Giovanni B. Valsecchi

                        IASF-CNR, Istituto di Astrofisica Spaziale e Fisica Cosmica
                               via Fosso del Cavaliere 100, 00133 Roma (Italy)

Some recent advances in the theory of close encounters between small  bodies and the Earth are described, with particular emphasis on the phenomenon of resonant returns. In this last case, the theory allows to understand the basic geometrical features of the phenomenon, and to compute the location, size and shape of impact keyholes; moreover, it allows to quantify the reduction of the impulse needed to deflect a NEA away from a collision course. Some examples will be discussed.


                                     "VERY SHORT ARC ORBIT DETERMINATION"

                                                            Andrea Milani

                                        Dipartimento di Matematica 
                                   Via Buonarroti 2 56127 PISA ITALY

"How to make do with One Night Stands" and "why even a ONS contains useful information"



Mark R. Kidger 
Instituto de Astrofísica de Canarias

67P/Churyumov-Gerasimenko is the new target of the ROSETTA mission after the failure of ROSETTA to meet the strict launch window for an encounter with 46P/Wirtanen. 67P is a comparatively recent visitor to the inner solar system having had q=4.0AU prior to 1840 and q>2.75AU until a Jupiter encounter in 1959. The recent large downward jumps in perihelion distance are almost certainly the drivers of 67P/Churyumov-Gerasimenko's high level of activity. The light curve, photometric evolution and morphology of the comet during the 2002/2003 apparition are studied through the observations of the Spanish language (although international) "Observadores_cometas" group.



     Mark R. Kidger  

Instituto de Astrofísica de Canarias

The apparition of 153P/Ikeya-Zhang = C/2002 C1 (Ikeya-Zhang) has been one of the most important cometary apparitions of recent years. For the first time a comet with a period greater than 156 years has been observed at more than one apparition. Despite the identification of C/1661 C1 with 153P/Ikeya-Zhang there remains the questions of the inferred major change in the light curve between 1661 and 2002 and of the original preferred identification with C/1532 R1, which has a strikingly similar orbit. One possibility is that C/1532 R1 and 153P are fragments of a single object that split in the past. A possible splitting scenario is examined. The possible identification of previous apparitions of 153P in 837 and 1273 is examined critically. It is shown that if these identifications are correct, the absolute magnitude of the comet has faded considerably with time, although this in itself may be consistent with an object that is evolving photometrically after a major splitting.



Mark R. Kidger

Instituto de Astrofísica de Canarias

A difficulty that observers face when taking data of comets is how to standardise their data to make it compatible with other observers using different instruments. The widespread use by amateurs of CCD cameras of high sensitivity and good cosmetic quality enormously increases the possibilities of photometric coverage of comets given that photometry is calculated automatically with astrometric observations. Although the MPC database now contains huge amounts of comet photometry, the lack of any standard method for taking this data means that the dispersion in photometry of a comet in the MPC database may be as large as 2 magnitudes at a given date even for magnitudes given as "N". In this paper we explore a standard system of photometry that is widely used by Spanish and Italian observers based on the USNO A2.0 catalogue and a series of standard photometric apertures. The suitability of the USNO catalogue for photometric work is examined critically and examples of comet light curves and coma profiles are shown. A transformation of USNO A2.0 to the standard Landolt BVR system is presented.



       M. Merino3, J.Núñez1,3, J.L. Muiños2, O.Fors1,3, F.Belizón2, M. Vallejo2 and J.M. Codina1

1 Observatori Fabra. Reial Acadèmia de Ciències i Arts de Barcelona  
Camí de l'observatori s/n, E-08035 Barcelona. e-mail: jorge@am.ub.es

