Xingfa Gu

Front Matter: Volume 10402

ix Conference Committee PLENARY SESSION 7081 02 Measurement science for climate remote sensing [7081-53] G. T. Fraser, S. W. Brown, R. U. Datla, B. C. Johnson, K. R. Lykke, J. P. Rice, National Institute of Standards and Technology (United States) PRELAUNCH CALIBRATION 7081 03 Vacuum compatible large uniform-radiance source for ground calibration of satellite cameras inside a thermal vacuum environment [7081-01] A. V. Arecchi, SphereOptics LLC (United States); S. Pal, Indian Space Research Organization (India); J. W. Jablonski, M. Gervais, M. Gugliotta, SphereOptics LLC (United States); H. Seth, A. Bhardwaj, H. S. Sahoo, Indian Space Research Organization (India) 7081 04 Design and validation of a transfer radiometer [7081-02] N. Anderson, K. Thome, S. Biggar, J. S. Czapla-Myers, College of Optical Sciences, Univ. of Arizona (United States) 7081 06 Pre-launch performance characterization of EOS-C camera [7081-04] Y.-W. Choi, S. Kang, J. Yun, J. Kim, M. Kang, S. Jeong, H. Kim, J. Song, E.-E. Kim, Satrec Initiative (South Korea) 7081 07 BRDF study of gray-scale Spectralon [7081-05] G. T. Georgiev, Science Systems and Applications, Inc. (United States); J. J. Butler, NASA Goddard Space Flight Ctr. (United States) 7081 08 Pre-launch optical tests of MODIS and MISR [7081-06] E. Waluschka, NASA Goddard Space Flight Ctr. (United States); C. J. Bruegge, Jet Propulsion Lab. (United States); X. Xiong, NA SA Goddard Space Flight Ctr. (United States) MODIS I 7081 09 MODIS along-scan direction Line Spread Function (LSF) modeling and verification using the Integration and Alignment Collimator (IAC) [7081-07] N. Che, T. Choi, Science Systems and Applications, Inc. (United States); X. Xiong, NASA Goddard Space Flight Ctr. (United States); D. Moyer, Aerospace Corp. (United States) 7081 0A On-orbit aqua MODIS modulation transfer function trending in along-scan from the Spectro-Radiometric Calibration Assembly [7081-08] T. Choi, N. Che, Science Systems and Applications, Inc. (United States); X. Xiong, NASA Goddard Space Flight Ctr. (United States)

Improvements in the calibration of the SNPP VIIRS day-night band (Conference Presentation).

We present improvements to the on-orbit calibration of the day-night band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi National Polar-orbiting Partnership (SNPP) satellite. Most important among the improvements is the expansion of the “sweet spot” from 4 o to 7.8o to increase the number of the fully illuminated scans for calcuation. This allows for the completion of the on-orbit calibration using the solar diffuser (SD) within one orbit instead multiple orbits as required in the current standard approach. The bidirectional reflectance factor (BRF) of the SD and the vignetting function (VF) describing the transmission of the attenuation screen in front of the SD port are also examined and improved. Additional enhancements include the analysis of the out-of-band (OOB) contribution of the relative spectral response (RSR) and the adaptation of the previously improved SD degradation. The result shows that the improved DNB calibration coefficients are more stable, smooth and less noisy.

Electronic crosstalk effect in SNPP VIIRS thermal emissive bands (Conference Presentation).

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) spacecraft has been on orbit for more than five years. Pronounced striping in Earth view (EV) images and obvious discontinuity in the EV brightness temperature (BT) of the thermal emissive bands (TEB) during the blackbody (BB) warm-up cool-down (WUCD) calibration have been found since launch but the root-cause of the phenomena has not yet been identified. Meanwhile, recent studies of the MODerate-resolution Imaging Spectroradiometer (MODIS) long-wave infrared (LWIR) photovoltaic (PV) bands demonstrate that crosstalk effect induces the same erroneous features. In this paper, it is shown that there is, indeed, a remarkable crosstalk contamination in SNPP VIIRS TEB. The crosstalk effect is quantitatively characterized by deriving the crosstalk coefficients from the scheduled lunar observations and the established lunar imagery analysis. Among all SNPP VIIRS TEB, band M14 is shown to have the largest crosstalk contamination from Band M15, while bands M13, M15, M16, and I5 have pronounced crosstalk effect as well. The crosstalk effect is distinctively different for the odd and even detectors within each affected band during to the pattern of the placement of the odd and the even detectors of the band on the focal plane assembly (FPA). The crosstalk coefficients are applied to mitigate the crosstalk effect and the improvements to both the BB calibration and EV retrieval are presented and addressed.

