EU-ESA Workshop on Astrometric and Radar Observations of NEOs

6 Oct 2025, 14:00 → 8 Oct 2025, 18:00 Europe/Rome

ESRIN-01121-Magellan (ESRIN)

Juan L. Cano (ESA), Richard Moissl (ESA), Thea Dethlefsen (EC), Maxime Devogele (ESA NEOCC)

The European Commission and ESA’s Planetary Defence Office together are organising the “EU-ESA Workshop on Astrometric and Radar Observations of NEOs” which will take place on 6–8 October 2025 at the European Space Research Institute (ESRIN) in Frascati, Italy.

The aim of this workshop is to bring together the international asteroid and planetary defence communities to critically assess and improve current practices in astrometric and radar measurements as well as orbit determination of NEOs. With the growing importance of precise tracking and prediction of asteroid trajectories, the workshop will focus on the sources of uncertainty in both optical and radar data, methods for properly estimating and reporting them, and the incorporation of new technologies and techniques to enhance the reliability of orbital predictions.

Key Objectives of the Workshop:

• Assess current methodologies used to estimate and propagate astrometric and timing uncertainties, including mathematical frameworks, calibration strategies, and effects in orbital determination.
• Promote the development of community guidelines on how to report and quantify uncertainties in astrometry and timing.
• Investigate new observational techniques and technologies (e.g., synthetic tracking, CMOS sensors, AI-assisted processing) and assess their impact on astrometric accuracy.
• Discuss other sources of astrometry/asteroid position measurement such as radar, stellar occultations, and negative or precovery observations.
• Identify facilities and instruments that could contribute to precise astrometry in the near future.

Tentative Sessions:

1.  Astrometric Observations of NEOs
   
   This session will serve as an introduction to astrometric observations and to provide an overview of the current capabilities and limitations of facilities involved in the astrometric observation of NEOs. Topics will include observational strategies, instrumentation, and data acquisition methods. The session will also highlight recent progress in synthetic tracking, including non-linear approaches, as innovative techniques for improving the detection and tracking of faint and fast-moving NEOs.
   
   
2. On the Uncertainties of Astrometric Observations and effects on orbit determination
   
   This session will delve into the quantitative analysis and interpretation of uncertainties associated with astrometric measurements. It will focus on how these uncertainties are estimated, modeled, and reported—differentiating between random (statistical) and systematic sources of error. The session will also assess the implications of poorly characterized uncertainties for orbit determination and risk assessment. Drawing on case studies, including recent IAWN campaigns, the session will showcase lessons learned and best practices, with particular attention to methodologies for evaluating and communicating timing and positional accuracy in astrometric data.
   
   
3. Non-Standard Astrometric Records
   
   This session will explore unconventional yet valuable sources of astrometric information. Stellar occultations offer opportunities for high-precision position measurements, while archival data, including precoveries and negative observations, can provide critical constraints for orbit determination and long-arc fitting of NEO trajectories.
   
   
4. Radar Observations and the Perspective for a European Radar Facility
   
   Radar plays a pivotal role in refining NEO orbits and improving impact predictions. This session will cover how radar measurements are acquired, calibrated, and interpreted, and discuss how these data are incorporated into orbit determination. A key focus will be the current status and future prospects for establishing dedicated radar capabilities in Europe to support planetary defence efforts.
   
   
5. Emerging Technologies and Techniques
   
   Looking to the future, this session will cover the adoption of CMOS sensors and their astrometric performance, as well as the integration of artificial intelligence and machine learning into astrometric data reduction pipelines. Presentations will also introduce upcoming facilities and instruments expected to significantly enhance the astrometric tracking of NEOs in the coming years.

A dedicated session will aim to consolidate input from all participants into a community white paper or technical document outlining best practices for uncertainty estimation and reporting.

Privacy Notice for EU-ESA workshops

Monday 6 October

Welcome

Welcome to the EU-ESA Workshop on size determination of potentially hazardous near-Earth objects

1 Welcome

Welcome and introduction to the workshop

Orbit determination and impact monitoring

2 Asteroid orbit determination and impact monitoring at ESA: the Aegis software

The Near-Earth Object Coordination Centre (NEOCC) of the European Space Agency is an operational hub that, among other tasks, determines the orbits of near-Earth objects (NEOs) and assesses their probabilities of impacting Earth. Since 2012, the NEOCC has shared NEO-related data via its dedicated web portal (https://neo.ssa.esa.int/). Over the course of its operational phase, significant enhancements have been introduced to the portal, the underlying software, and the data services provided.

A major milestone has been the independent deployment of a new Orbit Determination and Impact Monitoring system, called Aegis. All computations performed by Aegis are publicly accessible through the NEOCC portal, and the system now underpins all primary services. These include an orbital catalogue of all known asteroids, a Risk List of potential future Earth impacts, a close-approach forecast, interactive graphical tools, and an on-demand ephemeris service. Many of these services are also accessible via dedicated APIs, enabling automated data retrieval. This talk presents an overview of the algorithms implemented in Aegis, illustrates its application to planetary defence through practical examples, and summarises the NEOCC services supported by the system.

