Dr. Kevin A. Twedt Profile

Dr. Kevin A. Twedt

at Science Systems and Applications Inc

Publications (50)

SPIE Journal Paper | 15 April 2024

SNPP VIIRS solar vector orientation knowledge error revealed by solar diffuser stability monitor sun views

Ning Lei, Xiaoxiong Xiong, Sherry Li, Kevin Twedt

JARS, Vol. 18, Issue 02, 027502, (April 2024) https://doi.org/10.1117/12.10.1117/1.JRS.18.027502

KEYWORDS: Sun, Sensors, Displays, Transmittance, Calibration, Satellites, Data transmission, Interpolation, Radiometric calibration, Sunlight

Read Abstract +

Proceedings Article | 19 October 2023 Presentation + Paper

An overview of NOAA-21 VIIRS early on-orbit calibration and performance

Xiaoxiong Xiong, Amit Angal, Junqiang Sun, Ning Lei, Kevin Twedt, Hongda Chen, Kwofu Chiang

Proceedings Volume 12729, 1272916 (2023) https://doi.org/10.1117/12.2680636

KEYWORDS: Calibration, Equipment, Stray light, Signal to noise ratio, Displays, Data transmission, Space operations, Short wave infrared radiation, Sensors, Satellites

Read Abstract +

Proceedings Article | 6 October 2023 Presentation

On-orbit characterization of the VIIRS solar diffuser and attenuation screens for NOAA-21 using yaw measurements

Junqiang Sun, Xiaoxiong Xiong, Ning Lei, Kevin Twedt, Sherry Li

Proceedings Volume 12685, 1268510 (2023) https://doi.org/10.1117/12.2676866

KEYWORDS: Displays, Diffusers, Attenuation, Satellites, Calibration, Visible radiation, Vignetting, Telescopes, Satellite imaging, Reflector telescopes

Read Abstract +

Proceedings Article | 4 October 2023 Presentation + Paper

Early mission performance of NOAA-21 VIIRS reflective solar bands

Ning Lei, Xiaoxiong Xiong, Kevin Twedt, Amit Angal, Sherry Li, Junqiang Sun

Proceedings Volume 12685, 126850Y (2023) https://doi.org/10.1117/12.2676014

KEYWORDS: Bidirectional reflectance transmission function, Short wave infrared radiation, Signal to noise ratio, Sun, Radiometric calibration, Equipment, Displays, Telescopes, Diffusers, Satellites

Read Abstract +

Proceedings Article | 4 October 2023 Presentation + Paper

Impact of satellite orbit drift on MODIS Earth scene observations used in calibration of the reflective solar bands

Kevin Twedt, Xiaoxiong Xiong, Xu Geng, Truman Wilson, Qiaozhen Mu

Proceedings Volume 12685, 126850O (2023) https://doi.org/10.1117/12.2676873

KEYWORDS: Calibration, MODIS, Reflectivity, Data modeling, Satellites, Sensors, Algorithm development

Read Abstract +

Proceedings Article | 4 October 2023 Paper

Using scattered light from nadir port to aid the Terra and Aqua MODIS reflective solar band calibration

Amit Angal, Xiaoxiong Xiong, Kevin Twedt, Junqiang Sun

Proceedings Volume 12685, 126851D (2023) https://doi.org/10.1117/12.2676999

KEYWORDS: MODIS, Calibration, Light scattering, Mirrors, Equipment, Scattered light, Reflectivity, Light sources and illumination, Displays, Diffusers

Read Abstract +

SPIE Journal Paper | 3 August 2023

Aqua MODIS: 20 years of on-orbit calibration and performance

Xiaoxiong Xiong, Amit Angal, Tiejun Chang, Emily Aldoretta, Xu Geng, Daniel Link, Junqiang Sun, Kevin Twedt, Aisheng Wu

JARS, Vol. 17, Issue 03, 037501, (August 2023) https://doi.org/10.1117/12.10.1117/1.JRS.17.037501

KEYWORDS: MODIS, Calibration, Crosstalk, Space operations, Equipment, Long wavelength infrared, Signal to noise ratio, Reflectivity, Mirrors, Sensors

