RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 7th International Conference on Astrodynamics, Tools and Techniques H. Benninghoff, F. Rems, E. Risse, P. Irmisch, I. Ernst, B. Brunner, M. Stelzer, R. Lampariello, R. Krenn, M. Reiner, C. Stangl, R. Faller, O. Peinado German Aerospace Center (DLR)

Rendezvous, Inspection, CApturing, and Detumbling by RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 RICADOS Rendezvous, Inspection, CApturing, and Detumbling by Orbital Servicing Rendezvous Inspection Navigation Capturing, Berthing Combined Control Detumbling Mission Operations Research for inspection, rendezvous, berthing, control, mission operations and communications An end-to-end-simulator with simulated space segment, simulated communication path and ground segment as for a real mission Communications Satellite Simulator Test Facilities

Motivation RICADOS is motivated by the demand for RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Motivation RICADOS is motivated by the demand for on-orbit servicing for life-time extension space debris removal robotic tasks with high autonomy in manned and unmanned spaceflight Challenges Passive, non-cooperative target satellite, not prepared for on-orbit servicing Partly unknown target Target with lost attitude control or other damages Safety and robustness requirements due to autonomous rendezvous and berthing Consequences Several on-board and on-ground functionalities needed Advanced simulation and testing required

Overview on RICADOS ground segment control room infrastructure, RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Overview on RICADOS ground segment control room infrastructure, mission operations system hardware-in-the-loop simulators incl. payloads software simulation

RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Main task: Investigate the geometric properties of the target satellite, i.e. generate a geometrical model Inspection starts at hold point at 15-20m distance to the target after mid range rendezvous is finished Round trip flight around the target to collect image data (with stereo camera as inspection payload) Inspection images are processed later on ground after ground contacts with the satellite Also checks for damages are possible.

RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Main task: approaching the uncooperative target satellite by processing information from optical 2D and 3D sensors Pose estimation from 2D CCD (primary sensor) and 3D PMD camera Extended Kalman filter which can handle measurements with delay and performs sensor fusion Guidance function for a reference trajectory Position controller On-board telemetry and telecommand handling  Autonomous on-board GNC (Guidance, Navigation and Control) system which can be commanded from ground via telecommands (e.g. “start straight line approach to 6m with 0.02 m/s”)

Exemplary rendezvous camera images RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Exemplary rendezvous camera images

Capturing & Detumbling RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Capturing & Detumbling Main task: capture the target satellite with a robotic manipulator mounted on the servicer satellite and stabilizing its motion. On-board robotic system: Stereo camera at the robot end-effector Impedance controller (track the reference trajectory + compliance to impacts with the tumbling target) Stabilization / detumbling via control in the joint space of the robot Task management On-board telemetry and telecommand handling Robotic console Supports both standard operation and telepresence (interaction with visual and haptic feedback, operator in the loop) DLR light weight robot integrated at the console which guides the robotic arm onboard Challenge: Long control feedback loop with time delay and jitter (passivity control)

Combined Control Classical control: RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Combined Control Classical control: Splitting of satellite bus control and manipulator arm control Switching off servicer attitude and orbit control system (AOCS) during capturing is however very risky (uncooperative and tumbling target!) New approach: Combined Control One integrated control system for bus and manipulator Controller based on H-infinity control using a linear time-invariant (LTI) model of the servicing system is currently under development Controller is implemented as part of the mission-specific part of the satellite simulator

Simulation Infrastructure RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Simulation Infrastructure Software satellite simulator with telemetry-telecommand system, satellite bus simulation, and multi-body satellite dynamics simulation 2 hardware-in-the-loop test facilities EPOS 2.0 (European Proximity Operations Simulator) at DLR-GSOC for inspection and rendezvous simulation OOS-Sim (On-Orbit Servicing Simulator) at DLR-RMC for capturing and detumbling simulation

RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Communications Main Task: Interconnection of all sub-systems, sending and receiving science data and standard housekeeping data Set-up of the full operations network incl. special devices Merger: FPGA based device for handling commands from 2 sources, e.g. parallel housekeeping commands and commands from robotic system WAN (Wide Area Network) simulator: software which allows changes in packet delay and induce jitter or packet loss (used for realistic simulation) IP firewall (decapsulates CLTU or telemetry frames out of UDP/IP datagrams)

RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Mission Operations Main Task: Perform all operations as realistic as possible like during real missions Operational back end of RICADOS is equal to other missions operated by GSOC (German Space Operations Center) Realistic contact simulation Access to payloads (inspection, rendezvous, robotic) via the communication system, controlled by the Mission Operations System (MOS) 3 dedicated consoles: satellite bus control console, rendezvous console and robotic console Use of mission operations tools GECCOS: GSOC mission control system for satellite operations Display system Satmon Rendezvous and robotic specific tools integrated as virtual machines Access to OPSWEB (operational web server)

On-Orbit Servicing Test Scenario: „LEO Hopper“ RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 On-Orbit Servicing Test Scenario: „LEO Hopper“ Background: DLR satellite strategy: regular launches of compact satellites in low Earth orbits In the future: group of compact satellites in similar orbits Choose fleet servicing in LEO as test scenario for RICADOS Inspection, fly around Close range rendezvous Far & mid range rendezvous Capture with manipulator arm Wait for next service task Detumbling, perform service Retreat after servicing is finished

RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Conclusion RICADOS is a common research project of four DLR institutes in Oberpfaffenhofen and Berlin RICADOS allows to simulate the most critical phases of an on-orbit servicing mission RICADOS includes the full ground segment, simulation of communication and simulation of the space segment Two hardware-in-the-loop facilities are involved where the inspection, rendezvous and capturing payloads are integrated and where realistic target mockups, background and lightning conditions are realized

Video: DLR YouTube Channel RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018 Video: DLR YouTube Channel https://youtu.be/ADS-qGI5kOc