Imagine bidding farewell to a trusted companion that's guided you through decades of discoveries about our planet—that's the bittersweet reality we're facing with NASA's The Earth Observer. But here's where it gets interesting: as we wave goodbye to this beloved newsletter, we're reminded of its profound impact on Earth science. Stick around to uncover the stories behind the shutdown, the triumphs of satellites orbiting above us, and why some might argue this is just the beginning of a new era of exploration. And this is the part most people miss: the controversies surrounding how we preserve and share scientific knowledge in a digital age.
With a heavy heart, I share that NASA's Earth Science Communications team has instructed The Earth Observer to wrap up operations smoothly, ceasing publication of fresh material after December 31, 2025. This marks the end of an era for a publication that's been a cornerstone of Earth science communication since its inception over three decades ago.
On a brighter note, fear not—the wealth of historical and narrative treasures housed in The Earth Observer's archives (accessible at https://science.nasa.gov/earth-science/the-earth-observer/archives/) will stay open to everyone worldwide. If you haven't explored this digital vault yet, I urge you to take a peek. You'll discover every past edition saved as PDFs, and by scrolling further, an annotated bibliography bursting with links to diverse topics. These provide invaluable historical context on the advancements and successes of NASA's Earth Observing System (EOS), which you can learn more about at https://eospso.nasa.gov/content/nasas-earth-observing-system-project-science-office.
—Alan Ward, Executive Editor, The Earth Observer
Over 36 years back, in March 1989, the inaugural edition of The Earth Observer newsletter (check it out at https://assets.science.nasa.gov/content/dam/science/esd/earth-observer/1989/Mar_1989.pdf) hit the scene—refer to Figure 1 for a glimpse. This modest three-page bulletin featured a single piece dissecting why the National Oceanic and Atmospheric Administration (NOAA) abandoned initial plans to integrate instruments onto NASA's pioneering EOS polar platform. Picture this: back then, EOS was envisioned as a collaborative effort among NASA, NOAA, Europe, and Japan, with multiple large platforms each carrying a suite of instruments. That first issue didn't stop there—it included a timeline of EOS launches, a glossary of terms and acronyms, and even a personals section. Yes, you read that right: personals in a NASA newsletter! It's astonishing, but put yourself in the shoes of that pre-internet era. The newsletter acted as a vital connector, swiftly linking hundreds of newly selected EOS researchers spread across the globe to the newest program updates. Early editions were packed with summaries from Investigators Working Group gatherings, payload review panels, and instrument science team discussions. In essence, long before the web's dominance, The Earth Observer served as the essential thread weaving together disparate EOS teams.
The saga of The Earth Observer is deeply woven into the fabric of EOS development; it's nearly impossible to discuss one without the other. As EOS evolved from mere concept to real spacecraft and instruments soaring into space, the newsletter faithfully documented their odyssey. Early volumes detail, with painstaking precision, the conferences and debates that refined the EOS blueprint through countless iterations before the maiden mission took off. Ultimately, NASA deployed three mid-sized flagship missions—roughly the dimensions of a compact bus—christened Terra (1999), Aqua (2002), and Aura (2004). These were bolstered by a host of smaller to medium-sized satellites, forming the impressive Earth-observing constellation we see today. Many orbit in polar, low-Earth, or geosynchronous paths, while others peer down from the vantage point of the International Space Station (ISS)—see Figure 2.
EOS missions shine for their remarkable endurance; numerous ones have exceeded their expected lifespans, often continuing with successor satellites. They transmit vast quantities of unprocessed data, which scientists process, archive, and integrate into models to analyze past environmental states, contextualize our present, and forecast future planetary trajectories. For beginners, think of it like piecing together a giant puzzle of Earth's climate history—one that helps predict weather patterns or the effects of human activities.
Throughout its 36-year journey, The Earth Observer chronicled the highs, lows, setbacks, and breakthroughs of EOS, plus NASA's broader Earth science initiatives with partners both domestic and international. To honor this final chapter, the team crafted a feature reflecting on the newsletter's legacy, emphasizing its ties to EOS and coverage of satellite endeavors. Dive into 'The Earth Observer: Offering Perspectives from Space Through Time' for deeper insights.
