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(7482) 1994PC1
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The ESA S2P-NEO Coordination Centre has released a Close Approach Fact Sheet (CAFS) for asteroid (7482) 1994PC1, passing by Earth on 18 January. 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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January 2022
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The ESA SSA-NEO Coordination Centre has released the January 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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Automated data access to ESA's NEOCC portal
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Back in October 2019, a dedicated section was added to ESA’s NEOCC Web Portal, where automated access to several of the system services and data was described. Since then, this functionality was expanded to cover most of the services provided at the recently refurbished NEOCC portal, released in March 2021.

Some of the latest additions to this page include the following new features:

  • A catalogue of all NEAs and their orbital elements (close to the current date and in the middle of the observational arc)
  • A catalogue of all close approaches of NEAs to Earth from 1950 until 100 years from now
  • Asteroid physical properties
  • Several format changes to the provided ephemerides file in the asteroid pages

NEOCC encourages you to make use of these data to develop or to support your NEO-related projects.

For up-to-date information on new additions to the portal and the portal situation at any moment, please regularly consult our “System Status” page.

View of the “Automated Data Access” page in the NEOCC web portal. Credit: ESA / NEOCC.

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Automated data access to ESA's NEOCC portal
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Back in October 2019, a dedicated section was added to ESA’s NEOCC Web Portal, where automated access to several of the system services and data was described. Since then, this functionality was expanded to cover most of the services provided at the recently refurbished NEOCC portal, released in March 2021.

Some of the latest additions to this page include the following new features:

  • A catalogue of all NEAs and their orbital elements (close to the current date and in the middle of the observational arc)
  • A catalogue of all close approaches of NEAs to Earth from 1950 until 100 years from now
  • Asteroid physical properties
  • Several format changes to the provided ephemerides file in the asteroid pages

NEOCC encourages you to make use of these data to develop or to support your NEO-related projects.

For up-to-date information on new additions to the portal and the portal situation at any moment, please regularly consult our “System Status” page.

View of the “Automated Data Access” page in the NEOCC web portal. Credit: ESA / NEOCC.

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Inauguration of the new NEOCC facilities
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On 11 October 2021, the new offices of ESA’s NEO Coordination Centre (NEOCC) were inaugurated, in the presence of high-level authorities of ESA, the Italian Space Agency, and the Italian government. The Centre, firstly inaugurated in 2013, is now operating from a completely renovated building inside ESRIN, ESA’s Italian centre located in Frascati, near Rome.

The NEOCC will serve as the “nerve centre” of ESA’s Planetary Defence Office. The building will host the offices of the majority of the team members, working on the various pillars of the programme, including observations, orbit determination and impact monitoring.

The new building is an important addition to enhance the size, expertise and capabilities of the team, as they work together to provide their scientific and technical expertise to the topic of NEO monitoring and threat prevention.

The activities of the Centre cover a variety of topics essential to characterise the asteroidal impact threat: from the collection of new observations using many worldwide telescopic resources available to the Programme, to the use of these observations to refine our knowledge of the orbits of the most dangerous NEOs, and predicting possible future collisions with our planet.

The study of NEOs is a highly collaborative scientific field. The NEOCC therefore also serves as a repository for European data, knowledge and information, making it accessible to users in Europe and worldwide. At the same time, our scientists and researchers participate in worldwide collaborations on the topic, including international observing campaigns, and continuous comparisons of the impact monitoring results with NASA and their respective teams.

Recent events, such as the Chelyabinsk impact in 2013, and the multiple fireball events detected almost every night across Europe, demonstrate that asteroids are a continuous threat to our planet. ESA’s Planetary Defence Office, and its NEOCC team in Frascati, will continue to operate and grow to effectively provide Europe’s contribution to this important topic of global interest and relevance.

For more information, please check the ESA press release.

