SB9

The NEO Coordination Centre (NEOCC) is one of the key components of ESA’s Planetary Defence activities. Among its goals, it has a mandate to coordinate, collect and analyse telescopic observations of NEOs. To reach this objective, we developed a wide network of observational assets. In this contribution, we discuss some of the latest results obtained thanks to this unique global network.

In the recent years, ESA has strengthened its network of follow-up telescopes. It now has direct access to the Optical Ground Station (Tenerife, Spain) and the Calar Alto Schmidt telescope (fully dedicated to NEOCC activities - Spain). Via dedicated contracts, it also has allocated time in the LCO network, as well as telescopes in Australia (Zadko), Namibia (6ROADS), Reunion and India. Scientific collaboration & agreements granted time with ESO’s VLT and Korean’s BOAO and SOAO facilities.

Regarding future observational means, ESA is currently continuing the construction of the Flyeye telescope. This is a 1-meter class telescope with an ultra-wide field of 7º by 7º that will be installed on top of Monte Mufara (Italy). The Flyeye will be a remote-controlled telescope, while data will be automatically analysed by a dedicated pipeline, with the overall objective of reducing to a minimum the human intervention.

The mentioned observational assets available to our observers are used for a variety of observations. The main goal is of course the acquisition of follow-up observations, both on short notice and at the faint end of an object's observability window. We employ our smaller but geographically-distributed telescopes to quickly react to discoveries of possible new high-priority objects, such as imminent impactors. Larger assets, such as VLT, are instead routinely scheduled to obtain astrometry of risk list objects, down to magnitude ~27. With some specific telescopes we are also focusing on twilight and low-elongation observations, which are essential to track and characterize specific classes of objects, such as Atiras or Earth Trojans.

In addition to these regular observations, we also use some of the telescopes to attempt challenging or innovative observation techniques. For example, we are experimenting with the possibility to use modest sub-meter-size telescopes to obtain detections of important objects down to magnitude ~24, by observing the same target for an entire night and then stacking hundreds of frames on the motion of the object. These capabilities are made possible by recent advancements in GPU processing, which are also opening the way to new image analysis modes, such as synthetic tracking. We are also pioneering the so called "negative recovery" technique, using targeted non-detections of risk list objects to exclude their impact solutions, even without recovering the object itself.

Finally, we are active players in international campaigns dedicated to specific NEOs or observational challenges. This includes both our participation in internationally-led efforts, such as those managed by IAWN, and the organization of our own campaigns, such as a recent one dedicated to the astrometric coverage of the Earth fly-by of BepiColombo as a proxy to test the observational capabilities of our network on very close approachers.

All those observations are supplemented by the operations of our own orbit determination and impact monitoring software system (so-called AstOD) that allows constraining with the best possible accuracy the orbits of the observed objects and the possible impact chances with the Earth in the next 100 years. In what regards the threat monitoring over imminent impactors, we count on the Meerkat tool, which bases its automated operation on the use of systematic ranging and allows detecting and warning our staff of those cases, as recently occurred with 2022 EB5.

How to cite: Cano, J. L., Micheli, M., Conversi, L., Fohring, D., Moissl, R., Koschny, D., Faggioli, L., Gianotto, F., Kresken, R., Ramirez Moreta, P., Oliviero, D., Petrescu, E., Rudawska, R., and Frühauf, M.: Recent observational highlights from ESA’s Planetary Defence Office, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1084, https://doi.org/10.5194/epsc2022-1084, 2022.

 1. Introduction

On 26 September 2022 NASA's Double Asteroid Redirection Test (DART) spacecraft will impact Dimorphos, the satellite of asteroid (65803) Didymos. The impact  will change Dimorphos' orbital period around Didymos. As Didymos is an eclipsing binary, and on a close flyby of Earth on this date, the period change can be detected by Earth-based observers. Before impact, DART will deploy the Light Italian Cubesat for Imaging of Asteroid (LICIACube) that will provide images of the first instants after impact. ESA’s Hera spacecraft will rendezvous with Didymos four years after the impact. It will perform the measurements necessary to fully understand the effect of the DART impact on Dimorphos, in particular by measuring its mass, and investigating its internal structure, and thus determining the momentum transfer and detailed characterization of the crater left by DART.

2. The Hera Mission

Hera launch is planned for October 2024 and arrival at the Didymos system in early 2027. After arrival, it will release two cubesats, Juventas and Milani, and the three spacecraft will investigate the asteroid system for 6 months (see Figure 1). The mission is divided into several phases:

• The Early Characterisation Phase (6 weeks): Hera will stay around Didymos on hyperbolic arcs at a distance of 20-30 km. The goal is the determination of the global system properties (global shape of asteroids, gravity, dynamic properties).
• Payload Deposition Phase (4 weeks): Release and commissioning of the cubesats. The trajectories will be of the same type as during Early Characterisation Phase
• Detailed Characterisation Phase (4 weeks): Hera will orbit Disymos on hyperbolic arcs at distances of 8-20 km. Detailed investigations (mass of Dimorphos, subsurface characterization with radar).
• Close Observation Phase (6 weeks): Close flybys down to 4 km distance. Detailed characterization of surface properties and shape of DART impact crater.
• Experimental Phase (6 weeks): Close flybys down to 1 km distance from Dimorphos or less. High resolution observations of DART crater and other surface features. Landing of Cubesats on Dimorphos and of Hera on Didymos.

The following payload will study the surface, interior, and environment of the asteroid pair:

• Two Asteroid Framing Cameras (AFCs, visible imaging and navigation)
• The Hyperscout-H multispectral imager (spectral imaging 670 - 975 nm)
• The Thermal InfraRed Imager (TIRI, 8 - 14 μm), contributed by JAXA
• The Planetary Altimeter (PALT, Laser altimeter)
• The Radio Science Experiment (RSE)
• The JUventas RAdar (JURA), a monostatic radar operating at 50-70 MHz
• The Gravimeter GRASS on Juventas, to measure surface gravity after landing on Dimorphos
• The Asteroid SPECTrometer (ASPECT), a Fabry-Perot visible and near-IR imaging spectrometer on Milani
• The VISTA Thermogravimeter (Dust detection and Composition)

The Hera payload and cubesats have passed their Critical Design Reviews and are now being manufactured for delivery of the flight models in this year.  

   Figure 1: Overview of the Hera mission at (65803) Didymos.

3. Planetary Defence return

Hera will characterize in detail the properties of Dimorphos that are relevant for planetary defense. Its objectives related to the deflection demonstration are the following:

• Measuring the mass of Dimorphos to determine the momentum transfer efficiency from DART impact.
• Investigating in detail the crater produced by DART to improve our understanding of the cratering process and the mechanisms by which the crater formation drives the momentum transfer efficiency.
• Observing subtle dynamical effects (e.g. libration imposed by the impact, orbital and spin
  excitation of Dimorphos) that are difficult to detect for remote observers.
• Characterising the surface and interior of Dimorphos to allow scaling of the momentum transfer efficiency to different asteroids.

4. Science return

Even though its requirements are driven by planetary defence, Hera will also provide unique information on many current issues in asteroid science. The reason is that our knowledge of these fascinating objects is still poor, especially for the smallest ones. The recent data obtained by the JAXA Hayabusa2 and NASA OSIRIS-REx missions have revolutionized our understanding of carbonaceous Near-Earth Objects. Hera has the potential to perform similar as it will rendezvous for the first time with a binary asteroid. Dimorphos has a diameter of only 160 m. So far, no mission has visited such a small asteroid. Moreover, for the first time, internal and subsurface properties will be directly measured. From small asteroid internal and surface structures, through rubble-pile evolution, impact cratering physics, to the long-term effects of space weathering in the inner Solar System, Hera will have a major impact on many fields, providing answers to questions such as: How do binaries form? What does a 160 m-size rock in space look like? What is the surface composition? What are its internal properties? What are the surface structure and regolith mobility on both Didymos and Dimorphos? And what will be the size and the morphology of the crater left by DART?

