Search

Your search keyword '"N. Gorius"' showing total 20 results
Start Over Author "N. Gorius" Language english
20 results on '"N. Gorius"'

1. A hexagon in Saturn’s northern stratosphere surrounding the emerging summertime polar vortex

Author

L. N. Fletcher, G. S. Orton, J. A. Sinclair, S. Guerlet, P. L. Read, A. Antuñano, R. K. Achterberg, F. M. Flasar, P. G. J. Irwin, G. L. Bjoraker, J. Hurley, B. E. Hesman, M. Segura, N. Gorius, A. Mamoutkine, and S. B. Calcutt

Subjects
Science
Abstract

The Cassini spacecraft has provided an unprecedented characterisation of seasonal changes on Saturn. Here the authors describe the development of a warm polar vortex in Saturn’s northern summer, and show that the hexagon extends hundreds of kilometres from the troposphere into the stratosphere.

Published
2018
Full Text
View/download PDF

3. Temperature and Chemical Species Distributions in the Middle Atmosphere Observed during Titan's Late Northern Spring to Early Summer

Author

S Vinatier, C Mathe, B Bezard, J Vatant d’Ollone, S Lebonnois, C Dauphin, F M Flasar, R K Achterberg, B Seignovert, M Sylvestre, N A Teanby, N Gorius, A Mamoutkine, E Guandique, and D E Jennings

Subjects
Astrophysics
Abstract

We present a study of the seasonal evolution of Titan’s thermal field and distributions of haze, C2H2, C2H4, C2H6, CH3C2H, C3H8, C4H2, C6H6, HCN, and HC3N from March 2015 (Ls = 66°) to September 2017 (Ls = 93°) (i.e., from the last third of northern spring to early summer). We analyzed thermal emission of Titan’s atmosphere acquired by the Cassini Composite Infrared Spectrometer with limb and nadir geometry to retrieve the stratospheric and mesospheric temperature and mixing ratios pole-to-pole meridional cross sections from 5 mbar to 50 μbar (120–650 km). The southern stratopause varied in a complex way and showed a global temperature increase from 2015 to 2017 at high-southern latitudes. Stratospheric southern polar temperatures, which were observed to be as low as 120 K in early 2015 due to the polar night, showed a 30 K increase (at 0.5 mbar) from March 2015 to May 2017 due to adiabatic heating in the subsiding branch of the global overturning circulation. All photochemical compounds were enriched at the south pole by this subsidence. Polar cross sections of these enhanced species, which are good tracers of the global dynamics, highlighted changes in the structure of the southern polar vortex. These high enhancements combined with the unusually low temperatures (<120 K) of the deep stratosphere resulted in condensation at the south pole between 0.1 and 0.03 mbar (240–280 km) of HCN, HC3N, C6H6 and possibly C4H2 in March 2015 (Ls = 66°). These molecules were observed to condense deeper with increasing distance from the south pole. At high-northern latitudes, stratospheric enrichments remaining from the winter were observed below 300 km between 2015 and May 2017 (Ls = 90°) for all chemical compounds and up to September 2017 (Ls = 93°) for C2H2, C2H4, CH3C2H, C3H8, and C4H2. In September 2017, these local enhancements were less pronounced than earlier for C2H2, C4H2, CH3C2H, HC3N, and HCN, and were no longer observed for C2H6 and C6 H6, which suggests a change in the northern polar dynamics near the summer solstice. These enhancements observed during the entire spring may be due to confinement of this enriched air by a small remaining winter circulation cell that persisted in the low stratosphere up to the northern summer solstice, according to predictions of the Institut Pierre Simon Laplace Titan Global Climate Model (IPSL Titan GCM). In the mesosphere we derived a depleted layer in C2H2, HCN, and C2H6 from the north pole to mid-southern latitudes, while C4H2, C3H4, C2H4, and HC3N seem to have been enriched in the same region. In the deep stratosphere, all molecules except C2H4 were depleted due to their condensation sink located deeper than 5 mbar outside the southern polar vortex. HCN, C4H2, and CH3C2H volume mixing ratio cross section contours showed steep slopes near the mid-latitudes or close to the equator, which can be explained by upwelling air in this region. Upwelling is also supported by the cross section of the C2H4 (the only molecule not condensing among those studied here) volume mixing ratio observed in the northern hemisphere. We derived the zonal wind velocity up to mesospheric levels from the retrieved thermal field. We show that zonal winds were faster and more confined around the south pole in 2015 (Ls = 67−72°) than later. In 2016, the polar zonal wind speed decreased while the fastest winds had migrated toward low-southern latitudes.

