability often increases initially, or shows a quite erratic behaviour (see, for instance, the table in "2013TV135, A newly discovered object at the top of the impact risk list"), but then decreases until it falls to zero, or some very low number. This is exactly what happened with 2013TV135.

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2013TV135, A NEWLY DISCOVERED OBJECT AT THE TOP OF THE IMPACT RISK LIST

 

23 October 2013

Crimean Astrophysical Observatory

Crimean Astrophysical Observatory (Credit: Wikipedia)

Soon after having been spotted in the sky on 8 October 2013 from the Crimean Astrophysical Observatory (Ukraine), asteroid 2013TV135 topped the Risk Page.

Being a relatively large object (500 m in size) it quickly gained the headline news having ramped up the Palermo Scale value for a possible impact in August 2032.

The object has an absolute magnitude of 19.6 and it is currently easily observable. Although the many observations performed worldwide for orbit improvement, the impact probability and Palermo Scale continue to change with no clear pattern.

"We need more data, and also higher quality data with very accurate astrometry; we do not need too many observations, 3-5 observations per night is optimal" suggests Andrea Milani, on behalf of the NEODyS consortium.

Additional information can be extracted from the past history of 2013TV135: computing backwards ephemeris one notices that its brightness peaked at about 16th magnitude in mid-September, well before discovery, when it was observable from the southern hemisphere. Uncertainty analysis reveals that were the object first spotted at that time, its orbit would have been quickly well constrained thus avoiding any further concern.

Thus 2013TV135 is telling us the importance of both, a well coordinated follow-up campaign and the importance of extending the NEO sky surveys to the southern skies.

For the time being, stay tuned: the values of the impact probability (IP) and  Palermo Scale (PS) are reported daily in the table below:

 impact date            IP         PS    computation date

 2032/08/26.371  2.02E-5  -1.73    2013/10/16
 2032/08/26.364  2.74E-5  -1.62    2013/10/17
 2032/08/26.355  4.34E-5  -1.41    2013/10/18
 2032/08/26.352  2.65E-4  -0.62    2013/10/19
 2032/08/26.355  1.34E-4  -0.86    2013/10/20
 2032/08/26.354  1.19E-4  -0.88    2013/10/21
 2032/08/26.355  1.22E-4  -0.86    2013/10/22
 2032/08/26.355  1.97E-4  -0.65    2013/10/23
 2032/08/26.357  1.62E-4  -0.74    2013/10/24
 2032/08/26.357  1.02E-4  -0.95    2013/10/25
 2032/08/26.358  7.38E-5  -1.07    2013/10/26
 2032/08/26.358  7.70E-5  -1.06    2013/10/27
 2032/08/26.358  7.43E-5  -1.08    2013/10/28
 2032/08/26.358  9.42E-5  -0.97    2013/10/29
 2032/08/26.358  1.50E-4  -0.77    2013/10/30
 2032/08/26.359  2.31E-4  -0.58    2013/10/31
 2032/08/26.359  2.20E-4  -0.60    2013/11/01
 2032/08/26.359  6.46E-5  -1.14    2013/11/02
 2032/08/26.358  7.58E-6  -2.07    2013/11/03
 2032/08/26.358  5.25E-9  -5.49    2013/11/04
 2032/08/26.358  8.36E-8  -4.03    2013/11/05
 2032/08/26.359  2.79E-7  -3.51    2013/11/06
 2032/08/26.358  1.82E-7  -3.69    2013/11/07

Update: on 8 November 2013 asteroid 2013TV135 has been removed from the Risk Page. The non-zero impact probability spotted by monitoring systems just after its discovery dropped essentially to zero. The bulk of astrometric data collected by astronomers during one month of observations helped to improve our knowledge of its orbit, that eventually turned out to be a safe one.

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SPACE ODDITY: THE MYSTERY OF 2013 QW1

19 September 2013

Artificial object 2013 QW1 as imaged by Telescopio Nazionale Galileo/TNG.

