Publications by Fred Taylor

Exploring the Saturn system in the thermal infrared: The composite infrared spectrometer

Space Science Reviews 115 (2005) 169-297

FM Flasar, VG Kunde, MM Abbas, RK Achterberg, P Ade, A Barucci, B Bézard, GL Bjoraker, JC Brasunas, S Calcutt, R Carlson, CJ Césarsky, BJ Conrath, A Coradini, R Courtin, A Coustenis, S Edberg, S Edgington, C Ferrari, T Fouchet, D Gautier, PJ Gierasch, K Grossman, P Irwin, DE Jennings, E Lellouch, AA Mamoutkine, A Marten, JP Meyer, CA Nixon, GS Orton, TC Owen, JC Pearl, R Prangé, F Raulin, PL Read, PN Romani, RE Samuelson, ME Segura, MR Showalter, AA Simon-Miller, MD Smith, JR Spencer, LJ Spilker, FW Taylor

The Composite Infrared Spectrometer (CIRS) is a remote-sensing Fourier Transform Spectrometer (FTS) on the Cassini orbiter that measures thermal radiation over two decades in wavenumber, from 10 to 1400 cm - 1 (1 mm to 7μ m), with a spectral resolution that can be set from 0.5 to 15.5 cm - 1 . The far infrared portion of the spectrum (10-600 cm - 1 ) is measured with a polarizing interferometer having thermopile detectors with a common 4-mrad field of view (FOV). The middle infrared portion is measured with a traditional Michelson interferometer having two focal planes (600-1100 cm - 1 , 1100-1400 cm - 1 ). Each focal plane is composed of a 1× 10 array of HgCdTe detectors, each detector having a 0.3-mrad FOV. CIRS observations will provide three-dimensional maps of temperature, gas composition, and aerosols/condensates of the atmospheres of Titan and Saturn with good vertical and horizontal resolution, from deep in their tropospheres to high in their mesospheres. CIRS's ability to observe atmospheres in the limb-viewing mode (in addition to nadir) offers the opportunity to provide accurate and highly resolved vertical profiles of these atmospheric variables. The ability to observe with high-spectral resolution should facilitate the identification of new constituents. CIRS will also map the thermal and compositional properties of the surfaces of Saturn's icy satellites. It will similarly map Saturn's rings, characterizing their dynamical and spatial structure and constraining theories of their formation and evolution. The combination of broad spectral range, programmable spectral resolution, the small detector fields of view, and an orbiting spacecraft platform will allow CIRS to observe the Saturnian system in the thermal infrared at a level of detail not previously achieved. © 2004 Kluwer Academic Publishers.

Water vapor abundance in Venus' middle atmosphere from Pioneer Venus OIR and Venera 15 FTS measurements

ICARUS 173 (2005) 84-99

ME Koukouli, PGJ Irwin, FW Taylor

The Pioneer Venus Orbiter Infrared Radiometer and Venera 15 Fourier Transform Spectrometer observations of thermal emission from Venus' middle atmosphere between 10degreesS and 50degreesN have been independently re-analyzed using a common method to determine global maps of temperature, cloud optical depth, and water vapor abundance. The spectral regions observed include the strong 15 mum carbon dioxide band and the 45 mum fundamental rotational water band. The different spatial and spectral resolutions of the two instruments have necessitated the development of flexible analysis tools. New radiative transfer and retrieval models have been developed for this purpose based on correlated-k absorption tables calculated with up-to-date spectral line data. The common analysis of these two sets of observations has hence been possible for the first time. From the PV OIR observations, the cloud-top unit optical depth pressure showed a minimum of similar to 110 +/- 10 mbars in the evening equatorial region and a maximum of similar to 160 +/- 12 mbars in the morning mid-latitude regions. From the Venera 15 FTS spectra, the cloud-top pressure was found to increase from morning values of similar to 120 +/- 10 to 200 +/- 30 mbars in the late afternoon/early evening region. The cloud-top water vapor abundances observed by the PV OIR instrument were found to fluctuate from 10 +/- 5 ppm at night up to 90 +/- 15 ppm in the equatorial cloud-top region shortly after the sub-solar point. The mean Venera 15 FTS water vapor abundances were found to be 12 +/- 5 ppm with only a slight enhancement over the equatorial latitude bands and no clear day-night distinction. The common analysis of these two sets of observations broadly validates previously published individual findings. The differences in the retrieved atmospheric state can no longer be attributed to radiative transfer modeling bias and suggest significant temporal variability in the middle atmosphere of Venus. (C) 2004 Published by Elsevier Inc.

