Browsing by Author "Easdown, William"
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Item Open Access A mission architecture and systems level design of navigation, robotics and grappling hardware for an on-orbit servicing spacecraft(UKSEDS, 2020-10-10) Easdown, William; Felicetti, LeonardOn-orbit servicing (OOS) includes a range of servicing types that increase the lifetime of a satellite and its performance, as well as ensuring that it does not contribute to the growing issue of space debris. The avoidance of satellites becoming derelict is particularly important given the rise of ‘mega-constellations’. With the first cases of it in the 1970s, OOS has been achieved many times using crewed missions and robots controlled from the ground or by astronauts, for example during repairs and upgrades to the Hubble Space Telescope (HST) and on the International Space Station (ISS). This has allowed various space agencies and other organisations to mature processes and tools for several OOS mission types. The Northrop Grumman Mission Extension Vehicle-1’s (MEV-1) success servicing Intelsat 901 in early 2020 demonstrated that OOS is now viable from a commercial as well as technical standpoint. However, due to low technology maturity, autonomous rendezvous and proximity operations (RPO) and servicing remain challenging, despite autonomous rendezvous and docking with space stations having been demonstrated many times. This report will investigate the current state of the art in OOS and which technologies require further development to enable widespread adoption of OOS. A mission architecture to support OOS of satellites in the highest populated orbits will be described. Using this architecture, the report will focus on the selection of hardware required for guidance, navigation and control (GNC), for relative navigation towards and docking with the target satellite and of robotics to service the target. The report will use the design of the OneWeb satellites as a baseline for the target spacecraft but will also show how the servicing spacecraft’s services could be applied to a range of orbits and target spacecraftItem Open Access Mission ORCA: orbit refinement for collision avoidance(Springer, 2022-03-23) Barles, Anaïs; Bilkhu, Satnam; Boulnois, Anthony; Cuesta Arija, Francisco Javier; Duarri Albacete, Guillem; Easdown, William; Estalella Silvela, Alvaro; Gallego Fernández, Ramiro; Kent, Ben; Martínez Mariscal, Javier; Martinez Mata, Alfonso; Pradeep, Shilpa; Sinclair, Giovanni; Stephens-Simonazzi, Benedict; Yan, Wenhan; Felicetti, LeonardForecasting of collisions between resident space objects (RSOs) is becoming critical for the future exploitation of near-Earth space. A constellation of 28 spacecrafts (plus in-orbit spares) in sun synchronous orbits is proposed as a solution for improving the current space situational awareness capabilities. Each satellite uses an optical payload to track target RSOs, with the satellite's position precisely determined. Multiple pictures of the RSO are taken, and the spacecraft attitude used to calculate the target's position relative to the spacecraft. The target's orbit is then determined from the movement of the target through the field of view over time. The system outputs orbit state vectors of the tracked object, allowing precise orbit characterisation and collision forecasting to be delivered. The constellation's design allows high temporal resolution, so reliable information can be supplied to end-users. The paper shows the results of the system design of a demonstration mission meant to verify the feasibility of the concept, performed by a team of students of Cranfield University. The exercise addresses all the aspects of the preliminary design, including the definition of the mission and system requirements, the selection of the overall mission architecture, operations, and mission phases. A cap on the overall cost allows for the realisation of the platform within a university budget. The outline of the design includes not only the selection and sizing of all the subsystems and payload but also suggests a new strategy for deploying the constellation if the demonstration mission is successful. The utilisation of high TRL and COTS components, as well as mass, power, and link budgets, demonstrate the feasibility of the overall mission concept.Item Open Access Mission ORCA: Orbit Refinement for Collision Avoidance(iafastro, 2020-10-14) Barles, Anaïs; Bilkhu, Satnam; Boulnois, Anthony; Cuesta Arijaa, Francisco Javier; Duarri Albacete, Guillem; Easdown, William; Estalella Silvela, Alvaro; Gallego Fernández, Ramiro; Kent, Ben; Martínez Mariscal, Javier; Martinez Mata, Alfonso; Pradeep, Shilpa; Sinclair, Giovanni; Stephens-Simonazzi, Benedict; Yan, Wenhan; Felicetti, LeonardWith new launches every year, and the use of 'mega-constellations' becoming commonplace, there is an increasing number of active satellites and other resident space objects (RSOs) in low Earth orbit. However, a collision between objects could be disastrous, having wide-ranging impacts on the collision orbit and all the satellites users within it. Collision forecasting currently has large degrees of uncertainty, causing satellite operators to often ignore collision warnings. It is therefore critical that a system becomes operational to track RSOs and determine the likelihood of collisions with greater accuracy than is currently available. The proposed solution uses a constellation of 28 spacecraft (plus in-orbit spares) in Sun Synchronous Orbits. CubeSats will be used to reduce the cost and the time required for the constellation to become operational. Each satellite uses an optical payload to track target RSOs, with the satellite's position precisely determined. Multiple pictures of the RSO are taken, and the spacecraft attitude used to calculate the target's position relative to the spacecraft. The target's orbit is then determined from the movement of the target through the field of view over time. The system outputs orbit state vectors of the tracked object, allowing precise orbit characterisation and collision forecasting to be delivered. The constellation's design allows high temporal resolution, so reliable information can be supplied to end-users. The paper shows the results of the system design of a demonstration mission meant to verify the feasibility of the concept, performed by a team of students of Cranfield University. The exercise addresses all the aspects of the preliminary design, including the definition of the mission and system requirements, the selection of the overall mission architecture, operations, and mission phases. A cap on the overall cost allows for the realisation of the platform within a university budget. The outline of the design includes not only the selection and sizing of all the subsystems and payload but also suggests a new strategy for deploying the constellation if the demonstration mission is successful. The utilisation of high TRL and COTS components, as well as mass, power, and link budgets, demonstrate the feasibility of the overall mission concept