Artificial object 2013 QW1 as imaged by Telescopio Nazionale Galileo/TNG (Copyright TNG/Telescopio Nazionale Galileo)

Last month, ESA's near-Earth asteroid coordination centre triggered a series of European observations that confirmed an unknown object was, in fact, of human origin. The confirmation was the Centre's second such success in recent months and demonstrates the effectiveness of the Agency's asteroid-monitoring activities.

On 23 August, a rather unusual object was spotted in the sky by the US PanSTARRS asteroid survey and provisionally named 2013 QW1. The suspected near-Earth object (NEO) was moving in an Earth-centred orbit, leading astronomers to ask: was it natural or artificial?

If artificial, it would not be the first time that an asteroid-hunting survey had rediscovered a lost rocket stage wandering in space close to the edge of our planet's gravitational reach.
 

Apollo 12 on the launch pad

Apollo 12 at Pad A, Launch Complex 39, Kennedy Space Center (Copyright NASA)


Another object found in 2002

For example, when the third stage of the Apollo 12 mission failed to crash on the Moon as planned (NASA used such impacts to generate ‘Moonquakes' that could be studied by lunar seismographs to gain information on the Moon's interior), its subsequent orbital evolution was alternatively dominated by the attraction of the Sun and Earth.

The object was eventually rediscovered in 2002 as a temporary satellite of Earth, and its manmade origin was revealed by analysing the light reflected by the rocket body, which did not resemble that of an asteroid but rather revealed the titanium-enriched white paint used at that time for the Apollo rockets.

However, for the mysterious 2013 QW1, things were not that simple, and further observations were needed to determine whether it was artificial or natural.

That's when ESA's NEO Coordination Centre became involved, sending an alert to a number of collaborating observatories in Europe to trigger additional observations that might help to confirm the object's identity.
 

2012 QW1 Spectrum

2013 QW1 Spectrum (Copyright Observatoire de Paris/D. Perna and Maria Antonietta Barucci)

European astronomers up to challenge

The challenge was taken up by a team led by Elisabetta Dotto at INAF–Osservatorio di Roma, and Davide Perna and Maria Antonietta Barucci at the Observatoire de Paris, Meudon, who obtained time on the Italian Telescopio Nazionale Galileo to capture light reflected from the object.

"It was a bit of a challenge, because the object was moving fast with respect to a typical suspected NEO," said Dr Perna.

"But despite the difficulties, observations were made with an instrument called DOLORES, for ‘Device Optimized for the LOw RESolution', which allowed us to obtain the object's spectrum."

The result was a spectrum that does not resemble any asteroid. Instead, it bore strong similarities with the spectra of previously observed space junk such as discarded rocket stages, abandoned boosters or defunct satellites.

These measurements provided convincing evidence of the artificial nature of 2013 QW1 – it is possibly a booster stage – and supported it being removed from ESA's NEO catalogue and included, under the name 2010-050B, in the Minor Planet Center's Distant Artificial Satellite Observations list.

ESA's coordinating role

The event highlights the coordination role that ESA's new NEO Coordination Centre is playing in addition to its primary function of providing information on all known NEOs, including their orbits, impact risk and close approaches to Earth.

"The observations by European astronomers coordinated by ESA demonstrated a very quick reaction in getting high-quality data that conclusively identified the object as artificial, and hence no threat," says Detlef Koschny, responsible for NEO activities at ESA's Space Situational Awareness programme office.

"Our Centre has again shown it is serving as a focal point for coordinating observations which are vital for the European and international community involved in asteroid science, impact monitoring and mitigation."

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HAPPY BIRTHDAY, NEAS!

14 August 2013

The number of known Near-Earth Asteroids has just overcome 10,000 units! This result represents an important achievement if one thinks that over the one hundred years between 1898 (when the first NEA, 433 Eros was discovered) and 1998 only about 500 NEAs had been found, while the current NEA discovery rate is about 1,000 per year.

Out of the 10,000 discoveries, roughly 10 percent are larger than one kilometer in size, while the vast majority of NEAs are smaller than that, with the number of objects of a given size quickly increasing as the size decreases.

The first and most important step to protect our planet from NEAs is to discover all objects potentially at risk of collision with the Earth and in doing so the present wide-field, high-sensitivity sky surveys have proven extremely effective, putting astronomers are on the right track.
 