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'Oumuamua: the first interstellar object found in our Solar System
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On 19 October the Pan-STARRS telescope, one of the NASA-funded surveys dedicated to discovering new NEOs, found an object that proved to be extremely unique: for the first time, an asteroid originated around another star had been spotted when transiting inside our Solar System. The object, first labelled P10Ee5V by the discovery team, was quickly followed up by a few observatories, including by our team using the ESA Optical Ground Station in Tenerife. When combining our follow-up observations with the discovery data from Pan-STARRS, and with additional prediscovery observations also located by the Pan-STARRS team, we immediately noticed something strange: the only way to fit all data together was to assume that the object had an orbit with an eccentricity greater than 1, meaning it was in an unbound hyperbolic trajectory that proved to be extremely unique: for the first time, an asteroid originated around another star had been spotted when transiting inside our Solar System. The object, first labelled P10Ee5V by the discovery team, was quickly followed up by a few observatories, including by our team using the ESA Optical Ground Station in Tenerife. When combining our follow-up observations with the discovery data from Pan-STARRS, and with additional prediscovery observations also located by the Pan-STARRS team, we immediately noticed something strange: the only way to fit all data together was to assume that the object had an orbit with an eccentricity greater than 1, meaning it was in an unbound hyperbolic trajectory.

Comets in slightly hyperbolic trajectories appear in our Solar System quite often, but usually have eccentricities just a bit larger than 1. These are actually normal Solar System comets, coming near the Sun on a highly elliptical trajectory, and then perturbed by our planets into an orbit that is slightly hyperbolic. The most extreme example of such an object was comet C/1980 E1 (Bowell) which, while coming in from the outer edge of our Solar System, had a close approach with Jupiter that changed its eccentricity to 1.057.

However, P10Ee5V was clearly different. The eccentricity was higher, about 1.2, and no close encounter with any known planet had happened during its entry into the inner Solar System. The trajectory suggested it was an object coming into our system from outside, entering with a velocity of about 26 km/s. It was the first known example of an interstellar object visiting our planetary system. Additional observations collected over the next few days confirmed this conclusion, and the object was quickly announced as a comet with the designation C/2017 U1 (PANSTARRS). However, deeper observations confirmed that the object was not active, and should not have been designated as a comet but as an asteroid, leading the MPC to reclassify it as such assigning a variant asteroidal designation in the cometary system, A/2017 U1. A few days later, following a suggestion from the discovery team, the object received the permanent name 'Oumuamua, a Hawaiian composite word suggesting the idea of a messenger coming first from afar. The International Astronomical Union also introduced a new system to designate interstellar objects using the uppercase letter "I", and 'Oumuamua became the first object in this designation scheme with the full designation 1I/'Oumuamua.

Follow-up images of 1I/'Oumuamua as seen by ESA's OGS telescope on 19 October, just 13 hours after discovery. The object is the faint point-like source with roughly horizontal motion visible near the centre of this 5-frame animation. It is overlapping a star in the first image of the sequence. Credits: ESA NEOCC / D. Abreu (Ataman Science), M. Micheli (ESA), D. Koschny (ESA), M. Busch (Starkenburg Observatory), E. Schwab (Taunus Observatory) and A. Knöfel.

Over the next few days detailed observations of the asteroid were collected using some of the largest telescopes in the world, including ESO's VLT. They showed two main characteristics of the object: its colour was extremely similar to a normal asteroid coming from the outer part of our Solar System, but its shape was quite exceptional. The asteroid showed a rotational lightcurve with an amplitude of almost 2.5 magnitudes, which implies a ratio of approximately 10:1 between the longest and shortest dimension of the object. It was one of the most elongated asteroids ever seen. All these results, and a detailed analysis of this exceptional object, have recently been announced in a paper published on the journal Nature, which can be accessed at https://www.nature.com/articles/nature25020.

At the same time, additional astrometric observations led to further improvements in the orbit, which led to a more accurate computation of its original motion in the galaxy before the encounter with the Sun. The object came from the direction of the constellation Lyra, not far from where the bright star Vega is currently located. However, it could not have originated from Vega itself, because the motion of the star was such that it was not in the right direction when the asteroid was at its distance from the Earth. We still don't know in which system 'Oumuamua was born: its velocity is well aligned with the predominant motion of other stars in the local arm of the Milky Way, and it's therefore difficult to pinpoint a specific one as the origin.

