Speaker
Description
A multi-spectral system has been developed by an European consortium, led by cosine Remote Sensing (NL), including Spanish GMV Aerospace and Defence (ES), for a visual based navigation approach, based on the complementary use of imagery acquired in the Visible Near Infrared (VNIR) and the Thermal Infrared (TIR) spectral ranges. VNIR images exhibit high spatial resolution, but favourable illumination conditions are required to ensure high image quality. Instead, TIR images exhibit a moderate spatial resolution, but they provide target detection irrespective of the illumination condition. Therefore, their use can drastically increase the robustness of the navigation solution (estimation of the relative position and attitude for instance of a chaser spacecraft with respect to a target one in space debris applications).
A dual channel Camera Optical Unit (COU), based on cosine’s heritage in optical instrumentation for robotic and navigation applications has been developed. It integrates two (VNIR and TIR) camera heads in the same mechanical housing. The VNIR camera head consists of a monochromatic 4 Mpx sensor, responsive in the visible and near infrared ranges (400 – 1000 nm). It is equipped with a 21 mm lens, resulting in a 30 x 30 deg field of view. The TIR camera head is equipped with an uncooled, amorphous Silicon 0.3 Mpx microbolometer, sensitive to wavelengths between 8 μm – 14 μm. The two camera heads are interfaced to an integrated image acquisition and processing unit, equipped with a FPGA and a CPU unit. This subsystem exploits cosine’s heritage in CubeSat and nanosatellite applications and performs image grabbing and preprocessing (background subtraction and distortion correction), and handles the communication and data transfer with the IPB.
Two image processing algorithms have been considered by GMV and implemented for real-time applications running on GR740 (LEON4 processor): image centroiding for far range operation (5 km – 100 m) and Model Based Tracking (MBT) for short range operation (100 m – 2 m) potentially used with other sensors. MBT performs a pose estimation (position + attitude) based on the realignment of projected model edges with respect to the observed ones on the target. The use of MBT allows a complete target pose estimation, including an accurate range estimation.
The complementary use of VNIR and TIR images allows to obtain an accurate pose estimation, irrespective of the target illumination and thermal conditions as tested in the Hardware in the Loop campaign, performed at the platform-art© facility, located at GMV premises in Madrid. This included a representative satellite mock-up with active thermal control which allows to replicate evolution of conditions in orbit with results in open-air experiments that can be correlated with those in the vacuum of space.
The proposed navigation system reached a Technology Readiness Level of 5. A roadmap for the flight model has been identified with a compact optical head based on mirrors for a shared optical path (VNIR and TIR), as an evolution of the cosine HyperScout-2 instrument, already successfully employed in Low Earth Orbit operations.
