PERFORMANCE EVALUATION OF 3DPD, THE PHOTOGRAMMETRIC PIPELINE FOR THE CASSIS STEREO IMAGES

A novel photogrammetric pipeline has been designed by INAF-Padova for the processing of the recent stereo images of CaSSIS and it will be a starting point for the future procedures that will be applied to Stereo Camera (STC) (Cremonese, 2009; Da Deppo, 2010) images for the BepiColombo mission to Mercury. The large number of stereo pairs being generated has made it necessary that several teams attempt to generate products. The presented procedures are the two strategies (proposed by INAF-PADOVA and by EPFLLausanne) available nowadays in an international attempt to generate 3D products from the CaSSIS images. The comparisons here presented will be the first of several such efforts and are important to make the planetary community aware of the accuracy of the 3D data available. Furthermore, the possibility to consider higher accuracy DTMs as the ones of HiRISE makes the quality assessment of stereo products of CaSSIS robust and important for the assessment of data to be provided to the scientific community. The performance evaluation of the INAF-Padova pipeline (3DPD software) is the main objectives of this work. Additionally, the comparison between the correlation phase of 3DPD and of ASP (Moratto, 2010) that is integrated in the EPFL pipeline has been considered

A PHOTOGRAMMETRIC PIPELINE FOR THE 3D RECONSTRUCTION OF CASSIS IMAGES ON BOARD EXOMARS TGO

CaSSIS (Colour and Stereo Surface Imaging System) is the stereo imaging system onboard the European Space Agency and ROSCOSMOS ExoMars Trace Gas Orbiter (TGO) that has been launched on 14 March 2016 and entered a Mars elliptical orbit on 19 October 2016. During the first bounded orbits, CaSSIS returned its first multiband images taken on 22 and 26 November 2016. The telescope acquired 11 images, each composed by 30 framelets, of the Martian surface near Hebes Chasma and Noctis Labyrithus regions reaching at closest approach at a distance of 250 km from the surface. Despite of the eccentricity of this first orbit, CaSSIS has provided one stereo pair with a mean ground resolution of 6 m from a mean distance of 520 km. The team at the Astronomical Observatory of Padova (OAPD-INAF) is involved into different stereo oriented missions and it is realizing a software for the generation of Digital Terrain Models from the CaSSIS images. The SW will be then adapted also for other projects involving stereo camera systems. To compute accurate 3D models, several sequential methods and tools have been developed. The preliminary pipeline provides: the generation of rectified images from the CaSSIS framelets, a matching core and post-processing methods. The software includes in particular: an automatic tie points detection by the Speeded Up Robust Features (SURF) operator, an initial search for the correspondences through Normalize Cross Correlation (NCC) algorithm and the Adaptive Least Square Matching (LSM) algorithm in a hierarchical approach. This work will show a preliminary DTM generated by the first CaSSIS stereo images

A Photogrammetric Pipeline for the 3D Reconstruction of CaSSIS images on board ExoMars TGO

CaSSIS (Colour and Stereo Surface Imaging System) is the stereo imaging system onboard the European Space Agency and ROSCOSMOS ExoMars Trace Gas Orbiter (TGO) that has been launched on 14 March 2016 and entered a Mars elliptical orbit on 19 October 2016. During the first bounded orbits, CaSSIS returned its first multiband images taken on 22 and 26 November 2016. The telescope acquired 11 images, each composed by 30 framelets, of the Martian surface near Hebes Chasma and Noctis Labyrithus regions reaching at closest approach at a distance of 250 km from the surface. Despite of the eccentricity of this first orbit, CaSSIS has provided one stereo pair with a mean ground resolution of 6 m from a mean distance of 520 km. The team at the Astronomical Observatory of Padova (OAPD-INAF) is involved into different stereo oriented missions and it is realizing a software for the generation of Digital Terrain Models from the CaSSIS images. The SW will be then adapted also for other projects involving stereo camera systems. To compute accurate 3D models, several sequential methods and tools have been developed. The preliminary pipeline provides: the generation of rectified images from the CaSSIS framelets, a matching core and post-processing methods. The software includes in particular: an automatic tie points detection by the Speeded Up Robust Features (SURF) operator, an initial search for the correspondences through Normalize Cross Correlation (NCC) algorithm and the Adaptive Least Square Matching (LSM) algorithm in a hierarchical approach. This work will show a preliminary DTM generated by the first CaSSIS stereo images

High Velocity Impact Behavior of Composite Sandwich Panels with Self-Healing Capabilities