Eros Dicovery Plate

The elongated track left by 433 Eros is clearly visible in the discovery plate of the first NEA taken by Gustav Witt from the Observatory of Berlin. More details on the story behind Eros discovery at
http://spaceguard.iaps.inaf.it/tumblingstone/issues/num20/eng/eros.htm

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TARGET ASTEROID TRACKED BY EUROPEAN TEAMS

18 July 2013

In a recent close-ish flyby, asteroid 2002 GT was studied in detail for the first time by a network of European astronomers. The observations were coordinated by ESA's asteroid centre in Italy, and should prove crucial for a future spacecraft rendezvous.

Asteroid 2002 GT, a relatively large object a few hundred metres across, made a somewhat close flyby of Earth on 26 June, passing us at almost 50 times the distance of the Moon.

Asteroid 2002GT passes Earth 26 June 2013 (More about this video)

The encounter sparked intensive worldwide observations because the asteroid is the target of NASA's Epoxi mission in January 2020.

Last month's flyby was the last chance before then to study the object's diameter, rotation, composition and other physical characteristics.

Ideal opportunity to coordinate response

"The flyby presented an ideal opportunity to exercise the unique ‘coordinating function' of ESA's new Near-Earth Object Coordination Centre," says Ettore Perozzi, project leader for NEO services at Deimos Space.

Asteroid in infrared

"By alerting and then collating observations from diverse European teams, the Centre was able to provide a comprehensive set of results back to the scientific and space exploration communities, a cycle that wasn't happening before. This is really a first for Europe."

Deimos Space leads a project team that operates the Centre at the Agency's ESRIN site near Rome.

The gathered information will enable a very good characterisation of the asteroid's surface composition, thermal properties, shape and rotation. All of these features are crucial for any spacecraft visit.

Moreover, analysis of its changing brightness indicates the possible presence of a small moon.

 Focal point: ESA's NEO Coordination Centre

Gerhard Drolshagen, co-manager of the NEO segment at ESA's Space Situational Awareness programme office, says the 2002 GT event highlighted the potential coordination role that the Centre can play in addition to its primary function of providing information on all known NEOs, including their orbits, impact risk and close approaches to Earth.

"Traditionally, Europe's asteroid community reliably delivered world-class observations and has been credited with many significant discoveries and findings. What was lacking, however, was a central point to coordinate and synthesise data that could function across national and organisational boundaries.

Asteroid 2002 GT

"Our Centre has proven it can act as a driving force and a focal point for the European and international community involved in asteroid science, impact monitoring and mitigation."

Ettore adds: "We now know 2002 GT is a rocky body, belonging to a peculiar transition class that astronomers refer to as ‘Sq-type'.

Asteroid type

"It's also a potentially hazardous object, as its orbit crosses that of Earth, so it's certainly a very interesting object, well worth watching."

More about the NEO Coordination Centre, SSA and contact information

About 2002GT observations

ESA's Near-Earth Object Coordination Centre (NEO-CC) received well-documented observations of 2002GT as follows:

- Photometry and light-curve data from the 1 m-diameter C2PU telescope at the Observatoire de la Cote d'Azur, which allows calculation of the rotation period (3.77 hours). The shape of the light curve is also compatible with the presence of a satellite.

- Spectra and photometric data from Asiago Observatory (University of Padova and Observatory of Padova) which allows determination of the asteroid type (Sq), in agreement with other observations.

- Infrared observations from the Campo Imperatore Station of the INAF Rome Astronomical Observatory. Even under bad weather conditions, teams there were able to spot the asteroid 20 days before Earth flyby.

- Astrometry from Gaia-FUN-SSO. Six telescopes observed 2002 GT providing more than 1000 astrometric measurements. These were sent to the Minor Planet Centre and processed at the Institut de Mécanique Céléste et de Calcul des Ephémérides for computing orbital elements.