2 Real Instituto de la Armada en San Fernando.
Cecilio Pujazón s/n, E-11110 San Fernando. e-mail: ppmu@roa.es

3 Departamento de Astronomia y Meteorologia. Universidad de Barcelona.
Av. Diagonal 647, E-08028 Barcelona

   We present the transformation of a Baker-Nunn Camera (BNC) for remote and robotic use with a large format CCD, and its transfer to a new site located in Catalan Pyrenees. This project is a collaboration between the Fabra Observatory (Reial Acadèmia de Ciències i Arts de Barcelona) and the Real Observatorio de la Armada de San Fernando (ROA). Once refurbished, the 50cm f/1 camera will have a useful FOV of 5ºx5º and will be controlled via Internet.
 This is not a restoration of an old astronomical facility but a completely innovative refiguring of the instrument. We will modify both its mechanics and optics and will set up a new unique facility in Catalonia operating in real robotic and remote mode.
 Once the BNC will be operating, our scientific project considers two kinds of observing programs: a systematic observing program (QDDS) and selective observing programs.

The Quick Daily Sky Survey will operate by means of TDI (Time Delay Integration) CCD observation. It will be able to cover almost the entire northern sky in 4 or 5 nights up to V=20 producing up to 25 Gb/night of data. The other specific observing programs include the discovery and tracking of solar system objects (NEOs, PHAs, main belt asteroids, comets and TNOs), the detection of extra-solar planets, the detection of novae and supernovae, the quick localization of counterparts of GRBs, the detection of dangerous space debris and, in general, any program that could benefit of the large FOV and quick reaction of the camera.


                                                      PROPERTIES OF ASTEROIDS

        Jordi Llorca1,2  

1Dept. Química Inorgànica, Universitat de Barcelona. 2Institut d’Estudis Espacials de Catalunya. jordi.llorca@qi.ub.es

Asteroids have become objects of intense interest for planetary astronomers. They occupy the transition zone between the dense, volatile-poor terrestrial planets and the icy, gas-rich outer planets and satellites. Although a thorough understanding of the nature of asteroids is very important for science and because some of them may be potential impactors, we have not yet analysed directly any asteroid, either in situ or by sample return. Meteorites represent our best choice to know the physical and chemical characteristics of asteroids, but we do not know to what extent the information revealed by meteorites is representative enough. Therefore we need to obtain additional data using telescopes on Earth. Reflectance spectroscopy in the wavelength range 0.3-1.1 mm constitutes a good approach in order to obtain the mineralogical composition of the surface of asteroids. These data is compared to the spectral reflectivities of various types of powdered meteorites measured in the laboratory in order to provide a basis for chemical models and population distribution. Many different spectral types and mineral compositions are recognised among asteroids, but almost 75% of them appear to be similar to carbonaceous chondrites (which represent less than 3% of all meteorites recovered on Earth!). They consist of volatile-rich, low-density materials that probably condensed directly from the solar nebula at low temperatures. Another 15% of the asteroids seem to be composed of iron- and magnesium-rich silicate minerals with little dark carbonaceous material. These asteroids may never have been melted, but metamorphic or condensation temperatures must have reached 850ºC within relatively shallow layers, resulting in dense bodies. Relatively rare asteroids appear to be composed of solely metal (iron-nickel alloys), resulting from a molten state at temperatures exceeding 1400ºC. Most of the metallic asteroids are 100 to 200 km in diameter and do not appear to be fragmented like the other types of asteroids. On the other hand, Apollo-Amor asteroids exhibit reflectance spectra similar to ordinary chondrites (70% of recovered meteorites), whereas main-belt asteroids do not. Both experimental studies of the effect of space environment on the optical properties of mineral grains as well as more refined spectral comparisons of asteroids with meteorites are required in order to gain a better insight into the physical properties and composition of asteroid types.


