Maria Theresia Wörle

The Algorithm Assembly Set of Plato

Driven by the requirements of earth observing satellite missions, the mission planning team of the German Space Operations Center (GSOC) has improved its scheduling engine to allow automated timeline generation for multiple interacting satellites. Whereas the past work included extensions of the modeling language and improvements on the performance, current work focusses on the algorithm framework. In order to allow future missions’ scheduling software to reuse generic algorithms, special attention is given to the way one can add new sub-algorithms and combine them with existing ones. This ePoster demonstrates the algorithm framework of GSOC’s mission planning software Plato, using its interactive GUI Pinta. Based upon a typical multiple satellite planning problem, a priority based generic algorithm is presented, which solves this problem. We show how this algorithm can be split up into small subalgorithms, each of which can be used separately and all of which can be combined in arbitrary ways. We demonstrate how this flexibility can be used to create modifications on the overall algorithm or include mission specific sub-algorithms. Although all presented algorithms are based on simple heuristics, this mechanism supplies a straight forward way to incorporate more sophisticated optimization algorithms. The techniques demonstrated in this paper will be shown by means of the OnCall planning project. This project is used by GSOC in order to schedule the on-call shift times of its staff in order to implement 24/7 support for all important satellite sub-systems.

Mission Planning System for the TET-1 OnOrbitVerification Mission

The TET-1 satellite was launched on July 22nd, 2012, to test and demonstrate the space readiness of new hardware components. Eleven experiments are running in space since then. The mission planning system (MPS) that provides the TET-1 satellite with its tele-command timelines during the OnOrbitVerification (OOV) phase is presented: Based on a strategic one-year experiment plan provided in advance by an external industry partner, MPS collects all relevant information necessary to build a sequence of flight procedures, called timeline, for a time range of roughly a week, on a day-by-day basis. In contrast to the TerraSAR-X/TanDEM-X MPS or the Incremental Planning System, where several software components convert incoming orders into commandable files, a slim set of tools was decided to be used for the TET-1 mission, combined in PINTA (Program for INteractive Timeline Analysis). Necessary data was imported using the plug-in mechanism of PINTA that uses interfaces to several partners. Having all information available, scheduling itself was done by running the planning algorithms provided by Plato, GSOCs generic library for modeling and solving planning problems. An assembly of various planning algorithms, individually configurable and referencing one another, creates the necessary timeline entries of flight procedures. Due to the high flexibility of the planning system it was possible to support various changes in the pre-planned onboard timeline on short notice. Additionally, an outlook on further extensions of the current MPS is given, that enables even more flexibility in terms of data acquisition and are relevant for the upcoming FireBIRD mission, which includes the TET-1 spacecraft after the OOV operations phase.

Onboard Planning and Scheduling Autonomy withinthe Scope of the FireBird Mission

For most low orbiting earth observation satellite missions, the timeline is generated on- ground and during dedicated uplink sessions the corresponding tele-commands are sent to the spacecraft. Bene�ts of this approach are easy maintainability of the complex planning software and quick response times to customer input. However this approach has two major drawbacks: On the one hand the spacecraft behavior is not completely predictable in terms of constraining resources, which means that even detailed modeling requires margins for the on-board resources within the on-ground scheduling algorithms. On the other hand, the reaction time to onboard detected events includes at least the two upcoming ground station contacts, since data downlink and evaluation, (re-)planning and tele-command uplink have to be awaited before the spacecraft can perform new activities. This paper describes the �nal design and use cases of VAMOS, an experiment of DLR/GSOC, which will be part of the FireBird mission. VAMOS consists of a combined onboard / on-ground planning system, which resolves the above mentioned drawbacks by supplying limited onboard autonomy to the satellite, retaining the bene�ts of a ground based planning system as far as possible.

VAMOS – Verification of Autonomous Mission Planning On-board a Spacecraft

For typical ground based mission planning systems for low earth satellite missions one major drawback can be detected: The reaction time to on-board-detected events, which includes at least two ground station contacts. To correct this, the DLR/GSOC invented VAMOS, which is an autonomous concept of minimized on-board complexity which allows on-board reaction to telemetry measurements and event detection. This experiment will be part of the FireBIRD mission and verify the gain when mission planning autonomy is transferred to the spacecraft up to some extent. This paper presents the outcome of the design phase under the given constraints. In order to minimize risks and computational effort on-board, a solution has been chosen that demands relatively simple tasks of the on-board autonomy but nevertheless will lead to maximizing the mission output and on the other hand takes care of all potentially to be considered resource constraints.