Methane absorption in the atmosphere of Jupiter from 1800 to 9500 cm-1 and implications for vertical cloud structure

Icarus 176 (2005) 255-271

PGJ Irwin, K Sihra, NE Bowles, FW Taylor, SB Calcutt

Temperatures, Winds, and Composition in the Saturnian System

Science 307 (2005) 1247-1251

FM Flasar, PGJ Irwin, SB Calcutt, R Achterberg, FW Taylor

On the distribution and variability of water vapour in the middle atmosphere of Venus

ADV SPACE RES 36 (2005) 2138-2141

FW Taylor

Water is a key constituent of every planetary environment, and on Venus its abundance, distribution and temporal behaviour are crucial for understanding greenhouse warming, cloud formation and dissipation, volcanism, and atmospheric evolution. Many telescopic and spacecraft-based observations of atmospheric water vapour on Venus have been made, but are inconclusive about its role as a component of the current climate system on the planet. The data suggest that H2O may be well mixed in the lower atmosphere, but highly variable in and near the cloud layers, and probably also at the thermospheric levels where dissociation and loss occur. The details of the middle atmosphere variability, how significant it is, and the processes responsible, remain controversial. In particular, the Pioneer Venus Infrared Radiometer found a large 'wet patch', a localized region where the water vapour mixing ratio is generally enhanced by one to two orders of magnitude over the global mean, occurring at low latitudes in the mid-afternoon, that has not been confirmed by other observations. If it is real, the presently unknown mechanism that produces it may be an important part of the water cycle in the Venusian atmosphere. Here we reconsider this problem, and some of the possible processes that may be involved, prior to the expected acquisition of relevant new data by Venus Express and the Venus Climate Orbiter. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

Elementary climate physics

Oxford University Press, 2005

FW Taylor

Climate Physics is a modern subject based on a space-era understanding of the physical properties of the atmosphere and ocean, their planetary-scale history and ...

Elementary climate physics

Oxford University Press, 2005

FW Taylor

Climate Physics is a modern subject based on a space-era understanding of the physical properties of the atmosphere and ocean, their planetary-scale history and ...

Titan's Atmospheric Temperatures, Winds, and Composition.

Science 308 (2005) 975-978

FW Taylor, Flasar F.M., Achterberg, R.K., Conrath, B.J.

Search for spatial variation in the jovian 15N/14N ratio from Cassini/CIRS observations

Icarus 172 (2004) 50-58

SB Calcutt, Fouchet, Irwin, Parrish

Retrievals of jovian tropospheric phosphine from Cassini/CIRS

ICARUS 172 (2004) 37-49

PGJ Irwin, P Parrish, T Fouchet, SB Calcutt, FW Taylor, AA Simon-Miller, CA Nixon

Jupiter's atmospheric composition from the Cassini thermal infrared spectroscopy experiment.

Science 305 (2004) 1582-1586

VG Kunde, FM Flasar, DE Jennings, B Bézard, DF Strobel, BJ Conrath, CA Nixon, GL Bjoraker, PN Romani, RK Achterberg, AA Simon-Miller, P Irwin, JC Brasunas, JC Pearl, MD Smith, GS Orton, PJ Gierasch, LJ Spilker, RC Carlson, AA Mamoutkine, SB Calcutt, PL Read, FW Taylor, T Fouchet, P Parrish, A Barucci, R Courtin, A Coustenis, D Gautier, E Lellouch, A Marten, R Prangé, Y Biraud, C Ferrari, TC Owen, MM Abbas, RE Samuelson, F Raulin, P Ade, CJ Césarsky, KU Grossman, A Coradini

The Composite Infrared Spectrometer observed Jupiter in the thermal infrared during the swing-by of the Cassini spacecraft. Results include the detection of two new stratospheric species, the methyl radical and diacetylene, gaseous species present in the north and south auroral infrared hot spots; determination of the variations with latitude of acetylene and ethane, the latter a tracer of atmospheric motion; observations of unexpected spatial distributions of carbon dioxide and hydrogen cyanide, both considered to be products of comet Shoemaker-Levy 9 impacts; characterization of the morphology of the auroral infrared hot spot acetylene emission; and a new evaluation of the energetics of the northern auroral infrared hot spot.

