NEO Coordination Centre
Please note that all SSA-NEO Services are under development
|Last update: 2015-11-26 14:46:00 UTC|
WT1190F comes back: ESA NEOCC watching rare reentry
22 October 2015
An object discovered on 3 October 2015, temporarily designated WT1190F by the observers, will enter the Earth's
atmosphere on 13 November. It was discovered by the Catalina Sky Survey (http://www.lpl.arizona.edu/css).
The object is in Earth orbit, with a period of about three weeks. Its orbit is quite well known because it was also observed twice in 2013 by the same survey team. This long observational coverage is sufficient to model its trajectory with good accuracy and obtain two interesting results.
First, the object is likely man made. The motion of this body over about two years can be modelled in detail only if the effects of solar radiation pressure are taken into account. The intensity of this solar push is proportional to the object's area-to-mass ratio, which can therefore be estimated, providing an indirect clue to its density. It turns out that this body has a mean density that is about 10% that of water. This is too low to be a natural space rock, but it is compatible with being a hollow shell, such as the spent upper stage of a rocket.
The second, and even more interesting result, is that the object will re-enter Earth's atmosphere in a few weeks, around 06:20 UT on 13 November 2015. The object is quite small, at most a couple of meters in diameter, and a significant fraction if not all of it can be expected to completely burn up in the atmosphere. Whatever is left will fall into the ocean about 100 km off the southern coast of Sri Lanka. Its mass is not sufficient to cause any threat to the area, but the show will still be spectacular, since for a few seconds the object will become quite bright in the noon sky.
During the next few weeks ESA's NEOCC will organize observational campaigns to collect as much data as possible on this object. The goal is twofold; first, the object is interesting to better understand the re-entry of satellites and debris from high orbits. Second, it provides us with an ideal opportunity to test our readiness for any possible future events involving an asteroid, since the components of this scenario, from discovery to impact, are all very similar.
WT1190F observed on 9 October 2015 with the University of Hawaii 2.2 meter telescope on Mauna Kea, Hawaii. [Credits: B. Bolin, R. Jedicke, M. Micheli]
Telescopes around the globe recently homed in on one point in the sky, observing the paired Didymos asteroids – the target for ESA’s proposed Asteroid Impact Mission.
The 800 m-diameter main body is orbited by a 170 m moon, informally dubbed Didymoon. The duo were more favourably placed from March until early June for studies.
The goal was to help with planning not only ESA’s Asteroid Impact Mission (AIM) but also the NASA-led Double Asteroid Redirection Test, or DART, which will crash into Didymoon in late 2022 as ESA’s craft looks on.
The two candidate missions together are known as the Asteroid Impact & Deflection Assessment (AIDA) mission.
The very best observations turned out to be from Flagstaff, Arizona, USA – part of the observatory that famously discovered Pluto back in 1930 – as the conditions proved optimal there.
Andy Rivkin from the John Hopkins University’s Applied Physics Laboratory explained: “The most important question we were trying to answer was how much tilt is present between the orbit of the satellite around the primary and the orbit of the Didymos system around the Sun.”
The orientation of Didymoon’s orbit is one of the key factors involved in planning the mission. It is important, for example, in calculating the approach of the spacecraft to the binary system, as well as to know when the asteroid moon will fall into shadow – needed for scheduling payload operations.
Sharpening our estimates of the mass of the two Didymos bodies is also crucial, not least because the outcome of the DART impact will be influenced by the asteroids’ density.
Petr Pravec, from the Astronomical Institute of the Academy of Sciences of the Czech Republic, commented: “Unfortunately, we had bad weather on many of the nights that we were planning to get data. However, we were able to obtain some data and are using it in combination with older optical and radar data to refine the orbital period for the system and the density of Didymos.”
Nicholas Moskovitz, of Lowell University, Flagstaff, reveals: “The next observations of the Didymos binary system will be in the spring of 2017. We should be able to obtain time on larger telescopes as we hope AIM will be a fully approved mission by then. In addition, the asteroid system will be about 30% brighter than it was this time round, which will make the observations somewhat easier."
