ESA's Optical Ground Station (OGS) is 2400 m above sea level on the volcanic island of Tenerife.

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.

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 (on the left - 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.), 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.

ESA’s NEO Coordination Centre turned 10 years old this 22 of May. The Centre was inaugurated back in 2013 inside ESA’s ESRIN establishment close to Rome (Italy). It was a lucky coincidence that the Centre was opened just a few months after the most relevant asteroid impact event of the last hundred years, i.e. the Chelyabinsk event over Russia, which has fostered a surge on Planetary Defence activities ever since. The then ESA’s Space Situational Awareness Programme (since 2020 renamed as the Space Safety Programme) had been active since 2009 and had paved the way to the creation of the NEOCC.

At the time the NEOCC was inaugurated, slightly less than 10 000 NEOs had already been discovered. In just 10 years, that number has multiplied by more than three: during that period there have been twice as many discoveries as in the previous 100 years!

Since the start of operations of ESA’s NEOCC, the capabilities of the centre have steadily improved and expanded, starting from an initial federation of already existing services, and evolving into a fully independent operational system. A summary of some relevant achievements reached in these 10 years follows:

• May 2013: inauguration of the NEOCC at ESRIN, including the federation of several European NEO services (e.g. NEODyS data, EARN data, NEO chronology, NEO priority list, etc)
• April 2015: ESA and the NEOCC host the 4th Planetary Defense Conference at ESRIN
• Mid-2015: inauguration of the Test-Bed Telescope #1 in Cebreros (Spain)
• Nov 2018: incorporation into the NEOCC of full orbit determination capabilities
• Nov 2020: incorporation into the NEOCC of full impact monitoring capabilities
• March 2021: release of a new version of the NEOCC web portal
• April 2021: inauguration of the Test-Bed Telescope #2 in La Silla (Chile)
• Oct 2021: inauguration of the new NEOCC building at ESRIN
• Sep 2022: release of the NEO Toolkit in the NEOCC web portal

A recording of the inauguration session and the 2013 talks is available in this link.

To celebrate the event, the NEOCC staff visited the Specola Vaticana in Castel Gandolfo (in the Roman outskirts) and its meteorite collection. We are very grateful for the kind visit to the premises provided by Br. Robert Macke.

NEOCC staff at the Specola Vaticana. Credit: ESA / PDO / Vatican Observatory

ESA’s NEO Coordination Centre turned 10 years old this 22 of May. The Centre was inaugurated back in 2013 inside ESA’s ESRIN establishment close to Rome (Italy). It was a lucky coincidence that the Centre was opened just a few months after the most relevant asteroid impact event of the last hundred years, i.e. the Chelyabinsk event over Russia, which has fostered a surge on Planetary Defence activities ever since. The then ESA’s Space Situational Awareness Programme (since 2020 renamed as the Space Safety Programme) had been active since 2009 and had paved the way to the creation of the NEOCC.

At the time the NEOCC was inaugurated, slightly less than 10 000 NEOs had already been discovered. In just 10 years, that number has multiplied by more than three: during that period there have been twice as many discoveries as in the previous 100 years!

Since the start of operations of ESA’s NEOCC, the capabilities of the centre have steadily improved and expanded, starting from an initial federation of already existing services, and evolving into a fully independent operational system. A summary of some relevant achievements reached in these 10 years follows:

• May 2013: inauguration of the NEOCC at ESRIN, including the federation of several European NEO services (e.g. NEODyS data, EARN data, NEO chronology, NEO priority list, etc)
• April 2015: ESA and the NEOCC host the 4th Planetary Defense Conference at ESRIN
• Mid-2015: inauguration of the Test-Bed Telescope #1 in Cebreros (Spain)
• Nov 2018: incorporation into the NEOCC of full orbit determination capabilities
• Nov 2020: incorporation into the NEOCC of full impact monitoring capabilities
• March 2021: release of a new version of the NEOCC web portal
• April 2021: inauguration of the Test-Bed Telescope #2 in La Silla (Chile)
• Oct 2021: inauguration of the new NEOCC building at ESRIN
• Sep 2022: release of the NEO Toolkit in the NEOCC web portal

A recording of the inauguration session and the 2013 talks is available in this link.

To celebrate the event, the NEOCC staff visited the Specola Vaticana in Castel Gandolfo (in the Roman outskirts) and its meteorite collection. We are very grateful for the kind visit to the premises provided by Br. Robert Macke.

