MITM8

(385186) 1994 AW1 was the first known asteroid with a satellite, discovered in 1994 using photometric lightcurve [1], the most successful technique used for this purpose. After that, more than 450 asteroids with satellites were discovered in the Solar System [2], almost 80% of them with orbits up to Jupiter, using many other observation techniques such as radar, and direct imaging from the ground and space. Recently in 2021, it was the first time that a stellar occultation provided the discovery of a companion asteroid by two independent events [3]. But still, a whole range of separation and size ratios is out of reach, where asteroids are too faint for high-resolution imaging, too far for radar, or do not provide a good signature in photometry. In that range, the use of highly accurate astrometry could be promising. In binary star research, companions are revealed by astrometry when the motion of a star around the common barycentre is measured (wobbling). The same approach becomes possible for asteroids, for the first time thanks to Gaia astrometry. As predicted way before the launch of the Gaia satellite[4], the high accuracy astrometric data could be used to find binary asteroids currently out of reach of detection. The Gaia mission provided to the scientific community astrometric solutions at an unprecedented precision [5]. Data Release 3 (DR3) provides new data for more than 150.000 asteroids, 10 times more than in Gaia DR2. Hence, using a large number of bodies in DR3 data with even better precision than in previous releases, we aim to search for astrometric asteroid binaries. Our approach starts by averaging the residuals to orbital fits over each transit in the focal plane. We select the asteroids with at least 10 values of residuals that are consecutive in time or anyway spanning a limited time range. This selection results in a sample of a bit more than 30000 objects. Then, using a Generalized Lomb-Scargle periodogram (see [6] and references therein), we run a period search on every sequence in order to find a signal that would represent the period and amplitude of the system's wobbling. The result is a map of the frequency power that indicates the goodness of data fitting. Since this technique always finds periodic fluctuations that could be spurious because of residual noise, we perform some statistical tests to determine the probability of fake detection and the relevance of the signal found. The first procedure is to run 10000 Monte Carlo simulations on white noise using the same time-sampling as the real data. The resulting p-value shows us how likely it is to obtain a peak as large as the largest peak found in the data if there was only noise in the data. The bodies that have a p-value smaller than 5% pass through the second calibration test. Again we perform 2000 MC simulations while adding white noise to the real data and checking how it affects the distribution of frequencies obtained from the GLS periodogram. If at least 10% of the distribution lies around the best frequency found for the real data, then we select this body. This procedure tells us the quality and confidence of the signal found, i.e., how easy it is to detect and how much we can trust that there is a signal in the data.  After the period search and statistical relevance tests, we obtain over 3300 candidates as possible binary asteroids. The last step is to check if the wobbling found is physically consistent. Hence we calculate the estimated range of density, separation and mass ratio for the binary candidates. We consider 7 g/cm³ as a maximum threshold for an acceptable maximum density.  In the end, we obtained almost 250 asteroid binary candidates that survived the 3-stage selection. We still can't guarantee that the periods found with such favourable conditions are caused by a companion satellite, but we show that there are some interesting pieces of evidence to support such a hypothesis. Further verification is required, both by statistical methods and observations, to validate our findings.

References

[1] Pravec, P. & Hahn, G. 1997, Icarus, 127, 431

[2] Johnston, Wm. Robert. "Asteroids with Satellites Database" May 16, 2022. Johnston's Archive

[3] Gault D., Nosworthy P., Nolthenius R., Bender K., Herald D., 2022, MPBu, 49, 3

[4] Tanga, P., Hestroffer, D., Delbò, M., et al. 2008, Planetary and Space Science, 56, 1812

[5] Gaia Collaboration, Spoto, F., Tanga, P., et al. 2018b, Astronomy and Astrophysics, 616, A13

[6] VanderPlas, J. 2018, ApJS, 236, 16

[7] Hestroffer, D., Dell’Oro, A., Cellino, A., & Tanga, P. 2010, in Lecture Notes in Physics, Berlin Springer Verlag, Vol. 790, 251–340

Acknowledgements

This work presents results from the European Space Agency (ESA) space mission Gaia. Gaia data are being processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC is provided by national institutions, in particular the institutions participating in the Gaia MultiLateral Agreement (MLA). The Gaia mission website is https://www.cosmos.esa.int/gaia. The Gaia archive website is https://archives.esac.esa.int/gaia.

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001, also by CAPES-PRINT Process 88887.570251/2020-00, by the French Programme National de Planetologie, and by the BQR program of Observatoire de la Côte d'Azur. 

How to cite: Liberato, L., Tanga, P., Mary, D., and Spoto, F.: Satellite Search in Gaia DR3 astrometry, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-630, https://doi.org/10.5194/epsc2022-630, 2022.