Read Abstract +

Proceedings Article | 28 October 2022 Presentation

Twenty years of Aqua MODIS on-orbit calibration, performance, and improvements

Xiaoxiong Xiong, Amit Angal, Tiejun Chang, Emily Aldoretta, Xu Geng, Daniel Link, Junqiang Sun, Kevin Twedt, Aisheng Wu

Proceedings Volume PC12264, PC122640B (2022) https://doi.org/10.1117/12.2635957

KEYWORDS: Calibration, MODIS, Sensors, Sensor calibration, Visible radiation, Remote sensing, Reflectivity, Long wavelength infrared, Infrared radiation, Environmental sensing

Read Abstract +

Proceedings Article | 30 September 2022 Presentation + Paper

MODIS solar diffuser calibration strategies for the post orbital drift era

Gal Sarid, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 12232, 122320D (2022) https://doi.org/10.1117/12.2633379

KEYWORDS: Calibration, Sensors, MODIS, Space operations, Reflectivity, Sun, Signal detection, Diffusers, Short wave infrared radiation, Data modeling

Read Abstract +

Proceedings Article | 30 September 2022 Presentation + Paper

Calibration of NOAA-20 VIIRS reflective solar bands with combined solar diffuser and lunar data for NASA Collection 2 L1B

Kevin Twedt, Tiejun Chang, Amit Angal, Ning Lei, Junqiang Sun, Xiaoxiong Xiong

Proceedings Volume 12232, 122320R (2022) https://doi.org/10.1117/12.2631700

KEYWORDS: Calibration, Sensors, Short wave infrared radiation, Diffusers, Sun, Algorithm development, Bidirectional reflectance transmission function, Satellites

Read Abstract +

Proceedings Article | 30 September 2022 Presentation + Paper

Detector linearity assessment of MODIS reflective solar bands using on-board calibrators

Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 12232, 122320G (2022) https://doi.org/10.1117/12.2632458

KEYWORDS: Calibration, MODIS, Lamps, Sensors, Reflectivity, Transmittance, Diffusers

Read Abstract +

SPIE Journal Paper | 1 July 2022

Terra and Aqua MODIS collection 7 level 1B algorithm

Amit Angal, Xiaoxiong Xiong, Tiejun Chang, Kevin Twedt, Xu Geng, Aisheng Wu, Emily Aldoretta

JARS, Vol. 16, Issue 03, 037502, (July 2022) https://doi.org/10.1117/12.10.1117/1.JRS.16.037502

KEYWORDS: MODIS, Calibration, Sensors, Reflectivity, Short wave infrared radiation, Long wavelength infrared, Detection and tracking algorithms, Polarization, Mirrors, Algorithm development

Read Abstract +

SPIE Journal Paper | 15 June 2022

Characterization of the on-orbit response versus scan angle for Terra MODIS SWIR bands in Collection 7

Qiaozhen Mu, Xiaoxiong Xiong, Kevin Twedt, Amit Angal, Xu Geng

JARS, Vol. 16, Issue 02, 024520, (June 2022) https://doi.org/10.1117/12.10.1117/1.JRS.16.024520

KEYWORDS: Short wave infrared radiation, Reflectivity, MODIS, Calibration, Photonic integrated circuits, Sensors, Mirrors, Infrared radiation, Bidirectional reflectance transmission function, Absorption

Read Abstract +

Proceedings Article | 12 September 2021 Presentation + Paper

MODIS reflective solar bands calibration improvements for Collection 7

Kevin Twedt, Emily Aldoretta, Amit Angal, Hongda Chen, Xu Geng, Yonghong Li, Qiaozhen Mu, Kevin Vermeesch, Xiaoxiong Xiong

Proceedings Volume 11858, 118580S (2021) https://doi.org/10.1117/12.2597551

KEYWORDS: Calibration, Reflectivity, MODIS, Sensors, Short wave infrared radiation, Mirrors, Polarization, Image quality, Remote sensing