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Record breaking Atira recently discovered
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A newly discovered asteroid has broken many records in our Solar System. The object, now designated 2021 PH27, was discovered by Scott Sheppard on 13 August 2021, using the wide-field DECam imager mounted on the 4-metre Blanco Telescope at Cerro Tololo.

What makes this asteroid really unique is its extremely small orbit, and short orbital period. It orbits the Sun in less than 4 months (115 days to be precise), surpassed among the known objects only by planet Mercury with its 89 days. The semiaxis of its orbit is consequently the smallest among the known asteroids, at 0.46 au.

A direct consequence of its orbit is its challenging observability. It always remains very close to the Sun, and therefore can only be observed from Earth during very short time windows around local twilight. Also, its location in the sky makes it almost unobservable from the Northern Hemisphere, with Southern tropical locations being favoured. Because of these constraints, only less than 5 days of observations had been initially obtained, resulting in a poorly determined orbit that would have made a recovery during the next apparition quite challenging.

In order to improve the situation, we attempted a follow-up observation of the object on 30 August, twelve days after the latest reported astrometric measurement. The object was detected with a 36 cm telescope in Namibia, operated by the 6ROADS team. At a latitude of 23° South of the equator, its location is ideal for this particular object, and allowed us to detect it at an elevation of 18° above the local horizon, while at a solar elongation of just 33°.

Adding the corresponding astrometry to the orbital solution leads to an improvement of the uncertainties on all orbital elements of about an order of magnitude. The uncertainty of its sky position during the next apparition, in 2022, is similarly improved, going from a few degrees to just a few arcminutes, and ensuring that the object will likely not be lost in the future.

Image of 2021 PH27 observed with the 6ROADS SpringBok telescope on 30 August 2021. The image is a composite of 34 individual exposures, stacked on the motion of the object, for a total integration time of 17 minutes. Credit: ESA / 6ROADS, M. Gedek, R. Reszelewski, M. Zolnowski.

Ecliptic projection of the orbit of 2021 PH27 and the inner Solar System planets on 30 August 2021. The highly eccentric orbit of this Atira can be clearly observed as well as the observation geometry at that epoch. Credit: ESA / NEOCC.

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A new ESA telescope in La Silla
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As part of its Space Safety Programme, ESA has developed two 56 cm fully robotic telescopes, called Test-Bed Telescopes (TBTs). Their main scope is to be used as a test platform for the NEO survey strategy and data processing that will be carried out by the upcoming Flyeye telescope. In fact, despite the small aperture, each telescope is particularly suited for survey activities thanks to its 2.5°×2.5° field of view, entirely covered by a monolithic detector.

The first TBT was installed in 2015 at ESA's radio tracking station in Cebreros, Spain. The second TBT has been installed in the past weeks at La Silla observatory in Chile.

During the installation campaign, first light for the telescope was gathered. Despite still being in a very early commissioning phase, the telescope is already showing its promising capabilities, thanks to the excellent sky quality at La Silla. A single two-minute exposure reached a limiting magnitude of about 20.2, and a stack of five such frames was sufficient to detect stellar sources fainter than magnitude 21.

Once fully operational, the two telescopes will be used for survey and follow-up activities, shared between ESA's Planetary Defence Office and the Space Debris team.

For more information check the ESA press release and the ESO press release.

Caption: full field-of-view and close-up view of Centaurus A as observed during TBT's first light tests in La Silla. Credits: ESA / NEOCC.

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Going faint
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Meter-class telescopes, such as ESA's own Optical Ground Station in Tenerife, are usually capable of observing objects as faint as magnitude 22 or so. This is the typical limiting magnitude that can be reached in less than an hour of exposure time, under dark and clear conditions.

However, it is of course possible to push the capabilities of these systems to much fainter magnitudes, if we can devote sufficient time to a single observation. This is what we recently did with the 0.8-metre Schmidt telescope at Calar Alto, when we tried to observe an object that was predicted to have a visual magnitude of approximately 23.5.

We obtained about 200 images of the asteroid's location, 90 seconds each, from the time it rose above an altitude of 30° in the evening, to when it set below the same limit in the morning. We then combined them together in a stack, using the known motion of the target asteroid.