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COMET ISON: RECENT OBSERVATIONS OF AN APPROACHING BODY

24 June 2013

A new series of images from Gemini Observatory shows Comet C/2012 S1 (ISON) heading toward an extremely close rendezvous with the Sun. The images have been takenbetween February and May 2013 and show the comet's remarkable activity despite its current great distance from the Sun and Earth (730-580 million kilometers; or 4.9-3.9 A.U. from the Sun, just inside the orbital distance of Jupiter). Each image in the series is taken with the Gemini Multi-Object Spectrograph at the Gemini North telescope on Mauna Kea, Hawaii.

Discovered in September 2012 by two Russian amateur astronomers, Comet ISON will come to perihelion on 28 November 2013 at a distance of 0.012 AU (1,800,000 km) from the center point of the Sun. Accounting for the solar radius, the comet will pass approximately 1,100,000 km above the Sun's surface. This will be a very close pass. With a fairly large nucleus, estimated in the 1 to 10 km range, the comet will surely undergo strong radiation and tidal stresses and a tidal breakup is not an improbable outcome of the graze. But if Comet ISON survives that close encounter, the comet may appear in the morning sky before dawn in early December and become one of the greatest comets in the last 50 years or more.

Images of Comet ISON obtained using the Gemini Multi-Object Spectrograph at Gemini North on February 4, March 4, April 3, and May 4, 2013 (left to right, respectively; Comet ISON at center in all images). Credit: Gemini Observatory/AURA.

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NEO COORDINATION AND BIG DATA

17 June 2013

An interesting connection between Earth Observation and NEO monitoring activities has been unveiled through the NEO Coordination Centre participation at the "Big Data From Space" meeting, held at ESRIN from 5 to 7 june 2013 (http://www.congrexprojects.com/2013-events/13c10/programme).

The meeting aims to timely face the challenge of the huge increase in the images flow coming from space which will characterise the next generation of Earth Observation missions. The study case presented by the NEOCC refers to the discovery and characterization of the Kamil crater, a rayed impact crater with 45 m in diameter located in southern Egypt and first identified on Google Earth in 2008.

The Kamil crater floor depth is 16 m and is overlain by a 6 m-thick crater-fill material, which is consistent with a crater generated by an iron meteorite 1.3 m in diameter impacting at a velocity between 3 and 4 km/s. QuickBird Image 2009, Courtesy of Telespazio.

A geophysical expedition was undertaken in February 2010, which collected several hundred kilograms of nickel-enriched iron meteorites and performed in-situ measurements. Prior to the expedition extensive analysis of the impact site was performed by both high resolution optical images and by radar acquisitions from the Italian COSMO-SkyMed satellites, allowing detailed geo-morphological analysis of the features surrounding the crater and the search for secondary impacts.

The possibility of setting up an extended survey of small impact craters in inaccessible regions by using multispectral high resolution images appears then an appealing opportunity and a novel application within the "Big Data" initiative. The utilisation of Earth Observation data for developing and implementing new services at the NEO Coordination Centre and their contribution to operations has been also discussed. The NEOCC presentation can be found here.

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WATCHING FOR HAZARDS: ESA OPENS ASTEORID CENTRE

22 May 2013

SSA NEO-CC inauguration

ESA today inaugurated a new hub that will strengthen Europe's contribution to the global hunt for asteroids and other hazardous natural objects that may strike Earth.

Near-Earth Objects, or NEOs, are asteroids or comets with sizes ranging from metres to tens of kilometres that orbit the Sun and whose orbits come close to that of Earth. There are over 600.000 asteroids known in our Solar System, and almost 10.000 of them are NEOs.

Dramatic proof that some of these could strike Earth came on 15 February, when an unknown object thought to be 17–20 m in diameter exploded high above Chelyabinsk, Russia, with 20–30 times the energy of the Hiroshima atomic bomb. The resulting shock wave caused widespread damage and injuries, making it the largest known natural object to have entered the atmosphere since the 1908 Tunguska event.

The NEO Coordination Centre will serve as the central access point to a network of European NEO data sources and information providers being established under ESA's Space Situational Awareness (SSA) Programme.

This is the second centre to be opened under SSA leadership after the Space Weather Coordination Centre that opened in Brussels last month.

