FROM SIMULATION TO REALITY: CATALOGUING OF OBJECTS FROM GROUND-BASED OPTICAL OBSERVATIONS Ra´

This paper presents the approach for building a catalogue of Earthorbiting objects from optical observations in surveillance mode. The cataloguing is based on the DEIMOS CORTO tool (CORrelation Tool) which is described in this paper. CORTO has evolved from a simulated cataloguing system to a cataloguing software suite intended to process data from real observations. Thus, it merges the knowledge derived from simulation experience and the main constraints imposed by real observation activities. The main differences among these two approaches are highlighted in the paper. CORTO processes observations from several sensors in a sequential way. For each incoming observation, it attempts to correlate it to an existing object in the catalogue. If such correlation is possible, an orbit determination process is performed on the incoming measurement in the basis of a-priori state vector and covariance of the object. If such correlation is not possible, an initial orbit determination is carried out, and a new object associated to that measurement is created. CORTO allows a cold start of the cataloguing (i.e, it does not need any external catalogue to start) and thus, can maintain orbital information of object not included in public TLE file. The main results from DEIMOS cataloguing experience are summarised, describing the observation strategy and the measurement distribution considered necessary for achieving a proper cataloguing capability. This summary highlights the main difficulties that can be found, in the correlation activities which impose a several-step approach to correlation in order to avoid miss-correlation of objects. The approach undertaken in the CORTO software is based on a three step process: firstly, a correlation in the basis of comparison of observation with expected visibility periods and rough observation angles is carried out for every object. A second orbit determination compatibility cross-check based on the filtering residuals is performed later. Finally, a procedure for removing false objects (i.e, objects created by spurious measurements), and/or to remove objects which are observed sparsely is performed asynchronously. The system is intended to run in a mostly automated way, but allows an operator to assess the correlations performed automatically by the system, and to correct them if necessary. In addition to this, it is possible to correct errors related to manoeuvring objects. If the operator knows with certainty that a manoeuvre has taken place, information regarding that manoeuvre can be loaded into the catalogue. The operator can also infer when an impulsive manoeuvre has happened with support from the system. Finally, the system allows the user to perform an iterative process in order to estimate the area-to-mass ratios associated to each of the objects in the catalogue. The CORTO cataloguing system is accompanied by a set of auxiliary tools, also described in the paper, which complete the capabilities of the system to ensure the proper cataloguing process. These tools include: CALMA for calibration of observation stations (used to qualify a number of observatories), CORTOEditor, to support operator for operational maintenance of the catalogue, and CHOCO which optionally allows correlating the observed objects with the TLE data. This tool serves to assign the international ID to the CORTO objects, but is not mandatory for successful correlation of objects within CORTO. The catalogue is finally made available through a restricted web system (CAWEB) that supports the monitoring of the catalogue. The paper presents the main results from an observational campaign executed in October 2014 focused on the cataloguing of high altitude objects. The campaign lasted 9 consecutive observing nights, providing more than 200.000 observations from three surveillance and a tracking telescopes located in Spain. Those observations are used to feed-up the CORTO cataloguing system, and have allowed creating a catalogue of objects which are observable from southern Europe. In particular GEO ring longitudes covering Europe are well represented. About 300 objects are systematically observed during several nights, eventually reaching accurate orbits. The achievable accuracy of the observed orbits can reach values around 10-100 meters. Object manoeuvres are also observable. Example cases of observed manoeuvres are reported.