Annual Report 2003

Deutsches Zentrum für Luft- und Raumfahrt e.V. German Aerospace Center

Institute of Planetary Research

SECTION: “PHYSICS OF SMALL BODIES AND

EXTRA-SOLAR PLANETS”

Annual Report 2003

OBSERVATIONS MODELLIN G

FIREWATCH TECHNOLOGY

SPACE MISSIONS

http://solarsystem.dlr.de/KK

From left to right:

First row: Detlef de Niem [email protected] Scientific staff member Dr. Alan W. Harris [email protected] Deputy section leader Dr. Anders Erikson1 [email protected] Scientific staff member Dr. Carmen Tornow [email protected] Scientific staff member

Second row: Holger Voss1 [email protected] PhD student Dr. Gerhard Hahn [email protected] Scientific staff member Prof. U. Motschmann [email protected] Guest scientist Dr. Heike Rauer1 [email protected] Group leader Dr. Ekkehard Kührt [email protected] Section leader Dr. Jörg Knollenberg [email protected] Scientific staff member Rosemarie Mooseder Secretary (retired) Michael Müller [email protected] PhD student Martin Prescher Guest student Egon Braatz [email protected] Technical staff member

Not appearing in the photo: Dr. Stefano Mottola [email protected] Scientific staff member Ralph Kahle [email protected] PhD student Michael Weiler 1 [email protected] PhD student Stephanie Werner [email protected] PhD student

1 Group: Extrasolar planets and cometary atmospheres

Contents

Contents...... 2 1. Introduction (E. Kührt)...... 3 2. Asteroid science...... 4 2.1 Keck thermal-infrared observations of near-Earth asteroids (A. W. Harris)...... 4 2.2 Investigations of the physical properties of near-Earth asteroids with data from the NASA Infrared Telescope Facility (A. W. Harris, M. Müller) ...... 5 2.3 Asteroid thermal modelling (A. W. Harris, M. Müller) ...... 6 2.4 Asteroid search programmes and Databases (G. Hahn)...... 7 ODAS – OCA-DLR Asteroid Survey ...... 7 UDAS – Uppsala-DLR Asteroid Survey...... 7 ADAS – Asiago-DLR Asteroid survey ...... 7 Databases ...... 7 3. Cometary Science ...... 8 3.1 Modelling activity of Hale-Bopp (E. Kührt, O. Groussin, J. Knollenberg)...... 8 3.2 Percolation in cometary nuclei (O. Groussin, E. Kührt, J. Knollenberg)...... 8 3.3 The gas and dust environment of comets (J. Knollenberg) ...... 10 3.4 Plasma environment of comet Churyumov-Gerasimenko (T. Bagdonat1, U. Motschmann 1, E. Kührt, 1 Technische Universität Braunschweig)...... 11 4. Impact phenomena and Earth protection ...... 12 4.1 Hypervelocity impacts of comets and asteroids (D. de Niem, U. Motschmann) ...... 12 4.2 Deep Impact simulations (D. de Niem, J. Knollenberg, E. Kührt)...... 13 4.3 Mission analysis for in-situ exploration and deflection of hazardous asteroids and ...... 13 comets (R. Kahle, G. Hahn, Kührt)...... 13 5. Extrasolar Planets ...... 14 5.1 Radio emission from magnetospheres of extrasolar planets (J.-M. Grießmeier 1, U. Motschmann 1, E. Kührt , 1 Technische Universität Braunschweig) ...... 14 6. Investigation of Mars...... 15 6.1 Modelling of the solar wind - Mars interaction (A. Bößwetter 1, T. Bagdonat 1, U. Motschmann 1, E. Kührt, 1 Technische Universität Braunschweig)...... 15 6.2 Chronostratigraphy on Mars (S. Werner, G. Neukum1, B.A. Ivanov1, A.T. Basilevsky 1, S. van Gasselt 1, FU Berlin)...... 16 7. Scientific prospects...... 17 7.1 New access to telescopes ...... 17 7.2 SOFIA science (C. Tornow, H.-W. Hübers)...... 18 7.3 Origin of life on Earth (C. Tornow, E. Kührt, U. Motschmann)...... 19 8. Space missions...... 22 8.1 Rosetta ...... 22 8.2 Earthguard-I - Phase-A study for ESA (S. Mottola, A. W. Harris, E. Kührt, D. de Niem, G. Hahn) ...... 23 8.3 DAWN (S. Mottola, R. Jaumann, H. Michaelis, E. Kührt) ...... 23 8.4 Bepi Colombo ...... 24 9. Technology Projects ...... 25 9.1 AWFS/FIREWATCH (E. Kührt, J. Knollenberg, V. Mertens, T. Behnke)...... 25 9.2 Airborne FIREWATCH AFW (E. Kührt, J. Knollenberg) ...... 25 Appendix ...... 26

1. Introduction (E. Kührt)

The Section “Physics of Small Bodies and Extrasolar Planets“ was established in the Institute of Planetary Research of the DLR (German Aerospace Center) in January 1997. Its scientific work focuses on investigations of comets, asteroids, and extrasolar planets. At the end of 2003 the staff numbers 9 scientists, one technical employee, 4 PhD students, a secretary, and two guest scientists from the Technical University of Braunschweig and from LAS, Marseille, respectively. This report describes the results of our research and other activities in 2003.

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 small bodies on our home planet, participation in the SOFIA project, the origin of life and the transfer of space technology to solve environmental problems on Earth.

In 2003 a group was formed in our section to concentrate on extrasolar planets and atmospheres of comets. This group, headed by H. Rauer, will release a separate report.

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”.

In 2004 the European Rosetta spacecraft will be 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.

Some new research projects were started in 2003. Sections 7 describes activities to get access to further telescopes, some ideas for possible contributions to the SOFIA project and to one of the DLR basic research fields “Water and origins of life in space”.

The Appendix summarises publications, project contributions, observation campaigns, public outreach activities, and our funding.

Berlin, February 2004

2. Asteroid science

2.1 Keck thermal-infrared observations of near-Earth asteroids (A. W. Harris)

The completion of a programme of thermal-infrared observations of near-Earth asteroids (NEAs) with the 10-m Keck 1 telescope was marked by the publication of the results in the journal Icarus in November. This work was carried out in collaboration with M. Delbo (Univ. Turin, formerly a doctoral student at DLR, Berlin), R. P. Binzel (MIT), P. Pravec (Astronomical Inst., Ondrejov) and J. K. Davies (ATC, Edinburgh). The paper presents the albedos and diameters of 20 NEAs, derived by fitting thermal-model emission continua to the measured thermal-infrared fluxes in the wavelength range 4.8 – 20 microns. Our results have increased the number of NEAs having measured albedos by 35%. Two major conclusions of the work are: • the albedos of S-type NEAs appear to increase with decreasing size • high thermal-inertia, regolith-free objects may be uncommon, even amongst NEAs with diameters of less than 1 km.

The apparent trend to higher albedos with decreasing size in the case of S-type asteroids (Fig. 2.1) may reflect the lack of space weathering of small, young collision fragments. Space weathering is a gradual darkening of asteroid surfaces probably caused by the condensation on dust grains of iron vapour released from surface minerals by the action of the solar wind and micrometeorite bombardment. Our results suggest that many near-Earth asteroids with diameters less than a few km have undergone relatively little space weathering. This implies that these objects, which are presumably fragments from collisions between main-belt asteroids, have made their way into Earth-crossing orbits on time scales shorter than those associated with space weathering (i.e. several millions of years). If further data confirm a trend to higher albedos with decreasing size, our results may help to constrain the dynamical time scales on which small main-belt collision fragments migrate into Earth-crossing orbits.

Fig. 2.1: Plots of geometric albedo versus diameter and solar phase angle for near-Earth asteroids, including those observed in our programme with the Keck telescope. In the left-hand frame all the Keck albedo data, together with 7 values from the literature, are plotted. In the centre frame only the albedos of the S-type NEAs are plotted. The right-hand frame tests the possibility that the trend of increasing albedo with decreasing size suggested in the centre plot is due to phase-angle-dependent modelling errors. The lack of a correlation of albedo with phase angle implies that this is not the case. The linear correlation coefficients of the three plots are –0.38, -0.79, and –0.1, respectively.

A somewhat unexpected finding of our programme of thermal observations of NEAs is that the observed fluxes can be explained in terms of low thermal inertia in most cases. With a few exceptions, models assuming high thermal inertia do not provide good results. This implies that in general even small asteroids have dusty insulating regoliths, in contrast to expectations

that small asteroids with low gravities would not be able to retain collisional debris. With the Keck data we have been able to show that the low apparent colour temperatures observed in several cases are probably due to unusual surface structure and/or shape effects, rather than high thermal inertia.

Direct measurements of near-Earth asteroid albedos are of crucial importance to the assessment of the terrestrial impact hazard. Nearly all estimates of the diameters of NEAs are based on estimates of their absolute brightnesses and an assumed “typical” albedo. Our Keck observations confirm that near-Earth asteroid albedos range from a few percent to more than 50%, implying that such diameter estimates can be in error by up to a factor of 2. The results of our observations have enabled a more accurate determination of the size-frequency distribution of near-Earth asteroids and the associated impact risk to the Earth to be made. S. Stuart at MIT, working with R. Binzel,

Fig. 2.2 The Clearwater Lakes doublet crater system in Quebec, Canada. The crater diameters are 32 km (left) and 22 km. They were formed 290 million years ago, probably by a binary asteroid. Craters this large are formed by impactors with diameters of 1 km or more. Our Keck observations indicate that NEA surfaces are somewhat lighter than previously assumed. This leads to a reduction in the total number of objects in a given size range in the NEA population estimated from absolute brightnesses, as measured by survey programmes such as LINEAR, and a corresponding reduction in impact rate. (NASA/LPI).

has re-calculated the terrestrial collision probability on the basis of the albedo data derived from our Keck programme and the discovery statistics of the NEA search programme LINEAR. He calculates that the total number of NEAs with diameters of 1 km or more is 1090 ± 180. The corresponding rate of collisions with the Earth is one per 600,000 years (see Fig. 2.2 for an example). Events similar in magnitude to that which destroyed more than 2000 square km of forest in the Tunguska region of Siberia in 1908 should occur every 2000 – 3000 years.

