Robin Larsson

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

PRISMA: An In-Orbit Test Bed for Guidance, Navigation, and Control Experiments

This paper presents system-level hardware-in-the-loop real-time simulation results for three different guidance, navigation, and control experiments designed for in-flight demonstration on the PRISMA formation-flying satellite mission. The mission consists of two spacecraft: Main and Target The Main satellite has full orbit control capability, whereas Target is attitude-controlled only. Launch is planned for November 2009. The simulation results presented demonstrate the feasibility and readiness for flight as well as the expected in-flight performance. The three experiments include Global Positioning System and vision-based formation flying for two spacecraft in both passive and forced motion. In addition to these simulation results, the paper gives an overview of the PRISMA mission in general and the guidance, navigation, and control experiments in particular. The hardware-in-the-loop real-time test environment is also presented.

GPS-based relative navigation during the separation sequence of the PRISMA formation

PRISMA is a Swedish-led micro-satellite mission that serves as a test platform for autonomous formation flying and rendezvous of spacecraft. It comprises two satellites which are launched together in a clamped configuration and separated in orbit after completion of all checkout operations. The challenge of the subsequent early operations phase is to maintain the formation safety and in particular to minimize the risk of collision using only a reduced subset of the overall guidance, navigation and control functionalities. While not specifically designed for safe mode operations, the PRISMA GPS-based relative navigation system is still considered the best source of relative orbit information during this mission phase. A comprehensive simulation of the separation sequence has been therefore conducted that demonstrates the robust operation of the GPS navigation system under the adverse conditions of the separation event and the subsequent non-nominal spacecraft attitude. While initially based on offline Simulink/C++ software simulations, the employed test approach makes use of the prototype flight software for the GPS navigation system and enables a seamless transition to real-time software simulations as well as hardware-in-the-loop simulations.

Flight demonstration of formation flying capabilities for future missions (NEAT Pathfinder)

PRISMA is a demonstration mission for formation-flying and on-orbit-servicing critical technologies that involves two spacecraft launched in low Earth orbit in June 2010 and still in operation. Fun ...

PRISMA: An In -Orbit Test Bed for GNC Experiments

The PRISMA formation flying satellite project will demonstrate Guidance, Navigation, and Control strategies for advanced autonomous formation flying. The Swedish Space Corporation (SSC) is the prime contractor for the project which is funded by the Swedish National Space B oard (SNSB). By mid 2008, PRISMA is well into the system integration and test campaign and launch is planned for June, 2009. The mission consists of two spacecraft: MAIN and TARGET. The MAIN satellite has full orbit control capability while TARGET is attitude controlled only. PRISMA will perform a series of GNC related formation flying experiments. SSC is responsible for three main sets of experiments: Autonomous Formation Flying, Proximity Operations and Final Approach/Recede Maneuvers, and Autono mous Rendezvous. This paper focus es on describing these three set s of formation flying experim ents. The system test setup is also described together with real -time system level test results demonstrating the performance of each of the three GNC experiment sets.

Navigation and Control of the PRISMA formation: In-Orbit Experience

This paper presents flight results and lessons learned from the Spaceborne Autonomous Formation Flying Experiment (SAFE) conducted by the German Space Operations Center in the frame of the Swedish PRISMA mission. SAFE represents one of the first demonstrations in low Earth orbit of an advanced guidance, navigation and control system for dual-spacecraft formations. Innovative techniques based on carrier-phase differential GPS, relative eccentricity/inclination vectors and impulsive maneuvering are validated and tuned in orbit to achieve centimeter accurate real-time relative navigation, reliable formation keeping at the meter level and flexible formation reconfiguration capabilities.

Prisma Mission Extension: Adapting Mission Operations to New and Changing Mission Objectives

The PRISMA in-orbit test-bed was launched in June 2010 to demonstrate strategies and technologies for formation flying and rendezvous. OHB Sweden is the prime contractor for the project which is funded by the Swedish National Space Board (SNSB) with support from DLR, CNES, and DTU. In early September of 2011, 15 months after launch, all primary mission objectives of the PRISMA formation flying satellites had been achieved and mission success was declared. Since a significant amount of delta-V capability still remained an open call for new experiments was issued, inviting both old and new experimenters to use the capabilities of the formation. Several interested parties took the opportunity to perform their own experiments with an existing platform, each coming with new mission objectives not previously planned to be flown on the PRISMA satellites. Some of these experiments were close to what had already been achieved within the nominal mission, but some included new ways of using the formation not envisioned by the spacecraft designers. The new experiments span from data collection in specific relative orbits, with a separation from a few meters to several kilometers, to entirely new modules within the on-board software. Changing from a pre-planned technology demonstration mission to operating a commercial resource required adaptation of the original operational concept, taking into account the different levels of experience of the customers and managing the satellites between experiments. This paper describes how these new mission objectives were integrated in operations and how a sometimes very short turn-around between initial concept and experiment execution was implemented with the aid of well established validation processes, high degrees of on-board autonomy and a flexible operations team.