NEOCC staff at the Specola Vaticana. Credit: ESA / PDO / Vatican Observatory

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. Please, feel free to forward it to potentially interested people.

You can download the newsletter by clicking on the button below. To subscribe to the service, please fill in the form on page https://neo.ssa.esa.int/subscribe-to-services.

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The ESA S2P-NEO Coordination Centre has released a Close Approach Fact Sheet (CAFS) for asteroid 2023 DZ2, passing by Earth on 25 March. Please, feel free to forward it to potentially interested people.

You can download the CAFS by clicking on the button below. For subscribing to our releases, please fill in the form on page https://neo.ssa.esa.int/subscribe-to-services.

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For the seventh time, a meteoroid has been discovered before impacting the Earth. This one-metre asteroid has been discovered by Krisztián Sárneczky with the 60-cm Schmidt telescope of the Piszkéstető Observatory in Hungary. It is his second discovery of an impactor, after the impact of 2022 EB5 less than a year ago, in March 2022.

At 20:18:07 UTC on 12 February 2023 the new asteroid, now officially designated 2023 CX1, was imaged from Piszkéstető Observatory in Hungary and reported with a second position to the MPC at 20:49 UTC. About 40 minutes later some follow-up observations reported by the Višnjan Observatory in Croatia confirmed the object, and at this point the various impact assessment systems found a 100% impact probability in the area of the English Channel between 02 and 04 UTC. The estimated asteroid size was around 1 meter of diameter and posed no risk of damage for the people in the area.

During the next seven hours astronomers all around the globe observed the object and pinpointed the impact corridor over the English Channel, with a trajectory coming from West to East. The object was observed up to around 10 minutes before impact, only 5 minutes before getting into Earth’s shadow and becoming unobservable. The last image was taken at 02:46:56 UTC, by our collaborators of the Rantiga Observatory in Italy.

The fireball event happened at the predicted time (02:59 UTC) and location, with observations mostly from Southern UK and France, but also from Belgium, the Netherlands and even Germany. It is likely that some fragments of the meteoroid may have survived the atmospheric pass and fell somewhere onshore close to the coast north of Rouen, in Normandy, France.

The team at ESA’s Planetary Defence Office contributed to the event both with the timely notifications from its Meerkat system, and with the use of a network of optical telescopes established for these occasions. The observing facilities were specifically chosen to provide data useful to increase the accuracy in the determination of the impact circumstances. Astrometry from South Africa, quickly after the initial trigger, and later from the US, extended the observational baseline to continents outside Europe, providing larger parallax. Also, in the few minutes before impact, they triggered accurately-timed observations useful to reduce uncertainty of the impact time to less than 1 second.

First impact assessment by ESA’s tool Meerkat as reported at 21:33 UTC with only 7 measurements, already indicating an impact probability of ~100%. Credit: ESA / PDO

First impact corridor reported by ESA’s tool Meerkat as reported at 21:33 UTC, with the actual impact time 02:59 UTC in the middle of the uncertainty window. Credit: ESA / PDO

Asteroid 2023 CX1 entering Earth's atmosphere captured in the skies over the southern Netherlands. Credit: Gijs de Reijke

Registration is open for the ESA NEO and Debris Detection Conference - Exploiting Synergies, which will be held at ESA/ESOC, Darmstadt, Germany, 22 - 24 January 2019.

The deadline for the submission of abstracts is 1 October 2018.

The conference will highlight all classical and new disciplines of NEO and Debris Detection Research, including:

• Observation strategies - technology improvements of radar, passive optical, and laser systems
• Instrumentation component developments (CCDs, CMOS, ...)
• New telescope and radar projects (e.g. fly-eye telescope)
• Space-based observation concepts
• Space surveillance system architectures and applications
• Detection systems for fireball and other events
• Orbit prediction and determination
• On-orbit and re-entry risk assessments
• Data processing concepts
• Data exchange mechanisms and standardisation

Details on the conference venue, scope, registration, accommodation and abstract & paper submission can be found on the conference website.

We are looking forward to meeting you in Darmstadt!

With best regards from the local organisers.