“There are additional opportunities for pre-impact observations in 2019 and 2021, but we expect to have cleared up any lingering questions in 2017 and will just use the later observations to update our orbit calculations.”
“The observers did a great job,” says ESA’s Detlef Koschny. “Despite the bad weather conditions, they managed to collect good data. This is a nice demonstration of how well collaboration between an Agency and the science community can work.”
Each year, astronomers worldwide discover over 1000 new asteroids or other space rocks that could strike our planet. And if one is spotted heading towards Earth, experts working in ESA and national emergency offices need to know who should do what, and when.
A critical factor in protecting lives and property in the event of an object being discovered en route to Earth is civil response, and how national authorities can best inform their citizens of what to do. In turn, this requires ESA to know how best to compile, analyse and distribute scientific information on an impending object to those national authorities.
A workshop sponsored by ESA at the end of June saw delegates from six ESA Member states meeting with the Agency's Space Situational Awareness team to discuss asteroids – and to exercise the reactions that each would foresee in the event of a real near-Earth object, or NEO, threat.
National emergency response offices in Switzerland, Germany, Luxembourg, Romania, Sweden and the UK learned how the flow of information during an alert would run from ESA's NEO Coordination Centre to national authorities and then into national alert and warning systems.
Delegates contributed crucial information about their countries' response networks – think of those used for severe weather or flood warning – aimed at the general public, businesses and communities.
"Every year, more than 1000 new NEOs are discovered," notes ESA's Gerhard Drolshagen. "Most of them are some tens of metres in size and have the potential to cause damage on the ground. Sooner or later, one will actually hit Earth. These workshops are helping us to prepare for such an event."
Of the more than 600 000 known asteroids in our Solar System, more than 12 000 are classified as NEOs because their orbits bring them relatively close to our path.
While the likelihood of any real event remains small, understanding them and devising the best response is more important than ever since the Chelyabinsk strike in February 2013. Global awareness spiked after the event, and governments began to become aware of the kind of information they needed to provide to people on the ground – such as staying away from windows to avoid flying glass.
In this third workshop, the UN-mandated International Asteroid Warning Network (IAWN) and its relationship to ESA was highlighted.
"Establishing interfaces to the various emergency response offices is now a much clearer process," says ESA's Detlef Koschny. "We also learned which information needs to be made available at what time, and to whom."
Delegates are now aware of the channels through which ESA could inform countries about threats, so that they could prepare culturally and geographically appropriate responses for their countries.
"In the event of a threat, we need to clearly establish roles and responsibilities for the impact zone," said Nicolas Bobrinsky, Head of ESA's Space Situational Awareness. "Clear planning is the key to improved public safety."
The ESA SSA-NEO Coordination Centre has released the May newsletter summarising the most relevant data and events on asteroids and comets approaching the orbit of the Earth.
Call for media: ESA hosts IAA Planetary Defence Conference 2015
10 April 2015
Assessing the threat
CREOP Room, Building 11, ESRIN
|10:00||Doors open; registration|
The Planetary Defence Conference: Global cooperation against asteroid threats
Dr Detlef Koschny, Head of NEO Segment, ESA Space Situational Awareness Programme
Finding asteroids & avoiding impacts: space agencies taking action to prevent future catastrophe
Dr Lindley Johnston, NEO Programs Executive, Science Mission Directorate, HQ NASA
Responding to asteroid threat scenarios - The importance of impact simulation exercises
Debbie Lewis, Director, Resilience Planning at Axiom (Alderney) Ltd.