                                     "A QUICK LOOK AT SOME NEW STAR CATALOGS"

                                                     Herbert Raab

                      Davidschlag Observatory, Astronomical Society of Linz, Austria

Some new astrometric star catalogs have recently become available, among them the Guide Star Catalog 2.2 (GSC 2), the USNO-B1.0, and the USNO CCD Astrograph Catalog 2 (UCAC 2). Both the GSC and the USNO-B are based on data collected from scanning photographic plates from the Palomar and Southern Sky Surveys. Positions in the UCAC,
on the other hand, are derived from recent CCD observations, and proper motions are calculated from various earlier epoch data.
A comparison of the features of these catalogues is presented, and results obtained with these catalogs on a few sample images are compared.



                                                Konrad Dennerl
                             Max-Planck-Institut fuer extraterrestrische Physik
                             Giessenbachstrasse, D-85748 Garching, Germany

Having accompanied mankind since historical times, comets have kept an invisible secret until recently. In 1996 the surprising discovery was made that they do emit X-rays. This radiation turned out to reveal properties of comets not observed before. Their X-ray emission is characterized by rapid intensity fluctuations, and X-ray images are distinctly different from optical images, showing none of the characteristic tails, but bright emission from the sunward side of the coma, with the brightest region displaced from the cometary nucleus towards the Sun. For typical observing geometries, comets appear as diffuse crescents in X-rays, resembling more the Moon than a comet.
The origin of the cometary X-ray emission - a long-standing puzzle - is now generally understood. The X-rays are produced when highly charged heavy ions in the solar wind encounter gas in the cometary coma and are discharged there. This process leaves a characteristic signature in the X-ray spectrum, which contains information about the chemical composition and ionization structure of the heavy ion content of the solar wind. These properties are related to the type of solar wind, which is usually fast, steady and of low density at high heliographic latitudes and slow, highly variable and of high density at
low latitudes. The type of solar wind can be deduced from the optical appearance of the cometary plasma tail. Thus, optical images of comets, taken simultaneously with X-ray observations, provide independent complementary information about the solar wind, which is important for a detailed comparison with the X-ray data. This approach has become particularly interesting with the recent advances in X-ray spectral resolution, achieved with the X-ray satellites Chandra and XMM-Newton. The talk will summarize our current
understanding and will present the latest results in this young field of research.


                                       COMETS: ORIGIN AND EVOLUTION

  Marcos Rincon Voelzke

           Department of Informatic, Cruzeiro do Sul University, Regente Feijo Avenue 1295, 03342-000 Sao Paulo, SP, Brazil E-mail: voelzke@zipmail.com.br

The present contribution reviews our current understanding of the origin, nature and evolution of comets (Brandt, 1990; Voelzke and Matsuura, 1998). It also discusses the evolutionary scenarios that have been proposed so far to explain the observed morphological structures along the cometary plasma tail (Brandt et al., 1999; Brandt and Snow, 2000; Voelzke and Matsuura, 2000; Voelzke, 2002). Comets are the most primitive members of our solar system. Because of their orbits and small size, comets have undergone relatively little processing, unlike larger bodies such as the Moon and the Earth, which have been modified considerably since they formed. This pristine nature of comets is evidenced in their high abundance of volatile compounds. The composition of comets contains a wealth of information on their origin and evolution as well as the origin and evolution of our solar system; hence, they are often referred to as cosmic fossils. Our view of plasma structures in comets was based on the ideas of Biermann (1951) as extended by Alfven (1957) to include the effects of the solar wind magnetic field. The solar wind interacts with bright comets through its magnetic field and the cometary ions which are produced in an extended region around the comet. The field lines away from the comet are unimpeded and thus wrap around the comet to create a magnetic field in a hairpin configuration, i.e., a configuration with lobes of opposite polarity separated by a current sheet. Some part of this total magnetic structure includes the visible plasma tail. Because the comet is an obstacle in a supersonic and super-Alfvenic solar wind, a bow shock was also expected. Despite the sketchiness of many of the details, this picture presented specific tests of the data returned by the flyby spacecraft sent to comets P/Giacobini-Zinner and P/Halley.