ESA/ESOC,
Robert-Bosch-Strasse 5,
64293 Darmstadt,
Germany

Programme committee:
Vladimir Agapov (ROSCOSMOS), Ricardo Bevilacqua (IAA), Nicolas Bobrinsky (ESA), Richard Crowther (UKSA), Pascal Faucher (CNES), Moriba Jah (University of Texas at Austin), Lindley Johnson (NASA), Stephan Mayer (FFG), Manuel Metz (DLR), Ettore Perozzi (ASI), Thomas Schildknecht (COSPAR), Makoto Yoshikawa (JAXA)

Download the call for papers.

About two years ago, the NEOCC announced the full deployment of its orbit determination (OD) and impact monitoring (IM) software, developed and maintained by SpaceDyS s.r.l. through industrial contracts with ESA.

In the last months, all OD data and the entire risk list have been reprocessed using an updated version of the NEOCC software, which has now been renamed "Aegis".

The main updates introduced in this new version of the software are the adoption of the JPL DE441 Planetary and Lunar Ephemerides, the introduction of a new step-size formula for the propagation of orbits during close approaches, and an improved and more stable computation of the close approaches minimum distance. All these aspects aim to improve the calculation of OD and IM data. In addition, due to deep code optimisation and conversion to a dockerised architecture, the computation of IM data is now faster than before.

Finally, it is worth noting that the calculation of the Palermo Scale has changed from the old version of the software, in which the time to impact was defined as the interval between the mean epoch of observations and the date of impact. Currently, the Palermo Scale is calculated by considering the time to impact as the interval between the last IM calculation time and the potential event epoch.

A Planetary Defense Icon. Credit: ESA

For the second time this year, a small asteroid has been discovered before impacting the Earth. This time the discovery came from the Catalina Sky Survey, one of the major projects dedicated to the discovery and follow-up of NEOs, and already responsible for the discovery of the first three such cases between 2008 and 2018.

The new asteroid, now officially designated 2022 WJ1, was first imaged by the 1.5-metre Mt. Lemmon telescope at 04:53 UTC on 19 November, but the object was first reported to the MPC at 05:31, once 4 observations made it detectable by the automated pipelines running at the telescope.

Within a few minutes, ESA's own internal monitoring software reported that, based on the just-published astrometry, the object had a ~20% chance of being on a collision course, possibly hitting somewhere in North America 2 to 3 hours later. A few minutes later all other impact monitoring programs also sent alerts outlining a similar scenario.

Excerpt of the first impact assessment by ESA’s tool Meerkat as reported at 05:36 UTC, indicating an impact probability of ~20%. Credit: ESA / PDO

Within minutes of the notifications, observers at the Catalina Sky Survey, and elsewhere in the US, started obtaining follow-up observations of the new asteroid. In less than 30 minutes from the initial trigger, the impact became confirmed, thanks to newly reported observations. Shortly after, even more astrometry became available, sufficient to pinpoint the location of the impact point with excellent precision: the small asteroid, likely less than a meter in diameter, was going to impact somewhere between Lake Erie and Lake Ontario, near the US-Canada border, around 08:27 UTC.

First impact corridor computed by ESA’s tool Meerkat as reported at 05:36 UTC, still showing a large impact uncertainty. Credit: ESA / PDO

And, at exactly the predicted time, a fireball event indeed happened at the expected location, observed by hundreds of people in the Toronto area and elsewhere and by many surveillance cameras. Soon, photos and videos also surfaced, providing a fantastic view of the event, and its incoming trajectory.

It is likely that fragments of the meteoroid may have survived the atmospheric entry, reaching the ground. The largest ones probably fell somewhere offshore the Southern coast of Lake Ontario, but some smaller ones may have landed near the Canadian city of Grimsby. Searches are ongoing, stay tuned!

Image of the fireball produced by 2022 WJ1 at atmospheric entry. Credit: R. Weryk

This October marks the 10-year anniversary of the web portal deployed and operated by the NEO Coordination Centre (NEOCC). Prior to that, the NEO Segment of ESA’s Space Situational Awareness Programme had released a contract for the development of the web portal with the aim to host all related NEO contents in the field. The release of the NEOCC web portal actually predated the official inauguration of the NEO Coordination Centre at ESRIN, which occurred in May 2013.

The initial portal set-up was based on federating several information sources that were available at the time plus some additional new functionalities. When released, it already included the following functionalities: the risk page and the close approaches list (as obtained from the NEODyS portal at that time), the observational priority list (as provided by INAF), an orbit and flyby visualisation tool developed for the portal, an NEA database search function and the EARN physical properties database (as provided by DLR).

