ESA’s e.deorbit mission and its roadmap to Active Debris Removal
Since 2012, the European Space Agency (ESA) has studied a mission to perform Active Debris Removal (ADR) of a large space debris in low Earth orbit. The objective of the mission is to remove an ESA owned heavy debris from the 800 to 1000 km altitude near polar region. The removal is performed either by moving the target at high speed and high precision into the Earth’s atmosphere allowing the target to burn up due to aerothermal dynamic forces, or to move the target to a high altitude where the chance of collisions with other satellites is minimal. Several system studies have been performed, first internally in the form of pre-phase A studies done within ESA’s Concurrent Design Facility, and also phase A studies done by large satellite integrators contracted by ESA. Apart from the system studies, several technology development activities have started and some other are planned to start. In orbit testing may be required for several new technologies. All these activities together lead to a roadmap to a European capability to perform Active Debris Removal. Four questions will be answered: what the boundaries of e.deorbit? How is e.deorbit executed? How can we enable success? And what do we see when we re-assess e.deorbit on a regular basis? In terms of boundaries, e.deorbit and all technology development activities fall within ESA’s Clean Space initiative. With the Clean Space initiative, ESA will devote increasing attention to the environmental impacts of its activities, both on Earth and in space. A roadmap is created that brings the required technologies to a level where they are qualified through on-ground verifications by end of 2016. At the same time, the detailed design phase is scheduled such that a proposal can be prepared for the next Ministerial Council of 2016. The last boundaries are formed therefore by the stakeholders, consisting of the sponsors of all e.deorbit related activities, as well as active and passive stakeholders. E.deorbit is currently in detailed design phase. The execution of this phase focusses on consolidating all requirements for the implementation phase, which follows the System Requirements Review (SRR). The SRR marks the end of the first detailed design phase (B1). Envisat is the proposed space debris to serve as the target for ADR as it is ESA owned, in an 800 km altitude Sun Synchronous Orbit and of very high mass (8000 kg). Driving requirements are discussed in this paper, focussing on how the space element (e.deorbit) is affected by the launch element (launcher performance), ground element (the visibility of ground stations), target element (the unstable movement of the target and where to capture it), space environment element (in particular the safety requirements upon re-entry). The conceptual design phase focussed on three design options: 1) a robotic arm based solution that re-enters the target, 2) a flexible link based solution (capturing the target using a net or a harpoon) that re-enters the target, and 3) a robotic arm based solution that pushes the target to a high altitude (i.e. above the LEO protected zone as defined by ISO-standards). During the detailed design proposal phase, contractors were allowed to propose one preferred solution that re-enters the target, and focus the detailed design on this solution only. A strong focus on risk mitigation is pursued in the detailed design phase, while a cost ceiling for the e.deorbit platform was given. In order to enable success, a strong team work is pursued for e.deorbit. A concurrent design team at ESA, consisting of study manager, system engineers, cost and risk engineers and several specialists on subsystems that drive the design are working together to manage the work done by the contractors. Frequent communication with the contractors using video-conference connections are executed that allow for fast response to contractors questions and fast decision making. Several key-point meetings are put within the schedule, that each time narrows the amount of solution in order to refine better the preferred solutions. Finally, a motivation is noted within both the team working for e.deorbit as well as the public, as satellite collisions and re-entries are more and more in the news and even subject of Hollywood movies. There is a general movement (such as in the car industry) towards more sustainable solutions, and this raises sympathy for space- related sustainable solutions too. This is noted in the wide media coverage of e.deorbit and Clean Space related activities. Nevertheless, it is important to re-assess the status of e.deorbit on a regular bases and assess the risks of the design and progress. For example, currently the system studies are progressing at rapid speed, being on track to provide detailed inputs to a proposal for the e.deorbit implementation phase to be submitted to the Ministerial Council 2016, however some of the technology development studies are not at the same speed, or suffered a late start, sometimes due to lack of support, so that solutions need to be found to synchronize all activities before the SRR. But reaching the SRR is an achievement in itself: the e.deorbit mission started from scratch as no ESA programme was requesting this. Yet due to a motivated team of both ESA, industry and delegations, and the push of the Clean Space Initiative, the study matured to a phase B1 level. It is a challenging mission that requires new developments as capturing a uncooperative space debris using a spacecraft and then de-orbiting it, has never been done before, and will allow Europe to take the lead in Active Debris Removal technologies.