Speakers: Francesco Gioanotto (ESA NEOCC), Laura Faggioli (ESA NEOCC), Marco Fenucci (ESA NEOCC)

3 Advancing orbit determination and impact monitoring with ADES and high-precision astrometry: an example on 2024 YR4

The Astrometry Data Exchange Standard (ADES) is a new data format for asteroid astrometry, providing many other feature than the previous 80-column format which was adopted by the Minor Planet Center (MPC). Among other information, observers are allowed to report the measured astrometric uncertainties and time uncertainties.

Reporting astrometry in ADES has many advantages, and the astronomical community is on the way to fully transitioning to this new standard, especially the large surveys. On the other hand, orbit computation centers do not use yet the information contained in ADES to its full potential, often still relying on statistical models for uncertainties or manual direct intervention.

In this presentation we present some preliminary results on the orbit determination and impact monitoring with the usage of ADES data. We take into account the case of 2024 YR4, and perform orbit determination with different assumptions on the astrometric uncertainties: 1) fully statistical model; 2) ADES uncertainties and stricter rejection threshold; 3) ADES uncertainties with floor. For these different cases, we simulated the evolution of the impact probability as new observations were announced, comparing with the real scenario.

Still using the same example of 2024 YR4, we show how the orbit determination and impact monitoring would have changed if some radar observations were available in early January. This highlights, in general, how orbital uncertainties vary depending on whether radar measurements are included or not.

With these preliminary results we emphasise the need for the development of new astrometric error models which make use of astrometric uncertainties reported directly in ADES by the observers, underlying the benefits, challenges, and potential issues in moving towards such approach. We also emphasise the need for high-precision astrometry in improving orbit determination.

Speakers: Francesco Gianotto (ESA NEOCC), Laura Faggioli (ESA NEOCC), Marco Fenucci (ESA NEOCC)

4 Identifying and Understanding Bad Tracklets: Inaccurate and Mis-Attributed Astrometry

The Minor Planet Center (MPC) is the world's only center for collecting and disseminating observations of minor planets, comets, and natural satellites. The MPC receives between 3 and 4 million observations per month, for a total of more than 30 million observations per year (before Rubin). Historically, the MPC applied an arbitrary limit of 2 arcseconds when accepting astrometry of attributed objects. However, this threshold did not account for factors such as the pixel size of the telescope, seeing conditions, or the submitter's data processing pipeline.
At the end of 2021 MPC has transitioned from this hard 2-arcsecond limit to a weighting system based on a submission's observatory code and magnitude, allowing for more precise and often smaller limits. Nevertheless, cases still arise where processing pipelines accept astrometry that is later found to be inaccurate or misattributed.
This issue is particularly harmful for the NEO Confirmation Page (NEOCP), where early tracklets often cover only a short arc. A single 'bad' tracklet at this stage can produce an incorrect orbit, misleading follow-up observers, and causing wasted observing time on regions of the sky where the object is not actually located.
Our analysis shows that most bad tracklets on the NEOCP are reported by amateur observers using stacked (Tycho-tracker) astrometry.
We will discuss the frequency of bad tracklets for both NEOCP and non-NEOCP objects (as classified by both astrometric and photometric residuals), and describe the differences between bad measurements and mis-attributions.

Speakers: Federica Spoto (Harvard–Smithsonian Center for Astrophysics, Minor Planet Center, 60 Garden Street, Cambridge, MA, USA), Jorge A. Perez-Hernandez (Harvard–Smithsonian Center for Astrophysics, Minor Planet Center, 60 Garden Street, Cambridge, MA, USA), Matthew Payne (Harvard–Smithsonian Center for Astrophysics, Minor Planet Center, 60 Garden Street, Cambridge, MA, USA), Peter Veres (Harvard–Smithsonian Center for Astrophysics, Minor Planet Center, 60 Garden Street, Cambridge, MA, USA)

Open discussion

15:50 Coffee break

Astrometric Observation Uncertainties

5 Computing Astrometric Uncertainties

There are multiple components to the uncertainty of an astrometric observation.The astrometric solution, based on the pixel coordinates of catalog reference stars, involve coefficients whose uncertainties can be computed using standard linear algebra techniques. Independent of that is the centroid of the target object, which depends primarily on the image width and signal-to-noise ratio, though the accuracy of the flat fielding process can contribute secondarily.
More difficult to quantify are offsets between spatial and temporal centroids caused by variations in seeing, atmospheric transparency, and telescope tracking, and I would be interested in proposals for how one might attempt to quantify these effects. Chromatic effects can also be important for observations at large zenith distances, through wide filters (or no filter at all), and lower elevations where the atmosphere is thicker and refraction larger. The size of the effect has been estimated for one particular case, and implementation of a color term in the astrometric solution is a work in progress, but the lack of color information for a newly-discovered near-Earth asteroid represents an obvious limitation, though one can, to first order, assume the asteroid has the color of the Sun or slightly redder than that. More recently recognized is the effect of anomalous refraction, which can be significant for very short exposures, in which the positions of reference sources can be "frozen" at some distance from their nominal positions. Longer exposures ought to reduce the effect, as the average position ought to be closer to the actual position, but then the harder to quantify spatial-temporal offsets start to dominate. A proposal for a term to quantify anomalous refraction will be presented for discussion. Not to be ignored is the uncertainty in the timestamp associated with an observation.
Multiple observations of GPS satellites during evening and morning twilight have been successfully used to quantify the accuracy of the timestamp, but without knowing the source(s) of the noise, it is difficult to know whether the value to report should be the standard deviation or the standard deviation of the mean (or somewhere between these limits), and some discussion of this issue would be welcomed.

