Philae Landing on Comet 67P/Churyumov-Gerasimenko – Planned Chirality Measurements and Ideas for the Future

Philae is a comet Lander, part of the ESA Rosetta Mission to comet 67P/Churyumov-Gerasimenko. After a ten year cruise through the solar system it successfully landed on the nucleus of the comet on November 12, 2014. Philae's payload consists of ten scientific instruments, including COSAC, an evolved gas analyser with the capability to differentiate chiral molecules. After the touchdown of Philae, the anchoring harpoons, which were expected to fix the lander to ground, did not work, Philae bounced in the low gravity environment, and only came to rest after a 2 hours " hop " in an unforeseen area on the comet surface. Although, the scientific instruments, including cameras, mass spectrometers (including the one of COSAC), a magnetometer and a radar instrument could be operated, and fascinating, unprecedented scientific results were obtained, it was not possible to collect a sample of the surface material and no gas chromatography measurement could be performed. Thus, the measurement of the chirality of molecules on comets is still to be done in the future. The paper gives an overview of the Philae mission and the attempts to measure chiral molecules with COSAC, and suggests future measurements with returned samples from the primitive asteroids (162173) Ryugu and (101955) Bennu with the spacecraft Hayabusa 2 (JAXA) and OSIRIS-REx (NASA), respectively. Both will reach their targets in 2018

Using Information from Rendezvous Missions for Best-Case Appraisals of Impact Damage to Planet Earth Caused by Natural Objects

The Asteroid Threat Assessment Project (ATAP), a part of NASAs Planetary Defense Coordination Office (PDCO) has the responsibility to appraise the range of surface damage by potential asteroid impacts on land or water. If a threat is realized, the project will provide appraisals to officials empowered to make decisions about potential mitigation actions. This paper describes a scenario for assessment of surface damage when characterization of an asteroid had been accomplished by a rendezvous mission that would be conducted by the international planetary defense community. It is shown that the combination of data from ground and in-situ measurements on an asteroid provides knowledge that can be used to pin-point its impact location and predict the level of devastation it would cause. The hypothetical asteroid 2017 PDC with a size range of 160 to 290 m in diameter to be discussed at the PDC 2017 is used as an example. In order of importance for appraising potential damage, information required is: (1) where will the surface impact occur? (2) what is the mass, shape and size of the asteroid and what is its entry state (speed and entry angle) at the 100 km atmospheric pierce point? And (3) is the asteroid a monolith or a rubble pile? If it is a rubble pile, what is its structure and heterogeneity from the surface and throughout its interior? Item (1) is of first order importance to determine levels of devastation (loss of life and infrastructure damage) because it varies strongly on the impact location. Items (2) and (3) are used as inputs for ATAPs simulations to define the level of surface hazards: winds, overpressure, thermal exposure; all created by the deposition of energy during the objects atmospheric flight, andor cratering. Topics presented in this paper include: (i) the devastation predicted by 2017 PDCs impact on land based on initial observations using ATAPs risk assessment capability, (ii) how information corresponding to items (1) to (3) could be obtained from a rendezvous mission, and (iii) how information from a rendezvous mission could be used, along with that from ground observations and data from the literature to provide input for a new risk analysis capability that is emerging from ATAPs research. It is concluded that this approach would result in the creation of an appraisal of the threat from 2017 PDC with the least uncertainty possible, herein called the best-case

Using Information from Rendezvous Missions For Best-Case Appraisals of Impact Damage to Planet Earth Caused By Natural Objects

The Asteroid Threat Assessment Project (ATAP), a part of NASAs Planetary Defense Coordination Office (PDCO) has the responsibility to appraise the range of surface damage by potential asteroid impacts on land or water. If a threat is realized, the project will provide appraisals to officials empowered to make decisions on potential mitigation actions. This paper describes a scenario for assessment of surface damage when characterization of an asteroid had been accomplished by a rendezvous mission that would be conducted by the international planetary defense community. It is shown that the combination of data from ground and in-situ measurements on an asteroid provides knowledge that can be used to pin-point its impact location and predict the level of devastation it would cause. The hypothetical asteroid 2017 PDC with a size of 160 to 290 m in diameter to be discussed at the PDC 2017 meeting is used as an example. In order of importance for appraising potential damage, information required is: (1) where will the surface impact occur? (2) What is the mass, shape and size of the asteroid and what is its entry state (speed and entry angle) at the 100 km atmospheric pierce point? And (3) is the asteroid a monolith or a rubble pile? If it is a rubble pile, what is its sub and interior structure? Item (1) is of first order importance to determine levels of devastation (loss of life and infrastructure damage) because it varies strongly on the impact location. Items (2) and (3) are used as input for ATAPs simulations to define the level of surface hazards: winds, overpressure, thermal exposure; all created by the deposition of energy during the objects atmospheric flight, and/or cratering. Topics presented in this paper include: (i) The devastation predicted by 2017 PDCs impact based on initial observations using ATAPs risk assessment capability, (ii) How information corresponding to items (1) to (3) could be obtained from a rendezvous mission, and (iii) How information from a rendezvous mission could be used, along with that from ground observations and data from the literature, could provide input for an new risk analysis capability that is emerging from ATAPs research. It is concluded that this approach would result in appraisal with the least uncertainty possible (herein called the best-case) using simulation capabilities that are currently available or will be in the future

