SPHERE/ZIMPOL high resolution polarimetric imager - I. System overview, PSF parameters, coronagraphy, and polarimetry

H. M. Schmid; A. Bazzon; R. Roelfsema; D. Mouillet; J. Milli; F. Menard; D. Gisler; S. Hunziker; J. Pragt; C. Dominik; A. Boccaletti; C. Ginski; L. Abe; S. Antoniucci; H. Avenhaus; A. Baruffolo; P. Baudoz; J.L. Beuzit; M. Carbillet; G. Chauvin; R. Claudi; A. Costille; J.-B. Daban; M. de Haan; S. Desidera; K. Dohlen; M. Downing; E. Elswijk; N. Engler; M. Feldt; T. Fusco; J. H. Girard; R. Gratton; H. Hanenburg; Th. Henning; N. Hubin; F. Joos; M. Kasper; C. U. Keller; M. Langlois; E. Lagadec; P. Martinez; E. Mulder; A. Pavlov; L. Podio; P. Puget; S. P. Quanz; F. Rigal; B. Salasnich; J.-F. Sauvage; M. Schuil; R. Siebenmorgen; E. Sissa; F. Snik; M. Suarez; Ch. Thalmann; M. Turatto; S. Udry; A. van Duin; R. G. van Holstein; A. Vigan; F. Wildi

doi:10.1051/0004-6361/201833620

Home

All issues

Volume 619 (November 2018)

A&A, 619 (2018) A9

References

Free Access

Issue		A&A Volume 619, November 2018


Article Number		A9
Number of page(s)		37
Section		Astronomical instrumentation
DOI		https://doi.org/10.1051/0004-6361/201833620
Published online		06 November 2018

