Planning the operations for sentinel-1 satellite: How to fit a complex puzzle

Abstract

The Sentinel-1 mission is an initiative of Europe's Global Monitoring for Environment and Security, GMES (now named COPERNICUS) program. Its main objective is to provide operational data with the purpose of monitoring several aspects of the sea and land surface, ensuring the continuity with the earlier ERS and Envisat missions. The design of the Sentinel-1 mission, with its focus on reliability, operational stability, global coverage, consistent operations and quick data delivery, is expected to enable the development of new applications and to meet the evolving needs of GMES. The Sentinel-1 mission is composed by two satellites: S1A and S1B. S1A is expected to be launched in early 2014. S1B will be launched a few years later. In the scope of the Sentinel-1 program, the Mission Planning subsystem is part of the Payload Data Ground Segment (PDGS) and has been deployed at ESA's establishment in Frascati (Italy). GMV was awarded in 2010 with the contract for the development of the Mission Planning subsystem with Airbus Defence & Space, ESA's prime contractor for the Sentinel-1 PDGS. The current, accepted version of the Mission Planning subsystem is to be used during the launch campaign of the Sentinel-1 A satellite. The Mission Planning subsystem is in charge of generating the plan of activities for the payload and also for the data downlink. It must provide effective solutions to data provision in terms of revisit frequency, coverage, timeliness and reliability. Due to the nature of the design of the Sentinel-1 satellites, where the autonomy of the satellites is a main driver, the mission plans must be adapted to this philosophy. This fact also has an impact on the scheduling of the on-ground activities. Some of the key activities of the Mission Planning subsystem are: • Perform the on-board memory management of the sensing data in order to optimize its usage. The Sentinel-1 Mass Memory is a complex device that offers multiple configuration options. The correct and optimal usage of such device is a key point of the planning problem. • To grant the reception and processing of the sensing data in order to meet its strict delivery requirements to the users. • To optimize the usage of the Ground Stations network in order to provide the image data to the users at the required time. • To insert in the plan as many user requests for sensing data as possible. • To plan imagery in tandem for both satellites that constitute the Sentinel-1 constellation • To update the plan in case that sensing requests are received at the last moment To be able to use, as far as possible, the autonomous capacity that the satellite design allows. • To provide the capability to insert user requests through its dedicated HMI in order to generate plans autonomously Moreover, the Mission Planning subsystem must be flexible enough to meet the requirements needed by the different envisaged scenarios, where only one of the two satellites are in operations and where both satellites are operational. Also, the capability to modify the acquisition ground stations scenario must be provided in order to register or unregister Ground Stations while avoiding further modifications in the system. In order to fulfill the flexibility requirements, the usage of an Expert System has been required for implementing a soft algorithm logic as the planning engine. With this technique it is possible to modify the way that the planning of the tasks is performed without stopping the system and applying these modifications next time that a plan is generated. The purpose of this paper is twofold: • To describe the operational concept for the creation of the mission plans for the Sentinel-1 constellation: the innovative autonomous concept for the Sentinel-1 satellite design drives the way that the operations plans are created. A new concept of operations has been introduced as consequence of this. • To present the solutions that have been applied to the planning problems that the Sentinel-1 Mission Planning must face.