Increased striping was observed in Suomi-NPP VIIRS DNB nighttime imagery after a flight software update on January 8, 2020. It occurred after an onboard computer reboot, resulting in a sudden change in the HGS dark offset. The sudden change made the HGS DN0 (dark offset) LUT outdated, eventually degrading the nighttime imagery. Analysis of the DNB monthly calibration data collected before and after the flight software update indicated that the sudden change in the HGS dark offset was induced by an unexpected change of the HGS electronic bias after an onboard computer reboot during the flight software update. An algorithm capable of correcting the sudden change while also eliminating star light contamination has been adopted for determining the DN0 LUT since the DNB monthly calibration starting in late January 2020. Nighttime image quality affected by the electronic bias change has been restored after the LUT update.
The operational VIIRS Day/Night Band (DNB) Low Gain Stage (LGS) gain is calibrated by the onboard solar diffuser when it is fully illuminated by the Sun. Such calibration method relies on assumption of the same calibrator view and Earth view responses of the LGS. However, analysis of the NOAA-20 VIIRS DNB prelaunch testing data shows this assumption is not valid for all aggregation modes and detectors, consequently yielding striping in NOAA-20 VIIRS DNB daytime images collected by its LGS. Through applying scaling factors derived from the prelaunch testing data, the operational LGS gain calibration errors are corrected and striping in the reprocessed DNB daytime images is reduced.
The VIIRS Day/Night Band (DNB) sensors onboard NOAA-20 and SNPP satellites, being 50 minutes apart along the same orbit, provide nighttime imagery of clouds, nocturnal lights, aurora etc., and have been used for a variety of studies involving both geophysical and socio-economic activities. DNB stray light has been observed over both the Northern and the Southern Hemisphere. The monthly stray light correction look-up-table has been routinely generated for operational DNB data production. The calibration algorithm of DNB was recently improved to reduce strong striping at the end aggregation zones for both SNPP and NOAA-20. In addition, there were remnant stray light of the magnitude ~1 nW/cm2- sr in the SNPP DNB image over the southern hemisphere resulting from the use of static yearly-recycled stray light correction look-up-tables (twelve sets) generated during 2014 and 2015. To address these issues, the stray light correction algorithm was improved to support operational SNPP DNB calibration since May 2019. For NOAA-20 DNB, to synchronize with the improved DNB calibration algorithm and maintain consistency between DNB stray light correction and calibration algorithm update, monthly DNB stray light correction LUTs have been routinely generated for one additional full year until November 2019. This paper reports the updates that have been performed for SNPP and NOAA- 20 DNB stray light correction and evaluates the improvements in DNB imagery products.
Striping has been observed in nighttime imagery of VIIRS DNB onboard both Suomi-NPP and NOAA-20 satellites. Image analysis indicated that stripes usually come from the detectors with residual nonlinearity at very low radiance levels, whose High Gain Stage gain coefficients are biased due to the errors in the corresponding DNB gain ratios. Such bias is more than 10% for certain aggregation mode and detectors. By processing the VIIRS recommended operating procedure data with the linear regression method, we corrected the nonlinearity induced bias in the DNB gain ratios. Comparison of the original and the reprocessed DNB nighttime images shows that striping is significantly reduced, in particular under moonlight illumination.
With comprehensive analysis of the VIIRS DNB on-board calibrator blackbody (OBCBB) data and Earth View (EV) data, it is shown that the DNB OBCBB data can only track the dark current component of the DNB HGS EV dark offset. The DNB observation of deep space during the spacecraft pitch maneuver was also contaminated by star lights. With these acquired knowledge, we propose an improved algorithm for determining the DNB HGS dark offset that is both free from light contamination and capable of tracking drifts continuously. The new algorithm is expected to improve the DNB radiometric performance at low radiance level.
The atmospheric turbulence effects on the light field at the altitude of the VIIRS from a ground based Lambertian source were investigated. It has been shown theoretically that the radiant intensity follows the Lambert’s law despite of turbulent perturbations. The corresponding average irradiance at the altitude of the VIIRS can be determined via the inverse square law. Light field scintillation was evaluated numerically by the discretized mode representation of the source and the multiple random phase screen simulation method. Our results will contribute to the study of using ground based light source for the validation/calibration of the VIIRS DNB.
Polarized image of underwater light field contains rich information of and the targets strongly affected by the water inherent optical properties. We present a comprehensive analysis of the polarimetric images of a manmade underwater target with known polarization properties acquired by a full Stokes vector imaging camera in underwater environment. The effects of the camera’s parameters such as numerical aperture and orientation are evaluated. With the knowledge acquired in the analysis of such a forward polarimetric imaging process, a method for retrieval of the inherent optical properties of the water and the target polarization is explored.
The recently introduced class of Multi-Gaussian Schell-model [MGSM] beams is investigated via simulations and experiments with regards to its intensity fluctuations on propagation in atmospheric turbulence. The results indicate that the scintillation index of the MGSM beam is reduced for high values of the summation index, in agreement with previous theoretical results.
The analysis of images of several underwater targets that exhibits different polarization properties measured using an underwater camera in various water conditions is presented. The measurements are compared with an imaging model which combines vector radiative transfer simulations by the RayXP program for the propagation of light in the atmosphere-interface-ocean system and the Monte Carlo simulations for the near horizontal imaging in the water. Modeling includes analysis of the vector point spread function (PSF) from the target and the contribution of the veiling light between the target and the camera.
Polarized light fields contain more information than simple irradiance and such capabilities provide an advanced tool for
underwater imaging. We used a Monte Carlo technique to simulate the vector point spread function for a broad range of
water parameters from clear to turbid coastal waters. We also analyzed the impact of light scattered by suspended
particles between the target and the camera on the polarized image together with the light from the target. This
knowledge is expected to contribute to solutions of the inverse problem of the restoration of the target polarization
characteristics from its underwater image.
We introduce the concept of pseudo-Bessel correlated beams and investigate their scintillation properties on
propagation through turbulence. In weak turbulence the scintillation index of pseudo-Bessel correlated beams
is formulated by using the Rytov approximation. The study of scintillation is extended to strong turbulence by
numeric simulations. It is shown that by choosing an appropriate coherence parameter, pseudo-Bessel correlated
beams have lower scintillation than comparable fully coherent beams in both weak and strong turbulence.
The scintillation properties of Airy beam arrays in atmospheric turbulence are investigated. Similar to their
propagation in free space, the average propagation paths of Airy beams are also parabolic in turbulence. By
utilizing this self-bending property, the constituent Airy beamlets propagate through relatively independent
regions of turbulence and fully overlap at the on-axis detector. Through numeric simulations, it is shown that
the scintillation of Airy beam array is significantly reduced compared to a single Airy beam.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.