Aiello, A., Merano, M., & Woerdman, J. P. 2009, Phys. Rev. A, 80, 061801 [NASA ADS] [CrossRef] [Google Scholar]
Akiyama, E., Muto, T., Kusakabe, N., et al. 2015, ApJ, 802, L17 [NASA ADS] [CrossRef] [Google Scholar]
Amara, A., & Quanz, S. P. 2012, MNRAS, 427, 948 [NASA ADS] [CrossRef] [Google Scholar]
Antoniucci, S., Podio, L., Nisini, B., et al. 2016, A&A, 593, L13 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Appenzeller, I. 1968, ApJ, 151, 907 [NASA ADS] [CrossRef] [Google Scholar]
Aronson, E., Bladh, S., & Höfner, S. 2017, A&A, 603, A116 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Artmann, K. 1948, Ann. Phys., 437, 87 [CrossRef] [Google Scholar]
Aspin, C., Schwarz, H. E., McLean, I. S., & Boyle, R. P. 1985, A&A, 149, L21 [NASA ADS] [Google Scholar]
Avenhaus, H., Quanz, S. P., Schmid, H. M., et al. 2014, ApJ, 781, 87 [NASA ADS] [CrossRef] [Google Scholar]
Avenhaus, H., Quanz, S. P., Schmid, H. M., et al. 2017, AJ, 154, 33 [NASA ADS] [CrossRef] [Google Scholar]
Bailey, J., & Hough, J. H. 1982, PASP, 94, 618 [NASA ADS] [CrossRef] [Google Scholar]
Bastien, P., Drissen, L., Menard, F., et al. 1988, AJ, 95, 900 [NASA ADS] [CrossRef] [Google Scholar]
Bastien, P., Vernet, E., Drissen, L., et al. 2007, in The Future of Photometric, Spectrophotometric and Polarimetric Standardization, ed. C.Sterken, ASP Conf. Ser., 364, 529 [NASA ADS] [Google Scholar]
Bazzon, A., Gisler, D., Roelfsema, R., et al. 2012, in Ground-based and Airborne Instrumentation for Astronomy IV, Proc. SPIE, 8446, 93 [Google Scholar]
Bellini, A., Anderson, J., van der Marel, R. P., et al. 2014, ApJ, 797, 115 [NASA ADS] [CrossRef] [Google Scholar]
Benisty, M., Stolker, T., Pohl, A., et al. 2017, A&A, 597, A42 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Beuzit, J.-L., Feldt, M., Dohlen, K., et al. 2008, in Ground-based and Airborne Instrumentation for Astronomy II, Proc. SPIE, 7014, 18 [Google Scholar]
Bliokh, K. Y., & Aiello, A. 2013, J. Opt., 15, 014001 [NASA ADS] [CrossRef] [Google Scholar]
Boccaletti, A., Abe, L., Baudrand, J., et al. 2008, in Adaptive Optics Systems, Proc. SPIE, 7015, 70151B [CrossRef] [Google Scholar]
Bonnefoy, M., Zurlo, A., Baudino, J. L., et al. 2016, A&A, 587, A58 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Born, M., & Wolf, E. 1999, in Principles of Optics (Cambridge: Cambridge University Press) [CrossRef] [Google Scholar]
Brandner, W., & Hormuth, F. 2016, in Astronomy at High Angular Resolution, eds. H. M. J. Boffin, G.Hussain, J.-P. Berger, & L. Schmidtobreick Astrophysics and Space Science Library, 439, 1 [NASA ADS] [CrossRef] [Google Scholar]
Breckinridge, J. B., Lam, W. S. T., & Chipman, R. A. 2015, PASP, 127, 445 [NASA ADS] [CrossRef] [Google Scholar]
Cheetham, A. C., Girard, J., Lacour, S., et al. 2016, in Optical and Infrared Interferometry and Imaging V, Proc. SPIE, 9907, 99072T [CrossRef] [Google Scholar]
Clarke, D., Stewart, B. G., Schwarz, H. E., & Brooks, A. 1983, A&A, 126, 260 [NASA ADS] [Google Scholar]
Claudi, R. U., Turatto, M., Gratton, R. G., et al. 2008, in Ground-based and Airborne Instrumentation for Astronomy II, Proc. SPIE, 7014, 70143E [CrossRef] [Google Scholar]
Close, L. M. 2016, in Adaptive Optics Systems V, Proc. SPIE. 9909, 99091E [NASA ADS] [Google Scholar]