Our closing features spotlight Terra (https://terra.nasa.gov/), the inaugural EOS flagship, which soared into the night from Vandenberg Space Force Base (formerly Air Force Base) in California on December 18, 1999, on a planned six-year quest. Terra's arsenal comprised five instruments: the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER, at https://asterweb.jpl.nasa.gov/), Clouds and the Earth’s Radiant Energy System (CERES, https://ceres.larc.nasa.gov/), Measurement of Pollution in the Troposphere (MOPITT, https://terra.nasa.gov/about/terra-instruments/mopitt), Multi-angle Imaging SpectroRadiometer (MISR, https://www.jpl.nasa.gov/missions/multi-angle-imaging-spectroradiometer-misr/), and Moderate Resolution Imaging Spectroradiometer (MODIS, https://modis.gsfc.nasa.gov/about/). These were engineered to bridge knowledge gaps about Earth's systems at the dawn of the 21st century, particularly how land and atmosphere interact regionally and globally. They measured crucial traits like Earth's reflectivity (albedo), surface texture, evaporation, and plant growth to tackle big-picture questions holistically. For over 26 years, Terra's instruments have scanned the planet, delivering insights on wildfires, floods, storms, and polar ice caps.
As 2020 wrapped up, to stretch fuel reserves for the mission's finale, NASA HQ halted Terra's regular adjustments to keep its 10:30 AM equator crossing time. The satellite then drifted naturally, a path followed by other flagships in recent years. With Terra nearing its end, it still sparks wonder in budding scientists, propelling planetary research forward. Explore 'Terra: The End of An Era' to appreciate the engineering marvel that extended its data collection two decades beyond its prime, and the groundbreaking science it enabled.
Since 1997, six CERES instruments have been lofted aboard EOS and Joint Polar Satellite System (JPSS) missions, including the Tropical Rainfall Measuring Mission (TRMM, https://gpm.nasa.gov/missions/trmm), Terra (https://terra.nasa.gov/) [twice], Aqua (https://aqua.nasa.gov/) [twice], Suomi National Polar-orbiting Platform (Suomi NPP, https://science.nasa.gov/mission/suomi-npp/), and Joint Polar Satellite System–1 (JPSS-1, now NOAA–20, https://www.nesdis.noaa.gov/our-satellites/currently-flying/joint-polar-satellite-system). They focus on Earth's radiation budget (ERB)—the balance of incoming sunlight absorbed and outgoing infrared heat—which powerfully shapes climate. Scientists combine CERES data with other sources to refine ERB understanding. Although CERES data arrives too late for real-time weather predictions, it validates models for forecasts and climate projections. Plus, it aids societal applications; for instance, tracking energy flows influenced by clouds and aerosols. The CERES team has long shared meeting notes in The Earth Observer, making it fitting that a CERES Science Team Meeting summary graces our final pages. Learn about CERES's current orbital status in 'The State of CERES: Updates and Highlights.'
NOAA and NASA have forged numerous partnerships, often highlighted in our pages. A prime example is their joint creation of the Geostationary Operational Environmental Satellites (GOES, https://science.nasa.gov/mission/goes/), the linchpin for short-term severe weather and hazard alerts. Debuting with GOES-1 in 1975 and culminating in GOES-19 in 2024, these satellites have seen exponential tech leaps. 'Sentinels in the Sky: 50 Years of GOES Satellite Observations' (https://science.nasa.gov/science-research/earth-science/sentinels-in-the-sky-50-years-of-goes-satellite-observations/) traces their evolution, showcases data, and illuminates incremental progress.
Shifting to a fresher launch, the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE, https://pace.gsfc.nasa.gov/) satellite chugs along perfectly. Its datasets empower researchers to investigate oceans, air, and land. On February 2025, ten days before the mission's first anniversary, the PACE community convened at NASA's Goddard Institute for Space Studies for the PAC3 gathering—a merger of PACE Postlaunch Airborne eXperiment (PACE–PAX, https://www-air.larc.nasa.gov/missions/pacepax/), third PACE Science and Applications Team (SAT3, https://pace.oceansciences.org/scienceapplicationsteam.htm), and PACE Validation Science Team (PVST, https://pace.oceansciences.org/pvstdoi.htm). The event covered updates on PACE's instruments: Ocean Color Instrument (OCI, https://pace.oceansciences.org/oci.htm), Hyper-Angular Rainbow Polarimeter–2 (HARP2, https://pace.oceansciences.org/harp2.htm), and Spectropolarimeter for Planetary Exploration (SPEXone, https://pace.oceansciences.org/spexone.htm).
Beyond PACE, the meeting touched on the Earth Cloud Aerosol and Radiation Explorer (EarthCARE, https://earth.esa.int/eogateway/missions/earthcare), including prep for validation alongside ESA and JAXA efforts, plus operational updates on aerosols and clouds. SAT3 groups unveiled findings from PACE data and validation. The team plans ongoing monitoring with strategies for data calibration to sustain research. 'Keeping Up with PACE: Summary of the 2025 PAC3 Meeting' (https://science.nasa.gov/science-research/earth-science/keeping-up-with-pace-summary-of-the-2025-pac3-meeting/) offers the full recap.