Suomi-NPP visible infrared imaging radiometer suite (VIIRS) calibration uncertainty its effect on trends in the ocean color data record (Conference Presentation).

The NASA Ocean Color calibration team continued to reanalyze and improve on their approach to the on-orbit calibration of the Visible Infrared Imaging Radiometer Suite (VIIRS), aboard the Suomi National Polar-orbiting Partnership (NPP) satellite, now five years into its Earth Observation mission. As the calibration was adjusted for changes in ocean band responsitivity with time, the team also observed the variance and autocorrelation properties of calibration trend fit residuals, which appeared to have a standard deviation within a few tenths of a percent. Autocorrelation was observed to be different between bands at the blue end of the spectrum and bands at the red/NIR end, which are affected by significant changes in responsitivity stemming from mirror contamination. This residual information offered insight into the effect of small calibration biases, which can cause significant trend uncertainties in regional time series of surface reflectance and derived products. This work involves modeling spurious trends that are inherent to the calibration over time and that also arise between reprocessing efforts because of extrapolation of the time-dependent calibration table. Uncertainty in calibration trends was estimated using models of instrument and calibration system trend artifacts and correlated noise models using Monte Carlo techniques. Combined table reprocessing and extrapolation biases are presented for the first time. Calibration trend uncertainty is then propagated through to ocean color remote sensing reflectance and chlorophyll-a concentration time series. The results quantify the smallest trend observable in these oceanic parameters. This quantification furthers our understanding of uncertainty in measuring regional and global biospheric trends in the ocean using VIIRS, and better defines the roles of records in climate research.

MTG-IRS: from raw measurements to calibrated radiances.

The Meteosat Third Generation (MTG) series of future European geostationary meteorological satellites consists of two types of satellites, the imaging satellites (MTG-I) and the sounding satellites (MTG-S). The Infrared Sounder (IRS) is one of the two instruments hosted on board the MTG-S satellites. The scope of the IRS mission is to provide the user community with information on time evolution of humidity and temperature distribution, as function of latitude, longitude and altitude. Regarding time and space sampling, the entire Earth disk will be covered, with particular focus on Europe, which will be revisited every 30 minutes. This paper presents a synthetic overview of the mission and the instrument, and will go through the level 1 processing chain which takes instrument raw data to obtain spectrally and radiometrically calibrated and geolocalised radiances, called level 1b products. A discussion will be presented around the radiances uniformisation in space, spectral range and time and its impact for the users community.

Validation of VIIRS with CrIS by taking into account the sub-pixel cloudiness and viewing geometry (Conference Presentation).

The Cross-track Infrared Sounder (CrIS) onboard Suomi NPP (SNPP) and JPSS series has high radiometric accuracy, which can be used for validating some infrared bands of Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the same platform. The collocated CrIS and VIIRS sensor data record (SDR) along with the VIIRS cloud mask product from 19 to 21 September 2016 (during a period of blackbody warm-up cool-down, or WUCD) are used for inter-comparisons. This study addresses the questions on how the sub-pixel cloud presence and the local zenith angle impact the radiometric differences between CrIS and VIIRS. Both VIIRS brightness temperature (BT) bias and standard deviation for I5, M13, M15 and M15 whose spectral response functions (SRFs) have the full coverages over the CrIS spectral regions, are analyzed over the clear and cloudy skies, respectively. Results show good agreement between VIIRS and CrIS, cloud presence has substantial impact on STD, and also impact on BIAS, local zenith angle has also substantial impact on STD, but impact on bias is small. Both bias and STD are large in DCC (deep convective cloud) areas. The study clearly shows the VIIRS scene temperature bias during WUCD, as well as the bias removal after reprocessing the M15 and M16 with the improved calibration bias correction algorithm. The methodology can be applied to monitor and validate the imager with advanced infrared (IR) sounder onboard the same platform, such as CrIS for VIIRS (SNPP, JPSS), IASI for AVHRR (Metop), and GIIRS for AGRI (FengYun-4).