Published
2020
Full Text
View/download PDF

4. The unexpected surface of asteroid (101955) Bennu

Author

D. S. Lauretta, D. N. DellaGiustina, C. A. Bennett, D. R. Golish, K. J. Becker, S. S. Balram-Knutson, O. S. Barnouin, T. L. Becker, W. F. Bottke, W. V. Boynton, H. Campins, H. C. Connolly Jr, C. Y. Drouet d’Aubigny, J. P. Dworkin, J. P. Emery, H. L. Enos, V. E. Hamilton, C. W. Hergenrother, E. S. Howell, M. R. M. Izawa, H. H. Kaplan, M. C. Nolan, B. Rizk, H. L. Roper, D. J. Scheeres, P. H. Smith, K. J. Walsh, C. W. V. Wolner, D. E. Highsmith, J. Small, D. Vokrouhlický, N. E. Bowles, E. Brown, K. L. Donaldson Hanna, T. Warren, C. Brunet, R. A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D. L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C. M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, L. McGraw, R. Ghent, R. P. Binzel, M. M. Al Asad, C. L. Johnson, L. Philpott, H. C. M. Susorney, E. A. Cloutis, R. D. Hanna, F. Ciceri, A. R. Hildebrand, E.-M. Ibrahim, L. Breitenfeld, T. Glotch, A. D. Rogers, B. E. Clark, S. Ferrone, C. A. Thomas, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J. R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M. K. Crombie, C. Lantz, J. de Leon, J. Licandro, J. L. Rizos Garcia, S. Clemett, K. Thomas-Keprta, S. Van wal, M. Yoshikawa, J. Bellerose, S. Bhaskaran, C. Boyles, S. R. Chesley, C. M. Elder, D. Farnocchia, A. Harbison, B. Kennedy, A. Knight, N. Martinez-Vlasoff, N. Mastrodemos, T. McElrath, W. Owen, R. Park, B. Rush, L. Swanson, Y. Takahashi, D. Velez, K. Yetter, C. Thayer, C. Adam, P. Antreasian, J. Bauman, C. Bryan, B. Carcich, M. Corvin, J. Geeraert, J. Hoffman, J. M. Leonard, E. Lessac-Chenen, A. Levine, J. McAdams, L. McCarthy, D. Nelson, B. Page, J. Pelgrift, E. Sahr, K. Stakkestad, D. Stanbridge, D. Wibben, B. Williams, K. Williams, P. Wolff, P. Hayne, D. Kubitschek, M. A. Barucci, J. D. P. Deshapriya, S. Fornasier, M. Fulchignoni, P. Hasselmann, F. Merlin, A. Praet, E. B. Bierhaus, O. Billett, A. Boggs, B. Buck, S. Carlson-Kelly, J.Cerna, K. Chaffin, E. Church, M. Coltrin, J. Daly, A. Deguzman, R. Dubisher, D. Eckart, D. Ellis, P. Falkenstern, A. Fisher, M. E. Fisher, P. Fleming, K. Fortney, S. Francis, S. Freund, S. Gonzales, P. Haas, A. Hasten, D. Hauf, A. Hilbert, D. Howell, F. Jaen, N. Jayakody, M. Jenkins, K. Johnson, M. Lefevre, H. Ma, C. Mario, K. Martin, C. May, M. McGee, B. Miller, C. Miller, G. Miller, A. Mirfakhrai, E. Muhle, C. Norman, R. Olds, C. Parish, M. Ryle, M. Schmitzer, P. Sherman, M. Skeen, M. Susak, B. Sutter, Q. Tran, C. Welch, R. Witherspoon, J. Wood, J. Zareski, M. Arvizu-Jakubicki, E. Asphaug, E. Audi, R.-L. Ballouz, R. Bandrowski, S. Bendall, H. Bloomenthal, D. Blum, J. Brodbeck, K. N. Burke, M. Chojnacki, A. Colpo, J. Contreras, J. Cutts, D. Dean, B. Diallo, D. Drinnon, K. Drozd, R. Enos, C. Fellows, T. Ferro, M. R. Fisher, G. Fitzgibbon, M. Fitzgibbon, J. Forelli, T. Forrester, I. Galinsky, R. Garcia, A. Gardner, N. Habib, D. Hamara, D. Hammond, K. Hanley, K. Harshman, K. Herzog, D. Hill, C. Hoekenga, S. Hooven, E. Huettner, A. Janakus, J. Jones, T. R. Kareta, J. Kidd, K. Kingsbury, L. Koelbel, J. Kreiner, D. Lambert, C. Lewin, B. Lovelace, M. Loveridge, M. Lujan, C. K. Maleszewski, R. Malhotra, K. Marchese, E. McDonough, N. Mogk, V. Morrison, E. Morton, R. Munoz, J. Nelson, J. Padilla, R. Pennington, A. Polit, N. Ramos, V. Reddy, M. Riehl, S. Salazar, S. R. Schwartz, S. Selznick, N. Shultz, S. Stewart, S. Sutton, T. Swindle, Y. H. Tang, M. Westermann, D. Worden, T. Zega, Z. Zeszut, A. Bjurstrom, L. Bloomquist, C. Dickinson, E. Keates, J. Liang, V. Nifo, A. Taylor, F. Teti, M. Caplinger, H. Bowles, S. Carter, S. Dickenshied, D. Doerres, T. Fisher, W. Hagee, J. Hill, M. Miner, D. Noss, N. Piacentine, M. Smith, A. Toland, P. Wren, M. Bernacki, D. Pino Munoz, S.-i. Watanabe, S. A. Sandford, A. Aqueche, B. Ashman, M. Barker, A. Bartels, K. Berry, B. Bos, R. Burns, A. Calloway, R. Carpenter, N. Castro, R. Cosentino, J. Donaldson, J. Elsila Cook, C. Emr, D. Everett, D. Fennell, K. Fleshman, D. Folta, D. Gallagher, J. Garvin, K. Getzandanner, D. Glavin, S. Hull, K. Hyde, H. Ido, A. Ingegneri, N. Jones, P. Kaotira, L. F. Lim, A. Liounis, C. Lorentson, D. Lorenz, J. Lyzhoft, E. M. Mazarico, R. Mink, W. Moore, M. Moreau, S. Mullen, J. Nagy, G. Neumann, J. Nuth, D. Poland, D. C. Reuter, L. Rhoads, S. Rieger, D. Rowlands, D. Sallitt, A. Scroggins, G. Shaw, A. A. Simon, J. Swenson, P. Vasudeva, M. Wasser, R. Zellar, J. Grossman, G. Johnston, M. Morris, J. Wendel, A. Burton, L. P. Keller, L. Mcnamara, S. Messenger, K. Messenger, A. Nguyen, K. Righter, E. Queen, K. Bellamy, K. Dill, S. Gardner, M. Giuntini, B. Key, J. Kissell, D. Patterson, D. Vaughan, B. Wright, R. W. Gaskell, L. Le Corre, J.-Y. Li, J. L. Molaro, E. E. Palmer, M. A. Siegler, P. Tricarico, J. R. Weirich, X.-D. Zou, T. Ireland, K. Tait, P. Bland, S. Anwar, N. Bojorquez-Murphy, P. R. Christensen, C. W. Haberle, G. Mehall, K. Rios, I. Franchi, B. Rozitis, C. B. Beddingfield, J. Marshall, D. N. Brack, A. S. French, J. W. McMahon, E. R. Jawin, T. J. McCoy, S. Russell, M. Killgore, J. L. Bandfield, B. C. Clark, M. Chodas, M. Lambert, R. A. Masterson, M. G. Daly, J. Freemantle, J. A. Seabrook, K. Craft, R. T. Daly, C. Ernst, R. C. Espiritu, M. Holdridge, M. Jones, A. H. Nair, L. Nguyen, J. Peachey, M. E. Perry, J. Plescia, J. H. Roberts, R. Steele, R. Turner, J. Backer, K. Edmundson, J. Mapel, M. Milazzo, S. Sides, C. Manzoni, B. May, M. Delbo, G. Libourel, P. Michel, A. Ryan, F. Thuillet, and B. Marty

Subjects
Astronomy, Exobiology
Abstract

NASA’S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine—that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu’s global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5,6,7,8,9,10,11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid’s properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu’s thermal inertia12 and radar polarization ratios13—which indicated a generally smooth surface covered by centimetre-scale particles—resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.

