arXiv subjects

Detlef Koschny

Publications and source records attributed to Detlef Koschny.

At least 19 recordsLinked to original sources

arXiv2026

Twin Impact Lunar Telescope network: Lunar Impact Flash observations of the 2025 Geminids

Meteoroid impacts on the Moon, observed from Earth as flashes typically lasting a few tens of milliseconds, have been monitored for three decades for determining meteoroids' size and mass frequency distribution in the cm to dm range. Studies link these observed impact events to fresh craters advancing our understanding of energy partitioning during an impact. Currently we are transitioning to a new era where lunar impact flashes (LIFs) can be used to supplement upcoming lunar seismology to study the internal lunar structure. Here we present results from the first station of a telescope network under development for continuous LIF monitoring. Observations were carried out during the Geminids 2025 campaign, initiated by the LUMIO Science Team in the framework of their public engagement activities. We detected 53 potential impact flashes and confirmed 11 of them through multiframe observations, and independent detections by other observers. We present evidence suggesting that some of the yet unconfirmed events may be real. Our confirmed events range between magnitude +7.5 and +10.4, primarily in the V and R band. We obtained a high rate of observations per hour, highlighting the importance of high ZHR meteoroid streams for observing LIFs. We also discuss the scientific value of potential LIFs that remain unconfirmed in optical data alone. Even without multi station confirmation, these events can correlate to seismic signals in future lunar seismic networks, thereby providing useful physical constraints on impact processes. This approach would also allow stations equipped with a single telescope/camera to meaningfully contribute to the network.

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arXiv2026

Observational planning for the 2026 August 5 Falcon 9 Upper Stage lunar impact

On 2026 August 5, at approximately 06:35 UT, a spent Falcon 9 upper stage will impact the lunar surface near Einstein Crater. This event will occur on sunlit terrain near the eastern limb as seen from Earth. The impact flash and resultant ejecta plume from this event are potentially observable from ground- and space-based observational facilities. This event provides an opportunity to attempt the recording of an artificial impact in real-time; although many of the properties of the event (such as visual magnitude) are imprecisely predicted at present. Moreover, this event provides an opportunity to test a pipeline for localising impacts on the lunar surface for future seismic experiments, investigating the dust and plume dynamics from impact events on the Moon, and considering hazards from artificial space debris impacts. Both professional and amateur astronomers are encouraged to attempt observations of this event.

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arXiv2026

The ESA Meerkat Asteroid Guard: a monitoring service for imminent impactors

We present the Meerkat Asteroid Guard, an imminent impactor warning service developed and maintained by the European Space Agency's Near-Earth Object Coordination Centre (NEOCC). The software uses the method of systematic ranging to perform orbit determination on tracklets in the Near-Earth Object Confirmation Page (NEOCP), which typically have short observational arcs. Fitted orbits are propagated to determine the likelihood of an impact with Earth. In addition, magnitude fitting and Monte Carlo sampling are performed to estimate the object's size, possible impact locations and times, and suggest a best telescope pointing for object follow-up. A set of object scores are produced from computed posterior probabilities across the grid, giving a statistical description of the object's orbital and physical characteristics. The scores are packaged with several informative plots in an email alert, which is sent to Meerkat subscribers in the event of a significant impact probability, close approach, or other scientifically interesting event. The highlights of the five years of Meerkat's operational service are presented, including the successful warnings for all of the past six imminent impactors discovered before impact and several interesting close approaches.

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arXiv2025

Catastrophic disruption of asteroid 2023 CX1 and implications for planetary defense

Mitigation of the threat from airbursting asteroids requires an understanding of the potential risk they pose for the ground. How asteroids release their kinetic energy in the atmosphere is not well understood due to the rarity of significant impacts. Ordinary chondrites, in particular L chondrites, represent a frequent type of Earth-impacting asteroids. Here, we present the first comprehensive, space-to-lab characterization of an L chondrite impact. Small asteroid 2023 CX1 was detected in space and predicted to impact over Normandy, France, on 13 February 2023. Observations from multiple independent sensors and reduction techniques revealed an unusual but potentially high-risk fragmentation behavior. The nearly spherical 650 $\pm$ 160 kg (72 $\pm$ 6 cm diameter) asteroid catastrophically fragmented around 28 km altitude, releasing 98% of its total energy in a concentrated region of the atmosphere. The resulting shockwave was spherical, not cylindrical, and released more energy closer to the ground. This type of fragmentation increases the risk of significant damage at ground level. These results warrant consideration for a planetary defense strategy for cases where a >3-4 MPa dynamic pressure is expected, including planning for evacuation of areas beneath anticipated disruption locations.

