scholarly journals Determination of the TROPOMI-SWIR instrument spectral response function

2018 ◽  
Vol 11 (7) ◽  
pp. 3917-3933 ◽  
Author(s):  
Richard M. van Hees ◽  
Paul J. J. Tol ◽  
Sidney Cadot ◽  
Matthijs Krijger ◽  
Stefan T. Persijn ◽  
...  
Keyword(s):  
Response Function ◽  
Near Infrared ◽  
Spectral Response ◽  
Monochromatic Light ◽  
Imaging Spectrometer ◽  
Swir Band ◽  
Shortwave Infrared ◽  
Single Instrument

Abstract. 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.

scholarly journals New method to determine the instrument spectral response function, applied to TROPOMI-SWIR

2017 ◽  
Author(s):  
Richard M. van Hees ◽  
Paul J. J. Tol ◽  
Sidney Cadot ◽  
Matthijs Krijger ◽  
Stefan T. Persijn ◽  
...  
Keyword(s):  
Response Function ◽  
Near Infrared ◽  
Spectral Response ◽  
Short Wave ◽  
Trace Gas ◽  
Imaging Spectrometer ◽  
Swir Band ◽  
Novel Method ◽  
Single Instrument

Abstract. The Tropospheric Monitoring Instrument (TROPOMI) is the single instrument on board of 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 short-wave 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. Therefore a novel method for ISRF determination for an imaging spectrometer was developed and applied to the TROPOMI-SWIR band. The ISRF of all detector pixels of the SWIR spectrometer has been measured during an on-ground calibration campaign. The accuracy of the derived ISRF is well within the requirement for accurate trace-gas retrievals. Long-term in-flight monitoring of the ISRF is guaranteed by the presence of five SWIR diode lasers.

scholarly journals Radiometric Comparison of 1.6-μm CO2 Absorption Band of Greenhouse Gases Observing Satellite (GOSAT) TANSO-FTS with Suomi-NPP VIIRS SWIR Band

2016 ◽  
Vol 33 (7) ◽  
pp. 1443-1453
Author(s):  
Sirish Uprety ◽  
Changyong Cao
Keyword(s):  
Greenhouse Gases ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Co2 Absorption ◽  
New Methods ◽  
Swir Band ◽  
Long Term Trends ◽  
Global Concern ◽  
Shortwave Infrared

AbstractAn atmospheric CO2 increase has become a progressively important global concern in recent past decades. Since the 1950s, the Keeling curve has documented the atmospheric CO2 increase as well as seasonal variations, which also intrigued scientists to develop new methods for global CO2 measurements from satellites. One of the dedicated satellite missions is the CO2 measurement in the 1.6-μm shortwave infrared spectra by the Greenhouse Gases Observing Satellite (GOSAT) Thermal and Near Infrared Sensor for Carbon Observations–Fourier Transform Spectrometer (TANSO-FTS) instrument. While this spectral region has unique advantages in detecting lower-trophosphere CO2, there are many challenges because it relies on accurate measurements of reflected solar radiance from Earth’s surface. Therefore, the calibration of the TANSO-FTS CO2 has a direct impact on the CO2 retrievals and its long-term trends. Coincidently, the Suomi-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) 1.6-μm band spectrally overlaps with the TANSO-FTS CO2 band, and both satellites are in orbit with periodical simultaneous nadir overpass measurements. This study performs an intercomparison of VIIRS and the TANSO-FTS CO2 band in an effort to evaluate and improve the radiometric consistency. Understanding the differences provides feedback on how well the GOSAT TANSO-FTS is performing over time, which is critical to ensure a well-calibrated, stable, and bias-free CO2 product.

scholarly journals The operational methane retrieval algorithm for TROPOMI

2016 ◽  
Vol 9 (11) ◽  
pp. 5423-5440 ◽  
Author(s):  
Haili Hu ◽  
Otto Hasekamp ◽  
André Butz ◽  
André Galli ◽  
Jochen Landgraf ◽  
...  
Keyword(s):  
Response Function ◽  
Near Infrared ◽  
Spectral Response ◽  
Retrieval Algorithm ◽  
Model Errors ◽  
Instrument Calibration ◽  
Atmospheric Scattering ◽  
Accuracy And Precision ◽  
Land Surfaces ◽  
Shortwave Infrared