Published
2019
Full Text
View/download PDF

5. The operational environment and rotational acceleration of asteroid (101955) Bennu from OSIRIS-REx observations

Author

C. W. Hergenrother, C. K. Maleszewski, M. C. Nolan, J.-Y. Li, C. Y. Drouet d’Aubigny, F. C. Shelly, E. S. Howell, T. R. Kareta, M. R. M. Izawa, M. A. Barucci, E. B. Bierhaus, S. R. Chesley, B. E. Clark, E. J. Christensen, D. N. DellaGiustina, S. Fornasier, D. R. Golish, C. M. Hartzell, B. Rizk, D. J. Scheeres, P. H. Smith, X.-D. Zou, D. S. Lauretta, Jason Peter Dworkin, D.E. Highsmith, J. Small, D. Vokrouhlický, N.E. Bowles, E. Brown, K.L. Donaldson Hanna, T. Warren, C. Brunet, R.A. Chicoine, S. Desjardins, D. Gaudreau, T. Haltigin, S. Millington-Veloza, A. Rubi, J. Aponte, N. Gorius, A. Lunsford, B. Allen, J. Grindlay, D. Guevel, D. Hoak, J. Hong, D.L. Schrader, J. Bayron, O. Golubov, P. Sánchez, J. Stromberg, M. Hirabayashi, C.M. Hartzell, S. Oliver, M. Rascon, A. Harch, J. Joseph, S. Squyres, D. Richardson, J.P. Emery, L. McGraw, R. Ghent, R.P. Binzel, M.M. Al Asad, C.L. Johnson, L. Philpott, H.C.M. Susorney, E.A. Cloutis, R.D. Hanna, H.C. Connolly Jr, F. Ciceri, A.R. Hildebrand, E.-M. Ibrahim, L. Breitenfeld, T. Glotch, A.D. Rogers, B.E. Clark, S. Ferrone, C.A. Thomas, H. Campins, Y. Fernandez, W. Chang, A. Cheuvront, D. Trang, S. Tachibana, H. Yurimoto, J.R. Brucato, G. Poggiali, M. Pajola, E. Dotto, E. Mazzotta Epifani, M.K. Crombie, C. Lantz, M.R.M. Izawa, J. de Leon, J. Licandro, J.L.Rizos Garcia, S. Clemett, K. Thomas-Keprta, S. Van wal, M. Yoshikawa, J. Bellerose, S. Bhaskaran, C. Boyles, S.R. Chesley, C.M. Elder, D. Farnocchia, A. Harbison, B. Kennedy, A. Knight, N. Martinez-Vlasoff, N. Mastrodemos, T. McElrath, W. Owen, R. Park, B. Rush, L. Swanson, Y. Takahashi, D. Velez, K. Yetter, C. Thayer, C. Adam, P. Antreasian, J. Bauman, C. Bryan, B. Carcich, M. Corvin, J. Geeraert, J. Hoffman, J.M. Leonard, E. Lessac-Chenen, A. Levine, J. McAdams, L. McCarthy, D. Nelson, B. Page, J. Pelgrift, E. Sahr, K. Stakkestad, D. Stanbridge, D. Wibben, B. Williams, K. Williams, P. Wolff, P. Hayne, D. Kubitschek, M.A. Barucci, J.D.P. Deshapriya, M. Fulchignoni, P. Hasselmann, F. Merlin, A. Praet, E.B. Bierhaus, O. Billett, A. Boggs, B. Buck, S. Carlson-Kelly, J. Cerna, K. Chaffin, E. Church, M. Coltrin, J. Daly, A. Deguzman, R. Dubisher, D. Eckart, D. Ellis, P. Falkenstern, A. Fisher, M.E. Fisher, P. Fleming, K. Fortney, S. Francis, S. Freund, S. Gonzales, P. Haas, A. Hasten, D. Hauf, A. Hilbert, D. Howell, F. Jaen, N. Jayakody, M. Jenkins, K. Johnson, M. Lefevre, H. Ma, C. Mario, K. Martin, C. May, M. McGee, B. Miller, C. Miller, G. Miller, A. Mirfakhrai, E. Muhle, C. Norman, R. Olds, C. Parish, M. Ryle, M. Schmitzer, P. Sherman, M. Skeen, M. Susak, B. Sutter, Q. Tran, C. Welch, R. Witherspoon, J. Wood, J. Zareski, M. Arvizu-Jakubicki, E. Asphaug, E. Audi, R.-L. Ballouz, R. Bandrowski, K.J. Becker, T.L. Becker, S. Bendall, C.A. Bennett, H. Bloomenthal, D. Blum, W.V. Boynton, J. Brodbeck, K.N. Burke, M. Chojnacki, A. Colpo, J. Contreras, J. Cutts, C. Y. Drouet d'Aubigny, D. Dean, D.N. DellaGiustina, B. Diallo, D. Drinnon, K. Drozd, H.L. Enos, R. Enos, C. Fellows, T. Ferro, M.R. Fisher, G. Fitzgibbon, M. Fitzgibbon, J. Forelli, T. Forrester, I. Galinsky, R. Garcia, A. Gardner, D.R. Golish, N. Habib, D. Hamara, D. Hammond, K. Hanley, K. Harshman, C.W. Hergenrother, K. Herzog, D. Hill, C. Hoekenga, S. Hooven, E.S. Howell, E. Huettner, A. Janakus, J. Jones, T.R. Kareta, J. Kidd, K. Kingsbury, S.S. Balram-Knutson, L. Koelbel, J. Kreiner, D. Lambert, D.S. Lauretta, C. Lewin, B. Lovelace, M. Loveridge, M. Lujan, C.K. Maleszewski, R. Malhotra, K. Marchese, E. McDonough, N. Mogk, V. Morrison, E. Morton, R. Munoz, J. Nelson, M.C. Nolan, J. Padilla, R. Pennington, A. Polit, N. Ramos, V. Reddy, M. Riehl, Y.H. Tang, M. Westermann, C.W.V. Wolner, D. Worden, T. Zega, Z. Zeszut, A. Bjurstrom, L. Bloomquist, C. Dickinson, E. Keates, J. Liang, V. Nifo, A. Taylor, F. Teti, M. Caplinger, H. Bowles, S. Carter, S. Dickenshied, D. Doerres, T. Fisher, W. Hagee, J. Hill, M. Miner, D. Noss, N. Piacentine, M. Smith, A. Toland, P. Wren, M. Bernacki, D. Pino Munoz, S.-i. Watanabe, S. A. Sandford, A. Aqueche, B. Ashman, M. Barker, A. Bartels, K. Berry, B. Bos, R. Burns, A. Calloway, R. Carpenter, N. Castro, R. Cosentino, J. Donaldson, J.P. Dworkin, J. Elsila Cook, C. Emr, D. Everett, D. Fennell, K. Fleshman, D. Folta, D. Gallagher, J. Garvin, K. Getzandanner, D. Glavin, S. Hull, K. Hyde, H. Ido, A. Ingegneri, N. Jones, P. Kaotira, L.F. Lim, A. Liounis, C. Lorentson, D. Lorenz, J. Lyzhoft, E.M. Mazarico, R. Mink, W. Moore, M. Moreau, S. Mullen, J. Nagy, G. Neumann, J. Nuth, D. Poland, D.C. Reuter, L. Rhoads, S. Rieger, D. Rowlands, D. Sallitt, A. Scroggins, G. Shaw, A.A. Simon, J. Swenson, P. Vasudeva, M. Wasser, R. Zellar, J. Grossman, G. Johnston, M. Morris, J. Wendel, A. Burton, L.P. Keller, L. McNamara, S. Messenger, K. Nakamura-Messenger, A. Nguyen, K. Righter, E. Queen, K. Bellamy, K. Dill, S. Gardner, M. Giuntini, B. Key, J. Kissell, D. Patterson, D. Vaughan, B. Wright, R.W. Gaskell, L. Le Corre, J.L. Molaro, E.E. Palmer, M.A. Siegler, P. Tricarico, J.R. Weirich, T. Ireland, K. Tait, P. Bland, S. Anwar, A.S. French, J.W. McMahon, D.J. Scheeres, E.R. Jawin, T.J. McCoy, S. Russell, M. Killgore, W.F. Bottke, V.E. Hamilton, H.H. Kaplan, K.J. Walsh, J.L. Bandfield, B.C. Clark, M. Chodas, M. Lambert, R.A. Masterson, M.G. Daly, J. Freemantle, J.A. Seabrook, O.S. Barnouin, K. Craft, R.T. Daly, C. Ernst, R.C. Espiritu, M. Holdridge, M. Jones, A.H. Nair, L. Nguyen, J. Peachey, M.E. Perry, J. Plescia, J.H. Roberts, R. Steele, R. Turner, J. Backer, K. Edmundson, J. Mapel, M. Milazzo, S. Sides, C. Manzoni, B. May, M. Delbo’, G. Libourel, P. Michel, A. Ryan, F. Thuillet, and B. Marty

