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The Geostationary Environment Monitoring Spectrometer (GEMS) onboard the Geostationary Korea Multi-Purpose Satellite-2B (GEO-KOMPSAT-2B) satellite observes the hourly volcanic SO2 over Asia. In this study, the various physical characteristics of volcanic plumes have been investigated based on hourly volcanic SO2 measurements. The transport direction, path and speed, and altitude of volcanic SO2 plume emitted from Nishinoshima in Japan, Etna in Italy, and Dukono located in Halmahera, Indonesia were calculated. The SO2 plume from Nishinoshima, Japan, moved westward at a maximum speed of 57 km/h on August 4, 2020. The SO2 plume generated from Etna was observed to move over China using both GEMS and TROPOMI, and moved at an altitude of 11–14 km and a speed of 162–190 km/h. In the case of the SO2 plume from the Dukono volcano flowed into an average of 3.6 Mg of SO2 per hour to the cities of nearby islands. GEMS can be utilized for an improvement in the prediction accuracy of SO2 plume transport using a chemical transport model due to the availability of hourly volcanic SO2 height information. In addition, hourly observations of SO2 concentrations are expected to protect SO2 exposure through rapid forecasting for people in cities around the volcano.

Nitrogen oxides are among the most important pollutants in the troposphere. They are emitted in many anthropogenic activities such as fossil fuel use for energy production and transportation or agricultural burning. At high concentrations, nitrogen oxides are a health hazard. They also are involved in the formation of tropospheric ozone and acid rain.There are many different ways to measure nitrogen oxides in the atmosphere. Satellite observations of NO2 are one of the most powerful as they provide excellent coverage. However, the spatial resolution is limited and in the case of measurements from low-earth satellites, there is only one measurement per day. The latter problem can be overcome by using geostationary satellites, and the Korean GEMS instrument is the first to provide hourly NO2 observations over Asia.In this study, a full year of tropospheric NO2 columns are retrieved from GEMS observations. Different retrieval settings are applied and the results compared with a particular emphasis on the analysis of the diurnal variation of NO2. Sensitivity tests include correction for the polarisation sensitivity of the GEMS instrument, different stratospheric correction schemes, different surface reflectances and different a priori profiles. While all of these parameters affect the retrieved NO2 columns, the pattern of the diurnal variation of the retrieved tropospheric columns appears to be robust, at least over regions with large pollution signals.

Geostationary Environment Monitoring Spectrometer (GEMS), the world's first geostationary environmental senor onboard Geo-Kompsat 2B, was launched in February, 2020 to monitor atmospheric pollutants (such as -> e.g. Aerosol properties, Nitrogen dioxide, Sulphur dioxide, Formaldehyde and Ozone) with high temporal and spatial resolution over ASIA. Environmental Satellite Center (ESC) of National Institute of Environmental Research has distributed these data since March, 2021 after in-orbit test was completed. We performed the accuracy validation of GEMS atmospheric pollutants retrieval algorithm using other environmental satellite (such as TROPOMI, OMPS, etc.) and ground-based measurements (such as Pandora, Max-DOAS, etc.) data through GEMS Map of Air Pollution (GMAP) and Satellite Integrated Joint monitoring of Air Quality (SIJAQ) campaign. We validated the accuracy of GEMS atmospheric-pollutants-retrieval algorithm using the data from other environmental satellites (e.g. TROPOMI, OMPS, etc.) and ground-based measurements data (e.g. Pandora, Max-DOAS, etc.).After that, we improved the accuracy of retrieval algorithm and released GEMS version two data in November last year. In this version two data, we found improvements needed in a priori data, cloud data, and surface reflectance data. In this present study, we introduce the difference and improvements GEMS version two and one data.

