GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 6th ICATT, DARMSTADT, MARCH 2016 GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC

6th ICATT 2016 INTRODUCTION

Objectives The work presented in the paper focuses on the utilization of GNCDE (GNC Development Environment presented in detail at 5th ICATT) for assessing GNC concepts of two different ADR scenarios, both aimed at the post-life disposal of ENVISAT Design, development, verification and validation of the GNC for RDV and de-orbiting phases of E-Deorbit mission Quick preliminary feasibility evaluation from GNC point of view of PRIDE-ISV vehicle used as active debris removal spacecraft The high flexibility of GNCDE has permitted to adapt very quickly the mission data to the two different ADR scenarios 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

6th ICATT 2016 GNCDE OVERVIEW

Integrated environments for the GNC design process The GNC design process requires: A team composed of people with different background and knowledge areas Involvement of different disciplines: Mission design and planning Spacecraft systems knowledge Trajectory design Control design Sensor technology, navigation strategy and filters design Onboard SW coding & verification System verification (including HW in the loop) The GNC design loop is, in general, an iterative process All these facts point to the need for an integrated GNC development environment 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

GNCDE SUPPORT ALONG THE GNC DD&VV process GNCDE provides support to the whole GNC DD&VV process, from requirement analysis to HIL testing 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

6th ICATT 2016 ENVISAT OVERVIEW

Why ENVISAT ADR 8 tons satellite Earth Observation mission lost on April 2012 Currently on a 766 km SSO ENVISAT is a high priority ADR target because of its mass its long decay time (at least 150 years) its location on a Sun-synchronous orbit Very challenging ADR mission from GNC point of view, due to the high inertia and a “random” attitude motion 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

6th ICATT 2016 E.DEORBIT SCENARIO

E.DEORBIT OVERVIEW Chaser satellite launched by a small/medium launcher, which will autonomously perform a rendezvous and docking with the target ENVISAT by mean of a robotic arm Capture and perform a controlled de-orbiting of the target from the LEO protected zone accordingly to mitigation rules and mission scenario requirements The unknown attitude motion of the target and the high inertia puts a heavy demand on the GNC system Wet mass: ~1470 kg (~820 kg of propellant) 12+12 AOCS thrusters of 22 N 4 220 N and 2 425 N thrusters as main engines Camera at far range, LIDAR at medium range and LIDAR 3D at shortest range 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

E.DEORBIT ENVISAT ADR SCENARIO (I) The rendezvous phase is split into far, medium range and close range (synchronization) phases The Stack phase concerns the operations of the composite system, including stabilization, pointing and deorbiting GMV provides the guidance and control during the rendezvous phase Homing (far rendezvous phase), from 8km to 800 m from target Safe hold relative orbit at 800 m (an ellipse trajectory never crossing V-bar) Closing (medium range rendezvous), from 800 m to 100 m Parking hold point, with station keeping over V- bar at 100 m Inspection trajectory: from 100 m perform fly-by around the target and back to parking hold point. Approach along V-bar to 30m Fly-by to the direction of target’s angular momentum vector Attitude synchronization, and approach to 7 m Final approach and fly by to capture point in target’s body frame 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

E.DEORBIT ENVISAT ADR SCENARIO (II) The design and simulations are carried out using GNCDE functionalities, mainly Extensive use of pre-validated Spacelab libraries (both for RW and OBSW) Mission template framework ACED Tool for robust control synthesis and verification in presence of uncertain quantities Montecarlo Tool for rapid setup of MC test campaigns 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

E.DEORBIT ENVISAT ADR SCENARIO (III) Homing phase (ref. vs. real) Synchronization phase (ENVISAT BRF) 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

E.DEORBIT ENVISAT ADR SCENARIO (IV) Performances at capture point (100 case MC, perfect navigation and no uncertainty in the loop) Just initial design references to have a feeling about the nominal control performances Very good and encouraging results for the next steps of the activity but Comparison with requirements (on the other hand not yet consolidated at mission level) would not make much sense at this stage navigation and uncertainties, to be included next in the loop, will degrade the obtained performances of a factor which is not easily and realistically estimable a priori as it depends on a high number of contributors 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

6th ICATT 2016 PRIDE-ISV SCENARIO

PRIDE-ISV OVERVIEW Definition and development of an affordable reusable European space transportation system on the wave of the IXV success Able to perform experimentation and demonstration of multiple future application missions In particular, proposed to demonstrate rendezvous and docking technologies for ADR PRIDE-ISV conceptual design just started, no consolidated data Assumptions from CDR sessions: Wet mass ~2500 kg (~200 kg of propellant) 12+12 90 N thrusters (Isp ~240 s) Typical absolute sensors on-board Camera and LIDAR dedicated to ADR Robotic arm on roof hatch 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

Last approach and synchronization Approach to capture point from 50 m fly-around trajectory First 25 m in LVLH frame Transfer to ENVISAT body frame to follow capture point on ENVISAT body Attitude synchronization with ENVISAT motion Approach to 5 m capture point and 15 minutes station keeping Total DV (considering inefficiencies due to GNC, actuators and sensors in the loop) ~130 m/s Preliminary control designed with ACED Tool, but complete simulation in Simulink template out of the scope Link between GNCDE and Celestia to generate a video of the approach 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

6th ICATT 2016 CONCLUSIONS

Conclusions This paper has presented the utilization of GNCDE in case of two different ADR scenarios for ENVISAT post-life disposal Powerful and flexible GNC DD&VV environment permitting adapting very quickly the simulation template to each scenario The tools provided with GNCDE have been very useful in both scenarios to: Support the analysis and the designs Trajectory generation Control synthesis and verification Montecarlo simulations Smart visualizations PRIDE-ISV would be potentially able to perform ENVISAT ADR The vehicle should be designed around this worst case scenario, due to the AOCS capabilities needed and to the estimated high propellant consumption Very good preliminary results obtained for e.DeOrbit scenario The activity is still on-going and more consolidated results are expected soon, in line with the project schedule 6th ICATT: GNCDE AS DD&VV ENVIRONMENT FOR ADR MISSIONS GNC 2016/17/03

Thank you Luigi Strippoli Email: lstrippoli@gmv.es www.gmv.com