Speaker: Dave J. Tholen (University of Hawaii)

6 On the uncertainties of astrometric observations

Astrometric uncertainties are central to any orbit‑fitting procedure. The result of a fit is a nominal solution, which represents the single orbit that best matches the observations, and a confidence region describing the orbital uncertainty, which includes the set of orbital elements statistically compatible with the data and the error model. For well‑observed asteroids, the region is well approximated by a multidimensional ellipsoid. In contrast, for short-arc objects (e.g. objects on the Minor Planet Center's NEO Confirmation Page), the confidence region appears as a cloud of admissible orbits, whose distribution is frequently asymmetrical in shape, i.e. nonelliptical.

The confidence region depends on a realistic statistical model of observation errors: accurate error statistics determine both the shape of the region’s boundary and the probability distribution of orbits within it.

Astrometric errors are the result of several instrumental and observational factors, including but not limited to the pixel scale and aperture of the telescope, the astrometric catalog used for reducing the observations, the brightness of the observed objects, the observation technique and the observer. This yields a heterogeneous error distribution across the astrometric data set. A preliminary analysis of postfit residuals for observations of numbered objects indicates that the values are usually in the [–1, +1] arcseconds interval. These inhomogeneous uncertainties pose a significant challenge in the determination of precise orbital solutions.

To address this, we present a review of the statistical performances of all of the more than 300 million observations available for numbered objects in the Minor Planet Center database.

Speaker: Federica Spoto (Harvard–Smithsonian Center for Astrophysics, Minor Planet Center, 60 Garden Street, Cambridge, MA, USA)

7 Predicted astrometric uncertainty for NEO Surveyor tracklets

NEO Surveyor will produce observations of hundreds of thousands of near-Earth objects during its 5-year primary mission. Being taken at mid-infrared wavelengths, the astrometric uncertainties will be generally larger than those from ground-based telescopes, while the planned survey cadence means that each tracklet will cover a longer timespan. The access to low elongations enabled by observing from a space-based platform will also change the segments of the orbits that are covered by the observations. We discuss the predicted astrometric performance of NEO Surveyor observations of NEOs, as well as initial metrics for the tracklets that expected to be reported.

Speaker: Joseph Masiero (Caltech/IPAC)

Open discussion

Tuesday 7 October

Welcome

Welcome to the EU-ESA Workshop on size determination of potentially hazardous near-Earth objects

Astrometric Observation Uncertainties

8 NEOCC side-activities enabling precision astrometry

One of our main goals is to provide precision astrometry for high-profile objects, which require having a network of telescopes properly characterised and suite of sensors fully understood. We routinely participate in IAWN campaigns for timing, rapid response, but also do training with close-approachers or artificial objects in high orbits or reentering.

Timing of the observations is essential; therefore, we measure the bias in our measurements and their intrinsic uncertainty, and/or stability. Moreover, we improve this estimation with spatial mapping for cameras with several chips, long-travel shutters, or line-by-line read-out. We include this information in our reports in ADES format.

It is also important to know the topocentric location of the telescope. Apart from the use of GNSS receivers on-site, we have successfully used the observation of GNSS satellites to determine the topocentric coordinates. We have performed this task for all our owned/funded telescopes, and corrected from the geoid altitude in some cases.

As part of the practicing, we perform observations in challenging conditions, like close to the full moon or at low elevations. This sort of observations are often required to provide key astrometry for relevant NEOs . Some of our facilities allow us to observe at low elongation, not only for arc extension in the discovery opposition, but also early recoveries that enable characterisation of close approachers coming from the sun glare (e.g., 2023 KU).

We also provide some support for different projects in the agency, producing some non-asteroidal astrometry. We are supporting the Space Debris Office in the pre-reentry follow-up of the Cluster II spacecraft, providing for astrometry for orbit determination leading to an impact corridor. Moreover, we are also following spacecraft and rocket bodies launched in heliocentric orbits that may return in a near future and may use some our community resources if not properly identified.

Speaker: Francisco Ocaña (ESA NEOCC)

9 High-precision astrometry at ESA NEOCC

For more than a decade, here at ESA's NEO Coordination Centre we have been focusing on obtaining high-precision astrometry of priority targets. Over this time, we have developed resources and capabilities that allow for a quick and accurate response to Planetary Defence observational needs.

This talk will begin with an overview of our capabilities, emphasising the value of fast response and global coverage in astrometric work on targets relevant to planetary defence.

Will then turn our attention to the role of image quality, field of view and sampling in following up faint sources and extracting accurate astrometry. We will also briefly discuss on the specific difficulties posed by trailing, galactic confusion, extended objects or observations at low solar elongation, together with the techniques we use to address them.

Finally, we will outline our strategies for dealing with common challenges in astrometric follow-up, such as large ephemeris uncertainties (also in velocity space) and the faintness of a target when observed with moderate-size facilities. Such issues will become even more important, for both amateur and professional observers, once the increased flow of new discoveries from large surveys like Rubin begins.

