Band parameters for self-broadened ammonia gas in the range 0.74 to 5.24 mum to support measurements of the atmosphere of the planet Jupiter
Icarus, 2008
We present new measurements and modelling of low-resolution transmission spectra of self-broadene... more We present new measurements and modelling of low-resolution transmission spectra of self-broadened ammonia gas, one of the most important absorbers found in the near-infrared spectrum of the planet Jupiter. These new spectral measurements were specifically designed to support measurements of Jupiter's atmosphere made by the Near-Infrared Mapping Spectrometer (NIMS) which was part of the Galileo mission that orbited Jupiter from 1995 to September 2003. To reach approximate jovian conditions in the lab, a new gas spectroscopy facility was developed and used to measure self-broadened ammonia spectra from 0.74 to 5.2 μm, virtually the complete range of the NIMS instrument, for the first time. Spectra were recorded at temperatures varying from 300 to 215 K, pressures from 1000 to 33 mb and using three different path lengths (10.164, 6.164 and 2.164 m). The spectra were then modelled using a series of increasingly complex physically based transmittance functions.
Probing Mars’ atmosphere with ExoMars Mars Climate Sounder
... Probing Mars' atmosphere with ExoMars Mars Climate Sounder. Irwin, Patrick GJ; Calcu... more ... Probing Mars' atmosphere with ExoMars Mars Climate Sounder. Irwin, Patrick GJ; Calcutt, SB; Read, PL; Bowles, NE and Lewis, S. (2011). Probing Mars' atmosphere with ExoMars Mars Climate Sounder. ... Item ID: 27972. Depositing User: Stephen Lewis. ...
A Look at Dust Storms on Mars (2007 To 2009) Using MCS and THEMIS Observations
Martian dust storms may be small, localised and short lived or can be large and intense and expan... more Martian dust storms may be small, localised and short lived or can be large and intense and expand to enshroud most, if not all, of the planet within a few days. The martian dusty season occurs near the time of perihelion (closest approach to the sun) during Mars' southern hemisphere spring and summer. During this period (+/- 90 degrees Ls
Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its... more Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its north polar region has been in prolonged darkness since the solstice in October 2002. As a result, the north polar region is currently characterised by cold stratospheric temperatures and there is enrichment of trace gases due to downward atmospheric motion (e.g. Teanby et al., Icarus
Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its... more Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its north polar region has been in prolonged darkness since the solstice in October 2002. As a result, the north polar region is currently characterised by cold stratospheric temperatures and there is enrichment of trace gases due to downward atmospheric motion (e.g. Teanby et al., Icarus
Latitudinal variations in the temperature and composition of Saturn's upper troposphere from Cassini/CIRS
The Cassini Composite Infrared Spectrometer CIRS Flasar et al 2004 has been used to derive the me... more The Cassini Composite Infrared Spectrometer CIRS Flasar et al 2004 has been used to derive the meridional variation of temperature phosphine PH 3 and ammonia NH 3 abundance in Saturn s upper troposphere 0 8 to 0 1 atm Since orbital insertion in July 2004 CIRS has recorded thousands of spectra in both the far 10 - 600 cm -1
Latitudinal variations in the temperature and composition of Saturn's upper troposphere from Cassini/CIRS
The Cassini Composite Infrared Spectrometer CIRS Flasar et al 2004 has been used to derive the me... more The Cassini Composite Infrared Spectrometer CIRS Flasar et al 2004 has been used to derive the meridional variation of temperature phosphine PH 3 and ammonia NH 3 abundance in Saturn s upper troposphere 0 8 to 0 1 atm Since orbital insertion in July 2004 CIRS has recorded thousands of spectra in both the far 10 - 600 cm -1
Phosphine, Aerosols and Temperature Variations in Saturn's Upper Troposphere from Cassini/CIRS Observations
Thermal infrared data from the Cassini Composite Infrared Spectrometer (CIRS, Flasar et al., 2004... more Thermal infrared data from the Cassini Composite Infrared Spectrometer (CIRS, Flasar et al., 2004) has been used to produce global maps of temperature, para-hydrogen fraction, phosphine and ammonia distribution in the 60-800 mbar region with a high spatial resolution that can only be achieved by the Cassini orbiter. Since orbital insertion in July 2004, CIRS has recorded thousands of spectra
Space telescopes such as EChO (Exoplanet Characterisation Observatory) and JWST (James Webb Space... more Space telescopes such as EChO (Exoplanet Characterisation Observatory) and JWST (James Webb Space Telescope) will be important for the future study of extrasolar planet atmospheres. Both of these missions are capable of performing high sensitivity spectroscopic measurements at moderate resolutions in the visible and infrared, which will allow the characterisation of atmospheric properties using primary and secondary transit spectroscopy. We use the NEMESIS radiative transfer and retrieval tool (Irwin et al. 2008, Lee et al. 2012) to explore the potential of the proposed EChO mission to solve the retrieval problem for a range of H2-He planets orbiting different stars. We find that EChO should be capable of retrieving temperature structure to ~200 K precision and detecting H2O, CO2 and CH4 from a single eclipse measurement for a hot Jupiter orbiting a Sun-like star and a hot Neptune orbiting an M star, also providing upper limits on CO and NH3. We provide a table of retrieval precisio...