The result was a clear, albeit faint, detection of the object. When the detected source was measured photometrically, we discovered that the object was actually fainter, with a measured visual magnitude of about 24.2. This observation was also obtained under poorer-than-average seeing conditions, approximately 2.5". On a night with a better seeing it should be easily possible to reach an even fainter limiting magnitude.

This unusual mode of operation for a small-class telescope could offer interesting follow-up opportunities for faint objects, that are typically only observed with larger professional facilities.

Caption: Plain stack of the images (left), and the same stack processed to enhance the target and remove background sources (right). The object is visible at the centre of the red box. Stacks produced using Tycho. Credits: ESA NEOCC

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A brand-new face for the NEOCC web portal
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Our web portal was first released in 2012, even before the inauguration of our NEO Coordination Centre at ESRIN in May 2013. At that time, a first version of the portal was released by federating NEO services that were already operating (NEODyS, AstDyS, EARN, priority list, etc.). This was complemented with a suite of graphical tools and databases in order to render a first web service available.

In April 2015, and after the Planetary Defense Conference was held at ESRIN, we started producing our monthly newsletter, which has become one of our outreach flagship. In August 2017, we started releasing the close approach fact sheets (CAFS) to provide detailed information of relevant NEA approaches with the Earth.

After many improvements and additions performed to the portal through the years, we are happy to announce the release of a brand-new version of our portal based on present web technologies. We hope that the incorporation of these technologies will enhance the user experience of our portal while still providing easy access to the contents that we produce in our daily operations.

Snapshot of the old NEOCC web portal as of February 2013.

 

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Apophis removed from the risk list
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New optical observations of Apophis have been collected since end of October 2020. In addition to that, the acquisition of new radar observations in early March by NASA’s Goldstone Deep Space Communications Complex in California and the Green Bank Observatory, West Virginia, have provided enough data on the orbit of the infamous asteroid to finally rule out, with certainty, any Earth impact for at least 100 years.

For more information, please read ESA’s press release here.

In addition to that, recent Apophis stellar occultation observations have allowed constraining the Yarkovsky acceleration to even more accurate values than the ones reported by us here. For more information please read Gaia’s Image of the Week entry here.

Caption: Earth's gravity will notably alter Apophis' orbit during 2029 flyby.

 

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Learning from lunar lights
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Every few hours observing the Moon, ESA’s ‘NELIOTA’ project discovers a brilliant flash of light across its surface – the result of an object hurtling through space and striking our unprotected rocky neighbour at vast speed. Based at the Kryoneri telescope of the National Observatory of Athens, this important project is now being extended to January 2021.

From the Moon’s past, to Earth’s future

For this reason scientists are studying lunar flashes with great interest, not only for what they can tell us about the Moon and its history, but also about Earth and its future.Impact flashes are referred to as ‘transient lunar phenomena’, because although common, they are fleeting occurrences, lasting just fractions of a second. This makes them difficult to study, and because the objects that cause them are too small to see, impossible to predict.

By observing lunar impacts, NELIOTA (NEO Lunar Impacts and Optical TrAnsients) aims to determine the size and distribution of near-Earth objects (NEOs) – meteoroids, asteroids or comets. With this information, the risk these space rocks pose to Earth can be better understood.

The world’s largest eye on the Moon

In February 2017, a 22-month campaign began to observe lunar flashes with the 1.2 metre Kryoneri telescope, the largest telescope on Earth to monitor the Moon.

The flashes of light caused by lunar impacts are far dimmer than the sunlight reflected off the Moon. For this reason, we can only observe these impacts on the Moon’s ‘dark side’ – between New Moon and First Quarter, and between Last Quarter and New Moon. The Moon must also be above the horizon, and observations require a fast-frame camera, such as the Andor Zyla sCMOS used in the NELIOTA project.

To date, in the 90 hours of possible observation time that these factors allowed, 55 lunar impact events have been observed – a detection rate of about 2x10-7 flashes per hour, per square kilometre. Extending this to the entire surface of the Moon gives a final rate of almost 8 flashes per hour. With the extension of this observing campaign to 2021, further data should improve impact statistics.