Read Abstract +

Proceedings Article | 12 September 2021 Poster + Paper

Impact of the screen configurations on the estimated Terra MODIS SD degradation

Sarah Henderson, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 11858, 118581C (2021) https://doi.org/10.1117/12.2597322

KEYWORDS: MODIS, Calibration, Sensors, Reflectivity, Mirrors, Diffusers, Data modeling, Sun, Solar radiation, Signal attenuation

Read Abstract +

Proceedings Article | 12 September 2021 Presentation + Paper

High energy particle excitations as a measure of electronic crosstalk in MODIS and VIIRS VIS/NIR bands

Kevin Twedt, Truman Wilson, Xiaoxiong Xiong

Proceedings Volume 11858, 118580T (2021) https://doi.org/10.1117/12.2597316

KEYWORDS: Solar radiation, Sensors, MODIS, Particles, Signal detection, Analog electronics, Near infrared, Calibration, Silicon, Infrared sensors

Read Abstract +

Proceedings Article | 1 August 2021 Presentation + Paper

MODIS reflective solar band calibration improvements using pseudo-invariant desert targets

H. Chen, K. Twedt, K. Vermeesch, E. Aldoretta, A. Angal, X. Xiong

Proceedings Volume 11829, 118290Z (2021) https://doi.org/10.1117/12.2593364

KEYWORDS: Calibration, MODIS, Reflectivity, Sensors, Polarization, Satellites, Data processing, Bidirectional reflectance transmission function

Read Abstract +

To provide the best science data quality, an accurate characterization of the response versus scan angle (RVS) function is critical for the MODIS reflective solar bands (RSB) on-orbit calibration. In every MODIS operational scan, the Earth’s surface, referred to here as Earth view (EV), the space view (SV) port, and the onboard calibrators are viewed via a twosided scan mirror. The RVS is defined as the sensor’s relative response as a function the angle of incidence (AOI) to the scan mirror. Many different approaches have been developed to derive the time-dependent RVS and its look-up table (LUT) applied to MODIS Level 1B (L1B) products since calibration Collection 4. For most MODIS RSB, the on-board calibrators can reasonably track the RVS change with time. In practice, their RVS is derived using data from on-board calibrators and the EV mirror side ratio (for mirror side 2). For Terra bands 1-4, 8-10 and Aqua bands 1-4, 8-9, an enhancement has been employed in Collections 6 and 6.1 (C6/C6.1) by using Earth scene response trending from pseudoinvariant desert sites in addition to the onboard calibrators. The current C6/C6/1 RVS algorithm is focused on fitting the EV data at each AOI over time and then deriving the relative change at different AOI. The EV response trending is currently fitted with multiple segments over time. Alternatively, the EV responses can be fit first as a function of AOI before fitting temporally in order to reduce the dependence on the stability of the desert site. These pre-treatment methods on the EV data provide improvement in the derived calibration coefficients. However, evidence of insufficient calibration is still observed in the MODIS L1B reflectance data, especially in the form of differences between the mirror sides. In this paper, we review the current methodologies that utilize the EV response trends from the pseudo-invariant Libyan desert targets to supplement the gain derived from the onboard calibrators. An improvement is then proposed and investigated such that a sliding window average (SWA) is used to pre-process the raw EV data. The SWA parameters are carefully selected using trade-off studies to accurately track the Earth scene response trending in multiple cases to overcome the reflectance differences between two mirror sides. Calibration results show improvements for both Aqua and Terra MODIS RSB L1B data products. This new adjustment has been included in the recently delivered Collection 7 LUT that will be evident in the L1B products expected to be released in late 2021.

