US-French Satellite Takes Stock of World’s River Water - EARTH/UNIVERSE

Sunlight glints off one of the solar panels of the SWOT satellite in this artist’s concept. The antennas of the mission’s key instrument — the Ka-band Radar Interferometer (KaRIn) — collect data along a swath 30 miles (50 kilometers) wide on either side of the satellite.

CNES

In a first, a space mission led by NASA and France has tracked Earth’s rivers swelling and shrinking from month to month over the course of a year and found significantly less of a swing than previous model-based estimates. A record drought in the Amazon likely influenced the tally made by the Surface Water and Ocean Topography (SWOT) satellite. The findings also reveal new details about the underwater topography of the world’s river channels.

Launched in 2022, SWOT is a collaboration between NASA and the French space agency CNES (Centre National d’Études Spatiales). It is the first satellite capable of surveying not only the ocean, but also nearly all the world’s lakes and rivers with ultraprecision. While SWOT does not measure the absolute volume of rivers, it can track their width, surface height, and slope changing over time.

Traditionally, hydrologists have relied on models to calculate river storage changes, or they multiplied altimeter estimates of height by optical or radar estimates of width. In contrast, SWOT measures both dimensions, height and width, at the same time using its sensitive Ka-band Radar Interferometer (KaRIn) instrument to bounce microwaves off the water’s surface and time how long the signal takes to return. The new study, published Wednesday in Nature, analyzed nearly 1.6 million such observations.

The analysis paints a picture of some 127,000 river segments rising and falling between October 2023 and September 2024. In aggregate, river volumes varied by almost 83 trillion gallons (313 cubic kilometers). That’s about 28% less of a swing than the lowest previous estimates, a result likely skewed by extremely dry conditions during that period in the Amazon, home to Earth’s largest river by volume. 

Earth’s rivers pulse like capilleries in this visualization using data from the SWOT mission. The world tour zooms in on iconic rivers including the Amazon, which in the span of a year gained and lost enough water to fill 68 million Olympic-size swimming pools.
NASA’s Scientific Visualization Studio

New way to map river channels 

Even gripped by drought, the Amazon River varied more than any other during the year, gaining and losing more than 45 trillion gallons (172 cubic kilometers) — enough to cover the entire state of California in more than a foot of water.

More surprisingly, the world’s longest river, the Nile, varied less than expected, with volumes changing by only 2.2 trillion gallons (8.5 cubic kilometers). Possible explanations include upstream damming and severe drought, along with challenges that come with learning to work with a new satellite instrument.

Cedric David, who leads the SWOT research team that conducted the work at NASA’s Jet Propulsion Laboratory in Southern California, said the findings are a first look and the role of large floodplain dynamics remain to be fully determined. Still, such an accounting has been elusive until now. River gauges are sparse in areas, and some channels too remote for boat and ground surveys. Longstanding questions, such as how fast do rivers flow and how much rainwater and snowmelt runs into them, have added to the uncertainty.

“We’re starting to untangle some of the really tough questions SWOT was built for,” David said. “This is just the beginning.”

Tracking rivers as they swell and shrink is also helping scientists visualize something that can be challenging to survey in person: the underlying shape of riverbanks and beds. Such contours influence everything from shipping to flooding but have remained largely unmapped in many places, noted Arnaud Cerbelaud, a postdoctoral research fellow at JPL who co-led the study.

The new SWOT data provides a window into river channels ranging from concave to convex, steep to gentle, and stable to highly variable. In the Amazon, Mississippi, Orinoco, Yangtze, Ganges, Mekong and Yenisei rivers, for example, observed water levels vary by more than 32 feet (10 meters) from peak to trough.

“The implications go far beyond hydrology and will help us understand how water moves through the global Earth system,” Cerbelaud said. 

Source: US-French Satellite Takes Stock of World’s River Water - NASA

Technology Originally Developed for Space Missions Now Integral to Everyday Life - NASA Science Editorial Team

Groundbreaking “camera-on-a-chip” technology that was originally developed at NASA’s Jet Propulsion Laboratory (JPL) for use in space missions is currently employed in billions of devices like cell phones that are used daily by people worldwide.

Eric Fossum (in the center of the front row) and the team that invented the CMOS image sensor on site at NASA’s Jet Propulsion Laboratory.

Courtesy NASA/JPL-Caltech

In the 1980s, sensors used to produce high-quality images for space science (including the amazing images from NASA's Hubble Space Telescope) and other applications employed charge coupled device (CCD) technology. Dr. Eric Fossum was originally hired at JPL in 1990 to advance CCD technology for use in interplanetary space missions, but he ended up advancing another technology called complementary metal-oxide semiconductor (CMOS) technology for that purpose and much more. While at JPL, Fossum took advantage of a technique commonly used for CCDs and applied it to CMOS sensors to develop the first CMOS active pixel image sensor. This development began a chain of events that led to the present use of CMOS technology not only in space science missions, but also in billions of cameras in smartphones, webcams, automobiles, and medical devices used worldwide.

