Since its launch in 2017, Tropospheric Monitoring Instrument (TROPOMI) on S-5P has provided very high quality data using daily global coverage for a number of key atmospheric trace gases. Over its ...first 1000 d in operation, the short-wave infrared (SWIR) module has been very stable, and the continuously monitored calibration has remained of high quality. This calibration relies on a combination of extensive pre-launch and post-launch measurements, complemented by regular monitoring of internal light sources and background measurements.
In this paper we present a method and results for independent validation of the SWIR module calibration and instrument stability by examining the signal stability of a sample of 23 pseudo-invariant calibration desert sites. The data covers over 2 years of operational data.
With a Lambertian surface assumption, the results show that the SWIR module has little to no instrument degradation down to an accuracy of about 0.3 % yr−1, validating results obtained from the internal calibration suite. The method presented here will be used as ongoing validation of the SWIR calibration.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
During its first year in operation the short-wave infrared (SWIR) Tropospheric Monitoring Instrument
(TROPOMI) was
calibrated in-flight and its performance was monitored.
In this paper we present the ...results of the in-flight calibration and the ongoing instrument monitoring. This includes the determination of the background signals, noise performance, instrument spectral response function (ISRF) stability, and stray-light stability. From these results, the number of incurred dead and bad
pixels due to cosmic-ray impacts is determined. The light-path transmission is checked by monitoring internal lamp and diffuser stabilities.
Due to its high sensitivity to Earth radiation on the eclipse side, the calibration strategy for the background (i.e. dark current and offset) monitoring was adjusted.
Trends over the first full year of nominal operations reveal a very stable SWIR module. The number of newly incurred dead and bad pixels
is less than 0.1 % over nearly a full year since the start of operations. Assuming linear degradation of various components, the SWIR module is expected to keep performing within expected parameters for the full operational lifetime.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Since its launch in 2017, Tropospheric Monitoring Instrument (TROPOMI) on S-5P has provided very high quality data using daily global coverage for a number of key atmospheric trace gases. Over its ...first 1000 d in operation, the short-wave infrared (SWIR) module has been very stable, and the continuously monitored calibration has remained of high quality. This calibration relies on a combination of extensive pre-launch and post-launch measurements, complemented by regular monitoring of internal light sources and background measurements. In this paper we present a method and results for independent validation of the SWIR module calibration and instrument stability by examining the signal stability of a sample of 23 pseudo-invariant calibration desert sites. The data covers over 2 years of operational data. With a Lambertian surface assumption, the results show that the SWIR module has little to no instrument degradation down to an accuracy of about 0.3 % yr.sup.-1, validating results obtained from the internal calibration suite. The method presented here will be used as ongoing validation of the SWIR calibration.
Full text
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The short-wave infrared (SWIR) module of the Tropospheric Monitoring Instrument (TROPOMI) on board the ESA's Sentinel-5 precursor (S5p) satellite has been very stable during its 5 years in orbit. ...Calibration was performed on the ground, complemented by measurements during in-flight instrument commissioning. The radiometric response and general performance of the SWIR module are monitored by on-board calibration sources. We show that after 5 years in orbit, TROPOMI-SWIR has continued to show excellent performance with degradation of at most 0.1 % in transmission and having lost less than 0.3 % of the detector pixels. Independent validation of the instrument calibration, via vicarious calibration, can be done through comparisons with ground-based reflectance data. In this work, ground measurements at the Railroad Valley Playa, a valley in central Nevada that is often used as a reference for satellite measurements, are used to perform vicarious calibration of the TROPOMI-SWIR measurements. This is done using dedicated measurement campaigns as well as automated reflectance measurements within the RADCALNET programme. As such, TROPOMI-SWIR is an excellent test case to explore the methodology of vicarious calibration applied to infrared spectroscopy. Using methodology developed for the vicarious calibration of the OCO-2 and GOSAT missions, the absolute radiometry of TROPOMI-SWIR performance is independently verified to be stable down to â¼ 6 %-10 % using the Railroad Valley when both the absolute and relative radiometric calibrations are applied. Differences with the on-board calibration originate from the bidirectional reflection distribution function (BRDF) effects of the desert surface, the large variety in viewing angles, and the different sizes of footprints of the TROPOMI pixels. Vicarious calibration is shown to be an additional valuable tool in validating radiance-level performances of infrared instruments such as TROPOMI-SWIR in the field of atmospheric composition. It remains clear that for instruments of similar design and resolution to TROPOMI-SWIR, on-board calibration sources will continue to provide superior results due to the limitations of the vicarious calibration method.
