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By NASA
4 min read
NASA’s Swift Studies Gas-Churning Monster Black Holes
A pair of monster black holes swirl in a cloud of gas in this artist’s concept of AT 2021hdr, a recurring outburst studied by NASA’s Neil Gehrels Swift Observatory and the Zwicky Transient Facility at Palomar Observatory in California. NASA/Aurore Simonnet (Sonoma State University) Scientists using observations from NASA’s Neil Gehrels Swift Observatory have discovered, for the first time, the signal from a pair of monster black holes disrupting a cloud of gas in the center of a galaxy.
“It’s a very weird event, called AT 2021hdr, that keeps recurring every few months,” said Lorena Hernández-García, an astrophysicist at the Millennium Institute of Astrophysics, the Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes, and University of Valparaíso in Chile. “We think that a gas cloud engulfed the black holes. As they orbit each other, the black holes interact with the cloud, perturbing and consuming its gas. This produces an oscillating pattern in the light from the system.”
A paper about AT 2021hdr, led by Hernández-García, was published Nov. 13 in the journal Astronomy and Astrophysics.
The dual black holes are in the center of a galaxy called 2MASX J21240027+3409114, located 1 billion light-years away in the northern constellation Cygnus. The pair are about 16 billion miles (26 billion kilometers) apart, close enough that light only takes a day to travel between them. Together they contain 40 million times the Sun’s mass.
Scientists estimate the black holes complete an orbit every 130 days and will collide and merge in approximately 70,000 years.
AT 2021hdr was first spotted in March 2021 by the Caltech-led ZTF (Zwicky Transient Facility) at the Palomar Observatory in California. It was flagged as a potentially interesting source by ALeRCE (Automatic Learning for the Rapid Classification of Events). This multidisciplinary team combines artificial intelligence tools with human expertise to report events in the night sky to the astronomical community using the mountains of data collected by survey programs like ZTF.
“Although this flare was originally thought to be a supernova, outbursts in 2022 made us think of other explanations,” said co-author Alejandra Muñoz-Arancibia, an ALeRCE team member and astrophysicist at the Millennium Institute of Astrophysics and the Center for Mathematical Modeling at the University of Chile. “Each subsequent event has helped us refine our model of what’s going on in the system.”
Since the first flare, ZTF has detected outbursts from AT 2021hdr every 60 to 90 days.
Hernández-García and her team have been observing the source with Swift since November 2022. Swift helped them determine that the binary produces oscillations in ultraviolet and X-ray light on the same time scales as ZTF sees them in the visible range.
The researchers conducted a Goldilocks-type elimination of different models to explain what they saw in the data.
Initially, they thought the signal could be the byproduct of normal activity in the galactic center. Then they considered whether a tidal disruption event — the destruction of a star that wandered too close to one of the black holes — could be the cause.
Finally, they settled on another possibility, the tidal disruption of a gas cloud, one that was bigger than the binary itself. When the cloud encountered the black holes, gravity ripped it apart, forming filaments around the pair, and friction started to heat it. The gas got particularly dense and hot close to the black holes. As the binary orbits, the complex interplay of forces ejects some of the gas from the system on each rotation. These interactions produce the fluctuating light Swift and ZTF observe.
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Watch as a gas cloud encounters two supermassive black holes in this simulation. The complex interplay of gravitational and frictional forces causes the cloud to condense and heat. Some of the gas is ejected from the system with each orbit of the black holes. F. Goicovic et al. 2016 Hernández-García and her team plan to continue observations of AT 2021hdr to better understand the system and improve their models. They’re also interested in studying its home galaxy, which is currently merging with another one nearby — an event first reported in their paper.
“As Swift approaches its 20th anniversary, it’s incredible to see all the new science it’s still helping the community accomplish,” said S. Bradley Cenko, Swift’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “There’s still so much it has left to teach us about our ever-changing cosmos.”
NASA’s missions are part of a growing, worldwide network watching for changes in the sky to solve mysteries of how the universe works.
Goddard manages the Swift mission in collaboration with Penn State, the Los Alamos National Laboratory in New Mexico, and Northrop Grumman Space Systems in Dulles, Virginia. Other partners include the University of Leicester and Mullard Space Science Laboratory in the United Kingdom, Brera Observatory in Italy, and the Italian Space Agency.
Download high-resolution images and videos.
By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Media Contact:
Claire Andreoli
301-286-1940
claire.andreoli@nasa.gov
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Last Updated Nov 13, 2024 Editor Jeanette Kazmierczak Related Terms
Astrophysics Black Holes Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research Goddard Space Flight Center Neil Gehrels Swift Observatory Science & Research Supermassive Black Holes The Universe View the full article
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By NASA
Earth Observer Earth Home Earth Observer Home Editor’s Corner Feature Articles Meeting Summaries News Science in the News Calendars In Memoriam More Archives 22 min read
Summary of the Second OMI–TROPOMI Science Team Meeting
Introduction
The second joint Ozone Monitoring Instrument (OMI)–TROPOspheric Monitoring Instrument (TROPOMI) Science Team (ST) meeting was held June 3–6, 2024. The meeting used a hybrid format, with the in-person meeting hosted at the National Center for Atmospheric Research (NCAR) in Boulder, CO. This was the first OMI meeting to offer virtual participation since the COVID-19 travel restrictions. Combining the onsite and virtual attendees, the meeting drew 125 participants – see Photo.
