SLE experience over unreliable network links

Kurzfassung

Despite the great advances of technology in networking areas, space missions sometimes face difficulties to achieve a successful operational state when high reliability data links are not available between their control centres and the ground stations, causing loss of data and disconnections. The reasons are varied, from time and cost constraints to design and implementation restrictions, as well as additional limitations imposed by the Mission Control System (MCS). The objective of this paper is to share the experience gained at different stages of past spacecraft missions where CCSDS Space Link Extension services were not offered in the initial design, to present the solutions found to mitigate the data losses and to illustrate the positive impact to the overall mission following the implementation of CCSDS SLE services. Comparisons between different ground protocols, used extensively in space operations, to transport telemetry at higher data rates in real time between remote ground stations and control centres, and appropriate parameter fine-tuning that led to improved data delivery reliability are taken into consideration as well. This paper presents the operational success of the deployment of the SLE protocol to overcome the difficulties caused by the specified restrictions and limitations. The result of this analysis, or just parts of it, could be useful to space agencies in planning and designing their future missions in an optimal manner with respect to the ground network design and costs.