1. Navegação óptica espacial José Manuel N. V. Rebordão Faculdade de Ciências da Universidade de Lisboa Ciência 2009, 30 de Julho de 2009

2. 2009 Abstract uAutonomous navigation of spacecrafts is a mandatory technology in the context of a wide variety of space missions, such as rendezvous and docking, landing or constellation management. Sensing systems, in particular active or passive optical sensors, play an unique role to feed GNC systems with suitable spatial and temporal data. In addition noise characteristics are critical to select and parameterise signal processing filters and ensure smooth navigation. uSince Portugal became a member of ESA, optical navigation has been addressed by Portuguese research units and companies, working in most of the cases in close collaboration with EADS-Astrium, and several projects were awarded to develop and consolidate technologies and to generate performance models to guide the specifications and development of the GNC chain. Slowly but effectively, the TRL level has been increasing, leading to flight experiments and demonstrations in realistic environments under preparation to flight in ESA / Proba 3. uSeveral optical navigation techniques will be presented in the context of the control of constellation configurations, terrain-related navigation, rendezvous between autonomous spacecrafts and generation of hazard maps to enable the selection of the less hazardous landing site, supported by optical metrology and imaging or lidar data.

3. 2009 Optics / Photonics in Space Instrumentation / Payload (all ) u Analogue & Digital optics u Focal plane / sensors u P/L design assessment, performances & telemetry uSpacecraft / System u Attitude and navigation sensors u GNC sensors u Configuration management u Harness u Optical communications u Structure monitoring (FO sensors) u OGSE

4. 2009 What type of Missions ? uAutonomous missions u Solar system exploration u Man cannot be on-the-loop uConstellation of spacecrafts (S/C) u Real-time configuration control u System of several specialized S/C u Multi-aperture Instruments uMetrology

5. 2009 Functions to be performed uRelative navigation wrt u Terrain u Stars (star mappers, star trackers, sun sensors) u Planets & small bodies (Earth sensors) uLanding u Hazard mapping (in the context of Hazard Avoidance) uRendezvous & Docking u Range and attitude estimation uInstrument enablers u Configuration determination uRanges, angles ( and corresponding velocities and accelerations) u Configuration keeping u Manoeuvring control uPointing, change of geometry / baseline, …

6. 2009 Optics plays a role uSupplying derived data to the GNC system uComplementing / filtering / improving other navigation sensors with redundant data u IMU uEmbedded in a chain of several variable accuracy and time response sensors (metrological chain) u RF u Others (optical, …)

7. 2009 Main interfaces / dependencies uADCS u Attitude Determination & Control Systems uGNC u Guidance, Navigation & Control uSystem level u Type and degree of S/C stabilization u Location in S/C u Thrusters influence

8. 2009 Types uPassive u Camera-based / imaging uTerrain uCelestial bodies uOther spacecrafts (patterns of lights, 3D, …) uActive u LIDAR u Interferometric u Lateral sensing

9. 2009 Constrains and critical tradeoffs uMechanisms u Zooming variable resolution u Angular steering focus of attention uPower u LIDAR uSystem u Redundancy u Radiation hardening uProcessing power & Bandwidth u (>>) 1 – 10 Hz u Image-related u Intelligent processing u Number of devices uMission-related u Timing uThermal illumination, shadows, … uEclipse / non-eclipse

10. 2009 Examples uLanding / Hazard mapping u Passive uVBrNav HASE u Active uLiGNC LAPS uRendezvous & Docking u VBrNav GNCO PROBA 3 uESA Missions u PROBA 3 u Mars Return Sampler u Next Moon Lander uNavigation & Positioning u AUTONAV AEROFAST u NPAL u PLANAV uConstellation / Instrument configuration u High Precision Optical Metrology (DARWIN) Fabry-Perot Metrology PROBA 3 u FEMTO (XEUS) Mode Locked Semiconductor Lasers

11. Navigation & Positioning

12. 2009 ESA - AutoNav Autonomous on-board navigation for interplanetary missions PartnersESA, EADS Astrium (Fr), GMV (Sp), BDL FundingESA ContractsESA EADS Astrium INETI StartSeptember 2001 EndJuly 2004 Simulation of the navigation optical camera, to be included into the general system simulator; generation of images of star fields, planets and asteroids. Image analysis of star fields, asteroids and planets in order to measure the attitude of spacecraft and contour / limb of asteroids, enabling autonomous relative navigation.

13. 2009 Autonav – Faint object detection uTo locate a non-resolved faint punctual object using multiple time integration (MTI) approach to increase the SNR, and 3x validation based on the linearity of displacement. u 20 to 30 images are accumulated in sequence, … u made overlap using guide stars and added to increase SNR u The process is repeated three times to discriminate faint fixed stars from faint moving bodies (asteroids or comets) uMagnitude 13 objects should be detected with MTI uThe soonest asteroids are detected, the more accurate navigation is!