Asteroid trace over Chelyabinsk, Russia, on 15 February 2013

Located at ESRIN, ESA's centre for Earth observation, the centre was formally inaugurated today by Thomas Reiter, ESA Director of Human Spaceflight and Operations, together with Augusto Cramarossa, Italian Delegate to the ESA Council, and Claudio Portelli, Italian Delegate to the SSA Programme, both of ASI, the Italian space agency.

The event was hosted by Volker Liebig, ESA Director of Earth Observation Programmes and Head of the ESRIN Establishment.

The new centre will support experts in the field by federating new and existing European assets, systems and sensors into a future NEO system. It will support the integration and initial operation of ESA's NEO information distribution network.

Asteroid 2012DA14

The Centre is also the focus point for scientific studies needed to improve NEO warning services and provide near-realtime data to European and international customers, including scientific bodies, international organisations and decision-makers.

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AFTER CHELYABINSK: EUROPEAN EXPERTS ASSESS ASTEROID OPTIONS

8 May 2013

Asteroid trace over Chelyabinsk, Russia, on 15 February 2013

In February, a speeding asteroid slammed into our atmosphere and exploded high over Russia's Ural region, injuring hundreds and causing millions of euros of damage. What should we do if we have a similar – or even bigger – strike in the future?

Of the more than 600.000 known asteroids in our Solar System, almost 10.000 are classified as near-Earth objects, or NEOs, because their orbits bring them relatively close to Earth's path.

Dramatic proof that any of these can strike Earth came on 15 February, when an unknown object thought to be 17–20 m in diameter arrived at 66 000 km/h and exploded high above Chelyabinsk, Russia, with 20–30 times the energy of the Hiroshima atomic bomb.

The resulting shock wave caused widespread damage and injuries, making it the largest known natural object to have entered the atmosphere since the 1908 Tunguska event, which destroyed a remote forest area of Siberia.

"It's important that we become aware of the current and future position of NEOs, develop estimates on the likelihood of impacts and assess the possible consequences," says Detlef Koschny, Head of NEO activities in the Agency's Space Situational Awareness (SSA) Programme Office. 

Artist's impression of asteroids passing Earth

"More importantly, we must consider whether and how warning, mitigation and possible deflection actions can be taken. It's important not only for Europe, but for the rest of the planet, too."

One aspect of ESA's four-year-old SSA activity requires the development of an integrated system to scan the sky nightly for as-yet-undiscovered NEOs.

Another important element is studying how mitigation measures can be applied in the case of smaller NEOs, and how to deflect any larger ones that may seriously threaten our home planet.

This week, Deimos Space, an industrial partner working for ESA on SSA, has invited top researchers from universities, research institutes, national space agencies and industry in Europe and the USA to discuss the state of the art in NEO impact effects and threat mitigation.

The meeting is taking place in Tres Cantos, Spain, near Madrid.

"A great deal of work remains to be done, for example, in computer modelling of impact effects, how airbursts differ from ground strikes, kinetic versus explosive deflection strategies and much more," says Gerhard Drolshagen, of the SSA Programme Office.

"The aim is to develop plans that will guide us in current and future NEO research and development."

Ultimately, ESA aims to develop the capability to integrate Europe's current and new assets – such as automated telescopes – into a coordinated and more efficient NEO system that can provide nightly sky surveys and advanced warning.

"With this, we can work with our partner agencies, scientists, industry and international bodies like the UN to offer firm options to national governments and political decision-makers," says Nicolas Bobrinsky, Head of ESA's SSA Programme.

"Events like the Chelyabinsk strike show that the NEO hazard is not just theoretical, and we need to invest in practical measures today to address tomorrow's threats."

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TOTAS TEAM SCORES ANOTHER HITS

19 February 2013

In the last observing slot the TOTAS survey found another NEO. This is the fifth NEO found in about 300 hours of survey time, which is a good result considering the field of view of the telescope. The lucky 'clicker' who identified the object as a real object was Felix Hormuth. Congratulations!

The object was announced by the Minor Planet Center here: http://www.minorplanetcenter.net/mpec/K13/K13D26.html.