Subjects
Geosciences (General)
Abstract

During its approach to asteroid (101955) Bennu, NASA’s Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer (OSIRIS-REx) spacecraft surveyed Bennu’s immediate environment, photometric properties, and rotation state. Discovery of a dusty environment, a natural satellite, or unexpected asteroid characteristics would have had consequences for the mission’s safety and observation strategy. Here we show that spacecraft observations during this period were highly sensitive to satellites (sub-meter scale) but reveal none, although later navigational images indicate that further investigation is needed. We constrain average dust production in September 2018 from Bennu’s surface to an upper limit of 150 g/s averaged over 34 min. Bennu’s disk-integrated photometric phase function validates measurements from the pre-encounter astronomical campaign. We demonstrate that Bennu’s rotation rate is accelerating continuously at 3.63 ± 0.52 × 10^(–6) degrees/sq. day, likely due to the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, with evolutionary implications.

Published
2019
Full Text
View/download PDF

6. Author Correction: Shape of (101955) Bennu indicative of a rubble pile with internal stiffness

Author

M. Lefevre, Aaron S. Burton, Carina Bennett, J. A. Mapel, Renu Malhotra, Peter Fleming, J. McAdams, N. Mogk, R. L. Ballouz, P. H. Smith, V. Nifo, C. K. Maleszewski, Timothy D. Swindle, E. Dotto, Stephen R. Schwartz, C. May, J. Bayron, D. Patterson, D. Guevel, Ellen S. Howell, Humberto Campins, J. Kissell, E. Brown, J. Wood, E. Muhle, John Robert Brucato, J. Small, B. Miller, Oleksiy Golubov, R. Pennington, K. Harshman, J. Nelson, Catherine Elder, M. McGee, R. Burns, J. Contreras, S. Hull, D. Kubitschek, D. Noss, Andrew J. Liounis, J. Backer, B. May, G. Fitzgibbon, J. Donaldson, D. Worden, Bashar Rizk, R. Witherspoon, Catherine L. Johnson, Erica Jawin, G. Shaw, A. Aqueche, Dolores H. Hill, D. Folta, S. Ferrone, M. Lujan, Giovanni Poggiali, B. G. Williams, S. Selznick, Melissa A. Morris, K. Rios, Sara S. Russell, D. Lambert, J. Hong, Jeffrey B. Plescia, H. Bloomenthal, D. Drinnon, Olivier S. Barnouin, Derek S. Nelson, Amanda E. Toland, Michael C. Moreau, J. A. Seabrook, K. Dill, A. Mirfakhrai, K. Hyde, J. D. P. Deshapriya, Hannah Kaplan, Timothy P. McElrath, Juliette I. Brodbeck, N. Ramos, S. Stewart, James B. Garvin, Sei-ichiro Watanabe, M. Arvizu-Jakubicki, Jason P. Dworkin, Matthew A. Siegler, Collin Lewin, Masatoshi Hirabayashi, L. Bloomquist, S. Gardner, Keiko Nakamura-Messenger, A. H. Nair, M. Schmitzer, P. Haas, Julie Bellerose, Dolan E. Highsmith, L. Koelbel, C. C. Lorentson, J. Zareski, E. Queen, S. R. Chesley, Philip A. Bland, A. Cheuvront, V. E. Hamilton, Ronald G. Mink, N. Mastrodemos, H. C. Connolly, K. Bellamy, M. Killgore, A. Gardner, Y. Takahashi, M. Lambert, R. C. Espiritu, Z. Zeszut, E. T. Morton, Kevin J. Walsh, Timothy D. Glotch, M. Skeen, Brian Kennedy, Matthew R.M. Izawa, G. Neumann, F. Teti, D. Doerres, A. Hasten, F. Ciceri, D. Howell, A. Deguzman, J. Nagy, D. Vaughan, H. Ma, C. Lantz, D. N. Brack, David K. Hammond, Erwan Mazarico, Leilah K. McCarthy, L. Rhoads, Kathleen L. Craft, C. Welch, Jay W. McMahon, C. L. Parish, D. C. Reuter, M. Giuntini, N. Castro, Clive Dickinson, J. Kreiner, K. Kingsbury, S. Dickenshied, Joseph A. Nuth, Alan R. Hildebrand, Erik Asphaug, H. Ido, Eric M. Sahr, A. Harbison, Arlin E. Bartels, T. Forrester, D. Eckart, R. Bandrowski, Michael K. Barker, Robert Gaskell, J. Wendel, S. Freund, Marc Bernacki, Ryan S. Park, A. Taylor, E. B. Bierhaus, S. Millington-Veloza, J. Stromberg, L. B. Breitenfeld, K. Stakkestad, D. Ellis, Timothy J. McCoy, M. Susak, Richard G. Cosentino, C. Manzoni, Hisayoshi Yurimoto, C. Drouet d'Aubigny, A. Bjurstrom, Masako Yoshikawa, S. Francis, J. Peachey, J. Geeraert, K. Marchese, O. Billett, M. Rascon, F. Jaen, B. Diallo, Martin Miner, Kris J. Becker, E. Mazzotta Epifani, Florian Thuillet, A. Knight, James H. Roberts, Pasquale Tricarico, Edward A. Cloutis, T. Fisher, Dale Stanbridge, A. Colpo, Osiris-Rex Team, S. Gonzales, Q. Tran, M. K. Crombie, John Marshall, N. Bojorquez-Murphy, David Vokrouhlický, Allen W. Lunsford, H. Bowles, K. L. Edmundson, R. A. Masterson, Peter