     -   Alfven, H.: 1957, Tellus 9, 192 pp.
-   Biermann, L.: 1951, Z. Astrophys. 29, 274 pp.
-   Brandt, J.C.: 1990, in J. Watson (ed.), Comet Halley: Investigation,    
          Results, Interpretation 1
, Ellis Horwood, New York, 33-55.
-   Brandt, J.C., Caputo, F.M., Hoeksema, J.T., Niedner, M.B.Jr., Yi, Y. and 
          Snow, M.: 1999, Icarus 137, 69-83.
-   Brandt, J.C. and Snow, M.: 2000, Icarus 148, 52-64.
-   Voelzke, M.R.: 2002, EM&P 90, 405-411.
-   Voelzke, M.R. and Matsuura, O.T.: 1998, Planet. Space Sci. 46, 835-841.
-   Voelzke, M.R. and Matsuura, O.T.: 2000, A&AS 146, 1-5.



                      Gyula Szabo, graduate astronomer, graduate student of physics,

                    University of Szeged, Dept. of Experimental Physics and Astronomical

Nowaday's revolution of observing astronomy offers very high-quality amateur observations in cometary studies as well. These observations may, however, be lost if not archieved soon. On the other hand, valuable continuous data on comets are highly required for evolution studies by professionals; the archivation of the data is therefore requred by both kind of astronomers.
An archieve for amateur astronomer is not a nowelty in astronomy. The previous examples suggest that we wish to develop an archieve likely to what MPC does. The conception is to offer a very pure data format to the observer so that calculations and upload will not take more than few minutes.
In contribution with Szeged University, Visnjan and Rijeka Observatories, UAI designed this archivation of amateurs' data on comets. The archieved observable is the so-called Afrho, a parameter measuring the dust very independently on the observation circumstances. Anyone wherever in the World can upload data and query the archieve. We force no selection criteria of the individual objects, any comet is a potential target of CARA. Data can be queried by name and/or by times of observations. The system will not include the observed images theirselves, but we wish to
offer, optionally, to concede a reference web page or an e-mail account of contact. Here the analyst who wants to re-reduce the data or asks for the original image can correspond the observers.
Presentation discusses the basics of comet photometry, the meaning of Afrho and its measurement. We distribute an easy code that calculates Afrho from simple photometric parameters. We introduce the web page of CARA, show how to upload data and query the archieve. Hopefully, the first promising results achieved by the members of UAI encourage many new observers to join this project. We wish this archieve be succesful, adding no end of nice data to the understanding of comets!



J. Skvarč

    Črni Vrh Observatory, Slovenia jure.skvarc@ijs.si

With the start of NEO follow-up and asteroid search program at the Črni Vrh Observatory in 1997 also a complete set of software tools used for telescope control, astrometry and data archiving started development.  The central part of this software, fitsblink, began as a simple software for blinking FITS images on the Unix and Linux based computers.  New capabilities were added as needs arose, especially automatic matching of the catalog stars what was not a common feature at the time.  However, several functions needed for automatic asteroid observations were left outside fitsblink in a form of independent programs which were joined in a data processing pipeline using scripting languages like Perl and Python.  With the forthcoming new release of fitsblink, an integration of functions such as asteroid movement detection, automatic image alignment etc, has started.   In addition, several new functions are introduced:  image addition and subtraction, comet photometry, trail detection, sky gradient subtraction etc.  All data analysis functions are also available from the Python scripting language what allows simple creation of specialized data processing procedures specific to the needs of individual observers.


                                                THE SPACEGUARD CENTRAL NODE

                                                Andrea Boattini and Germano D'Abramo

                            IASF-CNR, via Fosso del Cavaliere 100, 00133 Roma (Italy)

The Spaceguard Central Node (SCN) has operated since the end of 1999 for the international coordination of NEO astrometric follow-up observations. Several services, updated on a daily basis, provides important guidelines for the observing communities. Other non dynamic services provides general suggestions or information
on targeted observational campaigns. The SCN has helped observers to reduce drastically the number of km or nearly km-sized NEOs that goes lost for insufficient coverage.



