Review of the mathematical foundations of data fusion techniques in surface metrology

The recent proliferation of engineered surfaces, including freeform and structured surfaces, is challenging current metrology techniques. Measurement using multiple sensors has been proposed to achieve enhanced benefits, mainly in terms of spatial frequency bandwidth, which a single sensor cannot provide. When using data from different sensors, a process of data fusion is required and there is much active research in this area. In this paper, current data fusion methods and applications are reviewed, with a focus on the mathematical foundations of the subject. Common research questions in the fusion of surface metrology data are raised and potential fusion algorithms are discussed

Geometric calibration of Colour and Stereo Surface Imaging System of ESA's Trace Gas Orbiter

There are many geometric calibration methods for "standard" cameras. These methods, however, cannot be used for the calibration of telescopes with large focal lengths and complex off-axis optics. Moreover, specialized calibration methods for the telescopes are scarce in literature. We describe the calibration method that we developed for the Colour and Stereo Surface Imaging System (CaSSIS) telescope, on board of the ExoMars Trace Gas Orbiter (TGO). Although our method is described in the context of CaSSIS, with camera-specific experiments, it is general and can be applied to other telescopes. We further encourage re-use of the proposed method by making our calibration code and data available on-line.Comment: Submitted to Advances in Space Researc

YARARA: Significant improvement of RV precision through post-processing of spectral time-series

Aims: Even the most-precise radial-velocity instruments gather high-resolution spectra that present systematic errors that a data reduction pipeline cannot identify and correct for efficiently. In this paper, we aim at improving the radial-velocity precision of HARPS measurements by cleaning individual extracted spectra using the wealth of information contained in spectra time-series. Methods: We developed YARARA, a post-processing pipeline designed to clean high-resolution spectra from instrumental systematics and atmospheric contamination. Spectra are corrected for: tellurics, interference pattern, detector stitching, ghosts and fiber B contaminations as well as more advanced spectral line-by-line corrections. YARARA uses Principal Component Analysis on spectra time-series with prior information to disentangle contaminations from real Doppler shifts. We applied YARARA on three systems: HD10700, HD215152 and HD10180 and compared our results to the HARPS standard Data Reduction Software and the SERVAL post-processing pipeline. Results: On HD10700, we obtain radial-velocity measurements that present a rms smaller than 1 m/s over the 13 years of the HARPS observations, which is 20 and 10 % better than the HARPS Data Reduction Software and the SERVAL post-processing pipeline, respectively. We also injected simulated planets on the data of HD10700 and demonstrated that YARARA does not alter pure Doppler shifted signals. On HD215152, we demonstrated that the 1-year signal visible in the periodogram becomes marginal after processing with YARARA and that the signals of the known planets become more significant. Finally, on HD10180, the known six exoplanets are well recovered although different orbitals parameters and planetary masses are provided by the new reduced spectra.Comment: 23 pages, 19 figure

The Mid-IR Properties of Starburst Galaxies from Spitzer-IRS Spectroscopy

We present 5-38um mid-infrared spectra at a spectral resolution of R~65-130 of a large sample of 22 starburst nuclei taken with the Infrared Spectrograph IRS on board the Spitzer Space Telescope. The spectra show a vast range in starburst SEDs. The silicate absorption ranges from essentially no absorption to heavily obscured systems with an optical depth of tau(9.8um)~5. The spectral slopes can be used to discriminate between starburst and AGN powered sources. The monochromatic continuum fluxes at 15um and 30um enable a remarkably accurate estimate of the total infrared luminosity of the starburst. We find that the PAH equivalent width is independent of the total starburst luminosity L_IR as both continuum and PAH feature scale proportionally. However, the luminosity of the 6.2um feature scales with L_IR and can be used to approximate the total infrared luminosity of the starburst. Although our starburst sample covers about a factor of ten difference in the [NeIII]/[NeII] ratio, we found no systematic correlation between the radiation field hardness and the PAH equivalent width or the 7.7um/11.3um PAH ratio. These results are based on spatially integrated diagnostics over an entire starburst region, and local variations may be ``averaged out''. It is presumably due to this effect that unresolved starburst nuclei with significantly different global properties appear spectrally as rather similar members of one class of objects.Comment: 22 pages, accepted for publication in ApJ, a high-resolution version is available from http://www.strw.leidenuniv.nl/~brandl/IRS_starbursts.pd