Close, L. M., Males, J. R., Morzinski, K., et al. 2013, ApJ, 774, 94 [NASA ADS] [CrossRef] [Google Scholar]
Collett, E. 1992, Polarized Light: Fundamentals and Applications (New York: Dekker) [Google Scholar]
Cox, L. J. 1976, MNRAS, 176, 525 [NASA ADS] [Google Scholar]
Davies, R., & Kasper, M. 2012, ARA&A, 50, 305 [NASA ADS] [CrossRef] [Google Scholar]
de Juan Ovelar, M., Diamantopoulou, S., Roelfsema, R., et al. 2012, in Modeling, Systems Engineering, and Project Management for Astronomy V, Proc. SPIE, 8449, 844912 [CrossRef] [Google Scholar]
de Zeeuw, T. 2016, The Messenger, 166, 2 [NASA ADS] [Google Scholar]
Dixon, W. V. D., Davidsen, A. F., & Ferguson, H. C. 1995, ApJ, 454, L47 [NASA ADS] [CrossRef] [Google Scholar]
Dohlen, K., Langlois, M., Saisse, M., et al. 2008, in Ground-based and Airborne Instrumentation for Astronomy II, Proc. SPIE, 7014, 70143L [CrossRef] [Google Scholar]
Dohlen, K., Vigan, A., Mouillet, D., et al. 2016, Proc. SPIE, 9908, 99083D [Google Scholar]
Engler, N., Schmid, H. M., Thalmann, C., et al. 2017, A&A, 607, A90 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Ferreira, J., Dougados, C., & Cabrit, S. 2006, A&A, 453, 785 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Frank, A., Ray, T. P., Cabrit, S., et al. 2014, Protostars Planets VI, 451 [Google Scholar]
Fusco, T., Sauvage, J.-F., Petit, C., et al. 2014, in Adaptive Optics Systems IV, Proc. SPIE, 9148, 1 [Google Scholar]
Fusco, T., Sauvage, J.-F., Mouillet, D., et al. 2016, in Adaptive Optics Systems V, Proc. SPIE, 9909, 99090U [CrossRef] [Google Scholar]
Gandorfer, A. M. 1999, Opt. Eng., 38, 1402 [NASA ADS] [CrossRef] [Google Scholar]
Gandorfer, A. M., & Povel, H. P. 1997, A&A, 328, 381 [NASA ADS] [Google Scholar]
Garufi, A., Quanz, S. P., Schmid, H. M., et al. 2016, A&A, 588, A8 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Gisler, D., Feller, A., & Gandorfer, A. M. 2003, in Polarimetry in Astronomy, Proc. SPIE, 4843, 45 [NASA ADS] [CrossRef] [Google Scholar]
Gisler, D., Schmid, H. M., Thalmann, C., et al. 2004, in Ground-based Instrumentation for Astronomy, Proc. SPIE, 5492, 463 [NASA ADS] [CrossRef] [Google Scholar]
Goos, F., & Hänchen, H. 1947, Annal. Phys., 436, 333 [NASA ADS] [CrossRef] [Google Scholar]
Haniff, C. A., Scholz, M., & Tuthill, P. G. 1995, MNRAS, 276, 640 [NASA ADS] [CrossRef] [Google Scholar]
Höfner, S. 2008, A&A, 491, L1 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Höfner, S., Bladh, S., Aringer, B., & Ahuja, R. 2016, A&A, 594, A108 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Hsu, J.-C., & Breger, M. 1982, ApJ, 262, 732 [NASA ADS] [CrossRef] [Google Scholar]
Ireland, M. J., Tuthill, P. G., Davis, J., & Tango, W. 2005, MNRAS, 361, 337 [NASA ADS] [CrossRef] [Google Scholar]
Janson, M., Durkan, S., Bonnefoy, M., et al. 2018, A&A, submitted, [Google Scholar]
Joos, F. 2007, PhD Thesis, ETH Zurich [Google Scholar]
Joshi, U. C., Ganesh, S., & Baliyan, K. S. 2012, in Stellar Polarimetry: from Birth to Death, AIP Conference Proceedings, 1429, 222 [NASA ADS] [CrossRef] [Google Scholar]
Jovanovic, N., Martinache, F., Guyon, O., et al. 2015, PASP, 127, 890 [NASA ADS] [CrossRef] [Google Scholar]