The first news that we released was on 12 October 2012, where we discussed the rediscovery of asteroid 2008 SE85. The object had been discovered by the Catalina Sky Survey back in September 2008 and had been subsequently lost. An amateur astronomer, Erwin Schwab, was able to find it again by making use of ESA’s Optical Ground Station (OGS) in Tenerife, Spain.

As time passed, new functionalities were added to the portal step by step. This included: the FITS image database, a fireballs database, a discovery statistics page, the NEO chronology (as kindly provided by Karel van der Hucht) and many other pages. Further to that, our portal started providing orbits as calculated by ESA’s own orbit determination software from November 2018 and own impact monitoring information from November 2020. Some tools are also provided in the portal as the NEO Population Tool (NEOPOP) and the NEO Propagation Tool (NEOPROP). We also added the possibility to have automated access to the portal data from November of 2019.

After more than eight years in operation, we released in March 2021 a full new version of the portal adapted to new web standards. Very recently, at the end of last September, we released a set of graphical tools that represent a relevant change on how the trajectories of asteroids and their observability can be visualised.

Snapshot of the old NEOCC web portal as of February 2013. Credit: ESA / PDO

The European Union (EU) and ESA’s Planetary Defence Office are organising the “EU-ESA Workshop on NEO Imminent Impactors Warning Coordination”. The workshop will take place at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany between 12-14 December 2022 and it will be performed in hybrid mode, with a preference for the local attendance of the speakers.

This workshop will explore the possibilities of increasing the networking of parties involved in the process of discovering, acknowledging and following up NEO imminent impactors as well as their atmospheric entry. Building on the recent occurrence of the impact of 2022 EB5 on 11 March 2022, EU and ESA want to increase the level of coordination and cooperation between all those actors. This includes asteroid discoverers and observers, NEOCP object analysts, spacecraft operators and mission planners and fireball network operators. Goals of the workshop are to establish a network of related experts and a communication protocol to ensure that the relevant information about imminent impactors reaches all possible interested parties.

A link to the event web portal can be found here.

The workshop sessions are the following:

1. New developments and updates to imminent impactor services
2. Observatories and observation networks for imminent impactors
3. Imminent impactor observation opportunities by spacecraft
4. Fireball networks and other sensing capabilities

Workshop presentations have been organised by invitation of relevant speakers. Speakers and interested participants are invited to register to the event up to 15 November 2022. Ample slots have been allocated in the programme to allow discussions between the experts. A limited number of presentation slots are still available. If a workshop attendee considers having a relevant contribution in the subject and would like to present it at the workshop, please send a message to the organisers with a proposed title and abstract before 30 October 2022. A limited capacity of up to 60 people will be available for local attendance to the event. These will be available to the speakers wanting to attend in person and on a first come first serve to the rest of attendees.

Programme of the European Union, implemented by ESA.

Providing astronomers with useful tools is one of the long-term goals of ESA’s Planetary Defence Office (PDO) and its NEO Coordination Centre (NEOCC). The brand-new Orbit Visualisation Tool (OVT hereafter) is the first of a series of tools created by NEOCC for the NEO community: the NEO Toolkit.

The OVT updates and improves the previous Orbit Visualiser of the NEOCC portal, offering the user a new experience in which not only the graphical capabilities have been enhanced, but also a deeper level of configuration and simultaneous visualisation of several near-Earth objects (NEO) is now possible.

The most powerful feature of the OVT is the selection and 3D visualisation of the Keplerian and perturbed orbits of one or more simultaneous asteroids and comets contained in the NEOCC database.

When an object is visualised, the user is provided with a wealth of information pertaining to the spatial and temporal situation of the object. The visualisation allows the user to move freely around the Solar System, displaying various information elements and moving back and forth in time to observe the evolution of the object’s orbit.

Known past impactors as well as past and future close approaches with Earth are highlighted as the date of the event approaches the date of the simulation.

Visualisation of the perturbed orbit of (65803) Didymos (orange colour) on 26 Sep 2022. The DART spacecraft is expected to impact Didymos’ moon Dimorphos on this date. More information on the DART mission is available here. Image credit: ESA / PDO / NEOCC.

Moreover, the OVT offers the possibility of displaying different collections of asteroids according to their properties:

• The complete NEO risk list of the NEOCC.
• Groups of NEOs according to the priority list of the NEOCC: Urgent, Necessary, Useful or Low Priority.
• NEO groups such as Atiras, Atens, Apollos, Amors and others.
• … and more!

