http://www.majidkiavarz.com/files/Satellite-derived%20land%20surface%20temperature%20Current%20status%20and%20perspectives.pdf

Satellite-derived land surface temperature: Current status and perspectives

New refinements and validation of the collection-6 MODIS land-surface temperature/emissivity product

Launched in February 2013, the Landsat-8 carries on-board the Thermal Infrared Sensor (TIRS), a two-band thermal pushbroom imager, to maintain the thermal imaging capability of the Landsat program. The TIRS bands are centered at roughly 10.9 and 12 μm (Bands 10 and 11 respectively). They have 100 m spatial resolution and image coincidently with the Operational Land Imager (OLI), also on-board Landsat-8. The TIRS instrument has an internal calibration system consisting of a variable temperature blackbody and a special viewport with which it can see deep space; a two point calibration can be performed twice an orbit. Immediately after launch, a rigorous vicarious calibration program was started to validate the absolute calibration of the system. The two vicarious calibration teams, NASA/Jet Propulsion Laboratory (JPL) and the Rochester Institute of Technology (RIT), both make use of buoys deployed on large water bodies as the primary monitoring technique. RIT took advantage of cross-calibration opportunity soon after launch when Landsat-8 and Landsat-7 were imaging the same targets within a few minutes of each other to perform a validation of the absolute calibration. Terra MODIS is also being used for regular monitoring of the TIRS absolute calibration. The buoy initial results showed a large error in both bands, 0.29 and 0.51 W/m2·sr·μm or −2.1 K and −4.4 K at 300 K in Band 10 and 11 respectively, where TIRS data was too hot. A calibration update was recommended for both bands to correct for a bias error and was implemented on 3 February 2014 in the USGS/EROS processing system, but the residual variability is still larger than desired for both bands (0.12 and 0.2 W/m2·sr·μm or 0.87 and 1.67 K at 300 K). Additional work has uncovered the source of the calibration error: out-of-field stray light. While analysis continues to characterize the stray light contribution, the vicarious calibration work proceeds. The additional data have not changed the statistical assessment but indicate that the correction (particularly in band 11) is probably only valid for a subset of data. While the stray light effect is small enough in Band 10 to make the data useful across a wide array of applications, the effect in Band 11 is larger and the vicarious results suggest that Band 11 data should not be used where absolute calibration is required.

/pdf/landsat-8-thermal-infrared-sensor-tirs-vicarious-radiometric-449hwjbqrg.pdf

Landsat-8 Thermal Infrared Sensor (TIRS) Vicarious Radiometric Calibration

Disaggregation of remotely sensed land surface temperature: Literature survey, taxonomy, issues, and caveats

Terra Moderate Resolution Imaging Spectroradiometer (MODIS) has made continuous global observations for more than six years since its launch in December 1999. MODIS has 36 spectral bands: 20 reflective solar bands (RSBs) with wavelengths from 0.41-2.2 mum and 16 thermal emissive bands with wavelengths from 3.7-14.4 mum. It is a cross-track scanning radiometer that collects data at three nadir spatial resolutions: 0.25 km (2 bands), 0.5 km (5 bands), and 1 km (29 bands). An onboard solar diffuser (SD) and an SD stability monitor (SDSM) are used biweekly for RSB on-orbit radiometric calibration. Another onboard calibrator (OBC), a spectroradiometric calibration assembly, is used periodically to evaluate and monitor RSB spatial and spectral performance. In addition to measurements made using OBCs, lunar observations at nearly identical phase angles are used to track RSB calibration stability. This paper provides an overview of MODIS RSB on-orbit calibration algorithms and operational activities. It discusses sensor characteristics that could impact RSB calibration accuracy and data product quality, including degradation of the SD bidirectional reflectance factor (BRF), degradation of the scan mirror reflectance in the visible spectral region, and changes in operational configuration. The Terra MODIS OBCs have performed well in monitoring SD degradation and tracking changes in RSB response. Band 8 (0.41 mum) has experienced the largest response decrease with an approximate annual rate of 4.5% (mirror side 1). Band 9 (0.44 mum) has an annual response decrease of about 2.3% (mirror side 1). For most RSB bands with wavelengths greater than 0.5 mum, the annual response changes are generally less than 1.0%. Results from the SDSM on-orbit observations show that the SD BRF also has a similar wavelength-dependent degradation, with the largest degradation appearing at the shortest wavelengths. Among the 330 RSB detectors, there are no inoperable detectors, and only a few noisy detectors have appeared postlaunch

Multiyear On-Orbit Calibration and Performance of Terra MODIS Reflective Solar Bands

The mechanism of crosstalk phenomena in the shortwave infrared (SWIR) subsystem of the Advanced Spaceborne Thermal Emission and Reflection Radiometer, which has six bands in the wavelength region of 1.6-2.43 /spl mu/m, is investigated. It is found that light incident to band 4 is reflected at the detector and the filter boundary, and then transported to other bands by multiple reflections in the focal plane area. A crosstalk correction algorithm is developed to improve the spectral separation performance of SWIR. Parameters of the crosstalk model, i.e., the amount of stray light and its area of influence, are determined by image analysis. By careful investigation of SWIR images around peninsulas, lakes, and islands, the crosstalk model is validated. Therefore, the correction algorithm is implemented in the preprocessing of higher level data products.