OMI flies on NASA’s Earth Observing System (EOS) Aura platform, launched July 15, 2004. TROPOMI flies on the European Space Agency’s (ESA)–Copernicus Sentinel-5 Precursor platform. OMI has collected nearly 20 years of data and TROPOMI now has amassed 5 years of data.
Meeting content was organized around the following four objectives:
discussion of the final reprocessing of OMI data (called Collection 4) and of data preservation; discussion of OMI data continuity and enhancements using TROPOMI measurements; development of unique TROPOMI products [e.g., methane (CH4)], applications (e.g., tracking emissions – and using them as indicators of socioeconomic and military activities), and new focus regions (e.g., Africa); and leverage synergies between atmospheric composition (AC) and greenhouse gas (GHG) missions, which form the international constellation of low Earth orbit (LEO) and geostationary orbit (GEO) satellites. The remainder of this article summarizes the highlights from each day of the meeting.
Photo. Group photo of the in-person participants at the OMI–TROPOMI Science Team meeting. Photo credit: Shaun Bush/NCAR’s Atmospheric Chemistry Observations & Modeling DAY ONE
The topics covered on the first day of the meeting included OMI instrument performance, calibration, final Collection 4 reprocessing, and plans for data preservation.
OMI and Data Products Update
Pieternel Levelt [Royal Netherlands Meteorological Institute (KNMI)—OMI Principal Investigator (PI) and NCAR’s Atmospheric Chemistry Observations & Modeling (ACOM) Laboratory—Director] began her presentation by dedicating the meeting to the memory of Johan de Vries, whose untimely death came as a shock to the OMI and TROPOMI teams – see In Memoriam: Johan de Vries for a celebration of his accomplishments and contributions to the OMI-TROPOMI team. She then went on to give a status update on OMI, which is one of two currently operating instruments on EOS Aura [the other being the Microwave Limb Sounder (MLS)]. OMI is the longest operating and stable ultraviolet–visible (UV-VIS) spectrometer. It continues to “age gracefully” thanks to its design, contamination control measures undertaken after the launch, and stable optical bench temperature. Lessons learned during integration of OMI on the Aura spacecraft (e.g., provide additional charged couple device shielding) and operations (i.e., monitor partial Earth-view port blockages) guided the development and operations of the follow-on TROPOMI mission.
Continued monitoring of OMI performance is crucial for extending science- and trend-quality OMI records to the end of the Aura mission (currently expected in 2026). Antje Ludewig [KNMI] described the new OMI Level-1B (L1B) processor (Collection 4), which is based on TROPOMI data flow and optimized calibrations. The processor has been transferred to the U.S. OMI ST, led by Joanna Joiner [NASA’s Goddard Space Flight Center (GSFC)]. Matthew Bandel [Science Systems and Applications, Inc. (SSAI)] described NASA’s new OMI monitoring tools.
Sergey Marchenko [SSAI] discussed OMI daily spectral solar irradiance (SSI) data, which are used for monitoring solar activity and can be compared with the dedicated Total and Spectral Solar Irradiance Sensor (TSIS-1) on the International Space Station. Continuation of OMI measurements will allow comparisons with the upcoming NASA TSIS-2 mission. Antje Inness [European Centre for Medium-range Weather Forecasts (ECMWF)] described operational assimilation of OMI and TROPOMI near-real time data into the European Copernicus Atmosphere Monitoring Service (CAMS) daily analysis/forecast and re-analysis – see Figure 1.
In Memoriam: Johan de Vries
Johan de Vries
June 10, 1956 – May 8, 2024 Johan de Vries [Airbus Netherlands—Senior Specialist Remote Sensing] passed away suddenly on May 8, 2024, after a distinguished career. As a member of the Ozone Monitoring Instrument (OMI)–TROPOspheric Monitoring Instrument (TROPOMI) program, Johan conceptualized the idea of using a two-dimensional (2D) charged couple detector (CCD) for the OMI imaging spectrometer. This “push-broom” design led to high-spatial resolution spectra combined with high-spatial resolution and daily global coverage capability. His pioneering design for OMI has now been repeated on several other U.S. and international atmospheric composition measuring instruments – in both low and geostationary orbits – that are either in orbit or planned for launch soon. This achievement ensures that Johan’s legacy will live on for many years to come as these push-broom Earth observing spectrometers result in unprecedented data for environmental research and applications. The OMI and TROPOMI teams express their deepest condolences to de Vries family and colleagues over this loss.
Figure 1. An example of TROPOMI pixel nitrogen dioxide (NO2) observations over Europe on September 8, 2018 [top] and the corresponding super observations [bottom] for a model grid of 0.5 x 0.5o. Cloudy locations are colored grey. TROPOMI super observations are tested for use in the European Centre for Medium Range Weather Forecasting (ECMWF) Copernicus Atmosphere Monitoring Service (CAMS) data assimilation framework and will also be used for combined OMI–TROPOMI gridded datasets. Figure credit: reprinted from a 2024 paper posted on EGUSphere. Updates on OMI and TROPOMI Level-2 Data Products
The U.S. and Netherlands OMI STs continue to collaborate closely on reprocessing and improving OMI and TROPOMI L2 science products. During the meeting, one or more presenters reported on each product, which are described in the paragraphs that follow.
Serena Di Pede [KNMI] discussed the latest algorithm updates to the Collection 4 OMI Total Column Ozone (O3) product, which is derived using differential absorption spectroscopy (DOAS). She compared results from the new algorithm with the previous Collection 3 and with both the TROPOMI and OMI NASA O3 total column (Collection 3) algorithms. Collection 4 improved on previous versions by reducing the retrieval fit error and the along-track stripes of the product.