G. Antreasian, N. Gorius, Benjamin Rozitis, D. Pino Muñoz, S. Carlson-Kelly, C. Thayer, J. Elsila Cook, B. C. Clark, N. Piacentine, José C. Aponte, M. Al Asad, M. A. Barucci, D. Blum, P. Falkenstern, Neil Bowles, Matthew Chojnacki, J. M. Leonard, J. Daly, K. Yetter, M. R. Fisher, Jeffrey N. Grossman, A. Boggs, N. Jayakody, Cristina A. Thomas, C.M. Ernst, Namrah Habib, J. N. Kidd, R. J. Steele, Andrew B. Calloway, Andrew Ryan, Kimberly T. Tait, Paul O. Hayne, J. Y. Li, K. L. Berry, William V. Boynton, Yanga R. Fernandez, D. A. Lorenz, M. Wasser, Daniel J. Scheeres, K. Fortney, A. Scroggins, B. Allen, B. Sutter, T. Ferro, Jonathan Joseph, Derek C. Richardson, D. Hoak, Brian Carcich, W. Chang, P. Wren, C. Boyles, Kaj E. Williams, B. Marty, J. Liang, J. Hoffman, A. Harch, Daniel R. Wibben, Jamie Molaro, S. Rieger, R. Enos, C. W. Hergenrother, Stephen R. Sutton, J. Grindlay, E. J. Lessac-Chenen, E. Huettner, C. Norman, P. Sherman, L. Swanson, M. Coltrin, S. Van wal, B. Buck, A. Fisher, Kevin Righter, Brian Rush, David D. Rowlands, Lauren McGraw, A. Levine, K. Drozd, D. Gaudreau, A. Nguyen, S. Sides, M. Chodas, R. Dubisher, B. Ashman, Michael Caplinger, Amy Simon, W. Moore, S. S. Balram-Knutson, R. Carpenter, S. Fornasier, Shogo Tachibana, Russell Turner, Ian A. Franchi, Trevor Ireland, Chloe B. Beddingfield, D. F. Everett, M. Corvin, Lindsay P. Keller, Tammy L. Becker, S. Carter, J. L. Rizos Garcia, Mark E. Perry, E. Keates, Michael C. Nolan, P. Vasudeva, C. Fellows, K. Herzog, Mark A. Jenkins, J. R. Weirich, J. Swenson, D. R. Golish, Davide Farnocchia, Lydia C. Philpott, Rebecca R. Ghent, Hannah C.M. Susorney, S. W. Squyres, Pedro Hasselmann, J. Hill, Thomas J. Zega, B. Key, Marco Delbo, A. S. French, P. Sánchez, A. Hilbert, J. Y. Pelgrift, R. P. Binzel, L. McNamara, Vishnu Reddy, Michael Daly, Scott Messenger, Daniella DellaGiustina, Maurizio Pajola, Charles Brunet, Joshua L. Bandfield, J. Padilla, A. Janakus, M. Moreau, R. Garcia, R. A. Chicoine, P. Michel, P. Kaotira, K. S. Johnson, J. Forelli, G. Miller, K. Martin, I. Galinsky, S. Desjardins, Naru Hirata, Christine Hartzell, M. L. Jones, S. Hooven, D. Velez, R. Munoz, Carolyn M. Ernst, C. Emr, N. Martinez-Vlasoff, S. Bendall, R. Zellar, E. Church, Theodore Kareta, T. Warren, P. Wolff, V. Morrison, C. Bryan, S. Bhaskaran, N. Jones, D. Hauf, Jeremy Bauman, R. T. Daly, R. Olds, M. M. Westermann, D. K. Hamara, E. Audi, G. Johnston, Eric Palmer, Courtney Mario, Daniel P. Glavin, T. Haltigin, J. Cutts, Javier Licandro, Xiao-Duan Zou, H. L. Roper, Gregory A. Neumann, William M. Owen, S. Sugita, Y. H. Tang, Kevin Burke, H. L. Enos, D. Gallagher, William F. Bottke, K. Getzandanner, Philip R. Christensen, C. W. V. Wolner, K. Fleshman, D. Poland, J. P. Emery, M.M. Riehl, D. Fennell, D. Sallitt, A. D. Rogers, M. Fitzgibbon, John H. Jones, S. Mullen, S. Salazar, S. Oliver, A. T. Polit, J. Cerna, A. Praet, Mark E. Holdridge, E. M. Ibrahim, Coralie D. Adam, J. de León, Christopher J. Miller, M. Ryle, J. Lyzhoft, M. Loveridge, C. Hoekenga, Brent J. Bos, S. Anwar, K. Chaffin, Devin L. Schrader, B. Lovelace, Romy D. Hanna, C. D. Adam, G. L. Mehall, K. L. Donaldson Hanna, F. Merlin, B. Wright, Guy Libourel, L. F. Lim, N. Shultz, Dante S. Lauretta, K. Hanley, Beth E. Clark, L. Le Corre, K. Thomas-Keprta, Moses Milazzo, W. Hagee, B. Page, M. Fisher, E. McDonough, D. Trang, S. Clemett, A. Rubi, A. Ingegneri, Scott A. Sandford, D. Dean, J. Freemantle, Michael D. Smith, Christopher W. Haberle, L. Nguyen, M. Fulchignoni, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), MINES ParisTech - École nationale supérieure des mines de Paris, Université Paris sciences et lettres (PSL), Centre de Mise en Forme des Matériaux (CEMEF), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS]Physics [physics], 010504 meteorology & atmospheric sciences, Rubble, Stiffness, engineering.material, 010502 geochemistry & geophysics, 01 natural sciences, [SDU]Sciences of the Universe [physics], engineering, medicine, General Earth and Planetary Sciences, Geotechnical engineering, medicine.symptom, Pile, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Geology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