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arXiv2024

The Aegis Orbit Determination and Impact Monitoring System and services of the ESA NEOCC web portal

The NEO Coordination Centre (NEOCC) of the European Space Agency is an operational centre that, among other activities, computes the orbits of near-Earth objects and their probabilities of impact with the Earth. The NEOCC started providing information about near-Earth objects in 2012 on a dedicated web portal, accessible at https://neo.ssa.esa.int/. Since the beginning of the operational phase, many developments and improvements have been implemented regarding the software, the data provided, and the portal. One of the most important upgrades is that the NEOCC is now independently providing data through a newly developed Orbit Determination and Impact Monitoring system, named Aegis. All the data computed by Aegis is publicly available on the NEOCC web portal, and Aegis is also used to maintain all the major services offered. The most important services comprise an orbital catalogue of all known asteroids, a list of possible future impacts with the Earth (also called Risk List), a list of forthcoming close approaches, a set of graphical toolkits, and an on-demand ephemerides service. Many of the services are also available through dedicated APIs, which can be used to automatically retrieve data. Here we give an overview of the algorithms implemented in the Aegis software, and provide a summary of the services offered by the NEOCC that are supported by Aegis.

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arXiv2024

NELIOTA: New results and updated statistics after 6.5 years of lunar impact flashes monitoring

We present results of the NELIOTA campaign for lunar impact flashes observed with the 1.2 m Kryoneri telescope. From August 2019 to August 2023, we report 113 validated and 70 suspected flashes. For the validated flashes, we calculate the physical parameters of the corresponding projectiles, the temperatures developed during the impacts, and the expected crater sizes. For the multiframe flashes we present light curves and thermal evolution plots. Using the whole sample of NELIOTA that encompasses 192 validated flashes in total from 2017, the statistics of the physical parameters of the meteoroids, the peak temperatures of the impacts and the expected crater sizes has been updated. Using this large sample, empirical relations correlating the luminous energies per photometric band were derived and used to roughly estimate the parameters of 92 suspected flashes of the NELIOTA archive. For a typical value of the luminous efficiency, we found that more than the 75% of the impacting meteoroids have masses between 1-200 g, radii between 0.5-3 cm and produced craters up to 3.5 m. 85% of the peak temperatures of the impacts range between 2000 and 4500 K. Statistics regarding the magnitude decline and the cooling rates of the multiframe flashes are also presented. The recalculation of the appearance frequency of meteoroids, lying within the aforementioned ranges of physical parameters, on the Moon yields that the total lunar surface is bombarded with 7.4 sporadic meteoroids/ hour and up to 12.6 meteoroids/hour when the Earth-Moon system passes through a strong meteoroid stream. By extrapolating these rates on Earth, the respective rates for various distances from its surface are calculated and used to estimate the probability of an impact of a meteoroid with a hypothetical infrastructure on the Moon, or with a satellite orbiting Earth for various impact surfaces and duration times of the missions.

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arXiv2023

Lunar impact flash results and space surveillance activities at Kryoneri Observatory

We present current and future activities regarding lunar impact flash and NEO observations and satellite tracking from Kryoneri Observatory. In particular, we present results from the ESA-funded NELIOTA program, which has been monitoring the Moon for impact flashes since early 2017. Using the 1.2 m Kryoneri telescope, which is equipped with two high frame-rate cameras recording simultaneously in two optical bands, NELIOTA has recorded over 170 validated lunar impact flashes, while another ~90 have been characterized as suspected. We present statistical results concerning the sizes, the masses and the appearance frequency of the meteoroids in the vicinity of the Earth, as well as the temperatures developed during the impacts. Moreover, we present the capabilities of the Kryoneri telescope as a sensor for satellite tracking and the future plans regarding the provision of high-quality services for both the Planetary Defense activities of ESA (S2P/PDO) and the European Union's Space Surveillance and Tracking programme (EU/SST).