                                                 Andrea Boattini

                          IASF-CNR, via Fosso del Cavaliere 100, 00133 Roma (Italy)

After a long hiatus CINEOS (Campo Imperatore Near earth Object Survey) restarted regular observing operations in June 2002. Since then it has discovered 3 NEAs and many hundreds of MBOs becoming the most prolific site in Europe. A NEO pilot program was recently conducted at ESO-La Silla with the 2.2-m Wide Field Images and the New Tecnology Telescope: this test led to the discovery of two NEAs and to the follow-up of many faint NEOs.


                                                       EARTH OBJECTS

                                      Juraj Toth, Leonard Kornos

           Astronomical Institute Faculty of Mathematics, Physics and Informatics
                      Comenius University 842 48 Bratislava Slovak Republic

We estimate the frequency of not very well known population of very small Near Earth Objects (~100m - 10m in diameter) which approache the Earth within the Moon distance. Also we propose an outline of a new survey system for such objects.



B. Dintinjana, S. Maticic, H. Mikuz, J. Skvarc, D. Zgavec

Crni Vrh Observatory, Slovenia

     After the telescope installation in summer 2002, we had first light on September 2, 2002. Since then, the system has been in trial operation during which we optimized it to fully achieve designed specifications. We report the results of a telescope calibration tests which include pointing and guiding accuracy, focus stability and photometric calibrations.  We achieved all-sky pointing accuracy of 2 arc min without the implementation of any corrections or encoders. Using the software corrections, we achieved 30 arc sec. Unguided exposures of up to 15 minutes duration are possible on sky areas where refraction effects are negligible. During the January – March 2003 period, we obtained a series of filtered CCD images of various deep sky objects and comets, including C/2002 V1 (NEAT) and C/2002 Y1 (Juels-Holvorcem). These results show the telescope superb imaging performance.         The telescope operation is now fully robotic. Once the list of targets is prepared by observer, the system perform imaging of objects without  intervention of observer. Our imaging system was designed to be used over the internet and we regularly perform remote observations. Current efforts are to complete computer control of observatory roof and incorporate the weather station. When completed, this final step in automatization will enable fully unattended remote observations.    
    The 60-cm telescope has been put in regular operation in March 2003. On March 5, 2003, we discovered our first NEO, the Aten family 2003 EM1.  Several NEO observations have been successfully performed. Using an advanced electronics system, the telescope guiding speed can be adjusted to follow any fast moving object. Fainter, fast-moving NEO's can be easily tracked and measured.



Migliorini A.1, Magrin S.1, Marchi S.1, Skvarc J.2, Barbieri C.1, Marzari F.1, Scholl H.3, Albrecht R.4

1 University of Padova, 2  Crni Vrh Observatory, 3 Observatoire de Nice, 4 ESA/ECF

   Here we describe the current status of an on-going work, performed in the frame of an approved ASTROVIRTEL program, having the aim to detect bodies orbiting around the Lagragian points of the outer planets (namely Saturn, Uranus, Neptune), analogous to the Jupiter Trojans. Till now, a large number of images taken with the WFI of the 2.2 m telescope of ESO at La Silla has been examined.  Due to the specific nature of our search, using archive images, a special observatory code I03 was assigned by the Minor Planet Center. Although still unsuccessful in respect to outer Trojans, the search  has already produced many new asteroids, some with interesting orbits.
    Up to now we selected 1066 scientific WFI images of which about 750 have been completely analyzed. As a result we have already submitted to the MPC 50 reports, containing approximately 300 distinct asteroids. The faintest objects are around R = 24.0; there are also several fairly bright but not numbered objects (e.g. R = 15.9). The MPC has awarded about 10 preliminary designations. Moreover we have found new positions (dated back to Aug. 2000) for the lost Near Earth Object 2001 AV43. A statistical analysis of the material is fairly difficult, because we are using plates taken with a variety of filters, exposure times and positions. At any rate, this analysis is certainly worth doing. We are going to analyze different images available in Astrovirtel database (e.g. taken with WFPC of the HST) and in other archives (i.e. SMOKA archive of Subaru Telescope) to improve our search program.
   The support given by ASTROVIRTEL, a Project funded by the European Commission under P5 Contract No. HPRI-CT-1999-00081, is acknowledged.