Validation of a crosstalk correction algorithm for ASTER/SWIR

In December 1999, the first Moderate Resolution Imaging Spectroradiometer (MODIS) instrument and an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument were launched into polar orbit on the Terra spacecraft. Both instruments measure surface radiance, which requires that they are calibrated and validated in flight. In-flight validation is essential to independently verify that instrument calibration correctly compensates for any changes in instrument response over time. In order to meet this requirement, an automated validation site was established at Lake Tahoe on the California/Nevada border in 1999 to validate the ASTER and MODIS thermal infrared (TIR, 7-13 mum) and MODIS mid infrared (MIR, 3-5 mum) land-monitoring channels. Daytime and nighttime data were used to validate the TIR channels, and only nighttime data were used to validate the MIR channels to avoid any reflected solar contribution. Sixty-nine ASTER scenes and 155 MODIS-Terra scenes acquired between years 2000 and 2005 with near-nadir views were validated. The percent differences between the predicted and instrument at-sensor radiances for ASTER channels 10-14 were 0.165plusmn0.776, 0.103plusmn0.613, -0.305plusmn0.613, -0.252plusmn0.464, and -0.118plusmn0.489, respectively. The percent differences for MODIS-Terra channels 20, 22, 23, 29, 31, and 32 were -1.375plusmn0.973, -1.743plusmn1.027, -0.898plusmn0.970, 0.082plusmn0.631, 0.044plusmn0.541, and 0.151plusmn0.563, respectively. The results indicate that the TIR at-sensor radiances from ASTER and MODIS-Terra have met the preflight radiometric calibration accuracy specification and provide well-calibrated data sets that are suitable for measuring absolute change. The results also show that the at-sensor radiances from the MODIS-Terra MIR channels have greater bias than expected based on the preflight radiometric calibration accuracy specification

Absolute Radiometric In-Flight Validation of Mid Infrared and Thermal Infrared Data From ASTER and MODIS on the Terra Spacecraft Using the Lake Tahoe, CA/NV, USA, Automated Validation Site

The water vapor scaling (WVS) method involves an atmospheric correction algorithm for thermal infrared (TIR) multispectral data, designed mainly for the five TIR spectral bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the Terra satellite. First, this method is improved for better applicability to ASTER/TIR imagery. The major improvement is the determination of a water vapor scaling factor on a band-by-band basis, which can reduce most of the errors induced by various factors such as algorithm assumptions. Next, the WVS method is validated by assessing the surface temperature and emissivity retrieved for a global-based simulation model (416 448 conditions), 183 ASTER scenes selected globally, and ASTER scenes from two test sites, Hawaii Island and Tokyo Bay. In situ lake surface temperatures measured in 13 vicarious calibration experiments, Moderate Resolution Imaging Spectroradiometer sea surface temperature products, and a climatic lake temperature are also used in validation. All the results indicate that although the ASTER/TIR standard atmospheric correction algorithm performs less well in humid conditions, the WVS method will provide more accurate retrieval of surface temperature and emissivity in most conditions including notably humid conditions. The expected root mean square error is about 0.6 K in temperature. Since the WVS method will be degraded by errors in gray pixel selection and cloud detection, these processing steps should be applied accurately.

Accurate atmospheric correction of ASTER thermal infrared imagery using the WVS method

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on the Terra satellite has five bands in the thermal infrared (TIR) spectral region between 8-12 /spl mu/m. The TIR bands have been regularly validated in-flight using ground validation targets. Validation results are presented from 79 experiments conducted under clear sky conditions. Validation involved predicting the at-sensor radiance for each band using a radiative transfer model, driven by surface and atmospheric measurements from each experiment, and then comparing the predicted radiance with the ASTER measured radiance. The results indicate the average difference between the predicted and the ASTER measured radiances was no more than 0.5% or 0.4 K in any TIR band, demonstrating that the TIR bands have exceeded the preflight design accuracy of <1 K for an at-sensor brightness temperature range of 270-340 K. The predicted and the ASTER measured radiances were then used to assess how well the onboard calibration accounted for any changes in both the instrument gain and offset over time. The results indicate that the gain and offset were correctly determined using the onboard blackbody, and indicate a responsivity decline over the first 1400 days of the Terra mission.

Vicarious calibration of ASTER thermal infrared bands

Thermal infrared (TIR) multispectral data over land can be atmospherically corrected by radiative transfer calculations combined with global assimilated data from a weather forecast system. This approach is advantageous to operational processing but is not accurate. A new atmospheric correction algorithm with global assimilated data, a water vapor scaling (WVS) method, has improved results. In this algorithm, the accuracy of global assimilated data is markedly improved on a pixel-by-pixel basis as follows: (1) selecting gray pixels from an image; (2) estimating the scaling factors for the water-vapor profiles of gray pixels by an improved multichannel algorithm; (3) estimating the scaling factors for the water-vapor profiles of nongray pixels by horizontal interpolation; and (4) improving the water-vapor profiles of all pixels with the scaling factors. The proposed method can be applied if the image has one or more gray pixels. The simulation results for the advanced spaceborne thermal emission and reflection radiometer (ASTER) TIR subsystem show that the proposed method reduces errors on air temperature profiles as well as on water-vapor profiles and is as accurate as atmospheric correction with radiosonde measurements.

Hideyuki Tonooka

Papers

Validation of a crosstalk correction algorithm for ASTER/SWIR

Absolute Radiometric In-Flight Validation of Mid Infrared and Thermal Infrared Data From ASTER and MODIS on the Terra Spacecraft Using the Lake Tahoe, CA/NV, USA, Automated Validation Site

Accurate atmospheric correction of ASTER thermal infrared imagery using the WVS method

Vicarious calibration of ASTER thermal infrared bands

An atmospheric correction algorithm for thermal infrared multispectral data over land-a water-vapor scaling method