The NELIOTA system is the first to use a 1.2-metre telescope for monitoring the Moon, and as such is able to detect flashes two magnitudes fainter than other lunar monitoring programs, which typically use 0.5-metre telescopes or smaller.

Another unique feature of the NELIOTA project is its ability to monitor the Moon in two ‘photometric bands’, which recently enabled the first-ever refereed publication to determine the temperature of lunar impact flashes – ranging from 1300 to 2800 C.

A modern approach to an ancient phenomenon

For at least a thousand years, people claim to have spotted flashes lighting up regions of the Moon, yet only recently have we had telescopes and cameras powerful enough to characterise the size, speed, and frequency of these events.

While our planet has lived with the risk, and reality, of bombardment from objects in space for as long as it has been in existence, we are now able to monitor our skies with more accuracy than ever before.

The NELIOTA project relies on funding from ESA’s Science programme, and is one exciting part of ESA’s Space Situational Awareness programme, which is building infrastructure in space and on the ground to improve our monitoring and understanding of potential Earth hazards.

The programme is currently in the process of setting up a network of Flyeye telescopes across the globe, to scan the skies for risky asteroids, including those that could hit the Moon.

In the future, ESA will move towards mitigation and active planetary defence, and is currently planning the ambitious Hera mission to test asteroid deflection.

Read more at the NELIOTA programme: https://neliota.astro.noa.gr/.

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ESA NEO and Debris Detection Conference - Exploiting Synergies
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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,
Rüdiger Jehn and Tim Flohrer
Ruediger.Jehn@esa.int | tim.flohrer@esa.int
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.

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2018 GE3: a late-detected visitor in the Earth's neighbourhood
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At approximately 09:30 UT on 14 April 2018 the Catalina Sky Survey, in Arizona, discovered a bright magnitude 15 object moving at a sky speed of 10" per minute, in the constellation Libra.

Follow-up observations obtained over the next few hours, by Catalina's own facilities and by other observers in the US Southwest, quickly showed that this was an unknown asteroid, which was about to have a close fly-by with our planet less than a day later. The asteroid was subsequently designated 2018 GE3.
It is not very unusual for small asteroids to be discovered just a few hours before close approach. However, what made this discovery quite unique is that this object was much bigger, having an estimated diameter between 50 m and 100 m.

The fly-by of 2018 GE3 happened around 06:40 UT on 15 April, at half the distance of the Moon. It reached magnitude 12 just before the closest approach, and then went towards the direction of the Sun, becoming unobservable from the ground.
The fly-by was one of the closest ever recorded for an object of this size. The only other object of comparable (or slightly larger) size that was seen coming closer was 2002 MN: it flew-by at just 0.3 lunar distances on 14 June 2002. It was discovered only three days before by the then-active LINEAR survey.

How is it possible that an object of this size, coming from the dark side of the sky, could be missed by all asteroid surveys until less than a day before the close passage? The reasons can be found in the "geometry" of the approach trajectory that was quite unfortunate for a variety of reasons. 

- The asteroid became brighter than magnitude 22.5 (the typical limit of large surveys like Pan-STARRS1) on 31 March, only two weeks before its fly-by. This time interval, unusually short for object of this size, is due to its higher-than-average incoming radial speed of ~30 km/s. Objects of the same size, on a more typical and slower NEO orbit, can become visible a couple of weeks earlier. However, they may not necessarily move in a way that makes them recognizable as NEOs that early on, so the actual warning time may be shorter.

Sky Coverage plot prepared with the Minor Planet Center's tool (https://minorplanetcenter.net/iau/SkyCoverage.html) for the timespan between 2 and 13 April 2018, and including only the deeper surveys. The approximate path of 2018 GE3 during the same time period is marked by the red arrow. The Pan-STARRS1 survey (dark blue) came close to the right position on 12 April, but stopped too far South. The Catalina Sky Survey's largest telescope, the 1.5-meter at Mt. Lemmon (purple), was observing mostly North of the equator for the same two weeks. Credits: Minor Planet Center

- More importantly, at that time the object was only 30° away from the fully illuminated moon, making it effectively unobservable. It got even closer to the moon for the next two days, and reached a sufficient distance from it only around 7 April.