Inverted colour visualisation of the perturbed orbit of 99942 Apophis (light blue) on 10 Apr 2029, three days before its close approach to Earth, as indicated in the ‘object details’ legend. The known group of Atira NEOs is represented as light red dots. Image credit: ESA / PDO / NEOCC.

Lastly, the OVT allows the extraction of images (such as those presented here) and web-friendly videos of the visualisation for individual or public outreach purposes.

Clip exported from the Orbit Visualisation Tool, featuring the objects of the risk list as of September 2022 (pink), the Inner Main-belt asteroids (yellow), 99942 Apophis (light grey orbit) and 65803 Didymos (blue orbit), among some planets of the solar system shown along with their orbits (dark grey). Video credit: ESA / PDO / NEOCC.

Along with the OVT, the NEO Toolkit features another three brand-new and complementary tools that focus on different aspects of the observation of NEOs:

• The Observation Planning Tool (OPT) provides the users with precise ephemerides and observational data from NEOs to help them to plan and schedule observations in the forthcoming nights.
• The Sky Chart Display Tool (SCDT) supports the observations by producing a visualisation of the orbits of the NEOs in the sky as observed from any location in the world.
• The Flyby Visualisation Tool (FBVT) offers a high accuracy visualisation of the NEOs that have one or more close approaches to Earth.

Stay tuned for more in-depth information on these three components of the NEO Toolkit. To receive more information about the NEOCC activities and near-Earth objects, you are welcome to subscribe to our services.

Last night at 23:14 UTC NASA's DART spacecraft successfully hit Dimorphos, the moonlet orbiting around near-Earth asteroid Didymos. About 38 seconds later, the time it took for the light to reach Earth, people all over the world saw the abrupt end of the live streaming from the spacecraft, signaling that the impact had happened successfully.

At the same time, astronomers in a small slice of our planet surface, extending from Southern and Eastern Africa to the Indian Ocean and the Arabian Peninsula, could actually watch it live with their telescopes. Among those were a half dozen stations joined together for a dedicated observing campaign organized by our ESA Planetary Defence Office, and coordinated by the team of observers of the NEO Coordination Centre. As usual, when such a timely astronomical event happens, not all stations were successful in their observations: clouds, technical problems and other issues always affect real-life observations. 

However, a few of our collaborating stations could immediately report a successful direct confirmation of the impact. Among them was the team of the Les Makes Observatory, on the French island of La Reunion, in the Indian Ocean. The sequence of images they provided in real time was impressive: the asteroid immediately started brightening upon impact, and within a few seconds it was already noticeably brighter. Within less than a minute a cloud of ejected material became visible, and we could follow it while it drifted Eastward and slowly dissipated.

The emotion of following the event live was the conclusion of weeks of discussions, meetings, accurate planning and observational design by our team, together with the local observers and scientists at all the collaborating stations. A fantastic campaign that produced data that our astronomers, together with the whole DART collaboration, will now begin analysing in order to extract valuable scientific information on the effects of the impact. The results will prepare us for the visit of ESA's Hera spacecraft to the Didymos system to examine the aftermath of the DART's impact a few years from now.

Observations of Didymos during the DART impact. A clear brightnening just after the impact can be observed, followed by a cloud of material ejected from Dimorphos. Credits: Les Makes observatory, J. Berthier, F. Vachier / T. Santana-Ros / ESA NEOCC, D. Föhring, E. Petrescu, M. Micheli

The NEOCC maintains an asteroid image database since 2019. Currently, there are up to 630 thousand images in the database of FITS files. The archive includes images from telescopes such as: ESA’s Optical Ground Station (J04), La Sagra Sky Survey (J75), Klet Observatory (246), Karl Schwarzschild Observatory (033), Calar Alto-Schmidt (Z84), and soon from other observatories cooperating with ESA.

The figure shows the area of the sky covered by the NEOCC image database. All of the available images in the archive have already been analysed to discover or follow-up already known asteroids, and the corresponding astrometric measurements have been submitted to the Minor Planet Center.

The sky covered by NEOCC image database. Credit: ESA / PDO

To access the NEOCC image database users need to use the FITS archive page available here. Through the search form they can find the image(s) by defining the sky area of the interest and/or time range, as well as the source (observatory code or its name). Alternatively, if the name of the image file is already known, the user can employ it to find it in the database as well. In the summary page of a given entry (figure below) the general information about the image and its preview is fully available. However, to download the FITS image itself, the user is required to be logged in first. If you wish to obtain an account for NEOCC portal, please follow the registration instructions in this page.