The Geostationary Environment Monitoring Satellite (GEMS) retrieves several species of trace gases and aerosol properties. For the aerosol property, retrieval results from the GEMS can be used for the surface air quality analysis and aerosol effect for the airmass factor (AMF) calculation. To provide accurate information on aerosol, in addition, aerosol vertical information is also retrieved from the GEMS defined by the aerosol effective height (AEH). The AEH can help to estimate the AMF for tropospheric trace gases and surface concentration of particulate matter (PM). The aerosol vertical distribution is relatively difficult to retrieve compared to those of clouds, because the optical property of aerosol is various due to the various aerosol types in the atmosphere. For the UV-visible hyperspectral observation, the aerosol vertical distribution can estimate from the absorption bands based on the Oxygen molecules, such as O2-A, O2-B, and O2-O2 absorption. Because of the limitation for the spectral coverage from 300~500 nm, however, GEMS is only available to use O2-O2 absorption bands. For the possibility of the AEH retrieval algorithm from GEMS, Park et al. (2016) investigated the theoretical sensitivity test of the AEH retrieval by solely using the O2-O2 absorption band with considering the aerosol and surface properties. Based on the previous studies, we introduce the operational retrieval algorithm for AEH with the theoretical basement. Also, we showed the performance of the operational AEH algorithm from GEMS based on case studies and the validation study using Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP).

Recent works on using Machine Learning methods for deriving estimates of the NO2 concentration at the Earth's surface from satellite observations exploit measurements taken from low Earth orbits, e.g. from the TROPOMI instrument on the Copernicus Sentinel-5P satellite. However, given geographic location, the time resolution is quite low, with a single measurement per day, which leads to rather small data sets. In order to increase the performance of Machine Learning methods, large data sets would be desirable.Launched in 2019, the Korean Geostationary Environmental Monitoring Spectrometer (GEMS) mission has been the first geostationary satellite mission for observing trace gas concentrations in the Earth's atmosphere over Asia. Geostationary orbits allows for hourly measurements, which leads to a much higher temporal resolution compared to measurements taken from low Earth orbits. Within the next years, two further geostationary missions will follow: NASA‘s TEMPO and ESA‘s Sentinel-4 mission, providing additional data with high temporal resolution over North America and Europe.One of the GEMS level-2 data products is the NO2 tropospheric vertical column density (VCD). In our research project we discuss and develop Deep Learning methods that use not only these NO2 VCDs, but also additional data such as meteorological and geographical data, to derive estimates of the NO2 surface concentration in high spatial as well as high temporal resolution, enabled by the geostationary GEMS measurements mentioned above. The validation of the network‘s prediction is realized by the consideration of in-situ NO2 observations from the air quality network of South Korea.

The Geostationary Environmental Monitoring Spectrometer (GEMS) is a UV–visible spectrometer onboard the GEO-KOMPSAT-2B satellite launched into geostationary orbit in February 2020. To evaluate GEMS NO2 column data, comparison was carried out using NO2 vertical column density (VCD) measured using direct-sunlight observations by the Pandora spectrometer system at four sites in Seosan, South Korea, during November 2020 to January 2021. Correlation coefficients between GEMS and Pandora NO2 data at four sites ranged from 0.35 to 0.48, with root mean square errors (RMSEs) from 4.7 × 1015 molec. cm-2 to 5.5 × 1015 molec. cm-2 for cloud fraction (CF) < 0.7. Higher correlation coefficients of 0.62–0.78 with lower RMSEs from 3.3 × 1015 molec. cm-2 to 4.3 × 1015 molec. cm-2 were found with CF < 0.3, indicating the higher sensitivity of GEMS to atmospheric NO2 in less-cloudy conditions. Overall, GEMS NO2 column data tend to be lower than those of Pandora due to differences in representative spatial coverage, with a large negative bias under high-CF conditions. With correction for horizontal representativeness in Pandora measurement coverage, the correlation coefficients range from 0.69 to 0.81 with RMSEs from 3.2 × 1015 molec. cm-2 to 4.9 × 1015 molec. cm-2 were achieved for CF < 0.3, showing the better correlation with the correction than that without the correction.

