1. MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

2. LWC – R ESIDUAL I SSUES Instrumental features (wiggles, slopes etc...) are sometimes present in the LWC spectra These features are caused by external vibrations and thermal gradients inside the instrument wiggles SLOPESLOPE MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

3. P RINCIPAL C OMPONENT A NALYSIS We attempted to correct for the residual artifacts by using the PCA The idea is to individuate the eigenvectors which are responsible for tilts and wiggles MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain We attempted to correct for the residual artifacts by using the Principal component analysis (PCA).  The PCA involves a mathematical procedure that transforms a number of possibly correlated variables into a number of uncorrelated variables called principal components, related to the original variables by an orthogonal transformation.  This transformation is defined in such a way that the first principal component has as high a variance as possible (that is, accounts for as much of the variability in the data as possible), and each succeeding component in turn has the highest variance possible under the constraint that it be orthogonal to the preceding components.  The PCA is the simplest of the true eigenvector-based multivariate analyses. Often, its operation can be thought of as revealing the internal structure of the data in a way which best explains the variance in the data.  If we apply the PCA to a dataset of measurements of an ideal source (e.g., perfectly stable), the eigenvectors of the covariance matrix will reveal the responsible for the source-unrelated variation in the data (e.g., thermal instability of the instrument and, most important for us, the external mechanical vibrations). In simple words:

4. P RINCIPAL C OMPONENT A NALYSIS We first applied the PCA to a dataset of deep space observations. The deep space can be considered as a very stable source indeed. We found that the very first eigenvector is always sinusoidal in shape Examples of ‘tilt’ eigenvectors ‘wiggles’ vectors for correlation so-called 1 st component MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain The sinusoidal shape can be easily associated to the “slopes” observed in the measured spectra: the signal will increase (decrease) in one part of the spectral range, and will decrease (increase) on the other part, depending on the sign of the coefficients of the eigenvector.

5. P RINCIPAL C OMPONENT A NALYSIS Orbit 730 – Spectrum #4 Original 1st component removed In most of the cases, removing the 1 st component gives optimal results MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

6. P RINCIPAL C OMPONENT A NALYSIS Orbit 730 – Spectrum #386 Original 1st component removed In most of the cases, removing the 1 st component gives optimal results MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

7. P RINCIPAL C OMPONENT A NALYSIS Orbit 72 – Spectrum #177 Original 1st component removed wiggles removed Sometime the ‘wiggles’ component is found and removed MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

8. P RINCIPAL C OMPONENT A NALYSIS Orbit 72 – Spectrum #177 Original 1st component removed wiggles removed If nothing has to be removed, nothing is removed !!! MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

9. P RINCIPAL C OMPONENT A NALYSIS Orbit 72 – Spectrum #177 Original 1st component removed The vibrations generate “correlated noise” that can be removed MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

10. P RINCIPAL C OMPONENT A NALYSIS …clues from the NESR… MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

11. P RINCIPAL C OMPONENT A NALYSIS The PCA helps reducing instrumental artifacts Improvements: correction for slopes, artifacts, and noise reduction. Best results with large datasets You are encouraged to perform similar analyses …conclusions… MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

12. P HASE I NVERSIONS  In presence of a very warm atmosphere or surface, we can experience phase inversions in the LWC spectra.  Many occurrences has been detected during the recent Global Dust Storm, when the atmospheric temperature is raised up by some tens of Kelvin by the presence of Dust.  Occasionally, phase inversions were detected in some observations during summer season.  The LWC detector is a pyroelectric, i.e. it measures the differences between its own temperature (~ 287 K) and the source temperature.  When this difference changes in sign (e.g. positive inside the 15-  m CO 2 absorption band and negative for a surface at 300 K), a phase inversion occurs.  Then the absorption features are seen as emission and vice versa, and the spectrum shows the spectral features of the PFS optical elements (beamsplitter, dichroic mirror…)  In principle, the spectra can be corrected, but an automated procedure is hard to develop and requires an extensive validation campaign. PFS Internal Meeting, 06 October 2010, IFSI-INAF, Rome (IT)

13. LWC: P HASE I NVERSION S Orbit 4443, sp # 91 CO 2 Q-branches are flipped Spurious features MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

14. P HASE I NVERSION S In principle, the spectra can be corrected, but an automated procedure is hard to develop and requires an extensive validation campaign. MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

15. LWC P HASE I NVERSION S MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

16. SWC I SSUES The Short Wavelength Channel spectra suffer the following main problems: S PIKES IN THE SPECTRA ( direct observations of the laser diode light ) –Only for orbits ≤ 634 C ONTAMINATION OF POINTING MIRROR ( can be removed! ) G HOSTS ( # and position depends on the frequency of external vibrations ) M ODULATIONS IN THE SPECTRA ( straylight ??? ) P HASE INVERSIONS –In the thermal part of the SWC –APIC 8 –V2e MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

17. There is a spectral feature between 2800 and 3000 cm -1 ; this feature was absent in the laboratory measurements. We have been able to trace all the experiment activity until the Launch preparation activity in Baikonour. Still in Baikonur we had spectra of the Internal Calibration Lamp without this structure, so it must have been generated during the launching itself, or immediately after in space. The contamination is a hydrocarbon (or mixture) and the features are the stretch transitions of the CH 2 and CH 3 groups. The general shape of these bands has been verified to be essentially constant and can be corrected when generating the calibrated spectra.

18. MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

21. SWC: G HOSTS ( Number and position depends on the frequency of external vibrations ) MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

22. G HOSTS MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

23. G HOSTS MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

24. G HOSTS MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

25. G HOSTS MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

26. M ODULATION MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

27. M ODULATION MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

28. P HASE I NVERSIONS MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain

29. P HASE I NVERSIONS MEx and VEx DATA WORKSHOP - PFS and SOIR experiments - 27 June - 1st July 2011, ESA/ESAC,Spain