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FIREBALL OVER RUSSIA

18 February 2013

On 15 Feb 2013, a very large fireball was reported over Chelyabinsk, Russia. Peter Brown from the University of Western Ontario, Canada, analyzed infrasound measurements of the event and deduced the following parameters:

Time of impact: 03:20:26 UT on 15-FEB-2013
Entry angle: 20 degree from surface
Entry velocity: below 20 km/s
Trajectory direction: North to South
Asteroid diameter before entry in the atmosphere: about 15 m
Kinetic energy: 500kt TNT equivalent (corresponding to 30 times the energy of the Hiroshima bomb)
Explosion altitude: 15-25 km

The direction of the trajectory and the large distance in time indicate that the object was unrelated to asteroid 2012DA14, which had a very close flyby in the evening of the same day.

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STRANGER IN THE NIGHT: SPACE ROCK TO MAKE CLOSE EARTH FLYBY

7 February 2013

Artist's impression of asteroids passing Earth

A little-known asteroid will skim past Earth on 15 February, passing just 28 000 km from our planet. The 50 m-diameter chunk of space rock was discovered last year by ESA-sponsored amateur astronomers in Spain.

Details of the ancient asteroid, 2012 DA14, are sketchy – no direct measurements of its size are available. From its brightness, scientists estimate its diameter at 50–80 m. Its composition is unknown and its mass is thought to be of the order of 130 000 tonnes.

What is known is that it will not impact Earth anytime soon.

"Its orbit can be computed quite accurately using Europe's NEODyS asteroid database," says Detlef Koschny, responsible for near-Earth objects at ESA's Space Situational Awareness office.

"These computations show that a collision with Earth can be excluded quite safely at least for this century."

Asteroid 2012 DA14

On 15 February, the asteroid will make its closest pass to our planet this century when it flies by at 7.8 km/s at a distance of just within 28 000 km.

"This is well inside the geostationary ring, where many communication satellites are located," says Detlef. "There is no danger to these satellites, however, as the asteroid will come ‘from below' and not intersect the geostationary belt."

The asteroid will make its closest approach at around 19:40 GMT (20:40 CET) on Friday evening next week. While tiny against the vastness of our Solar System, it should be visible in Europe to anyone with a good pair of binoculars and an idea of where to look (see link to details below).

The asteroid was discovered by the La Sagra Sky Survey, which is supported by ESA's Space Situational Awareness programme, on 22 February 2012. The observatory is in southeast Spain, near Granada, at an altitude of 1700 m, one of the darkest, least light-polluted locations on the European mainland.

The small size and previously unknown orbit of 2012 DA14 meant that it was spotted only after it had flown past Earth at about seven times the distance of the Moon.

"If this object were made of iron and it were to hit our planet, it could create a crater comparable to the 1.5 km Meteor Crater near Flagstaff, Arizona, for example," says Detlef. "However, it won't."

Asteroid 2012 DA14 orbit

Finding near-Earth objects (NEOs) like these – passing close to our planet and large enough to do damage if they were to enter our atmosphere – is a major goal of ESA's Space Situational Awareness (SSA) programme.

The SSA office sponsors a number of astronomer groups in Europe, supporting their local surveys or allocating observation time at ESA's own telescope on Tenerife, Spain.

The discovery of 2012 DA14 was particularly significant for the Agency's SSA office because it is typical of the estimated half a million undiscovered NEOs up to 30 m across.

"Our SSA programme is developing a system of automated optical telescopes that can detect asteroids just like this one," says ESA's Nicolas Bobrinsky, SSA programme manager.

"In cooperation with survey efforts worldwide, our goal is to spot NEOs larger than 40 m in size at least three weeks before closest approach to Earth."

To achieve this, ESA teams supported by European industry are developing a system of automated 1 m-diameter telescopes capable of imaging the complete sky in one night. 

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SUCCESSFUL OBSERVING SLOT WITH THE OGS TELESCOPE

17 January 2013

During the last observing run with the ESA 1-m telesope on Tenerife (the OGS = Optical Ground Station) the SSA-NEO programme successfully recovered three 'lost' NEOs. In addition, one new NEO was discovered. The new object has the designation 2013 AS76:

http://www.minorplanetcenter.net/mpec/K13/K13B02.html

From the brightness of the object the size can be estimated to be around 40 - 100 m. With a minimum flyby distance to the Earth of just above 0.05 AU or 7.5 Million km it just falls outside the definition of a 'Potentially Hazardous Object'. Thus it will not pose any threat to our planet in the near future.