Nitrogen dioxide (NO2) is a major air pollutant. Tropospheric NO2 vertical column densities (VCDs) retrieved from sun-synchronous satellite instruments have provided abundant NO2 data for environmental studies, but such data are limited by insufficient temporal sampling (e.g., once a day). The Geostationary Environment Monitoring Spectrometer (GEMS) launched in February 2020 monitors NO2 at an unprecedented high temporal resolution. Here we present a research product for tropospheric NO2 VCDs, referred to as POMINO-GEMS. We develop a hybrid retrieval method combining GEMS and TROPOMI observations as well as GEOS-Chem simulations to generate hourly tropospheric NO2 slant column densities (SCDs). We then derive tropospheric NO2 air mass factors (AMFs) with explicit corrections for the anisotropy of surface reflectance and aerosol optical effects, through pixel-by-pixel radiative transfer calculations. Prerequisite cloud parameters are retrieved with the O2-O2 algorithm by using ancillary parameters consistent with those used in NO2 AMF calculations. Initial retrieval of POMINO-GEMS tropospheric NO2 VCDs for June–August 2021 reveals strong hotspot signals over megacities and distinctive diurnal variations over polluted and clean areas. POMINO-GEMS NO2 VCDs agree well with our POMINO-TROPOMI v1.2.2 product (R = 0.97, and NMB = 3.6 %) over Asia. Comparison with ground-based MAX-DOAS VCD data at nine sites shows a small bias of POMINO-GEMS (NMB = –15.7 %); however, the correlation for diurnal variation varies from -0.66 to 0.90, suggesting location-dependent performance. Surface NO2 concentrations estimated from POMINO-GEMS VCDs are consistent with measurements from the Ministry of Ecology and Environment of China at 855 sites (NMB = –24.1 %, and R = 0.95 for diurnal correlation averaged over all sites). POMINO-GEMS data will be made freely available for users to study the spatiotemporal variations, sources and impacts of NO2.

A Schottky photodiode based on a binary mixture of Ag2Se CQDs and PbS CQDs and the photodiode's spectral responsivity.

The COVID-19 pandemic has caused severe damage to the global tourism industry. However, there is hope that the industry will recover in the near future. This study investigates how the pandemic has affected the peoples’ traveling intention and provide implications for accelerating the recovery of the industry. A PLS-SEM analysis of 382 samples confirms the significant effect of COVID-19 risk perception on travel intention while also highlighting the mediating role of perceived effectiveness of COVID-19 protective measures. The study also concludes that there is a significant difference in the perceived protective measure effectiveness-travel intention relation based on accommodation preference.

Lead selenide (PbSe) was the first semiconductor used for photosensors operating in the mid-wavelength infrared spectral region (3-5 um) and is still the primary choice for low-cost, uncooled photoconductive detector applications. Even through PbSe has been studied for over 70 years, more understandings on its physical mechanism for high photoresponsivity is still emerging. Common methods of fabricating PbSe detectors involve physical/chemical vapor deposition or chemical bath deposition (CBD) techniques, followed by post-deposition sensitization processes including oxygen annealing and iodization. Here, we present a new approach to fabricating photoconductive devices based on PbSe colloidal nanocrystals. This infrared colloidal ink can serve as a critical component to enabling digital additive manufacturing of mid-infrared sensor arrays and simultaneously lower the fabrication cost by removing multiple masking steps required in conventional approaches. We report on the synthesis and fabrication of PbSe nanostructured film and the effects of thermal annealing as well as oxygen and iodide incorporation on the photoconductive properties.

The Geostationary Environment Monitoring Spectrometer (GEMS) onboard the Geostationary Korea Multi-Purpose Satellite-2B (GEO-KOMPSAT-2B) satellite was launched in February 2020 and observes the hourly volcanic SO2 in geostationary orbit. We For the first time show the hourly changes in volcanic SO2 distributions emitted and transported from several volcanoes over Asia. The various physical characteristics of volcanic plumes have been investigated based on hourly volcanic SO2 measurements. We estimated transport direction, path and speed, and altitude of volcanic SO2 plume emitted from Nishinoshima in Japan, Etna in Italy, Taal volcano in the Philippines and Dukono located in Halmahera, Indonesia. Before the eruption, Taal volcanic SO2 plumes, which were found to present within PBL, were transported mostly less than 100 km in various azimuth directions. Gradual increase in SO2 column densities was observed for about two months before a volcanic eruption from Taal. It implies that it might be possible to warn a volcanic eruption in advance which is subject to further investigation. GEMS can be further utilized for an improvement in prediction accuracy of SO2 plume transport using chemical transport model due to the availability of hourly volcanic SO2 height information.