These questions will be addressed by Hera as a natural outcome of its planetary defence investigations

5. Conclusion
The DART impact on Dimorphos and the accompanying observations by LICIACube and Earth-based observers, together with the detailed investigation of the Didymos system by Hera will be the first full scale asteroid deflection test of mankind.

How to cite: Küppers, M., Michel, P., Fitzsimmons, A., Green, S., Lazzarin, M., Sugita, S., Ulamec, S., Carnelli, I., and Martino, P. and the The Hera Investigation Team: The ESA Hera Mission: Investigating binary asteroid (65803) Didymos and the DART crater, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-192, https://doi.org/10.5194/epsc2022-192, 2022.

Introduction:  In late September 2022 the NASA mission DART will perform the first test of the kinetic impactor technique conceived to deflect an asteroid en route to Earth. With a mass of 650 kg and an impact velocity of about 6.6 km/s, DART is expected to change the binary orbital period of Dimorphos, the 160-m moon of Didymos Near-Earth Asteroid (NEA), by about 10 min, an effect that can be easily measured by ground-based telescopes [1] [2].

LICIACube: LICIACube (Light Italian Cubesat for Imaging of Asteroids) is the first purely Italian spacecraft to be operated in deep space. It is a 6U cubesat platform developed by the Argotec company and managed by the Italian Space Agengy (ASI) with the aim to contribute in the NASA DART Planetary Defence objective and to perform autonomous science at the asteroid [3]. LICIACube has been launched together with DART on November 2021: after a 10-months interplanetary cruise it will be released 10 days before the foreseen DART impact on Dimorphos and it will be guided along its fly-by trajectory with a closest approach (CA) of around 55 km from the Dimorphos’ surface (Fig. 1).

Figure 1 – The nominal LICIACube mission

LICIACube is equipped with two different payloads named LEIA (Liciacube Explorer Imaging for Asteroid) and LUKE (Liciacube Unit Key Explorer) (Fig. 2). High-resolution images, obtained by LEIA at the CA (up to 1.5 m/px) will allow us to study the surface morphology of Dimorphos and the presence of boulders/large blocks on its surface. The LUKE data (up to 8 m/px at CA, with a RGB filter system) will give us also the opportunity to investigate the composition of Dimorphos throughout spectrophotometric analyses. It will then be possible to map the surface composition of the object and to derive the surface heterogeneity at the observed scale.

After imaging the DART impact, during the fly-by the two instruments will allow us to investigate the nature of the target, explore the difference between the impact and non-impact regions, and to study the nature and the evolution of the produced plume, in order to deeply investigate the composition and the structure of the material composing a small double NEA.

Figure 2 – LICIACube and its payload

 After the Dimorphos fly-by, LICIACube will download the obtained images directly to Earth: the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Centre, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center.

Acknowledgements: The LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP F84I190012600).

References: [1] Rivkin A.S. et al., (2021) PSJ, in press. [2] Cheng A. F., et al. (2018) PSS, 157, 104. [3] Dotto E., et al. (2021) PSS 199, 105185.

How to cite: Ivanovski, S. L., Dotto, E., Della Corte, V., Ieva, S., Amoroso, M., Bertini, I., Brucato, J., Capannolo, A., Cotugno, B., Cremonese, G., Dall Ora, M., Don, P. D. J., Di Tana, V., Gai, I., Hasselmann, P. H., Impresario, G., Lavagna, M., Lucchetti, A., Mazzotta Epifani, E., and Meneghin, A. and the LICIACube and DART team members: Before the DART impact: LICIACube - The Light Italian Cubesat for Imaging of Asteroids, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1202, https://doi.org/10.5194/epsc2022-1202, 2022.

Instrument overview

The Light Italian Cubesat for Imaging of Asteroids (LICIACube) [1] is part of the NASA Double Asteroid Redirection Test (DART) [2], the first mission aiming to demonstrate the applicability of the kinetic impactor method for planetary defense. The mission was launched on 24 November 2021 to perform the impact experiment on Dimorphos, the small secondary of the binary asteroid (65803) Didymos, on September 26, 2022. The 6U LICIACube, stored as a piggyback of DART spacecraft, is the first Italian mission operating in deep space managed by the Italian Space Agency (ASI) that will witness the effects of DART impact on Dimorphos. 
The Italian cubesat will perform an autonomous fly-by of the binary system with several scientific objectives: (i) to directly witness the impact of DART spacecraft on Dimorphos surface; (ii) to study the ejecta plume over its evolution in time and under varied phase angles in order to estimate the properties of the plume and the evolution of its grain distribution; (iii) to study the impact site with sufficient resolution to allow the measurements of  size, color and morphology of the artificial crater formed in the aftermath; (iv) to perform observations of the non-impacted hemisphere to increase  accuracy in the determination of the target’s shape and volume and for overall investigation of the surface. 
To fulfill such key objectives, LICIACube is carrying a suite of cameras composed by the LICIACube Explorer Imaging for Asteroid (LEIA), a narrow FoV camera, and LUKE, a Gecko imager provided by SCS space company. The 70.55 mm focal length of LUKE is designed to work in focus between 400 m to infinity. FoV is ±5° and IFoV 78 μrad/px with a spatial scale about 4 m/px at 51 km. LUKE is equipped with a front illuminated CMOS detector (ams CMV2000), the pixel pitch is 5.5 microns and images will be 1088x2048 pixels. It is an RGB camera with a Bayer pattern filter. 
LICIACube will be released by DART about 10 days before the impact and it will autonomously fly to the target, reaching a minimum distance of about 51 km (Closest Approach). During the fly-by, both LEIA and LUKE cameras will acquire 228 RGB image (for a simulated example see Figure 1) of the impacted and non-impacted target sides with a resolution ranging from 71 m/px down to 4.3 m/px.

Fig 1 Original frame and zoom-in of analog image of Didymos-Dimorphos system, simulated using the shape models of asteroids Ryugu and Itokawa, as observed by LUKE. 

Expected scientific analysis

Several activities in support of the scientific analysis are ongoing and more will be done once data will be downloaded [3]. Four main studies are linked with LUKE science: (i) laboratory support to data interpretation, (ii) multivariate statistical analysis of LUKE data, (iii) photometric phase curve analysis, and (iv) study of the plume evolution.

The support of laboratory analyses will be continuous across all the LICIACube mission phases to support the interpretation of the data collected by the LICIACube payload. Main activities will concern RGB measurements with LUKE-like RGB cameras and analysis of LUKE RGB bands spectral response with existing and new laboratory spectroscopic measurements in LUKE wavelength range. In detail we will proceed with: 1) the creation of a dedicated database to support the investigation on surface composition; 2) the study of surface processes able to modify the appearance of Didymos and Dimorphos surfaces.

Moreover, by using multi-color images acquired by LUKE we will analyze the features on Dimorphos and Didymos surfaces both from a geomorphological and a compositional perspective. By applying the G-Mode method we will search for possible heterogeneities/variegations on the surface characterizing regions with the same spectral behavior. This analysis is therefore fundamental to infer the formation and the evolution of this binary system. Indeed, binary asteroids' possible compositional differences are still poorly investigated due to the difficulties in ground-based observation and the absence of dedicated space missions.

In addition, during about 10 days in the nominal operation schedule of LICIACube, LUKE is expected to capture images of the Didymos-Dimorphos system ranging from 42 to 120 degrees of phase angle and down to about 51 km. Didymos will become resolved by 4 pixels about 7 minutes before the impact, while Dimorphos will reach the same spatial resolution only 42 seconds after. The photometric phase curve will reveal some scattering properties of the granular surface medium. Within this phase angle coverage, the surface texture, particles’ irregularities, multiple scattering, and multi-scale roughness are the dominant properties.