International audience

Published
2020

7. Advanced Net Flux Radiometer for the Ice Giants

Author

Dat Q. Tran, Tilak Hewagama, R. K. Achterberg, Patrick G. J. Irwin, Amy Simon, S. B. Calcutt, M. Roos-Serote, Shahid Aslam, N. Gorius, G. Quilligan, Geronimo Villanueva, V. Cottini, and Conor A. Nixon

Subjects
Physics, Radiometer, 010504 meteorology & atmospheric sciences, business.industry, Uranus, Astronomy and Astrophysics, Spectral bands, 01 natural sciences, Thermopile, Wavelength, Radiation flux, Optics, Space and Planetary Science, Neptune, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, business, 010303 astronomy & astrophysics, Ice giant, 0105 earth and related environmental sciences
Abstract

The design of an advanced Net Flux Radiometer (NFR), for inclusion as a payload on a future Ice Giants probe mission, is given. The Ice Giants NFR (IG-NFR) will measure the upward and downward radiation flux (hence net radiation flux), in seven spectral bands, spanning the range from solar to far infra-red wavelengths, each with a 5° Field-Of-View (FOV) and in five sequential view angles (±80°, ±45°, and 0°) as a function of altitude. IG-NFR measurements within either Uranus or Neptune’s atmospheres, using dedicated spectral filter bands will help derive radiative heating and cooling profiles, and will significantly contribute to our understanding of the planet’s atmospheric heat balance and structure, tropospheric 3-D flow, and compositions and opacities of the cloud layers. The IG-NFR uses an array of non-imaging Winston cones integrated to a matched thermopile detector Focal Plane Assembly (FPA), with individual bandpass filters, housed in a diamond windowed vacuum micro-vessel. The FPA thermopile detector signals are read out in parallel mode, amplified and processed by a multi-channel digitizer application specific integrated circuit (MCD ASIC) under field programmable gate array (FPGA) control. The vacuum micro-vessel rotates providing chopping between FOV’s of upward and downward radiation fluxes. This unique design allows for small net flux measurements in the presence of large ambient fluxes and rapidly changing ambient temperatures during the probe descent to ≥10 bar pressure.

Published
2020

8. Poster-PrOVE-Access2Space

Author

Tilak Hewagama, Aslam, Shahid, J. Bauer, P. Clark, L. Feaga, Folta, David C., N. Gorius, T. Hurford, Livengood, Timothy A., Malphrus, Ben, Mumma, Michael J., Nixon, Conor A, M. Ravine, J. Sunshine, and Villanueva, Geronimo

Published
2020
Full Text
View/download PDF

9. Titan Surface Temperatures during the Cassini Mission

Author

Virgil G. Kunde, V. Cottini, Tetsuya Tokano, R. K. Achterberg, M. S. Kaelberer, Athena Coustenis, M. E. Segura, Conor A. Nixon, E. Guandique, N. Gorius, D. E. Jennings, F. M. Flasar, Robert E. Samuelson, Paul N. Romani, NASA Goddard Space Flight Center (GSFC), Institut für Geophysik und Meteorologie [Köln], Universität zu Köln, Department of Astronomy [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Science Systems and Applications, Inc. [Lanham] (SSAI), University of Florida [Gainesville] (UF), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)

Subjects
North pole, Physics, 010504 meteorology & atmospheric sciences, Subsolar point, Astronomy and Astrophysics, Atmospheric sciences, 01 natural sciences, Latitude, symbols.namesake, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], General Circulation Model, 0103 physical sciences, symbols, Solstice, Titan (rocket family), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

By the close of the Cassini mission in 2017 the Composite Infrared Spectrometer had recorded surface brightnesstemperatures on Titan for 13 yr (almost half a Titan year). We mapped temperatures in latitude from pole to pole inseven time segments from northern mid-winter to northern summer solstice. At the beginning of the mission thewarmest temperatures were centered at 13 S where they peaked at 93.9 K. Temperatures fell off by about 4 Ktoward the north pole and 2 K toward the south pole. As the seasons progressed the warmest temperatures shiftednorthward, tracking the subsolar point, and at northern summer solstice were centered at 24 N. While moving norththe peak temperature decreased by about 1 K, reaching 92.8 K at solstice. At solstice the fall-off toward the northand south poles were 1 K and 3 K, respectively. Thus the temperature range was the same 2 K at the two poles. Ourobserved surface temperatures agree with recent general circulation model results that take account of methanehydrology and imply that hemispherical differences in Titan's topography may play a role in the north?southasymmetry on Titan.

Published
2019

11. Seasonal evolution of Saturn's polar temperatures and composition

Author

R. K. Achterberg, Gordon L. Bjoraker, Rohini Giles, G. S. Orton, Brigette E. Hesman, Patrick G. J. Irwin, N. Gorius, James Sinclair, Leigh N. Fletcher, and Jane Hurley

Subjects
Earth and Planetary Astrophysics (astro-ph.EP), Polar front, FOS: Physical sciences, Subsidence (atmosphere), Astronomy and Astrophysics, Sudden stratospheric warming, Atmospheric sciences, Troposphere, Space and Planetary Science, Polar vortex, Solstice, Longitude, Stratosphere, Geology, Astrophysics - Earth and Planetary Astrophysics
Abstract

The seasonal evolution of Saturn's polar atmospheric temperatures and hydrocarbon composition is derived from a decade of Cassini Composite Infrared Spectrometer (CIRS) 7-16 $\mu$m thermal infrared spectroscopy. We construct a near-continuous record of atmospheric variability poleward of 60$^\circ$ from northern winter/southern summer (2004, $L_s=293^\circ$) through the equinox (2009, $L_s=0^\circ$) to northern spring/southern autumn (2014, $L_s=56^\circ$). The hot tropospheric polar cyclones and the hexagonal shape of the north polar belt are both persistent features throughout the decade of observations. The hexagon vertices rotated westward by $\approx30^\circ$ longitude between March 2007 and April 2013, confirming that they are not stationary in the Voyager-defined System III longitude system as previously thought. The extended region of south polar stratospheric emission has cooled dramatically poleward of the sharp temperature gradient near 75$^\circ$S, coinciding with a depletion in the abundances of acetylene and ethane, and suggestive of stratospheric upwelling with vertical wind speeds of $w\approx+0.1$ mm/s. This is mirrored by a general warming of the northern polar stratosphere and an enhancement in acetylene and ethane abundances that appears to be most intense poleward of 75$^\circ$N, suggesting subsidence at $w\approx-0.15$ mm/s. However, the sharp gradient in stratospheric emission expected to form near 75$^\circ$N by northern summer solstice (2017, $L_s=90^\circ$) has not yet been observed, so we continue to await the development of a northern summer stratospheric vortex. North polar minima in tropospheric and stratospheric temperatures were detected in 2008-2010 (lagging one season, or 6-8 years, behind winter solstice); south polar maxima appear to have occurred before the start of the Cassini observations (1-2 years after summer solstice). [Abridged], Comment: Preprint of article accepted for publication in Icarus