Juseon “Sunny” Bak and Xiong Liu [both from Smithsonian Astrophysical Observatory (SAO)] gave updates on the status of the Collection 4 O3 profile products.
Lok Lamsal [GSFC/University of Maryland, Baltimore County (UMBC)] and Henk Eskes [KNMI] compared Collection 3 and Collection 4 of the nitrogen dioxide (NO2) products.
Zolal Ayzpour [SAO] discussed the status of the OMI Collection 4 formaldehyde (HCHO) product.
Hyeong-Ahn Kwon [SAO] presented a poster that updated the Glyoxal product.
Omar Torres [GSFC] and Changwoo Ahn [GSFC/SSAI] presented regional trend analyses using the re-processed OMI Collection 4 absorbing aerosol product – see Figure 2.
Figure 2. Reprocessed OMI records (from Collection 4) of monthly average aerosol optical depth (AOD) at 388 nm derived from the OMI aerosol algorithm (OMAERUV) over Western North America (WNA): 30°N–50°N, 110°W–128°W) [top] and over Eastern China (EC): 25°N–43°N, 112°E–124°E) [bottom]. A repeatable annual cycle over WNA occurred with autumn minimum at around 0.1 and a spring maximum in the vicinity of 0.4 during the 2005–2016 period. After 2017 much larger AOD maxima in the late summer are associated with wildfire smoke occurrence. Over EC (bottom) the 2005–2014 AOD record depicts a large spring maxima (0.7 and larger) due to long-range transport of dust and secondary pollution aerosols followed by late autumn minima (around 0.3). A significant AOD decrease is observed starting in 2015 with reduced minimum and maximum values to about 0.2 and 0.5 respectively. The drastic change in AOD load over this region is associated with pollution control measures enacted over the last decade. Figure credit: Changwoo Ahn/GSFC/SSAI and Omar Torres/GSFC Updates on EOS Synergy Products
Several presenters and posters during the meeting gave updates on EOS synergy products, where OMI data are combined with data from another instrument on one of the EOS flagships. These are described below.
Brad Fisher [SSAI] presented a poster on the Joint OMI–Moderate Resolution Imaging Spectroradiometer (MODIS) cloud products.
Wenhan Qin [GSFC/SSAI] presented a poster on the MODIS–OMI Geometry Dependent Lambertian Equivalent Surface Reflectivity (GLER) product.
Jerry Ziemke [GSFC and Morgan State University (MSU)] presented on the OMI–MLS Tropospheric Ozone product that showed post-COVID tropospheric O3 levels measured using this product, which are consistent with similar measurements obtained using other satellite O3 data – see Figure 3.
Figure 3. Anomaly maps of merged tropospheric column O3 (TCO) satellite data (Dobson Units) for spring–summer 2020–2023. In this context, an anomaly is defined as deseasonalized O3 data. The anomaly maps are derived by first calculating seasonal climatology maps for 2016–2019 (i.e., pre-COVID pandemic) and then subtracting these climatology maps from the entire data record.
Note: The sensors used in this analysis include: the Ozone Mapping and Profiler Suite (OMPS)/ Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) and Cross-track Infrared Sounder (CrIS) on the Joint Polar Satellite System (JPSS) missions, which currently include the joint NASA–NOAA Suomi National Polar-orbiting Partnership (Suomi NPP), NOAA-20, and NOAA-21; the Earth Polychromatic Imaging Camera (EPIC)/MERRA-2 on the Deep Space Climate Observatory (DSCOVR); the Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS), both on EOS Aura; the Infrared Atmospheric Sounding Interferometer (IASI)/ Fast Optimal Retrievals on Layers (FORLI), IASI/SOftware for Fast Retrievals of IASI Data (SOFRID), and IASI/Global Ozone Monitoring Experiment–2 (GOME2). IASI flies on the European MetOp-A, -B, and -C missions. The OMPS/MERRA-2 and EPIC/MERRA-2 products subtract coincident MERRA-2 stratospheric column O3 from total O3 to derive tropospheric column O3. Figure credit: Jerry Ziemke/GSFC and Morgan State University (MSU) Updates on Multisatellite Climate Data Records
The OMI ST also discussed refining and analyzing multisatellite climate data records (CDRs) that have been processed with consistent algorithms. Several presenters reported on this work, who are mentioned below.
Jenny Stavrakou [Koninklijk Belgisch Instituut voor Ruimte-Aeronomie, Royal Belgian Institute for Space Aeronomy (BIRA–IASB)], reported on work focusing on the OMI and TROPOMI HCHO CDR and Huan Yu [BIRA–IASB)] reported harmonized OMI and TROPOMI cloud height datasets based on improved O2-O2 absorption retrieval algorithm.
Lok Lamsal [GSFC/UMBC, Goddard Earth Sciences Technology and Research (GESTAR) II], Henk Eskes, and Pepijn Veefkind [KNMI] reported on the OMI and TROPOMI NO2 CDRs – see Figure 4.
Si-Wan Kim [Yonsei University, South Korea] reported on OMI and TROPOMI long-term NO2 trends.
