1. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Analysis of spectral features in TNO and asteroid spectra S. Erard, D. Despan, F. Merlin

2. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Spectral observation of TNOs 1998 Cruikshank et al. Dark objects (≥ 18th mag) Shallow spectral features (in the NIR) => Very long exposure times required to access compositional information  implication for observing strategy and for analysis methods

3. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Spectral observation of TNOs Methanol is the second most easily detected ice (after H 2 O) Detection requires SNR ≥ 70 for pure ice Ammonia detection requires SNR ≥ 125 Requirements are higher if only a fraction of the surface is covered, or mixture with other ices C. Trujillo, Catania 2006 meeting 8-10m telescope, mag 18: 1 h exposure SNR ~100 Only 2005 FY9 has been observed with SNR allowing detection of N 2, CO, CO 2, or ethane ice (only ethane is detected)

4. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Spectral observation of TNOs Trujillo’s conclusion, Catania 2006 meeting (excerpt) The Good News: - About 25 KBOs could be observed by an international team of collaborators using the world's largest telescopes. The Bad News: - Don't bother observing any of the brightest 15 KBOs unless you spend at least 4 hours of exposure time on a 8m – 10m telescope in good conditions. Tips for observers: -Don't repeat objects that are already done! -Observe in good conditions and at low airmass! -Take high (80-100) S/N spectra!

5. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Spectral detection /characterization methods Simulation + spectral fit, inversion: - The first step is to identify the components - Extra components just add noise to the fits - Continuum is always an issue Spectral ratios: - Historically important, but very crude MGM: - Adapted only to specific minerals (pyroxenes, olivines, feldpars…) Tetracorder, etc…: - Rely on a more or less complete data base, - Not really adapted to ices Geographic mixture Hapke modelShkuratov model H2Oa----6%5µm H2Oc1%5µm14%5µm5%5µm Carbo n 83%15µm50%15µm68%15µm Ice- Th 5%5µm7%31µm7%5µm Tit-Th5%5µm---- Tri-Th6%5µm29%12µm14%15µm Merlin & Barucci, Catania 2006 meeting

6. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Multiresolution spectral analysis Purpose: - Detection method adapted to low SNR situations Output: - Characteristics of absorptions features (center, depth, width) - Detection thresholds in terms of S/N and proximity to the edges Basis: - Wavelet decomposition + multiscale grouping (based on imaging algorithms) - Uses a dyadic algorithm to avoid band reconstruction Performances: - Separates bands within Rayleigh criterion (if slightly different) - Accuracy on band properties ~10% for Gaussians - Correctly identifies bands at SNR = 3 in I/F - Robust to asymmetrical band shapes - Separates continuum variations from resolved bands

7. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Orthopyroxene (laboratory spectrum) The two bands are correctly detected at all scales Grouping and identification of a dominant scale provides accurate band characteristics Simulations — High SNR

8. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Simulated spectrum + noise 3 wide bands and a narrow one, correctly detected Simulations — medium SNR

9. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Jarosite (lab. spectrum) Many narrow bands on varying structure, correctly detected Bands near the edge (uncomplete) are detected with a low statistical weight Simulations — very tilted continuum

10. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 VLT / Naco resolved observations Bright, extended object (mag ~8) Ice features? Clay features? Ceres, 2.1-2.4 µm CH 3 OH CH 4 H2OH2O N2N2 NH 3

11. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 19 structures detected, mainly small telluric (with atm. counterparts) and solar bands No ice absorption above 5  (disk centre or pole) Possible feature at 2.11 µm Improvement of telluric correction pending Ceres, 2.1-2.4 µm Erard et al., EGU 2006

12. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Observations by Barucci et al 2005 (VLT), R~3000 6 structures detected, mostly telluric correction remants Positive detection at 2.142 µm, corresponding to N 2 ice but significantly narrower Sedna, 1.9-2.5 µm Erard et al., DPS 2005

13. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007 Multiscale analysis methods, coupled with noise filtering algorithm, are very efficient in low SNR situations TNO spectral studies require this kind of analysis The present one, based on a very redundant algorithm, may still be improved with band reconstruction Tests are still being performed on laboratory spectra + observations First article with full description and tests to be submitted in 2007 (hopefully) Conclusion

14. S. Erard et al. — Workshop 3e zone, Nantes, 11-12 janvier 2007