Published
2015

12. The distribution of methane in Titan’s stratosphere from Cassini/CIRS observations

Author

Bruno Bézard, Gordon L. Bjoraker, N. Gorius, Emmanuel Lellouch, Richard K. Achterberg, F. M. Flasar, Conor A. Nixon, S. Vinatier, Observatoire de Paris - Site de Paris (OP), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and NASA Goddard Space Flight Center (GSFC)

Subjects
[PHYS]Physics [physics], 010504 meteorology & atmospheric sciences, Astronomy and Astrophysics, Mole fraction, Atmospheric sciences, 01 natural sciences, Methane, Latitude, Atmosphere, Troposphere, symbols.namesake, chemistry.chemical_compound, chemistry, 13. Climate action, Space and Planetary Science, 0103 physical sciences, symbols, Environmental science, Atmosphere of Titan, Titan (rocket family), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], 010303 astronomy & astrophysics, Stratosphere, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences
Abstract

Cassini/CIRS spectra in the far- and mid-infrared region are used to determine the abundance of methane in Titan’s lower stratosphere and investigate its distribution with latitude. The CIRS spectra include emission from both the CH4 ν4 band at 7.7 μm and pure rotational lines longwards of 50 μm, which show differential sensitivities to thermal profile and methane mole fraction. We analyze nadir and limb data taken over the first part of the Cassini mission (August 2005 to June 2010), including a selection of 12 latitudes that provides a reasonably complete and regular sampling of both hemispheres. Unexpectedly, but in a consistent manner for limb and nadir geometries, large variations of the methane mole fraction near 15 mbar (∼85 km) are found, with values ranging from ∼1.0% (at low latitudes and near ±50–55°) to ∼1.5% (at ±30–35° and polar latitudes). Error bars on the retrieved methane mole fraction are 0.07–0.12% at low latitudes in the Southern hemisphere and 0.14–0.21% northward of 40°N. A 1.0% methane mole fraction at low latitudes permits us to reconcile the HASI-measured temperatures below 147 km altitude (2.7 mbar) with inferences from CIRS. The roughly hemispherically-symmetric distribution of methane gas is reminiscent of that observed or predicted for the tropospheric methane clouds, which on a yearly-averaged basis, show preferential occurrences at tropical and polar latitudes. We speculate that convective events at these latitudes result into local stratospheric methane enrichment, which may persist year-round due to dynamical mixing times in the lower stratosphere only moderately shorter than a Titan year.

Published
2014

13. Water vapor in Titan’s stratosphere from Cassini CIRS far-infrared spectra

Author

Nicholas A Teanby, Carrie M. Anderson, G. Bampasidis, Emmanuel Lellouch, F. M. Flasar, Valeria Cottini, Gordon L. Bjoraker, Richard Achterberg, N. Gorius, Patrick G. J. Irwin, R. de Kok, Bruno Bézard, Athena Coustenis, Donald E. Jennings, Conor A. Nixon, NASA Goddard Space Flight Center (GSFC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), School of Earth Sciences [Bristol], University of Bristol [Bristol], Science Systems and Applications, Inc. [Lanham] (SSAI), SRON Netherlands Institute for Space Research (SRON), Clarendon Laboratory [Oxford], University of Oxford [Oxford], and University of Oxford

Subjects
Atmospheres, 010504 meteorology & atmospheric sciences, Satellites, Atmospheric sciences, 01 natural sciences, symbols.namesake, Far infrared, 0103 physical sciences, Mixing ratio, Radiative transfer, Atmosphere of Titan, 010303 astronomy & astrophysics, Stratosphere, Spectroscopy, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, [PHYS]Physics [physics], Satellites, Atmospheres, Astronomy and Astrophysics, Spectral bands, 13. Climate action, Space and Planetary Science, symbols, Atmospheres, Composition, Environmental science, Titan (rocket family), Titan, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Water vapor, Composition
Abstract

Here we report the measurement of water vapor in Titan's stratosphere using the Cassini Composite Infrared Spectrometer (CIRS, Flasar, F.M. et al. [2004]. Space Sci. Rev. 115, 169-297). CIRS senses water emissions in the far infrared spectral region near 50μm, which we have modeled using two independent radiative transfer codes (NEMESIS (Irwin, P.G.J. et al. [2008]. J. Quant. Spectrosc. Radiat. Trans. 109, 1136-1150) and ART (Coustenis, A. et al. [2007]. Icarus 189, 35-62; Coustenis, A. et al. [2010]. Icarus 207, 461-476). From the analysis of nadir spectra we have derived a mixing ratio of 0.14±0.05ppb at an altitude of 97km, which corresponds to an integrated (from 0 to 600km) surface normalized column abundance of 3.7±1.3×10 14molecules/cm 2. In the latitude range 80°S to 30°N we see no evidence for latitudinal variations in these abundances within the error bars. Using limb observations, we obtained mixing ratios of 0.13±0.04ppb at an altitude of 115km and 0.45±0.15ppb at an altitude of 230km, confirming that the water abundance has a positive vertical gradient as predicted by photochemical models (e.g. Lara, L.M., Lellouch, F., Lopez-Moreno, J.J., Rodrigo, R. [1996]. J. Geophys. Res. 101(23), 261; Wilson, E.H., Atreya, S.K. [2004]. J. Geophys. Res. 109, E6; Hörst, S.M., Vuitton, V., Yelle, R.V. [2008]. J. Geophys. Res., 113, E10). We have also fitted our data using scaling factors of ~0.1-0.6 to these photochemical model profiles, indicating that the models over-predict the water abundance in Titan's lower stratosphere. © 2012 Elsevier Inc..