Speaker: Marco Micheli

10 Influence of the dynamic classification of asteroids on observation astrometric errors

Astrometric observations weights, usually computed after a station-specific statistical analysis on the observation residuals, quantify the expected accuracy of data.
The influence on observations weights of external factors such as epoch of observation, magnitude, and employed catalogue has already been proven in the literature.
This work analyses observation residuals of the major surveys accounting for the dynamical classification of asteroids, to understand whether the observation quality may have a dependence on the different type of observed object to develop a more accurate weighting system. The work identifies four stations with different qualities depending on whether they are observing near-Earth asteroids or main-belt asteroids. Moreover, the cross-correlation between the dynamic classification and epoch, magnitude, and catalogue is investigated, as well as the influence of these factors on observations’ quality.

Speaker: Nicolo Stronati

11 Impact of Observation Time Uncertainty on Orbit Determination: An experiment with real data

Accurate orbit determination of near-Earth objects (NEOs) relies critically on the precision of astrometric
observations, including the timing of each measurement. In this work, we investigate the effect of
observation time uncertainty on orbit determination by analyzing observational data with explicit timing
uncertainty information. We performed Orbit Determination task using astrometric data in ADES format
retrieved from the Minor Planet Center (MPC), focusing on entries that include uncTime and/or rmsTime
fields. These two fields represent the systematic and random components of the timing uncertainty,
respectively, as declared in [1].
Initial orbital elements were sourced from the NEO Coordination Centre (NEOCC) database. In particular,
the overall dataset is composed by 1660 asteroids selected at July 17th: 1468 are NEOs (74 of them are in
ESA risk list), 111 are numbered or multi-opposition, the remaining 81 are single opposition. The latter have
been discarded since Aegis does not carry out orbit determination task on them.
We compare two sets of solutions of differential corrections: one determined without considering timing
uncertainties, as is currently done in daily operations at NEOCC, and one that incorporates this information
into the orbit determination process. Aegis projects timing uncertainties to the astrometric weights in Least
Squares Fit through the angular speed of the asteroid predicted at each available observation time,
augmenting the uncertainty ellipse of the optical observation in the Sky Plane. This is the same approach
adopted by JPL in [2].
The analysis focuses on quantifying the resulting differences, particularly in terms of the (square root of)
eigenvalues of covariance matrix and the displacement between the new and initial solutions. The square
root of eigenvalues of covariance matrix represent the length of the axes of the ellipsoid, so they could give
a better idea about shrinking or stretching of the (linear) confidence region.
Bibliography:
[1] A Concise Description of the Astrometry Data Exchange Standard, 2024-05-02
[2] Farnocchia et al. (2022). International Asteroid Warning Network Timing Campaign: 2019 XS. The
Planetary Science Journal. 3. 156. 10.3847/PSJ/ac7224.

Speaker: Davide Bracali Cioci (SpaceDyS)

Open discussion

11:00 Coffee break

Software and new technologies

12 NEODetect: An AI-based real-time system for faint NEO trail detection - latest enhancements for improved accuracy and usability

Machine Intelligence Zrt is advancing Europe’s efforts in Near-Earth Object (NEO) detection through the development of NEODetect, a cutting-edge AI-driven system designed for real-time analysis of astronomical images while Konkoly Observatory is currently leading Europe’s Near-Earth Object (NEO) survey effort, with more than 250 discoveries in the past four years, including three imminent impactors found between 2022 and 2024.
Supported by the European Space Agency, we recently introduced a novel search technique that leverages machine learning algorithms to accelerate real-time image analysis - specifically targeting faint, trailed images of the smallest and closest NEOs. A custom deep-learning model, trained on both real and extensive synthetic astronomical datasets, now enables robust detection of NEOs and space debris, a key advantage over traditional methods.
However, feedback from our users highlighted a limitation: the initial model did not deliver precise positional estimate for candidates, necessitating additional fitting and validation steps by astronomers. Addressing this, we are now integrating a secondary neural network module that predicts each NEO candidate’s subpixel position, trail length, and direction of motion with high accuracy. This upgrade increases the reliability and precision of individual detections and dramatically simplifies result matching and the analysis of time-series data, especially valuable for large, mosaic-mode telescope systems scanning vast sky areas.
Through extensive testing and benchmarking, NEODetect has proven to be a fast, reliable tool that broadens the capabilities of NEO and space debris discovery efforts. By combining the powerful pattern recognition capabilities of deep learning with our ongoing developments in precise quantitative analysis, Machine Intelligence Zrt aims to elevate both the scientific impact and operational efficiency of modern survey programs, laying a solid foundation for the future of automated planetary defense.

Speaker: Szabolcs István Velkei (Machine Intelligence Zrt)

13 Astrometrica: Basic functions and practical application

Astrometrica is a software tool for astrometric and photometric analysis of digital astronomical images. It has been used successfully by observers around the world for about two decades. In this session, we will describe the basic functions of the software and its practical applications. We will also discuss possible future developments.
Peter and I will share the presentation. Peter will probably add a few more words to the abstract, describing his part, which will focus on the practical use of the software by active observers.

Speaker: Herbert Raab

14 Exploring the Impact of Camera Timing on NEO Astrometry

Accurate astrometry of Near-Earth Objects (NEOs) depends on two key elements: precise timing and precise positional measurement. For most stars and main-belt asteroids, timing errors are negligible compared to position errors. But NEOs, with their rapid apparent motion, are highly sensitive to even small timing biases. An observatory that has not properly calibrated its timing source may find residuals far larger than expected, undermining orbit determination and follow-up efforts. This presentation examines the hardware, software, and calibration factors that influence timing accuracy, and offers practical strategies for evaluating and improving it.

