Italian Workshop on Space Situational Awareness Italian Space Agency Headquarter 9 – 10 July 2012, Roma, Italy PoliMi Expertise and Contribution to Space Situational Awareness Michèle Lavagna Dipartimento di Ingegneria Aerospaziale- Politecnico di Milano Via La Masa 34, 20156, Milano, Italy Team Members and Roles ‣ Politecnico di Milano Name Role Email Michèle Lavagna Associate Professor [email protected] Roberto Armellin Postdoctoral Fellow [email protected] Pierluigi Di Lizia Postdoctoral Fellow [email protected] Monica Valli PhD Student [email protected] Alessandro Morselli PhD Student [email protected] Chiara Massimiani PhD Student [email protected] ‣ Dinamica Srl Name Role Email Michèle Lavagna Partner [email protected] Roberto Armellin Partner [email protected] Pierluigi Di Lizia Partner [email protected] Research Areas and Collaborations ‣ ‣ Past and ongoing work on both NEO and Space Debris Rationales and Curriculum: 2005 Participation to ESA/Ariadna study: • Interval analysis and validated integration techniques • Assessment of their accuracy for error and uncertainty propagation in astrodynamics 2006 Collaboration with Michigan State University (Berz) • High order methods: Differential algebra and Taylor models • Initially developed for particles • accelerators Proposed by R. Moore to perform validated integration of NEO motion • Extremely useful for global optimization Research Areas and Collaborations 2007 2009 Participation to two ESA/Ariadna studies • Branch and bound global optimization; application to MOID computation • Nonlinear tools for uncertainty propagation with applications to Apophis 2009 Interest shown by ESA (Granada, 2009) paved the way to applications in Space Debris sector • Nonlinear mapping of uncertainties in preliminary orbit determination • Fast conjunction analysis and impact probability computation 2010 2011 Collaboration with Università di Bologna (Piergentili), Università di Padova (Francesconi), Università di Roma (Santoni) for Active Debris Removal 2012 • Participation to the ITN “The Asteroid and Space Debris Network” (FP7) • Collaboration with INAF-IRA: Debris orbit determination with Croce del • Nord radiotelescopes Support to the definition of an SSA/NEO architecture in CO-II (Telespazio) Previous Work and Main Results ‣ Nonlinear tools for uncertainty propagation for NEO and Debris • NEO/Debris state is Taylor expanded in initial conditions • Integrations replaced by evaluations of polynomials Fast Monte Carlo simulation: Computational time reduced to 1% • Polynomials are manipulated to obtain time and distance of close approach as a function of initial conditions Accurate and fast computation of impact probability ‣ MOID computation • The use of rigorous global optimizers guarantees that the exact MOID is computed • • The algorithm is able to handle multiple solutions The Taylor expansion of the MOID w.r.t. uncertain parameters is computed MOID range including uncertainties Previous Work and Main Results ‣ Orbit determination • Uncertainties are taken into account throughout the orbit determination process Nonlinear mapping of uncertainty in NEO state • Subsequent high order propagation improves accuracy for NEO follow-up Finer enclosure of the region to be observed • ‣ Fast nonlinear filtering techniques have been developed to improve accuracy with additional observations Active Debris Removal • Robustness analysis to uncertainties on boundary • • • conditions and model parameters Nonlinear optimal feedback control algorithms for uncertain boundary conditions (noncooperative debris) Optimal control laws robust to uncertain model parameters Capture mechanisms: docking, net, expanding foam Implemented Methods ‣ The implemented algorithms are based on differential algebra (DA) Algebra of real numbers Algebra of Taylor polynomial ‣ DA allows semi-analytical, nonlinear, and efficient mapping of uncertainties (e.g. high order expansion of the flow of ODE) ‣ When nonlinearities play a crucial role ‣ DA enables algorithms that are more accurate than those based on linearizations ‣ DA enables algorithms that are more efficient than classical Monte Carlo simulation (orders of magnitude) with comparable accuracy ‣ In combination with interval analysis