LUKE data will help improve our knowledge on asteroid binary systems in particular on their origin and evolution. Expected results promise to significantly advance our understanding of these small rocky bodies in combination with the other data obtained by the mission both from the spacecraft and from ground observations.

Acknowledgements
The LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP F84I190012600). This work utilizes spectra downloaded by NASA RELAB facility at Brown University. All the authors have contributed to the present work. The entire LICIACube Team made this paper possible. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References
[1] Dotto et al. 2021, PSS, 199, 105185
[2] Rivkin et al. 2021, PSJ, 2, 5, 173
[3] Poggiali et al. 2022, PSJ, submitted

How to cite: Poggiali, G., Brucato, J. R., Hasselmann, P. H., Ieva, S., Perna, D., Pajola, M., Lucchetti, A., Deshapriya, J. D. P., Della Corte, V., Mazzotta Epifani, E., Rossi, A., Ivanovski, S. L., Zinzi, A., Meneghin, A., Amoroso, M., Pirrotta, S., Impresario, G., and Dotto, E. and the LICIACube Team: Expected investigation of the (65803) Didymos-Dimorphos system using the RGB spectrophotometry dataset from LICIACube Unit Key Explorer (LUKE) wide-angle camera, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-887, https://doi.org/10.5194/epsc2022-887, 2022.

Introduction: Near-Earth objects (NEOs), due to their proximity to our planet, represent one of the most accessible bodies in the whole Solar System. Their investigation can offer answers to several pressing questions in modern planetology (regarding, e.g., planetary formation, delivery of water and organics to the early Earth, and emergence of life). However, NEOs can also represent a risk for human civilization, since few of them can be potential impactors [1].

The binary Didymos system: The binary NEO Didymos is composed of a main body (68503) Didymos and its satellite, later renamed Dimorphos. Recent studies estimate that nearly 15% of large NEOs (> 200 m) should be binaries [2]. At the moment, the most current explanation involves the reaccumulation of a body following a rotational disruption, probably as a result of the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. However, other mechanisms are predicted for different sizes and populations of small bodies (capture, collision and tidal processes) [3].

Binary NEOs can also be helpful to demonstrate the applicability of the most mature technique for impact mitigation, i.e. the kinetic impactor [4]. To this purpose, the NASA Double Asteroid Redirection Test (DART) has been approved to be the first demonstration of an hazard mitigation of an asteroid by using a kinetic impactor [5].

The DART/LICIACube mission: The DART spacecraft, launched on November 23^rd 2021, will impact Dimorphos, the smaller member of the Didymos binary asteroid system, on September 26^th 2022. Hosted as a piggyback during the 15 months of DART interplanetary cruise there will also be LICIACube, the Light Italian Cubesat for Imaging of Asteroids [6], which is a 6U cubesat space mission supported by the Italian Space Agency (ASI). LICIACube will be released in the proximity of the target and will perform an autonomous fly-by of the Didymos system, probing the DART impact and reaching several scientific goals, such as: i) witness with its optical payloads (LUKE & LEIA, [6]) the impact of DART, ii) study the structure and evolution of the ejecta plume, and iii) acquire images of the event’s aftermath on the impacted hemisphere, as well as characterizing the non-impacted one.

Ground-based characterization of the Didymos system prior to the impact: Data available in literature for the target of the DART/LICIACube mission, the binary NEO 65803 Didymos, is scarce. Only few spectra were taken during the latest observational windows in 2003 and 2019. The limited compositional data available for this NEO suggests a possible silicate composition [7], and an affinity with its best meteorite analogue, the L- and LL-ordinary chondrites [8]. A detailed spectral characterization in this case is crucial due to its binary nature, in order to disentangle the contribution of the primary from the secondary body and asses the heterogeneity of the surface composition in the light of the DART/LICIACube mission.

A potential heterogeneity on Didymos: During the latest observational window in 2021 (the last before the DART impact) we obtained for the first time a complete rotational characterization of the system via visible spectroscopy. While the observations confirm an affinity with silicate material and ordinary chondrites, data analysis shows a subtle but persistent spectral slope variation, computed in this case between 0.5 and 0.7 µm. This slope variation is also confirmed by comparing our most recent data with spectra obtained during the previous 2003 and 2019 passages (see Fig. 1).

Figure 1 – Comparison between a representative set of spectra collected during our observations in 2021, together with previously observed spectra of the Didymos system retrieved in literature. a) Spectrum #1 together with the one observed by J. De Leon in 2019 in red (private communication); b) Spectrum #5 together with one from [9] in green; right) spectrum #8 with one retrieved by [7] in cyan. Published originally in [10].

Figure 2 – Comparison between three representative Didymos spectra observed at TNG during the 2021 observational window with their best meteorite analogue. Best analogue is represented by either L-, LL-ordinary chondrites or pure olivine and hypersthene spectra, the main components of L-/LL ordinary chondrites, suggesting that variability is probably related with different concentration of these minerals. Published originally in [10].

Future work: New spectral characterization already scheduled for 2022 in the unexplored NIR range will be helpful to confirm these promising results. We will compare this new data with RGB-images obtained by LUKE camera on board of LICIACube, to look for potential heterogeneity of the surface. Moreover, we will take advantage of the unprecedented brightness of the system during the 2022 observational window (brighter than the last two decades, V_mag = 14.5) to further investigate the contribution of Dimorphos, constrain potential similarity/difference with respect to Didiymos, and assess eventual mineralogical changes induced to the system by DART impact. These observations will be the ideal benchmark also in light of the Hera mission [12], which will visit the system in 2026.

Acknowledgments: This research was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0).

References: [1] Perna D., et al., 2013, A&A Rev. 21, 65; [2] Margot, J. L et al. 2015, Ast. IV, 355; [3] Walsh, K. J. & Jacobson, S. A., Ast. IV, 454; [4] Cheng, A. F. et al. 2018, P&SS,157,104; [5] Rivkin A.S. et al., (2021) [6] Dotto E. et al., 2021, PSS, 199, 105185; [7] De Leon J., et al., 2010, A&A 517, A23; [8] Dunn, T. L., et al., 2013, Icarus, 222, 273; [9] Binzel, R.P. et al., 2004, Icarus, 170, 25; [10] Ieva, S. et al., 2022, PSJ, submitted. [11] Michel, P. et al., 2022, PSJ, submitted.

How to cite: Ieva, S., Mazzotta Epifani, E., Perna, D., Dall'Ora, M., Petropoulou, V., Prasanna Deshapriya, J. D., Hasselmann, P., Rossi, A., Poggiali, G., Brucato, J. R., Pajola, M., Lucchetti, A., Ivanovski, S. L., Palumbo, P., Della Corte, V., Zinzi, A., Dotto, E., Rivkin, A., Thomas, C., and DeLeon, J. and the LICIACube team: DIDYMOS AT DIFFERENT ROTATIONAL PHASES: a subtle but persistent spectral variability, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-897, https://doi.org/10.5194/epsc2022-897, 2022.

The ESA HERA mission approved by the last ESA council Space19+ will be launched in 2024 to deeply investigate the Didymos binary system and especially its moonlet [1]. Onboard the Juventas small platform, The Juventas Radar -JuRa- will fathom Didymoon and provide the first direct observation of an asteroid deep interior. The characterization of the asteroids’ internal structure is crucial for science, planetary defense and exploration [2].