Abstract. This work presents the operational methane retrieval algorithm for the Sentinel 5 Precursor (S5P) satellite and its performance tested on realistic ensembles of simulated measurements. The target product is the column-averaged dry air volume mixing ratio of methane (XCH4), which will be retrieved simultaneously with scattering properties of the atmosphere. The algorithm attempts to fit spectra observed by the shortwave and near-infrared channels of the TROPOspheric Monitoring Instrument (TROPOMI) spectrometer aboard S5P.The sensitivity of the retrieval performance to atmospheric scattering properties, atmospheric input data and instrument calibration errors is evaluated. In addition, we investigate the effect of inhomogeneous slit illumination on the instrument spectral response function. Finally, we discuss the cloud filters to be used operationally and as backup.We show that the required accuracy and precision of  < 1 % for the XCH4 product are met for clear-sky measurements over land surfaces and after appropriate filtering of difficult scenes. The algorithm is very stable, having a convergence rate of 99 %. The forward model error is less than 1 % for about 95 % of the valid retrievals. Model errors in the input profile of water do not influence the retrieval outcome noticeably. The methane product is expected to meet the requirements if errors in input profiles of pressure and temperature remain below 0.3 % and 2 K, respectively. We further find that, of all instrument calibration errors investigated here, our retrievals are the most sensitive to an error in the instrument spectral response function of the shortwave infrared channel.

scholarly journals Radiometric Intercomparison between Suomi-NPP VIIRS and Aqua MODIS Reflective Solar Bands Using Simultaneous Nadir Overpass in the Low Latitudes

2013 ◽  
Vol 30 (12) ◽  
pp. 2720-2736 ◽  
Author(s):  
Sirish Uprety ◽  
Changyong Cao ◽  
Xiaoxiong Xiong ◽  
Slawomir Blonski ◽  
Aisheng Wu ◽  
...  
Keyword(s):  
Infrared Imaging ◽  
Atmospheric Transmission ◽  
Imaging Spectrometer ◽  
The North ◽  
Swir Band ◽  
Low Latitudes ◽  
Moderate Resolution ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Shortwave Infrared ◽  
The Impact

Abstract On-orbit radiometric performance of the Suomi National Polar-Orbiting Partnership (Suomi-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) is studied using the extended simultaneous nadir overpass (SNO-x) approach. Unlike the traditional SNO analysis of data in the high latitudes, this study extends the analysis to the low latitudes—in particular, over desert and ocean sites with relatively stable and homogeneous radiometric properties—for intersatellite comparisons. This approach utilizes a pixel-by-pixel match with an efficient geospatial matching algorithm to map VIIRS data into the Moderate Resolution Imaging Spectroradiometer (MODIS). VIIRS moderate-resolution bands M-1 through M-8 are compared with Aqua MODIS equivalent bands to quantify radiometric bias over the North African desert and over the ocean. Biases exist between VIIRS and MODIS in several bands, primarily because of spectral differences as well as possible calibration uncertainties, residual cloud contamination, and bidirectional reflectance distribution function (BRDF). The impact of spectral differences on bias is quantified by using the Moderate Resolution Atmospheric Transmission (MODTRAN) and hyperspectral measurements from the Earth Observing-1 (EO-1) Hyperion and the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS). After accounting for spectral differences and bias uncertainties, the VIIRS radiometric bias over desert agrees with MODIS measurements within 2% except for the VIIRS shortwave infrared (SWIR) band M-8, which indicates a nearly 3% bias. Over ocean, VIIRS agrees with MODIS within 2% by the end of January 2013 with uncertainty less than 1%. Furthermore, VIIRS bias relative to MODIS is also computed at the Antarctica Dome C site for validation and the result agrees well within 1% with the bias estimated using SNO-x over desert.

scholarly journals Assessment of Sun photometer Langley calibration at the high-elevation sites Mauna Loa and Izaña

2018 ◽  
Author(s):  
Carlos Toledano ◽  
Ramiro González ◽  
David Fuertes ◽  
Emilio Cuevas ◽  
Thomas F. Eck ◽  
...  
Keyword(s):  
Near Infrared ◽  
Quality Criteria ◽  
High Elevation ◽  
High Mountain ◽  
Atmospheric Variability ◽  
Mauna Loa ◽  
Clear Sky ◽  
Calibration Uncertainty