Kasper, M., Beuzit, J.-L., Feldt, M., et al. 2012, The Messenger, 149, 17 [NASA ADS] [Google Scholar]
Kasper, M., Kasper, M. & Mawet, D. 2013, in Proceedings of the Third AO4ELT Conference, 8 [Google Scholar]
Keller, C. U., Schmid, H. M., Venema, L. B., et al. 2010, in Ground-based and Airborne Instrumentation for Astronomy III, Proc. SPIE, 7735, 77356G [CrossRef] [Google Scholar]
Kemp, J. C., & Barbour, M. S. 1981, PASP, 93, 521 [NASA ADS] [CrossRef] [Google Scholar]
Kervella, P., Domiciano de Souza, A., & Bendjoya, P. 2008, A&A, 484, L13 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Kervella, P., Montargès, M., Lagadec, E., et al. 2015, A&A, 578, A77 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Kervella, P., Lagadec, E., Montargès, M., et al. 2016, A&A, 585, A28 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Khouri, T., Maercker, M., Waters, L. B. F. M., et al. 2016, A&A, 591, A70 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Kuhn, J. R., Potter, D., & Parise, B. 2001, ApJ, 553, L189 [NASA ADS] [CrossRef] [Google Scholar]
Lafrenière, D., Marois, C., Doyon, R., Nadeau, D., & Artigau, É. 2007, ApJ, 660, 770 [NASA ADS] [CrossRef] [Google Scholar]
Langlois, M., Dohlen, K., Vigan, A., et al. 2014, in Ground-based and Airborne Instrumentation for Astronomy V, Proc. SPIE, 9147, 91471R [CrossRef] [Google Scholar]
Law, N. M., Mackay, C. D., Dekany, R. G., et al. 2009, ApJ, 692, 924 [NASA ADS] [CrossRef] [Google Scholar]
Liimets, T., Corradi, R. L. M., Jones, D., et al. 2018, A&A, 612, A118 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Lovis, C., Snellen, I., Mouillet, D., et al. 2017, A&A, 599, A16 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Macintosh, B., Graham, J. R., Ingraham, P., et al. 2014, Proc. Nat. Acad. Sci., 111, 12661 [NASA ADS] [CrossRef] [Google Scholar]
Maire, A.-L., Bonnefoy, M., Ginski, C., et al. 2016a, A&A, 587, A56 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Maire, A.-L., Langlois, M., Dohlen, K., et al. 2016b, in Ground-based and Airborne Instrumentation for Astronomy VI, Proc. SPIE, 9908, 990834 [CrossRef] [Google Scholar]
Malbet, F. 1996, A&AS, 115, 161 [NASA ADS] [Google Scholar]
Marchis, F., Kaasalainen, M., Hom, E. F. Y., et al. 2006, Icarus, 185, 39 [NASA ADS] [CrossRef] [PubMed] [Google Scholar]
Marois, C., Lafrenière, D., Doyon, R., Macintosh, B., & Nadeau, D. 2006, ApJ, 641, 556 [NASA ADS] [CrossRef] [Google Scholar]
Martinez Pillet, V., & Sanchez Almeida, J. 1991, A&A, 252, 861 [NASA ADS] [Google Scholar]
McLaughlin, D. E., Anderson, J., Meylan, G., et al. 2006, ApJS, 166, 249 [NASA ADS] [CrossRef] [Google Scholar]
Melnikov, S., Stute, M., & Eislöffel, J. 2018, A&A, 612, A77 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Milli, J., Mouillet, D., Mawet, D., et al. 2013, A&A, 556, A64 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Milli, J., Mouillet, D., Fusco, T., et al. 2017, Adapt. Opt. Extremely Large Tel., DOI 10.26698/AO4ELT5.0034 [Google Scholar]
Momany, Y., Saviane, I., Smette, A., et al. 2012, A&A, 537, A2 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Muto, T., Grady, C. A., Hashimoto, J., et al. 2012, ApJ, 748, L22 [NASA ADS] [CrossRef] [Google Scholar]