In 2022, DART/NASA will impact the moonlet to quantify the mechanical response of the body, mainly from ground-based observation [3]. Five years later, HERA/ESA is a unique opportunity to observe in detail the bodies, the crater and the ejecta in order to better constrain mechanical models providing a global characterization of the binary system: shape, density, dynamic properties, thermal properties and composition [4]. The Hera mothercraft will carry two CubeSats, Juventas and Milani. The small spacecraft Juventas will investigate the asteroids’ internal structure. Information about the internal structure is crucial for science, planetary defense and exploration since our current knowledge relies entirely on inferences from remote sensing observations of the surface and theoretical modeling [2].

JuRa is a monostatic radar, BPSK coded at 60MHz carrier frequency and 20MHz bandwidth, inherited from CONSERT/Rosetta [5], [6] and redesigned in the frame of the AIDA/AIM phase A/B [4], [7]. The instrument design is under validation for a flight model delivery end of 2022.

JuRa maps the backscatter coefficient (sigma zero - s₀) of the surface or subsurface, which quantifies the returned power per surface or volume unit. It is related to the degree of heterogeneity at the scale of the wavelength and to the dielectric contrast of heterogeneities, giving access to both, the sub-meter texture of the constituent material and larger scale structures.

• The first objective of JuRA is to characterize the moonlet’s interior, to identify internal geological structure such as layers, voids and sub-aggregates, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution and heterogeneity at from submetric to global scale.
• The second objective is to estimate the average permittivity and to monitor its spatial variation in order to retrieve information on its composition and porosity. Radar bypasses the near surface alteration by space-weathering and thermal-cycling as observed with optical remote sensing. The observation of the structure and composition of the moonlet will provide constraints on the mechanical model of the impact process.
• The same characterization applied to the main asteroid of the binary system is among the secondary objectives, to detect differences in texture and composition. When compared to the observation of the moonlet, it will constraint the model of binary system formation to discriminate between progressive versus catastrophic process and more generally on the stability conditions of the system.

In this talk, we will review the JuRa science objectives and the instrument development status. We will show the results of the model end-to-end tests and the corresponding instrument performances. Then we will present the proposed operation strategy and the developed approaches for data processing.

Acknowledgments

• Hera is the ESA contribution to the AIDA collaboration.
• Juventas and JuRa are developed under ESA contract supported by national agencies.
• JuRa is built by Emtronix (LU), UGA/IPAG (FR), TU Dresden (DE), Astronika (PL) and FZ (CZ). Juventas is built by Gomspace (LU). Juventas navigation plan is developed by GMV (RO)
• This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 870377 (project NEO-MAPP).

References

[1]          P. Michel et al., « European component of the AIDA mission to a binary asteroid: Characterization and interpretation of the impact of the DART mission », Advances in Space Research, vol. 62, n^o 8, p. 2261‑2272, oct. 2018, doi: 10.1016/j.asr.2017.12.020.

[2]          A. Herique et al., « Direct observations of asteroid interior and regolith structure: Science measurement requirements », Advances in Space Research, vol. 62, n^o 8, p. 2141‑2162, oct. 2018, doi: 10.1016/j.asr.2017.10.020.

[3]          A. F. Cheng et al., « Asteroid Impact & Deflection Assessment mission: Kinetic impactor », Planetary and Space Science, vol. 121, p. 27‑35, févr. 2016, doi: 10.1016/j.pss.2015.12.004.

[4]          P. Michel et al., « Science case for the Asteroid Impact Mission (AIM): A component of the Asteroid Impact & Deflection Assessment (AIDA) mission », Advances in Space Research, vol. 57, n^o 12, p. 2529‑2547, juin 2016, doi: 10.1016/j.asr.2016.03.031.

[5]          W. Kofman et al., « The Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT): A Short Description of the Instrument and of the Commissioning Stages », Space Science Reviews, vol. 128, n^o 1‑4, p. 413‑432, mai 2007, doi: 10.1007/s11214-006-9034-9.

[6]          W. Kofman et al., « Properties of the 67P/Churyumov-Gerasimenko interior revealed by CONSERT radar », Science, vol. 349, n^o 6247, p. aab0639, juill. 2015, doi: 10.1126/science.aab0639.

[7]          A. Herique et al., « A radar package for asteroid subsurface investigations: Implications of implementing and integration into the MASCOT nanoscale landing platform from science requirements to baseline design », Acta Astronautica, mars 2018, doi: 10.1016/j.actaastro.2018.03.058.

How to cite: Herique, A., Plettemeier, D., and Kofman, W. and the JuRa Team: JuRa: the Juventas Radar on Hera to fathom Didymoon, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-487, https://doi.org/10.5194/epsc2022-487, 2022.

Research into the orbital and physical properties near-Earth asteroids (NEAs) is important as these objects can reveal information about the origin and history of our planetary system.
Here we present our findings regarding the physical characteristics of the near Earth asteroids (NEAs) 2005 UD and 2001 SG286. The 2005 UD is currently a possible target for the DESTINY+ space mission, along with (3200) Phaeton which seems to share similar dynamic and physical characteristics. However, compared to Phaethon, there is still limited data available regarding 2005 UD. On the other hand, 2001 SG286 is another very interesting object, feasible as target for a sample-return mission which required additional observations to firmly establish its nature and composition.
In order to obtain the light-curves of these objects, we used the 2.5m Issac Newton Telescope (INT) equipped with Wide Field Camera CCD4 and the Sloan photometric filters. The visible spectrum of 2005 UD was captured using the INT with the Intermediate Dispersion Spectrograph (IDS) instrument. Furthermore, we used the 3.58m Telescopio Nazionale Galileo (TNG) equipped with the NICS instrument and the AMICI prism disperser to capture its infrared spectrum. The spectrum of 2001 SG286 was acquired using the 10.4m Gran Telescopio Canarias equipped with Optical System for Imaging and low Resolution Integrated Spectroscopy (OSIRIS) instrument. The observations of both objects were made during their recent favorable approaches (October 2018 for 2005 UD and October 2020 for 2001 SG 286).
For photometric data reduction we used the PHOTOMETRY PIPELINE by Michael Mommert and the MPO CANOPUS software with the reference stars from the GAIA and APASS catalogues, respectively. The nightly zero points were found to be consistent up to 0.1 magnitudes. MPO Canopus was finally used for the rotation period analysis, using the FALC (Fourier Analysis of Light Curves) algorithm. The light-curve plots are shown below. The “Reduced Magnitude” on the Y axis represents the Sloan filter magnitude values that have been corrected from sky magnitudes to unity distance by applying –5 * log(rR) to the initial measurements, where r is the Earth-asteroid distance and R is the Sun-asteroid distance. The X axis represents the rotational phase.
For 2005 UD, we found that a trimodal solution with a period of 7.85 hours is the best fit with polynomial orders ranging from 3 to 8, taking into account the INT data. This solution was previously suggested by Moskovitz in his presentation at PERC Int'l Symposium on Dust & Parent Bodies 2019 (IDP 2019) as a valid possibility, besides the predominant value of 5.23 hours currently found in the literature [1].

As for 2001 SG286, our analysis indicates that it is a non-principal axis slow rotator (tumbler), with overlapped rotational periods of 12.3 and 18.45 hours. Although we searched for a binary solution, we could not get a compelling result. Moreover, probabilistically there is a low chance of finding a companion given that the majority of binary asteroids are fast rotators.

2005 UD presents a C-type spectrum according to Bus-DeMeo classification.
In this case, we used the infrared data to calculate the thermal excess according to the thermal model described by Rivkin et al [2]. By further applying the aforementioned model and taking into account the heliocentric distance of the object at the time of the observation, we determined the geometrical albedo of 2005 UD to be pV = 0.06, which is in agreement to the latest estimate of Masiero et al [3].

On the other hand, the high quality spectral data obtained with GTC allowed us to firmly determine that 2001 SG286 is an S-type asteroid according to Bus-DeMeo classification, a result which is not in agreement with previous studies[4][5].