Figure 4. OMI nitrogen dioxide (NO2) time series bridging the first GOME mission (which flew on the European Remote Sensing Satellite–2 (ERS–2) from 1995–2011 with limited coverage after 2003) and measurements from the two currently operating missions – OMI (2004–present) and TROPOMI (2017–present) – offer consistent climate data records that allow for studying long-term changes. This example shows tropospheric NO2 column time series from three instruments over Phoenix, AZ. The overlap between the OMI and TROPOMI missions allows for intercomparison between the two, which is crucial to avoid continuity-gaps in multi-instrument time series. The ERS-2 (GOME) had a morning equator crossing time (10:30 AM), while Aura (OMI) and Metop (TROPOMI) have afternoon equator crossing times of 1:45 PM and 1:30 PM respectively. Figure credit: Lok Lamsal/GSFC/University of Maryland, Baltimore County (UMBC) Update on Aura’s Drifting Orbit
Bryan Duncan [GSFC—Aura Project Scientist] closed out the first day with a presentation summarizing predictions of Aura’s drifting orbit. Overall, the impact of Aura’s drift is expected to be minor, and the OMI and MLS teams will be able to maintain science quality data for most data products. He thanked the OMI/TROPOMI ST and user community for expressing their strong support for continuing Aura observations until the end of the Aura mission in mid–2026.
DAY TWO
The second day of the meeting focused on current and upcoming LEO and GEO Atmospheric Composition (AC) missions.
TROPOMI Mission and Data Product Updates
Veefkind presented an update on the TROPOMI mission, which provides continuation and enhancements for all OMI products. Tobias Borssdorf [Stichting Ruimte Onderzoek Nederland (SRON), or Netherlands Institute for Space Research] explained how TROPOMI, with its innovative shortwave infrared (SWIR) spectrometer, measures CH4 and carbon monoxide (CO). This approach continues measurements that began by the Measurements of Pollution in the Troposphere (MOPITT) instrument on Terra.
Hiren Jethva [NASA Airborne Science Program] and Torres presented new TROPOMI near-UV aerosol products, including a new aerosol layer optical centroid height product, which takes advantage of the TROPOMI extended spectral range – see Figure 5.
Figure 5. Global gridded (0.10° x 0.10°) composite map of aerosol layer optical centroid height (AH) retrieved from TROPOMI O2-B band observations from May–September 2023. Figure credit: Hiren Jethva/NASA Airborne Science Program GEMS–TEMPO–Sentinel-4 (UVN): A Geostationary Air Quality Constellation
TROPOMI global observations serve as a de facto calibration standard used to homogenize a new constellation of three missions that will provide AC observations for most of the Northern Hemisphere from GEO. Two of the three constellation members are already in orbit. Jhoon Kim [Yonsei University—PI] discussed the Geostationary Environmental Monitoring Spectrometer (GEMS), launched on February 19, 2020 aboard the Republic of Korea’s GEO-KOMPSAT-2B satellite. It is making GEO AC measurements over Asia. The GEMS team is working on validating measurements of NO2 diurnal variations using ground-based measurements from the PANDORA Global Network over Asia and aircraft measurements from the ASIA–AQ field campaign.
Liu discussed NASA’s Tropospheric Emission Monitoring of Pollution (TEMPO) spectrometer, launched on April 7, 2023, aboard a commercial INTELSAT 40E satellite. From its GEO vantage point, TEMPO can observe the Continental U.S., Southern Canada, Mexico, and the coastal waters of the Northwestern Atlantic and Northeastern Pacific oceans.
Gonzales Abad [SAO] presented the first measurements from TEMPO. He explained that TEMPO’s design is similar to GEMS, but GEMS includes an additional visible and near infrared (VNIR) spectral channel (540–740 nm) to measure tropospheric O3, O2, and water vapor (H2Ov). TEMPO can perform optimized morning scans, twilight scans, and scans with high temporal resolution (5–10 minutes) over selected regions. Abad reported that the TEMPO team released L1B spectra and the first provisional public L2 products (Version 3), including NO2, HCHO, and total column O3. Andrew Rollins [National Oceanic and Atmospheric Administration’s (NOAA) Chemical Sciences Laboratory (CSL)] reported that the TEMPO team is working on validation of provisional data using both ground-based data from PANDORA spectrometers and data collected during several different airborne campaigns completed during the summer of 2023 and compiled on the AGES+ website.
Ben Veihelmann [ESA’s European Space Research and Technology Center—PI] explained that ESA’s Copernicus Sentinel-4 mission will be the final member of the GEO AC constellation. Veefkind summarized the Sentinel-4 mission, which is expected to launch on the Meteosat Third Generation (MTG)-Sounder 1 (MTG-S1) platform in 2025. The mission is dedicated to measuring air quality and O3 over Europe and parts of the Atlantic and North Africa. Sentinel-4 will deploy the first operational UV-Vis-NIR (UVN) imaging spectrometer on a geostationary satellite. (Airbus will build UVN, with ESA providing guidance.) Sentinel-4 includes two instruments launched in sequence on MTG-S1 and MTG-S2 platforms designed to have a combined lifetime of 15 years. The mission by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) will operate Sentinel-4, and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) or German Aerospace Center will be responsible for operational L2 processing.
These three GEO AC missions, along with the upcoming ESA/EUMETSAT/Copernicus LEO (morning orbit, 9:30 a.m.) Sentinel-5 (S5) mission, will complete a LEO–GEO satellite constellation that will enable monitoring of the most industrialized and polluted regions in the Northern Hemisphere into the 2030s. Sentinel-5 will not continue the OMI–TROPOMI data record in the early afternoon; however, it will be placed in the morning orbit and follow ESA’s Global Ozone Monitoring Experiment (GOME) and EUMETSAT GOME-2 missions. By contrast, GEO AC observations over the Southern Hemisphere are currently not available. Several presenters described ongoing projects for capacity building for LEO satellite air quality data uptake and emission monitoring in Africa and advocated for the new geostationary measurements.