Johnson V-band Photometry of Minor Planets based on the Hipparcos 
An observing methodology for determining accurate magnitude - phase angle parameters.

                                                     Richard Miles 
                                        Golden Hill Observatory, Dorset, UK

Physical classification of asteroids would greatly benefit from an expansion of current magnitude-phase angle observations to include many more objects than to date, and to extend coverage to small phase angles.  A proposal is put forward for a CCD observing methodology which exploits the precision photometry of the Hipparcos Catalog to yield accurate Johnson V-band photometry of asteroids.

The approach is to reference CCD images of asteroids relative to images of Hipparcos stars, selected to meet the criteria: 5.0<V<9.5 and +0.4<(B-V)<+1.0.  Images of both are taken either with the same camera or, preferably, using a second CCD camera attached to a shorter focal length / small aperture telescope or lens.  It is recommended that the CCD camera used has a ‘pseudovisual’ spectral response similar to the S20 photocathode as used on the Hipparcos satellite and that it is used unfiltered.

  Calibration of the CCD camera calls for an accurate determination of the transformation coefficient for conversion from the instrumental magnitude system of the camera to the Hipparcos, Hp magnitude system.  The author also demonstrates that the read-across from Hp magnitude to Johnson V magnitude can be carried out with an accuracy of better than 0.004 mag based on Landolt or E-region standard stars.


                                         OF THE OBSERVATORY OF MALLORCA

                                         Avila G.1, Guarro J.2, Sanchez S.2, Nomen J.2 

                        1 European Southern Observatory, Garching bei Muenchen, Germany
                     CAOS Club of Amateurs in Optical Spectroscopy
                   2 Observatorio Astronomico de Mallorca          

The OAM (Observatori Astronomic de Mallorca) in collaboration with CAOS (Club of Amateurs in Optical Spectroscopy) has buildt three all spherical, compact, catadioptrics of 60 cms aperture telescopes. The optical design is based in a model for small apertures by Yuri Klevtsov. Given the large apertures and the requirement for a half degree field of view, our design requires an additional coma corrector. This paper describes the optical design and present status of the project.



                                       Avila G., Guirao C., Rodriguez J.

                       European Southern Observatory, Garching bei Muenchen, Germany
                  CAOS Club of Amateurs in Optical Spectroscopy

We present a summary of the spectra of bright comets obtained with
FIASCO (FIbre Amateur Spectrograph Casually Organized), a low
resolution spectrograph. A description of performance of the spectrograph and exploration for other astronomical analysis is also presented. Finally, we describe the status of LECHES, a high resolution echelle spectrograph being built in collaboration with OAM.