Nitrogen oxides (NOx) play an important role in tropospheric chemistry and are key pollutants in particular in industrialised regions. While some natural emission sources exist such as lightning and bacterial soil activities, anthropogenic emissions dominate, mainly from transport, energy production, heating and industrial sources. To better understand the role of nitrogen oxides in the troposphere and to monitor the effects of measures taken to reduce emissions, continuous and global measurements of NO2 abundances in the troposphere are needed.Passive remote sensing of NO2 from space is possible as it has strong and structured absorption features in the UV and visible part of the solar spectrum. Global measurements of tropospheric NO2 have been achieved from a series of instruments including GOME, SCIAMACHY, GOME2, OMI and TROPOMI. While these data sets provide a wealth of information on NO2, they all are from satellites in sun-synchronous orbits and provide little insight into the diurnal evolution of NO2. This has changed with the launch of the Korean GEMS instrument that is the first to provide hourly NO2 measurements over Asia.In this study, spectra from the GEMS instrument were analysed for tropospheric NO2 using the IUP-Bremen NO2 retrieval code developed as breadboard algorithm for the upcoming European geostationary instrument Sentinel-4. Very good agreement is found between GEMS and concurrent measurements from TROPOMI. Validation using ground based MAX-DOAS measurements in Incheon, Republic of Korea during the GMAP-2021 campaign shows good correlation but a systematic underestimation, similar to what is reported for TROPOMI data. A number of sensitivity studies have been performed to explore the changes of the retrievals when using different stratospheric correction schemes, different a priori NO2 profiles, and different surface reflectivity assumptions. The results will be presented and discussed, in particular in view of their impact on the diurnal variations retrieved for NO2 over different cities in Asia.

Nitrogen dioxide (NO2) is generally emitted from the anthropogenic source such as fossil fuel combustion and natural sources such as lightning, forest fires, and soil emission. These NO2 have adverse effects on human health and are known to affect regional climate as a short lived climate forcer. In addition, it is a precursor of aerosol nitrate and plays a key role the photochemistry of tropospheric Ozone. Up to date, NO2 observation has been possible only once a day using low earth orbit satellite sensors such as GOME, SCIAMACHY, GEMS-2, OMI, OMPS, and TROPOMI. However, hourly NO2 monitoring is expected to provide better understanding of atmospheric chemistries and climate effects related with NOx in regional and global scales. From February, 2020, it is possible, for the first time, to observe the diurnal NO2 variations using Geostationary Environment Monitoring Spectrometer (GEMS). Here, we present first results of diurnal changes in total and tropospheric NO2 columns observed over Asia with high temporal and spatial resolutions using the GEMS operational NO2 algorithm. NIER of Ministry of Environment in South Korea plans to release the GEMS NO2 data in real-time. The GEMS operational NO2 algorithm based on DOAS technique and LUT based NO2 AMF to retrieve the total NO2 columns. We, in addition, retrieve the GEMS tropospheric NO2 columns by subtracting stratospheric NO2 columns from the total NO2 columns. The stratospheric NO2 columns are calculated from scaling stratospheric NO2 from SLIMCAT model using the real GEMS observation data over Pacific ocean. In this present study, we introduce diurnal characteristics at various major cities including, ports, and industrial regions. We also evaluate the performance of the GEMS NO2 retrieval algorithm by comparing GEMS NO2 columns and those observed from ground based Pandora at Seosan in South Korea and MAX-DOAS at Xianghe in China. The comparisons also are made between the total and tropospheric GEMS NO2 data and that of TROPOMI. The validation results show good agreements of GEMS data against those from others.

Background There has been a growing interest in the association between mitochondrial dysfunction and sepsis. However, most studies have focused on mitochondrial structural damage, functional aspects, or the clinical phenotypes in sepsis. The purpose of this study was to evaluate mitochondrial DNA (mtDNA) gene mutations in critically ill pediatric patients with septic shock. Method Thirteen patients with severe sepsis or septic shock admitted to the pediatric intensive care unit (PICU) of a tertiary children's hospital were enrolled in this prospective observational study. Clinical data from electronic medical records were obtained. Whole-blood samples were collected within 24 h of PICU admission to perform PBMC isolation, mtDNA extraction, and mtDNA sequencing using next-generation sequencing. Results mtDNA sequencing revealed mutations in 9 of the 13 patients, presenting 27 point mutations overall, with 15 (55.6%) located in the locus related to adenosine triphosphate production and superoxide metabolism, including electron transport. Conclusion In this pilot study, significant numbers of mtDNA point mutations were detected in critically ill pediatric patients with septic shock. These mutations could provide promising evidence for mitochondrial dysfunction in sepsis and a basis for further large-scale studies. Impact This study is the first to examine mitochondrial DNA mutations in pediatric patients with septic shock using next-generation sequencing. A high frequency of mitochondrial DNA mutations was detected in these patients indicating an association with septic shock. This pilot study may provide a potential explanation for the association between mitochondrial dysfunction and septic shock on a genetic basis.