Synergy with Other Current or Upcoming Missions
Attendees discussed the synergy between upcoming AC, GHG, and ocean color missions. Current trends in satellite AC measurements are toward increased spatial resolution and combined observations of short-lived reactive trace gases – which are important for air quality (AQ) monitoring – and long-lived GHG – which are important for climate monitoring and carbon cycle assessments. Some trace gases (e.g., O3 and CH4) are both polluters and GHG agents. Others [e.g., NO2 and sulfur dioxide (SO2 )] are aerosol [particulate matter (PM)] and O3 precursors and are used as proxies and spatial indicators for anthropogenic CO2 and CH4 emissions.
Yasjka Meijer [ESA—Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) Mission Scientist]) reviewed the plans for CO2M, which includes high-resolution measurements [~4 km2 (~1.5 mi2)] of CO2 , CH4 , and NO2.
Jochen Landgraf [SRON] described ESA’s new Twin Anthropogenic Greenhouse Gas Observers (TANGO) mission, which has the objective to measure CO2 , CH4 , and NO2 at even higher spatial resolution [~300 m (~984 ft)] using two small CubeSat spectrometers flying in formation.
Hiroshi Tanimoto [National Institute for Environmental Studies, Japan] described the Japan Aerospace Exploration Agency’s (JAXA) Global Observing SATellite for greenhouse gases and water cycle (GOSAT-GW) mission, which includes the Total Anthropogenic and Natural Emission mapping SpectrOmeter (TANSO-3) spectrometer to simultaneously measure CO2 , CH4, and NO2 with ~1–3 km (~0.6–1.8 mi) spatial resolution in focus mode. GOSAT-GW will also fly the Advanced Microwave Scanning Radiometer 3 (AMSR3).
Joanna Joiner [GSFC—Geostationary Extended Operations (GeoXO) Project Scientist and ACX Instrument Scientist] described the plans for the next-generation U.S. geosynchronous satellite constellation, which will consist of three satellites covering the full Earth disk: GEO-East, GEO-West, and GEO-Central. (By contrast, the current Geostationary Operational Environmental Satellite (GOES) series has two satellites: GOES–East and GOES–West.) GEO-Central will carry an advanced infrared sounder (GXS) for measuring vertical profiles of many trace gases, temperature and humidity, and a new UV-VIS spectrometer (ACX), which is a follow-on to TEMPO for AQ applications. Both GXS and ACX instruments will be built by BAE Systems, which acquired Ball Aerospace and Technology, and will also build the GeoXO ocean color spectrometer (OCX).
Andrew Sayer [UMBC] described NASA’s Plankton, Aerosols, Clouds, and ocean Ecosystem (PACE), which launched on February 8, 2024. The PACE payload includes a high-spatial resolution [~1 km (~0.6 mi) at nadir] Ocean Color Instrument (OCI), which is a UV-Vis-NIR spectrometer with discrete SWIR bands presenting additional opportunities for synergistic observations with the AC constellation. Sayer presented OCI “first light” aerosol data processed using the unified retrieval algorithm developed by Lorraine Remer [UMBC].
The second day concluded with a joint crossover session with NASA’s Health and Air Quality Applied Sciences Team (HAQAST) followed by a poster session. Several OMI–TROPOMI STM participants presented on a variety of topics that illustrate how OMI and TROPOMI data are being used to support numerous health and AQ applications. Duncan, who is also a member of HAQAST team, presented “20 years of health and air quality applications enabled by OMI data.” He highlighted OMI contributions to AQ and health applications, including NO2 trend monitoring, inferring trends of co-emitted species [e.g., CO2, CO, some Volatile Organic Compounds (VOCs)], validation of new satellite missions (e.g., TEMPO, PACE), and burden of disease studies.
DAY THREE
Discussions on the third day focused on advanced retrieval algorithms, leading to new products and new applications for OMI and TROPOMI data. Several presentations described applications of TROPOMI CH4 data and synergy with small satellites.
Advanced Retrieval Algorithms and New Data Products
Ilse Aben [SRON] described TROPOMI global detection of CH4 super-emitters using an automated system based on Machine Learning (ML) techniques – see Figure 6. Berend Schuit [SRON] provided additional detail on these methods. He introduced the TROPOMI CH4 web site to the meeting participants. He explained how TROPOMI global CH4 measurements use “tip-and-cue” dedicated satellites with much higher spatial resolution instruments [e.g., GHGSat with ~25-m (~82-ft) resolution] to scan for individual sources and estimate emission rates. Most CH4 super-emitters are related to urban areas and/or landfills, followed by plumes from gas and oil industries and coal mines.
Figure 6. Methane plume map produced by SRON shows TROPOMI large CH4 emission plumes for the week of the OMI–TROPOMI meeting (June 3–6, 2024). Figure credit: Itse Aben/Stichting Ruimte Onderzoek Nederland (SRON) Alba Lorente [Environmental Defense Fund—Methane Scientist] introduced a new MethaneSAT satellite launched in March 2024, which aims to fill the gap in understanding CH4 emissions on a regional scale [200 x 200 km2 (~77 x 77 mi2)] from at least 80% of global oil and gas production, agriculture, and urban regions. Alex Bradley [University of Colorado, Boulder] described improvements to TROPOMI CH4 retrievals that were achieved by correcting seasonal effects of changing surface albedo.