The Incremental Planning System—GSOC's Next- Generation Mission Planning Framework

The paper at hand presents the new generic framework for automated planning and scheduling in future mission planning systems developed at GSOC (German Space Operations Center). It evolved from the experiences made in past and current projects and the evaluation of internal and external requirements for upcoming projects. In customary systems such as the one used within GSOC’s TerraSAR-X/TanDEM-X mission, succeeding planning runs to combine all collected input to a consistent, conflict-free command timeline take place at fix, dedicated points in time, e.g. twice a day. In contrast and as a main difference, with the new system each new input is processed immediately and so a consistent up-to-date timeline is maintained at all times. We show that this approach provides a set of important advantages and new possibilities for spacecraft commanding and user satisfaction. For example, uplink schedules can be flexibly modified due to short-term notifications, or up-to-date, extensive information about the planning state is always available, which means that conflicts can be seen before finally submitting a new request and, if applicable, can be resolved by selecting a suggested solution scenario. The presented system constitutes a generic tool suite which is scalable in performance critical areas, which is configurable to various mission scenarios and which defines a dedicated set of interfaces, specifying the functionality that remains to be implemented by each individual project. The declared goal is that all upcoming GSOC missions will benefit from using the Incremental Planning framework in terms of cost reduction, implementation duration and system robustness.

The TerraSAR-X/TanDEM-X Mission Planning System: Realizing new Customer Visions by Applying new Upgrade Strategies

The history of the TerraSAR-X and TanDEM-X mission planning system is briefly presented. In addition to the not trivial demands of the first years, special attention is given to the challenges of recent years. Here the TanDEM-X science phase, conducted between 2014 and 2016, is the most prominent feature. It is shown how agile software engineering methods can help to keep the already achieved system robustness, and how further enhancements can easily be incorporated.

The Mission Planning System for the Firebird Spacecraft Constellation

The Firebird mission comprises the two spacecraft TET (launched July 22nd 2012) and BIROS (launch foreseen for May 25th 2016), both carrying a combined infrared-optical camera system as primary payload as well as several additional hard- and software experiments. Our Mission Planning team at the German Space Operations Center (GSOC) is responsible for generating conflict-free timelines for commanding payload and so-called background sequence operations for both spacecraft in accordance with all given spacecraft and ground-related constraints and customer requirements. Therefore, a Mission Planning system has been prepared and is continuously developed further with continuously changing space segment capabilities throughout the different project phases. The paper at hand describes the main components and their set-up, e.g. the semi-automated planning tools and the newly implemented interactive order interface for the customers. Furthermore, the decision to which extent a combined system is set up for both spacecraft as well as the advantages of being able to rely on a generic, configurable tool suite, modeling language and scheduling algorithm assembly are discussed.

GSOC SoE-Editor 2.0 - A Generic Sequence of Events Tool

At the German Space Operations Center (GSOC) two applications had been developed for scheduling operations of Launch and Early Orbit Phases (LEOP), Commissioning Phases or special operations campaigns (e.g. software upload, special orbit maneuvers, etc.): one for low earth orbit (LEO) and one for medium (MEO) and geostationary earth orbit (GEO). The experiences of these tools were now merged with the scheduling capabilities of GSOCs generic mission planning application Pinta (Program for interactive timeline analysis), its scheduling library Plato (Planning tool) and the GSOC web based timeline display TimOnWeb.

Operating and Evolving the EDRS Payload and Link Management System

Based on its Plato scheduling library, GSOC has developed the scheduling components for controlling the EDRS-A and EDRS-C payloads, called Link Management System. This paper reports on the operational experience gained from almost two years of EDRS-A operations and the improvements that have been made to the codebase. The necessary changes for EDRS-C are highlighted. Finally, thoughts and recommendations for future ground segment engineering are given.