The results of our Keck programme (Delbo et al., 2003) were the subject of a DLR Press Release (37/2003) on 18. September and were featured in Nature News and Views in the November issue (Nature, 2003, 426, p. 242).

2.2 Investigations of the physical properties of near-Earth asteroids with data from the NASA Infrared Telescope Facility (A. W. Harris, M. Müller)

Thermal-infrared data obtained with the NASA IRTF (Fig. 2.3), PI: A. W. Harris, together with data from the Keck programme outlined above, show that the apparent colour temperatures of NEAs decrease more rapidly with increasing solar phase angle than would be expected on the basis of simple thermal models that ignore shape effects and surface irregularities. In particular, two binary asteroids, which are thought to consist of rubble piles, show relatively low colour temperatures at phase angles of around 60°. Rubble piles may have unusually rough or irregular surfaces that could lead to a high degree of beaming of thermal radiation in the sunward direction and correspondingly less radiation being observed at high phase angles. Since virtually nothing is known about the physical nature of rubble piles, such observations are a potentially valuable source of information on their surface properties.

The IRTF, while not as sensitive as the much larger Keck telescopes, allows us to observe selected asteroids over longer time intervals and ranges of phase angle. Studying the variation in the intensity and wavelength distribution of the thermal flux with phase angle provides insight into the thermal properties and surface characteristics of near- Earth asteroids. The NASA IRTF time allocation committee has awarded a total of 6 half-nights to this programme for 2004.

Progress in our observational work on near- Earth asteroids was presented at the 35th Meeting of the American Astronomical Society Fig. 2.3 The NASA Infrared Telescope Facility on Division for Planetary Sciences in Monterey, 1 – Mauna Kea, Hawaii, with the island of Maui in the 6 September (Harris et al., 2003; Müller et al., background. The IRTF primary mirror has a diameter of 3 m. The altitude of the summit of Mauna Kea is 4200 2003). m. (NASA/IRTF).

2.3 Asteroid thermal modelling (A. W. Harris, M. Müller)

Theoretical modelling of the thermal emission of asteroids is crucial for the interpretation of observational data. We are investigating the effects of shape, surface structure, rotation and thermal inertia on the observed thermal emission from asteroids as a function of solar phase angle. Our goal is to develop computer routines that will allow the observable thermal-infrared emission to be calculated for a given object with arbitrary viewing geometry. The surface of an asteroid is treated as a 3-dimensional arrangement of triangular facets. The solar energy incident on a facet is calculated taking into account the heliocentric distance, angle of inclination and shadowing effects, which depend on the shape of the object and the facet’s location with respect to neighbouring surface structure (e. g. craters). The temperature of the facet is then calculated on the basis of assumed values of albedo and thermal inertia. The total observable thermal emission is calculated by summing the contributions from each facet visible to the observer. Model parameters can be adjusted until good agreement is obtained with observational data, thereby constraining the physical properties of target asteroids. An example of our simulations is given in Fig. 2.4.

The thermal-infrared work described above is partly supported by a grant from the German Research Foundation (DFG).

Fig. 2.4 Thermal model of the near-Earth asteroid 1580 Betulia. Warmer sun-facing facets are coloured red. The model is based on a realistic shape derived from optical lightcurve observations (courtesy M. Kaasalainen) but does not include the effects of thermal inertia. The thermal-IR emission an observer would detect for a given set of astrometric and physical parameters can be synthesized with such models and compared with actual observational data. The most probable thermal parameters of the asteroid can be derived iteratively by finding the model parameters that give the best fit to the observational data.

2.4 Asteroid search programmes and Databases (G. Hahn)

ODAS – OCA-DLR Asteroid Survey Although the observing programme at the Schmidt telescope of the OCA at Calern was cancelled in 1999, the database of astrometric observations (more than 44000 were obtained) is still maintained. These observations are continuously checked at the Minor Planet Center, and used for orbit determination and/or improvements. By the end of 2003 more than 37000 of these observations had been linked to known asteroids or comets. The survey resulted in 951 orbits of new discovered asteroids, of which currently 496 are numbered. Further details are available at http://earn.dlr.de/odas/ .

UDAS – Uppsala-DLR Asteroid Survey Observations at the Kvistaberg Station have continued, resulting in 9980 astrometric observations of asteroids and comets. Details and current observing statistics can be found at http://earn.dlr.de/udas/ .

ADAS – Asiago-DLR Asteroid survey 807 astrometric positions of asteroids and comets were obtained during February - April of 2003. Maintenance work at the telescope and the camera system during most of the year prevented further observations. Details can be found at http://dipastro.pd.astro.it/planets/adas/.

Databases Physical properties and discovery circumstances of NEOs are available at http://earn.dlr.de/nea/ . A constantly updated database of all known NEOs (as announced and published by the Minor Planet Center - MPC) is maintained, providing a “home-page” for each asteroid. These pages contain the discovery circumstances, and all published data on the physical properties, including references. It also contains an update to the table of physical properties of NEOs published in the Asteroids III book (Binzel et al., 2002, W. Bottke et al. eds., Univ. of Arizona Press, Tucson. pp. 255 - 271).

3. Cometary science

3.1 Modelling activity of Hale-Bopp (E. Kührt, O. Groussin, J. Knollenberg)

The outstanding brightness of comet Hale-Bopp enabled observers to measure production rates of several volatiles over a wide range of heliocentric distances and to establish an exceptional database for the analysis of cometary activity and physical properties (e.g. Bockelée-Morvan and Rickman 1999). Only water molecules probably come directly from the surface. The production rates of this species offer the simplest way to obtain information about the nucleus.

The analysis of extremely volatile species like CO is more complex. It is not completely understood where they are released. Several authors (Benkhoff, 1999; Enzian, 1999; De Sanctis, 1999) argue that they are released deeply below the surface and in extended sources. However, their model results don’t fit the measurements.

We developed a new thermal model to calculate production rates. The influence of heat conduction and the strong obliquity of the rotation axis, which causes pronounced seasons, are taken into account. The gas activity has been calculated as a function of heliocentric distance by an integration of the local flux over the entire surface of the comet, and compared with experimental data published by different groups. Because comets are porous bodies sublimation is allowed in the entire volume. Furthermore, we assume that all CO molecule

coming from the sublimation front reach the surface and escape the nucleus. Results are given in figs. 3.1 – 3.3, where the solid and dotted lines correspond to a thermal conductivity of 0.001 W/K/m and 1 W/K/m, respectively.

Fig. 3.1 The measured and calculated H2O Fig. 3.2 Calculated CO production rate (mol/s) is production rates (mol/s) are shown as a compared with experimental data. As for H O, the 2 function of heliocentric distance (AU). Active low conductivity curve (solid line) fits the areas statistically distributed over the nucleus observations better than the high conductivity are assumed. curve (dotted line).

Fig. 3.1 shows that a thermal conductivity of

0.001 W/K/m fits the observational H2O-data well but higher values do not. This result is in agreement with previous calculations performed by Kührt (2002) and Groussin et al. (2004). The best curve was achieved with an active surface area of about 2500 km2, which corresponds to an active fraction of 16%, assuming a radius of 35 km. The CO sublimation rates shown in Fig. 3.2 fit the post-perihelion data well, but pre-perihelion Fig. 3.3 Depth of the CO sublimation front (in m) some small discrepancies remain. As for H O, as a function of heliocentric distance (AU). 2 the low conductivity curve fits the observations better than the high conductivity curve). This is a preliminary result and we expect to ameliorate the fit soon by changing the parameters (density, conductivity). It can be found that CO-sources over an active area of about 1200 km2 well describe the observations. This corresponds to an active fraction of about 8% for a nucleus with a radius of 35 km. The depth of the CO sublimation front (Fig. 3.3) strongly varies with the heliocentric distance and depends on the density of H2O and CO. For a low conductivity the CO front almost reaches the surface at perihelion, while for a high conductivity the CO front remains in deeper layers and, therefore, the production curve is flat.

3.2 Percolation in cometary nuclei (O. Groussin, E. Kührt, J. Knollenberg)

The study of gas diffusion through porous media is essential to understand the activity of cometary nuclei, in particular the activity of highly volatile molecules that may come from deep layers. Usually, authors solve the gas and heat diffusion equations to determine the net production rates. As a first approximation, this method is satisfactory, but it suffers from a number of unknown parameters, such as pore size, thermal conductivity and tortuosity. Moreover, it assumes that a gas molecule can always find a path from the location where it is produced to the surface of the nucleus, even if it is produced in deep layers. This point has never been checked before in the literature and is the subject of this study. Percolation theory is very well adapted to tackle this problem, as it deals with the connection between pores in

Fig. 3.4 Two basic models are illustrated. Each plot is a slice of a 200x200x200 cubic lattice. On the left, each cell of the lattice is filled (white) are empty (black), randomly, with a given probability. In this case, this probability to be empty, which obviously corresponds to the porosity of the lattice, equals 44%. We call this model “model 1”. On the right, the cubic lattice if filled with spherical grains (white) of different radius, assuming a given distribution function. The porosity (44% in this case) is derived from the grain size distribution function. We call this model “model 2”. Models 1 and 2 give very different results even for the same porosity. The free parameters are the porosity for model 1 and, additionally, the grains size distribution function for model 2.

porous media. Percolation theory is used in many branches of physics such as phase transition, polymer science, aggregation, etc. (Stauffer and Aharony, 1994). It was recently applied to comet by Shoshany et al. (2002) to estimate the thermal conductivity of the nucleus as a function of its porosity. In this study, we apply the percolation theory to calculate the percolation probability, characteristic time for gas diffusion, production rates (flux) and tortuosity as a function of porosity. The two models we used are presented in Fig. 3.4 and some results are illustrated by figs. 3.5 and 3.6. For model 1 there is a phase transition for a

porosity pc=0.32±0.01. If p<0.32, no molecules can diffuse through the media and deeper layer are isolated from the surface. If p>0.32, nearly all the molecules produced in deeper layers can find a path through the porous media and escape. For model 1 the theory predicts

pc=0.3116 that is in excellent agreement with our determination and which validates our numerical code. For model 2, where the cubic lattice is filled with spherical grains with a given

size distribution function, the behaviour is identical, but the critical porosity is pc=0.04±0.02. As a consequence, except for extremely low porosity, a gas molecule can always find a path to

reach the surface. For this model theoretical value of pc do not exist.