References:
1. B. Warner and R. Stephens “Near-Earth Asteroid Lightcurve Analysis at the Center for Solar System Studies: 2019 July-September”, Minor Planet Bull. 2020 Jan;47(1):23-34.
2. A.S. Rivkin et al. “Constraining near-Earth object albedos using near-infrared spectroscopy”, Icarus 175 (2005) 175–180.
3. J. R. Masiero et al. “Asteroid Diameters and Albedos from NEOWISE Reactivation Mission Years 4 and 5”, The Planetary Science Journal, 1:5, 2020 March
4. Binzel et al. “Dynamical and compositional assessment of near-Earth object mission targets”, Meteoritics & Planetary Science 39, Nr 3, 351–366 (2004)
5. Popescu, M. et al. “Spectral properties of eight near-Earth asteroids”, A&A 535, A15 (2011)

Acknowledgements:

The work of RMG, and MP was supported by a grant of the Romanian National Authority for Scientific Research – UEFISCDI, project number PN-III-P1-1.1- TE-2019-1504. The work of MP, JdL, JL, is made in the framework of EU-funded project ”NEOROCKS - The NEO Rapid Observation, Characterization and Key Simulations project”, SU-SPACE-23-SEC-2019 from the Horizon 2020 - Work Programme 2018-2020, under grant agreement No 870403

How to cite: Gherase, R., Vaduvescu, O., Wilson, T., Popescu, M., de León, J., Lorenzi, V., Licandro, J., Morate, D., Aznar, A., and Simion, G.: The Physical Properties of the Near Earth Asteroids 2005 UD and 2001 SG286, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1056, https://doi.org/10.5194/epsc2022-1056, 2022.

Near-Earth objects (NEOs) deserve our attention because they pose an impact risk for Earth. A good example is the Chicxulub impactor that produced the Cretaceous/Tertiary mass extinction event 65 Myr ago (Bottke et al. 2007). Up to now, more than 1 milion of asteroids have been discovered, and about 28,700 are cataloged as NEOs. This number steadily increases every month. Even if this currently known population of NEOs does not pose a direct threat to humanity within the next century, we are not able to assert that tomorrow we will not discover an asteroid capable of wiping out life on Earth in the next years.

Within the NEO population there is a subclass defined potentially hazardous asteroids (PHAs). These are objects with an orbit that can make close approaches to the Earth (whose minimum orbit intersection distance, or MOID, to Earth’s orbit is smaller than 0.05 AU), and large enough (absolute magnitude H ≤ 22, or equivalent diameter above ∼140 m, assuming the average NEO albedo of 0.14) to cause significant regional damage in the event of impact. Currently, more than 2200 NEAs are classified as PHAs.

Any mitigation strategy designed for a potential impact is dependent on the ability to determine the asteroid’s physical properties (Perna et al. 2016): the damage produced by a possible collision will mainly depend on the speed of the impact, the size of the object, and its composition. In this context, the knowledge of the physical properties of PHAs is still poor, with less than 15% having their taxonomies determined (∼300 objects). Due to this, improving our understanding on PHAs and their composition is essential for planning space-missions aimed to develop preventive actions against potential impacts (e. g. Cheng et al. 2018).

For the present work, we have investigated the physical nature of several PHAs, using data obtained within the framework of the Visible NEAs Observations Survey (ViNOS). We analyzed and characterized a sample comprised of 14 of these objects. To conduct this study, we obtained visible spectra of these 14 PHAs in the 0.5-0.9 μm region using the 2.5m Nordic Optical Telescope, located at the El Roque De Los Muchachos Observatory in La Palma (Spain). The resulting spectra were combined with their corresponding near-infrared counterparts, available in the literature from SMASS. We performed a taxonomical classification of the spectra, and computed several diagnostic spectral parameters (slopes, band centres, and band area ratios). We also compared the spectra with laboratory spectra of meteorites from the RELAB database. Among the studied sample of PHAs, approximately 90% of the objects (13 out of 14) were classified as silicaceous (S-types and subclasses). Only one object, 489486, was classified as carbonaceous. Five of the studied PHAs did not previously have taxonomical classifications. The comparisons of the silicaceous PHAs with meteoritic spectra all yielded ordinary chondrites (OCs) as the best match for meteoritic analogs, and the computed mineralogy of all of our targets is consistent with this results (see Fig. 1).

Fig. 1. Distribution of the studied asteroids BAR versus Band Center I space. The enclosed regions are taken from Dunn et al. (2013), which follow the results of Gaffey et al. (1993), Burbine et al. (2001), and Cloutis et al. (2010). Asteroids with two NIR spectra, and thus, two sets of spectral parameters, are connected by a dashed line. The numbers represent the corresponding object (when repeated, refers to its second spectrum).

How to cite: Morate, D., Popescu, M., De León, J., and Licandro, J.: Mineralogical analysis of 14 PHAs from ViNOS data, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-722, https://doi.org/10.5194/epsc2022-722, 2022.

The International Year of Planetary Defense 2029 (IYPD2029) will be a global raising awareness opportunity of protecting our planet Earth against possible hazards from Space, such as asteroids, the science behind it, and its contributions to ensuring human security, stimulating worldwide interest in asteroids not only as a source of information about the origins of our Universe but also about Planetary Defence and its role in keeping our planet safe and societies resilient to potential hazards from Space.

IYPD2029 will mark the monumental leap forward in a global effort in planetary defense and portray it as a peaceful global scientific endeavor that unites scientists in an international, multicultural family of scientists working together to defend our planet against the potential hazards of Near-Earth Objects. IYPD2029 is, first and foremost, an activity for the citizens of Planet Earth. It aims to convey the excitement of personal discovery, the pleasure of sharing fundamental knowledge about asteroids, comets, meteorites, Near Earth Objects and the value of the scientific culture.

The vast majority of IYPD2029 activities will take place on several levels: locally, nationally, regionally, and internationally. Several countries have already formed national committees to prepare activities for the close approach of the asteroid Apophis in 2029. These committees are collaborations between professional and amateur astronomers, science centers and science communicators. In this presentation, we aim to inform the community about the work that is underway and invite further partners to be involved and collaborate in the variety of planned efforts.

How to cite: Daou, D. and Koffler, R.: The International Year of Planetary Defence, 2029., Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-91, https://doi.org/10.5194/epsc2022-91, 2022.

(99942) Apophis is a near-Earth asteroid that will closely approach to Earth in 2029; the minimum geocentric distance will be about 38,000 km.  During the approach, the spin state of Apophis is expected to be altered by Earth's gravitation torque.  The exact change depends on the orientation of Apophis during the close approach.  Although the shape and spin-state model of Apophis was reconstructed from 2012/13 observations by Pravec et al. (2014, Icarus 233, 48),  the precision of rotation parameters they derived was not sufficient to predict the orientation for 2029.

We will present our analysis of photometric observations of Apophis that we carried out from 2020-11-16 to 2021-05-06 with the 1.54-m Danish telescope at La Silla.  By applying the lightcurve inversion technique of Kaasalainen (2001, A&A 376, 302), we reconstructed the spin state and shape of Apophis.  This new model agrees with the one reconstructed by Pravec et al. (2014) and with an updated model published by Lee et al. (2022, arXiv:2204.02540).  We aimed to invert both the 2012-2013 and 2020-2021 data together and reconstruct the Apophis spin state with high precision.  The long interval of observations would enable us to precisely determine the rotation and precession periods and thus reliably predict  the orientation of Apophis during its 2029 flyby, calculate a change of its spin state, and predict how the Yarkovsky effect will influence  the post-encounter orbit of Apophis, which is crucial for its post-2029 impact predictions.