In this study, the high velocity impact behavior of a dual-plate multifunctional panel composed by a carbon fiber reinforced plastics (CFRP) laminate and an ionomer thermoplastic resin plate is investigated experimentally. A unique characteristic of this panel is the ability to auto-repair holes generated by impacts, which is possible due to the ionomer layer. This panel is also a structural element since it includes a CFRP laminate layer. In the experimental campaign spherical aluminum projectiles with a diameter ranging from 2.3 to 4.5 mm were impacted against the multifunctional panel at impact velocities ranging from ∼2.0 to ∼2.5 km/s and all impacts were normal to the target. Impacts occurring on the CFRP and ionomer side were investigated. The impact response of the panels discussed in this work concerns the following characteristics: debris cloud shape, damage on the witness plate, momentum transferred to the witness plate and self-healing. It was observed that when the ionomer was located on the back side of the panel it hindered the debris cloud expansion. This configuration also resulted in lower momentum transfer to the witness plate. The layers disposition had a minor effect on fragment velocity at the debris cloud tip for impact energies above -200 J. Complete self-healing of the hole occurred in all impact cases up to the projectile diameter of 3.5 mm

Impact Behavior of a Simple Multifunctional Plate Structure

The ionomer self-healing performance in a multilayer plate structure, consisting of woven CFRP and ionomer, was investigated experimentally. It was observed that the ionomer performance is conditioned by its location in the structure. If it is directly exposed to the impact it heals much better, with respect to a case where the impactor first strikes the CFRP and then passes through the ionomer

Impact Tests and Simulations for Multifunctional Materials

none7T. Mudric; C. Giacomuzzo; U. Galvanetto; A. Francesconi; M. Zaccariotto; A.M. Grande; L. Di LandroT., Mudric; C., Giacomuzzo; U., Galvanetto; A., Francesconi; M., Zaccariotto; Grande, ANTONIO MATTIA; DI LANDRO, LUCA ANGEL

3DPD: A photogrammetric pipeline for a PUSH frame stereo cameras

An innovative photogrammetric pipeline has been developed by INAF-Padova for the processing of the stereo images from the CaSSIS (Colour and Stereo Imaging System) (Thomas et al., 2014). CaSSIS is the multispectral stereo push frame camera on board ExoMars TGO (Trace Gas Orbiter) which will image 1.5% of the Mars surface in stereo mode with a spatial resolution of 4.6 m/pixel: the highest resolution single pass stereo capability currently operating a Mars. Data acquisition started in April 2018. The camera is able to provide two images of the same target from two different points of view along the same orbit and within one minute. The telescope is mounted on a rotational stage and its boresight is oriented to 10 degrees with respect to nadir direction. After the acquisition of the first set of images looking forward along track, the rotational stage is rotated by 180 degrees and a second set of images (looking backward) is acquired.The stereo pairs can then be processed to provide the 3D topography of specific targets. The suite of photogrammetry and imaging tools, named 3DPD (3Dimensional reconstruction of Planetary Data) (Simioni a al. 2017), is designed for processing stereo push frame data and producing the three-dimensional data for geomorphological analysis of planetary surfaces.The workflow involves a MATLAB tool for the preparation of the inputs (the mosaicked images and the projection matrices) to be ingested into the 3DPD matching core software. The pipeline is in continuous development and routinely ingests a large number of images that CaSSIS is presently acquiring and will continue to acquire in the future. CaSSIS 3DPD products are the unique DTMs available nowadays and the stereo products have been considered in some scientific work (as described in Section 6.2). The same pipeline faces the need of a dedicated pipeline for the Mercury Global Mapping with the Spectrometers and Imagers for the Mercury Planetary Orbiter (MPO) BepiColombo Integrated Observatory SYStem (SIMBIO-SYS) (Cremonese et al., 2020)

Comparison of self-healing ionomer to aluminium-alloy bumpers for protecting spacecraft equipment from space debris impacts

This paper discusses the impact behaviour of a self-healing ionomeric polymer and compares its protection capability against space debris impacts to that of simple aluminium-alloy bumpers. To this end, 14 impact experiments on both ionomer and Al-7075-T6 thin plates with similar surface density were made with 1.5 mm aluminium spheres at velocity between 1 and 4 km/s. First, the perforation extent in both materials was evaluated vis-à-vis the prediction of well known hole-size equations; then, attention was given to the damage potential of the cloud of fragments ejected from the rear side of the target by analysing the craters pattern and the momentum transferred to witness plates mounted on a ballistic pendulum behind the bumpers. Self-healing was completely successful in all but one ionomer samples and the primary damage on ionomeric polymers was found to be significantly lower than that on aluminium. On the other hand, aluminium plates exhibited slightly better debris fragmentation abilities, even though the protecting performance of ionomers seemed to improve at increasing impact speed