Alternatively and as of today, the NEOCC image database is linked into the Solar System Object Image Search (SSOIS) system developed by the Canadian Astronomy Data Centre (CADC). Images are searchable and directly accessible through that portal in order to facilitate precovery activities and other research tasks.

Moreover, in order to receive more information about NEOCC activities and near-Earth objects please also subscribe to our services.

Example of the summary page of an image in the database. Credit: ESA / PDO

Just in time for worldwide Asteroid Day: a threatening space rock lingered at the top of risk lists around the globe for months, with 1 chance in 3000 of impacting Earth on 2 April 2052. Now, ESA’s PDO team working with experts at the European Southern Observatory have officially removed asteroid 2021 QM1 from their asteroid risk list. This was a result of skilled observations and analysis of the faintest asteroid ever observed with one of the most sensitive telescopes in the world.

Read the full article here.

Orbit of asteroid 2021 QM1 and relative position at Asteroid Day 2022. Credit: ESA / PDO

(29075) 1950 DA is a kilometre-size near-Earth asteroid discovered on 22 February 1950, observed at that time for 18 days and then lost for 50 years. In January 2001, thanks to an identification with another asteroid discovered in December 2000, (29075) 1950 DA was recovered and observed again.

After collecting high-precision radar measurements in March 2001, a potential impact on 16 March 2880 was detected (see this reference). An impact probability as large as 1 in 300 was computed at that time, corresponding to a maximum Palermo Scale of +0.17.

The estimated impact probability was updated several times since then, last time in 2015 when it reached a value of about 1 in 8000, with a Palermo Scale of about -1.4.

After 6 years, and in agreement with JPL’s Sentry and NEODyS, ESA’s NEOCC decided to update the (29075) 1950 DA risk information by performing the risk assessment taking into account all the measurements available until December 2021. The resulting estimated impact probability in 2880 is approximately 1 in 50 000, and the Palermo Scale value is now about -2.

Ecliptic projection of the trajectory of (29075) 1950 DA. Credit: ESA / PDO

At 19:24 UTC on 11 March 2022, Krisztián Sárneczky discovered a new bright and fast moving object with the 60 cm Schmidt telescope of the Piszkéstető Observatory in Hungary. After collecting 4 observations in quick sequence, at 19:38 UTC he reported them to the Minor Planet Center, with the internal observer-assigned designation of Sar2593.

They were quickly published and used by the various impact assessment systems to estimate the possibility of an impact, which seemed unlikely at that time, with a probability of less than 1%.

In the meantime, he began collecting more observations, and at 20:16 UTC he submitted a second batch of 10 additional measurements, now extending the observed arc to about 40 minutes.

As soon as they were published and picked up by the automatic systems, a completely different scenario became clear. At 20:25 UTC ESA’s own internal monitoring system, called “Meerkat”, triggered an alert to our team, reporting a 100% chance of impact for the object. The expected impact time was between 21:21 and 21:25 UTC, less than an hour later. The impact location was already predictable with an accuracy of about a thousand kilometres, and was located a few hundred kilometres North of Iceland.

In response to this alert, and similar ones quickly distributed by other alert systems, many professional and amateur observers all over Europe and in Asia quickly began observing the imminent impactor. Detecting it was extremely challenging, since the object was already very close (less than 50 000 km from the Earth) and moving very fast in the sky.

Another observatory from Slovakia soon reported its successful observations, together with many more detections from the original discoverer. When added to the trajectory computation, they pinpointed the location of the impact with a precision of just a few seconds and kilometres: the asteroid was going to enter the upper layers of our atmosphere roughly 140 km South of the Jan Mayen island, at 21:22:42 UTC, less than 2 hours after being discovered. From its observed brightness, the object appeared to be very small, roughly a metre in diameter.

In the few minutes just before impact more observatories obtained detections, including a last set at 21:10 UTC, by our collaborators of the Kleť Observatory. Shortly after the expected time of impact the Minor Planet Center designated the asteroid as 2022 EB5, the fifth known impactor observed in space before hitting our planet, and the first discovered from Europe.

Some cameras on the Norwegian island of Jan Mayen (900 km from the coast of Norway) recorded at least the flash of light from the incoming object. No visual evidence has arrived from Iceland, located roughly 700 km away from the impact point, probably because of to low-altitude clouds.

