The ground segment for the ESA M4 Ariel exoplanet space mission is introduced. The ground segment encompasses the framework necessary to support the development of the Ariel mission to launch, ...in-flight operations and calibration, data processing pipeline and data handling, including user support. The structure of the ground segment and assumed responsibilities between ESA and the Ariel mission consortium is explained, along with their interfaces. The operational phases for the mission are introduced, including the early commissioning/verification phases, the science operations and the calibration strategy. The smooth transition of the ground segment through the various pre/post launch mission phases to nominal operations will be paramount in guaranteeing the success, scientific return and impact of the Ariel mission. The expected science data products are defined and a representative data processing pipeline is presented.
SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on-board the European Environmental Satellite (Envisat)
provided spectrally resolved measurements in the wavelength ...range from 0.24 to 2.4 µm by looking into the Earth's atmosphere using different viewing geometries (limb, nadir, solar, and lunar occultation). These observations were
used to derive a multitude of parameters, in particular atmospheric trace gas amounts. In addition to radiance measurements solar spectral irradiances (SSIs) were measured on a daily basis.
The instrument was operating for nearly a decade, from August 2002 to April 2012. Due to the harsh space environment, it suffered from continuous optical degradation. As part of recent radiometric calibration activities
an optical (physical) model was introduced that describes the behaviour of the scanner unit of SCIAMACHY with time (Krijger et al., 2014).
This model approach accounts for optical degradation by assuming contamination layers on optical surfaces in the scanner unit. The variation in layer thicknesses of the various optical components is determined from the combination of solar measurements from different monitoring light paths available for SCIAMACHY.
In this paper, we present an optimisation of this degradation correction approach,
which in particular improves the solar spectral data.
An essential part of the modification is the use of measurements from SCIAMACHY's internal white light source (WLS) in combination with direct solar measurements.
The WLS, as an independent light source, therefore, gives an opportunity to better separate instrument variations and natural solar variability.
However, the WLS emission depends on its burning time and changes with time as well.
To use these measurements in the optimised degradation correction, the change in the WLS emission in space needs to be characterised first. The changes in the WLS with accumulated burning time
are in good agreement with detailed laboratory lamp studies by Sperling et al. (1996).
Although the optimised degradation-corrected SCIAMACHY SSIs still show some instrumental issues when compared to SSI measurements from other instruments and model reconstructions,
our study demonstrates the potential for the use of an internal WLS for degradation monitoring.
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This paper describes the in-flight calibration of the polarization response of the SCIAMACHY polarization measurement devices (PMDs) and a selected region of its science channels. With the lack of ...polarized calibration sources it is not possible to obtain such a calibration from dedicated calibration measurements. Instead, the earthshine itself, together with a simplified radiative transfer model (RTM), is used to derive time-dependent and measurement-configuration-dependent polarization sensitivities. The results are compared to an instrument model that describes the degradation of the instrument as a result of a slow buildup of contaminant layers on its elevation and azimuth scan mirrors. This comparison reveals significant differences between the model prediction and the data, suggesting an unforeseen change between on-ground and in-flight calibration in at least one of the polarization-sensitive components of the optical bench. The possibility of mechanisms other than scan mirror contamination contributing to the degradation of the instrument will be discussed. The data are consistent with a polarization phase shift occurring in the beam split prism used to divert the light coming from the telescope to the different channels and polarization measurement devices. The extension of the instrument degradation model with a linear retarder enables the determination of the relevant parameters to describe this phase shift and ultimately results in a significant improvement of the polarization measurements as well as the polarization response correction of measured radiances.
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The Tropospheric Monitoring Instrument (TROPOMI) is the single instrument on board the ESA Copernicus Sentinel-5 Precursor satellite. TROPOMI is a nadir-viewing imaging spectrometer with bands in the ...ultraviolet and visible, the near infrared and the shortwave infrared (SWIR). An accurate instrument spectral response function (ISRF) is required in the SWIR band where absorption lines of CO, methane and water vapor overlap. In this paper, we report on the determination of the TROPOMI-SWIR ISRF during an extensive on-ground calibration campaign. Measurements are taken with a monochromatic light source scanning the whole detector, using the spectrometer itself to determine the light intensity and wavelength. The accuracy of the resulting ISRF calibration key data is well within the requirement for trace-gas retrievals. Long-term in-flight monitoring of SWIR ISRF is achieved using five on-board diode lasers.
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The shortwave infrared (SWIR) spectrometer module of the Tropospheric
Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5
Precursor satellite, is used to measure atmospheric CO ...and methane columns.