Proceedings Article | 12 April 2021 Presentation + Paper

Terra MODIS sees solar eclipses: analysis of reflective solar band response at multiple radiance levels

Gal Sarid, Kevin Twedt, Xiaoxiong (Jack) Xiong

Proceedings Volume 11727, 117270I (2021) https://doi.org/10.1117/12.2586219

KEYWORDS: Reflectivity, MODIS, Calibration, Signal processing, Sensors, Signal detection, Signal attenuation, Satellites, Satellite imaging, Mirrors

Read Abstract +

SPIE Journal Paper | 6 November 2020

Improvements of on-orbit characterization of Terra MODIS short-wave infrared spectral bands out-of-band responses

Xiaoxiong Xiong, Amit Angal, Yonghong Li, Kevin Twedt

JARS, Vol. 14, Issue 04, 047503, (November 2020) https://doi.org/10.1117/12.10.1117/1.JRS.14.047503

KEYWORDS: MODIS, Short wave infrared radiation, Sensors, Calibration, Long wavelength infrared, Photovoltaics, Reflectivity, Infrared radiation, Mirrors, Mid-IR

Read Abstract +

The short-wave infrared (SWIR) bands (5 to 7, 26) of Terra Moderate Resolution Imaging Spectroradiometer (MODIS), which are colocated with the midwave infrared bands (20 to 25) on the short- and mid-wave infrared focal plane assembly, have a known issue related to 5.3-μm out-of-band (OOB) thermal leak and electronic crosstalk that was identified prelaunch. As a result, a crosstalk correction algorithm was designed and implemented in the MODIS level 1B (L1B) calibration. Shortly after the Terra launch, extensive efforts were undertaken to help characterize and mitigate the impact due to the OOB response and crosstalk on the SWIR on-orbit calibration and, consequently, the associated L1B data products. In addition, special night-time-day-mode operations have been regularly scheduled to derive the crosstalk correction coefficients. Since MODIS does not have a spectral band centered at 5.3 μm, its band 28 (7.325 μm) was chosen as the surrogate sending band to simulate the OOB radiances at 5.3 μm. This was largely based on the measurements from the MODIS Airborne Simulator spectrometer field campaigns in the early months after the Terra launch. In the case of Aqua MODIS, the magnitude of the SWIR crosstalk was much smaller and band 25 (4.52 μm) was found to be more effective as the sending band for the crosstalk correction. In recent years, the Terra MODIS photovoltaic (PV) long-wave infrared (LWIR) bands (27 to 30) electronic crosstalk has increased considerably, especially after the spacecraft safe-mode event occurred in February 2016. This accentuated degradation in the PV LWIR performance has also impacted the performance of the SWIR crosstalk correction and thus its calibration and data quality. We examine the use of band 25 as the sending band for the Terra MODIS SWIR crosstalk correction and compare its performance with that based on band 28 as the sending band. Results indicate an improvement of on-orbit gain stability for the SWIR calibration and reduced detector to detector and subframe to subframe striping in the calibrated L1B imagery, especially during the period when the PV LWIR electronic crosstalk has become more severe. This approach has been implemented in the forward production of Terra MODIS Collection 6 and Collection 6.1, starting from July 2019, and is planned to be used for the future reprocessing of MODIS L1B and to help improve the mission-long reflectance calibration and trending stability of the SWIR bands.

SPIE Journal Paper | 27 October 2020 Open Access

Terra MODIS: 20 years of on-orbit calibration and Performance (Erratum)

Xiaoxiong Xiong, Emily Aldoretta, Amit Angal, Tiejun Chang, Xu Geng, Daniel Link, Vincent Salomonson, Kevin Twedt, Aisheng Wu

JARS, Vol. 14, Issue 04, 049902, (October 2020) https://doi.org/10.1117/12.10.1117/1.JRS.14.049902

KEYWORDS: MODIS, Calibration, Remote sensing

Read Abstract +

DOWNLOAD PAPER

SPIE Journal Paper | 16 October 2020

SNPP VIIRS RSB on-orbit radiometric calibration algorithms Version 2.0 and the performances, part 1: the algorithms

Ning Lei, Xiaoxiong Xiong, Zhipeng Wang, Sherry Li, Kevin Twedt

JARS, Vol. 14, Issue 04, 047501, (October 2020) https://doi.org/10.1117/12.10.1117/1.JRS.14.047501

KEYWORDS: Bidirectional reflectance transmission function, Sensors, Calibration, Sun, Satellites, Transmittance, Detection and tracking algorithms, Reflectivity, Solids, Short wave infrared radiation