validated propagation and rigorous global optimization Implemented Methods Debris ‣Tool for computing the weekly collision risk between all operative satellites against a list of all unclassified USSTRATCOM two-line element (TLE) sets (first guess) ‣Orbital filters for reducing the number of pairs to be analyzed ‣Verified global optimizer for computing the time and distance of closest approach (TCA and DCA) ‣Analytical and nonlinear mapping of uncertainties on TCA and DCA ‣Efficient algorithms for computation of collision probabilities combining the Taylor expansion of TCA and DCA and sampling techniques ‣Refinement in more accurate dynamical (numerical) model ‣Methods for nonlinear mapping of observation uncertainties from the space of observables to phase space ‣High-order filters for accurate orbit determination Implemented Methods NEO ‣Algorithms for analyzing NEO trajectories ‣Identification of potentially hazardous objects (PHO) via rigorous computation of MOID ‣Rigorous computation of the time and distance of closest approach (TCA and DCA) ‣Analytical and nonlinear mapping of uncertainties on TCA and DCA ‣Highly accurate expansion of the flow to study close approaches, resonant returns, and for computation of collision probabilities ‣Mapping observation uncertainties from the space of observables to phase space in preliminary orbit determination ‣High-order filters for accurate orbit determination Potentialities - Limitation Potentialities ‣Efficient algorithms for the management of uncertainties in orbit determination and orbit propagation ‣Alternative approach to current ones (independent cross-validation of the result often pursued by ESA) ‣Inclusion in consolidated tools to extend some capabilities and improve performances Limitations ‣Most of the codes is the result of research activity, scientific publications have been produced ‣DA is implemented in COSY-Infinity (open source), a constraint on computer language Funds are needed for software engineering (mandatory) and for DA implementation in a different working environment (nice to have) Unexploited Potentials ‣ Differential algebra has unexploited potentials in ‣ Debris clouds (post-collision) evolution in arbitrary dynamical model ‣ Enrich TLE with confidence region information ‣ Development of alternatives to TLE and SGP4 for orbital parameters storage and objects orbit propagation ‣ Expand the flow of ODE with respect to uncertain parameters (e.g. diameter, spin axis direction, and thermal properties for NEO propagation) or un-modeled perturbation (unknown, but bounded) ‣ Include information on uncertain parameters (not only initial condition) in computation of collision probabilities Contribution to SSA ‣ Started a collaboration with Medicina Observatory ‣ Current activity: support for target selection for observation with a small portion of the Croce del Nord ‣ Future goal: orbit determination for the full scale use of re-engineered Croce del Nord Medicina Medicina Radar survey and follow-up Data processing PoliMi Orbit determination and propagation Catalogue Maintenance PoliMi Risk Assessment Contribution to SSA ‣ TOols for Management of Close Approach Threats (TOMCAT) • Main goals: accurate impact risk assessment and design of optimal collision avoidance maneuvers CA ident. UniRM UniBO MOID & IP PoliMI UniRM Optical & radar measurements UniBO Improved OD UniRM, UniBO PoliMI Risk UniPD Collision avoidance PoliMI ‣ CO-II SSA Architectural Design (collaboration with Telespazio and INAF- OAB) • Main goals: consolidated architecture for civilian SSA with programmatic dossier Req. analysis Candidate architectures identification Supporting analysis Development, deployment, and operation approach Active debris removal ‣ Space system design ‣ Pre-phase A studies for debris removal missions ‣ Rendezvous and docking ‣ Robust control algorithms ‣ Facility for 2D algorithms testing: frictionless table ‣ Proposals to MIUR in collaboration with Uni PD, UniBO, UniNA “Federico II”, Uni RM “La Sapienza” Active Debris Removal ‣ Catching mechanism ‣ Net system design and testing ‣ Expressed interest by ESA and contact with Astrium where similar activities are undergoing ‣ De-orbiting mechanism ‣ Hybrid propulsion for de-orbiting FOTO e dettagli