PHILAE: Science scheduling and unknown context. leassons learned

Rosetta is an ambitious mission launched in March 2004 to study the nucleus as well as the coma of the comet 67P/Churyumov-Gerasimenko. It is composed of a space probe and the Philae Lander. The mission is a series of premieres: among others, first probe to escort a comet, first time a landing site is selected with a so short notice, first time a lander has landed on a comet nucleus. The space probe Rosetta reached the vicinity of the comet in spring 2014 when it has started to study Churyumov-Gerasimenko with remote sensing instruments. An intense observation phase followed to be able to select a landing site for the Lander. And in November 2014, at a distance of about 3 AU from the sun, Philae has reached its destination on the surface of the comet 67P. Once stabilized on the comet, the lander has performed its “First Science sequence”. Philae’s aim was to perform detailed and innovative in-situ experiments on the comet’s surface to characterize the nucleus by performing mechanical, chemical and physical investigations on the comet surface. The main contribution to the Rosetta lander by the French space agency (CNES) is the Science Operation and Navigation Centre (SONC) located in Toulouse. Among its tasks is the scheduling of the scientific activities of the 10 lander experiments and then to provide it to the Lander Control Centre (LCC) located in DLR Cologne. Nevertheless, the specific context of the Rosetta mission made this task even more complex if compared to usual spacecraft or landers: indeed the teams in charge of the Philae activity scheduling had to cope with huge constraints in term of energy, data management, asynchronous processes and co-activities or exclusions between instruments. In addition to these huge constraints it is important to note that the comet, its environment and the landing conditions remained unknown until the separation time and that the landing site was selected a short time before it had to take place and when the baseline operational sequence was already designed. This paper will explain the specific context of the Rosetta lander mission and all the constraints that the activity scheduling had to face to fulfil the scientific objectives specified for Philae. A specific tool was developed by CNES and used to design the complete sequence of activities on the comet with respect to all constraints. The baseline scenario designed this way will also be detailed to highlight the difficulties and challenges that the operational team had to face. A specific focus will be given on the landing site selection and the impacts on the scientific operations scheduling. Moreover the actual sequence performed on the comet will also be detailed and analysed to deduce the lessons that could be learned from such an unprecedented endeavour. Indeed as for every mission of exploration the flexibility concept was anticipated but had to face unexpected events

The Philae Lander: Science planning and operations

Rosetta is an ambitious mission launched in March 2004 to study comet 67P/Churyumov–Gerasimenko. It is composed of a space probe (Rosetta) and the Philae Lander. The mission is a series of premieres: among others, first probe to escort a comet, first time a landing site is selected with short turnaround time, first time a lander has landed on a comet nucleus. In November 2014, once stabilized on the comet, Philae has performed its “First Science Sequence”. Philae’s aim was to perform detailed and innovative in-situ experi- ments on the comet’s surface to characterize the nucleus by performing mechanical, chemical and physical investigations on the comet surface. The main contribution to the Rosetta lander by the French space agency (CNES) is the Science Operation and Navigation Center (SONC) located in Toulouse. Among its tasks is the scheduling of the scientific activities of the 10 lander experiments and then to provide it to the Lander Control Center (LCC) located in DLR Cologne. The teams in charge of the Philae activity scheduling had to cope with considerable constraints in term of energy, data management, asynchronous processes and co-activities or exclusions between instruments. Moreover the comet itself, its environment and the landing conditions remained unknown until separation time. The landing site was selected once the operational sequence was already designed. This paper will explain the specific context of the Rosetta lander mission and all the constraints that the lander activity scheduling had to face to fulfill the scientific objectives specified for Philae. A specific tool was developed by CNES and used to design the complete sequence of activities on the comet with respect to all constraints. The baseline scenario for the lander operation will also be detailed as well as the sequence performed on the comet to highlight the difficulties and challenges that the operational team faced

Rosetta Lander - After seven years of cruise, prepared for hibernation

Rosetta is a Cornerstone Mission of the ESA Horizon 2000 programme. It is going to rendezvous with comet 67P/ Churyumov–Gerasimenko after a 10 year cruise and will study both its nucleus and coma with an orbiting spacecraft and a landed platform. The latter, named Philae, has been designed to land softly on the comet nucleus and is equipped with 10 scientific instruments to perform in-situ studies of the cometary material. Philae has been provided by a large international consortium. Rosetta was successfully launched on March 2, 2004 from Kourou in French Guyana. Philae is operated by the Lander Control Centre (LCC) at DLR, Cologne and the Science Operations and Navigation Centre (SONC) at CNES, Toulouse via the European Spacecraft Operations Centre (ESOC) in Darmstadt. The scientific lead is at the Max Planck Institute for Solar System Science (Katlenburg-Lindau, Germany) and the Institut d’Astrophysique Spatiale (Paris). Since launch, the Lander has been operational during commissioning, several checkouts, two planetary swing-bys at the Earth and one at Mars, fly-bys at asteroids Sˇ teins and Lutetia as well as some additional activities for calibration and failure investigation. Payload checkout PC13 was the last Lander activation prior to a deep space hibernation phase of Rosetta, which started in June 2011 and will last until approaching the comet in 2014. The paper describes the various Lander activities over the past seven years and gives an outlook of near- and on-comet operations. Landing is foreseen in November 2014 at a heliocentric distance of 3 AU. Prior to that, detailed characterization of the comet nucleus has to be performed with the Rosetta Orbiter instruments

The CONSERT operations planning process for the Rosetta mission

The COmet Nucleus Sounding Experiment by Radio wave Transmission (CONSERT / Rosetta) has been designed to sound the interior of the comet 67P/Churyumov-Gerasimenko. This instrument consists of two parts: one onboard Rosetta and the other one onboard Philae. A good CONSERT science measurement sequence requires joint operations of both spacecrafts in a relevant geometry. The geometric constraints to be fulfilled involve the position and the orientation of both Rosetta and Philae. At the moment of planning the post-landing and long-term science operations for Rosetta instruments, the actual comet shape and the landing location remained largely unknown. In addition, the necessity of combining operations of Rosetta spacecraft and Philae spacecraft makes the planning process for CON- SERT particularly complex. In this paper, we present the specific methods and tools we developed, in close collaboration with the mission and the science operation teams for both Rosetta and Philae, to identify, rank and plan the operations for CONSERT science measurements. The presented methods could be applied to other missions involving joint operations between two platforms, on a complex shaped object

The CONSERT operations planning process for the Rosetta mission

In the scope of European Space Agency's Rosetta mission, the COmet Nucleus Sounding Experiment by Radio wave Transmission (CONSERT) has sounded the deep interior of the nucleus of comet 67P/Churyumov-Gerasimenko. The CONSERT experiment main objective was to image the interior of the comet nucleus. This bi-static radar experiment with instrument units on-board both, the Rosetta main spacecraft and its lander Philae, requires a specific geometric configuration to operate and produce fruitful science data. Thus, these geometric constraints involve mainly the position and orientation of Rosetta and Philae. From the operations planning point of view, the mission constraints imposed observation slots to be defined far before their execution, while the comet shape, spacecraft trajectories and landing site were still unknown. The CONSERT instrument operations scheduling had to be designed jointly for Rosetta and Philae platforms, based on different time scales and planning concepts. We present the methods and tools we developed to cope with the complexity of this planning process. These operations planning concepts allowed handling the complexity of multiple platform operations and the lack of prior knowledge of the observed target