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Parker Garcia
Parker Garcia

Sentinel Lite Key

Remote sensing of nighttime light emissions offers a unique perspective for investigations into some of these human behaviors. The Visible Infrared Imaging Radiometer Suite (VIIRS) instruments aboard the joint NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi NPP) and NOAA-20 satellites provide global daily measurements of nocturnal visible and near-infrared (NIR) light that are suitable for Earth system science and applications studies. VIIRS Day/Night Band (DNB) data are used for estimating population, assessing electrification of remote areas, monitoring disasters and conflict, and understanding biological impacts of increased light pollution.

Sentinel Lite Key

Viewing nighttime lights provides a unique perspective of the planet. Unlike daytime remote sensing, there are multiple sources of nighttime illumination. These sources include moonlight, light directly emitted by a source (e.g., buildings and transport), and light reflected by the ground, also known as surface albedo. Snow, which has a high surface albedo under illuminated conditions, can increase the signal returned to a satellite-borne instrument at 512 miles. On the other hand, natural land surfaces with a low surface albedo, such as water bodies and forest canopies, reflect far less light.

NTL data have a long time series. The U.S. Department of Defense launched the Defense Meteorological Satellite Program (DMSP), a series of sun-synchronous satellites, to collect nighttime light emissions with the Operational Linescan System (OLS) sensor from the early 1970s until 2011. The digital stream of data, however, did not begin until 1992.

In 2011, through a partnership with NOAA and the Department of Defense, NASA launched the Suomi NPP satellite and in 2018 the NOAA-20 satellite. Both satellites carry the VIIRS instrument, which also collects NTL emissions and continues the long-term NTL data record. The VIIRS DNB improves upon the older DMSP OLS with higher spatial and radiometric resolution: VIIRS has a spatial resolution of 375 and 750 meters (depending on the band), daily temporal resolution, and more complete global coverage and higher quality data.

The VIIRS Level 1 DNB product has been calibrated, but stray light and other sources of noise (e.g., lunar illuminance, twilight, clouds, noisy scan-edges, etc.) affect the DNB quality, and warrant additional correction. For example, with moonlight the reflectance of snow cover, smoke, airborne dust, sea ice, and land surface features are visible. Likewise, artificial light sources exhibit large variations when viewed at different satellite viewing geometries. This requires that the data be carefully processed so scientific analyzes and applications are conducted consistently.

Houston, TX, experienced a major winter storm in February 2021, which shattered low-temperature records and knocked out power to 1.4 million customers. Natural gas shortages were already impacting demand, which only intensified as time progressed. Controlled outages and downed power lines left parts of the state in the dark. NASA Black Marble data show the extent of this outage event. The image below is a Black Marble High Definition (HD) product. Black Marble HD is generated through the synergistic use of the daily NASA Black Marble standard product with data from other Earth observing satellites (e.g., Landsat 8, Sentinel-2) and ancillary data sources (e.g., street, building, and other GIS layers).

Research on the consistency of suspended particulate matter (SPM) concentration retrieved from multisource satellite sensors can serve as long-time monitoring of water quality. To explore the influence of the atmospheric correction (AC) algorithm and the retrieval model on the consistency of the SPM concentration values, Landsat 8 Operational Land Imager (OLI) and Sentinel 2 MultiSpectral Imager (MSI) images acquired on the same day are used to compare the remote sensing reflectance (Rrs) SPM retrieval values in two high-turbidity lakes. An SPM retrieval model for Shengjin Lake is established based on field measurements and applied to OLI and MSI images: two SPM concentration products are highly consistent (R2 = 0.93, Root Mean Squared Error (RMSE) = 20.67 mg/L, Mean Absolute Percentage Error (MAPE) = 6.59%), and the desired results are also obtained in Chaohu Lake. Among the four AC algorithms (Management Unit of the North Seas Mathematical Models (MUMM), Atmospheric Correction for OLI'lite'(ACOLITE), Second Simulation of Satellite Signal in the Solar Spectrum (6S), Landsat 8 Surface Reflectance Code & Sen2cor (LaSRC & Sen2cor)), the two Rrs products, as well as the final SPM concentration products retrieved from OLI and MSI images, have the best consistency when using the MUMM algorithm in SeaWIFS Data Analyst System (SeaDAS) software. The consistency of SPM concentration values retrieved from OLI and MSI images using the same model or same form of models is significantly better than that retrieved by applying the optimal models with different forms.

Most sentinels follow a specific dress code, white and black cloth with gold trimmings and geometric accessories, including the crest of the Sentinels. Akshan is mentioned to have broken several dress codes of the order with his preferred choice of garments.

The exterior of the main bunker is a concrete pyramid, with a blast door entrance on the northeast side; four separate ventilation towers also rise to the northeast. Through the entrance is a large room resembling a missile silo featuring a network of catwalks. Descending the catwalk to the left leads to the first control room. On a desk on the room's lower level is the sentinel site blast door override holotape, which will open the blast doors in the facility when loaded in the doors' related terminals. The blast door near the desk opens to reveal a small observation room, where a terminal may be accessed for a pre-War launch report. Continuing down the catwalk, a second similar observation room and terminal are in the control room on the next level down. Finally, a terminal that may be used to abort the launch sequence is on the lowest level. The nearby elevator may be used to return to the catwalk by the entrance on the top level. 041b061a72




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