For this purpose, calibrated radiance measurements are needed that are
minimally contaminated by instrumental stray light. Therefore, a method has
been developed and applied in an on-ground calibration campaign to
characterize stray light in detail using a monochromatic quasi-point light
source. The dynamic range of the signal was extended to more than 7 orders of magnitude by performing measurements with different exposure times,
saturating detector pixels at the longer exposure times. Analysis of the
stray light indicates about 4.4 % of the detected light is correctable stray
light. An algorithm was then devised and implemented in the operational data
processor to correct in-flight SWIR observations in near-real time, based on
Van Cittert deconvolution. The stray light is approximated by a far-field
kernel independent of position and wavelength and an additional kernel
representing the main reflection. Applying this correction significantly
reduces the stray-light signal, for example in a simulated dark forest scene
close to bright clouds by a factor of about 10. Simulations indicate that
this reduces the stray-light error sufficiently for accurate gas-column
retrievals. In addition, the instrument contains five SWIR diode lasers that
enable long-term, in-flight monitoring of the stray-light distribution.
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The ground segment for the ESA M4
Ariel
exoplanet space mission is introduced. The ground segment encompasses the framework necessary to support the development of the
Ariel
mission to launch, ...in-flight operations and calibration, data processing pipeline and data handling, including user support. The structure of the ground segment and assumed responsibilities between ESA and the
Ariel
mission consortium is explained, along with their interfaces. The operational phases for the mission are introduced, including the early commissioning/verification phases, the science operations and the calibration strategy. The smooth transition of the ground segment through the various pre/post launch mission phases to nominal operations will be paramount in guaranteeing the success, scientific return and impact of the
Ariel
mission. The expected science data products are defined and a representative data processing pipeline is presented.
SCIAMACHY on ENVISAT has meanwhile explored the Earth's atmosphere for more than 9 years. All subsystems perform well which is a precondition for maintaining a high optical and operational ...performance. Even the unavoidable in-orbit degradation due to the harsh space environment is lower than expected and can be largely compensated by sophisticated calibration and monitoring means. Because of the excellent status of both the platform and the instruments the ENVISAT mission has been extended until the end of 2013. Associated with this extension was a change of the orbit in late October 2010 and reconfiguring SCIAMACHY for achieving successful operations in the coming years.
Abstract
Neurons in primary visual cortex (V1) may not only signal current visual input but also relevant contextual information such as reward expectancy and the subject’s spatial position. Such ...contextual representations need not be restricted to V1 but could participate in a coherent mapping throughout sensory cortices. Here, we show that spiking activity coherently represents a location-specific mapping across auditory cortex (AC) and lateral, secondary visual cortex (V2L) of freely moving rats engaged in a sensory detection task on a figure-8 maze. Single-unit activity of both areas showed extensive similarities in terms of spatial distribution, reliability, and position coding. Importantly, reconstructions of subject position based on spiking activity displayed decoding errors that were correlated between areas. Additionally, we found that head direction, but not locomotor speed or head angular velocity, was an important determinant of activity in AC and V2L. By contrast, variables related to the sensory task cues or to trial correctness and reward were not markedly encoded in AC and V2L. We conclude that sensory cortices participate in coherent, multimodal representations of the subject’s sensory-specific location. These may provide a common reference frame for distributed cortical sensory and motor processes and may support crossmodal predictive processing.
Background
Pediatric renal tumors are often heterogeneous lesions with variable regions of distinct histopathology. Direct comparison between in vivo imaging and ex vivo histopathology might be ...useful for identification of discriminating imaging features.
Objective
This feasibility study explored the use of a patient-specific three-dimensional (3D)-printed cutting guide to ensure correct alignment (orientation and slice thickness) between magnetic resonance imaging (MRI) and histopathology.
Materials and methods
Before total nephrectomy, a patient-specific cutting guide based on each patient’s preoperative renal MRI was generated and 3-D printed, to enable consistent transverse orientation of the histological specimen slices with MRI slices. This was expected to result in macroscopic slices of 5 mm each. The feasibility of the technique was determined qualitatively, through questionnaires administered to involved experts, and quantitatively, based on structured measurements including overlap calculation using the dice similarity coefficient.
Results
The cutting guide was used in eight Wilms tumor patients receiving a total nephrectomy, after preoperative chemotherapy. The median age at diagnosis was 50 months (range: 4–100 months). The positioning and slicing of the specimens were rated overall as easy and the median macroscopic slice thickness of each specimen ranged from 5 to 6 mm. Tumor consistency strongly influenced the practical application of the cutting guide. Digital correlation of a total of 32 slices resulted in a median dice similarity coefficient of 0.912 (range: 0.530–0.960).
Conclusion
We report the feasibility of a patient-specific 3-D-printed MRI-based cutting guide for pediatric renal tumors, allowing improvement of the correlation of MRI and histopathology in future studies.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, VSZLJ, ZAGLJ
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