Jonathan Shanklin

British Astronomical Association

The British Astronomical Association (BAA) has been observing comets since its inception in 1890 and a formal comet section was set up in 1891.  Unfortunately all early records were lost during the Second World War and the earliest extant records date from the 1940s.  The majority of observations made since then have been logged in the standard format used by the International Comet Quarterly (ICQ) and are available in electronic format.  In total there are over 30,000 observations of some 400 comets, including returns of 80 periodic comets.  Observers and observations come from all the continents.  Detailed reports on the comets seen each year are published in the British Astronomical Association Journal, and current information is available on the Comet Section web page at http://www.ast.cam.ac.uk/~jds  The Section also publishes a twice yearly newsletter The Comet's Tale.
Selected apparitions from the archives are used to illustrate various types of cometary light curve, including some that show linear behaviour with respect to perihelion as well as the majority, which show the more normal power law behaviour.  Other examples are selected to show outbursts, or sudden fading.  A few comets have been observed at several returns and the light curves of these comets are used to demonstrate any secular changes in their absolute magnitude. 
There are several controversial issues that may be worth discussing further at this meeting:
a)  There are many different formats being used to report comet observations, despite the standard set by the ICQ.  The wide variety of formats in use tends to result in poor formatting of electronic submissions, resulting in much extra work for the analyst.  Should European observers standardise on the ICQ format, or alternatively should we make use of software to translate between the various national formats ?
b)  Many observations are made in light polluted areas.  Should such observations be rejected ?
c)  Some analysts prefer to select observations made by 'experienced' observers and reject all others.  Is this a valid approach ?
d)  How many observations, made at the limit of observing conditions, are hallucinations ?




                                                    Korado Korlevic

                                              Visnjan Observatory


                                                ON SPLITTING OF COMETS

                                                  Mike Kletlow

                        Max-Planck-Institut fuer Kernphysik, Heidelberg, Germany

In the past 160 years about 35 split comets have been observed.
Additionally we know some split families like the Kreutz and presumably SOHO comet groups.
Two of these comets disappeared completely and one comet (Shoemaker-Levy 9) was distroyed during his impact on Jupiter.
Currently we know two types of split comets from observations: comets, which split into few fragments, where the primary fragment remains permanent and a smaller secondary (and maybe tertiary) fragment can survive up to years (type A).
Type B comets split into many fragments which are short-lived and no primary body can be identified. In this case the parent body may become completely destroyed, as it was the case for D/1993 F2 (Shoemaker-Levy 9) and C/1999 S4 (LINEAR). Type A splitting events can re-occur for the same object.
The significance of splitting phenomena on the evolution of comets has not been investigated very much. The splitting rate for short-period comets can be estimated to ~0.03/century/object, thus repeatedly splitting events can play an important mass-loss factor within the lifetime of a short-period comet. 
Different scenarios are used to explain the splitting of cometary nuclei:
tidal splitting, rotational splitting, splitting by thermal stress, 
splitting by internal gas pressure and impact-induced splitting are proposed mechanisms. 
At least for comet Shoemaker-Levy 9 we know for sure that tidal forces caused his disruption.
Because the internal structure of comets (in general and for most individual comets) is
not well known (if at all) and the existing observational data do not represent the real break-up event, all these models are more or less appropriate. Thus, at present, we cannot really answer the question 'Why and how do comets split ?'.
Most of the current observational data begin to track the seperation process typically weeks after the fragmentation. Activity outbursts and so-called coma arc-lets can indicate a possible upcoming break-up event in the nucleus.
High resolution monitoring of comets which show such secondary effects may provide us with data, which are closer to the real break-up moment.

- General reference: H. Boehnhardt, Split Comets. To be appeared in COMETS II.




Mark R. Kidger, Fabiola Martín-Luis

Instituto de Astrofísica de Canarias

To date sizes have been measured directly for only two comets: 1P/Halley and 19P/Borrelly, both in space probe encounters. To date the sizes of non-periodic comet nuclei have only been inferred from indirect measurements with large uncertainties. In the case of C/1995 O1 (Hale-Bopp), for example, the range of diameters estimated by different techniques ranges from under 30km to approximately 130km. However, the technique of measuring the albedo through visible and mid-infrared observations of the inert nucleus offers the possibility of making accurate determinations of both albedo and effective radius. To date such techniques have not been applicable because of the lack of instrumentation of suitable sensitivity to detect bare nuclei at large heliocentric distances. This situation is now changing as various mid-infrared imagers with high sensitivity will be available on large telescopes. In particular, CanariCam the mid-infrared imager of the Gran Telescopio CANARIAS, which is due to start scientific operations in 2005, is capable of detecting bare nuclei at very large heliocentric distances. In the case of C/1995 O1 (Hale-Bopp) the estimated flux would be 90mJy at r=17AU compared to a limiting flux of 0.9mJy for a 5s detection in 100s. Thus we could detect nuclei as small as a third of the diameter of Hale-Bopp in a few hours even at 17AU. The mid-infrared observations can be combined with visible and near-infrared data from the telescopes at Teide Observatory to measure exact albedos and effective radii for a sample of non-periodic comets thus permitting for the first time a statistical study of their properties.



