Speakers
Description
At a time when the number of satellites in orbit is increasing and with the rise of mega-constellations, ensuring effective satellite end-of-life (EOL) operations has become crucial. However, these operations can often be challenging due to need of consecutive manoeuvres and continuous satellite monitoring. In addition, there may be periods of missing data and manoeuvres may contain inaccuracies that require real time re-calculation. Therefore, data collection from different sources and its early processing becomes essential to support those end-of-life operations. This presentation aims at providing a description of real end-of-life operations supported with an optical data sensor network and orbit determination service.
This optical data and orbit determination service consists in the regular and on-demand observation of the entire EUMETSAT fleet of GEO satellites, providing both optical tracking data and estimated ephemeris, which allows EUMETSAT to enhance the orbit estimation with an additional and alternative source of data, and to deal with particular operations, such as manoeuvres, or contingency situations with safety and higher confidence. Furthermore, the service provides additional support for special campaigns, such as calibration of ranging stations, Launch and Early Orbit Phase (LEOP) and also end-of-life operations.
The service is currently provided for the MSG-2 (Meteosat 9), MSG-3 (Meteosat 10), MSG-4 (Meteosat 11) and MTG-I1 (Meteosat 12) satellites, the latter since December 2022. However, until the end of its operations, the service was also provided to MSG-1 (Meteosat 8). During MSG1 end-of-life operations it was possible to prove that very valuable support can be provided with this optical service and orbit determination service.
During these end-of-life operations in GEO, the semi-major axis (SMA) is normally increased at least 300km, while maintaining a low eccentricity, which is achieved through a series of manoeuvres, generally 2 per day. In this situation, it has been shown that optical data from telescopes is useful to complement ranging data from GEO ranging stations, for the potential loss of coverage from a ranging station due to the satellite drift when increasing the SMA, for contingency situations or for final orbit estimation once the satellite is fully passivated.
In fact, the usefulness of the service was evident during the end-of-life campaign of MSG-1, in October 2022, during which optical data was provided by 3 telescopes, and up to 12 manoeuvres during a 6-days period were estimated, including a last observation phase after the passivation of the satellite.
Not everything has been an easy path, as the campaign also served to understand the challenges associated to this support. For example, it is not always possible to observe between maneuvers due to unfavorable illumination conditions, which can lead to greater uncertainty in orbital information and, consequently, in the telescope pointing. In addition, having many consecutive maneuvers without the satellite in free-flight does not allow for an improved orbit determination. Finally, adverse weather conditions require telescope redundancy from different locations. On the other hand, this campaign allowed also to analyse the possible extension of the service with additional functionalities based on the exploitation, for instance, of telescope light-curves to perform rotational analysis and attitude estimation.
In conclusion, this presentation describes how an optical data provision and orbit determination service can support end-of-life operations. In particular, it showcases how such support was provided for the real case of EUMETSAT's MSG-1 end-of-life operations, and it provides a summary of the data and main results obtained during that campaign. Furthermore, it analyzes the lessons learned from supporting such cases and raises the possibility of extending the support with analysis of light-curves.
