Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) is a NASA Earth-observing satellite mission that will continue and advance observations of global ocean color, biogeochemistry, and ecology, as well as the carbon cycle, aerosols and clouds. PACE will be used to identify the extent and duration of phytoplankton blooms and improve understanding of air quality. These and other uses of PACE data will benefit the economy and society, especially sectors that rely on water quality, fisheries and food security.
After being proposed for cancellation under President Trump’s FY 2018 budget, it was restored by Congress. The PACE project is managed by NASA Goddard Space Flight Center. The main instrument and bus were designed and built at Goddard Space Flight Center.
On 4 February 2020, NASA announced the selection of SpaceX to launch PACE on a Falcon 9, at a total cost to NASA of US$80.4 million, including the launch service and other mission-related costs. The total cost of the mission is $964 million, which includes spacecraft construction, launch, and operations. PACE successfully launched on 8 February 2024.
The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone levels have dropped to as low as 33 percent of their pre-1975 values. The ozone hole occurs during the Antarctic spring, from September to early December, as strong westerly winds start to circulate around the continent and create an atmospheric container. Within this polar vortex, over 50 percent of the lower stratospheric ozone is destroyed during the Antarctic spring.
As explained above, the primary cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction. The Cl-catalyzed ozone depletion can take place in the gas phase, but it is dramatically enhanced in the presence of polar stratospheric clouds (PSCs).
These polar stratospheric clouds form during winter, in the extreme cold. Polar winters are dark, consisting of three months without solar radiation (sunlight). The lack of sunlight contributes to a decrease in temperature and the polar vortex traps and chills the air. Temperatures hover around or below −80 °C. These low temperatures form cloud particles. There are three types of PSC clouds—nitric acid trihydrate clouds, slowly cooling water-ice clouds, and rapid cooling water-ice (nacreous) clouds—provide surfaces for chemical reactions whose products will, in the spring lead to ozone destruction.
The photochemical processes involved are complex but well understood. The key observation is that, ordinarily, most of the chlorine in the stratosphere resides in “reservoir” compounds, primarily chlorine nitrate (ClONO2) as well as stable end products such as HCl. The formation of end products essentially removes Cl from the ozone depletion process. The former sequester Cl, which can be later made available via absorption of light at shorter wavelengths than 400 nm. During the Antarctic winter and spring, however, reactions on the surface of the polar stratospheric cloud particles convert these “reservoir” compounds into reactive free radicals (Cl and ClO). Denitrification is the process by which the clouds remove NO2 from the stratosphere by converting it to nitric acid in PSC particles, which then are lost by sedimentation. This prevents newly formed ClO from being converted back into ClONO2.
The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is greatest during spring. During winter, even though PSCs are at their most abundant, there is no light over the pole to drive chemical reactions. During the spring, however, sunlight returns and provides energy to drive photochemical reactions and melt the polar stratospheric clouds, releasing considerable ClO, which drives the hole mechanism. Further warming temperatures near the end of spring break up the vortex around mid-December. As warm, ozone and NO2-rich air flows in from lower latitudes, the PSCs are destroyed, the enhanced ozone depletion process shuts down, and the ozone hole closes.
Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much smaller ozone depletion through homogeneous gas-phase reactions, which occurs primarily in the upper stratosphere.
Video credit: NASA’s Ames Research Center/Bishop’s University /Jason Rowe
The Surface Water and Ocean Topography (SWOT) mission is a satellite altimeter jointly developed and operated by NASA and CNES, the French space agency, in partnership with the Canadian Space Agency (CSA) and UK Space Agency (UKSA). The objectives of the mission are to make the first global survey of the Earth’s surface water, to observe the fine details of the ocean surface topography, and to measure how terrestrial surface water bodies change over time.
While past satellite missions like the Jason series altimeters (TOPEX/Poseidon, Jason-1, Jason-2, Jason-3) have provided variation in river and lake water surface elevations at select locations, SWOT will provide the first truly global observations of changing water levels, stream slopes, and inundation extents in rivers, lakes, and floodplains. In the world’s oceans, SWOT will observe ocean circulation at unprecedented scales of 15–25 km (9.3–15.5 mi), approximately an order of magnitude finer than current satellites. Because it uses wide-swath altimetry technology, SWOT will almost completely observe the world’s oceans and freshwater bodies with repeated high-resolution elevation measurements, allowing observations of variations.
Over the past few years, machine learning techniques have been increasingly used to analyze the vast amount of data collected by the Landsat mission, which has been circling the globe for over 50 years. The data has been used to classify different types of land cover, detect changes to landscapes over time, and map the impact of human activity on the environment. With the field constantly evolving, researchers are developing new deep learning models to improve the accuracy and efficiency of the analysis and extract even more information from the data. Here are just a few examples of how the combination of Landsat data and machine learning is providing a better understanding of our planet’s past, present, and future.
Video credit: NASA’s Goddard Space Flight Center/Scientific Visualization Studio/Chris Burns [KBRWyle]: Lead Producer/Chris Burns [KBRWyle]: Lead Writer
Tropical Cyclone Freddy lasted more than five weeks. Once a very powerful Category 5 cyclone, Freddy first made landfall along the east coast of Madagascar on February 21st, 2023 just north of the town of Mananjary as a Category 3 cyclone with average winds reported at 130 km/h (~81 mph) with gusts up to 180 km/h (~112 mph). After crossing over Madagascar, Freddy continued westward over the Mozambique Channel before making landfall again and for the first time along the east coast of Mozambique just south of Vilankulos as a moderate tropical storm with sustained winds estimated at 50 mph. However, despite being weaker at landfall, Freddy has resulted in widespread flooding across parts of Mozambique due to the storm stalling out near the coast after making landfall. Incredibly, Freddy then drifted back out over the Mozambique Channel, nearly making landfall again along the southwest coast of Madagascar, before changing direction, re-intensifying, weakening, re-intensifying one last time, and making landfall for the 2nd time in Mozambique as a Category 1 cyclone near Quelimane with sustained winds reported at 90 mph on the 11th of March.
Credit: NASA’s Goddard Space Flight Center/Ryan Fitzgibbons (KBRwyle): Lead Producer, Lead Editor/Aaron E. Lepsch (ADNET): Technical Support/George Huffman (NASA/GSFC): Lead Scientist, Lead Narrator/B. Jason West (ADNET): Lead Visualizer/Stephen Lang (SSAI): Lead Writer/Music: “Enlightenment,†Universal Production Music
Landsat 8 is an American Earth observation satellite launched on 11 February 2013. It is the eighth satellite in the Landsat program; the seventh to reach orbit successfully. Originally called the Landsat Data Continuity Mission (LDCM), it is a collaboration between NASA and the United States Geological Survey (USGS). NASA Goddard Space Flight Center in Greenbelt, Maryland, provided development, mission systems engineering, and acquisition of the launch vehicle while the USGS provided for development of the ground systems and will conduct on-going mission operations. It comprises the camera of the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS), which can be used to study Earth surface temperature and is used to study global warming.
The satellite was built by Orbital Sciences Corporation, who served as prime contractor for the mission. The spacecraft’s instruments were constructed by Ball Aerospace & Technologies and NASA’s Goddard Space Flight Center (GSFC), and its launch was contracted to United Launch Alliance (ULA). During the first 108 days in orbit, LDCM underwent checkout and verification by NASA and on 30 May 2013 operations were transferred from NASA to the USGS when LDCM was officially renamed to Landsat 8.
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