Fig. 3.6 Tortuosity as a function of porosity for models 1 Fig. 3.5 Probabilty for a gas molecule to diffuse through a and 2. The tortuosity is the ratio of the length of the path porous media as a function of its porosity p for models 1 followed by a gas molecule from the location it is produced and 2. It is usually called the percolation probability. to the surface to the length of the shortest (direct) path. The vertical lines mark the percolation limits. 9

For both models we find that the lower the porosity, the higher is the tortuosity (Fig. 3.6) because the path becomes more complex (less direct) for lower porosity. When we reach the percolation limit, tortuosity becomes larger than 2. A typical value used in the literature (e.g., Enzian 1999) is 13/9. We note that the present calculation of the tortuosity is a lower limit as we always consider the shortest path from the top of the lattice to its bottom, neglecting more complex and longer paths. A better model to estimate the tortuosity is now in progress.

3.3 The gas and dust environment of comets (J. Knollenberg)

In models of the cometary gas and dust coma the dust particles are usually treated as compact spheres, although there is evidence (e.g. from the “Interplanetary Dust Particles” thought to be of cometary origin) that they might have in reality a fluffy and fractal-like aggregate structure. Therefore, the drag forces on fractal particles where studied in some detail and first results were presented in October 2003 at the conference on “The new Rosetta targets” in Capri, Italy. Two different methods were used to create fractal grains. The first was the well- known BPCA (“Ballistic Particle Cluster Aggregation”) model and the second the purely mathematical “Dielectric Breakdown Model”. Although the latter method is not directly related to a relevant physical agglomeration process and, therefore, somehow artificial, it has Fig. 3.7 DBM dust aggregate with fractal dimension D=2.3. the advantage that particles of different fractal dimensions can be generated by simply varying the model input parameters. Figure 3.7 shows an example of a DBM generated dust particle consisting of 1024 monomers and a fractal dimension D=2.3. The drag force on a dust grain is generally proportional to the cross section over mass ratio A/M of the particle and

to the “drag coefficient” CD(Ma, Td/Tg), a shape factor which is further dependent on the flow Mach number Ma and the ratio of dust-to-gas

temperature Td/Tg. The computed A/M ratio exponent E (A/M ~ RadiusE, e.g. for compact spheres E=-1) is depicted in Fig. 3.8. showing clear evidence for a linear relationship between E and D for D > 2.2.

Furthermore, detailed Monte-Carlo simulations on the interaction between a free molecular gas stream and the fractal dust aggregates have Fig. 3.8 Cross section over mass exponent E of dust shown that the drag coefficient is generally only aggregates as function of fractal dimension D. slightly increased by 5-30% compared to the corresponding values for a sphere and that this result is nearly independent of the fractal dimension. These results justify the use of the spherical particle assumption for dust flow modelling, but allow further a simple rescaling of the results to fractal dust models via the derived dependence between E and D.

Together with the conference mentioned above a meeting of the ESA CEMWG (“Comet Environment Modelling Working Group”) was also held, which was attended by one group member (J. Knollenberg). At this meeting, some concern was expressed about the dust environment of the new target 67P/Churyumov-Gerasimenko (CG) as a possible threat to the Rosetta mission, because 67P-CG is dustier in terms of the AfRho parameter than the original target comet P/Wirtanen. To support the analysis of ESA, several runs with an existing 2D- axisymmetric model of the inner gas-and dust coma were executed. The main conclusion from these simulations was that the situation for 67P-CG is not much worse than for P/Wirtanen, if one compares the estimated particle flux on the spacecraft and the predicted radiation environment. The results of his modelling effort will be presented at the next CEMWG meeting.

3.3 Plasma environment of comet Churyumov-Gerasimenko (T. Bagdonat1, U. Motschmann 1, E. Kührt, 1 Technische Universität Braunschweig)

Comet Churyumov-Gerasimenko (C-G) was chosen as the new target of the ROSETTA mission which will be launched in February 2004. Although C-G is estimated to be about four times larger in diameter compared to the old target Wirtanen, recent ground-based observations indicate a similar water production rate for both comets. Because water is the dominant source for ion production through solar UV radiation, both comets are very similar from a plasma physical point of view.

We adapted our previous model for Wirtanen to C-G toperform numerical simulations of the plasma environment at C-G for different heliocentric distances. For this purpose we use a fully three-dimensional hybrid code, which describes the ions as individual particles, whereas the electrons are modelled as a fluid. As advancement to our earlier model we included ion- neutral gas collisions and two different electron temperatures for the solar wind electrons and the “cometary electrons”, which are significantly colder.

Figs. 3.9 and 3.10 show two different views of an exemplary 3D result for C-G at a heliocentric distance of

Fig. 3.9 Isosurface of the cometary 3.25 AU. An isosurface of the cometary ion density, i.e. ion density (red) and magnetic field the plasma tail, along with the magnetic field line lines for C-G at 3.25 AU. configuration are shown. The solar wind flows in the positive x-direction, i.e. from left to right in both figures. The IMF points towards the positive y-direction. The axes are scaled in ion inertia lengths, which are about 250 km for this case. Thus, the simulation box extends about 1000 km in each direction. The production rate of C-G is very low at this heliocentric distance. Consequently, the plasma tail is not directed anti-sunward, but shows the cycloidal form typical for weak comets. The tail is “flat”, i.e. it is much broader in the plane perpendicular to the IMF (Fig. 3.10) than in the parallel plane (Fig.3.9), because the pick-up process only acts perpendicular to the magnetic field. The field lines are draped around the obstacle, as can be seen in Fig. 3.9 and also bent slightly upwards, as Fig. 3.10 shows. After being detached from the tail, the Fig. 3.10 Same as in Fig. 3.9 but for a different viewing angle 11

field lines try to shorten, which excites a circularly polarized Alfvèn in the wake. Some other interesting plasma features (not shown here) have been investigated. At distances beyond 2.5 AU, the plasma environment does not show a shock or a diamagnetic cavity. However, a modified “ion composition boundary” is already developed. This differs strongly from the case of strong comets like Halley. Moreover we investigated the ion dynamics by means of individual particle trajectories as well as energy spectra. The spectra show a pronounced non-thermal behaviour. Therefore a kinetic treatment is mandatory for weak comets. Several interesting plasma physical effects never observed in-situ before could be explored by the ROSETTA spacecraft.

4. Impact phenomena and Earth protection

4.1 Hypervelocity impacts of comets and asteroids (D. de Niem, U. Motschmann)

Current issues for numerical simulation In computational physics, hypervelocity impacts are challenging because of the need to model multi-material hydrodynamic phenomena in the presence of interface instability and over a huge range of Mach numbers, densities, and pressures. A basic goal is to understand the partition of the kinetic energy of the impactor and the consumption of this energy during various stages of crater formation. A parallel effort is to develop a multi-material Godunov method using mixture theory to yield an effective Riemann problem for the bulk material. Recently, simple ordering strategies have been implemented to enable more than two materials to share a computational cell, but this has not yet been generalized to two dimensions. Validation of variants using individual signal-propagation times for the solution of the multi-material Riemann problem to others using an effective one-material treatment have been performed. Further research led to a faster iterative algorithm for the solution of the elementary Riemann problem. Moreover, new strategies dealing with vacuum in parts of the cell have been developed (weighting of interactions between cells with partial vacuum adjacent to the face where the Riemann problem is to be solved). As an example, an impact into ice has been simulated (one material plus vacuum), and with parameters compatible with the upcoming Deep impact mission (Fig. 4.1). An ongoing activity is the transition from a two- dimensional scheme in Cartesian co-ordinates to cylindrical coordinates, to solve realistic two- dimensional axially symmetric impact problems. This has been developed within AUSM- and Godunov-type methods. Generalization of the overshoot-free material transport algorithm to cylindrical coordinates is a recent achievement.

Condensation of impact-generated vapour Direct hydrocode simulations are limited in the number of materials, and coupling condensation kinetics on a cell basis is not feasible because of the stiffness of the problem. Existing investigations are confined to the condensation of major element compounds as an equilibrium process; theoretical models of the condensation of Ni-Fe spherules and platinum- group element abundances are required because these are regarded as the most convincing argument for impact events in earth history. In 2002 a new theory for kinetics of condensation of vapour of transition metals in the early solar system appeared (Tanaka, K. K., Tanaka, H., and Nakazawa, K. 2002, Icarus, Vol. 160, 197), which goes beyond the classical theory of nucleation. However, the model is too simple in an impact situation; it uses simple exponential temperature decrease. We prefer to generalize our own energy equation (de Niem, D. 2002, Geol. Soc. of Am., Spec. Pap. 356) to compute the actual temperature history resulting from the dynamics. A related effort was the collection of relevant thermo-chemical data, which are not yet complete. Preliminary results include the composition of early high-temperature liquid condensates forming in a dense hot vapour originally composed of chondrite-like material. These were presented at the Large Meteorite Impacts conference in 2003.