Daniel Jacob [Harvard University] presented several topics, including the highest resolution [~30 m (~98 ft)] NO2 plume retrievals from Landsat-8 – see Figure 7 – and Sentinel-2 imagers. He also discussed using a ML technique trained with TROPOMI data to improve NO2 retrievals from GEMS and modeling NO2 diurnal cycle and emission estimates. He introduced the ratio of ammonia (NH3) to NO2 (NH3/NO2) as an indicator of particulate matter with diameters less than 2.5 µm (PM2.5) nitrate sensitivity regime. Jacob emphasized the challenges related to satellite NO2 retrievals (e.g., accounting for a free-tropospheric NO2 background and aerosols).
Figure 7. Landsat Optical Land Imager (OLI) image, obtained on October 17, 2021 over Saudi Arabia, shows power plant exhaust, which contains nitrogen dioxide (NO2) drifting downwind from the sources (the two green circles are the stacks). The ultra-blue channel (430–450 nm) on OLI enables quantitative detection of NO2 in plumes from large point sources at 30-m (~98-ft) resolution. This provides a unique ability for monitoring point-source emissions of oxides of nitrogen (NOx). The two stacks in the image are separated by 2 km (~1.2 mi). Figure credit: Daniel Jacob – repurposed from a 2024 publication in Proceedings of the National Academies of Sciences (PNAS) Steffen Beirle [Max Planck Institute for Chemistry, Germany] explained his work to fit TROPOMI NO2 column measurements to investigate nitric oxide (NO) to NO2 processing in power plant plumes. Debra Griffin [Environment and Climate Change Canada (ECCC)] used TROPOMI NO2 observations and ML random forest technique to estimate NO2 surface concentrations. Sara Martinez-Alonso [NCAR] investigated geographical and seasonal variations in NO2 diurnal cycle using GEMS and TEMPO data. Ziemkecombined satellite O3 data to confirm a persistent low anomaly (~5–15%) in tropospheric O3 after 2020. Jethva presented advanced OMI and TROPOMI absorbing aerosol products. Yu described improved OMI and TROPOMI cloud datasets using the O2-O2 absorption band at 477 nm. Nicholas Parazoo [Jet Propulsion Laboratory (JPL)] described TROPOMI Fraunhofer line retrievals of red solar-induced chlorophyll fluorescence (SIF) near O2-B band (663–685 nm) to improve mapping of ocean primary productivity. Liyin He [Duke University] described using satellite terrestrial SIF data to study the effect of particulate pollution on ecosystem productivity.
New Applications
Zachary Fasnacht [SSAI] used OMI and TROPOMI spectra to train a neural network to gap-fill MODIS and Visible Infrared Imaging Radiometer Suite (VIIRS) ocean color data under aerosol, sun glint, and partly cloudy conditions. This ML method can also be applied to PACE OCI spectra. Anu-Maija Sundström [Finnish Meteorological Institute (FMI)] used OMI and TROPOMI SO2 and O3 data as proxies to study new particle formation events. Lindsey Anderson [University of Colorado, Boulder] described how she used TROPOMI NO2 and CO measurements to estimate the composition of wildfire emissions and their effect on forecasted air quality. Heesung Chong [SAO] applied OMI bromine oxide (BrO) retrievals to the NOAA operational Ozone Mapping and Profiling Suite Nadir Mapper (OMPS-NM) on joint NOAA–NASA Suomi-National Polar-orbiting Partnership (Suomi NPP) satellite with the possibility to continue afternoon measurements using similar OMPS-NM instruments on the four Joint Polar Satellite System missions (JPSS-1,-2,-3,-4) into the 2030s. (JPSS-1 and -2 are now in orbit and known as NOAA-20 and -21 respectively; JPSS-4 is planned for launch in 2027, with JPSS-3 currently targeted for 2032.)
Kim demonstrated the potential for using satellite NO2 and SO2 emissions as a window into socioeconomic issues that are not apparent by other methods. For example, she showed how OMI and TROPOMI data were widely used to monitor air quality improvements in the aftermath of COVID-19 lockdowns. (Brad Fisher [SSAI] presented a poster on a similar topic.)
Cathy Clerbaux [Center National d’Études Spatiale (CNES), or French Space Agency] showed how her team used TROPOMI NO2 data to trace the signal emitted by ships and used this information to determine how the shipping lanes through the Suez Canal changed in response to unrest in the Middle East. Iolanda Ialongo [FMI] showed a similar drop of NO2 emissions over Donetsk region due to the war in Ukraine. Levelt showed how OMI and TROPOMI NO2 data are used for capacity-building projects and for air quality reporting in Africa. She also advocated for additional geostationary AQ measurements over Africa.
DAY FOUR
Discussions on the final day focused on various methods of assimilating satellite data into air quality models for emission inversions and aircraft TEMPO validation campaigns. The meeting ended with Levelt giving her unique perspective on the OMI mission, as she reflected on more than two decades being involved with the development, launch, operation, and maintenance of OMI.
Assimilating Satellite Data into Models for Emissions
Brian McDonald [CSL] described advance chemical data assimilation of satellite data for emission inversions and the GReenhouse gas And Air Pollutants Emissions System (GRA2PES). He showed examples of assimilations using TROPOMI and TEMPO NO2 observations to adjust a priori emissions. He also showed that when TEMPO data are assimilated, NOx emissions adjust faster and tend to perform better at the urban scale. Adrian Jost [Max Planck Institute for Chemistry] described the ESA-funded World Emission project to improve pollutant and GHG emission inventories using satellite data. He showed examples of TROPOMI SO2 emissions from large-point sources and compared the data with bottom-up and NASA SO2 emissions catalogue.