In 2019, Comet Interceptor was selected by the European Space Agency, ESA, as the first in its new class of F missions. At the time of this writing, formal adoption of the mission is anticipated for early June 2022. The Japanese space agency, JAXA, is making a major contribution to the project. Comet Interceptor's primary science goal is to characterise for the first time, a yet-to-be-discovered long-period comet, preferably dynamically new, or an interstellar object. An encounter with a comet approaching the Sun for the first time will provide valuable data to complement information gathered by all previous comet missions, which through necessity all visited more evolved short period comets. The spacecraft will be launched in 2029 with the Ariel mission to the Sun-Earth Lagrange Point, L2. This relatively stable location allows a rapid response to the appearance of a suitable target comet, which will need to cross the ecliptic plane through an annulus centered on the Sun that contains Earth’s orbit. A suitable new comet would be searched for from Earth, with short period comets acting as mission backup targets. Powerful facilities such as the Vera Rubin Observatory make finding a suitable comet nearing the Sun very promising, and the spacecraft could encounter an interstellar object if one is found on a suitable trajectory. The spacecraft must cope with a wide range of target activity levels, flyby speeds, and encounter geometries. This flexibility has significant impacts on the spacecraft solar power input, thermal design, and shielding that can cope with dust impacts. Comet Interceptor comprises a main spacecraft and two probes, one provided by ESA, the other by JAXA, which will be released by the main spacecraft on approach to the target. The main spacecraft, which would act as the primary communication point for the whole constellation, would be targeted to pass outside the hazardous inner coma, making remote and in situ observations on the comet’s sunward side. Planned measurements of the target include its surface composition, shape, and structure, its dust environment, and the gas coma’s composition. A unique, multi-point ‘snapshot’ of the comet- solar wind interaction region will be obtained, complementing single spacecraft observations at other comets. We shall describe the science drivers, planned observations, and the mission’s instrument complement, to be provided by consortia of institutions in Europe and Japan.

How to cite: Jones, G., Snodgrass, C., and Tubiana, C. and the The Comet Interceptor Consortium: The Comet Interceptor Mission, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1085, https://doi.org/10.5194/epsc2022-1085, 2022.

Space Surveillance and Tracking (SST) requires the development of observational campaigns to early identify Earth orbiting objects, estimate their orbital elements and monitor the evolution of their trajectories.

With a growing number of satellites being launched every year, there is an increasing interest in SST at worldwide level and especially across the EU. In this context, Romania is one of the few EU member states involved in such activities.

SST systems must implement an Image Data Reduction Subsystem, able to timely process the continuous exposures taken in an automatic and continuous way by optical telescopes, analyse these data sets to identify objects of interest (target objects) and retrieve accurate measurements of the apparent position and brightness of the detected objects. In the last step, the tool generates tracklet information for the identified target objects.

In this context, The Generic Data Reduction Framework for Space Surveillance -  gendared, prototyped initially by GMV in the frame of an ESA Romanian Industry Incentive Scheme project, is intended to be used in order to support the operational reduction of the image data acquired by optical telescopes. gendared receives as input the raw images taken by the telescope, and generates as output astrometric and photometric data for the target objects detected in the observation images.

The key aspects that drove the development of gendared and its advantages include the fact that the software is autonomous and unassisted, can process images in near real-time, can cope with different image acquisition schemas, and is configurable and modular.

As of the end of the prototyping phase and the acceptance of the software by ESA, gendared has been successfully tested and validated on Romanian telescopes and developed further for various operational use cases of different telescopes, such as the German Aerospace Centre (DLR) telescopes.

Furthermore, since mid-2020, gendared is part of a larger architecture of GMV products supporting the operational data processing activities in Romanian Space Agency’s SST Operational Centre (COSST), which ensures the Romanian contribution to the EUSST Consortium. In this case gendared is covering, in a centralized architecture, the processing of the data coming from the Romanian optical telescopes involved in EUSST. The software was further upgraded for this purpose, with new algorithms and processing pipelines included.

Most recently GMV has also won a Romanian Research & Development grant to upgrade gendared with artificial intelligence algorithms. This project involves a consortium led by GMV, with the Faculty of Automatic Control and Computer Science and the Astronomical Institute of the Romanian Academy as partners. By integrating artificial intelligence techniques into the current gendared framework, we aim to improve its performance, reduce user involvement and computational costs, as well as increase pipeline autonomy. The upgraded solution will be tested and validated in representative scenarios based on real telescope data, with the ultimate goal of converting the prototype into a product that will be validated in an SST operational environment on a wide range of telescopes.

How to cite: Piso-Grigore, A.-M., Voicu, A., Sprimont, P., Bija, B., Alonso-Lasheras, O., and Olteanu, V.: gendared: the Generic Data Reduction Framework for Space Surveillance, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-35, https://doi.org/10.5194/epsc2022-35, 2022.