4.2 Deep Impact simulations (D. de Niem, J. Knollenberg, E. Kührt)

In preparation for a possible collaboration in NASA’s Deep Impact mission, some studies of the interaction of the impact-generated vapour cloud with a cometary atmosphere have been made. An analytical model was developed for the properties of the strong shock wave driven into the coma, based on the Kompaneets approximation. A density distribution is

Fig. 4.1 Model calculation of the density of target Fig. 4.2 Dust column density at t=3 s after the impact for material 3 ms after a 370 kg impactor has hit the a phase angle of 60°. surface of a comet with 10 km s-1. demonstrated in Fig. 4.1. Furthermore, temperature and pressure in the shock wave have been investigated numerically, using a hydrodynamic scheme based on Roe’s Riemann solver for a Van der Waals gas, which is a better approximation for the metastable water vapour prior to condensation.

Using the results from the impact model described above as input data, a 2D-axisymmetric hydrodynamic model of the coupled gas and dust flow in the coma was then used to compute the transient coma features generated by the impact. Fig. 4.2 shows as an example the dust column density at t=3 s after the impact, where a dust shell moving outwards at a speed of about 0.7 km s-1 is clearly visible.

4.3 Mission analysis for in-situ exploration and deflection of hazardous asteroids and comets (R. Kahle, G. Hahn, Kührt)

The presence of craters on the Earth and Moon constitutes undeniable proof that the Earth has often been struck by NEOs in its past.

Furthermore, the currently observed large Athos Rendezvous 17 Oct 2008 + + + + + + + + + Earth Gravity-Assist population of near-Earth asteroids implies that + + + + + + Earth + + 1 Mar 2008 ++ + + + there is a continuing risk of future impacts on 1.5 + + + + the Earth. In order to prevent a predicted -1 Athos+ S/C Mars 0.15 + 0.1 -0.5 + + 0.05 ] terrestrial impact catastrophe, technically + + 0 U Y A

[ [

A 0 -0.05 Z credible mitigation missions have to be U ] Deep Space -0.1 0.5 Maneuver -0.15 identified and designed in a first instance. The Launch from GTO -0.2 -2 1 11 Jan 2008 -1.5 analysis of such missions is the scope of a PhD -1 -0.5 1.5 0 0.5 project being carried out in the Physics of Small ] 1 X [AU Bodies Section in collaboration with the 21.5 Technische Universität Dresden. Fig. 4.3 Trajectory design for an Earth-Gravity- Assist transfer to virtual asteroid Athos.

A model population of virtual collision candidates has been generated based on a de-biased NEO orbit population and statistical statements regarding physical properties. This population shall allow for a close-to-reality simulation of potential Earth impact mitigation scenarios. Orbits are propagated with the aid of the 15th order numerical integrator RADAU. Here, Earth and moon are treated separately and inner and outer planets are included to simulate the influence of pre-impact close encounters. Further, an atmospheric entry routine has been implemented, which simulates braking, ablation and fragmentation of the entry-object. Finally, impact location and impact (or airburst) energy can be estimated. Based on the characteristics of an individual virtual object the velocity change required to deflect its collision path into a grazing encounter (or safe encounter) shall be computed as a function of interception epoch. As an outcome, the total impulse for deflection can be found. This impulse has to be applied by a deflection technique. Here, a promising non-nuclear technology is the solar concentrator, where the basic idea is to concentrate solar radiation onto the NEO surface with a lightweight (parabolic) reflector. Depending on duration and intensity of illumination, the material within the spot will be heated up and vaporizes delivering a low but continuous thrust. When operating such a system over several weeks, even large objects of several hundred meters in diameter could be diverted from their collision path. A feasible concentrator design based on inflatable space structures has been investigated that meets the limited payload capability of current interplanetary launchers. Critical issues to be investigated deal with the condensation of gas and penetration of dust particles. Other mitigation techniques under investigation are kinetic energy impacts, nuclear explosives, and novel mini-magnetospheric plasma propulsion.

If the required impulse for deflection can be generated by a particular deflection technique then mission opportunities have to be identified too. Based on the delta-V requirements of the transfer mission and payload capacity of launch system the maximum available deflection payload mass can be estimated. Transfer trajectory analysis includes rendezvous missions, e.g. for precursor mission (Fig. 4.3), as well as high speed impacting missions, e.g. for kinetic energy interaction. A mission analysis program has been developed, which finds energy- optimal impulsive transfer trajectories to a desired target. Simple elliptical transfers, multiple- encounter transfers, and multi-gravity-assist trajectories are considered. Finally, mission requirements, deflection feasibility and mission opportunities shall be analysed for each individual model object. General (or statistical) statements concerning the feasibility and effort for deflection missions shall be derived.

5. Extrasolar Planets

5.1 Radio emission from magnetospheres of extrasolar planets (J.-M. Grießmeier 1, U. Motschmann 1, E. Kührt , 1 Technische Universität Braunschweig)

Magnetized extrasolar giant planets in close (but not tidally locked) orbits are expected to be strong nonthermal radio emitters. The radiation may be strong enough to be detected from Earth with the next generation of instruments. As most observation techniques radio detection does not simply yield the pure planetary signal, but a combination of the planetary and stellar emission. This is true for observations in all spectral ranges, but the intensity ratio of stellar to planetary emission varies: it is about 109 in the visible range and 106 for infrared emissions. Things are different for the low-frequency radio range: The planetary radio emissions are dominated by powerful nonthermal emission generated by the cyclotron-maser-instability (CMI). The solar radio emission - which is considered as an example for stellar radio emission - consists of a quiet background produced through thermal bremsstrahlung plus a rich spectrum of radio bursts. The difference in generation mechanism leads to a much more favourable intensity ratio. Figure 5.1 shows that the intensity ratio ranges between 10-4 for quiet sun

emissions and 103 for strong radio bursts in the spectral region considered here, thus making it easier to separate the stellar and the planetary radio emission.

Within this project a detailed comparison of the expected stellar and planetary signal is performed for the low-frequency radio range. For the star a stellar twin is assumed, while for the planet Jupiter’s radio emission is Fig. 5.1 Comparison of solar and average planetary flux densities (all flux densities normalized to a distance of 1AU.) taken, keeping in mind that for close-in extrasolar planets much stronger radio emissions are expected when compared to the radio planets of the solar system. The quiet sun emission, which is due to thermal emission of ionized plasma close to the local electron plasma frequency, is much weaker than Jupiter’s emission, and has a different polarisation (i.e. it is randomly polarised). Thus, quiet star emission is not a problem for the detection of radio emission from magnetospheres of extrasolar planets. During solar maximum, noise storms frequently occur (about 10% of the time). The typical duration is between a few hours and several days. The emission consists of a broadband continuum plus short-lived bursts. Noise storms could be a problem for stars much more active than the Sun.

Radio bursts are generated by high-energy particles originating from solar flares or shock fronts. Typically, their frequency drifts. Their flux densities are much higher than that of the quiet sun or of noise storms. As their flux density is much higher than for Jupiter’s emission, radio bursts could be problematic. However, for the sun, radio bursts are either rare (Type IV bursts: 3 per month at solar maximum) or of limited duration (Type III bursts: a few seconds). Also, the additional noise due to the galactic background has to be considered. An additional measurement (slightly off-target) may become necessary to be able to subtract the galactic background from the measured signal. Thus, it seems that for a planet with sufficiently strong radio emission the separation of the planetary signal from the stellar emission is possible.

6. Investigation of Mars

6.1 Modelling of the solar wind - Mars interaction (A. Bößwetter 1, T. Bagdonat 1, U. Motschmann 1, E. Kührt, 1 Technische Universität Braunschweig)

The Phobos-2 mission has detected that Mars does not possess an intrinsic magnetic field. Consequently, the ionosphere of Mars is directly affected by the solar wind. The gyroradii of the solar wind protons are in the range of several hundred kilometres and therefore they are comparable with the characteristic scales of the interaction region. Consequently this interaction of the solar wind with the ionosphere is studied by a three dimensional hybrid model.

Different boundaries emerge from the interaction of the solar wind with the continuously produced ionospheric heavy-ion plasma. These boundaries can be identified as bow shock, ion composition boundary and magnetic pile up boundary. Figs. 6.1 and 6.2 show the simulation results where solar wind density and the heavy ion density are depicted.

Comparing the figures one recognizes that the sharply bounded tail fits exactly into the solar wind plasma wake. Hence, both ion species are completely separated. The corresponding boundary is called ion composition boundary. Fig. 6.2 shows that the heavy ion density becomes asymmetric inside the tail. The heavy ions form rays. Beneath the South pole some cycloidal motion of the large gyroradius can be seen, whereas in the rest of the tail region the stream lines are bundled inside the tail rays. Furthermore, in the northern hemisphere a wave- like structure with rather large amplitude is evolved on the dayside of the ion composition boundary by a Kelvin-Helmholtz instability. This wave strips off heavy ion plasma clouds with high density. Downstream of the bow shock a multiple shocklet structure is to be seen. The simulation results regarding the shape and position of these boundaries are in good agreement with the Phobos-2 and Mars Global Surveyor observations. The positions of these boundaries depend essentially on the ionospheric production rate, the solar wind ram pressure, and the electron temperature of the ionospheric heavy ion plasma.

6.2

Fig. 6.1 Solar wind density in cm-3. The black solid lines Fig. 6.2 Heavy ion density in cm-3 with the stream represent stream lines of the corresponding velocity field. lines of the corresponding velocity field. The heavy On the nightside, a plasma wake is formed, where the ions form a complex tail structure behind the planet. solar wind density vanishes almost completely.

6.2 Chronostratigraphy on Mars (S. Werner, G. Neukum1, B.A. Ivanov1, A.T. Basilevsky1, S. van Gasselt 1, 1 FU Berlin)

The global stratigraphic schemes for Mars are based on the superimposed number of impact craters on planetary surface units and a chronology model by Hartmann and Neukum which have been transferred from Moon to Mars having in mind that there is a single crater- generating family of projectiles. In case of Mars the current best estimate of the Mars/Moon cratering rate ratio is given by Ivanov.