PurposeDigital stickers are being used frequently due to a rapid increase in the usage of mobile messenger services. Moreover, characters featured on digital stickers are being used as spokes-characters for brand marketing and advertisements. These characters create positive consumer attitude toward the brand and the brand's product or service.Design/methodology/approachBased on 307 surveys collected in Korea, this paper examines the relationship between the dimensions of the characters and the usage intention of an Internet-only banking service.FindingsResults indicate that unlike conventional spokes-characters, the expertise of sticker characters does not have an influence on usage intention. However, all three dimensions of characters are effective in forming a positive brand equity, and this has a mediating role in enhancing usage intention.Originality/valueCurrent research has brought academic attention to characters featured on digital stickers and have verified their significant role. Moreover, in an Internet-only banking context, branding strategy is an effective way to encourage customers to use services. Theoretical implications are addressed, as are implications for managers who are looking for a character that will execute effective marketing campaigns.

To ensure the peaceful use of nuclear energy, nuclear safeguards are applied in member states of the International Atomic Energy Agency the Non-Proliferation Treaty. The two main goals of nuclear safeguards are effectiveness and efficiency. The International Atomic Energy Agency has a great interest in using a containment and surveillance technology to maintain continuity of knowledge. A representative means of a containment and surveillance technology is a sealing system to alert the user to tampering. The existing sealing systems used by the International Atomic Energy Agency are of limited utility for real-time verification purposes. To address this limitation, the present study analyzed the design requirements of a sealing system proposed by various institutions including the International Atomic Energy Agency, the U.S. Nuclear Regulatory Commission, a number of national laboratories, and companies. Then, we identified the appropriate design requirements of this system for real-time verification. The next step is to develop a real-time verification sealing system based on the design requirements identified and discussed herein. Such a system is expected to significantly enhance the efficiency of nuclear safeguards.

At airports and ports, X-ray security scanners based on dual-energy transmission imaging have been operated to prevent importation of contraband articles including weapons, narcotics, and explosives. Security scanners currently operated by the Korea Customs Service use a fixed tube voltage (i.e., 160 kVp); hence, it has a limitation in detecting thinly-coated and/or low-density organic contraband articles. Tube voltage lower than 160 kVp affords an advantage in terms of enhanced contrast for organic materials, albeit at the cost of penetration power, and vice versa. Therefore, a security scanner with variable tube voltage that is adjustable according to the physical/chemical properties of the object to be inspected, has the potential to improve detection probability for contraband articles. In the present study, security scanner design optimization specifically in terms of the X-ray generator and the dual-energy detector was performed by Monte Carlo (MC) simulations. Then, the performance of the designed system was evaluated using a simple phantom to demonstrate the advantages of the variable tube voltage application. Additionally, the standard kits were used for performance evaluation in terms of simple penetration and wire display, which are the two parameters specified in Korean law.

The decrease of the gate voltage swing switching a field effect transistor from on to off state and, consequently, the decrease of the power supply voltage is the key challenge of the transistor design. Gate voltage dependent tunneling has been used to achieve this goal by decreasing the slope of the exponential current decay in the subthreshold regime below 60 mV per decade. We describe a new Carbon Nanotube (CNT) Percolating Thin Film Transistor (PTFT) that should allow achieving a steep subthreshold slope. CNT TFTs use mats of CNTs deposited on a substrate and forming a random percolating network. The conduction contacts between the individual CNTs is determined by tunneling and, therefore, could be strongly affected by external agents, such as gases or biological fluids. The asymmetry of the contacts to each CNT enables the rectification of electromagnetic radiation impacted on the CNT mat changing the drain-to-source conduction, with giant relative changes near the percolation point. Our experimental data show that sub-THz radiation shifts the percolation point at high intensity, when the rectified radiation changes the shape of the potential barrier between the CNT in a proximity contact. The CNT PTFT operates near the percolation point. In this regime, the gate bias shifts the percolation point by (a) depleting the CNTs in the subthreshold regime and (b) changing the shape of the tunneling barrier. This ensures the metal-insulator transition resulting in a sharp decrease of the subthreshold current slope. We present a compact model of the percolated CNT PTFT based on our Unified SPICE/ADS model that shows that this effect could reduce the subthreshold slope of the CNT TFs from 340 meV per decade to about 190 meV per decade. Acknowledgments This work at RPI was supported by the U.S. Army Research Laboratory under the Cooperative Research Agreement (Project Monitor Dr. Meredith Reed) and by the US ONR (Project Monitor Dr. Paul Maki).