Ivar van der Velde [SRON] presented a method to evaluate fire emissions using new satellite imagery of burned area and TROPOMI CO. Helene Peiro [SRON] described her work to combine TROPOMI CO and burned area information to compare the impact of prescribed fires versus wildfires on air quality in the U.S. She concluded that prescribed burning reduces CO pollution. Barbara Dix [University of Colorado, Boulder, Cooperative Institute for Research in Environmental Sciences] derived NOx emissions from U.S. oil and natural gas production using TROPOMI NO2 data and flux divergence method. She estimated TROPOMI CH4 emissions from Denver–Julesburg oil and natural gas production. Dix explained that the remaining challenge is to separate oil and gas emissions from other co-located CH4 sources. Ben Gaubert [NCAR, Atmospheric Chemistry Observations and Modeling] described nonlinear and non-Gaussian ensemble assimilation of MOPITT CO using the data assimilation research testbed (DART).
Andrew (Drew) Rollings [CSL] presented first TEMPO validation results from airborne field campaigns in 2023 (AGES+ ), including NOAA CSL Atmospheric Emissions and Reactions observed from Megacities to Marine Aeras (AEROMMA) and NASA’s Synergistic TEMPO Air Quality Science (STAQS) campaigns.
A Reflection on Twenty Years of OMI Observations
Levelt gave a closing presentation in which she reflected on her first involvement with the OMI mission as a young scientist back in 1998. This led to a collaboration with the international ST to develop the instrument, which was included as part of Aura’s payload when it launched in July 2004. She reminisced about important highlights from 2 decades of OMI, e.g., the 10-year anniversary STM at KNMI in 2014 (see “Celebrating Ten Years of OMI Observations,” The Earth Observer, May–Jun 2014, 26:3, 23–30), and the OMI ST receiving the NASA/U.S. Geological Survey Pecora award in 2018 and the American Meteorological Society’s Special award in 2021.
Levelt pointed out that in this combined OMI–TROPOMI meeting the movement towards using air pollution and GHG data together became apparent. She ended by saying that the OMI instrument continues to “age gracefully” and its legacy continues with the TROPOMI and LEO–GEO atmospheric composition constellation of satellites that were discussed during the meeting.
Conclusion
Overall, the second OMI–TROPOMI STM acknowledged OMI’s pioneering role and TROPOMI’s unique enhancements in measurements of atmospheric composition:
Ozone Layer Monitoring: Over the past two decades, OMI has provided invaluable data on the concentration and distribution of O3 in the Earth’s stratosphere. This data has been crucial for understanding and monitoring the recovery of the O3 layer following international agreements, such as the Montreal Protocol. Air Quality Assessment: OMI’s high-resolution measurements of air pollutants, such as NO2, SO2, and HCHO, have significantly advanced our understanding of air quality. This information has been vital for tracking pollution sources, studying their transport and transformation, and assessing their impact on human health and the environment. Climate Research: The data collected by OMI has enhanced our knowledge of the interactions between atmospheric chemistry and climate change. These insights have been instrumental in refining climate models and improving our predictions of future climate scenarios. Global Impact: The OMI instrument has provided near-daily global coverage of atmospheric data, which has been essential for scientists and policymakers worldwide. The comprehensive and reliable data from OMI has supported countless research projects and informed decisions aimed at protecting and improving our environment. OMI remains one of the most stable UV/Vis instruments over its two decades of science and trend quality data collection. The success of the OMI and TROPOMI instruments is a testament to the collaboration, expertise, and dedication of both teams.
Nickolay Krotkov
NASA’s Goddard Space Flight Center
Nickolay.a.krotkov@nasa.gov
Pieternel Levelt
National Center for Atmospheric Research, Atmospheric Chemistry Observations & Modeling
levelt@ucar.edu
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By NASA
Researchers demonstrated the feasibility of 3D bioprinting a meniscus or knee cartilage tissue in microgravity. This successful result advances technology for bioprinting tissue to treat musculoskeletal injuries on long-term spaceflight or in extraterrestrial settings where resources and supply capacities are limited.
BFF Meniscus-2 evaluated using the BioFabrication Facility to 3D print knee cartilage tissue using bioinks and cells. The meniscus is the first engineered tissue of an anatomically relevant shape printed on the station. Manufactured human tissues have potential as alternatives to donor organs, which are in short supply. Bioprinting in microgravity overcomes some of the challenges present in Earth’s gravity, such as deformation or collapse of tissue structures.
A human knee meniscus 3D bioprinted in space using the International Space Station’s BioFabrication Facility.Redwire Complex cultures of central nervous system cells known as brain organoids can be maintained in microgravity for long periods of time and show faster development of neurons than cultures on Earth. These findings could help researchers develop treatments for neurodegenerative diseases on Earth and address potential adverse neurological effects of spaceflight.
Cosmic Brain Organoids examined growth and gene expression in 3D organoids created with neural stem cells from individuals with primary progressive multiple sclerosis and Parkinson’s disease. Results could improve understanding of these neurological diseases and support development of new treatments. Researchers plan additional studies on the underlying causes of the accelerated neuron maturation.
Neural growth in brain organoids that spent more than a month in space. Jeanne Frances Loring, National Stem Cell Foundation Researchers demonstrated that induced pluripotent stem cells (iPSCs) can be processed in microgravity using off the-shelf cell culture materials. Using standard laboratory equipment and protocols could reduce costs and make space-based biomedical research accessible to a broader range of scientists and institutions.