Speaker: Daniel Parrott

15 sCMOS Detectors for NEO Observations: Opportunities and Challenges

Scientific CMOS (sCMOS) detectors are being increasingly introduced into astronomical instrumentation due to their fast readout speeds, low read noise, and growing affordability. These features are especially relevant for observing Near-Earth Objects (NEOs), which are often faint, fast-moving, and require high-cadence observations.

In this talk, I will present our experience using sCMOS sensors, specifically the Sony IMX455 and IMX411, across a group of robotic telescope projects installed at Teide Observatory (Tenerife, Spain), actively contributing to Solar System science: ATLAS-Teide, the Transient Survey Telescope (TST), and the Two-meter Twin Telescope (TTT). I will outline the general properties of sCMOS technology and compare them to traditional CCDs, highlighting their implications for NEO observations, including the role of different noise contributions and the challenges introduced by rolling shutter readout.

Special focus will be given to ATLAS-Teide, the newest node in the global ATLAS (Asteroid Terrestrial-impact Last Alert System) network. Located at the Teide Observatory (Canary Islands), this facility operates 16 telescopes simultaneously in synchronized groups of four, delivering wide-field, high-cadence coverage of the night sky. The adoption of sCMOS technology is significantly boosting the network’s ability to detect potentially hazardous asteroids and contribute to planetary defense.

I will present recent scientific results from ATLAS-Teide, TST and TTT, including NEO discoveries, orbit refinement, and physical characterization, along with preliminary results from an ongoing survey targeting fast-rotating NEOs, some of them with sub-minute periods, where the high frame rate and low readout noise of sCMOS detector offer clear advantages over traditional CCDs. I will discuss how sCMOS-based instrumentation is reshaping the way we observe and monitor small bodies in the Solar System.

Speaker: Miguel R. Alarcon (Instituto de Astrofísica de Canarias (IAC), C/ Vía Láctea, s/n, E-38205, La Laguna, Spain)

Open discussion

13:30 Lunch break

Software and new technologies

16 Commissioning and First Light Results of ESA’s Flyeye-1 Telescope

The Flyeye-1 is the first in a planned network of wide-field survey telescopes designed by the European Space Agency (ESA) to enhance Europe’s capability in detecting and tracking Near-Earth Objects (NEOs). This talk presents results from the commissioning campaign of Flyeye-1, conducted at the test facilities at the Matera Space Centre, operated by the Italian Space Agency (ASI) in southern Italy.
We report the integration of the telescope with its equatorial mount and the progress on the optical alignment of the telescope’s 16 astronomical optical channels and cameras. At the same time, major software components – including the Front-End Control software, the Tasking and Scheduling software, and the Flyeye Data Processing Chain (DPC) – are in the process of being integrated. The expected performance of the DPC was validated using simulated images of artificial NEOs.
First light observations were carried out to verify system interconnectivity and assess key performance metrics including image quality, astrometric and photometric accuracy, and field uniformity. Testing included manual calibrations and manual interactions, single-night operational tests, and safety and maintenance checks. A full demonstration of the system’s end-to-end functionality – covering automated scheduling, image acquisition, object detection and reporting – is planned for two dedicated sessions in Q3 2025, following the completion of the Factory Acceptance Tests (FAT). Early results from the acceptance phase point to Flyeye-1’s strong potential for operational deployment and its expected contribution to ESA’s planetary defense activities.
Finally, we provide an update on the construction of the permanent observatory at Mt. Mufara (Sicily), where the Flyeye-1 is scheduled to be permanently relocated in 2026 and outline the roadmap for future developments and the planned expansion of the network.

Speaker: Dora Fohring (ESA NEOCC)

Astrometry from Space

17 The James Webb Space Telescope as a Planetary Defense Asset

The James Webb Space Telescope (JWST) proved that it is capable of achieving planetary defense objectives via its targeted follow-up observations of the near-Earth asteroid (NEA) 2024 YR4. The Near Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI) were used to study 2024 YR4 and better constrain its (1) orbit, (2) size, and (3) rotation light curve. Each of these objectives required different, non-default data products. For instance, the JWST observations were made while tracking on the NEA, but the default calibration products removed the cores of the stellar PSFs. However, astrometric measurements required intact star streaks, so the JWST pipeline was run locally with the “cosmic ray rejection” step turned off. Additional effort was required to correctly determine the time when the target was observed, due to the non-destructive, up-the-ramp sampling nature of the JWST detectors. Determining the diameter of 2024 YR4 required completely different data products where all dithers were combined, fully eliminating the star streaks and leaving behind only the target. For the rotation light curve studies, individual integrations within a dither, which are combined by default, were broken out and processed separately to increase temporal sampling. The processes for creating all of these different “flavors” of data are now in place and ready to run immediately following future JWST observations of NEAs that pose a threat to Earth. In this talk I will focus on the flexibility of the JWST data to meet all of these needs simultaneously, which arises from the way that the detectors operate. Pitfalls and workarounds will also be discussed, since this flexibility naturally comes hand-in-hand with additional complexity.