How to cite: Durech, J., Vokrouhlicky, D., Pravec, P., Hornoch, K., Kusnirak, P., Fatka, P., and Kucakova, H.: Shape and spin-state model of asteroid (99942) Apophis reconstructed from photometric observations in 2020/21, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-36, https://doi.org/10.5194/epsc2022-36, 2022.

Apophis, the Asteroid 2004 MN4 is one of the Near-Earth Object (NEO) with regular and very close Earth en-
counters. During the next encounter in 2029, Apophis will flyby by about a distance of 36000 km above the surface
of Earth. During this close flyby, the orbit and dynamics of Apophis is expected to vary significantly due to gravi-
tational interactions with the Earth (Scheeres et al., 2006; Souchay, Lhotka, et al., 2018; Souchay, Souami, et al.,
2014). The surface is not expected to undergo catastrophic disruption, however it may be subject to tidal stresses
and localized failures resulting in debris (Scheeres et al., 2006). The variations of orbital parameters, i.e. spin,
obliquity, longitudinal and latitudinal librations am increase considerably during the closest-approach epoch which
will be observable in real time by groundbased radar and telescopes.

Here we present the numerical simulations using the full-two-body (F2BP), where the rotational and translational
dynamics are fully coupled. F2BP can fully capture the system’s dynamics taking into account the objects’ irregular
shapes and the close proximity of the components . The system’s dynamical evolution is especially sensitive to the
shapes and initial positions and orientations of each component. Here we use the open source F2BP code GUBAS
(Davis and Scheeres, 2020). The initial position and speed come from Horizon System from the Jet Propulsion
Laboratory, the initial orientations from Pravec et al., 2014 and the system is propagated using a LGVI integrator.
We use a radar based shape model for Apophis (Brozovic et al., 2018) while the Earth is modeled by an ellipsoid
of revolution.

Starting from when Apophis enters the sphere of influence of Earth until it leaves it, we propagate the dynamical
parameters. The results shows significant changes in the rotational state of Apophis already few hours before the
closest-approach. In addition to rotational and orbital parameters, we calculate also the changes in surface gravity
and dynamical slopes during the close encounter. The changes in Apophis rotation and surface changes, including
potential localized failures across its surface, are important parameters for planetary defense missions since they
provide information on otherwise inaccessible interior and mechanical properties of the asteroids.

References

Scheeres, D. J., et al. (2006). Dynamical configuration of binary near-earth asteroid (66391) 1999 KW4. Science, 314 (5803), 1280–1283.

Souchay, J., Lhotka, C., et al. (2018). Changes of spin axis andrate of the asteroid (99942) Apophis during the 2029 close encounter with Earth: A constrained model. Astronomy and Astrophysics, 617, 1–11.

Souchay, J., Souami, D., et al. (2014). Rotational changes of the asteroid 99942 Apophis during the 2029 close encounter with Earth. Astronomy and Astrophysics, 563, 1–6.

Davis, A. B., & Scheeres, D. J. (2020). Doubly synchronous binary asteroid mass parameter. Icarus, 341.

Pravec, P., et al. (2014). The tumbling spin state of (99942) Apophis. Icarus, 233, 48–60.

Brozovi ́c, M., et al. (2018). Goldstone and Arecibo radar observations of (99942) Apophis in 2012–2013. Icarus, 300, 115–128.

How to cite: Noiset, G., Tasev, E., and Karatekin, Ö.: Changes in Apophis rotation and surface gravity during its 2029 Earth flyby, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1159, https://doi.org/10.5194/epsc2022-1159, 2022.

Science rationale: Our knowledge of the internal structure of asteroids entirely relies on inferences from remote sensing observations of the surface combined with theoretical modeling [1]. Is Apophis a rubble-pile, as expected, or a monolithic rock, and how high is the porosity? What is the typical size of the constituent blocks? Are these blocks homogeneous or heterogeneous? If Apophis is bilobed, how does the material differ between each lobe?

After many asteroid rendezvous and fly-by missions from different nations, these crucial and yet basic questions remain open. Direct measurements of the deep interior structure and composition are needed to better understand the accretion and dynamical evolution of asteroids in general. These measurements at Apophis in particular will directly improve our ability to understand and predict stability conditions as well as to interpret the response of Apophis to the tidal forces induced by its close approach to the Earth. This information is also crucial to plan any interaction of a spacecraft with Apophis and other similar asteroids, especially for Planetary Defense purposes.

Direct observations of asteroid subsurfaces in general are also required to better model the dynamics of granular materials in low gravity, and to determine material composition and mineralogy, while space weathering and thermal cycling alter surface properties as observed by optical remote sensing.

DROID mission concept: Radar observation of Apophis from a spacecraft is the most mature technique capable of achieving these objectives, by providing a direct measurement of its interior. This is the goal of DROID – (Distributed Radar Observations of Interior Distributions), a mission concept developed in collaboration between NASA JPL and CNES [2] and discussed in more detail in the accompanying presentation [3].

The DROID mothership will release two CubeSats each carrying a low-frequency radar. The radar will be a version of JuRa (60 MHz) [4], modified to operate in a bistatic mode and using an inter-satellite link as a synchronization channel. The mothership and the two CubeSats (daughtercraft) will also have cameras for both science and navigation.

Radar observation: Each daughtercraft radar can operate in a monostatic mode, or in a bistatic mode using the two platforms to measure the signal transmitted throughout Apophis, as CONSERT did onboard Rosetta orbiter and Philae lander [1,5,6,7].

Monostatic radar. A radar at 60 MHz offers a larger penetration (up to 100 meters or more) with a limited resolution (≈5 m). It corresponds to the instrument under implementation for the Juventas Cubesat on the Hera/ESA mission [4].

Furthermore, multi-pass processing allows us to build a 3D tomographic image of the interior to identify internal structure like layers, voids and sub-aggregates, to bring out the aggregate structure and to characterize its constituent blocks in terms of size distribution and heterogeneity at different scales (from sub-metric to global). Initial dynamics modeling of the two Cubesats orbiting Apophis at 3 body radii indicates that 20% full Doppler coverage is possible in 40 days [2,8].

Shallow subsurface characterization and radar images to support the shape modeling are also possible in this configuration, but with degraded performance due to a limited resolution.

Bistatic radar. The bistatic radar will firstly measure the signal in transmission, allowing us to achieve a direct measurement of the dielectric permittivity, which is related to composition and microporosity [6]. This objective is less demanding in terms of data volume and operation compared to full bistatic coverage. Partial transmission coverage will provide slices of the body with average characterization and its special variability. With dense coverage, benefiting from a larger diversity of observation angles, the bistatic mode will allow a complete 3D tomography [8,9]. In general, multi-angular acquisition allows for a better decorrelation of the size effect and permittivity contrast in the return power.

Ground-to-space: In addition to radar observation at close proximity, there is the possibility for joint ground-to-space radar observations at the epoch of the Apophis close approach. [10]. Such measurements would make use of high-power transmitters or sensitive radio astronomy observatories on Earth [11]. Ground-to-space configurations would be used to collect echoes in unique bistatic configurations or to collect echoes during spacecraft maneuvers at close approach (e.g., required spacecraft stand-off).

Acknowledgement: The research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).

References:

[1] A. Herique et al. (2018) ASR 62, 2141‑2162., [2] R. Amini et al. (2022) Apophis T-7, #2012, [3] C. Raymond et al. (2022) this meeting., [4] A. Herique et al. (2022) JuRA radar, EPSC, [5] W. Kofman et al. (2015) Science 349, aab0639.,[6] Herique et al. (2016) MNRAS 462, S516‑S532., [7] A. Herique et al. (2019) A&A 630, A6., [8] M. Haynes et al. (2021) ASR 68 (9), [9] M. Haynes et al. (2021) LPSC #1295, [10] A. Herique et al. (2019) Apophis T-9 #2029, [11] M. Haynes et al (2022) Apophis T-7 #2020

How to cite: Herique, A., Adell, P., Amini, R., Davidsson, B., Haynes, M., Fesq, L., Lorda, L., Michel, P., Raymond, C., and Verdier, N.: DROID: Bistatic low-frequency radar sounding of 99942 Apophis in 2029, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-474, https://doi.org/10.5194/epsc2022-474, 2022.