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arXiv2023

Mining archival data from wide-field astronomical surveys in search of near-Earth objects

Increasing our knowledge of the orbits and compositions of Near-Earth Objects (NEOs) is important for a better understanding of the evolution of the Solar System and of life. The detection of serendipitous NEO appearances among the millions of archived exposures from large astronomical imaging surveys can provide a contribution which is complementary to NEO surveys. Using the AstroWISE information system, this work aims to assess the detectability rate, the achieved recovery rate and the quality of astrometry when data mining the ESO archive for the OmegaCAM wide-field imager at the VST. We developed an automatic pipeline that searches for the NEO appearances inside the AstroWISE environment. Throughout the recovery process, the pipeline uses several public web-tools to identify possible images that overlap with the position of NEOs, and acquires information on the NEOs predicted position and other properties (e.g., magnitude, rate and direction of motion) at the time of observations. We have recovered 196 appearances of NEOs from a set of 968 appearances predicted to be recoverable. It includes appearances for three NEOs which were on the impact risk list at that point. These appearances were well before their discovery. The subsequent risk assessment using the extracted astrometry removes these NEOs from the risk list. We estimate a detectability rate of 0.05 per NEO at an SNR>3 for NEOs in the OmegaCAM archive. Our automatic recovery rates are 40% and 20% for NEOs on the risk list and the full list, respectively. The achieved astrometric and photometric accuracy is on average 0.12 arcsec and 0.1 mag. These results show the high potential of the archival imaging data of the ground-based wide-field surveys as useful instruments for the search, (p)recovery and characterization of NEOs. Highly automated approaches, as possible using AstroWISE, make this undertaking feasible.

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arXiv2023

(523599) 2003 RM: The asteroid that wanted to be a comet

We report a statistically significant detection of nongravitational acceleration on the sub-kilometer near-Earth asteroid (523599) 2003 RM. Due to its orbit, 2003 RM experiences favorable observing apparitions every 5 years. Thus, since its discovery, 2003 RM has been extensively tracked with ground-based optical facilities in 2003, 2008, 2013, and 2018. We find that the observed plane-of-sky positions cannot be explained with a purely gravity-driven trajectory. Including a transverse nongravitational acceleration allows us to match all observational data, but its magnitude is inconsistent with perturbations typical of asteroids such as the Yarkovsky effect or solar radiation pressure. After ruling out that the orbital deviations are due to a close approach or collision with another asteroid, we hypothesize that this anomalous acceleration is caused by unseen cometary outgassing. A detailed search for evidence of cometary activity with archival and deep observations from Pan-STARRS and the VLT does not reveal any detectable dust production. However, the best-fitting H$_2$O sublimation model allows for brightening due to activity consistent with the scatter of the data. We estimate the production rate required for H$_2$O outgassing to power the acceleration, and find that, assuming a diameter of 300 m, 2003 RM would require Q(H$_2$O)$\sim10^{23}$ molec s$^{-1}$ at perihelion. We investigate the recent dynamical history of 2003 RM and find that the object most likely originated in the mid-to-outer main belt ($\sim86\%$) as opposed to from the Jupiter-family comet region ($\sim11\%$). Further observations, especially in the infrared, could shed light on the nature of this anomalous acceleration.

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arXiv2023

Identifying meteorite droppers among the population of bright 'sporadic' bolides imaged by the Spanish Meteor Network during the spring of 2022

The extraordinary weather conditions available between February and March 2022 over Spain have allowed us to analyze the brightest fireballs recorded by the monitoring stations of the Spanish Meteor Network (SPMN). We study the atmospheric flight of 15 large meteoroids to determine if they are meteorite dropper events to prepare campaigns to search for freshly fallen extraterrestrial material. We investigate their origins in the Solar System and their dynamic association with parent bodies and meteoroid streams. Employing our Python pipeline 3D-FireTOC, we reconstruct the atmospheric trajectory utilizing ground-based multi-station observations and compute the heliocentric orbit. In addition, we apply an ablation model to estimate the initial and terminal mass of each event. Using a dissimilarity criterion and propagating backward in time, we check the connection of these meteoroids with known complexes and near-Earth objects. We also calculate if the orbits are compatible with recent meteoroid ejections. We find that ~27% of these fireballs are dynamically associated with minor meteoroid streams and exhibit physical properties of cometary bodies, as well as one associated with a near-Earth asteroid. We identify two meteorite-producing events; however, the on-site search was unsuccessful. By considering that these fireballs are mostly produced by cm-sized rocks that might be the fragmentation product of much larger meteoroids, our findings emphasize the idea that the population of near-Earth objects is a source of near-term impact hazards, existing large Earth-colliding meteoroids in the known complexes.