Speaker: Bryan Holler

16:15 Coffee break

Astrometry from Space

18 High-precision astrometry of moving targets with HST

Astrometry of moving targets with HST imaging devices presents some interesting challenges to retain the full precision possible. The dominant challenge comes from the differential motion between the object and the background stars. This motion includes the orbital path of HST around the Earth in addition to the usual orbital motions of the Earth and object around the Sun. Just as important as the measurement, I will detail how I measure the typically non-gaussian positional errors of the astrometry. I will review the methods I use for the extraction of astrometric positions and uncertainties using examples from New Horizons and Lucy mission support work as well as Ouamuamua. This discussion will include the approximations required to support an MPC submission.

Speaker: Marc Buie (Southwest Research Institute)

Open discussion

Stellar Occultation

19 Occultation-based astrometry

Occultations of stars by solar system objects provides a very accurate differential position of the object relative to the occulted star. The precision of this measurement can reach micro-arcsecond levels, particularly in the outer solar system. The conversion of such constraints into absolute astrometry requires separate knowledge of the star position. Starting with the release of the Gaia DR2 catalog, the star positions were finally good enough to produce astrometry that is most similar to what is possible with radar ranging. A common approach to this uses the concept of the "fundamental plane". I have developed an alternate methodology that provides equivalent astrometry but is based on a simpler geometric approach. I will describe this process along with some approaches for finding the center of the object and then estimating non-gaussian error envelopes for the astrometry. Also included will be a summary of the precision possible for different types of solar system bodies from NEAs out to TNOS.

Speaker: Marc Buie (Southwest Research Institute)

Wednesday 8 October

Welcome

Welcome to the EU-ESA Workshop on size determination of potentially hazardous near-Earth objects

Astrometry from Space

20 Including Gaia FPR astrometry in the estimation of Main Belt Asteroid Masses

We present the results of our analysis of the Gaia Focused Product Release (FPR) astrometry [1] and the results of the Main Belt Asteroid (MBA) mass estimation exercise using all available astrometry [2]. Gaia FPR includes astrometric observations of more than 156,000 asteroids [3]. The high precision of these astrometric observations requires careful modeling of the dynamics and the observable. We find that the offset of the center-of-light with phase angle is significant in the larger objects. Therefore, we improve the observable model with a center-of-light correction. In addition, we inflate the uncertainty of the measurements to account for the unknown location of the center-of-mass relative to the center-of-light and unmodelled parameters of the center-of-light location. Adding this dataset to all astrometry reported to the Minor Planet Center and radar delay-Doppler, we estimate the masses of Main Belt Asteroids. We demonstrate this approach for the mass estimate of 16 Psyche [4], then generalize the method to estimate the masses of a preliminary list of small-body perturbers. We search for close encounters between all known asteroids and the small-body perturbers; 975,000 asteroids had encounters within their observational arc. Of those, about 86,000 have some signal in their astrometry for one or more asteroid masses. We obtain 77 MBA mass estimates with SNR>10 and 232 estimates with SNR>3. From the derived estimates, we provide updated density estimates and an updated total main belt mass.

This research was supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, administered by Oak Ridge Associated Universities under contract with NASA.
[1] Fuentes-Muñoz et al. (2024), AJ, 167:290
[2] Fuentes-Muñoz et al. (2025), AJ (in review)
[3] Gaia Collaboration et al, (2023) A&A, 680, A37

Speaker: Oscar Fuentes-Muñoz (Jet Propulsion Laboratory, California Institute of Technology)

21 Space-based NEO targets: opportunities and challenges

In the past, observations from space assets successfully showed the potential of discovering and analysing NEOs and other small bodies in the solar system within the scope of its mission (e.g., Gaia, NEOWISE). More and more, we make use of more unconventional observations from spacecrafts that were not fully intended for such operations – 2024 YR4 observations by JWST turned out to be a valuable opportunity in constraining the orbit, now with the planned 3I/ATLAS observations from JUICE and potentially other, we reach a point in time, where observations from space are possibly the best or sometimes the only ones to obtain critical information. With increasingly rapid response times, this raises challenges in operations, but just as important opportunities. We will be able to have a look at recent and upcoming targets, share lessons-learned, and discuss systematic strategies reducing the efforts.

Speaker: Tobias Hoffmann (ESA ESOC)

22 Analysis of NEOMIR’s detection capabilities given an astrometric precision of 0.2”

Searching the sky for potentially hazardous asteroids is typically carried out by dedicated ground-based surveys. These observations face certain limitations, as the telescopes operate in the visible wavelength range and only observe at night. Since optical telescopes detect asteroids via reflected sunlight, objects approaching Earth at very small elongation angles are particularly difficult to spot. With the aim of detecting these objects and provide a sufficient warning time in case of an impacting event, the NEOMIR mission, a telescope placed in the Sun-Earth L1 and observing in the mid infrared, is proposed.

The work focuses on the quality of NEOMIR’s data and the possibility of producing precise orbit predictions out of them, determining the impact time and location of the identified objects. The possibility of following-up the objects from the ground is also explored. In particular the study assesses how the NEOs’ orbits’ uncertainty evolves with time as a function of NEOMIR’s observational arc and astrometric precision, assumed to be of 0.2”. A number of 163 synthetic impactors is analyzed and observations are simulated as taken from ACE, spacecraft in an orbit representative of the NEOMIR’s one. All observations are filtered based on NEOMIR’s detecting capabilities, and processed through the FindOrb software, generating the orbital solution and associated covariance matrix. A Monte Carlo simulation is performed for each object to explore its uncertainty area and assess its impact probability. Based on the produced solutions, ground-based observations are also simulated and included in the study; improvements in the results are analyzed.