Wheel-regolith interactions on small-body surfaces

We conduct experiments using a single-wheel testbed and simulations using the Soft-Sphere Discrete Element Method to study wheel-regolith interactions on small-body surfaces. We analyze wheel sinkage and traction on different surface materials and we discuss the influence that lowgravity has on rover maneuverability

MASCOT’s in situ analysis of asteroid Ryugu in the context of regolith samples and remote sensing data returned by Hayabusa2

The Hayabusa2 mission provided a unique data set of asteroid Ryugu that covers a wide range of spatial scale from the orbiter remote sensing instruments to the returned samples. The MASCOT lander that was delivered onto the surface of Ryugu aimed to provide context for these data sets by producing in situ data collected by a camera (MasCam), a radiometer (MARA), a magnetometer (MasMag) and a spectrometer (MicrOmega). In this work, we evaluate the success of MASCOT as an integrated lander to bridge the gap between orbiter and returned sample analysis. We find that MASCOT’s measurements and derivatives thereof, including the rock morphology, colour in the visible wavelengths, possible meteorite analogue, density, and porosity of the rock at the landing site are in good agreement with those of the orbiter and the returned samples. However, it also provides information on the spatial scale (sub-millimetres to centimetres) at which some physical properties such as the thermal inertia and reflectance undergo scale-dependent changes. Some of the in situ observations such as the presence of clast/inclusions in rocks and the absence of fine particles at the landing site was uniquely identified by MASCOT. Thus, we conclude that the delivery of an in situ instrument like MASCOT provides a valuable data set that complements and provides context for remote sensing and returned sample analyses

The ESA Hera mission to the binary asteroid (65803) Didymos: Planetary defense and science

The Hera mission is in development for launch in 2024 within the ESA Space Safety Program. Hera will contribute to the first deflection test of an asteroid, in the framework of the international NASA and ESA-supported Asteroid Impact and Deflection Assessment (AIDA) collaboration. Hera will also offer a great science return

The ESA Hera Mission: Investigating binary asteroid (65803) Didymos and the DART crater

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

ORIGO: A mission concept to challenge planetesimal formation theories

Comets are generally considered among the most pristine objects in our Solar System. There have thus been significant efforts to understand these bodies. During the past decades, we have seen significant progress in our theoretical understanding of planetesimal/cometesimals (the precursors of comets) formation. Recent space missions—such as ESA’s Rosetta mission to comet 67P/Churyumov-Gerasimenko—have provided observations claimed by proponents of different comet formation theories to validate their scenarios. Yet, no single formation paradigm could be definitively proven. Given the importance of understanding how the first bodies in our Solar System formed, we propose a dedicated mission to address this issue. ORIGO will deliver a lander to the surface of a cometary nucleus where it will characterise the first five m of the subsurface. With remote sensing instruments and the deployment of payload into a borehole, we will be able to study the physico-chemical structure of ancient, unmodified material. The mission has been designed to fit into the ESA M-class mission budget

Small Spacecraft in Small Solar System Body Applications

In the wake of the successful Philae landing on comet 67P/Churyumov-Gerasimenko and the launch of the first Mobile Asteroid Surface Scout, MASCOT, aboard the Hayabusa2 space probe to asteroid (162173) Ryugu, small spacecraft in applications related to small solar system bodies have become a topic of increasing interest. Their unique combination of efficient capabilities, resource-friendly design and inherent robustness makes them attractive as a mission element at the frontiers of exploration of the solar system by larger spacecraft as well as stand-alone low-cost approaches to open up the solar system for a broader range of interests. The operators' requirements for cutting-edge missions compatible with available launch capabilities impose significant constraints in resources, timelines, timeliness, mass and size. To create spacecraft feasible within these constraints, the mission design teams need to accept a broad range of equipment maturity levels from fresh concepts to off-the-shelf units. The resulting Constraints-Driven Engineering (CDE) environment has led to new methods which transcend traditional evenly-paced and sequential development. We evolved and extended Concurrent Design and Engineering (CD/CE) methods originally incepted for initial studies into Concurrent Assembly, Integration and Verification (CAIV). It is applied in all phases in most of our projects to achieve convergence of asynchronous subsystem maturity timelines and to match parallel tracks of integration and test campaigns. When facing such a challenge, Model-Based Systems Engineering (MBSE) supports design trades and constant configuration evolution due to unforeseen changes. Proactive change and schedule acceleration has resulted from system-level CD/CE optimization across interface boundaries by MBSE-aided CAIV