Published
2012

14. PEGASE: a free flying interferometer for the spectroscopy of giant exo-planets

Author

J. M. Le Duigou, L. Escarrat, D. Rouan, B. Sorrente, A. Léger, Yves Rabbia, Benoit Meyssignac, G. Rousset, Fabien Malbet, R. Cledassou, Denis Mourard, Olivier Absil, Frédéric Cassaing, Marc Ollivier, P.-Y. Guidotti, Michel Delpech, Paul Duchon, N. Gorius, Bruno Fleury, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Interferometry, 13. Climate action, Hot Jupiter, Brown dwarf, Astronomy, Darwin (spacecraft), Angular resolution, Satellite, Spectral resolution, Exoplanet, ComputingMilieux_MISCELLANEOUS, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM]
Abstract

This paper presents a summary of the phase-0 performed in 2005 for the Pegase mission. The main scientific goal is the spectroscopy of hot Jupiters (Pegasides) and brown dwarfs from 2.5 to 5 μm. The mission can extend to the exploration of the inner part of protoplanetary disks, the study of dust clouds around AGN,... The instrument is basically a two-aperture (D=40 cm) interferometer composed of two siderostats and one beam-combiner. The formation is linear and orbits around L2, pointing in the anti-solar direction within a +/-30° cone. The baseline is adjustable from 50 to 500 m in both nulling and visibility measurement modes. The angular resolution ranges from 1 to 20 mas and the spectral resolution is 60. in the nulling mode, a 2.5 nm rms stability of the optical path difference (OPD) and a pointing stability of 30 mas rms impose a two level control architecture. It combines control loops implemented at satellite level and control loops operating inside the payload using fine mechanisms. According to our preliminary study, this mission is feasible within an 8 to 9 years development plan using existing or slightly improved space components, but its cost requires international cooperation. Pegase could be a valuable Darwin/TPF-I pathfinder, with a less demanding, but still ambitious, technological challenge and a highly associated scientific return.

Published
2006

15. Towards a laboratory breadboard for PEGASE, the DARWIN pathfinder

Author

Michel Delpech, Frédéric Cassaing, F. Brachet, Denis Mourard, A. Léger, Marc Ollivier, Marc Barillot, Christophe Buisset, François Hénault, P.-Y. Guidotti, G. Rousset, D. Rouan, J. M. Le Duigou, B. Sorrente, N. Gorius, Bruno Fleury, Yves Rabbia, Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, and COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Physics, Payload, 02 engineering and technology, Breadboard, 021001 nanoscience & nanotechnology, 7. Clean energy, 01 natural sciences, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], 010309 optics, Interferometry, Cophasing, Pathfinder, 0103 physical sciences, Astronomical interferometer, Darwin (spacecraft), 0210 nano-technology, Nuller, ComputingMilieux_MISCELLANEOUS, Remote sensing
Abstract

PEGASE, a spaceborne mission proposed to the CNES, is a 2-aperture interferometer for nulling and interferometric imaging. PEGASE is composed of 3 free-flying satellites (2 siderostats and 1 beam combiner) with baselines from 50 to 500 m. The goals of PEGASE are the spectroscopy of hot Jupiter (Pegasides) and brown dwarves, the exploration of the inner part of protoplanetary disks and the validation in real space conditions of nulling and visibility interferometry with formation flying. During a phase-0 study performed in 2005 at CNES, ONERA and in the laboratories, the critical subsystems of the optical payload have been investigated and a preliminary system integration has been performed. These subsystems are mostly the broadband (2.5-5 μm) nuller and the cophasing system (visible) dedicated to the real-time control of the OPD/tip/tilt inside the payload. A laboratory breadboard of the payload is under definition and should be built in 2007.

Published
2006

17. A hexagon in Saturn's northern stratosphere surrounding the emerging summertime polar vortex.

Author

Fletcher LN, Orton GS, Sinclair JA, Guerlet S, Read PL, Antuñano A, Achterberg RK, Flasar FM, Irwin PGJ, Bjoraker GL, Hurley J, Hesman BE, Segura M, Gorius N, Mamoutkine A, and Calcutt SB

Abstract

Saturn's polar stratosphere exhibits the seasonal growth and dissipation of broad, warm vortices poleward of ~75° latitude, which are strongest in the summer and absent in winter. The longevity of the exploration of the Saturn system by Cassini allows the use of infrared spectroscopy to trace the formation of the North Polar Stratospheric Vortex (NPSV), a region of enhanced temperatures and elevated hydrocarbon abundances at millibar pressures. We constrain the timescales of stratospheric vortex formation and dissipation in both hemispheres. Although the NPSV formed during late northern spring, by the end of Cassini's reconnaissance (shortly after northern summer solstice), it still did not display the contrasts in temperature and composition that were evident at the south pole during southern summer. The newly formed NPSV was bounded by a strengthening stratospheric thermal gradient near 78°N. The emergent boundary was hexagonal, suggesting that the Rossby wave responsible for Saturn's long-lived polar hexagon-which was previously expected to be trapped in the troposphere-can influence the stratospheric temperatures some 300 km above Saturn's clouds.

Published
2018
Full Text
View/download PDF

18. Composite infrared spectrometer (CIRS) on Cassini: publisher's note.

Author

Jennings DE, Flasar FM, Kunde VG, Nixon CA, Segura ME, Romani PN, Gorius N, Albright S, Brasunas JC, Carlson RC, Mamoutkine AA, Guandique E, Kaelberer MS, Aslam S, Achterberg RK, Bjoraker GL, Anderson CM, Cottini V, Pearl JC, Smith MD, Hesman BE, Barney RD, Calcutt S, Vellacott TJ, Spilker LJ, Edgington SG, Brooks SM, Ade P, Schinder PJ, Coustenis A, Courtin R, Michel G, Fettig R, Pilorz S, and Ferrari C

Abstract

This publisher's note renumbers the reference list in Appl. Opt.56, 5274 (2017)APOPAI0003-693510.1364/AO.56.005274.

Published
2017
Full Text
View/download PDF

19. Simple parametric model for intensity calibration of Cassini composite infrared spectrometer data.

Author

Brasunas J, Mamoutkine A, and Gorius N

Abstract

Accurate intensity calibration of a linear Fourier-transform spectrometer typically requires the unknown science target and the two calibration targets to be acquired under identical conditions. We present a simple model suitable for vector calibration that enables accurate calibration via adjustments of measured spectral amplitudes and phases when these three targets are recorded at different detector or optics temperatures. Our model makes calibration more accurate both by minimizing biases due to changing instrument temperatures that are always present at some level and by decreasing estimate variance through incorporating larger averages of science and calibration interferogram scans.

Published
2016
Full Text
View/download PDF

20. Identifying sampling comb changes in Fourier transform spectrometers with significant self-emission and beam splitter absorption.

Author

Brasunas J, Mamoutkine A, and Gorius N

Abstract

For accurate calibration of Fourier transform spectrometers we must constrain or resample the interferogram data to an invariant sampling comb. This can become challenging when instrument self-emission is significant and beam splitter absorption is present. The originally-sampled interferogram center-burst position can move due not only to sampling comb changes, but also to an interaction between the strength of an external target and the so-called anomalous phase (the two ports of the interferometer contribute center-bursts at different locations, and the relative weighting of the two ports varies with the strength of the external target). We present a model of the anomalous phase to enable partitioning of changes in observed center-burst location between sampling comb changes and anomalous phase effects.

Published
2015
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results