Mission Planning and Operational Constraints and Their Resolution for EO Missions Like EnMAP

Abstract

Earth observation missions are generally operated by execution of predefined timetagged commands. However, depending on the type of mission, issues relevant to different types of mission may occur. These issues are drivers for the design of the operations system of EnMAP (Environmental Mapping and Analysis Program). The main challenges are limited transfer of telecommands and limited downlink capabilities; also the cloud coverage in the target area -for optical sensors -plays a huge role.There are certain constraints, concerning this satellite bus in particular. For example a limited time tagged list which allows no more than 120 time tagged commands on board. Further the fact that every dumped house keeping packet has to be requested from the space craft which leads to a delay in the reception of telemetry can be a bottle neck. In addition to these S-band related issues it is a real challenge to coordinate the amount of payload data which will be down-linked via X-band. In this paper the strategy of managing all these difficulties and optimally operating the satellite under these conditions, will be described.For handling of cloud coverage a database with weather statistics will be implemented. These statistics are compared with global forecast models as provided by e.g. the German weather service (DWD). With the calculated forecast values, planning priority of datatakes is increased or decreased.

The EnMAP Mission Planning System

“…The design of the EnMAP MPS largely builds on our experience gathered during the TerraSAR-X/TanDEM-X mission [16] and has been developed further. Parts of a preliminary EnMAP MPS design have already been described by [17]; however, it has also evolved significantly since then -most importantly through incorporating the most recent Mission Planning technologies in the context of an intermediate critical design review (so-called ∆CDR) of the EnMAP ground segment in 2016.…”

“…EnMAP will perform Earth observations in the visible and near infrared (VNIR) as well as shortwave infrared (SWIR) part of the electromagnetic spectrum. Clouds in the acquired scenes are thus expected to reduce the area that is useful for scientific applications by more than 50% [17,22]. However, there are two potential counter measures against wasting satellite resources for largely obstructed observations: Onboard cloud detection to discard affected scenes before downlink (e. g. [23] in the context of EnMAP) or prioritizing acquisitions with favorable cloud forecasts already on-ground (e. g. in use for Landsat 7 [22] or CHRIS-PROBA [24]).…”

“…* The limited onboard buffer of 120 time-tagged commands is a rather unusual characteristic of the EnMAP mission; for a more detailed discussion in the context of the EnMAP MPS, see[17].…”

The EnMAP Mission Planning System

“…Parts of a preliminary EnMAP MPS design have already been described by [17]; however, it has also evolved significantly since then -most importantly through incorporating the most recent Mission Planning technologies in the context of an intermediate critical design review (so-called ∆CDR) of the EnMAP ground segment in 2016.…”

“…Clouds in the acquired scenes are thus expected to reduce the area that is useful for scientific applications by more than 50% [17,22]. However, there are two potential counter measures against wasting satellite resources for largely obstructed observations: Onboard cloud detection to discard affected scenes before downlink (e. g. [23] in the context of EnMAP) or prioritizing acquisitions with favorable cloud forecasts already on-ground (e. g. in use for Landsat 7 [22] or CHRIS-PROBA [24]).…”