- Also, one of the main asteroid discovery telescopes, the Pan-STARRS1 survey, was not operational due to poor weather until 12 April, and therefore did not cover the area of the sky where 2018 GE3 was located.

The currently existing surveys, especially those capable of reaching the faint limiting magnitude needed to detect 2018 GE3 early on, have the capability to cover the entire observable night sky only every few weeks. It is therefore possible for an object like this to "slip" though their monitoring pattern and come close to our planet unannounced.

This underlines the importance and also the potential of the Fly-Eye Telescope which is currently built in Italy under ESA contract. It will have a very large field-of-view of 6.7 x 6.7 square degrees, which allows to scan one complete hemisphere in 48 hours. Putting one fly-eye telescope in the Northern and one in Southern hemisphere will provide a global coverage. Asteroids like 2018 GE3 should then be detected with at least one week of warning time, sufficient to make a reliable estimate of a possible impact area and to initiate adequate precaution measures.

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An archival precovery
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During the first month of 2018 two objects reached a Torino Scale level of 1, and attracted the attention of observers with the goal of collecting additional observations necessary to remove the possible risk. One of them 2017 YZ1, was removed from the risk list within a few days thanks to new observations of various observers, including David Tholen from Hawaii, and our team working in collaboration with the OASI telescope in Brazil.

The other object, 2017 XO2, was harder to remove. By the time it reached Torino Scale 1 it was already quite faint, at magnitude 24, and difficult to observe for most telescopes. There was however another way to get the data needed to clarify the risk: we realised that the Pan-STARRS archive contained a significant amount of images obtained in November and December 2011 that should have covered the area where 2017 XO2 was located, and at that time the object was much brighter, around magnitude 20.

There was a problem however: the uncertainty of the asteroid's position in the sky was huge, many degrees long. Still, we decided to analyse all the dozens of images from one of the many detectors where the object could have been, and after many hours of careful searches we were able to locate the object in the November 5 image set, about 2 sigma away from the expected position.

These images then allowed us to find it in all the other sets from that year, for a total of nine good detections. None of them had been found by the automated Pan-STARRS system because there were only two detections for each night, while automated algorithms need at least three to safely identify a new moving object. Adding these observations to the orbit computation resulted in the immediate exclusion of all possible impact dates for the next century, and the object went directly from Torino Scale level 1 to a complete removal from our risk list.

 

Animation of two images of 2017 XO2 taken on 2011 November 25 by the Pan-STARRS telescope. The two images were exposed approximately 18 minutes apart, and the object is visible in the top half of the image. Credit: Pan-STARRS

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A large fast-rotating asteroid
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A few weeks ago the Pan-STARRS survey discovered a new NEO, temporarily identified as P10G8tt and then formally designated 2018 AM12. Follow-up observations over the next few days allowed the determination of its distance, and consequently its absolute magnitude, which turned out to be roughly 21.4. This brightness should correspond to a diameter between about 150 m and 300 m, depending on the unknown albedo of the object's surface.

A few days later one of our collaborators, Erwin Schwab, was using the 0.8-metre Schmidt telescope in Calar Alto, Spain, to collect observations of the asteroid, while he noticed that the object was an extremely fast rotator, with a rotation period of roughly 12.5 minutes. He collected data over about two hours, which resulted in the lightcurve shown in the figure below.

This fast period is unusual for an object of this size, since it is known that almost all objects larger than ~200 m tend to have periods longer than 2 hours (the so-called spin barrier).

The object is now approximately of magnitude 20, but it is getting fainter quite fast. Obtaining a taxonomical classification of it, or any other proxy for its albedo, would allow us to determine its actual size more accurately. If the object turns out to be larger than the spin barrier, it would be interesting to investigate its physical properties in greater detail.

The results of these observation have been submitted for publication to the Minor Planet Bulletin

Lightcurve of 2018 AM12 obtained on 2018 January 16 with the Calar Alto Schmidt telescope, phased with the detected rotational period of 12.64 minutes. Credit: E. Schwab

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Observations of the OSIRIS-REx Spacecraft
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As part of an international observing campaign, the OSIRIS-REx spacecraft has been imaged during our normal monthly observing run on 16 September with the OGS telescope in Tenerife. In the attached image one can observe the OSIRIS-REx spacecraft as the tiny point at the centre of the image moving from left to right. The larger spot moving in the same direction, but located more to the left, is main belt asteroid (50587) 2000 ET45.

