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There are satellites that flash briefly across the sky and then fade into history, and there are satellites that quietly build a legacy measured not in months, but in generations. The Landsat program belongs firmly to the latter. Since 1972, when the first Landsat spacecraft began circling Earth, the mission has carried forward a simple but transformative idea: that if we observe our planet consistently, patiently, and scientifically, we can understand how it changes—and why.

Landsat was born during a time when space exploration was dominated by lunar ambitions and planetary probes. Yet a handful of scientists and engineers recognized that one of the most important frontiers lay much closer to home. The Earth itself was changing under the pressure of agriculture, urban expansion, deforestation, water use, and climate variability. The Landsat program was designed to provide something unprecedented: a continuous, calibrated, and publicly available record of the planet’s land surface.

From the beginning, the mission’s goals were ambitious. Landsat satellites were built to measure reflected sunlight and emitted thermal radiation from Earth’s surface across multiple wavelengths. This spectral approach allowed scientists to distinguish forests from croplands, healthy vegetation from drought-stressed fields, snow from clouds, and sediment-rich rivers from clear lakes. By observing the same locations again and again over decades, Landsat turned snapshots into time series, revealing patterns that would otherwise remain invisible.

The engineering behind Landsat is a study in precision. Each spacecraft travels in a near-polar, sun-synchronous orbit at an altitude of roughly 700 kilometers. This orbit ensures that the satellite passes over any given location at approximately the same local solar time, maintaining consistent lighting conditions for imaging. Stability and repeatability are paramount. The sensors must be radiometrically calibrated to detect subtle changes in surface reflectance over time. A difference of just a few percent in measured brightness can signal shifts in vegetation health or soil moisture.

Over successive missions, Landsat’s instruments evolved. Early satellites relied on the Multispectral Scanner (MSS), which offered groundbreaking though relatively coarse imagery. Later generations introduced the Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+), expanding spectral coverage and spatial resolution. With Landsat 8, launched in 2013, the program entered a new era of digital precision with two primary instruments: the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). Together, they extended the spectral range, improved signal-to-noise performance, and ensured compatibility with the historical data record.

The continuity of the Landsat archive is not an accident—it is a design philosophy. Every new satellite must be cross-calibrated against its predecessor so that the global dataset remains scientifically consistent. This continuity has allowed researchers to track deforestation in the Amazon, glacier retreat in Greenland, urban expansion in Asia, and agricultural water use in the American West. Landsat’s data policy, which made imagery freely available starting in 2008, transformed global access to Earth observation, catalyzing research, commercial innovation, and environmental monitoring on a planetary scale.

It is within this lineage that Landsat 9 emerged.

Launched on September 27, 2021, from Vandenberg Space Force Base aboard an Atlas V rocket, Landsat 9 was not conceived as a revolution, but as a promise kept. Its mission was to ensure that the Landsat record—now spanning more than half a century—would continue without interruption. Developed by NASA and operated jointly by NASA and the U.S. Geological Survey (USGS), Landsat 9 carries forward the twin-instrument architecture pioneered by Landsat 8, with refined performance and improved reliability.

At the heart of Landsat 9 is the Operational Land Imager 2 (OLI-2), an advanced multispectral sensor that captures reflected sunlight across visible, near-infrared, and shortwave infrared wavelengths. These spectral bands are carefully chosen to reveal the chemical and structural properties of land surfaces. Vegetation reflects strongly in the near-infrared; water absorbs much of it. Soils, minerals, and built environments each leave distinct spectral signatures. By measuring these patterns, OLI-2 allows scientists to compute vegetation indices, monitor crop productivity, detect wildfire scars, and assess coastal health.

Complementing OLI-2 is the Thermal Infrared Sensor 2 (TIRS-2), which measures land surface temperature. Thermal data are essential for understanding evapotranspiration, drought conditions, urban heat islands, and volcanic activity. Land surface temperature is not merely a climate statistic; it is a dynamic variable that shapes ecosystems, agriculture, and human comfort. TIRS-2 improves upon earlier thermal sensors with better stray-light control and enhanced calibration, strengthening confidence in long-term temperature records.

Together, OLI-2 and TIRS-2 produce imagery with a spatial resolution of 30 meters for most bands and 100 meters for thermal measurements, revisiting the same location every 16 days. When combined with Landsat 8, the effective revisit time drops to eight days, increasing temporal coverage and reducing data gaps caused by cloud cover.

The engineering sophistication of Landsat 9 extends beyond its instruments. The spacecraft platform was built by Northrop Grumman and designed for durability and efficiency, with redundant systems and precise attitude control to maintain stable pointing. The satellite continuously transmits data to ground stations, where it is processed, calibrated, and archived by the USGS. Each image enters a public repository that now contains millions of scenes—a living chronicle of Earth’s surface.

Perhaps the most remarkable aspect of Landsat 9 is how unremarkable it strives to be. Its purpose is not spectacle, but continuity. It does not chase novelty; it protects consistency. In an era of rapid technological turnover, Landsat 9 embodies a different ethos: that sustained observation is as important as innovation.

As climate change accelerates, water resources tighten, and urban populations grow, the need for objective, long-term data becomes ever more urgent. Landsat 9 contributes to this global awareness by quietly collecting photons reflected and emitted from Earth’s surface, converting them into calibrated digital records. These records feed into agricultural planning, disaster response, forest management, and climate science.