Full text
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
During its first year in operation the short-wave infrared (SWIR) Tropospheric Monitoring Instrument (TROPOMI) was calibrated in-flight and its performance was monitored. In this paper we present the ...results of the in-flight calibration and the ongoing instrument monitoring. This includes the determination of the background signals, noise performance, instrument spectral response function (ISRF) stability, and stray-light stability. From these results, the number of incurred dead and bad pixels due to cosmic-ray impacts is determined. The light-path transmission is checked by monitoring internal lamp and diffuser stabilities. Due to its high sensitivity to Earth radiation on the eclipse side, the calibration strategy for the background (i.e. dark current and offset) monitoring was adjusted. Trends over the first full year of nominal operations reveal a very stable SWIR module. The number of newly incurred dead and bad pixels is less than 0.1 % over nearly a full year since the start of operations. Assuming linear degradation of various components, the SWIR module is expected to keep performing within expected parameters for the full operational lifetime.
Full text
Available for:
IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Mechanical ventilation induces diaphragm muscle atrophy, which plays a key role in difficult weaning from mechanical ventilation. The signaling pathways involved in ventilator-induced diaphragm ...atrophy are poorly understood. The current study investigated the role of Toll-like receptor 4 signaling in the development of ventilator-induced diaphragm atrophy.
Unventilated animals were selected for control: wild-type (n = 6) and Toll-like receptor 4 deficient mice (n = 6). Mechanical ventilation (8 h): wild-type (n = 8) and Toll-like receptor 4 deficient (n = 7) mice.Myosin heavy chain content, proinflammatory cytokines, proteolytic activity of the ubiquitin-proteasome pathway, caspase-3 activity, and autophagy were measured in the diaphragm.
Mechanical ventilation reduced myosin content by approximately 50% in diaphragms of wild-type mice (P less than 0.05). In contrast, ventilation of Toll-like receptor 4 deficient mice did not significantly affect diaphragm myosin content. Likewise, mechanical ventilation significantly increased interleukin-6 and keratinocyte-derived chemokine in the diaphragm of wild-type mice, but not in ventilated Toll-like receptor 4 deficient mice. Mechanical ventilation increased diaphragmatic muscle atrophy factor box transcription in both wild-type and Toll-like receptor 4 deficient mice. Other components of the ubiquitin-proteasome pathway and caspase-3 activity were not affected by ventilation of either wild-type mice or Toll-like receptor 4 deficient mice. Mechanical ventilation induced autophagy in diaphragms of ventilated wild-type mice, but not Toll-like receptor 4 deficient mice.
Toll-like receptor 4 signaling plays an important role in the development of ventilator-induced diaphragm atrophy, most likely through increased expression of cytokines and activation of lysosomal autophagy.
A new retrieval method to detect steep temperature gradients between the convective overshoots of cumulonimbus clouds and the surrounding cirrus has been applied to determine gradients and their ...orientation in the image plane of infrared data of the advanced very high resolution radiometer (AVHRR). These orientations are used to derive cloud elevations which are brightened by the Sun or are in shadow, which strongly affects the visible signal. The impact of temperature gradients on the visible radiances is illustrated by two examples that indicate deep convective overshoots. Both examples show that the illuminated side of the overshoots can exceed the cloud top reflectivity by 50%, while the shadows account for <50% of the cloud top reflectance. The shadows usually extend several pixels beyond the base of the overshoots. Here we show that statistical analyses of cloud optical depth are affected by the cloud top structure, based on 1 month of high‐resolution AVHRR satellite data. The contribution of shadow side pixels with steep temperature gradients (≥16 K) can exceed 30% for small optical depths (<3). The contribution of illuminated sides of cloud top structures and cloud sides with steep temperature gradients can exceed 70% for large optical depths (>32).
A new method is introduced to identify active convective cloud regions in high‐resolution AVHRR satellite data. This method is developed to overcome several limitations of existing visible/infrared ...techniques. Steep temperature gradients between the convective overshoots of cumulonimbus clouds and the surrounding cirrus are used to identify the edges of active convective regions. The limitations of previous methods are shown using up to 1.1 km resolution AVHRR data of the NOAA‐11 and NOAA‐12 satellites collected during the Central Equatorial Pacific Experiment (CEPEX), a measurement campaign that took place over the central Pacific Ocean between March 7 and April 6, 1993. Differences in the identification of convection between the new algorithm and the existing algorithms are clarified by a case study and further illustrated by three collocations between NOAA‐11 and NOAA‐12 overpasses and observations made with the Massachusetts Institute of Technology (MIT) 5 cm Doppler radar onboard the research vessel R/V Vickers.
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