EUROPEAN SPACE AGENCY
EUROPEAN SPACE OPERATIONS CENTRE
GROUND SYSTEMS ENGINEERING DEPARTMENT
Mission Analysis Office
CLASSIFICATION OF GEOSYNCHRONOUS OBJECTS
by J.P. Arregui and R. Jehn
Produced with the DISCOS Database
ESOC Robert-Bosch-Str. 5, 64293 Darmstadt, Germany
All objects near the geostationary ring which are catalogued in ESA's DISCOS Database (Database and Information System Characterising Objects in Space) are listed in this document. The main purpose is to classify all these objects according to different categories. Indeed, six different types of categories are defined:
- C1: objects under longitude and inclination control (E-W as well as N-S control) - the longitude is
nearly constant and the inclination is smaller than 0.3 degrees,
- C2: objects under longitude control (only E-W control) - the longitude is nearly constant but the
inclination is higher than 0.3 degrees,
- D: objects in a drift orbit,
- L1: objects in a libration orbit around the Eastern stable point (longitude 75 degrees East),
- L2: objects in a libration orbit around the Western stable point (longitude 105 degrees West),
- L3: objects in a libration orbit around both stable points.
All objects are selected from ESA's DISCOS Database according to the following criteria:
- eccentricity smaller than 0.1
- mean motion between 0.9 and 1.1 revolution per sidereal day, corresponding approximately to a
semi-major axis of 42164 ± 2800 km
- inclination lower than 20 degrees
The basic source of information are the NASA Two-Line Elements (TLE). The DISCOS Database is updated at regular intervals by ESOC's Mission Analysis Office (on average 1 TLE per week and per object is stored). As the data are determined by passive sensors, their accuracy is limited. At the geostationary altitude, only objects larger than about 1 m in size are tracked on a regular basis. The main information given by this catalogue is the classification of the objects according to their type of motion. It should be noted that also some of the derived parameters like libration period and libration amplitude may sometimes have a limited accuracy. For further information about the method of classification please refer to Classification of geostationary objects, (Ref. 1).
This document contains three tables:
- Table 1 contains objects with recently updated orbital elements. They are ordered according to
their type of motion and some orbital information is given.
- Table 2 contains objects for which there were no TLEs available during the last 6 months. The
classification of objects for which no TLEs are available at all is following the classification made
by Vladimir Agapov, Keldysh Institute for Applied Mathematics, Moscow (KIAM), supported by
Space Informatics and Analytical Systems, Moscow, Russia.
- Table 3 contains all the objects the status of which cannot be determined by our software. The
main reason for the difficulty to classify an object is that there are not enough TLEs available or
that the status has recently changed (satellite newly launched or recently manoeuvred).
In order to find a specific object in one of the three tables, there is a list of all objects in ascending order of their COSPAR identification in Chapter 2.