Read Abstract +

SPIE Journal Paper | 16 October 2020

SNPP VIIRS RSB on-orbit radiometric calibration algorithms Version 2.0 and the performances, part 2: the performances

Ning Lei, Xiaoxiong Xiong, Zhipeng Wang, Sherry Li, Kevin Twedt

JARS, Vol. 14, Issue 04, 047502, (October 2020) https://doi.org/10.1117/12.10.1117/1.JRS.14.047502

KEYWORDS: Reflectivity, Sensors, Calibration, Signal to noise ratio, MODIS, Bidirectional reflectance transmission function, Satellites, Detection and tracking algorithms, Short wave infrared radiation, Transmittance

Read Abstract +

Proceedings Article | 6 October 2020 Presentation + Paper

Eighteen years of Aqua MODIS on-orbit operation, calibration, and performance

X. Xiong, E. Aldoretta, A. Angal, T. Chang, X. Geng, D. Link, J. Sun, K. Twedt, A. Wu

Proceedings Volume 11530, 1153013 (2020) https://doi.org/10.1117/12.2574995

KEYWORDS: Calibration, MODIS, Sensors, Earth's atmosphere, Atmospheric sciences, Remote sensing system design, Reflectivity, Remote sensing, Environmental sensing, Climatology

Read Abstract +

Proceedings Article | 20 September 2020 Presentation + Paper

MODIS detector differences using deep convective clouds and desert targets

Qiaozhen Mu, Amit Angal, Kevin Twedt, Aisheng Wu, Xiaoxiong Xiong

Proceedings Volume 11530, 115301A (2020) https://doi.org/10.1117/12.2571977

KEYWORDS: MODIS, Sensors, Reflectivity, Calibration, Satellite communications, Satellites, Earth's atmosphere, Clouds, Target detection, Short wave infrared radiation

Read Abstract +

Proceedings Article | 20 September 2020 Presentation + Paper

Analysis of the on-orbit response-versus-scan-angle for the MODIS SWIR bands derived from lunar observations

Truman Wilson, Emily Aldoretta, Amit Angal, Xu Geng, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 11530, 115301E (2020) https://doi.org/10.1117/12.2572877

KEYWORDS: MODIS, Short wave infrared radiation, Calibration, Sensors, Contamination, Mirrors, Reflectivity, Photonic integrated circuits, Electronic components

Read Abstract +

Proceedings Article | 20 August 2020 Poster + Paper

The MODIS RSB calibration and look-up table delivery process for collections 6 and 6.1

Emily Aldoretta, Amit Angal, Kevin Twedt, Hongda Chen, Yonghong Li, Daniel Link, Qiaozhen Mu, Kevin Vermeesch, Xiaoxiong Xiong

Proceedings Volume 11501, 115011Q (2020) https://doi.org/10.1117/12.2570785

KEYWORDS: MODIS, Calibration, Sensors, Reflectivity, Mirrors

Read Abstract +

Proceedings Article | 20 August 2020 Presentation + Paper

N20 VIIRS RSB calibration algorithms and results: collection 2.0

Ning Lei, Kevin Twedt, Amit Angal, Sherry Li, Tiejun Chang, Xu Geng, Xiaoxiong Xiong

Proceedings Volume 11501, 1150114 (2020) https://doi.org/10.1117/12.2567775

KEYWORDS: Calibration, Sensors, Bidirectional reflectance transmission function, Transmittance, Satellites, Telescopes, Sun, Reflectivity, Mirrors

Read Abstract +

Proceedings Article | 20 August 2020 Poster + Paper

Twenty years of Terra MODIS spatial performance using the spectro-radiometric calibration assembly

Daniel Link, Emily Aldoretta, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 11501, 115011I (2020) https://doi.org/10.1117/12.2568047

KEYWORDS: Spatial analysis, Calibration, MODIS, Sensors, Lamps, Signal detection, Long wavelength infrared, Spectral calibration, Reticles

Read Abstract +

Proceedings Article | 20 August 2020 Presentation + Paper

Twenty years of Terra MODIS spectral performance using the spectro-radiometric calibration assembly