Mark R. Kidger, Fabiola Martín-Luis  

Instituto de Astrofísica de Canarias

CanariCam the mid-infrared imager of the Gran Telescopio CANARIAS, will have many applications for the study of solar system bodies, in particular comets, NEOs and vulcanism on Io. In particular, it will offer Spanish solar system scientists and planetary geologists a series of exciting research options that have previously not been available to them. We present a brief description of the instrument and its applications.



Fernanda Artigue  

Observatorio de los Molinos, Uruguay

Mark R. Kidger & Fabiola Martín-Luis

Instituto de Astrofísica de Canarias

We report the results of three-colour photometry of 67P/Churyumov-Gerasimenko in BVR taken with the 82-cm IAC-80 Telescope at Teide Observatory (Tenerife) and with the 1-m Jacobus Kapteyn Telescope at the Roque de los Muchachos Observatory (La Palma) during March and April 2003. The comet showed a strongly condensed aspect with an almost stellar nucleus in a more extended coma and a tail that extends out of the 7.1 arcminute field of the IAC-80 Telescope. We present colour maps of the coma taken with deep exposures and an analysis of the coma profile and morphology.  


                                          FROM  SIERRA NEVADA OBSERVATORY                    

Jose L. Ortiz, V. Casanova, A. Sota

Instituto de Astrofísica de Andalucía, CSIC, Granada, Spain

The study of the rotational variability in large Trans Neptunian Objects (TNOs) and Centaurs is important because it provides a means of obtainining valuable information on a number of basic properties which are extremely useful for our understanding of the Kuiper Belt and for the understanding of the formation and evolution of the solar system. Since 2000, long observing runs devoted to the study of the photometric variability of TNOs and Centaurs are scheduled regularly at Sierra Nevada Observatory using its 1.5m telescope equipped with a fast read-out 1024x1024 CCD camera.  We present a compilation of recent results on the largest bodies that have been observed, and some statistics concerning the range of variability, which appears to be larger than that of the main belt asteroids of similar large sizes. Since the large bodies are not collisionally evolved, this result seems to be an important feature of the primordial distribution, which is different for TNOs when compared to main belt asteroids.



                                               Pasquale Tricarico

                      Physics Department, Padova University, Padova, Italy

Orbit Reconstruction, Simulation, and Analysis (ORSA) is a C++ framework for the development of algorithms oriented to the simulation and analysis of the orbital evolution of bodies in space.
The main goals of the project are the implementation of state of the art orbit integration algorithms, with concerns on accuracy and performance, and the development of a number of analysis tools. Commandline and graphical interfaces are also provided.
In the presentation, will be presented the principal characteristics
of the project and the results obtained.


                                     SATURN TROJANS PREDICTOR

                                 Pasquale Tricarico, Francesco Marzari

                      Physics Department, Padova University, Padova, Italy

We propose a method for the prediction of observational regions candidate to the discovery of Saturn Trojans which makes use ofthe Frequency Map Analysis. Thanks to a deep analysis of the forced and proper elements of a set of virtual Saturn Trojans,
the stability regions in the space of the proper elements can be spotted at different inclinations. After the conversion from proper elements to osculating elements, the observational regions in the RA/DEC system can be obtained at any epoch. We also plan
to build a website with ephemeris and other services spotting the most probable RA/DEC regions with stable Saturn Trojans.