An intense stratospheric jet on Jupiter

Nature 427 (2004) 132-135

SB Calcutt, Achtergerg, Flasar, Kunde

The stratosphere

PHILOS T ROY SOC A 361 (2003) 11-22

FW Taylor

The stratosphere is that part of the atmosphere which lies between ca. 10 and 50 km above the surface of the Earth and which contains the ozone layer. It is the seat of much interesting behaviour in terms of dynamics, radiation and chemistry, now revealed in detail by observations from modern space instruments, but still not completely understood. Other planetary atmospheres exhibit stratospheric behaviour which in some ways resembles, and in others contrasts sharply with, that of the Earth. In reviewing these topics, this paper describes some key problems that will be addressed by new measurements from space in the near future.

The greenhouse effect and climate change revisited


FW Taylor

Some fundamental questions concerning the circulation of the atmosphere of Venus

ADV SPACE RES 29 (2002) 227-231

FW Taylor

There has been very little new data on the atmosphere of Venus in recent years, but ongoing studies of data from space missions such as Pioneer Venus, Venera and Galileo, plus ground-based observations, have uncovered, but not yet resolved, a number of fundamental questions relating to the atmospheric global circulation. In addition to the perennial problem of trying to understand the forces driving the equatorial super-rotation, there is still no reliable model, even in the qualitative sense, of the mean meridional (equator-to-pole) circulation, nor of the peculiar giant polar vortices which are a major feature of it. There is pronounced meteorological activity in the upper troposphere, the general character of which, let alone the processes responsible, remains unknown. The very limited observations of temperature and compositional trends, wave motions and cloud features which exist at present provide some clues as to what may be happening on the Earth's twin planet and suggest the next steps towards a more detailed, quantitative understanding. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Correlation of near-infrared albedo and 5-micron brightness variations in Jupiter's atmosphere

ADV SPACE RES 29 (2002) 285-290

PGJ Irwin, SB Calcutt, AL Weir, FW Taylor, RW Carlson

The Galileo Near Infrared Mapping Spectrometer (NIMS) has returned many spectra of the Jovian atmosphere in the range 0.7-5.2 mum. Although communications restrictions have limited the data return, several wide-area maps have been recorded at near full NIMS resolution. Using these data it is possible to determine both the average shape of the near-infrared (NIR) spectra with very thick clouds (and zero 5-mum brightness) and how these spectra vary as the 5-mum brightness increases.In most of the cases studied, we find that the variable part of the reflectivity has a very different shape to the mean part and may best be explained by variable reflectivity in the cloud layers at pressures greater than 1 bar. In these cases it would thus appear that a variable opacity in a cloud deck based between 1 and 2 bars is mainly responsible for the NIR albedo variations, and not a higher ammonia cloud based above 1 bar as has often been previously suggested. While the composition of this main variable cloud deck could well be ammonium hydrosulphide, other candidates include ammonia (should the much higher estimate of its deep gaseous fractional abundance resulting from the Galileo probe mission be correct), and perhaps even the upper reaches of a deeper water cloud. (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

The Lavoisier mission: A system of descent probe and balloon flotilla for geochemical investigation of the deep atmosphere and surface of Venus

ADV SPACE RES 29 (2002) 255-264

E Chassefiere, JJ Berthelier, JL Bertaux, E Quemerais, JP Pommereau, P Rannou, F Raulin, P Coll, D Coscia, A Jambon, P Sarda, JC Sabroux, G Vitter, A Le Pichon, B Landeau, P Lognonne, Y Cohen, S Vergniole, G Hulot, M Mandea, JF Pineau, B Bezard, HU Keller, D Titov, D Breuer, K Szego, C Ferencz, M Roos-Serote, O Korablev, V Linkin, R Rodrigo, FW Taylor, AM Harri