Three so-called NEO candidates observed with the OGS are still on the NEO Confirmation Page of the Minor Planet Center (http://www.minorplanetcenter.net/iau/NEO/toconfirm_tabular.html).

This discovery was possible because of the dedication and support of the TOTAS team (http://vmo.estec.esa.int/totas). The lucky person who first saw this object was amateur astronomer Gerhard Lehmann.

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THE IMPACT RISK FOR 2011 AG5 HAS BEEN CLEARED

7 January 2013

The orbital path of 2011 AG5 has been carefully analyzed in the past year, due to its 1-in-550 probability to pass, during the moderately close approach to the Earth that will take place in early February 2023, through a 365 km wide keyhole leading to a resonant return with impact on the Earth on 5 February 2040.

As it is customary in these cases, observing opportunities, useful to refine the orbit and possibly remove the collision possibilities, have been looked for; the first of these opportunities has occurred in October 2012, and has been put to good use by a team of the Institute for Astronomy of the University of Hawaii, using the Gemini North telescope.

Given the difficulty of the observations, the analysis of the collected data has taken some time. The astrometry so obtained has been fed to the CLOMON2 impact monitoring robot, and the results have been carefully cross-checked with those of JPL Sentry.

The result is that no impact with the Earth is possible between now and 2100. It is anyway desirable that the next observing opportunities for this object be exploited, so as to further refine our knowledge of its motion and especially of the circumstances of its encounter with the Earth in 2023, when physical observations would be possible. (Source: NEODyS)

Gemini Multi-Object Spectrograph image of 2011 AG5. The asteroid is the point at the center of the image -circled. (Image credit: Gemini Observatory)

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ANOTHER RECOVERY - 2009 XZ1 FOUND AGAIN

15 November 2012

In the last observing slot at ESA's 1-m telescope on Tenerife, the previously 'lost' object 2009 XZ1 has been recovered. E. Schwab (Germany) has planned and analyzed the observations. The Minor Planet Electronic Circular announcing the recovery can be found here: http://www.minorplanetcenter.net/mpec/K12/K12V81.html. The animation shows a 4' x 4' cutout of the original image, showing five stacks of images following the asteroid. The object is the dot moving upwards close to the center of the images between the trailed stars.

Image credit: ESA/Schwab

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NICE SURPRISE DURING OBSERVATIONS

17 October 2012

In the last SSA-NEO observing run on Tenerife, we have imaged an object on the NEO Confirmation Page called SW40nU (now called comet C/2012 T5), discovered by the Spacewatch survey. It turned out to be a comet. This image shows a stack of all obtained images on 15 Oct 2012 at 23:29 UT, tracked on the object. The new comet is in the center of the image, the short tail is clearly visible arching to the right of the object. Because the image was tracked on the comet, the stars are trailed lines. Data for this object has been submitted to the Minor Planet Center and the Central Bureau for Astronomical Telegrams.

Image credit: ESA/Knöfel

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LOST ASTEROID REDISCOVERED WITH A LITTLE HELP FROM ESA

12 October 2012

A potentially hazardous asteroid once found but then lost has been rediscovered and its orbit confirmed by a determined amateur astronomer working with ESA's space hazards programme. The half-kilometre object will not threaten Earth anytime soon.

Asteroid 2008SE85

Amateur astronomer Erwin Schwab, from Germany, conducted his asteroid hunt in September during a regular observation slot at ESA's Optical Ground Station in Tenerife, Spain, sponsored by the Agency's Space Situational Awareness programme.

He was determined to rediscover the object, known by its catalogue name as 2008SE85.

Potentially Hazardous Asteroid 2008SE85 was discovered in September 2008 by the Catalina Sky Survey, and observed by a few observatories to October 2008. 

Asteroid considered lost

Since then, however, nobody had observed the object and predictions for its current position had become so inaccurate that the object was considered to be ‘lost'.