AIRS visible light channels: Lessons from 15 years of using internal calibration sources, vicarious calibration, and the use of deep convective clouds (Conference Presentation).

The Atmospheric Infrared Sounder (AIRS) on the EOS Aqua Spacecraft was launched on May 4, 2002 and is currently fully operational. AIRS, in addition to the infrared system comprised of 2378 channels with wavelengths ranging from 3.7-15.4 um, has 4 Visible/Near-Infrared channels and an on-board calibration source utilizing 3 independent lamps to characterize the change in the visible response over time. One of the key measurements related to climate change is the measurement of the Reflected Short-Wave Solar radiation (RSW). The AIRS visible light channels can be used to accurately measure the stability of the RSW. We describe our experience from 15 years of AIRS data with using internal calibration lamps, vicarious calibration, MODIS cross-calibration, and Deep Convective Clouds (DCCs) for the calibration and stabilization of the AIRS visible light data. The result is the DCC stabilized anomaly trend of the RSW measured with AIRS.

Imaging gratings: Technology and applications for spectrometers (Conference Presentation).

For imaging spectrometers beside the polarization sensitivity and efficiency the imaging quality of the diffraction grating is essential. Low aberration imaging quality of the grating is required not to limit the overall imaging quality of the instrument. The wavefront aberration of an optical grating is a combination of the substrate wavefront and the grating wavefront. During the manufacturing process of the grating substrate different processes can be applied in order to minimize the wavefront aberrations. The imaging performance of the grating is also optimized due to the recording setup of the holography and a special technique to apply blazed profiles also in photoresist of curved substrates. This technology of holographically manufactured gratings is used for transmission and reflection gratings on different types of substrates like prisms, convex and concave spherical and aspherical surface shapes, free-form elements. All the manufactured gratings are monolithic and can be coated with high reflection and anti-reflection coatings. Prism substrates were used to manufacture monolithic GRISM elements for the UV to IR spectral range preferably working in transmission. Besides of transmission gratings, numerous spectrometer setups (e.g. Offner, Rowland circle, Czerny-Turner system layout) working on the optical design principles of reflection gratings. The present approach can be applied to manufacture high quality reflection gratings for the EUV to the IR. In this paper we report our latest results on manufacturing lowest wavefront aberration gratings based on holographic processes in order to enable at least diffraction limited complex spectrometric setups over certain wavelength ranges. Beside the results of low aberration gratings the latest achievements on improving efficiency together with less polarization sensitivity and multi-band performance of diffractive gratings will be shown.

Compact, on-demand broad spectral range (visible to long wave infrared) calibrator (Conference Presentation).

First, the emission wavelengths from visible to short-wave infrared are generated by Light Emitting Diodes (LEDs) and phosphors which spectrally down convert the higher energy photons from the LED to a lower energy photon distribution. This process is analogous to the commercial lighting industry where blue LEDs are down converted into a distribution that resembles variations of white light. Second, several formats of carbon materials have been combined together into a multi-layer structure so that a highly uniform temperature interface feeds a high emissivity surface of vertically aligned carbon nanotubes. Finally, both of these technologies give rise to a thin profile, layered structure which can be easily mounted on a paddle for movement in and out of the optical path.

Demonstrating Technologies for Hyperspectral Infrared Remote Sensing from Space on a CubeSat (Conference Presentation).

CubeSats offer a low cost platform for remote sensing and in-situ measurements in space. Not only is the cost of the spacecraft low, but also the cost of the launch since typically CubeSats are secondary payloads to the primary satellite being launched. Despite the low available volume, mass and power and a typically less than ideal orbit, the platform can be ideal for demonstrating technology and even achieving certain science quality measurements. In this talk we discuss the CubeSat Infrared Atmospheric Sounder (CIRAS) a new project at NASA JPL designed to demonstrate key technologies for hyperspectral infrared measurements of atmospheric temperature and water vapor from space.