We concluded that NEOMIR would allow to distinguish NEOs from innocuous objects and to determine a limited impact corridor, but not the exact impact location. Additional ground-based observations are paramount to ensure determination of the impact point. Based on the current telescopes’ capabilities we obtain that 2/3 of the considered objects can be re-observed from the ground.

Speaker: Margharita Revellino (ESA NEOCC)

Open discussion

10:45 Coffee break

Stellar Occultation

23 The role of stellar occultations in NEO astrometry

Occultations by asteroids are an outstanding technique capable of providing extremely astrometry relative to the occulted star. Currently, occultations (mostly observed with portable equipment) provide several hundred astrometric observations per year, in an increasing trend.
The Gaia mission has contributed to occultation both by reducing the uncertainty on both asteroid orbits and star positions. As a consequence, the prediction of the occultation paths on Earth have dramatically improved, to the point that stellar occultations by Near Earth Asteroids have become possible.
Occultation events by NEA remain, however, a challenge, due to their small size resulting in a very narrow occultation path. Extremely accurate orbits and ephemeris are needed, and the event durations is always short (order of 0.1 to 0.01 s).
In this context, successful occultations typically require: several observers covering the cross section of the occultation path and its uncertainty margins; a fast sampling rate preserving a good signal-to-noise (fast cameras and relatively large telescopes); very accurate absolute time-tagging. At the data reduction stage, effects due to diffraction, noise, and relativistic light propagation must be carefully evaluated and taken into account.
The possible reward is proportional to the difficulty of the challenge. The experience has shown that this technique can equal radar astrometry in terms of astrometric accuracy, considerably improving the dynamical characterization on aspects such as the Yarkovsky accelleration, the possible orbital changes due to surface activity (for instance in the case of Phaethon), the impact risk (Apophis) and the orbital changes due to mitigation measures (DART impact on Didymos).
In addition to the dynamical characterization, physical properties such as shape and size are obtained. The record established by the smallest asteroid having produced an occultation (Dimorphos) will be illustrated as an outstanding example.
The possibility to exploit this technique more systematically is substantially limited by the available resources and the high costs of occultation campaigns (both in terms of logistics and manpower).

Speaker: Paolo Tanga (Université Côte d'Azur, Observatoire Côte d'Azur, Laboratoire Lagrange CNRS/UMR7293, Nice, France)

Radar observations

24 Physical characterisation of near-Earth objects using planetary radar observations

Planetary radar observations provide a powerful tool for post-discovery characterisation of the physical and dynamical properties of asteroids, comets, the Moon, and terrestrial planets. Radar systems can measure the asteroid’s radar cross section and Doppler broadening, which provide information on the asteroid’s size, rotation rate, and the composition. Radar can also be used for range-Doppler imaging by mapping the reflected power as a function of the Doppler frequency and the range (based on the signal’s round-trip time), which allows imaging resolutions finer than 10 meters per pixel at best, and thus direct observations of morphologic features and possible moons. Furthermore, radar is the only ground-based instrument that can directly probe the near-surface internal structure of asteroids.

I will discuss the physical characterisation of near-Earth objects (NEOs) using radar observations as a tool for understanding the diversity of NEOs by means of numerical inversion modelling of radar polarimetry. Traditionally, primarily the circular polarisation ratio has been used as a measure of surface roughness; however, surface roughness is only one factor in the observed radar polarimetry. I demonstrate that both surface and subsurface (volume) scattering has to be considered using realistic rubble morphologies, size distributions, and dielectric properties, and in contrast, whether these properties can be constrained based on radar polarimetric observations when data quality allows.

Speaker: Anne Virkki (Department of Physics, University of Helsinki, Helsinki, Finland / Finnish Geospatial Research Institute, National Land Survey, Espoo, Finland)

25 The Effelsberg 100-m telescope and its potential for NEO observations

Although more than 50 years old, the 100m-telescope at Effelsberg is still one
of the two largest fully steerable radio telescopes in the world. Its frequency
coverage (300 MHz to 90 GHz) and agility, the high sensitivity, and the various
flexible backends make it a unique instrument in Europe.

Consequently, it is heavily involved in various kinds of astronomical research
using the telescope as stand-alone instrument („single-dish“) as well as in several
VLBI networks. Here, we describe the telescope's properties and discuss its
capabilities to perform NEO observations.

