Jean-Sébastien Ardaens

Spaceborne Autonomous Formation-Flying Experiment on the PRISMA Mission

The Prototype Research Instruments and Space Mission Technology Advancement (PRISMA) represents the first European technology demonstration of formation-flying and on-orbit-servicing techniques. Several hardware and software experiments, either at subsystem or system levels, have been successfully conducted since the launch of the dual-satellite mission in June 2010. This paper describes the guidance, navigation, and control functionalities and presents key flight results from the so-called Spaceborne Autonomous Formation-Flying Experiment (SAFE) executed in September 2010 and March 2011 as one of the primary PRISMA mission objectives. SAFE is intended to demonstrate autonomous acquisition, keeping, and reconfiguration of passive relative orbits for advanced remote sensing and rendezvous applications. As shown in the paper, the onboard Global Positioning System navigation system provides relative orbit information in real time with an accuracy better than 10 cm and 1 mm/s (threedimensional, root mean square) in position and velocity, respectively. The impulsive formation control achieves accuracies better than 10m (three-dimensional, root mean square) for separations below 2 km with minimum usage of thrusters, ensuring high predictability for simplified mission operations and minimum collision risk for increased safety

Angles-Only Navigation to a Noncooperative Satellite Using Relative Orbital Elements

This work addresses the design and implementation of a prototype relative navigation tool that uses camera-based measurements collected by a servicer spacecraft to perform far-range rendezvous with a noncooperative client in low Earth orbit. The development serves the needs of future on-orbit servicing missions planned by the German Aerospace Center. The focus of the paper is on the design of the navigation algorithms and the assessment of the expected performance and robustness under real-world operational scenarios. The tool validation is accomplished through a high-fidelity simulation environment based on the Multi Satellite Simulator in combination with the experience gained from actual flight data from the GPS and camera systems onboard the Prototype Research Instruments and Space Mission Technology Advancement mission.

Navigation and control of the TanDEM-X formation

Germany is presently preparing the first operational formation flying mission for Synthetic Aperture Radar (SAR) interferometry in low-Earth orbit. TanDEM-X comprises two nearly identical satellites (TSX and TDX) that are launched with a two-year time shift in 2007 and 2009, respectively. From 2009 onwards, the two satellites will fly in close proximity and collect SAR interferograms for digital elevation model (DEM) generation. The TanDEM-X mission profile is particularly challenging from a flight dynamics point of view and poses new needs for spacecraft navigation and control. These comprise the formation design, the ground-controlled and autonomous formation maintenance, as well as the highprecision reconstruction of the interferometric baseline. This paper discusses the geometry of the TanDEM-X formation along with a relative motion model that forms the basis of the formation control concept and the autonomous onboard navigation. Furthermore, the orbit control and precise orbit determination of the primary spacecraft TSX is illustrated using actual flight data from the first six months of operations.

Spaceborne Autonomous Relative Control System for Dual Satellite Formations

two spacecraft flying on near-circular orbits. Emphasis is given to the practical implementation within an onboard embedded computer, which requires a simple, resource-sparing, and robust design of the system. Therefore, the algorithms are tailored to minimize the usage of onboard resources and to allow the harmonious integration of the relative control system within the space segment. The validation of TanDEM-X Autonomous Formation Flying performed using a hardware-in-the-loop testbed shows that control performance at the meter level is expected.

Relative control of a virtual telescope using Global Positioning System and Optical Metrology

A = plant matrix a = semimajor axis B = deterministic matrix e = eccentricity ec = control error vector GM = gravitational parameter i = inclination K = gain matrix l = reference separation between the occulter and the coronagraph M = mean anomaly Q = control error weighting matrix R = control input weighting matrix r = position in Earth-centered inertial coordinates u = control input v = velocity in Earth-centered inertial coordinates x = state vector in Earth-centered inertial coordinates

Flight Demonstration of Autonomous Noncooperative Rendezvous in Low Earth Orbit

This paper presents ultimate design, implementation, and in-flight performance of the spaceborne guidance navigation and control system which enabled the Autonomous Vision Approach Navigation and Target Identification (AVANTI) experiment; a flight demonstration developed by the German Space Operations Center (GSOC) of the German Aerospace Center (DLR) and carried out in November 2016. Designed to prove the viability to perform far- to mid-range proximity operations with respect to a noncooperative flying object using only optical angle measurements, AVANTI realized the first autonomous vision-based rendezvous to a passive target spacecraft in low Earth orbit. Within this experiment, the DLR Earth-observation BIROS satellite approached down to less than 50 m of inter-satellite distance the BEESAT-4 CubeSat, previously released in orbit by BIROS itself. To this end, a dedicated spaceborne formation- flying system carried out relative navigation and maneuver planning tasks. Moreover, it took over BIROS orientation and maneuvering capabilities to steer the spacecraft along a passively safe rendezvous trajectory. During AVANTI, the images taken by BIROS constituted the only source of relative navigation information. In the absence of external, independent, and precise navigation data of the target satellite, AVANTI performances have been assessed against the ground-based post-facto reprocessing of the images collected in flight.

TanDEM-X Autonomous Formation Flying System: Flight Results

Abstract The TanDEM-X mission is a scientific and commercial Earth observation mission comprising two satellites flying in close formation. The formation maintenance can be advantageously performed by an onboard autonomous system, which reduces the operational efforts, provides a shorter reaction time in case of contingencies and increases the control performance. The TanDEM-X Autonomous Formation Flying (TAFF) system has been developed for this purpose and is intended to replace the ground-based formation keeping activities during routine operations. TAFF has been activated for the first time in October 2010 for commissioning, during which the autonomous usage of thrusters was prohibited. Afterwards, a closed-loop campaign was successfully conducted in March 2011, demonstrating the capability of TAFF to maintain autonomously the formation. After a brief technical description of the system, the paper presents the key results gained during the commissioning phase and the closed-loop campaign.