Stellar Stem Cells Ax-2 evaluated how microgravity affects methods used to generate and grow stem cells into a variety of tissue types on the ground. iPSCs can give rise to any type of cell or tissue in the human body, and insight into processing in space could support their use in regenerative medicine and future large-scale biomanufacturing of cellular therapeutics in space.
NASA astronaut Peggy Whitson, an Axiom Mission 2 crew member, works on stem cell research on a previous mission. NASA/Shane KimbroughView the full article
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By Space Force
Space Delta 5 and the Combined Space Operations Center hosted a three-day working group to collaborate on current efforts for developing a shared Space Common Operational Picture.
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By NASA
4 Min Read Student-Built Capsules Endure Heat of Re-entry for NASA Science
The five capsules of the KREPE-2 mission are pictured on Earth prior to flight. Credits: University of Kentucky. In July 2024, five student-built capsules endured the scorching heat of re-entry through Earth’s atmosphere as part of the second Kentucky Re-Entry Probe Experiment (KREPE-2). Scientists are now analyzing the data from the KREPE-2 experiments, which could advance the development of heat shields that protect spacecraft when they return to Earth.
The mission was designed to put a variety of heat shield prototypes to the test in authentic re-entry conditions to see how they would perform. These experimental capsules, which were built by students at the University of Kentucky and funded by the NASA Established Program to Stimulate Competitive Research (EPSCoR) within NASA’s Office of STEM Engagement, all survived more than 4,000 degrees Fahrenheit during descent.
The football-sized capsules also successfully transmitted valuable data via the Iridium satellite network along their fiery journey. The trove of information they provided is currently being analyzed to consider in current and future spacecraft design, and to improve upon designs for future experiments.
“These data – and the instruments used to obtain the data – assist NASA with designing and assessing the performance of current and new spacecraft that transport crew and cargo to and from space,” said Stan Bouslog, thermal protection system senior discipline expert at NASA’s Johnson Space Center in Houston who served as the agency’s technical monitor for the project.
Taking the Plunge: Communicating Through a Fiery Descent
“The only way to ‘test like you fly’ a thermal protection system is to expose it to actual hypersonic flight through an atmosphere,” Bouslog said.
The self-contained capsules launched aboard an uncrewed Northrop Grumman Cygnus spacecraft in January 2024 along with other cargo bound for the International Space Station. The cargo craft detached from the space station July 12 as the orbiting laboratory flew above the south Atlantic Ocean. As the Cygnus spacecraft began its planned breakup during re-entry, the KREPE-2 capsules detected a signal – a temperature spike or acceleration – to start recording data and were released from the vehicle. At that point, they were traveling at a velocity of about 16,000 miles per hour at an altitude of approximately 180,000 feet.
The University of Kentucky student team and advisors watched and waited to learn how the capsules had fared.
As the capsules descended through the atmosphere, one group watched from aboard an aircraft flying near the Cook Islands in the south Pacific Ocean, where they tracked the return of the Cygnus spacecraft. The flight was arranged in partnership with the University of Southern Queensland in Toowoomba, Queensland, Australia, and the University of Stuttgart in Stuttgart, Germany. Alexandre Martin, professor of mechanical and aerospace engineering at the University of Kentucky and the principal investigator for the experiment, was on that flight.
“We flew in close to the re-entry path to take scientific measurements,” Martin said, adding that they used multiple cameras and spectrometers to observe re-entry. “We now have a much better understanding of the break-up event of the Cygnus vehicle, and thus the release of the capsules.”
Meanwhile, members of the University of Kentucky’s Hypersonic Institute had gathered at the university to watch as KREPE-2 data arrived via email. All five successfully communicated their flight conditions as they hurtled to Earth.
“It will take time to extract the data and analyze it,” Martin said. “But the big accomplishment was that every capsule sent data.”
Members of the University of Kentucky student team have begun analyzing the data to digitally reconstruct the flight environment at the time of transmission, providing key insights for future computer modeling and heat shield design.
An artist’s rendering of one of the KREPE-2 capsules during re-entry. A. Martin, P. Rodgers, L. Young, J. Adams, University of Kentucky Building on Student Success
The mission builds on the accomplishments of KREPE-1, which took place in December 2022. In that experiment, two capsules recorded temperature measurements as they re-entered Earth’s atmosphere and relayed that data to the ground.
The extensive dataset collected during the KREPE-2 re-entry includes heat shield measurements, such as temperature, as well as flight data including pressure, acceleration, and angular velocity. The team also successfully tested a spectrometer that provided spectral data of the shockwave in front of a capsule.
“KREPE-1 was really to show we could do it,” Martin said. “For KREPE-2, we wanted to fully instrument the capsules and really see what we could learn.”
KREPE-3 is currently set to take place in 2026.
The ongoing project has provided valuable opportunities for the University of Kentucky student team, from undergrads to PhD students, to contribute to spaceflight technology innovation.
“This effort is done by students entirely: fabrication, running simulations, handling all the NASA reviews, and doing all the testing,” Martin said. “We’re there supervising, of course, but it’s always the students who make these missions possible.”
Related links:
EPSCoR Space Station Research Explorer: Kentucky Re-entry Probe Experiment-2 Science Launches to Space Station on NASA’s 20th Northrop Grumman Mission Big Goals, Small Package: Enabling Compact Deliveries from Space Keep Exploring Discover More STEM Topics From NASA
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