Utopia and Acidalia Planitiae (both Martian lowland plain units) are occupied by extensive areas of polygonal terrain, so-called giant polygons (Fig. 6.3). They consist of 200 to 800 meter wide steep-walled and flat-floored troughs some tens of meters deep and 5 km to 30 km in diameter. A number of hypotheses for the origin were mentioned such as thermal cooling and contraction in permafrost, desiccation of water-saturated sediments, cooling of lava, and tectonic deformation. The giant polygonal pattern is accompanied by ring- or double-ring-like structures which are assumed to be buried craters (ghost craters) and have been used to estimate the thickness of the overburden.

New measurements in selected areas of the Utopia region which cover polygonal terrain and surrounding units were performed. All crater size-frequency distributions (SFD) of the selected units converge in the smaller crater diameter size range and give an age of 3.4 Ga. The diversity or deviation from the expected crater production function for the larger crater diameter size range (larger than 3 km) most likely depends on different target properties or the geologic evolution of that area. A few of these units show an "excess" in the crater SFD of larger craters as has been already observed by McGill and Hills. Crater counts on these units yield an age of 3.8 Ga. The measured distributions converging in the small-size range lead to an age of 3.4 Ga and indicate a resurfacing event at 3.4 Ga ago detectable in all units. The same distribution has been combined with the population of so-called ghost craters, the buried craters which causes the ring- like grabens. The sum of visible and ghost crater populations yield an age of 3.8 Ga as it has been observed in regions with strong excess of craters in the larger diameter range. In the Acidalia Planitia case the results of crater SFD show similar results, but appear less pronounced. The ages yielded for this region are slightly different and reveal a time span from 3.5 to 3.7 Ga, whatever causes the diversity or obscures the expected production function of the crater SFD in Utopia Planitia in the Fig. 6.3 THEMIS image (Mars larger size range occurred between 3.4 and 3.8 Ga. These Odyssey mission) shows an distributions can be explained by extensive resurfacing effects example of a crater in the polygon terrain in Utopia within a time span of roughly half a billion years. This is region and also double-ring consistent with the existence of a proposed ocean in the forming grabens, so-called northern lowlands and with the interpretation that the polygons ghost craters with a resolution formed through desiccation and differential compaction of of about 20 m per pixel. sediment over buried topography.

The future goal is to assess the role of the projectile nature (asteroid vs. comet) and the target properties (water or ice content) in the crater formation process and thus in the morphological appearance and size parameters of craters. Objects that may reflect the volatile content are craters with fluidized ejecta blankets (FEB) varying in their morphology of interiors and some quantitative parameters such as crater depth/diameter, rim height/diameter ratios and additionally the diameter ratios of the crater cavities to their ejecta blankets.

This project runs within the framework of the DFG- Schwerpunktprogramm: Mars and other terrestrial planets.

7. Scientific prospects

7.1 New access to telescopes

Calar Alto: 1.23 m Telescope – commissioning phase (S. Mottola, E. Kührt)

In January 2003 we completed the commissioning phase of the Max Planck Institute 1.23 m telescope on Calar Alto (Fig. 7.1). All the necessary software for the remote control of the telescope has been installed at our Institute

Fig. 7.1 The Calar Alto 1,23 m telescope. 17

and thoroughly tested; computer scripts for the automatic acquisition of images sequences have been written, and test observations have been carried out.

Unfortunately, shortly after the commissioning phase had been completed, a major mechanical failure of the telescope mount has brought the observing program to a halt. A major failure of the telescope cannot be repaired within the scope of the present maintenance contract, and a new agreement with MPI needs to be put in place. In addition, starting from this year, all of the telescopes on Calar Alto will be operated by a new German-Spanish organization, which will require a new negotiation with all involved parties. The first steps in this direction have already been undertaken, and in the course of the present year it should become clear how, and under what conditions the telescope can be fixed and the observing program restored.

Himalaya: 2 m Chandra Telescope HCT (S. Mottola, E. Kührt) We have started cooperation with Indian scientists in the field of observing and modelling comets and asteroids. It is planned to write joint proposals for the Indian Astronomical Observatory (IAO) that is situated at an altitude of 4500 metres above mean sea level in the north of western Himalaya. It is the world’s highest observatory for optical and infrared astronomy. The cloudless sky and low atmospheric water vapour make it one of the best sites in the world for optical, infrared, sub-millimetre, and Fig. 7.2 The 2 m Chandra Telescope in Himalaya. millimetre wavelengths. A 2-m optical-infrared telescope (Chandra Telescope HCT, Fig. 7.2) with 3 science instruments (Himalaya Faint Object Spectrograph, the Near-IR Imager, and the Optical CCD Imager) is installed there and gives us a good opportunity to observe small bodies.

7.2 SOFIA science (C. Tornow, H.-W. Hübers)

SOFIA – the replacement of the Kuiper Airborne Observatory – is a joint project between NASA and the DLR. It will fly on a Boeing 747 (Fig. 7.3) and start to operate in October, 2005. Its telescope is equipped with a 2.7 m parabolic mirror. A number of 1st-light instruments will be capable of measuring the emitted radiation of extraterrestrial targets in the optical, infrared and sub-mm spectral regions. Among other goals SOFIA enables the study of: Fig. 7.3 Sofia aircraft.

• Proto-planetary disks and planet formation in nearby star systems. • Origin and evolution of biogenic atoms, molecules, and solids. • Composition and structure of planetary atmospheres, rings, and comets.

DLR is involved in the development of GREAT (German Receiver for Astronomy at Terahertz Frequencies). Presently, GREAT consists of low-, mid-, and high-frequency bandpasses (LFB, MFB, and HFB) that correspond to

2 2 • C II ion − P3/2 → P1/2 fine-structure ground-state transition at 1.9005 THz – LFB 2 • OH molecule − Π3/2 J = 5/2 → 3/2 rotational ground-state transition at 2.5123 THz – MFB

• HD molecule − J = 1 → 0 rotational ground-state transition at 2.6750 THz – MFB 3 3 • O I atom − P1 → P2 fine-structure ground-state transition at 4.7447 THz – HFB

The flight altitude of SOFIA can be as high as ~ 12 km. Nevertheless, the atmospheric influence is still measurable and needs to be corrected. In addition there is the far-infrared background radiation resulting from the galactic cirrus contribution and zodiacal light.

Starting in 2003 we have been preparing several SOFIA observation proposals: • Hot cores which are produced by forming massive stars should be observed during the first observing cycle, extending from October 2005 to October 2006. We suppose that the rich chemistry is driven by the stellar far UV radiation and its impact on the ice mantle of the grains. Therefore the UV flux will be measured using the GREAT at different distances from the star to map the extension of its radiation field. • Later we will try to observe comets. In Section 7 the similarities in the chemical composition of the gas in the vicinity of hot cores and in the coma of active comets are discussed. However, the occurrence of these comets cannot be planned.

7.3 Origin of life on Earth (C. Tornow, E. Kührt, U. Motschmann)

The origin of life is a basic research subject in the DLR. In 2003 we started to review this problem to be able to define research projects that could enlighten the problem. Life is the product as well as the subject of a universal evolution process from the most primordial matter to molecules, and finally to cells and complex cellular structures. Living matter, as we know it, consists of carbon, hydrogen, oxygen and nitrogen. According to Curtis and Barnes (1989), nearly 99% of all the atoms in micro-organisms correspond to C (12.1%) H (9.9%) O (73.7%) and N (3%). These atoms are the most abundant reactive elements in the Universe. There are many candidates that could be appropriate places for the chemical synthesis of prebiotic organic molecules. The three most interesting terrestrial sites are:

• Secondary atmosphere (N2, CO2, CH4 / NH3) Currently, most planetary scientists agree that a rapid outgassing from the terrestrial mantle caused the formation of the secondary atmosphere. This process is related to the observations that volcanoes release different gases during the eruptions since their magma contains gas dissolved under pressure. According to Miller and Urey such atmosphere could have provided the material and chemical conditions (reducing milieu) which have led to a spontaneous production of amino acids.

• Warm/hot hydrothermal vents The discovery of extensive ecosystems around hydrothermal vents and the observation that hyperthermophile organisms (heat loving extremophiles) are among the most ancient branches of the tree of life made this assumption very promising. Chemical processes could have been driven by the nearby geothermal energy source, but the high temperatures would destroy the biochemical molecules such as RNA. Other vents (“Lost City”) have temperatures between 40 and 70 ºC. They do not exist on ocean ridges only and allow a survival of complex molecules.

• Lithospheric environment Earliest research on deep-dwelling bacteria starts in 1920 when bacteria from oil deposits in sedimentary rocks 600 m below ground were found. These microbes called thermophiles live within rocks and are adapted to temperatures > 60 o C and an environment without oxygen.

Concerning the formation of the Earth there are three disadvantages which have certainly caused a depletion of the volatile elements in the composition of the Earth: • the distance between Earth and Sun, • the accretion process of the Earth and • the impact of a Mars-like planet that caused the formation of the Moon

These conditions did not allow a high abundance of volatile material. In fact, H2O − a necessary requirement for the formation of life - is much more abundant on Ganymed (65 vol%) than on Earth (0.0013VOL%). In addition, recent observations have suggested that outgassing of the Earth mantle did not have to be very rapid so that there are reservoirs in the mantle layer which never degassed.