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arXiv2020

Velocity distribution of larger meteoroids and small asteroids impacting Earth

Various meteor and fireball networks exist worldwide. Most data sets which include ground-based observational data of meteors are affected by biases. The larger and faster the entering meteoroid, the brighter is the produced meteor. Hence, small and slow objects often stay undetected. This bias of meteor observations towards faster meteoroids is a challenge if quantitative population and flux models are derived. In this work the velocity distribution of objects in space is analysed by using different data sets that are not affected by this velocity bias since they include only large objects, like the near-Earth object (NEO) risk list of ESA's (European Space Agency) SSA (Space Situational Awareness) near-Earth object Coordination Centre (NEOCC), and the fireballs in NASA's (National Aeronautics and Space Administration) CNEOS (Center for near-Earth object Studies) JPL (Jet Propulsion Laboratory) fireball database. Additionally, when only the largest objects recorded with the CILBO (Canary Island Long-Baseline Observatory) camera setup were analysed, a very similar distribution was shown. These velocity distributions are in good agreement with a widely used velocity distribution for smaller sporadic meteoroids in free space which was adopted as reference by the ECSS (European Cooperation for Space Standardisation) Space Environment Standard.

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arXiv2020

Luminous efficiency based on FRIPON meteors

In meteor physics the luminous efficiency $τ$ is used to convert the meteor's magnitude to the corresponding meteoroid's mass. However, lack of sufficiently accurate verification methods or adequate laboratory tests leave this parameter to be controversially discussed. In this work meteor/fireball data obtained by the Fireball Recovery and InterPlanetary Observation Network (FRIPON) was used to calculate the masses of the pre-atmospheric meteoroids which could in turn be compared to the meteor brightnesses to assess their luminous efficiencies. For that, deceleration-based formulas for the mass computation were used. We have found $τ$-values, as well as the shape change coefficients, of 294 fireballs with determined masses in the range of $10^{-6}$ kg - $100$ kg. The derived $τ$-values have a median of $τ_{median}$ = 2.17 %. Most of them are on the order of 0.1 % - 10 %. We present how our values were obtained, compare them with data reported in the literature, and discuss several methods. A dependence of $τ$ on the pre-atmospheric velocity of the meteor, $v_e$, is noticeable with a relation of $τ=0.0023 \cdot v_e^{2.3}$. The higher luminous efficiency of fast meteors could be explained by the higher energy released. Fast meteoroids produce additional emission lines that radiate more efficiently in specific wavelengths due to the appearance of the so-called second component of higher temperature. Furthermore, a dependence of $τ$ on the initial meteoroid mass, $M_e$, was found, with negative linear behaviour in log-log space: $τ=0.48 \cdot M_e^{-0.47}$. This implies that the radiation of smaller meteoroids is more efficient.

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arXiv2019

NELIOTA: Methods, statistics and results for meteoroids impacting the Moon

This paper contains the results from the first 30 months of the NELIOTA project for impacts of NEOs/meteoroids on the lunar surface. Our analysis on the statistics concerning the efficiency of the campaign and the parameters of the projectiles and the impacts is presented. The parameters of the lunar impact flashes based on simultaneous observations in two wavelength bands are used to estimate the distributions of the masses, sizes and frequency of the impactors. These statistics can be used both in space engineering and science. The photometric fluxes of the flashes are measured using aperture photometry and their apparent magnitudes are calculated using standard stars. Assuming that the flashes follow a black body law of irradiation, the temperatures can be derived analytically, while the parameters of the projectiles are estimated using fair assumptions on their velocity and luminous efficiency of the impacts. 79 lunar impact flashes have been observed with the 1.2 m Kryoneri telescope in Greece. The masses of the meteoroids range between 0.7 g and 8 kg and their respective sizes between 1-20 cm depending on their assumed density, impact velocity, and luminous efficiency. We find a strong correlation between the observed magnitudes of the flashes and the masses of the meteoroids. Moreover, an empirical relation between the emitted energies of each band has been derived allowing the estimation of the physical parameters of the meteoroids that produce low energy impact flashes. The NELIOTA project has so far the highest detection rate and the faintest limiting magnitude for lunar impacts compared to other ongoing programs. Based on the impact frequency distribution on Moon, we estimate that sporadic meteoroids with typical masses less than 100 g and sizes less than 5 cm enter the mesosphere of the Earth with a rate ~108 meteoroids/hr and also impact Moon with a rate of ~8 meteoroids/hr.

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arXiv2019

The Sporadic Activity of (6478) Gault: A YORP-driven event?

