1. 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)

2. 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

3. 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

4. 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

5. 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.

6. 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”)

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

8. 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)

9. 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

10. 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

11. 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)

12. 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)

13. 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

14. 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

15. Video: DLR YouTube Channel
RICADOS – Rendezvous, Inspection, CApturing and Detumbling by Orbital Servicing, ICATT 2018
Video: DLR YouTube Channel