Therefore, extraterrestrial sources which could have delivered organic volatiles to the Earth surface are of growing interest. On has to consider:

• Interplanetary dust particles (IPDPs) Direct measurements of the IPDPs flux provided by cratering data from the Long Duration 4 Exposure Facility satellite have given a value of 40 ± 20 ⋅10 metric tons/ yr. The particle flux peaks at a size of nearly 200 µm. IPDPs are formed by collisions of the bodies in the asteroid and Kuiper belt or they are produced from comets reaching the Sun. 0 • Interstellar dust particles (ISDPs) The most important formation sites of ISDPs are the carbon- and oxygen-rich AGB stars. 9 According to Greenberg they live ~ 5 ⋅10 years. During their cycle from diffuse to dense molecular clouds and back to diffuse ones (Fig. 7.4) an ice mantle grows and evolves around the Si-core via accretion and photo-processing. The ice consists of H2O, CO, CO2, and NH3. A typical ISDP can undergo up to 25 cycles before it is destroyed in a blast wave or incorporated into planetesimals or cometesimals. In 2002 Bernstein et al. and Munoz Caro et al. have performed an amino-acid synthesis using ice mixtures that represent analogues of the grain mantles. For conditions typical to the interstellar medium the probes are subjected to UV radiation. Both groups have reported the formation of amino acids whereas in the water-rich mixture only a few ones were produced.

Fig. 7.4 Grain evolution due to the transport shown in Fig. 7.6. Since there is far more hydrogen than anything else the condition of the hydrogen determines what the ice mantles will look like. So, if the hydrogen is atomic then it will add to the less abundant elements (like C, O, and N) making reduced

compounds like water (H2O), methane (CH4),

and ammonia (NH3). If the hydrogen is molecular then the C, O and N have a chance to react with one another forming

molecules like CO, N2, and O2.

• Meteorites especially carbonaceous chondrites Evidence for a complex astro-chemistry comes from the analysis of the Murchison and Tagish Lake meteorites that fell to Earth on September 28th, 1969 and January 18th, 2000. In the Tagish Lake material (Pizzarello et al., 2001) pyridine carboxylic acids and cyclic or ring-aromatic carbon chains were identified. For the Murchison meteorite one has detected over 70 amino acids whereas only 20 can be found in terrestrial samples. In addition the meteoritic amino acids are

more racemic than the terrestrial molecules which are only L- enantiomers. Nevertheless, there is a big debate on the problem of contamination concerning the Murchison meteorite. • Comets as storage of protosolar material One has to consider that cometary material could differ from the ISDPs due to the aging effects in three evolutionary phases which are infall of gas and dust, accretion to comets, and storage in the outer solar system. Recent observation of C/1996 B2 (Hyakutake) and C/1995 O1 (Hale-Bopp) have led to new knowledge on the composition of cometary material. In a paper of Charnley et al., 2001 one finds an organic inventory of a dark molecular Fig. 7.5 Comparison between the abundance cloud (L134N), a cold protostellar core ratios measured in comet Hale-Bopp and those (NGC7538:IRS9), an evolved massive star-forming measured in molecular hot cores and in the bipolar outflow L1157. core (Orion hot cores) and a comet (Hale–Bopp). From the data it is obvious that the two latter targets present a comparable rich organic chemistry. This impression is supported by the abundance relation shown in Fig. 7.5 which is presented by Bockelée-Morvan and Crovisier, Observatoire de Paris (http://www.obspm.fr/actual/nouvelle/comet00.en.shtml).

A method to compare ISDPs and cometary material are the D/H and the HNC/HCN ratios. The comets P/Halley, C/1996 B2 Hyakutake and C/1995 O1 Hale-Bopp give a water derived value −4 of D/H ~ 3⋅10 which is ten to twenty times higher than the protosolar ratio retrieved from H2 and twice as high as the ratio measured in our oceans. However, it is lower than the data estimated for the cold dense molecular clouds but comparable to hot core D/H ratios. In addition it appears that the D/H ratio from organic matter is higher than (D/H)H2O. The HNC/HCN ratio depends on the heliocentric distance. A corresponding observation was made by Schilke et al., 1992, whereby the ratio is higher in a medium vicinity of Orion-KL and declines for the adjacent ridge.

To contribute to the investigations of origins of life we will concentrate our studies on the cometary evaporation and its reflection in the processes around hot cores. The significance of the hot core environment is underlined by the following: Concerning the L- enantiomers mentioned in the context with meteorites it is not known so far why life prefers them.

Fig. 7.6 Left - Interaction between terrestrial and extraterrestrial influences during the formation of life. Since the D/H ratio known for comets and the terrestrial ocean (see right part) suggests a combination of a cometary delivery of water and an outgassing from the mantle it makes sense to assume a similar procedure for the enrichment of organic prebiotic material.

Nevertheless, there is an interesting hint to favour at least partly extraterrestrial organic molecules. A scheme incorporating extraterrestrial organic material into the process of life formation is shown in Fig. 7.6. The organic material forms on the ISDPs. Since these particles are the seeds of cometesimals the organics can be inserted into the comets.

Starting from the idea that the investigation of the similarities between hot core and cometary photo-chemistry will lead to a deeper understanding of the chemical processes on and above the surface of interstellar grains the influence of the UV radiation field on the complexity of the detected organic molecules has to be studied. The relevant measurements will be performed with SOFIA and other telescopes.

8. Space missions

8.1 Rosetta

ROLIS (S. Mottola) The ROLIS experiment is one of the imagers on the Lander of the ESA Rosetta mission. ROLIS will acquire images of the comet surface during the Lander descent phase, with ever- increasing resolution. After landing, it will acquire high-resolution color images of the regions below the lander, from which the in-situ analizers will sample the surface. The cancellation of the launch in January 2003 has required a new series of tests and verifications, as a preparation for the subsequent new launch campaign.

MUPUS-TM (E. Kührt, J. Knollenberg) MUPUS-TM is an experiment onboard the ROSETTA cometary lander, a subunit of the MUPUS suite of instruments (PI: T. Spohn), which is dedicated to the measurement of physical properties of the near surface layers (down to a depth of about 0.5 m) of the target comet. MUPUS-TM consists of a small sensor head equipped with thermopile-IR detectors and a front- end electronics unit. In the MUPUS framework the main task of TM is to measure the surface temperature at the landing, and to derive thermophysical properties of the comet. After cancellation of the Rosetta launch in January 2003 the Lander was dismounted again from the Orbiter and then stored at the launch site in Kourou, until the second launch campaign was started in August 2003. To verify the functionality of the Lander subsystems and payload, an AFT was conducted on 13-th August 2003, which included also a short functional test of MUPUS. The results revealed that MUPUS-TM is still fully operational. Furthermore, the Ground Reference Model (GRM) was delivered on October 29th to the Lander project and integrated into the Rosetta Lander GRM. The GRM also passed the IUT (Integrated Unit Test) without problems.

OSIRIS (E. Kührt, J. Knollenberg) OSIRIS (PI: H.U. Keller) is an imaging system designed to address key problems of the cosmogony of comets by investigating they physical and chemical processes that occur in and near the nucleus. The investigation of the nucleus itself requires high spatial resolution over a wide wavelength range but with modest spectral resolution. The investigation of the innermost dust and gas comae requires a wide field of view with a selection of narrow band interference filters to image the 2-D gas distribution. OSIRIS consists of two cameras: a narrow angle camera (NAC) with a 2.4x2.4° FOV and a wide angle camera (WAC) with a 12x12° FOV.

Our contributions as CoI and team member, respectively, comprise calibration and modelling support. In2003 J. Knollenberg participated in the calibration of the OSIRIS-NAC with special focus on the CCD-performance and linearity of the overall system part in several calibration campaigns.

8.2 Earthguard-I - Phase-A study for ESA (S. Mottola, A. W. Harris, E. Kührt, D. de Niem, G. Hahn)

In January 2003 the final presentation of the Earthguard-I - Phase-A study for ESA was given. This study has been carried out in collaboration with Kayser- Threde with the goal of defining a mission to search for Near Earth Objects (NEOs) which are difficult or impossible to detect from groundbased locations. Based on long-term orbital evolution studies of known NEOs it is expected that a significant fraction of the NEO population has orbits that are mostly or completely inside the Earth's orbit - the so called Atens and Inner-Earth Objects (IEOs). Due to their short Fig. 8.1 The Earthguard-I telescope accommodated orbital periods of less than one year their encounter on the BepiColombo Service Module in orbit around frequency is high, and so is their potential impact risk. Mercury. A space platform orbiting in the inner region of the Solar System would be a vantage point from which these objects could be efficiently discovered and characterized.

The Earthguard-I study resulted in a design for a telescope, including a turntable with one degree of freedom, sensor electronics and a data processing unit, which could be accommodated on a planned spacecraft such as the BepiColombo mission to Mercury (Fig. 8.1), or a dedicated spacecraft which would cruise to a heliocentric orbit of around 0.5 AU utilizing low-thrust propulsion.

In the course of this study several observation strategies were numerically simulated in order to estimate the efficiency of the discovery process. We studied the effects of varying the solar elongation of the scan centres and the telescope aperture sizes for different orbits and mission durations.

ESA has welcomed the results of this project with great interest, and it is planning to initiate a follow-up study that shall capitalize on the results of Earthguard-I and other parallel studies.

8.3 DAWN (S. Mottola, R. Jaumann, H. Michaelis, E. Kührt)

Dawn (Fig. 8.2) is a NASA space mission of the Discovery class that by successively orbiting both 4 Vesta and 1 Ceres addresses the long- standing goals of understanding the origin and evolution of the Solar System. Ceres and Vesta are two complementary terrestrial protoplanets (one apparently "wet" and the other "dry"), whose accretion was probably terminated by the formation of Jupiter. They provide a bridge in our understanding between the rocky bodies of the inner solar system and the icy bodies of the outer solar system. Ceres appears to be undifferentiated while Vesta has experienced significant heating and likely Fig. 8.2 DAWN spacecraft. differentiation. Both formed very early in the history of the Solar System and while suffering many impacts have remained intact, thereby retaining a record of events and processes from the time of planet formation. Detailed study of the geophysics and geochemistry of these two bodies provides critical benchmarks for early Solar System conditions and processes that shaped its subsequent evolution. Dawn provides the missing context for both primitive and evolved meteoritic data, thus playing a central role in

understanding terrestrial planet formation and the evolution of the asteroid belt. Dawn is to be launched in May 2006 arriving at Vesta in 2010 and Ceres in 2014, stopping at each to make11 months of orbital measurements. The spacecraft uses solar electric propulsion, both in cruise and in orbit, to make most efficient use of its xenon propellant. The spacecraft carries two framing cameras, visible and infrared mapping spectrometer, gamma ray/neutron spectrometer, magnetometer, and radio science.