We demonstrated a dramatic reduction in the sub-terahertz (sub-THz) transmittance and enhancement in the conductance of the carbon nanotube (CNT) mats at high radiation intensities near the percolation threshold, i.e. at the CNT concentrations where the mat conductivity as a function of the CNT concentration sharply increases. The CNT mat conductivity near the percolation point is determined by the electron (or hole for p-type CNTs) tunneling between the adjacent nanotubes. The symmetry of CNT contacts is broken by the differences in the positions and the sizes and types of the contacting CNTs enabling the rectification of the THz or sub-THz radiation impinging on the CNT mats. As the consequence of such rectification, the tunneling barrier shape changes to a more triangular share enhance the CNT mat AC conductivity and decrease transmission. One application of this effect is films preventing damage to sensitive THz and sub-THz detectors (such as Schottky diodes or TeraFETs) by limiting the maximum power impinging on the detectors. Since the shape of the tunneling barriers is strongly affected by ambience and/or substrate monitoring limiting CNT transmission near the percolation point transmission as function of intensity, temperature, and frequency could be used for humidity, temperature, gas exposure, strain, and multiple sensors of external stimuli. The nanoscale of CNT contacts and gaps enables high speed THz responses.

Background Novel three-layered (TL) tablet systems were compared with both monolithic matrix (MM) formulations and a commercial immediate-release (IR) capsule to develop once-a-day (OAD) pregabalin tablets. Methods The physical properties of the TL tablets, including dissolution and swelling rates, were compared with those of the MM tablets and the pharmacokinetic parameters of the TL tablet were compared with those of an IR capsule in beagles and humans. Results Our results indicated that the same amount of a hydrophilic polymer in the formulations had similar dissolution profiles at 12 h, regardless of the tablet geometry. However, the degree of tablet swelling differed, with larger amounts of polymer in the tablets showing a greater degree of swelling. In addition, TL tablets swelled more rapidly compared with MM tablets. For the pharmacokinetic study of the TL tablet, the beagles demonstrated absorption results similar to those of an IR capsule, whereas the humans demonstrated low total absorption compared with an IR capsule. The time of the peak plasma concentration at 6 h in the fed state of humans coincided with the results of the study on beagles. Conclusion The novel TL tablet system of pregabalin may prove to be helpful in developing improved formulations with better continuous drug absorption for OAD administration.

The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled for launch in February 2020 to monitor air quality (AQ) at an unprecedented spatial and temporal resolution from a geostationary Earth orbit (GEO) for the first time. With the development of UV–visible spectrometers at sub-nm spectral resolution and sophisticated retrieval algorithms, estimates of the column amounts of atmospheric pollutants (O3, NO2, SO2, HCHO, CHOCHO, and aerosols) can be obtained. To date, all the UV–visible satellite missions monitoring air quality have been in low Earth orbit (LEO), allowing one to two observations per day. With UV–visible instruments on GEO platforms, the diurnal variations of these pollutants can now be determined. Details of the GEMS mission are presented, including instrumentation, scientific algorithms, predicted performance, and applications for air quality forecasts through data assimilation. GEMS will be on board the Geostationary Korea Multi-Purpose Satellite 2 (GEO-KOMPSAT-2) satellite series, which also hosts the Advanced Meteorological Imager (AMI) and Geostationary Ocean Color Imager 2 (GOCI-2). These three instruments will provide synergistic science products to better understand air quality, meteorology, the long-range transport of air pollutants, emission source distributions, and chemical processes. Faster sampling rates at higher spatial resolution will increase the probability of finding cloud-free pixels, leading to more observations of aerosols and trace gases than is possible from LEO. GEMS will be joined by NASA’s Tropospheric Emissions: Monitoring of Pollution (TEMPO) and ESA’s Sentinel-4 to form a GEO AQ satellite constellation in early 2020s, coordinated by the Committee on Earth Observation Satellites (CEOS).