Staring At The Sun: Implementing the Remote Sensing Window Concept for Solar Orbiter

ESA’s Solar Orbiter mission, scheduled for launch in 2017, will enter into an elliptical orbit around the sun with a perihelion of 0.3 AU and an increasing inclination of up to 35°. Three ten-day “remote sensing windows” will be centred on the closest, most northern and most southern points of each 160-day orbit. During this remote sensing window, remote sensing instruments will peer through slots in the spacecraft’s heat shield to observe the evolution of solar features and will only see a small fraction of the solar disk. However, due to the difficulty of modelling the movement of these features, they can migrate out of the instrument’s field-of-view within about 3 days. It is therefore mandatory for Solar Orbiter to implement ground-based feature tracking as part of the science planning process. With groundand Earth-orbit based observatories not always able to observe the same part of the sun as Solar Orbiter, the instruments themselves will need to provide data which can be used by the science planning team to select and track the path of the features across the solar surface. A subset of “quick look” data will need to be defined which is sufficiently detailed to enable the analysis of the movement but also small enough to be downlinked completely in one ground station pass. The rapid processing by the science ground segment located at ESAC in Spain will be critical to turn this “quick look” data into data sets that can be analysed and form the basis of spacecraft pointing requests. Flight Dynamics will be required to check and convert these pointing requests into spacecraft commands forming a complete chain of attitude segments, one for each day of the science window, such that a complete and coherent guidance profile is always available to the spacecraft. Finally, the uplink to the spacecraft must be performed on a daily basis, in such a way as to minimise disruption to on-going science observations. Furthermore, there's the question of how this can actually be achieved operationally in a safe manner. What if a ground-station pass is lost? How do we prioritise the downlink of the quick look data? How do we uplink the new guidance profile safely? How do we transition from one guidance profile segment to the other in a smooth manner, that doesn't interrupt on-going observations? The remote sensing