Speaker: Alexander Kraus

26 The ESA “NEO Observation Concepts for Radar Systems” Project and Beyond

From‬‭ 2019‬‭ to‬‭ 2022,‬‭ ESA‬‭ funded‬‭ the‬‭ pilot‬‭ project‬‭ “NEO‬‭ Observation‬‭ Concepts‬‭ for‬‭ Radar‬‭ Systems,”‬ aimed‬‭ at‬‭ developing‬‭ a‬‭ European‬‭ radar‬‭ system‬‭ for‬‭ Near-Earth‬‭ Objects‬‭ (NEOs).‬‭ The‬‭ initiative‬ focused‬‭ on‬‭ enhancing‬‭ planetary‬‭ defense,‬‭ mission‬‭ planning,‬‭ and‬‭ scientific‬‭ research.‬‭ Key‬ contributions‬‭ came‬‭ from‬‭ INAF,‬‭ SpaceDyS,‬‭ and‬‭ the‬‭ University‬‭ of‬‭ Helsinki,‬‭ with‬‭ successful‬‭ radar‬ campaigns‬‭ conducted‬‭ in‬‭ collaboration‬‭ with‬‭ JPL/NASA.‬‭ The‬‭ study‬‭ included‬‭ technical‬‭ evaluations‬‭ of‬ the‬‭ European‬‭ assets‬‭ that‬‭ might‬‭ contribute‬‭ to‬‭ a‬‭ future‬‭ planetary‬‭ radar‬‭ network.‬‭ It‬‭ also‬‭ estimated‬‭ the‬ achievable‬‭ performance‬‭ in‬‭ NEO‬‭ observations‬‭ at‬‭ different‬‭ frequencies,‬‭ considering‬‭ weather‬ conditions.‬‭ Test‬‭ experiments‬‭ were‬‭ devoted‬‭ to‬‭ asteroids‬‭ such‬‭ as‬‭ 2021‬‭ AF8‬‭ and‬‭ (4660)‬‭ Nereus‬‭ (see‬ Pupillo et al. 2024).‬

Additional‬‭ campaigns‬‭ were‬‭ carried‬‭ out‬‭ to‬‭ provide‬‭ additional‬‭ demonstrations‬‭ and‬‭ to‬‭ develop‬ specialized‬‭ software‬‭ tools.‬‭ A‬‭ highlight‬‭ was‬‭ the‬‭ observation‬‭ of‬‭ 2005‬‭ LW3‬‭ at‬‭ close‬‭ approach‬‭ (Nov.‬ 23,‬‭ 2022).‬‭ The‬‭ experiment‬‭ used‬‭ a‬‭ multi-static‬‭ radar‬‭ configuration:‬‭ the‬‭ 70-m‬‭ DSS-63‬‭ (Madrid)‬‭ as‬ transmitter,‬‭ and‬‭ the‬‭ 32-m‬‭ Medicina‬‭ and‬‭ 100-m‬‭ Effelsberg‬‭ telescopes‬‭ as‬‭ receivers.‬‭ This‬‭ marked‬‭ one‬‭ of‬‭ the‬‭ first‬‭ NEO‬‭ radar‬‭ observations‬‭ conducted‬‭ solely‬‭ with‬‭ European‬‭ facilities.‬‭ The‬‭ data‬‭ revealed‬‭ the‬‭ asteroid’s‬‭ rotation‬‭ period,‬‭ surface‬‭ roughness,‬‭ and‬‭ confirmed‬‭ the‬‭ presence‬‭ of‬‭ a‬‭ satellite‬‭ (50–100‬‭ m),‬ detected as a distinct spectral spike.‬

Preliminary‬‭ results‬‭ from‬‭ the‬‭ observation‬‭ of‬‭ 2006‬‭ WB‬‭ (Nov.‬‭ 25–26,‬‭ 2024)‬‭ are‬‭ also‬‭ presented.‬‭ The‬ Sardinia‬‭ Radio‬‭ Telescope‬‭ and‬‭ Lovell‬‭ dish‬‭ served‬‭ as‬‭ receivers,‬‭ while‬‭ DSS-14‬‭ (Goldstone)‬‭ and‬ DSS-63 transmitted at 8.6 and 7.2 GHz. The campaign provided valuable physical data.‬

We‬‭ are‬‭ now‬‭ focusing‬‭ on‬‭ an‬‭ innovative‬‭ VLBI‬‭ radar‬‭ observation‬‭ of‬‭ 2025‬‭ FA22,‬‭ to‬‭ be‬‭ proposed‬‭ as‬‭ an‬ EVN‬‭ ToO.‬‭ If‬‭ confirmed,‬‭ it‬‭ will‬‭ involve‬‭ 11‬‭ European‬‭ receiving‬‭ stations,‬‭ relying‬‭ on‬‭ DSS-63‬‭ for‬ transmission.‬
‭

Speaker: Giuseppe Pupillo (INAF-IRA)

27 Towards a European Planetary Radar: Concepts, Architectures, and Trade-offs

Since the collapse of the ARECIBO radio telescope occurred on the 1st of December 2020 we are missing a powerful instrument that has been used for decades for Planetary Radar astronomy. Several institutions in US are trying to identify a viable solution to substitute the ARECIBO telescope. In Europe there are limited resources that could be used to perform this type of experiments. We would like to introduce some idea on how it could be possible to support the design of a European Planetary Radar by trading-off several radar architectures (single dish vs array configuration), different frequencies, different power amplifiers to cope with the Planetary Defence requirements and to take into account preliminary requirements for Cislunar SSA and Planetary Science. To give an example, few studies have demonstrated that, considering both CAPEX & OPEX costs a solution based on an array of smaller antennas will be cheaper than a new architecture based on a monolithic antenna. Graceful degradation will further help in improving the system availability. An array of 18m antennas equipped with 50 kW X-Band SSPA could be designed for such a scope. Nowadays, most observations are based on a network of Telescopes but there is a clear potential to improve these observations with the development of suitable ground-based radar network as well as advanced processing techniques to process data from multiple observations in the optical and RF domain.

Speaker: Marco Alessandrini (ESA)

Open discussion

13:30 Lunch break

Open discussion

16:00 Coffee break

Final discussions, key takeaway, findings