On 2019 January 5 a streamer associated with the 4--10 km main-belt asteroid (6478)~Gault was detected by the ATLAS sky survey, a rare discovery of activity around a main-belt asteroid. Archival data from ATLAS and Pan-STARRS1 show the trail in early December 2018, but not between 2010 and January 2018. The feature has significantly changed over one month, perfectly matching predictions of pure dust dynamical evolution and changes in observing geometry for a short release of dust around 2018 October 28. Follow-up observations with HST show a second narrow trail corresponding to a brief release of dust on 2018 December 30. Both releases occurred with negligible velocity. We find the dust grains to be fairly large, with power-law size distributions in the $10^{-5} - 10^{-3}$~m range and power-law indices of $\sim -1.5$. Three runs of ground-based data find a signature of $\sim 2\,\rm h$ rotation, close to the rotational limit, suggesting that the activity is the result of landslides or reconfigurations after YORP spin-up.

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arXiv2019

Simulation of Sky Surveys with the Flyeye Telescope

ESA's Flyeye telescope is designed with a very large field of view (FoV) in order to scan the sky for unknown near-Earth Objects (NEOs). For typical exposure times of 40 s, the telescope is able to detect objects with a limiting magnitude up to 21.5. The aim is to observe those NEOs that are going to hit the Earth within a few weeks or days, in advance of impact. In order to estimate the detection rate of NEOs with the Flyeye telescope, a synthetic population of Earth threatening asteroids is created by means of the software NEOPOP. Then, the true anomalies and longitudes of the ascending node of these objects are modified in order to generate about 2500 impactors. In the simulations almost three impacts can be detected per year from NEOs down to 1 m using only one Flyeye telescope. When operating two telescopes simultaneously, one at Monte Mufara and one at La Silla, four detected impacts per year are expected. Nonetheless, it is estimated that about 15.6% of the Earth impactors will be very difficult to be detected using ground-based telescopes due to the fact that they are approaching us from the Sun.

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arXiv2019

A systematic ranging technique for follow-ups of NEOs detected with the Flyeye telescope

When new objects are detected in the sky, an orbit determination needs to be performed immediately to find out their origin, to determine the probability of an Earth impact and possibly also to estimate the impact region on Earth. ESA's Flyeye telescope is expected to revolutionize the effort of predicting potential asteroid or deep space debris impact hazards due to the expected increase of near-Earth object discoveries. As the observed orbit arc for such an object is very short, classical Gaussian orbit determination cannot be used. We adopt the systematic ranging technique to overcome the lack of information and predict a region of the sky where the body can most likely be found. We also provide a detection probability for follow-up observations and investigate potential follow-up telescopes for the Flyeye telescope.

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arXiv2019

NELIOTA Lunar Impact Flash Detection and Event Validation

NELIOTA (NEO Lunar Impacts and Optical TrAnsients) is an ESA-funded lunar monitoring project, which aims to determine the size-frequency distribution of small Near-Earth Objects (NEOs) via detection of impact flashes on the surface of the Moon. A prime focus, high-speed, twin-camera system providing simultaneous observations in two photometric bands at a rate of 30 frames-per-second on the 1.2 m Kryoneri telescope of the National Observatory of Athens was commissioned for this purpose. A dedicated software processes the images and automatically detects candidate lunar impact flashes, which are then validated by an expert user. The four year observing campaign began in February 2017 and has so far detected more than 40 lunar impact events. The software routinely detects satellites, which typically appear as streaks or dots crossing the lunar disk. To avoid confusing these events with real flashes, we check different available catalogs with spacecraft orbital information and exclude spacecraft identifications.

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arXiv2018

Models of Rosetta/OSIRIS 67P dust coma phase function

The phase function of the dust coma of comet 67P has been determined from Rosetta/OSIRIS images \citep{Bertini17}. This function show a deep minimum at phase angles near 100$^\circ$, and a strong backscattering enhancement. These two properties cannot be reproduced by regular models of cometary dust, most of them based on wavelength-sized and randomly-oriented aggregate particles. We show, however, that an ensamble of oriented elongated particles of a wide variety of aspect ratios, with radii $r \gtrsim$10 $μ$m, and whose long axes are perpendicular to the direction of the solar radiation, are capable of reproducing the observed phase function. These particles must be absorbing, with an imaginary part of the refractive index of about 0.1 to match the expected geometric albedo, and with porosity in the 60-70\% range.

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