DLR Berlin has participated in the mission since the initial proposal phase. It is represented in the Science Team by two members and contributes critical hardware for the two framing cameras. During 2003 Dawn reached a number of milestones and successfully underwent important reviews: the Phase B study was completed, the PDR was passed, and Phase C and construction phase were started. Similarly, in Berlin the design phase of the camera front-end electronics was finalized, the concept was successfully reviewed, and the manufacturing phase was started.

8.4 Bepi Colombo

BepiColombo (BC), an ESA cornerstone mission in cooperation with Japan, will explore Mercury, the planet closest to the Sun. It will be the first spacecraft to be inserted into orbit around this planet. Europe's space scientists have identified the mission as one of the most challenging long-term planetary projects, largely because Mercury's orbit so close to the Sun makes the planet difficult for a spacecraft to reach and difficult to observe from a distance. Scientists want to study Mercury because of the valuable clues it will provide in understanding how planets form. We announced our interest to participate in this mission with parts of the camera system and an infrared radiometer. Infrared Radiometer IRA (J. Knollenberg, E. Kührt) IRA is designed as a four channel IR-radiometer based on Measuring range 100….700 K thermopiles with in-flight calibration and will measure the Mass < 200 g radiation flux from the surface. The data allow us to derive Wavelength range 1-50 µm) the thermal inertia (heat conductivity some surface Radiometric NETD < 1 K properties (temperature, roughness, emissivity, grain size). Resolution Field of view 2…5° (TBC) Basic parameters of the instrument are given in Table 8.1. The strong temperature variations on Mercury are Ground resolution 10…80 km (TBC) demonstrated in Fig. 8.3. Power 150 mW / 1 W Peak Supply voltages +/-5 V Measurement cycle 4 s (continuous) Data rate 32 Bit/s

Heritage Rosetta, Mupus-TM 16.2.2001, equator Table 8.1 IRA parameters.

800 600 400 in K 200 Fig. 8.3 Calculation of the temperature at a given 0 date at equator around sunrise with moonlike Temperature 0 100 200 300 400 500 properties of the surface. time in h

Camera system (R. Jaumann, E. Kührt, H. Michaelis, S. Mottola, J. Oberst) During year 2003 we have continued our activities for the definition of a BC camera system. In particular, we have developed a concept for an integrated imager for the MPO (Mercury

Planetary Orbiter) which consists of a high resolution channel and a stereo channel with multispectral capabilities.

9. Technology Projects

9.1 AWFS/FIREWATCH (E. Kührt, J. Knollenberg, V. Mertens, T. Behnke)

Every year fires produce damage totalling some ten million Euro in Germany and several billion Euro in Europe. The ground based Autonomous Forest Fire Recognition System AWFS) has been under development since 1998. The project was supported by the European Union and by DLR-TM.

The aim of AWFS is to detect smoke clouds arising from forest fires up to a distance of 10 km within 8 minutes. The complex system consists of advanced hardware and sophisticated image processing software on the basis of IDL. The camera with 1024x1024 pixels was originally developed for space applications.

In 2003 this technology has been successfully transferred to a company that is active on the German market (see http://www.fire-watch.de). About 30 systems were sold under the name FIREWATCH in three German Bundesländer (Brandenburg, Fig. 9.1 Actual Sites of Firewatch Sachsen and Mecklenburg-Vorpommern). Fig. 9.1 shows the in Germany. actual sites of the system. Firewatch didn’t overlook any fire and found good acceptance by the users. Pilot projects have been operated in Canada, Turkey, South Africa and Russia).

The institute's experience in the development of camera systems for space missions and in planetary image processing was of great benefit to this project. The license fees for the AWFS- technology which DLR receives from the industrial partner are several 105 Euros per year.

9.2 Airborne FIREWATCH AFW (E. Kührt, J. Knollenberg)

After the successful development of FireWatch in Germany an airborne system is under development. Market analyses have shown that a big international interest exists for such a development. This is the case where wide areas of forest exist outside on settlements, as e.g., in Canada, Australia, USA and Russia where big forest fire damages are common (Fig. 9.2). But even in Brandenburg a study group was already established on the initiative of the responsible Ministry who should give recommendations to the airborne monitoring of forest fires and other events relevant to security.

The aim of the project AFW, which was started in 2003, is the development of an observation platform for the early recognition of forest fires on the basis of optical technologies (IR and VIS) as well as a module for the radio transmission of the relevant information. Together with our industrial partner Fig. 9.2 An example of fire damage in USA. we are working on a conceptional study. The project is supported by DLR-TM.

Appendix

1. Scientific Publications in refereed journals and books (submitted or published in 2003)

Barbieri, C., Bertini, I., Magrin, S., Salvadori, L., Calvani, M., Claudi, R., Pignata, G., Hahn, G., Mottola, S. and Hoffmann, M. 2003. ADAS: Asiago-DLR Asteroid Survey. Memorie della Societa Astronomica Italiana, v. 74, p. 432.

Barbieri C., C. Blanco, B. Bucciarelli, R. Coluzzi, A. Di Paola, L. Lanteri, G. Li Causi, E. Marilli, P. Massimino, V. Mezzalira, S. Mottola, R. Nesci, A. Omizzolo, F. Pedichini, F. Rampazzi, C. Rossi, R. Stagni, M. Tsvetkov, R. Viotti: Digitization and Scientific Exploitation of the Italian and Vatican Astronomical Plate Archives 2003. Submitted to Experimental Astronomy.

Boattini, A., D'Abramo, G., Scholl, H., Hainaut, O. R., Boehnhardt, H., West, R., Carpino, M., Hahn, G., Michelsen, R., Forti, G., Pravec, P., Valsecchi, G. B., and Asher, D. J. 2003. Near -Earth asteroid search and follow-up beyond the 22nd magnitude: a pilot program with ESO telescopes. Astronomy and Astrophysics, submitted.

Boattini, A., D'Abramo, G., Scholl, H., Hainaut, O. R., West, R., Hahn, G., Michelsen, R., Forti, G., Pravec, P., Valsecchi, G. B. 2003. Eliminating virtual impactors with the Very Large Telescope. An ESO program with the FORS2 camera. Astronomy and Astrophysics, submitted.

Delbo, M., Harris, A. W., Binzel, R. P., Pravec, P., and Davies, J. K. 2003. Keck observations of near- Earth asteroids in the thermal infrared. Icarus, 166, 116 – 130.

Goldammer, J.G., A.C. Held, M. Hille, K.-P. Wittich, E. Kührt, N. Koutsias, and D. Oertel 2003. An Innovative Conceptual Model of a Forest Fire Management Information and Decision-Support System for Brandenburg State. Natural Hazards, submitted.

Marczewski, W., K. Schröer, K. Seiferlin, B. Usowicz, M. Banaszkiewicz, M. Hlond , J. Grygorczuk , St. Gadomski, J. Krasowski, W. Gregorczyk, G. Kargl, A. Hagermann, A.J. Ball, E. Kührt, J. Knollenberg, T. Spohn 2004. Pre-Launch Performance Evaluation of the cometary experiment MUPUS-TP. JGR accepted.

Merin, B. and 23 colleagues, incl Harris, A. W. and Rauer, H. 2003. Study of the properties and spectral energy distributions of the Herbig AeBe stars HD 34282 and HD 141569. Astronomy and Astrophysics, submitted.

Mora, A. and 24 colleagues, incl. Harris, A. W. and Rauer, H. 2003. Dynamics of the circumstellar gas in BF Orionis, SV Cephei, WW Vulpeculae and XY Persei. Astronomy and Astrophysics, submitted.

Russell C.T., A. Coradini, U. Christensen, M.C. De Sanctis, W.C. Feldman, R. Jaumann, H.U. Keller, A.S. Konopliv, T.B. McCord, L.A. McFadden, H.Y. McSween, S. Mottola, G. Neukum, C.M. Pieters, T.H. Prettyman, C.A. Raymond, D.E. Smith, M.V. Sykes, B.G. Williams, J. Wise, and M.T. Zuber: Dawn: A Journey in Space and Time 2003. Planetary and Space Science, in press.

Weiler, M., Rauer, H., Knollenberg, J., Jorda, L., Helbert, J.; The dust activity of comet C/1995 O1 (Hale-Bopp) between 3 AU and 13 AU from the Sun, A&A 403, 313-322 (2003).

2. Scientific publications in other journals and proceedings (published in 2003)

Claudi R.U., M. Calvani, C. Barbieri, S. Magrin, P. Bruno P., S. Mottola. The Asiago NEO and Exoplanet Search with the Refurbished Schmidt Telescope. Joint and National Astronomical Meeting for 2003 12th European Meeting for Astronomy and Astrophysics. JENAM 25-30 August 2003 Budapest Hungary.

de Niem, D. 2003. A model of early condensate composition in impacts. Third international conference on large meteorite impacts. Nördlingen, abstract no. 4069.

Hahn, G., Harris, A. W., Jaumann, R., Köhler, U., and Kührt, E. 2003. Die Kleinkörper des Sonnensystems. Sterne und Weltraum Special, 2/03, p. 6 – 27.

Harris, A. W. 2003. Asteroiden – Trümmer aus planetarer Urzeit. 2003, Sterne und Weltraum Special, 2/03, p. 48 – 61.

Harris, A. W. 2003. Die Asteroidenforschung im Zeitalter der Raumfahrt. Raumfahrt Concret, no. 29/30, issue 4/5/ 2003.

Harris, A. W., Delbo, M., and Binzel, R. P. 2003. The physical characterization of near-Earth asteroids: latest results of a program of thermal-infrared observations. American Astronomical Society, DPS meeting #35, #22.03.