Emily Aldoretta, Daniel Link, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 11501, 115010D (2020) https://doi.org/10.1117/12.2570782

KEYWORDS: MODIS, Lamps, Calibration, Spectral calibration, Sensors, Reflectivity, Near infrared, Monochromators

Read Abstract +

SPIE Journal Paper | 8 August 2020

Terra MODIS: 20 years of on-orbit calibration and performance

Xiaoxiong Xiong, Emily Aldoretta, Amit Angal, Tiejun Chang, Xu Geng, Daniel Link, Vincent Salomonson, Kevin Twedt, Aisheng Wu

JARS, Vol. 14, Issue 03, 037501, (August 2020) https://doi.org/10.1117/12.10.1117/1.JRS.14.037501

KEYWORDS: Equipment, Crosstalk, Short wave infrared radiation, Calibration, MODIS, Sensors, Long wavelength infrared, Staring arrays, Signal to noise ratio, Algorithm development

Read Abstract +

Since its launch in December 1999, Terra Moderate Resolution Imaging Spectroradiometer (MODIS) has successfully operated for more than 20 years, with its observations generating a broad range of science data products that have greatly enabled the remote sensing community and users worldwide in their studies of many key geophysical parameters of the Earth’s systems. MODIS collects data in 36 spectral bands, covering wavelengths from 0.41 to 14.4 μm, which are calibrated by a set of onboard calibrators (OBCs). Also contributing to the sensor’s mission-long on-orbit calibration and characterization are near-monthly scheduled lunar observations and multiple time series of the sensor’s responses over select ground targets at a variety of scan angles. To a large extent, the quality of MODIS data products relies strongly on the dedicated efforts to operate and calibrate the instrument, to derive and update calibration parameters, and to develop and implement new calibration strategies and algorithms in response to on-orbit changes of the sensor’s characteristics and its OBC functions. We provide an overview of the Terra MODIS on-orbit operation and calibration activities over the last 20 years, including changes made to extend and preserve the instrument and OBC functions and their operation strategies. It also illustrates the sensor’s on-orbit performance with results derived from its OBC, lunar observations, and select ground targets and discusses major changes in sensor characteristics and corrections applied to the L1B algorithms as well as calibration lookup table updates. To date, the Terra MODIS instrument and its OBCs continue to operate and function normally. Except for those identified prelaunch, most spectral bands and detectors continue to meet their specified calibration requirements. Also discussed in our paper are lessons learned from Terra MODIS operation and calibration, as well as future efforts to further extend and maintain the quality of its long-term data records.

SPIE Journal Paper | 23 June 2020

Effects of out-of-band and time-varying relative spectral response on the calibration of MODIS reflective solar bands

Kevin Twedt, Amit Angal, Xiaoxiong Xiong

JARS, Vol. 14, Issue 02, 024523, (June 2020) https://doi.org/10.1117/12.10.1117/1.JRS.14.024523

KEYWORDS: Calibration, MODIS, Mirrors, Reflectivity, Sensors, Sun, Clouds, Spectral calibration, Ocean optics, Near infrared

Read Abstract +

Proceedings Article | 10 October 2019 Presentation + Paper

Using solar eclipse events to validate VIIRS reflective solar band calibration at multiple radiance levels

Kevin Twedt, Ning Lei, Xiaoxiong Xiong

Proceedings Volume 11151, 111511M (2019) https://doi.org/10.1117/12.2532855

KEYWORDS: Calibration, Sun, Sensors, Data modeling, Satellites, Short wave infrared radiation, Reflectivity, Diffusers, Signal attenuation, Remote sensing

Read Abstract +

Proceedings Article | 10 October 2019 Paper

On-orbit tracking of sub-sample gain differences in SNPP and NOAA-20 VIIRS imagery bands

Kevin Twedt, Ning Lei, Xiaoxiong Xiong

Proceedings Volume 11151, 111512B (2019) https://doi.org/10.1117/12.2533125

KEYWORDS: Sensors, Calibration, Spatial resolution, Image resolution, Satellites, Reflectivity, Diffusers