Norris, B. R. M., Tuthill, P. G., Ireland, M. J., et al. 2012, Nature, 484, 220 [NASA ADS] [CrossRef] [PubMed] [Google Scholar]
Ohnaka, K., Weigelt, G., & Hofmann, K.-H. 2017a, A&A, 597, A20 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Ohnaka, K., Weigelt, G., & Hofmann, K.-H. 2017b, Nature, 548, 310 [NASA ADS] [CrossRef] [Google Scholar]
Paladini, C., Klotz, D., Sacuto, S., et al. 2017, A&A, 600, A136 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Patapis, P., Kühn, J., & Schmid, H. M. 2018, in Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III, Proc. SPIE, 10706, 107065J [Google Scholar]
Perrin, M. D., Schneider, G., Duchene, G., et al. 2009, ApJ, 707, L132 [NASA ADS] [CrossRef] [Google Scholar]
Perrin, M. D., Duchene, G., Millar-Blanchaer, M., et al. 2015, ApJ, 799, 182 [NASA ADS] [CrossRef] [Google Scholar]
Povel, H.-P. 1995, Opt. Eng., 34, 1870 [NASA ADS] [CrossRef] [Google Scholar]
Povel, H., Aebersold, H., & Stenflo, J. O. 1990, Appl. Opt., 29, 1186 [NASA ADS] [CrossRef] [Google Scholar]
Pragt, J., Roelfsema, R., Gisler, D., et al. 2012, in Ground-based and Airborne Instrumentation for Astronomy IV, Proc. SPIE, 8446, 844697 [CrossRef] [Google Scholar]
Quanz, S. P., Schmid, H. M., Geissler, K., et al. 2011, ApJ, 738, 23 [NASA ADS] [CrossRef] [Google Scholar]
Ragland, S., Le Coroller, H., Pluzhnik, E., et al. 2008, ApJ, 679, 746 [NASA ADS] [CrossRef] [Google Scholar]
Rapson, V. A., Kastner, J. H., Millar-Blanchaer, M. A., & Dong, R. 2015, ApJ, 815, L26 [NASA ADS] [CrossRef] [Google Scholar]
Riaud, P., Boccaletti, A., Baudrand, J., & Rouan, D. 2003, PASP, 115, 712 [NASA ADS] [CrossRef] [Google Scholar]
Roelfsema, R., Schmid, H. M., Pragt, J., et al. 2010, in Ground-based and Airborne Instrumentation for Astronomy III, Proc. SPIE, 7735, 4 [Google Scholar]
Roelfsema, R., Gisler, D., Pragt, J., et al. 2011, in Techniques and Instrumentation for Detection of Exoplanets V, Proc. SPIE, 8151, 81510N [Google Scholar]
Roelfsema, R., Bazzon, A., Schmid, H. M., et al. 2014, in Ground-based and Airborne Instrumentation for Astronomy V, Proc. SPIE, 9147, 91473W [CrossRef] [Google Scholar]
Roelfsema, R., Bazzon, A., Schmid, H. M., et al. 2016, in Adaptive Optics Systems V, Proc. SPIE, 9909, 990927 [CrossRef] [Google Scholar]
Rouan, D., Riaud, P., Boccaletti, A., Clénet, Y., & Labeyrie, A. 2000, PASP, 112, 1479 [NASA ADS] [CrossRef] [Google Scholar]
Sauvage, J.-F., Fusco, T., Rousset, G., & Petit, C. 2007, J. Opt. Soc. Am. A, 24, 2334 [NASA ADS] [CrossRef] [Google Scholar]
Sauvage, J.-F., Fusco, T., Lamb, M., et al. 2016a, in Adaptive Optics Systems V, Proc. SPIE, 9909, 990916 [CrossRef] [Google Scholar]
Sauvage, J.-F., Fusco, T., Petit, C., et al. 2016b, J. Astron. Tel., Instrum. Syst., 2, 025003 [NASA ADS] [CrossRef] [Google Scholar]
Scarrott, S. M., Warren-Smith, R. F., Pallister, W. S., Axon, D. J., & Bingham, R. G. 1983, MNRAS, 204, 1163 [NASA ADS] [CrossRef] [Google Scholar]
Schiavon, R. P., Dalessandro, E., Sohn, S. T., et al. 2012, AJ, 143, 121 [NASA ADS] [CrossRef] [Google Scholar]
Schmid, H. M., Beuzit, J.-L., Feldt, M., et al. 2006a, in Direct Imaging of Exoplanets: Science & Techniques, eds. C. Aime, & F. Vakili, IAU Colloq., 200, 165 [NASA ADS] [Google Scholar]
