Deutsches Zentrum für Luft- und Raumfahrt e.V. German Aerospace Centre Institute of Planetary Research SECTION: “ASTEROIDS AND COMETS” Annual Report 2004 Comets ASTEROIDS SPACE MISSIONS MODELS http://solarsystem.dlr.de/KK From left to right Prof. U. Motschmann [email protected] Guest scientist Dr. Jörg Knollenberg [email protected] Scientific staff member Dr. Ekkehard Kührt [email protected] Section leader Dr. Alan W. Harris [email protected] Deputy section leader Dr. Gerhard Hahn [email protected] Scientific staff member Dr. Stefano Mottola [email protected] Scientific staff member Egon Braatz [email protected] Technical staff member Michael Müller [email protected] PhD student Not appearing in the photo: Dr. Carmen Tornow [email protected] Scientific staff member Detlef de Niem [email protected] Scientific staff member Ralph Kahle [email protected] PhD student (finished his work) 2 1. Introduction (EK) 2. Asteroid science 2.1 Investigations of the physical properties of near-Earth asteroids with data from the NASA Infrared Telescope Facility (A. Harris, M. Müller) 2.2 Remote Observing with the IRTF from Berlin (M. Müller, A. Harris) 2.3 Asteroid thermal modelling (M. Müller, A. Harris, M. Delbo, E. Kührt) 2.4 Scientific requirements for near-Earth asteroid hazard mitigation (A. Harris) 2.5 Asteroid search/follow-up programmes and databases (G. Hahn) 2.6 Photometric Survey of Binary Near-Earth Asteroids (G. Hahn, S. Mottola) 2.7 Modelling the solar wind interaction with magnetized asteroids by a quasi-neutral hybrid model (U. Motschmann et al.) 3. Comet science 3.1 Activity of C-G (E. Kührt) 3.2 Pre-cometary ice composition from hot core chemistry (C. Tornow, E. Kührt, U. Motschmann) 4. Impact phenomena and Earth protection 4.1 Hypervelocity impacts on Earth and Mars (D. de Niem) 4.2 Impact-generated vapour and condensate chemistry (D. de Niem) 4.3 On the feasibility of deflecting hazardous asteroids (R. Kahle, E. Kührt, G. Hahn) 5. Contribution to space missions 5.1 Rosetta-Mupus (J.Knollenberg, E. Kührt, T. Spohn) 5.2 Rosetta-Rolis (S. Mottola, H. Michaelis) 5.3 Sofia (C. Tornow, E. Kührt, U. Motschmann) 5.4 DAWN (S. Mottola, R. Jaumann) 5.5 Don Quijote: Study of a hazardous asteroid mitigation pre-cursor mission (A. Harris) 5.6 Deep Impact simulations (D. de Niem, E. Kührt, J. Knollenberg) 5.7 Global 3d hybrid simulation study of the Martian plasma boundaries (A. Bößwetter, T. Bagdonat, U. Motschmann, E. Kührt) 6. Scientific prospects 6.1 Access to Calar Alto telescope (S. Mottola, E. Kührt, A. Harris, G. Hahn) 6.2 National spaceguard centre (G. Hahn, A. Harris, S. Mottola, E. Kührt) 6.3 ISSI project (E. Kührt, M. Müller, M. Delbo, A. Harris) 7. Technology Projects 7.1 AWFS/FIREWATCH (E. Kührt, J. Knollenberg, T. Behnke, V. Mertens) 7.2 HP3 (J. Knollenberg, R. Nadalini) 8. Appendix 8.1 Scientific Publications in refereed journals and books (submitted or published in 2004) 8.2 Scientific publications in other journals and proceedings (published in 2004) 8.3 Publications in the popular literature and public outreach 8.4 Space mission responsibilities 8.5 Observing Campaigns 2004 8.6 Other events and activities 8.7 Funding 3 1. Introduction (E. Kührt) The Section “Asteroids and Comets” was established in the Institute of Planetary Research of the DLR (German Aerospace Centre) in January 1997. At the end of 2004 the staff numbered 7 scientists, one technical employee, 2 PhD students, a secretary, and one guest scientists from the Technical University of Braunschweig. This report describes the results of our research and other activities in 2004. Our scientific goal is to investigate small bodies by observing them in the visible, infrared, and other wavelength ranges, contributing to relevant space missions and modelling physical processes associated with this class of object. Other fields of interest are risk evaluation of impacts of Near Earth Objects (NEOs) on our home planet, the origin of life and the transfer of space technology to solve environmental problems on Earth. Comets and asteroids are thought to be remnant material from the processes of formation and initial development of planets and, therefore, a source of information on conditions in the early Solar System. Many scientists believe that comets and asteroids have significantly influenced the evolution of the terrestrial planets and life on Earth. In particular, public interest in near-Earth asteroids has risen dramatically in recent years as a result of the recognition that such objects occasionally collide with the Earth with potentially catastrophic consequences. Activities in this field are a part of our DLR-project “Comets and asteroids”. They are summarized in Sections 2, 3, and 4. In March 2004 the European Rosetta spacecraft was launched. It should arrive at comet Churyumov- Gerasimenko in 2014 and provide us with a great deal of new information about comets. Our team is involved in numerous experiments on this ESA cornerstone mission. Contributions to Rosetta and several other space missions are described in Section 5. Some new research projects were started in 2004 that are introduced in Section 6. Technology transfer projects are discussed in Section 7. The Appendix summarises publications, project contributions, observation campaigns, public outreach activities, and our funding. 