Read Abstract +

Proceedings Article | 10 October 2019 Presentation + Paper

NOAA-20 VIIRS solar diffuser BRDF on-orbit change factor for wavelengths longer than 1 micron

Ning Lei, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 11151, 111511L (2019) https://doi.org/10.1117/12.2533478

KEYWORDS: Bidirectional reflectance transmission function, Diffusers, Short wave infrared radiation, Infrared imaging, Satellites, Visible radiation, Radiometry, Satellite imaging, Infrared sensors, Sensors

Read Abstract +

Proceedings Article | 10 October 2019 Paper

Improvements in the on-orbit response versus scan-angle characterization for the MODIS ocean color bands

Xu Geng, Amit Angal, Yonghong Li, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 11151, 1115124 (2019) https://doi.org/10.1117/12.2532081

KEYWORDS: MODIS, Calibration, Reflectivity, Mirrors, Sensors, Atmospheric corrections, Photonic integrated circuits, Clouds, Diffusers, Image resolution

Read Abstract +

Proceedings Article | 9 September 2019 Presentation + Paper

Terra MODIS: 20 years of on-orbit calibration and performance

Xiaoxiong Xiong, Emily Aldoretta, Amit Angal, Tiejun Chang, Xu Geng, Dan Link, Vincent Salomonson, Kevin Twedt, Aisheng Wu

Proceedings Volume 11127, 1112714 (2019) https://doi.org/10.1117/12.2531933

KEYWORDS: Calibration, MODIS, Sensors, Diffusers, Earth's atmosphere, Visible radiation, Long wavelength infrared, Infrared radiation, Reflectivity, Black bodies

Read Abstract +

Proceedings Article | 9 September 2019 Paper

Comparison of MODIS solar diffuser stability monitor calibration results for different operational configurations

Kevin Twedt, Amit Angal, Hongda Chen, Xiaoxiong Xiong

Proceedings Volume 11127, 1112728 (2019) https://doi.org/10.1117/12.2528444

KEYWORDS: Calibration, MODIS, Sensors, Sun, Reflectivity, Diffusers, Transmittance

Read Abstract +

SPIE Journal Paper | 29 May 2019

Stray-light correction and prediction for Suomi National Polar-orbiting Partnership visible infrared imaging radiometer suite day-night band

Hongda Chen, Xiaoxiong Xiong, Xu Geng, Kevin Twedt

JARS, Vol. 13, Issue 02, 024521, (May 2019) https://doi.org/10.1117/12.10.1117/1.JRS.13.024521

KEYWORDS: Stray light, Contamination, Sensors, Visible radiation, Infrared imaging, Radiometry, Space operations, Data fusion, Calibration, Airglow

Read Abstract +

Proceedings Article | 23 October 2018 Paper

Initial radiometric calibration status and performance of NOAA-20 VIIRS reflective solar bands

Ning Lei, Kevin Twedt, Xuexia Chen, Xiaoxiong Xiong

Proceedings Volume 10781, 107810M (2018) https://doi.org/10.1117/12.2324523

KEYWORDS: Sensors, Bidirectional reflectance transmission function, Signal to noise ratio, Sun, Calibration, Satellites, Reflectivity, Transmittance, Short wave infrared radiation, Diffusers

Read Abstract +

Proceedings Article | 11 October 2018 Paper

Performance assessments and comparisons of S-NPP and NOAA-20 (JPSS-1) VIIRS on-orbit calibration

Xiaoxiong Xiong, Amit Angal, James Butler, Hongda Chen, Kwofu Chiang, Ning Lei, Yonghong Li, Kevin Twedt

Proceedings Volume 10785, 1078514 (2018) https://doi.org/10.1117/12.2326866

KEYWORDS: Calibration, Sensors, Signal to noise ratio, Long wavelength infrared, Black bodies, Stray light, Contamination, Bidirectional reflectance transmission function, Near infrared, Satellites

Read Abstract +

Proceedings Article | 7 September 2018 Paper

Methods of Earth-view-based calibration of the response versus scan angle of the MODIS reflective solar bands