Lavoisier mission is a joint effort of eight European countries and a technological challenge aimed at investigating the lower atmosphere and the surface of Venus. The mission consists of a descent probe and three balloons to be deployed below the cloud deck. Its main scientific objectives may be summarized as following : (i) composition of the deep atmosphere : noble gas (elemental/isotopic), molecular species (elemental/isotopic), oxygen fugacity; vertical/horizontal/temporal variability; (ii) infrared spectroscopy and radiometry (molecular composition, radiative transfer); (iii) dynamics of the atmosphere : p, T, acceleration measurements, balloon localization through VLBI, meteorological events signed by acoustic waves, atmospheric mixing as imprinted on radioactive tracers; (iv) surface morphology and mineralogy through near infrared imaging on dayside, surface temperature through NIR imaging on nightside. Additional tentative objectives are search for (a) atmospheric electrical activity (optically, radioelectrically, acoustically), (b) crustal outgassing and/or volcanic activity : acoustic activity, horizontal/vertical distribution of radioactive tracers, (c) seismic activity : acoustic waves transmitted from crust to atmosphere, and (d) remanent and/or intrinsic magnetic field. Lavoisier was proposed to ESA in response to the F2/F3 mission Announcement of Opportunity at the beginning of 2000, but it was not selected for the assessment study, A wide international partnership was created for this occasion, including Finland (FMI), France (IPSL, MAGIE, Universite Orsay, IPSN, INPG, CEA, IPGP, Obs. Paris-Meudon), Germany (MPAe, Univ. Muenster), Hungary (KFKI, Univ. Eotvos), Portugal (OAL), Russia (IKI), Spain (IAA), United Kingdom (Univ. Oxford). (C) 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.

Atmospheric composition and cloud structure in jovian 5-μm hotspots from analysis of Galileo NIMS measurements

Icarus 150 (2001) 48-68

CA Nixon, PGJ Irwin, SB Calcutt, FW Taylor, RW Carlson

NIMS is the Near-Infrared Mapping Spectrometer on board the Galileo spacecraft in jovian orbit. We have selected four maps of warm-to-hot regions of the North Equatorial Belt (NEB) for study, analyzing the spectra emerging in the low-opacity 5-μm window. Two methods for calculating the spectrum have been used. The first is a full-scattering radiative transfer forward model that is slow but accurate. The second method calculates spectra by interpolating on a grid of spectra precalculated using the first method for a range of model atmospheres. This method of forward calculation is more suited to analysis of large data sets where application of the full radiative transfer in every instance would be computationally prohibitive. The faster method is verified against the first before being used alone. A retrieval (inversion) algorithm is then used to match model spectra to data and obtain values for cloud opacities and gas mixing ratios. We first sum spectra with similar peak radiances to produce mean spectra representative of brighter and darker (at 5 μm) regions of the maps. These coadded spectra are then analyzed with the fast retrieval code to obtain the average variations in atmospheric parameters from the center to the edges of the hotspots. These analyses confirm that 5-μm hotspots are relatively cloud free, and that a medium level (1.5-bar) cloud layer of large NH 4 SH particles is the main absorber at these wavelengths. Variations in water vapor relative humidity and high (0.5-bar) ammonia cloud opacity are also derived. We then analyze single spectra over wide areas to produce spatial maps of parameter variations. We find that models that do not include a deep water cloud (~4 bar) do not match all the spectra to within the noise level. A deep water cloud therefore seems to be present in localized areas, toward the edges of the hotspot regions. We examine these findings in the light of results from other Galileo instruments, concluding that the deep cloud observed by the SSI instrument at several locations is likely to be the deep water cloud required by the NIMS data. © 2001 Academic Press.

Latitudinal and longitudinal behavior of the mesospheric OH nightglow layer as observed by the Improved Stratospheric and Mesospheric Sounder on UARS


G Zaragoza, FW Taylor, M Lopez-Puertas

The origin of belt/zone contrasts in the atmosphere of Jupiter and their correlation with 5-mu m opacity

ICARUS 149 (2001) 397-415

PGJ Irwin, AL Weir, FW Taylor, SB Calcutt, RW Carlson