Schmid, H. M., Joos, F., & Tschan, D. 2006b, A&A, 452, 657 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Schmid, H.-M., Downing, M., Roelfsema, R., et al. 2012, in Ground-based and Airborne Instrumentation for Astronomy IV, Proc. SPIE, 8446, 8 [Google Scholar]
Schmid, H. M., Bazzon, A., Milli, J., et al. 2017, A&A, 602, A53 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Schneider, G., & Silverstone, M. D. 2003, in High-Contrast Imaging for Exo-Planet Detection, eds. A. B.Schultz, Proc. SPIE, 4860, 1 [NASA ADS] [CrossRef] [Google Scholar]
Serkowski, K. 1974, in Planets, Stars, and Nebulae: Studied with Photopolarimetry, ed. T. Gehrels, IAU Colloq., 23, 135 [NASA ADS] [Google Scholar]
Serkowski, K., & Shawl, S. J. 2001, AJ, 122, 2017 [NASA ADS] [CrossRef] [Google Scholar]
Serkowski, K., Mathewson, D. S., & Ford, V. L. 1975, ApJ, 196, 261 [NASA ADS] [CrossRef] [Google Scholar]
Sivaramakrishnan, A., Koresko, C. D., Makidon, R. B., Berkefeld, T., & Kuchner, M. J. 2001, ApJ, 552, 397 [NASA ADS] [CrossRef] [Google Scholar]
Soummer, R., Pueyo, L., & Larkin, J. 2012, ApJ, 755, L28 [NASA ADS] [CrossRef] [Google Scholar]
Stenflo, J. O. 1996, Nature, 382, 588 [NASA ADS] [CrossRef] [Google Scholar]
Stenflo, J. O., & Keller, C. U. 1997, A&A, 321, 927 [NASA ADS] [Google Scholar]
Stolker, T., Dominik, C., Avenhaus, H., et al. 2016, A&A, 595, A113 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Thalmann, C., Schmid, H. M., Boccaletti, A., et al. 2008, in Ground-based and Airborne Instrumentation for Astronomy II, Proc. SPIE, 7014, 3 [Google Scholar]
Thalmann, C., Mulders, G. D., Janson, M., et al. 2015, ApJ, 808, L41 [NASA ADS] [CrossRef] [Google Scholar]
Tinbergen, J. 1979, A&AS, 35, 325 [NASA ADS] [Google Scholar]
Tinbergen, J. 2007, PASP, 119, 1371 [NASA ADS] [CrossRef] [Google Scholar]
van Belle, G. T., Dyck, H. M., Benson, J. A., & Lacasse, M. G. 1996, AJ, 112, 2147 [NASA ADS] [CrossRef] [Google Scholar]
van Boekel, R., Henning, T., Menu, J., et al. 2017, ApJ, 837, 132 [NASA ADS] [CrossRef] [Google Scholar]
van Holstein, R. G., Snik, F., Girard, J. H., et al. 2010, in Techniques and Instrumentation for Detection of Exoplanets VIII, Proc. SPIE, 10400, 1040015 [Google Scholar]
Vernazza, P., Marchis, F., Carry, B., Marsset, M., & Hanus, J. 2008, in European Planetary Science Congress (EPSC2017), 11 [Google Scholar]
Vigan, A., Langlois, M., Dohlen, K., et al. 2014, in Ground-based and Airborne Instrumentation for Astronomy V, Proc. SPIE, 9147, 91474T [CrossRef] [Google Scholar]
Vigan, A., Bonnefoy, M., Ginski, C., et al. 2016, A&A, 587, A55 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]
Whittet, D. C. B., Martin, P. G., Hough, J. H., et al. 1992, ApJ, 386, 562 [NASA ADS] [CrossRef] [Google Scholar]
Wildi, F., Mouillet, D., Beuzit, J.-L., et al. 2009, in Techniques and Instrumentation for Detection of Exoplanets IV, Proc. SPIE, 7440, 74400Q [CrossRef] [Google Scholar]
Wildi, F. P., Michaud, B., Crausaz, M., et al. 2010, in Ground-based and Airborne Instrumentation for Astronomy III, Proc. SPIE, 7735, 77352V [CrossRef] [Google Scholar]
Zurlo, A., Vigan, A., Galicher, R., et al. 2016, A&A, 587, A57 [NASA ADS] [CrossRef] [EDP Sciences] [Google Scholar]

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.