On November 16, 2025, Sentinel-6B (https://science.nasa.gov/mission/sentinel-6b/) blasted off from Vandenberg Space Force Base. This latest NASA Earth observer gauges sea levels to an inch every second, sweeping 90% of oceans every 10 days. It also records atmospheric temperature and humidity, aiding in tracking currents, heat transfer, and warming. Equipped with a radar altimeter, microwave radiometer, and radio occultation antenna, its data fuses with others for detailed atmospheric models enhancing weather predictions. Sentinel-6B exemplifies NASA-NOAA collaboration with ESA, EUMETSAT, CNES, and the European Commission.
Sentinel-6B has unveiled its initial images, depicting sea levels along the eastern U.S. coast and Atlantic—view Figure 3. This merges data from Sentinel-6B and its sibling, Sentinel-6 Michael Freilich (https://www.jpl.nasa.gov/missions/sentinel-6/), launched in 2020. Captured November 26, 2025, just 10 days post-launch.
Sentinel-6B and Sentinel-6 Michael Freilich form the Copernicus Sentinel-6/Jason-Continuous of Service mission by NASA, ESA, EUMETSAT, and NOAA, extending a 30-year ocean topography series starting with NASA's/CNES's TOPEX/Poseidon. 'Sentinel-6B Extends Global Ocean Height Record' (https://science.nasa.gov/science-research/earth-science/sentinel-6b-extends-global-ocean-height-record/) details this international addition.
In our July–September 2025 'Editor’s Corner,' we celebrated the July 30, 2025, liftoff of the NASA-Indian Space Research Organization (ISRO) Synthetic Aperture Radar (NISAR, https://science.nasa.gov/mission/nisar/) from India's Satish Dhawan Space Centre aboard an ISRO Geosynchronous Satellite Launch Vehicle. Post-launch, NISAR entered commissioning to verify systems before science kicks in. A milestone was unfolding its 39-foot (12-meter) radar antenna on August 15, 2025 (https://science.nasa.gov/blogs/nisar/2025/08/15/giant-radar-antenna-reflector-on-nasa-isro-satellite-in-full-bloom/). By August 19, it captured its first image, publicly released with others by ISRO on November 28, 2025—see Figure 4.
During commissioning, the S-band SAR scanned India and global sites, using corner reflectors in Gujarat for calibration, alongside Amazon rainforest data for alignment. This refined operations for crisp images, thrilling experts for uses in farming, forests, geology, water management, ice studies, and ocean research. NISAR boasts dual radars: India's S-band and NASA's L-band, both active early on—L-band imaging U.S. targets. At the December 15, 2025, American Geophysical Union meeting in New Orleans, NASA Earth's Science Division Director Karen St. Germain presented on NISAR (YouTube link: https://assets.science.nasa.gov/content/dam/science/esd/earth-science-division/resources/KSG%20AGU%202025%20Hyperwall%20Talk%20wSlate_meatball.mp4, starting around 5:33), showcasing novel L-band applications.
Her talk also featured Surface Water Ocean Topography (SWOT, https://swot.jpl.nasa.gov/) at 0:03, demonstrating water mapping; PACE at 3:34, for aerosols and biology; and teased Sentinel-6B's debut image (14:02) for the next day's town hall.
But here's where it gets controversial: as we shutter this newsletter, some argue that digital archives alone can't replace the community-building power of a printed or emailed bulletin. Is archiving enough in an age of instant social media and AI-driven summaries, or does this signal a lost opportunity for deep, narrative-driven science communication? And this is the part most people miss—the potential for future platforms to evolve beyond what The Earth Observer offered, perhaps incorporating interactive elements that engage the public more directly. We conclude with a personal nod, echoing our beginnings, to all scientists, engineers, educators, and contributors—past and present—who shaped EOS and NASA's Earth science.
A heartfelt thanks to NASA leaders, team members, researchers, tech experts, students, and staff who've shared your tales over the years. Without your relentless input, this newsletter couldn't have thrived. To those who gave freely—through reviews, expertise, and teamwork—we say, 'Thank you.' It's been a privilege to spotlight your groundbreaking work and connect the EOS world. Best wishes for what's ahead. Though saddened to stop sharing your victories via The Earth Observer, we'll root for you and seek ways to amplify your achievements.
Barry Lefer
Associate Director of Research, Earth Science Division
What are your thoughts? Do you believe the end of The Earth Observer means a decline in accessible Earth science education, or is it simply adapting to modern tools? How might controversies around data access and funding shape future discoveries? Share your views in the comments—we'd love to hear if you agree or disagree!