Image of OSIRIS-REx spacecraft. Credit: ESA NEOCC / D. Abreu (Ataman Science), M. Micheli (ESA), D. Koschny (ESA), M. Busch (Starkenburg Observatory), E. Schwab (Taunus Observatory) and A. Knöfel.

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Approaching Asteroid
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An international campaign has revealed that an asteroid will come within 44 000 km of our planet in October, providing a rare opportunity for intensive studies.

Astronomers recently spotted asteroid 2012 TC4 under a collaboration between ESA and the European Southern Observatory (ESO) to locate faint objects that might strike Earth. This is the first observation since 2012, when the asteroid was discovered by the Pan-STARRS observatory in Hawaii. It was found this time by ESO's Very Large Telescope in Chile.

The original observations revealed the asteroid's next approach to our vicinity would be in October 2017 but its orbit meant that it could not be tracked during the last five years, leaving astronomers unsure on how close it would come.

The new observations reveal it will miss Earth by 44 000 km. While it remains visible, astronomers will study the 15–30 m object in as much detail as possible, such as obtaining information on its composition.

An asteroid of this size entering our atmosphere would have a similar effect to the Chelyabinsk event. The 2012 TC4 Observing Campaign is part of a larger international initiative led by NASA. The campaign is an excellent opportunity to test the international ability to detect and track near-Earth objects and assess our ability to respond together to a real asteroid threat.

Recovery image of 2012 TC4. Credit: ESO / ESA NEOCC / O. Hainaut (ESO), M. Micheli (ESA) & D. Koschny (ESA)

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NELIOTA: ESA's new lunar monitoring project in collaboration with the National Observatory of Athens
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Credit: J. Madiedo / MIDAS
NELIOTA is an activity initiated by the European Space Agency (ESA), which was recently launched at the National Observatory of Athens. The project aims to count and characterise the number and distribution of near-earth objects (NEOs). NEOs are meteoroids, comets or asteroids found in the neighbourhood of the Earth. Large NEOs can pose a threat to humans, as some have the potential to impact the Earth. The Earth's atmosphere protects us from impacts of small NEOs, most of which burn up as they enter the atmosphere at great speeds. Only the largest ones have the potential to reach the surface. On the Moon, however, the absence of an atmosphere means that all NEOs that enter the Moon's gravity will impact the surface. Impacts on the non-illuminated side of the Moon cause a visible flash that lasts about 1 second and results in a crater. Scientists are interested in understanding the size distribution and frequency of NEOs in order to assess the threat of small NEO collisions to orbiting spacecraft and to future ESA Moon missions.
 
The NELIOTA project will use existing facilities at the National Observatory of Athens to establish an operational system that will monitor the Moon, looking for faint NEO impacts. The project involves upgrading the 1.2m Kryoneri telescope, located in the Northern Peloponnese, in Greece, as well as procuring two specialised fast-frame cameras. Specialised software will be developed to control the telescope and cameras, as well as process the resulting images to detect the impacts automatically. The NELIOTA system will then publish the data on the web so it can be made available to the scientific community and the general public.
 
The objective of this three and a half year activity is to design, develop and implement a highly automated lunar monitoring system. The system will conduct an observing campaign for 2 years searching for NEO impact flashes on the Moon. The impact events will be verified, characterised and recorded. The 1.2m Kryoneri telescope will be capable of detecting flashes far fainter than telescopes currently monitoring the Moon. It is expected that NELIOTA will be able to record NEOs weighing just a few grams.
 
This activity is being undertaken by a team led by Dr. Alceste Bonanos at the Institute for Astronomy, Astrophysics, Space Applications & Remote Sensing at the National Observatory of Athens, Greece. The upgrade of the 1.2m Kryoneri telescope will be undertaken by DFM Engineering, Inc. The project website can be found here.
 