Abstract. The aim of this paper is to analyze the suitability of the high-mountain stations Mauna Loa and Izaña for Langley plot calibration of Sun photometers. Thus the aerosol optical depth (AOD) characteristics and seasonality, as well as the cloudiness, have been investigated in order to provide a robust estimation of the calibration accuracy, as well as the number of days that are suitable for Langley calibrations. The data used for the investigations belong to AERONET and GAW-PFR networks, which maintain reference Sun photometers at these stations with long measurement records: 22 years at Mauna Loa and 15 years at Izaña. In terms of clear sky and stable aerosol conditions, Mauna Loa (3397 m a.s.l.) exhibits on average of 377 Langleys (243 morning and 134 afternoon) per year suitable for Langley plot calibration, whereas Izaña (2373 m a.s.l.) shows 343 Langleys (187 morning and 155 afternoon) per year. The background AOD (500 nm wavelength) values, on days that are favorable for Langley calibrations, are in the range 0.01–0.02 throughout the year, with well-defined seasonality that exhibits a spring maximum at both stations plus a slight summer increase at Izaña. The statistical analysis of the long-term determination of extraterrestrial signals yields to a calibration uncertainty of ~ 0.2–0.5 %, being this uncertainty smaller in the near infrared and larger in the ultraviolet wavelengths. This is due to atmospheric variability that cannot be reduced based only on quality criteria of individual Langely plots.

scholarly journals Hyperspectral Monitoring of Non-Native Tropical Grasses over Phenological Seasons

2021 ◽  
Vol 13 (4) ◽  
pp. 738
Author(s):  
Kirrilly Pfitzner ◽  
Renee Bartolo ◽  
Tim Whiteside ◽  
David Loewensteiner ◽  
Andrew Esparon
Keyword(s):  
Near Infrared ◽  
Spectral Response ◽  
Grass Species ◽  
Wet Season ◽  
Native Grass ◽  
Data Collections ◽  
Spectral Patterns ◽  
Shortwave Infrared ◽  
Over Time

The miniaturisation of hyperspectral sensors for use on drones has provided an opportunity to obtain hyper temporal data that may be used to identify and monitor non-native grass species. However, a good understanding of variation in spectra for species over time is required to target such data collections. Five taxological and morphologically similar non-native grass species were hyper spectrally characterised from multitemporal spectra (17 samples over 14 months) over phenological seasons to determine their temporal spectral response. The grasses were sampled from maintained plots of homogenous non-native grass cover. A robust in situ standardised sampling method using a non-imaging field spectrometer measuring reflectance across the 350–2500 nm wavelength range was used to obtain reliable spectral replicates both within and between plots. The visible-near infrared (VNIR) to shortwave infrared (SWIR) and continuum removed spectra were utilised. The spectra were then resampled to the VNIR only range to simulate the spectral response from more affordable VNIR only hyperspectral scanners suitable to be mounted on drones. We found that species were separable compared to similar but different species. The spectral patterns were similar over time, but the spectral shape and absorption features differed between species, indicating these subtle characteristics could be used to distinguish between species. It was the late dry season and the end of the wet season that provided maximum separability of the non-native grass species sampled. Overall the VNIR-SWIR results highlighted more dissimilarity for unlike species when compared to the VNIR results alone. The SWIR is useful for discriminating species, particularly around water absorption.

scholarly journals Parameterizing the instrumental spectral response function and its changes by a Super-Gaussian and its derivatives

2016 ◽  
Author(s):  
Steffen Beirle ◽  
Johannes Lampel ◽  
Christophe Lerot ◽  
Holger Sihler ◽  
Thomas Wagner
Keyword(s):  
Response Function ◽  
Cross Sections ◽  
Spectral Response ◽  
Gaussian Function ◽  
Computation Time ◽  
Satellite Orbit ◽  
Spectral Calibration ◽  
Instrumental Resolution ◽  
Derivatives Of

Abstract. The instrumental spectral response function (ISRF) is a key quantity in DOAS analysis, as it is needed for wavelength calibration and for the convolution of trace gas cross-sections to instrumental resolution. While it can generally be measured using monochromatic stimuli, it is often parameterized in order to merge different calibration measurements and to plainly account for its wavelength dependency. For some instruments, the ISRF can be described appropriately by a Gaussian function, while for others, dedicated, complex parameterizations with several parameters have been developed. Here we propose to parameterize the ISRF as a "Super Gaussian", which can reproduce a variety of shapes, from point-hat to boxcar shape, by just adding one parameter to the "classical" Gaussian. The Super Gaussian turned out to describe the ISRF of various DOAS instruments well, including the satellite instruments GOME-2, OMI, and TROPOMI. In addition, the Super Gaussian allows for a straightforward parametrization of the effect of ISRF changes, which can occur on long-term scales as well as e.g.~during one satellite orbit, and impair the spectral analysis if ignored. In order to account for such changes, spectral structures are derived from the derivatives of the Super Gaussian, which are afterwards just scaled during spectral calibration or DOAS analysis. This approach significantly improves the fit quality compared to setups with fixed ISRF, without drawbacks on computation time due to the applied linearization. In addition, the wavelength dependency of the ISRF can be accounted for by accordingly derived spectral structures in an easy, fast, and robust way.