Introduction:  The close approach of asteroid (99942) Apophis on April 13, 2029 presents a unique opportunity to achieve breakthrough science and strengthen planetary defense goals. 

As discussed in [1], low-frequency (VHF) radar observations can probe the interior structure of small bodies, as demonstrated by CONSERT at comet 67P [2, 3], and the planned JuRa low frequency radar on Hera/Juventas at the Didymos system—target of the DART mission. Radar measurements can determine the distribution of monolithic objects and voids within the body at 10’s of meter scale, which are critical for potential deflection and disruption attempts. This is best accomplished by multi-static, low frequency radar [4].

A mission concept to exploit the Apophis opportunity has been developed in a collaboration between NASA/JPL and CNES. The Distributed Radar Observations of Interior Distributions (DROID) mission would rendezvous with Apophis in late Summer 2028, seven months prior to Earth closest approach (ECA) and escort it through the encounter. A possible asteroid flyby on the way would delay arrival to late 2028 but still provide ample time for pre-ECA characterization. DROID’s measurements would determine the interior structure and properties, the body’s shape, morphology and rotation and observe any resolvable changes. DROID provides unique high fidelity in situ data that complements and enhances Earth-based optical and radar observations of Apophis, as well as data collected by OSIRIS-APEX which is due to rendezvous with Apophis 8 days after ECA.

As illustrated in Figure 1, DROID’s architecture calls for three spacecraft: an ESPA Grande-class Mothership and two 6U CubeSats. The Mothership carries the CubeSats to Apophis, achieves the rendezvous cruise trajectory, performs high resolution imaging, and acts as a Direct-to-Earth (DTE) node for the constellation. Once Apophis’s physical characteristics (shape, spin, gravity field) are sufficiently characterized, the Mothership deploys both CubeSats, which then insert themselves into coordinated low orbits to perform monostatic and bistatic radar observations.

Mission Goals:  The DROID mission has two primary goals. The first goal is to understand the interior structure of a rubble pile asteroid and implications for its formation, evolution and response to a deflection attempt. Objectives include determining shape and density, and determining the internal size, distribution, and arrangement of blocks and voids within Apophis. \

DROID’s second goal is to understand how close planetary encounters affect asteroids. DROID will provide critical pre-ECA imagery of Apophis that are necessary for change detection. Objectives include determining if material moves on the surface of Apophis during the Earth flyby, and determining how the spin state of Apophis changes during ECA.

Payload: Given the goals above, DROID employs four types of payloads distributed over three spacecraft (Figure 1). Objectives requiring surface imaging are to be met with a narrow-angle camera (NAC) on-board the Mothership spacecraft, whose focal plane is to be based on the Advanced CASPEX detector [5]. Additional wide-angle cameras (WACs) are carried on the two CubeSats for optical navigation.

The objective to map internal structure is achieved using the Low Frequency Radar (LFR) on the CubeSats. The LFR is baselined as a version of JuRa (60 MHz), [6], modified to operate in a bistatic mode [1]. Inter-Spacecraft Link (ISL) S-band transponders on all three spacecraft perform data transfer between CubeSats and Mothership, and synchronize the CubeSat clocks for accurate bistatic radar measurement. ISLs are also used with the Mothership’s DTE link to map the gravity field.

Mission Architecture: The DROID mission architecture is compatible with either direct launch or rideshare and will utilize heritage bus designs that can achieve the required propulsion performance. DROID’s 3.54 km/s ΔV requirement is similar to that of ESCAPADE, which uses bipropellant propulsion [7], DROID’s reference mission is constrained by a cruise trajectory insertion (CTI) window of about October-November 2027. Details of launch, CTI and cruise are provided in [8].

Operations: DROID arrives at Apophis around August-September 2028 (~December if it performs a precursor asteroid flyby) and executes a 0.30 km/s burn to reduce its relative velocity. During this phase, the Mothership NAC begins preliminary characterization of Apophis’s shape and spin. Approach imaging is then followed-up by several flyby maneuvers used to characterize the gravity field with DTE communication.

The Mothership then deploys the CubeSats, which maneuver into 2-5 body radii altitude, sun-synchronous terminator orbits using their own cold gas propulsion. Following CubeSat deployment, the Mothership positions itself in a 9 body radii altitude orbit where it continues its imaging investigations using the NAC. The CubeSats are positioned antipodally with ±15° margin in their relative position and continuously collect both monostatic and bistatic echoes. A 2-body radii altitude orbit will enable mapping of 20% of the 3D monostatic Doppler sampling at 60 MHz [9], within 40 days. Radar data products include: (1) 3D volumetric backscatter via monostatic/bistatic tomographic SAR, (2) average dielectric constant along interior bistatic ray paths with assessment of internal heterogeneity [10].

The configuration of the DROID constellation during ECA and Post-ECA operations is the subject of on-going studies. Major ECA drivers include positioning of cameras to maximize the likelihood of capturing surface changes and mitigating the risk of collisions with potential ejected debris. The major Post-ECA driver is escaping from Apophis orbit to a safe heliocentric orbit prior to depleting propellent in order to avoid any possibility of impacting the asteroid and perturbing its orbit.

Acknowledgments: This work is being carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA (80NM0018D0004), and at CNES. ©2022 California Institute of Technology. Government sponsorship acknowledged.

References: [1] Herique, A. et al (this meeting). [2] Barbin, Y. et al (1999) ASR 24. [3] Kofman, W. et al. (2007) SSR 128.  [4] Haynes, M. et al (2022) LPSC #1295. [5] Bezine, J. et al. (2021) ICSO 118520V. [6] Herique, A. et al (2020) EPSC. [7] French, R. (2019) AIAA SSC. [8] Amini, R. et al (2022) Apophis T-7 #2012. [9] Haynes, M. et al. (2021) ASR 68. [10] Herique, A. et al (2018) ASR 62.

How to cite: Raymond, C. A., Amini, R. B., Adell, P. C., Anderson, R., Bandyopadhyay, S., Bhaskaran, S., Davidsson, B. J. R., Esteve, F., Fesq, L., Haynes, M., Herique, A., Karimi, R., Keane, J. T., Lorda, L., Michel, P., Miller, R., and Virmontois, C.: DROID: A mission concept to accompany and characterize Apophis through its 2029 Earth closest approach, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-770, https://doi.org/10.5194/epsc2022-770, 2022.

Summary

In this work we present the design of the ATLAS (Asteroid Terrestrial-impact Last Alert System) unit that will be installed at Teide Observatory in Tenerife island (Spain). ATLAS-Teide will be built by the IAC and will operated as part of the ATLAS network in the framework of an operation and science exploitation agreement between the IAC and the ATLAS team at University of Hawaii.

ATLAS-Teide will be the first ATLAS unit based on COTS.  Its design is modular, each module (“building block”) consist of four Celestron RASA 11 telescopes that point to the same sky field, equipped with QHY600 CMOS cameras on a equatorial Direct Drive mount. Each module is equivalent to a 56cm effective diameter telescope and provides a 7.3 deg²  field of view and a 1.25 “/pix plate scale. ATLAS-Teide will consist of four ATLAS modules in a roll-off roof building. This configuration allows to cover the same sky area of the actual ATLAS telescopes.  This design is cheaper to build and maintain, and more flexible than the actual one.