Nevertheless, there is independent evidence that the impact did in fact occur thanks to the international network of infrasound detectors. Signals from the impact were detected from Iceland and Greenland, suggesting an energy release equivalent to 2 to 3 kt of TNT. This is more than what would have been expected from a metre-sized impactor, and pointed to a likely larger diameter of 3 to 4 metres. The discrepancy is likely the result of the measurement uncertainties in both the optical observations and the infrasound detections.

Predicted impact point and time computed by ESA’s imminent impactor alert system “Meerkat” at 20:25 UTC, with the initial 14 observations. The impact location was later refined with more observations, and proved correct. Credit: ESA / PDO

Asteroid 2022 EB5 detected by the Kleť Observatory at 21:10 UTC, less than 13 minutes before it impacted the Earth. Credit: Kleť Observatory

Initial observations of asteroid 2022 AE1 showed a potential Earth impact on 4 July 2023 – not enough time to attempt deflection and large enough to do real damage to a local area should it strike.

Worryingly, the chance of impact appeared to increase based on the first seven days of observations, followed by a week ‘in the dark’ as the full Moon outshone the potential impactor, ruling out further observations. As the Moon moved aside, the skies dimmed and ESA’s Near-Earth Object Coordination Centre (NEOCC) took another look, only to find the chance of impact was falling quickly and finally disappearing. It has since been confirmed that 2022 AE1 will not impact Earth in the next 100 years and has thus been removed from ESA’s risk list.

Read the full story behind this here.

Screenshot of ESA’s risk list on 20 January 2022, last day that 2022 AE1 was in the top position. Credit: ESA / NEOCC.

Until a few days ago, asteroid 2009 JF1 was present in the top-10 ranking of our risk list, for a possible impact on 6 May 2022. It is a small object, only about 10 m in diameter, and therefore the possible impact was not of significant concern. However, its probability of 1 in 4000 made it one of the most likely predicted events in our risk list, and together with its approaching impact date attracted our attention for further investigation.

As the designation suggests, this object was discovered back in 2009. It was first found by the NASA-funded Catalina Sky Survey's Mt. Lemmon Station in Arizona on 4 May of that year, and followed up the next day by the same survey's Southern station in Siding Spring.

Unfortunately, nobody else detected the object back then, nor at any later time; in fact, the timespan between the first and last observation was less than 30 hours, and resulted in a poor knowledge of the object's orbit that made the object effectively lost just a few weeks after discovery. These circumstances prevented observers from improving the orbit in either of the two classical ways, i.e. via new observations or via precovery searches: there was no way to know where the object was located any other time except for the few days around the time of discovery.

In order to assess the situation more clearly, thanks to the support of the Catalina team, we were able to retrieve the original FITS images exposed by their two telescopes at the time. This gave us the possibility to re-measure them astrometrically with tools available today, and in particular using ESA’s Gaia catalogue as source of reference stars. Gaia’s exquisite astrometric precision allowed us to extract more accurate measurements of the object’s position in 2009. Even more importantly, it was now possible to assess the accuracy of our positional measurements to a much better level, thanks to Gaia’s unbiased determination of our reference systems in the sky.

This new information, extracted from existing data but with new tools that were not available at the time, was then used by our team to reassess the impact risk posed by 2009 JF1. The results were interesting: the impact probability for May dropped to just 1 in 1 700 000, and the asteroid has now lost its prominence in our risk list, and is relegated together with other more routine objects that pose minimal threat.

This experiment proves the importance of an astrometric catalogue like Gaia, and of a proper determination of measurement uncertainties, in the context of solar system dynamics. It also shows how essential it is to preserve and properly archive original observational data for posterity, since they can provide information that was not usable at the time of acquisition, but becomes crucial at a later time.

The plots in the figure show the coordinate of the Earth on the plane of the ecliptic (at the origin) and the possible positions of the asteroid, for the time of the predicted impact. Points within the 1-sigma uncertainty region are given in red, the 2-sigma in yellow and the 3-sigma in green. The scale of the axes is expressed in Earth radii. The left plot refers to the old solution, before the remeasurements; the cloud of points clearly passes through the reference system origin (thus impacting the Earth). The right plot corresponds to the new solution after the remeasurements; its smaller uncertainty now shows no impacting solutions within the 3-sigma boundary. Credit: ESA / NEOCC.