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August 2022
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The ESA SSA-NEO Coordination Centre has released the August 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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NEOCC FITS Image Archive now accessible through the SSOIS
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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

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NEOCC FITS Image Archive now accessible through the SSOIS
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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

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Asteroid 2021 QM1 removed from NEOCC’s risk list pole position
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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

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Impact threat analysis update completed for 1950 DA
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(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

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Fifth notch for Planetary Defenders
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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

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Recap on the removal of 2022 AE1 from the risk list
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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.

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2009 JF1 kicked out of the risk list top-ten thanks to observation re-measurements
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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.

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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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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.

News item All news
2018 GE3: a late-detected visitor in the Earth's neighbourhood
operator neo image

operator neo

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.