2. Asteroid Science 2.1 Investigations of the physical properties of near-Earth asteroids with data from the NASA Infrared Telescope Facility (A. Harris, M. Müller) The main goal of our observing program with the IRTF is to study the physical properties of the diverse members of the near-Earth asteroid population. Near-Earth asteroids (NEAs) are important not only from the point of view of the risk of catastrophic impacts on the Earth, for which measurements of their sizes and albedos are needed, but also because of their close relation to asteroids in the main belt and the information on the dynamical and physical structure of the main belt that they bring to us. Near-Earth asteroids make close approaches to the Earth and are therefore more accessible to both astronomical observers and rendezvous missions than main-belt asteroids. Our program was awarded a total of 5.5 nights of observing time with the NASA IRTF in the 2004 observing schedule. This time was spread throughout the year as 11 half-nights. We observed a total of 5 NEAs, including (4179) Toutatis, a potentially hazardous object that currently makes close approaches to the Earth every 4 years. On 29 September 2004 Toutatis, which has a diameter of about 4 km, came within only 1.5 million km of the Earth or 4 times the lunar distance. Spectrophotometric thermal-IR observations made on several dates in September are still being analysed and promise to provide a detailed picture of the object’s thermal properties and surface structure. A clearer knowledge of thermal properties, such as thermal inertia and conductivity, is vital 4 to improve calculations of the gradual drift in the orbit of a small asteroid such as Toutatis due to the reactive force resulting from the asymmetric emission of thermal photons (the “Yarkovsky effect”). Attempts have been made by colleagues in the USA to measure this drift in a few cases, including Toutatis, using radar techniques. The combination of radar and thermal-IR observations of small NEAs will provide us with a much clearer understanding of the importance of the Yarkovsky effect and the role it plays in delivering collisional fragments in the main belt into orbital resonances with Jupiter and thus into near-Earth orbits. Precise calculations of the orbital evolution of potentially hazardous asteroids also depend on the Yarkovsky effect and thus on the thermal properties of these objects. Another focus of our observational program in 2004 was the NEA (25143) Itokawa, the target of the Japanese Hayabusa rendezvous mission. A major goal of Hayabusa, which is due to rendezvous with Itokawa in the summer of 2005, is to return to Earth a sample of the asteroid’s surface material. Infrared observations and thermal modelling have revealed that the thermal inertia of Itokawa is some 7 times the lunar value, indicating that in terms of its physical properties, Itokawa’s surface is somewhere between the thermally insulating, debris-strewn, dusty surface of the Moon and bare rock. While a pure rocky surface can be ruled out, it is possible that some regions of Itokawa’s surface are relatively debris-free. Knowledge of the thermal properties of Fig. 2.1. Artist’s impression of asteroid surfaces is important for the planning of lander Hayabusa near its rendezvous missions, from the point of view of their movement over the target Itokawa. surface and interaction with it, and the day/night temperature cycling they are subjected to. 2.2 Remote Observing with the IRTF from Berlin (M. Müller, A. Harris) About half of the aforementioned IRTF observations were performed remotely from Berlin (cf. “Highlight of the week” 245, http://solarsystem.dlr.de/HofW/nr/245/ ). Remote observing has recently been promoted to a fully supported observing mode at the IRTF. In 2004, we set up and tested all the required tools for the network connection; remote observing from Berlin is now a routine means of data acquisition. For the thermal-IR work described in Section 2.1 two instruments were used: the Mid-Infrared Spectrometer and Imager, MIRSI, for thermal-infrared observations, and an optical CCD, Apogee, for simultaneous lightcurve observations. Both instruments can be controlled remotely over the internet. The instrument software runs locally at the IRTF, but the screen output and input from mouse and keyboard can be transferred to/from any computer. For this purpose the VNC protocol is used, which is encrypted and password-protected.