ANDROID Small Active Debris Removal Mission
In recent years the concern about the future exploitation of space has been growing due to the risk that uncontrolled space debris poses to the space environment and therefore to the survivability of operational spacecraft. Two main regions of concern exist, GEO, where most of the commercial telecommunications satellites orbit, and LEO, where many scientific missions observing the Earth fly. Of special concern is the sun synchronous orbit, of special interest for Earth sciences. The population of debris in this region has been growing, increasing the risk of a collision and hence the exponential increase in the number of debris. One of the possible solutions to this problem is Active Debris Removal. Recent have studies shown that the situation could be contained if 5 to 10 debris objects are removed per year. Initially those debris objects should be the ones posing more risk, usually large objects (high mass, high surface, high energy). But smaller debris objects should be also targeted. ANDROID mission is proposed as an affordable solution to deorbit small targets (200kg). the mission can offer the opportunity to exercise different technologies and strategies that can be required for missions targeting larger debris. AnDROiD mission has been studied by GMV with the support of QinetiQ Space for platform design, Space Research Centre Polish Academy of Sciences for the robotic arm design and GMV Romania for the net system design. System level sizing has been carried out as well as investigations and definition of the most critical technologies for the mission, namely the guidance, navigation and control system and the capture mechanisms. The mission has been sized to offer the possibility of attempting at least two different capture techniques before the actual deorbiting of the target, a rigid method (robotic arm) and a flexible one (net system). These technologies are representative of the broarder set of capture techniques that are being studied at the moment for different missions, ranging from clamps or tentacles to harpoons. The robotic arm capture will be performed first, followed by a set of secondary GNC experiments. A second capture of the target will be performed with the net system for later deorbit of the compound. PROBA2 has been selected as target of opportunity. PROBA2 was launched on the second of November 2009 by a Rockot launch vehicle. The main goal of mission was technology demonstration while at the same time provide scientific observations of the Sun. Currently it is still operational in a sun-synchronous orbit at 718km altitude with a local time of ascending node of 06h24 am. By the time ANDROID is put into orbit PROBA2 will have exceeded its operational lifetime. Therefore it has been considered for the goals of the study that PROBA2 will be non-operational, though having an operational target would widen the set of experiments that could be carried out as well as provide additional information for the validation of the results. Initial analysis indicates that PROBA2 should be spinning at an angular rate of 5 revolutions per orbit. Two grasping points have been identified. The adaptor ring, selected as baseline point due to its generality with respect to other missions, and the DSLP antenna as backup (TBC). The ANDROID mission is to be launched in a shared launch into LEO. The total mass of the system is expected to be under 350kg, therefore there should be no problem in finding a candidate launch opportunity. Furthermore, SSO is a popular orbit for which several flights are done per year. The most popular orbits are around 650km altitude dawn dusk (quite close to the target orbit of Android) and 820km altitude 10:30 LTAN. A launch opportunity should be selected so that the DV and time required to arrive to the final orbit is minimised. The flight system is based on the PROBA NEXT platform, which is the successor of the PROBA1, PROBA2, and PROBA-V/egetation) satellites developed by QinetiQ Space. The PROBA-NEXT platform is a fully redundant all-purpose and generic platform that can host payloads in the range of 150kg and that can deliver more than 600W of power. For the purposes of ANDROID it is complemented with a small Robotic Arm for the debris capture, Net System and a complex GNC system in charge of autonomous proximity operations. The GNC system is based on standard AOCS equipment and complemented with relative navigation sensors. Feasibility analysis of the mission has been carried out together with the preliminary definition of the critical subsystems. Technology maturity for the different elements has been analysed and a development roadmap proposed for each of the main technologies. The paper will provide de details of the mission design as well as the development roadmap and schedule.