14. 2009 Autonav – Bright object detection uSmall objects & phase correction uFull object within FOV uLimb measurement

15. 2009 FP7 - AEROFAST AEROcapture for Future spAce tranSporTation PartnersAstrium (Fr), Deimos Engenharia, Corticeira Amorim (PT), Samtech (B), U. Rome, STIL (Bu), I. Lotnictwa (Pl), SRCPAS (Pl), ONERA (Fr), Kybertec (CZ) FundingFP7 ContractsEADS Astrium SAS INETI StartSeptember 2008 End2010 Solar system missions (e.g., Mars) relying on return missions (humans and cargo) must rely on aerocapture to be mass effective and use atmospheric drag to slow space vehicles. Aerocapture demands extremely accurate navigation Image-based optical navigation (images of planet limbs, stars and asteroids) to support GNC.

16. 2009 ESA - Planav Image based navigation tool for Mars landing PartnersESA, Deimos Engª (P) FundingESA (Task Force Portugal – ESA) ContractsESA Deimos Engª INETI StartAugust 2003 EndDecember 2003 Utilization of the geophysical cameras of Beagle in the opposite direction, to track Mars moons Phobos and Deimos, against a fixed background of bright stars. Analysis of the visibility of stars and moons, to ensure that the Kalman filter receives an adequate number of observables, in order to reduce the positional error of Beagle 2. Precise determination of Beagle 2 landing position in Mars Beagle 2 as seen from Mars Express

17. 2009 ESA - NPAL Navigation for planetary approach and landing PartnersESA, EADS Astrium (Fr), O. Galileo (It), U. Dundee, SSSL (Uk), Atmel (It) FundingESA ContractsESA EADS Astrium INETI StartDecember 2001 EndJuly 2004 Image analysis of planetary surfaces (feature detection and tracking) in order to enable navigation relative to the terrain (kinematics). Modelling and testing image processing algorithms hardcoded in one ASIC (FEIC camera)

18. 2009 Courtesy of EADS Astrium SAS NPAL – Relative Navigation issues uSupported by vision u Last 20 km in about 60 s. u Relative surface velocity from ~750 m/s to 0. u FOV 70º u 1024x1024. 50 Hz uThermal constrains: u Landing at dawn u Sun very close to the horizon (< 5º) ulong shadows.

19. 2009 NPAL – Relative Navigation issues uWith a single measurement, the LOS to a feature point is known, but not its depth. uTracking the point with a dynamical filter allows progressive determination of depth. For that: u Displacement and rotation of the S/C between two consecutive measurements MUST be known. uRotation gyroscopes uDisplacement requires v, but errors in v grow, because v is integrated from a. uThe vehicle state estimation is performed through sequential Kalman filtering (one sub-optimal implementation, Sparce Weight Kalman Filter, tested) u~ 50 points are used in the state vector

20. Terrain-relative navigation. What for? For safe landing with vision-based risk assessment (hazard mapping) and Hazard Avoidance Passive systems (camera) VBrNav HASE NextMoon Active systems (lidar) LiGNC LAPS NextMoon

21. 2009 Vision Based Landing: objectives Courtesy of EADS Astrium SAS Objective: Landing on a planet without atmosphere (Mercury) on a only 10% hazard-free surface Hazard avoidance (HA) is responsible for hazard detection and path-planning to avoid the detected hazards with constraints on fuel and spacecraft control authority.

22. 2009 Vision based Landing: Hazard Avoidance (HA) uHazard Mapping: process of analysing terrain topography and detecting hazards through IP algorithms applied to the monocular optical images taken by the onboard navigation camera. uPiloting: concepts of data fusing, planning and decision-making used for the selection of a safe Landing Site (LS). uGuidance: concepts used to steer the spacecraft to the Landing Site (it can change during flight).

23. 2009 ESA – VBrNav / HM Vision-Based relative Navigation techniques framework PartnersESA, LusoSpace, Deimos Engª (P), EADS Astrium (F) FundingESA (Task Force Portugal – ESA) ContractsESA Deimos Engª INETI StartFebruary 2004 EndMarch 2006 Development of landing hazard maps (in view of Mercury or Mars landing), based on optical images using shape from shading methods.

24. 2009 HM issues uTopography ( slope) estimation using different IP methods u Motion Stereo u Optical flow u Shape from Shading (SFS) u Merging with Navigation DEM0 uImage analysis to derive u Shadows u Texture (boulders and craters) uHazard fusion

25. 2009 ESA - LiGNC LIDAR Guidance, Navigation and Control PartnersESA, EADS Astrium (Fr), Deimos Engª, Solscientia (P), U. Dundee (Uk) FundingESA ContractsESA EADS Astrium INETI StartSeptember 2001 EndJuly 2005 LIDAR data processing to: - generate topographic maps of the landing regions, - build up landing hazard maps - estimate dynamically navigation kinematical parameters.