A new technology emerges…

In 1990, CCDs were the primary technology used to generate high-quality images. CCD sensors consist of arrays of pixels that convert light into electric charges. The charge from each pixel is transferred step-by-step to an output amplifier at the corner of the sensor and converted to a voltage that represents the brightness of the light received at the corresponding pixel. The data from all the pixels is then aggregated to generate an image. While CCD cameras can produce very high-quality images that are suitable for scientific use, they require a lot of power and an efficient charge transfer process to be effective.

CMOS sensors, on the other hand, have signal amplifiers within each pixel and signals can be read directly from each pixel instead of being transferred long distances to an amplifier for conversion. CMOS sensors therefore require less voltage to operate than CCDs and issues with the charge transfer process such as radiation susceptibility are greatly reduced. Although CMOS sensors existed in the 1990s, they produced too much noise to produce high-quality images required for science applications.

To reduce the signal noise typical of CMOS sensors at that time, Fossum applied a technique that was often used in CCD devices. This technique—called “intra-pixel charge transfer with correlated double sampling”—enables a double measurement of a pixel’s voltage without and with the light-generated charge. Subtracting the values of these two samples enables noise to be suppressed, improving the signal-to-noise ratio.

The next steps

Soon several companies signed Technology Cooperation Agreements with JPL and partnered with Fossum and his colleagues to develop the promising new technology. In 1995, Fossum and co-worker Dr. Sabrina Kemeny licensed the technology from CalTech and founded a company called Photobit to develop CMOS sensors. In 1996, Fossum left JPL to work at Photobit full time. The Photobit, team further refined the CMOS technology to get it closer to CCD capabilities, reduce power requirements, and make manufacturing cheaper.

Shortly thereafter, CMOS cameras started to be used in webcams, “pill cams” (small, swallowable devices that incorporate a tiny camera to take thousands of high-resolution images of the digestive tract), and other applications. In 2001 Photobit was acquired by Micron Technology, a larger company that devoted even more resources to development of CMOS technology. With the subsequent explosion of the cell phone industry, by 2013 more than a billion CMOS sensors were manufactured each year, and today that number has grown to about seven billion per year.

Where are these sensors now?

The CMOS technology Dr. Fossum originally developed has not only enabled space science, it has been infused into devices we depend on every day, dramatically and positively transforming many aspects of our lives. Virtually all digital still and video cameras, including those on cell phones, employ them. In addition, CMOS technology is used in automotive electronics, webcams, sports cameras, industrial equipment, security cameras including doorbells, and cinematography cameras, and for medical and dental imaging, among many other applications.

A frame from a video made from images taken by the Wide-Field Imager for Solar Probe (WISPR) instrument (which employs CMOS technology) onboard NASA's Parker Solar Probe. This image was captured during the mission’s record-breaking flyby of the Sun on Dec. 25, 2024, and shows the solar wind racing out from the Sun’s outer atmosphere, the corona.

Credit: NASA/Johns Hopkins APL/Naval Research Lab

In addition to dominating the commercial and consumer market, CMOS imagers have been used as engineering cameras to enable the entry, descent, and landing of NASA's Perseverance Mars rover, in the camera onboard the OCO-3 (Orbiting Carbon Observatory-3) mission that monitors the distribution of carbon dioxide on Earth, and as scientific imagers on NASA's Parker Solar Probe mission that is revolutionizing our understanding of the Sun. CMOS imagers are on their way to Jupiter’s moon, Europa, on the agency's Europa Clipper mission, and a delta-doped ultraviolet version with tailored response is under development for use on the upcoming UVEX (UltraViolet EXplorer) mission that will provide insight into how galaxies and stars evolve.

CMOS imagers are routinely used in monitoring the launch and deployment of CubeSats and SmallSats. They were recently used to monitor the deployment of Pandora, a small satellite that will characterize exoplanet atmospheres and their host stars; BLACKCAT (the Black Hole Coded Aperture Telescope), a small X-ray telescope; and the SPARCS (Star-Planet Activity Research CubeSat) mission designed to monitor and characterize the stellar flares of low-mass stars in ultraviolet to provide context for the habitability of exoplanets in their system. NASA is also developing descendants of this technology for use in missions that will search for life beyond Earth like its Habitable Worlds Observatory.

In recognition of the impact this CMOS technology has had, the National Academy of Engineering (NAE) has named Dr. Fossum the recipient of the 2026 Charles Stark Draper Prize for Engineering “for innovation, development, and commercialization of the complementary metal-oxide semiconductor (CMOS) active pixel image sensor ‘camera-on-a-chip.’” The NAE bestows this award biennially to honor an engineer “whose accomplishment has significantly impacted society by improving the quality of life, providing the ability to live freely and comfortably, and/or permitting the access to information.”

Sponsoring Organizations: The original efforts at JPL to develop this CMOS technology were funded by JPL and NASA.  

Source: Technology Originally Developed for Space Missions Now Integral to Everyday Life - NASA Science