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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