Error analysis for retrieval of Venus׳ IR surface emissivity from VIRTIS/VEX measurements

Kappel, David; Haus, Rainer; Arnold, Gabriele

doi:10.1016/j.pss.2015.01.014

Cited by 14 publications

(59 citation statements)

References 47 publications

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“…Disentangling these contributions is a difficult and not well‐constrained problem [e.g., Kappel et al , ]; however, here we only need to look for transient variations. The median over time of VIRTIS measurements

(〈〉, I_{normalsurf})

is an estimate of the local background.…”

Section: Data Processingmentioning

confidence: 99%

“…There are several sources for such errors: shifts in the wavelength registration and bandwidth between images and steadily varying with pixel position on the detector [Bézard et al, 2009], insufficient stray light correction [cf. Mueller et al, 2008;Kappel et al, 2012], residual cloud error [Kappel et al, 2015], and incorrect flat field calibration [Kappel et al, 2012]. In addition to these systematic error sources, there is instrumental noise, which varies with internal temperature of the instrument, image exposure time, and radiation exposure.…”

Section: Filtering and Noise Estimatementioning

confidence: 99%

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Search for active lava flows with VIRTIS on Venus Express

et al. 2017

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The Visible Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on Venus Express observed thermal emission from the surface of Venus at 1 μm wavelength and thus would have detected sufficiently bright incandescent lava flows. No eruptions were detected in the observations between April 2006 and October 2008, covering an area equivalent to 7 times the planets surface on separate days. Models of the cooling of lava flows on Earth are adapted to Venus ambient conditions to predict thermal emission based on effusion rate. Taking into account the blurring of surface thermal emission by the atmosphere, the VIRTIS images would detect eruptions with effusion rates above 500 to 1000 m3/s. On Earth such eruptions occur but are rare. Based on an eruption rate and duration distribution fitted to historical data of three terrestrial volcanos, we estimate that only a few percent of all eruptions are detectable. With these assumptions the VIRTIS data can constrain the rate of effusive volcanism on Venus to be less than about 300 km3/yr, at least an order of magnitude higher than existing constraints. There remains a large uncertainty because of unknown properties of lava flows on Venus. Resolving flows in radar imaging and their thickness in altimetry might help to better constrain these properties. While VIRTIS data do not represent a significant constraint on volcanism, an optimized instrument with a 20 times better signal‐to‐noise ratio would likely be able to detect effusion rates on the order of 50 m3/s.

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(〈〉, I_{normalsurf})

is an estimate of the local background.…”

Section: Data Processingmentioning

confidence: 99%

Section: Filtering and Noise Estimatementioning

confidence: 99%

Search for active lava flows with VIRTIS on Venus Express

et al. 2017

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“…Venus surface emissivity retrieval bases on a detailed radiative transfer simulation model ("forward model") 12,17,18,19 , a multi-spectrum retrieval technique (MSR) 18,19,20 , and a detailed error analysis 19,20 . The radiative transfer model simulates the radiance spectra.…”

Section: Retrieval Methodsmentioning

confidence: 99%

VIRTIS on Venus Express: retrieval of real surface emissivity on global scales

et al. 2015

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The extraction of surface emissivity data provides the data base for surface composition analyses and enables to evaluate Venus' geology. The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA's Venus Express mission measured, inter alia, the nightside thermal emission of Venus in the near infrared atmospheric windows between 1.0 and 1.2 µm. These data can be used to determine information about surface properties on global scales. This requires a sophisticated approach to understand and consider the effects and interferences of different atmospheric and surface parameters influencing the retrieved values. In the present work, results of a new technique for retrieval of the 1.0 -1.2 µm -surface emissivity are summarized. It includes a Multi-Window Retrieval Technique, a Multi-Spectrum Retrieval technique (MSR), and a detailed reliability analysis. The MWT bases on a detailed radiative transfer model making simultaneous use of information from different atmospheric windows of an individual spectrum. MSR regularizes the retrieval by incorporating available a priori mean values, standard deviations as well as spatial-temporal correlations of parameters to be retrieved. The capability of this method is shown for a selected surface target area. Implications for geologic investigations are discussed. Based on these results, the work draws conclusions for future Venus surface composition analyses on global scales using spectral remote sensing techniques. In that context, requirements for observational scenarios and instrumental performances are investigated, and recommendations are derived to optimize spectral measurements for Venus' surface studies.

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“…The VIRTIS-M experiment on VenusExpress regularly mapped the Venus' surface from 2006 to 2009. There are, nevertheless, large uncertainties in the absolute value of the emissivity, as discussed in Haus and Arnold (2010) and Kappel et al (2015). In their analysis of 47 orbits, Haus and Arnold (2010) find surface emissivities at 1.02 mm ranging from typically 0.5 to 0.9, with lower emissivities found at higher elevations (0.6-0.8 in average).…”

Section: Uncertaintiesmentioning

confidence: 98%