Presentation of findings PDC 2015
Dr William Ailor, Distinguished Engineer, The Aerospace Corporation, PDC 2015 co-chair
Richard Tremayne-Smith, Advisor, The Secure World Foundation, PDC 2015 co-chair
End of briefing; opportunities for individual interviews; small group visits to ESA's NEO Coordination Centre
Tel.: +33 1 47 23 82 15
LBT detects one of the faintest NEOs ever observed thanks to a collaboration between INAF and ESA
2 December 2014
The Large Binocular Telescope (LBT), of which the Italian National Institute for Astrophysics (INAF) is a main partner, has successfully observed asteroid 2014 KC46 in one of the faintest Near-Earth Object (NEO) recoveries ever performed. This challenging observation, which pushed the limits of the telescope down to a visual magnitude of 26.3, was carried out on the nights of 28 and 30 October 2014 by a new collaboration between the Italian LBT team and the NEO Coordination Centre of the European Space Agency. LBT spotted the 100-metre-sized object while it was just beyond the orbit of Mars. The corresponding measurement of its position was sufficient to decrease the uncertainties associated to its orbital path to the point of safely dismissing any possible threat that the asteroid may hit the Earth in the near future.
The successful observation of 2014 KC46 has been made possible by the unique performances of LBT: a large field of view to entirely cover the uncertainty in the position of the target asteroid, coupled with the ability to spot very faint objects thanks to the twin 8.4-meter mirrors of the telescope. This result highlights the importance of rapid response for securing NEO orbits and the effectiveness of LBT in detecting faint large-uncertainty objects.
The data have been accepted by the IAU Minor Planet Center, the official organisation in charge of collecting astrometric data for small bodies of the solar system, and published in the electronic circular MPEC 2014-V35. Both the European NEODyS system and the JPL-based Sentry system updated their orbit determination and impact monitoring using the new LBT observations, and confirmed the removal of all impact solutions for the next century.
The Large Binocular Telescope is a facility consisting of two 8.4-meter mirrors on a common mount, located at an altitude of 3200 m on Mt. Graham (Arizona, USA). This telescope is equivalent in light-gathering power to a single 11.8 meter instrument. LBT is a collaboration between the Instituto Nazionale di Astrofisica (INAF), The University of Arizona, Arizona State University, Northern Arizona University, the LBT Beteiligungsgesellschaft in Germany, The Ohio State University, Research Corporation in Tucson, and the University of Notre Dame.
The NEO Segment of ESA's Space Situational Awareness (SSA) aims to coordinate and combine information from different sources, analyse them to predict possible impact with the Earth, assess danger, and analyse possible mitigations, including the deflection of a menacing asteroid. Within this framework, the ESA NEO Coordination Centre provides data and services on the NEO hazard and coordinates follow-up astronomical observations.
The SSA-NEO and NEOCC-Team in front of the Coordination Centre (from left to right: Gerhard Drolshagen, Philipp Maier, Detlef Koschny, Joaquim Correia de Oliveira, Marco Micheli, Fabrizio Bernardi, Barbara Borgia, Ettore Perozzi, Ana Maria Teodorescu)
ESA's bug-eyed telescope to spot risky asteroids
22 Sep 2014
Lost NEOs (part 1): how to find them in the sky
15 Sep 2014
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.
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)
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*.
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.
Happy Birthday NEOCC!
22 May 2014
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 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.
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!
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.
A good year to find a comet
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: 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.
Figure 2: Comet P/2014 C1 (TOTAS) orbit (Image credit: M. Bush/EasySky)
Getting ready for asteroids
The Recovery of 2009 FD, a Potentially Hazardous Asteroid
21 January 2014
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.
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/
Observing 2013 NJ: A study case
4 December 2013
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.
2013TV135, A NEWLY DISCOVERED OBJECT AT THE TOP OF THE IMPACT RISK LIST
23 October 2013
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.
SPACE ODDITY: THE MYSTERY OF 2013 QW1
19 September 2013
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 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.
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."
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.
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
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'.
"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."
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.
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.
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.
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.
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.
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."
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.
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.
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.
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:
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.
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)
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
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
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.
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."
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)
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.
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.
Image: Logo of the Gaia Follow-Up-Network of Solar System Objects