The first ATLAS “building block” will be operational before the end of 2022 and we aim to complete the four modules of ATLAS-Teide by the end of 2023.

The ATLAS survey. 

ATLAS is an asteroid impact early warning system developed by the University of Hawaii and funded by NASA (see http://atlas.fallingstar.com). It consists of four 50cm telescopes (Hawaii ×2, Chile, South Africa). Each ATLAS unit maps 1/4 of the night sky, making 4 observations of each field at intervals of one hour, detecting objects of V=19.5-20 in 30s exposures. The software automatically detects moving targets, discovering hundreds of new objects every night. It also allows thousands of these bodies to be observed, taking very precise astronomical and photometric measurements, making ATLAS one of the most prolific asteroid database. ATLAS also processes the survey data to find stationary transient events, which are immediately reported to the IAU. These include supernovae, starbursts, and fast transients like GRB afterglows, etc. It also has an agreement with LIGO to search for electromagnetic counterparts of gravitational wave sources. ATLAS is among the 3 main projects of the world in reporting this type of event, with more than 300 supernova candidates found per year. 

ATLAS-Teide, the next generation of ATLAS units.
 
Late 2021, the IAC obtained funding from the Spanish “Subprograma Estatal de Infraestructuras de Investigación y Equipamiento Científico Técnico (Ref. EQC2021-007122-P)” to install an ATLAS unit at Teide Observatory. ATLAS-Teide will be the 5th ATLAS unit and will be operated together with the other four thanks to an agreement between the IAC and the Institute for Astronomy of the University of Hawaii (IfA-UH).
The design of the existing ATLAS is based on a telescope that is a variant of the Wright-Schmidt cameras that use a 50cm Schmidt correcting foil, a 65cm spherical primary mirror and a 3-element field correcting lens and a f/D=2.0. Each telescope is equipped with ACAM, a back-illuminated 110Mpix CCD camera providing a field of view of 5.4 x 5.4 deg and a plate scale of 1.88 “/pix. The design and construction of the telescope is of the company DFM Engineering Inc. After several interactions with DFM we have concluded that doing it with them is actually impossible and that it is necessary to opt for another design. 
After studying different options, we concluded that the best solution is to design a new ATLAS unit using a modular structure based on existing “commercial off-the-shelf” (COTS) equipment.  It should have capabilities similar to the telescopes that ATLAS currently has in terms of detection limit and sky area covered per night. The solution we found is cheaper to build and maintain, very efficient and more flexible than the current ATLAS. The new ATLAS design is based on optic telescope assemblies (OTAs) Celestron model RASA11, QHY600 CMOS cameras that use back-illuminated IMX-455 chip from SONY, with 9576*6388 pixels of 3.76 microns, and mounts of the L-series of the PlaneWave company. 

An ATLAS module or “building block” consists of four RASA 11 telescopes mounted together on a L-series PlaneWave equatorial mount (see Fig. 1), each one equipped with a QHY600 camera. All 4 telescopes point to the same field, so, combining the 4 images obtained simultaneously we have a system with an equivalent collecting area equivalent to that of a telescope with 56cm aperture (25.4% larger than that of the current ATLAS) with a field of view of 7,37 deg2 and a 1.25 “/pix plate scale. Considering the slightly lower sensitivity of the QHY cameras respect to ACAM the ATLAS module should detect objects of V=19.5-20 in 30s exposures.  

Figure 1- Schematic drawing of an ATLAS module.

To cover a similar sky area of the ATLAS units, ATLAS-Teide will consist of four ATLAS building blocks (16 OTAs RASA 11 in total) installed in a building with a roll-off roof structure. This design provides a similar sensitivity and sky coverage with a better plate scale. Moreover, it has several advantages: (i) its cost is a fraction of the cost of the old ones; (ii) it is much more flexible, allowing e.g. to point the four modules to the same field going 0.75 mag deeper; (iii) it is more efficient as in case some of its part fail the other modules can continue operating while the failed component is rapidly replaced, thus, if the COTS parts behave as promised, it is cheaper and easier to maintain and operate.

We are building the first ATLAS “building block” that will be operational before the end of 2022. It will be used to test its capabilities, develop all the needed software (control and image reduction) and the integration of the system into the ATLAS network.  The main aim is to complete the four modules of ATLAS-Teide by the end of 2023 and have it fully integrated in the ATLAS network early 2024. 

Acknowledgements. This project has received funding from the “Subprograma Estatal de Infraestructuras de Investigación y Equipamiento Científico Técnico (Ref. EQC2021-007122-P)”

How to cite: Licandro, J., Tonry, J., Serra-Ricart, M., R. Alarcon, M., and Denneau, L.: ATLAS-Teide: the next generation of ATLAS units for the Teide Observatory, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-634, https://doi.org/10.5194/epsc2022-634, 2022.

Understanding of shallow angle impacts (termed "oblique") comes from planetary bodies other than Earth, and also comes from modelling published by various workers over the past two decades or so. Another comparator source is the Southern Mt Lofty Ranges and Kangaroo Island impact in South Australia, which has not been dated other than being >35 mya. At previous conference attendances the case has been built that the oblique impact in SA was from the south rather than in the plane of the ecliptic, which raises the new question how common is such an event in the solar system. A digital elevation model from the Mars Orbiter Laser Altimeter has here been used to assess the occurrences of oblique impacts on Mars, focussing on the northern hemisphere. A large impact crater at 7 degrees N / 178 degrees E on Mars matches the criteria and additionally has the same impact approach direction as the Southern Mt Lofty Ranges craters, implying that the orbital plane of that impactor may have been similar or the same as that of the latter. The large scale of the particular crater identified on Mars forces a reassessment of the sizes of additional candidate Australia craters beyond the Southern Mt Lofty Ranges and Kangaroo Island impact sites. A digital elevation model of a central band of Australia, some 600 km wide, is analysed for candidate sites, while indicators of meteorite disintegration during oblique impacts are used to inform the study and to shortlist candidate sites.

How to cite: Moore, R.: Linking a large oblique-impact crater on Mars to the Southern Mt Lofty Ranges multiple impact event in South Australia – inference for latter event size and scope, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1201, https://doi.org/10.5194/epsc2022-1201, 2022.

NASA and its partners maintain a watch for near-Earth objects (NEOs), asteroids and comets that pass within Earth’s vicinity, as part of an ongoing effort to discover, catalog, and characterize these bodies and to determine if any pose an impact threat. NASA’s Planetary Defense Coordination Office (PDCO) is responsible for:

• Ensuring the early detection of potentially hazardous objects (PHOs) – asteroids and comets whose orbits are predicted to bring them within 0.05 astronomical units of Earth's orbit; and of a size large enough to reach Earth’s surface – that is, greater than perhaps 30 to 50 meters;
• Tracking and characterizing PHOs and issuing warnings about potential impacts;
• Providing timely and accurate communications about PHOs; and
• Performing as a lead coordination node in U.S. Government planning for response to an actual impact threat.

NASA’s current congressionally-mandated objective is to detect, track, and catalogue at least 90 percent of NEOs equal to or greater than 140 meters in size by 2020, and characterize the physical properties of a subset representative of the entire population. This mandate will likely not be met given current resources dedicated to the task; however significant progress is being made.

In this paper, we will report on the status of our program and the missions working to support our planetary defense coordination office. In addition, we will provide the latest detections and characterizations results. Our office continues to work diligently with our international partners to achieve our goals and continue to safeguard Earth with the latest technologies available.

How to cite: Daou, D., Johnson, L., and Fast, K.: Latest Update on NASA’s Planetary Defense Program, Europlanet Science Congress 2022, Granada, Spain, 18–23 Sep 2022, EPSC2022-1271, https://doi.org/10.5194/epsc2022-1271, 2022.