Kevin Twedt, Hongda Chen, Xiaoxiong Xiong, Amit Angal, Xu Geng, Aisheng Wu

Proceedings Volume 10764, 107641P (2018) https://doi.org/10.1117/12.2321231

KEYWORDS: Calibration, MODIS, Reflectivity, Bidirectional reflectance transmission function, Sensors, Algorithm development

Read Abstract +

Proceedings Article | 7 September 2018 Paper

On-orbit performance of the Terra and Aqua MODIS solar diffuser stability monitor

Emily Aldoretta, Kevin Twedt, Amit Angal, Hongda Chen, Xiaoxiong Xiong

Proceedings Volume 10764, 107641O (2018) https://doi.org/10.1117/12.2321163

KEYWORDS: Signal to noise ratio, Calibration, MODIS, Sensors, Diffusers, Reflectivity, Signal detection, Interference (communication), Space operations, Sun

Read Abstract +

Proceedings Article | 7 September 2018 Paper

Comparison of the MODIS and VIIRS on-board SD and SDSM performance

Amit Angal, Xiaoxiong Xiong, Ning Lei, Kevin Twedt

Proceedings Volume 10764, 107641V (2018) https://doi.org/10.1117/12.2324477

KEYWORDS: MODIS, Sensors, Calibration, Sun, Reflectivity, Signal attenuation, Space operations, Diffusers, Radiometry, Bidirectional reflectance transmission function

Read Abstract +

Proceedings Article | 7 September 2018 Presentation + Paper

Effects of time-varying relative spectral response on the calibration of MODIS reflective solar bands

Kevin Twedt, Amit Angal, Xiaoxiong Xiong

Proceedings Volume 10764, 1076413 (2018) https://doi.org/10.1117/12.2321255

KEYWORDS: MODIS, Calibration, Reflectivity, Mirrors, Sun, Sensors, Ocean optics, Spectral calibration, Diffusers

Read Abstract +

Proceedings Article | 7 September 2018 Presentation + Paper

Assessment of the on-orbit MODIS SRCA spectral uncertainty

Emily Aldoretta, Daniel Link, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 10764, 1076412 (2018) https://doi.org/10.1117/12.2321149

KEYWORDS: MODIS, Calibration, Reflectivity, Diffraction gratings, Spectral calibration, Diffraction

Read Abstract +

SPIE Journal Paper | 16 July 2018 Open Access

Updates of Moderate Resolution Imaging Spectroradiometer on-orbit calibration uncertainty assessments

Xiaoxiong Xiong, Amit Angal, William L. Barnes, Hongda Chen, Vincent Chiang, Xu Geng, Yonghong Li, Kevin Twedt, Zhipeng Wang, Truman Wilson, Aisheng Wu

JARS, Vol. 12, Issue 03, 034001, (July 2018) https://doi.org/10.1117/12.10.1117/1.JRS.12.034001

KEYWORDS: Calibration, MODIS, Sensors, Spectral calibration, Reflectivity, Mirrors, Short wave infrared radiation, Detection and tracking algorithms, Polarization, Imaging systems

Read Abstract +

DOWNLOAD PAPER

Proceedings Article | 5 September 2017 Paper

Status of the MODIS spatial and spectral characterization and performance after recent SRCA operational changes

Daniel Link, Zhipeng Wang, Kevin Twedt, Xiaoxiong Xiong

Proceedings Volume 10402, 104022G (2017) https://doi.org/10.1117/12.2273053

KEYWORDS: MODIS, Lamps, Calibration, Space operations, Sensors, Spectral calibration, Sensor performance, Satellites

Read Abstract +

Proceedings Article | 5 September 2017 Presentation + Paper

On-orbit noise characterization of SNPP VIIRS reflective solar bands

Kevin Twedt, Ning Lei, Xiaoxiong Xiong

Proceedings Volume 10402, 104021X (2017) https://doi.org/10.1117/12.2274025

KEYWORDS: Reflectivity, Signal to noise ratio, Diffusers, Calibration, Satellites, Interference (communication), Sensor calibration, Visible radiation, Infrared imaging, Radiometry

Read Abstract +