EUNEASO, which stands for EUropean Near-Earth Asteroids Search Observatories, is a cooperation between European institutes working in the field of asteroid research to organize a large-scale NEO search programme. Our general policy is to use existing infrastructures and telescopes and install state-of-the-art CCD camera systems. In parallel to the search programme we build up the capability to perform continuous astrometric follow-up and physical observations of newly discovered and/or favourably approaching NEOs. - The project shall be seen as a (European) contribution to a global network of NEO (re)search programmes, and we are particularily emphasizing our efforts to establish effective and reliable communication links between the participating sites via internet and to standardize our software and data formats (of e.g. astrometric posistions, photometric lightcurve data, etc.).
For the search programme we are developing a CCD array camera system, based on 2k x 2k CCD chips, using a modular design, to build a mosaic covering about 5° x 1° of the sky in the focal plane of the 90cm OCA Schmidt telescope.
Most of the development work has been done at the OCA, where a prototype one-CCD system is being tested at the 90cm Schmidt at Caussols.
At the Institute of Planetary Exploration of the DLR in Berlin-Adlershof a full-fledged 9-CCD camera system (based on the OCA prototype) is under construction.
At the Astronomy Department of the University of Padua a large field CCD camera is under development. The acquisition of a commercially available SBIG ST-8 CCD camera is being considered for a test phase of the NEO search programme at the Asiago Schmidt telescope.
In addition to the CCD camera development at the OCA, experiments with scanning photographic films taken with a Schmidt telescope are currently performed. This technique, if proven successful, may be applied to NEO search on existing and newly exposed plates and/or films.
Computer programmes to allow the (automatic) detection of moving objects on a series of CCD frames are currently being developed at the OCA in cooperation with the DLR group.
We have developed a software dubbed GODS (Global Orbit Determination Software), which implements an optimized algorithm for automatic detection of moving objects. After a normal pre-processing step, the image is convolved with a DOG (difference of Gaussian) adaptative filter. A maxima detection precedes an image characterisation procedure (position and flux). Further operations on object catalogs are carried out with a combination of dynamic 2D range trees and Voronoi diagrams. Catalogs of observations of the same field taken at different times are matched to detect both reference stars and objetcs which have a linear motion. Pattern matching with stars from the HSR Guide Star Catalog allows astrometry. Final reduction outputs an IAU compatible ASCII form, and observed objects are kept in a database on the site. The software is in final test stage. We can detect asteroids up to magnitude V=19 with a precision of 0.05 arcsec. The filtering step takes 3 minutes for a 2048x2048 image on a HP9000/710 workstation. Operations on catalogs are instantaneous thanks to high-level data structures used.
For the first phase of the search programme we envisage at least two dedicated telescopes, one in the northern and one in the southern hemisphere. Currently, there is a proposal submitted to ESO to install a CCD array camera system at the 1m Schmidt telescope at La Silla, Chile, and a decision by ESO is expected later this spring.
As a northern site the 90cm Schmidt at Caussols, north of Nice in France, is being considered as a viable choice.
Another possibility is the use of the 67cm Schmidt telescope at Asiago, 90km north of Padua (Italy). At present the telescope is used for a programme devoted to a photographic search for asteroids. The site enjoys many nights of good weather, especially during fall and winter.
One important factor in sucessfully running a joint programme of discovery and follow-up of NEOs is the availability of a fast and reliable communication system between the various sites. We plan to establish a coordination centre which is linked via internet to the individual nodes. This allows to respond rapidly to interesting discoveries, and to optimize the use of observing time.
As part of this effort we have installed this WWW server to provide EARN, the European Asteroid Research Node and which is intended to facilitate the exchange of data and other information about both theoretical and observational asteroid research.
In order to follow-up new discoveries we are aiming at a series of geographically well distributed stations which can determine accurate astrometric positions to secure a reliable orbit for as many NEOs as possible.
As part of the photometric observation programmes carried out at different sites we have developed the capability to derive accurate astrometric positions from selected CCD frames, using the HST Guide Star Catalogue as a reference system. The software developed at Ondrejov and DLR allows interactive reduction shortly after having made an exposure, and computes positions in the format ready to be sent to the Minor Planet Center at Cambridge, Mass., for orbit determination.
These procedures are currently used on a routine basis at the Ondrejov Observatory (65cm reflector equipped with a SBIG ST-6 CCD camera in the primary focus) in the Czech Republic and at DLR, using the Bochum telescope (60cm reflector + CCD camera with 1k x 1k Tektronics chip) at ESO, Chile. This has allowed us to gain experience about the recovery and follow-up of NEOs, which will be used when the EUNEASO project will come into its operational phase.
During the last 14 months of activity at Ondrejov some 40 NEOs have been observed astrometrically, three have been actively recovered and seven new (mainbelt) asteroids have been discovered. At ESO, astrometric positions of some 20 asteroids (mainly NEOs) have been determined, of which five new discoveries, among them one NEO, 1995 FJ, (see figure 1).
Figure 1. Discovery CCD image of NEO 1995 FJ taken with the 60cm Bochum telescope at ESO on March 29, 1995, 08:15 UT, by S. Mottola. On the same frame the mainbelt asteroid 1995 FH was also discovered. This exposure was taken during a photometric study of NEO 1991 OA. The telescope was tracked to follow the motion of 1991 OA, and for this reason the field stars appear trailed. Due to their apparent motion the two discovered asteroids display trails in different directions.
To obtain information about the physical properties of NEOs already during the discovery apparition is one of the goals of our programme; since experience has shown that it might take many years until the next favourable apparition occurs.
Several groups within this project have been conducting for many years systematic observation programmes for physical studies of asteroids (photometry, colourimetry, spectroscopy) and often NEOs are included in these campaigns as targets of opportunity. This means observing techniques, reduction software and data analysis are well developed and can be used for dedicated studies of the large number of new NEO discoveries expected from the upcoming survey programmes.
In particular, the groups at the Institute of Planetary Exploration of the DLR in Berlin-Adlershof and at Ondrejov Observatory have developed an integrated CCD camera and image analysis system especially designed for lightcurve studies of asteroids. On-line reduction of the obtained lightcurve allows an estimate of the rotation period of an object so that its further observations can be performed to optimize the lightcurve coverage. This allows to observe several asteroids simultaneously, using the available telescope time in the most efficient way.
At Ondrejov, where the telescope is dedicated to NEO observations, some 30 NEOs have been observed photometrically. The DLR group determined new rotation periods for about 20 NEOs which have been observed as part of the ongoing photometry programme of asteroids (see figure 2).
Since the beginning of 1995 a cooperation with the Astronomical Observatory of the State University in Kharkiv, Ukraine has become effective. At the 70cm telescope at the observing station of Kharkiv observatory a SBIG ST-6 CCD camera system is being used in connection with the DLR data retrieval and analysis package to perform lightcurve measurements of asteroids, in particular NEOs.
Figure 2. Composite lightcurve of NEO (5836) 1993 MF derived from observations obtained by the DLR group with the 60cm Bochum telescope at ESO, Chile.