This project forms part of many activities initiated and/or sponsored by the European Space Agency to help have a better understanding of our Space environment. In parallel to this exciting new venture, the Agency is also examining our space weather and the detrimental impact of space debris.
 

CREDIT: J. Madiedo / MIDAS

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The 2016 WJ1 precoveries: back to the future
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The word "precovery" has entered the astronomical jargon rather recently but it quickly grew in popularity among asteroid hunters. It refers to the finding of an archival observation of an object which was not recognized as such because the corresponding image originally served other purposes. Hence the name "precovery", which explains why we may have direct measurements of an asteroid position at a time well ahead its discovery date. Searching for precoveries is a powerful technique for NEO impact monitoring. It allows to extend the observational arc of an object leading often to a dramatic improvement in its orbit knowledge without the need of additional telescope time. Although extremely rewarding, it is a tricky business which requires peculiar skills. The past trajectory of the asteroid (including uncertainties) must be assessed in order to start searching and retrieving candidate images from astronomical databases all over the world. A careful inspection looking for a faint spot close enough to the expected location is then carried out.

The case for 2016 WJ1 is no exception, but with a further taste of complexity: a chain of precoveries brought the NEO Coordination Centre to catch a view of the asteroid position as far back as July 2003. 2016 WJ1 was discovered on 19 October 2016 by the Catalina Sky Survey. When impact monitoring systems were run , the object turned out to be rather peculiar, with more than 200 dates within the next century when an impact could not be excluded with certainty. However, the highest probability for any of these events was quite low, about 1 in 80 000.

The left panel shows the 2003 precovery image of 2016 WJ1: the asteroid appears a faint spot between two bright stars. The right panel shows the orbit of 2016 WJ. The orbit of 2016 WJ is rather peculiar, having both nodes very close to the Earth orbital radius. The position of the Earth and of the asteroid corresponds to the 2037 encounter, formerly an impact solution.

Over the following days new observations were collected and when the impact predictions were recomputed some of the possible dates were discarded, but others became associated to a higher hazard. In particular, a possible close approach in June 2065 was now showing an impact probability of about 1 in 8000, enough to classify an object of this size at level 1 of the Torino scale (out of 10 levels).

The left panel shows the behaviour of the impact probability over time for two possible impact dates and its cumulative value (blue area). Note the steady increase and the almost sudden drop to a value difficult to appreciate in the scale of the plot, after the 2003 precovery observation was found. The right panel shows how the accuracy with which the 2016 WJ1 semimajor axis was known, increased with the length of the observed arc, significantly extended by precoveries.

Usually additional follow-up observations are likely to remove the possible threat, but for 2016 WJ1 this was not the case. Those collected during the subsequent week, including some from our team with ESA's OGS telescope in Tenerife, did not significantly change the impact scenario. However, they did improve our knowledge of the asteroid's orbit enough to start searching for precoveries.

The archives of the survey telescope Pan-STARRS revealed a promising set of images taken on 13 October 2016. An extremely faint source was indeed spotted at the expected position, but it was so barely visible to prevent deciding whether it was the footprint of 2016 WJ1 or just a fortunate alignment of noise features. Yet the information was not useless: pretending that the Pan-STARRS detection was true, the asteroid orbit was refined to the point of allowing us to push the search further back in the past - until a couple of decades ago. Were another object to be found following the new predictions, this would confirm that the Pan-STARRS faint detection was indeed correct.

The Canadian SSOIS image search system, one of the most efficient on-line precovery services available, with which the NEO Coordination Centre is collaborating, was used to this end. Two sets of images taken on 4 and 5 July 2003 with the Canada-France-Hawaii Telescope, where the object should have been visible, were retrieved. After careful inspection we were able to locate the object only 4 arcminutes away from the prediction based on the Pan-STARRS detection.Accurate astrometry was promptly extracted from these images and the outcome was lowering the probability associated to possible impact scenarios to safer values.

Following asteroid footsteps backward in time is an exciting game, to which a future development of the ESA SSA-NEO Segment is likely to provide a significant contribution: the deployment of the so-called "Fly-Eye" telescopes. Aimed at NEO discovery they will cover the whole visible sky every night thus making available a huge database which in the long run will greatly increase the chances of carrying out successful precoveries.