Kührt, E., Arnold, G., and Keller, H.U. 2003. Rosetta – Naherkundung von Kometen. Sterne und Weltraum Special, 2/03, p. 38 – 44.

Kührt, E., Knollenberg, J. 2003. Fire detection in Germany. Proceedings of III. Wildfire Conference, Sydney.

McCord, T., C. T. Russell, A. Coradini, M. C. DeSanctis, W. C. Feldman, R. Jaumann, A. S. Konopliv, L. A. McFadden, H. Y. McSween, S. Mottola, G. Neukum, C. M. Pieters, C. A. Raymond, D. E. Smith, M. V. Sykes, B. G. Williams, J. Wise and M. T. Zuber, Dawn: A journey in space and time, presented at EGS-AGU-EUG Joint Assembly, Nice, France, April 2003.

Mueller, M., Harris, A. W., Delbo, M., and Bus, S. J. 2003. The sizes and albedos of near-Earth asteroids, including 6489 Golevka, from recent IRTF observations. American Astronomical Society, DPS meeting #35, #22.04.

Omizzolo A., C.Barbieri, C. Blanco, B. Bucciarelli, R. Coluzzi, A. Di Paola, L. Lanteri, G. Li Causi, E. Marilli, S. Mottola, R. Nesci, F. Pedichini, F. Rampazzi, C. Rossi, M. Tsvetkov. Status of the Digitization of the Archives of Photographic Plates of the Italian Astronomical Observatories and of the Specola Vaticana 2003. IAU General Assembly, Sydney.

Russell C.T., A. Coradini, M.C. De Sanctis, W.C. Feldman, R. Jaumann, A.S. Konopliv, T.B. McCord, L.A. McFadden, H.Y. McSween, S. Mottola, G. Neukum, C.M. Pieters, T.H. Prettyman, C.A. Raymond, D.E. Smith, M.V. Sykes, B.G. Williams, J. Wise, and M.T. Zuber: Dawn Mission: A Journey in Space and Time 2003. Lunar and Planetary Science XXXIV (Extended Abstract), Houston.

3. Minor Planet Electronic Circulars

Karlsson, O., and 53 coauthors, including Hahn, G. and Mottola, S. Observations of Comets. Minor Planet Electronic Circ., 2003-W62 (2003). Lehky, M. and 75 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-V17 (2003). Karlsson, O. and 15 coauthors, including G. Hahn and S. Mottola. COMET C/2003 H1 (LINEAR). Minor Planet Electronic Circ., 2003-J30 (2003). Karlsson, O. and 70 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-G54 (2003). Lehky, M. and 38 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-G15 (2003). Karlsson, O. and 4 coauthors, including G. Hahn and S. Mottola. COMET C/2003 F1 (LINEAR). Minor Planet Electronic Circ., 2003-G14 (2003).

Lehky, M. and 56 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-F54 (2003). Sanner, J. and 47 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-F23 (2003). Sanner, J. and 59 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-E64 (2003). Lehky, M. and 12 coauthors, including G. Hahn and S. Mottola. COMET C/2002 Y1 (JUELS- HOLVORCEM). Minor Planet Electronic Circ., 2003-D25 (2003). Boattini, A. and 8 coauthors, including G. Hahn. 2001 SK9. Minor Planet Electronic Circ., 2003-C59 (2003). Boattini, A. and 8 coauthors, including G. Hahn. 2001 FF7. Minor Planet Electronic Circ., 2003-C58 (2003). Boattini, A. and 8 coauthors, including G. Hahn. 2000 AD6. Minor Planet Electronic Circ., 2003-C55 (2003). Boattini, A. and 8 coauthors, including G. Hahn. 1999 TB5. Minor Planet Electronic Circ., 2003-C54 (2003). Tichy, M. and 79 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-C48 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 2003 BH84. Minor Planet Electronic Circ., 2003-C35 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 2002LW. Minor Planet Electronic Circ., 2003-C30 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 2002 FA6. Minor Planet Electronic Circ., 2003-C29 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 2001 BP61. Minor Planet Electronic Circ., 2003-C28 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 1999 RC32. Minor Planet Electronic Circ., 2003-C27 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 1998 ST49. Minor Planet Electronic Circ., 2003-C26 (2003). Boattini, A. and 5 coauthors, including G. Hahn. 2003 BC46. Minor Planet Electronic Circ., 2003-B56 (2003). Lehky, M. and 53 coauthors, including G. Hahn and S. Mottola. Observations of Comets. Minor Planet Electronic Circ., 2003-B25 (2003). Lehky, M. and 28 coauthors, including G. Hahn and S. Mottola. COMET C/2002 Y1 (JUELS- HOLVORCEM). Minor Planet Electronic Circ., 2003-A85 (2003). Davidsson, B. and 15 coauthors, including G. Hahn and S. Mottola. COMET C/2002 U2 (LINEAR). Minor Planet Electronic Circ., 2003-A81 (2003).

4. Publications in the popular literature and public outreach

G. Hahn

• Radio call-in programme: Deutschland Radio, 22.12.2003, on the subject of the asteroid impact hazard, in collaboration with the German science magazine Bild der Wissenschaft.

A. W. Harris

• Consultant for articles on asteroids and planetary phenomena, incl. reports of research work described in the section "Asteroid Science" above: Profil (Austrian News Magazine), 6.10.03 SonntagsZeitung (Swiss newspaper), 13.10.03 Berliner Morgenpost, 16.11.03 Tagesspiegel, 17.11.03 Die Welt, 19.11.03 Nature, 426, p. 242, 20.11.03 New Scientist, 13.12.03

Frankfurter Rundschau, 9.12.03 Berliner Morgenpost (B.I.Z.), 21.12.03

• Radio interview for regional radio station, Mecklenburg Vorpommern, 20.09.03. • Lecturer "Studium Generale", Technical University of Dresden, 8.01.03 and 8.12.03. • Invited lectures: Bruno-H.Bürgel Observatory, Berlin Spandau, 7.03.03. DLR, Oberpfaffenhofen, 7.04.03. 19. Tag der Raumfahrt, Neubrandenburg, 20.09.03. Inst. Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, 11.11.03. Inst. Raumfahrtsysteme, Univ. Stuttgart, 18.12.03. • Lecturer "Lange Nacht der Wissenschaften", 14.06.03. • Lecture to students of the Humboldt Gymnasium, Eichwalde, "Asteroids and Comets", 10.02.03; 4.03.03; and 23.10.03. • Lecture to various visiting school groups, "Asteroiden und Kometen", 17.06.03; 19.06.03; 2.07.03.

E. Kührt

• Invited presentation at FERIC, Hinton, Canada, March 2003 • Lecturer "Lange Nacht der Wissenschaften", 14.06.03. • Several radio interviews

5. Space mission responsibilities

J. Knollenberg

• Rosetta: Co-Investigator MUPUS, associated scientist of OSIRIS

E. Kührt

• Co-Investigator ROSETTA-experiments: OSIRIS, RPC, ROMA, SESAME, and MUPUS • Team member DAWN

S. Mottola

• PI of the ROLIS experiment on the Lander of the ESA Rosetta mission. • Co-I of the VIRTIS experiment on the ESA Rosetta mission. • Co-I of the NASA DAWN mission. • Member of the ESA Science Advisory Working Group for the BepiColombo Mission.

6. Observing Campaigns 2003

Date Telescope Targets ______

January Calar Alto Test measurements 4-7 May UKIRT NEAs (reflection spectroscopy) 10,13,15 May IRTF NEAs Sekhmet, Golevka (thermal-IR) 1-3 Jun. ESO 3.6m NEAs (various; thermal-IR) ______

UKIRT is the 3.8-m UK Infrared Telescope on Mauna Kea, Hawaii. The IRTF is the 3.0-m NASA Infrared Telescope on Mauna Kea, Hawaii.

7. Other events and activities

G. Hahn • German representative, OECD Workshop on Near Earth Objects: Risks, Policies and Actions, January 20-22, 2003, Frascati, Italy.

A. W. Harris • Member of the ESA expert committee established to examine proposals for space-based studies of near-Earth objects. • Member Scientific Organizing Committee, Asteroids, Comets, Meteors, 2005. • Referee for the journals Icarus and the Astronomical Journal. • Member of the organizing committee of Commission 15, "Physical Studies of Asteroids and Comets", of the International Astronomical Union.

J. Knollenberg • DLR innovation award • Member of the ESA environmental working group for Rosetta

E. Kührt • DLR innovation award • Referee for the journal PSS

S. Mottola • Referee for the journals Icarus, PSS, Astronomy&Astrophysics, Advances in Space Research

8. Funding

Our funding comes from DLR-projects as Rosetta, Dawn, Comets&Asteroids, Development and age of planets, and others. Furthermore, several colleagues are involved in projects where funding origins from outside:

G. Hahn ESOC contract 15836/01/D/HK(SC) [30036 €]: Extension of the optical observation capabilities of a 1m telescope. Subcontracted from the Astronomical Institute of the University of Berne. The project aims to use the 1m Zeiss telescope at Teneriffe for astrometric observations of asteroids and comets, especially NEOs. Our subcontract concentrates on searching strategies, observation planning, and simulations of observing campaigns.

A. W. Harris Support for the third year of a project entitled "Investigation of the physical properties and origins of near-Earth objects" from the German Research Foundation DFG (HA 2914/1-4). The support covers a stipendium for a postgraduate student and funds for observation campaigns, etc.

E. Kührt and J. Knollenberg • License earnings for technology transfer FIREWATCH (ca. 200000 €) • Industry contract with IQ wireless GmbH (10000 € for calibration work)

G. Hahn, A. Harris, E. Kührt, S. Mottola Earthguard-I, funding ca. 60000 € by ESA: This study has been carried out in collaboration with Kayser-Threde with the goal of defining a mission to search for Near Earth Objects (NEOs) within the Earth orbit which are difficult or impossible to detect from groundbased locations.