scholarly journals The operational methane retrieval algorithm for TROPOMI

2016 ◽  
Author(s):  
Haili Hu ◽  
Otto Hasekamp ◽  
André Butz ◽  
André Galli ◽  
Jochen Landgraf ◽  
...  
Keyword(s):  
Response Function ◽  
Near Infrared ◽  
Spectral Response ◽  
Short Wave ◽  
Retrieval Algorithm ◽  
Model Errors ◽  
Instrument Calibration ◽  
Atmospheric Scattering ◽  
Accuracy And Precision ◽  
Land Surfaces

Abstract. This work presents the operational methane retrieval algorithm for the Sentinel-5 Precursor (S5-P) satellite and its performance tested on realistic ensembles of simulated measurements. The target product is the column-averaged dry air volume mixing ratio of methane (XCH4), which will be retrieved simultaneously with scattering properties of the atmosphere. The algorithm attempts to fit spectra observed by the shortwave and near-infrared channels of the TROPOMI spectrometer aboard S5-P. The sensitivity of the retrieval performance to atmospheric scattering properties, atmospheric input data and instrument calibration errors is evaluated. Also, we investigate the effect of inhomogeneous slit illumination on the instrument spectral response function. Finally, we discuss the cloud filters to be used operationally and as backup. We show that the required accuracy and precision of < 1 % for the XCH4 product are met for clear sky measurements over land surfaces and after appropriate filtering of difficult scenes. The algorithm is very stable having a convergence rate of 99 %. The forward model error is less than 1 % for about 95 % of the valid retrievals. Model errors in the input profile of water do not influence the retrieval outcome noticeably. The methane product is expected to meet the requirements if errors in input profiles of pressure and temperature remain below 0.3 % and 2 K, respectively. We find further that, of all instrument calibration errors investigated here, our retrievals are the most sensitive to an error in the instrument spectral response function of the short-wave infrared channel.

scholarly journals IMPLEMENTATION STRATEGY OF VISIBLE AND NEAR-INFRARED IMAGING SPECTROMETER ON YUTU-2 ROVER BASED ON VISION MEASUREMENT TECHNOLOGY

2020 ◽  
Vol XLIII-B3-2020 ◽  
pp. 1191-1197
Author(s):  
T. Yu ◽  
Z. Liu ◽  
Z. Rong ◽  
Y. Wang ◽  
J. Wang ◽  
...  
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Measurement Technology ◽  
The Moon ◽  
Near Infrared Imaging ◽  
Imaging Spectrometer ◽  
Precise Control ◽  
Vision Measurement ◽  
Communication Condition ◽  
Shortwave Infrared

Abstract. The Chang'e-4 successfully landed on the far side of the moon in January 2019. By the 12th lunar day, its Yutu-2 rover had achieved a breakthrough travel distance of greater than 300 m. A visible and near-infrared imaging spectrometer (VNIS), consisting of a visible and near-infrared (VNIR) imaging spectrometer and a shortwave infrared (SWIR) spectrometer was used for detecting mineralogical compositions of lunar-surface materials. Because VNIS is fixed on the front of the rover, and the field-of-view (FOV) of VNIR and SWIR are small (8.5° and 3.6° respectively), approaching and accurately pointing at the specific science target depend completely on the precise control of the moving rover.In this paper, a successful method of VNIS target detection based on vision measurement is proposed. First, the accurate position of the target is calculated via navigation camera imaging. Then, the moving path is planned by considering the terrain environment, illumination, communication condition, and other constraints. After the rover moves to the designed position, the binocular imaging of the hazard-avoidance cameras are activated, the detection direction and forward distance are calculated according to the images, and the FOV trajectory of the VINS is predicted while moving. Finally, by choosing the required moving control parameters, the imaging field of the VINS accurately cover the detected targets visually.These methods have been verified many times, and the results show that they are effective and feasible. The research results based on the VNIS data have successfully revealed the material composition on the far side of the moon and have deepened human understanding of its formation and evolution.

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