26. 2009 ESA - LiGNC

27. 2009 ESA – LAPS LIDAR-based Autonomous Planetary landing System PartnersEADS Astrium SAS (Fr), ABSL Space Products (Uk), Vision-Box (Pt), U. Dundee (Uk) FundingESA ContractsESA EADS Astrium FCUL Start2008 End2010 New Lidar developed for planetary topography Image processing (IP) consolidation Updating LiGNC IP algorithms for LAPS needs: Adaptation to LIDAR outputs Real-time implementation and optimization (with Vision-Box) Tests

28. Rendezvous & Docking VBrNav / RVD GNCO & GNCO Maturation PROBA 3

29. 2009 ESA – VBrNav / RDV Vision-Based relative Navigation techniques framework PartnersESA, LusoSpace, Deimos Engª (P) FundingESA (Task Force Portugal – ESA) ContractsESA Deimos Engª INETI StartFebruary 2004 EndMarch 2006 GNC (Guidance, Navigation & Control) for Rendezvous & Docking between autonomous S/C (in view of Mars Return Sample mission) uDesign Drivers u Early detection of the target for a specified radial dispersion (50, 100 m) at a specified range (1, 1.5, 2 km) u ±1º attitude uncertainty of the chaser Space qualified CCD (1024x1024, 15 m) u No zoom, only 1 fixed camera u Minimum number of light spots on the target u Eclipse

30. 2009 ESA – GNCO MATURATION Guidance for Non-Circular Orbits PartnersDeimos Engenharia FundingESA ( Task Force Portugal – ESA ) ContractsDeimos Engenharia FCUL StartJanuary 2006 EndDecember 2010 Mars Return Sampler mission Modelling optical navigation sensors and image processing chain Development of performance models Laboratory test bed Real-time test bed with WH in the loop Passive spherical, non-stabilized white canister with RR

31. 2009 PROBA-3 ESA – PROBA 3 Autonomous Rendezvous Experiment PartnersDeimos Engenharia, … FundingESA ContractsDeimos Engenharia INETI Start2009 End2012

32. Constellation / Instrument configuration PROBA-3

33. 2009 ESA - HPOM High precision optical metrology (Darwin) PartnersESA, EADS Astrium (Fr + D), SIOS, TPD/TNO (Nl), EADS-CASA (Sp) FundingESA ContractsESA EADS Astrium INETI StartDecember 2001 EndDecember 2005 DARWIN is based on an InfraRed Space Interferometer (MAT) to detect planets in non- solar planetary systems. Optical metrology (FSI, frequency sweeping interrferometry) for formation flying missions New concepts for compensation of metrological networks in space.

34. 2009 FSI - Frequency Sweeping Interferometry Laser & Detection Optical Head FSI Head uESA / FP-MET – Fabry-Perot Metrology uNon ambiguous measurement uNo need for frequency stabilization uLow hardware complexity (transferred to software) uCompactness uSynthetic wavelength down to the mm range m level accuracy at short ranges uMeasurement of drift between S/C

35. 2009 FSI for Multiple Aperture telescopes u.u. uSynthetic optics, Michelson configuration uStabilization of the interference patterns uMetrological chain to control the optical delay lines uFSI for coarse compensation, relative metrology for RT stabilization

36. 2009 FSI for distance measurement CandidateTechnology for ESA PROBA 3 (2013) Vacuum tests in 2009

37. 2009 ESA - FEMTO Absolute long distance measurement with (sub- ) μ m accuracy for formation flight applications PartnersESA, TPD/TNO (Nl), LCVU (Nl), ASTRIUM (D) FundingESA ContractsESA TPD/TNO INETI StartJanuary 2007 EndDecember 2009 Realisation and fundamental technological limitations of pico ( ps, 10 -12 s ) and femto-second (fs, 10 -15 s) metrology Assessment of the maturity of the technology Applicability of fs-metrology to different space mission scenarios Complexity and impact at system level

38. 2009 Baseline Metrology for XEUS uXEUS (X-ray Evolving Universe Spectroscopy): two separate spacecrafts flying in formation with a focal length of 35 m, without the use of a large deployable bench or a telescope tube system. uXEUS Optical metrology must measure all 6 degrees of freedom of DSC (Detector S/C) relative to MSC (Mirror S/C), uThe solution to measure 6 DOF is to use a Trilateration scheme to obtain the lateral displacements and angular orientation of the DSC wrt the MSC with an absolute distance metrology system.

39. 2009 Mode locked Semiconductor Lasers for Optical Precision Metrology PartnersEADS Astrium (D), Reflekron (Fi) ( observers ) FundingESA – ITI (Industrial Triangular Initiative) ContractsESA FCUL Start2008 End2010 Modelocked Semiconductor Laser accurate timing stabilization Pulse Cross-correlation for time-of-flight distance measurement Application to space and to Formation Flying missions metrology ESA- Mode Locked Semiconductor Lasers

40. 2009 Final comments (excluding Configuration-type issues) uSolid-state lasers uMulti-camera u Redundancy u Zooming u Changing FOV / resolution u Steerability u Eclipse / non-eclipse phases u Huge amount of on-board u Processing capability u Telemetry u Intelligence Mechanisms !APS cameras !

41. 2009 Acknowledgements uINETI FCUL u Bento Correia (now @ Vision Box) u Alexandre Cabral u Paulo Motrena u Manuel Abreu u João Coelho u Conceição Proença u João Dinis u Elena Duarte uESA uEADS Astrium GNC team uDeimos Engenharia GNC team END !