Quantifying The Effect Of Scattering Upon The Retrieved Dust Opacity In The Martian Atmosphere, As Deduced From Mro/mcs Measurements
Mars Climate Sounder data from September to November 2006 is analysed to determine the effect of ... more Mars Climate Sounder data from September to November 2006 is analysed to determine the effect of scattering upon the retrieved dust opacity in the atmosphere of Mars. The inclusion of scattering in dust retrievals makes them significantly more computationally expensive. Thus, understanding the regimes in which scattering plays a less significant role could considerably decrease the computational time of analysing the extensive MCS dataset. Temperature profiles were initially retrieved using Nemesis, Oxford University's multivariate retrieval algorithm, at each location using MCS' A1, A2 and A3 channels (595 to 665 cm-1 ).Using these temperature profiles, and by assuming the characteristics of the dust particles to be comparable to those of Wolff and Clancy (2003), the dust opacity was retrieved using the B1 channel of MCS (290 to 340 cm-1 ) with and without scattering. The effect of scattering on the fit to the MCS data and on the derived vertical dust profile at various locations across the planet are presented. Particular emphasis is placed upon understanding the spatial and temporal variations of atmospheric regimes in which scattering plays a significant role.
We demonstrate the effectiveness of the Exoplanet Characterisation Observatory mission concept fo... more We demonstrate the effectiveness of the Exoplanet Characterisation Observatory mission concept for constraining the atmospheric properties of hot and warm gas giants and super Earths. Synthetic primary and secondary transit spectra for a range of planets are passed through EChOSim (Waldmann & Pascale 2014) to obtain the expected level of noise for different observational scenarios; these are then used as inputs for the NEMESIS atmospheric retrieval code and the retrieved atmospheric properties (temperature structure, composition and cloud properties) compared with the known input values, following the method of Barstow et al. (2013a). To correctly retrieve the temperature structure and composition of the atmosphere to within 2 {\sigma}, we find that we require: a single transit or eclipse of a hot Jupiter orbiting a sun-like (G2) star at 35 pc to constrain the terminator and dayside atmospheres; 20 transits or eclipses of a warm Jupiter orbiting a similar star; 10 transits/eclipses ...
In recent years, an increasing number of observations have been made of the transits of 'Hot Jupi... more In recent years, an increasing number of observations have been made of the transits of 'Hot Jupiters', such as HD 189733b, about their parent stars from the visible through to mid-infrared wavelengths, which have been modelled to derive the likely atmospheric structure and composition of these planets. As measurement techniques improve, the measured transit spectra of 'Super-Earths' such as GJ 1214b are becoming better constrained, allowing model atmospheric states to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets such as the Earth or cold planets like Jupiter, it is hoped that this might become practical in the coming decades and if so, it is of interest to determine what we might infer from such measurements. In this work we have constructed atmospheric models of the Solar System planets from 0.4 -15.5 µm that are consistent with ground-based and satellite observations and from these calculate the primary transit and secondary eclipse spectra (with respect to the Sun and typical Mdwarfs) that would be observed by a 'remote observer', many light years away. From these spectra we test what current retrieval models might infer about their atmospheric states and compare these with the 'ground truths' in order to assess: a) the inherent uncertainties in transit spectra observations; b) the relative merits of primary transit and secondary eclipse spectra; and c) the advantages of acquiring directly imaged spectra of these planets. We find that observing secondary eclipses of the Solar System would not give sufficient information for determining atmospheric properties with 10m-diameter telescopes from a distance of 10 light years, but that primary transits give much better information. We find that a single transit of Jupiter in front of the Sun could potentially be used to determine temperature and stratospheric composition, but for the Earth the mean atmospheric composition could ! ! ! 4! only be determined if it were orbiting a much smaller M-dwarf. For both Jupiter and Earth we note that direct imaging with sufficient nulling of the light from the parent star theoretically provides the best method of determining the atmospheric properties of such planets.
Preliminary Martian Atmospheric Water Vapour Column Abundances with Mars Climate Sounder
Mars Climate Sounder (MCS) is an infra-red radiometer on board NASA's Mars Reconnaissance Orb... more Mars Climate Sounder (MCS) is an infra-red radiometer on board NASA's Mars Reconnaissance Orbiter (MRO) launched in August 2005 and now orbiting Mars in a near circular polar orbit. MCS has nine spectral channels in the range 0.3-50 µm. Goals of MCS include global characterization of atmospheric temperature, dust and water profiles observing temporal and spatial variation. Using Oxford University's
Mars Climate Sounder (MCS) on Mars Reconnaisance Orbiter (MRO) collected limb observations for mo... more Mars Climate Sounder (MCS) on Mars Reconnaisance Orbiter (MRO) collected limb observations for most of the 2007 global dust storm event. MCS is a nine channel infrared radiometer with limb staring arrays optimized of atmospheric sounding. In the 15 micron channel (nominally designed for pressure and high altitude temperature retrievals), the lowest detector (pointed 5 km below the surface) has
Uploads
Papers by Neil E Bowles