Orbit of 2008SE85

Erwin planned his observing sequence to look for the object within the area of uncertainty of its predicted position. After only a few hours, he found it about 2° – four times the apparent size of the Moon – away from its predicted position.

"I found the object on the evening of Saturday, 15 September, while checking the images on my computer," says Erwin.

"I then saw it again at 01:30 on Sunday morning – and that was my birthday! It was one of the nicest birthday presents."

These new observations of the roughly 500 m-diameter asteroid will allow a much more accurate determination of its orbit and help confirm that it will not be a threat to Earth anytime soon.

Potentially Hazardous Asteroids approach Earth closer than about 7 million km; about 1300 are known.

When a new asteroid is discovered, follow-up observations must be done within a few hours and then days to ensure it is not subsequently lost.

USA-based Minor Planet Center acknowledges the find

Asteroid position measurements are collected from observers worldwide by the US-based Minor Planet Center, which acknowledged the rediscovery of 2008SE85 by releasing a Minor Planet Electronic Circular announcing the new observations.

1m telescope at ESA's Optical Ground Station

"These observations were part of the strong collaboration that we have with a number of experienced backyard observers," says Detlef Koschny, Head of the Near-Earth Object segment of ESA's Space Situational Awareness programme.

"It's not the first time our collaboration with amateurs has scored such a success. Members of the Teide Observatory Tenerife Asteroid Survey started by Matthias Busch from Heppenheim, Germany, discovered two new near-Earth objects during the last year while working with our observing programme."

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A SENSE OF SOMETHING STRANGE

While the sky becomes more and more continuously scanned by ground and space-based NEO surveys, discovering objects in unusual orbital configurations represents the new frontier. Their dynamics translates into peculiar visibility conditions thus calling for smart observation strategies. Tunguska-class (i.e. 30-60 meter size) objects in orbits closely resembling that of the Earth turn out particularly elusive due to their faint appearance and the long synodic period. The only chance to spot them in the sky is when they, from time to time, come close to our planet, crossing the night sky at high declinations. This is the case for asteroid 2012 DA14, discovered from the La Sagra Observatory, in southern Spain, on 23 February 2012 (a detailed account is posted at the observatory web site http://www.oam.es/Asteroid_2012DA14.htm). 2012DA14 is a 45 meter NEO which exhibit an interesting dynamical behaviour characterized in the 2001-2013 timeframe by yearly close approaches to our planet (http://newton.dm.unipi.it/neodys/index.php?pc=1.1.8&n=2012DA14) down to distances smaller than the geostationary ring where most telecommunication satellites reside. Even if 2012 DA14 will not impact the Earth it poses the challenge of how to discover these objects with a warning time large enough for mitigation. A space-based observatory in a "strange" orbital configuration has been proposed to this end.

Image: The discovery plates of 2012DA14 (credits: La Sagra Sky Survey)

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A WISE DECISION

The data gathered by the US WISE mission have been released as public domain on 14 March 2012 (http://wise2.ipac.caltech.edu/docs/release/allsky/). This release provides improved calibration and processing algorithms. After the successful detection of 2010TK7, the first Earth Trojan Asteroid, which resulted from post-processing archived WISE data, new discoveries are expected in the future.

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GAIA FOR NEOs

Although Gaia's primary mission goal is the precise measurement of star positions and not observing NEOs, nevertheless it is likely to produce a significant contribution to NEO detection. This is due to the peculiar way its on-board telescopes will scan the sky, reaching solar elongations as low as 45 degrees. Yet without a robust ground-based network of follow-up telescopes Gaia's detections would lose much of their value because of the poor quality of the computed orbits. The Gaia working group devoted to moving objects detection, led by the Institut de Méchanique Céleste et de Calcul des Éphémérides (IMCCE) of the Observatory of Paris, is taking up the challenge. After a successful kick-off meetig in 2010 a second workshop is planned in Paris from 19 to 21 September 2012.

http://www.imcce.fr/hosted_sites/gaiafun2012/index.php

Image: Logo of the Gaia Follow-Up-Network of Solar System Objects