The Landsat program began as an experiment in seeing our planet from above. Over five decades, it has become a foundational instrument for understanding it. Landsat 9 stands as the latest steward of that legacy—a spacecraft designed not just to observe the Earth, but to ensure that future generations can compare their world to the one we see today.

In that sense, Landsat 9 is more than a satellite. It is a continuation of a conversation between humanity and its home, a steady voice reminding us that change is measurable, and therefore knowable.

Video credit: NASA Goddard

Mea AI adiutor dicit:

Launched on April 15, 1999, from Vandenberg Air Force Base in California aboard a Delta II rocket, Landsat 7 marked a new chapter in Earth observation. This satellite, a collaborative endeavor between NASA, the U.S. Geological Survey (USGS), and NOAA, was the seventh in the long-running Landsat program that began in 1972. With a sun-synchronous, near-polar orbit at an altitude of approximately 705 kilometers, Landsat 7 was designed to pass over the same part of the Earth every 16 days, capturing high-resolution imagery under consistent lighting conditions at around 10:00 a.m. local solar time.

The spacecraft itself was engineered by Lockheed Martin and featured a three-axis stabilized platform, which allowed precise orientation in space. It drew power from solar arrays supported by nickel-cadmium batteries and used a hydrazine monopropellant system for orbital maintenance. One of its significant upgrades over previous Landsat missions was the inclusion of a solid-state data recorder capable of storing roughly 378 gigabits of data. This feature allowed the satellite to store imagery until it could downlink it to a ground station, enabling more flexible operations and broader global coverage.

At the heart of Landsat 7’s success was its sole scientific instrument: the Enhanced Thematic Mapper Plus (ETM+). This powerful sensor was a “whisk-broom” scanner, capturing data across eight spectral bands. Six of these bands covered the visible, near-infrared, and shortwave infrared portions of the electromagnetic spectrum with a resolution of 30 meters. A thermal infrared band operated at 60 meters resolution, while a high-resolution panchromatic band offered detail at 15 meters. Each scene covered an area of roughly 183 by 170 kilometers.

One of ETM+’s distinguishing features was its rigorous calibration. Equipped with a full-aperture solar calibrator and internal lamps, ETM+ maintained its radiometric accuracy to within five percent. This exceptional calibration made it the gold standard for satellite remote sensing, enabling cross-calibration with other Earth-observing missions such as NASA’s Terra and EO-1 satellites.

However, Landsat 7’s mission was not without challenges. On May 31, 2003, the satellite’s scan line corrector (SLC)—a mechanism that compensated for the motion of the satellite to ensure complete image coverage—failed. This hardware malfunction introduced zigzag-shaped data gaps that affected roughly 22 to 30 percent of each image. Despite the setback, Landsat 7 continued to operate, and the data it captured remained valuable. Scientists developed methods to fill in the gaps using data from adjacent passes, allowing continued scientific use and analysis.

Originally designed for a five-year mission, Landsat 7 exceeded expectations by remaining active for over two decades. In 2017, the final station-keeping maneuvers were performed to maintain the satellite’s orbital parameters. As fuel levels dropped, the satellite’s orbit began to drift slightly, but its imaging capabilities remained intact. In April 2022, the satellite was placed in a lower orbit to support calibration of other Earth-observing systems, and it continued to acquire data intermittently until January 2024. On June 4, 2025, the mission officially came to an end.

Throughout its operational life, Landsat 7 played a vital role in Earth sciences. It provided consistent, high-resolution imagery that supported a wide range of applications, including environmental monitoring, land use planning, disaster response, water resource management, agriculture, and climate change research. The data collected were used in studies that tracked deforestation in the Amazon, urban sprawl in North America, and agricultural patterns in sub-Saharan Africa, among countless other projects.

One of Landsat 7’s most transformative impacts came in 2008, when USGS made its entire Landsat archive—including Landsat 7 data—available to the public at no cost. This decision revolutionized the field of remote sensing, opening the doors to researchers, educators, governments, and businesses worldwide. The number of Landsat scene downloads skyrocketed, leading to an explosion in published scientific studies and practical applications.

Beyond its imagery, Landsat 7 served as a radiometric benchmark. Its ETM+ sensor was so well-calibrated that it became a reference instrument, helping to ensure consistency and accuracy across other satellite missions. This legacy continued with Landsat 8, launched in 2013, and Landsat 9, which entered service in 2021. Even in its final years, Landsat 7 contributed to efforts to standardize Earth observation through proposed servicing missions and calibration support.

Landsat 7’s mission may have ended, but its legacy endures. For over 20 years, it provided humanity with a clearer picture of our changing planet, setting new standards in satellite imaging and democratizing access to Earth observation data. As scientists and decision-makers confront the challenges of climate change, food security, and sustainable development, the insights first captured by Landsat 7 continue to inform policy and shape our understanding of the world.

Video credit: NASA Goddard

NASA dicit:

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

Wikipedia dicit:

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.

Credit: NASA Goddard

NASA dicit:

Landsat 9 is the latest satellite to continue the legacy of global observations of Earth’s land surface. With unmatched longevity, accuracy, and coverage, the Landsat program has been the cornerstone of global land imaging since 1972. Landsat 9 continues this tradition, and will carry us into the next 50 years of Earth observations. The two instruments aboard will make the most advanced measurements of any Landsat satellite.

Design and construction of the spacecraft and its instruments is managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and operation and archiving of the data is managed by the U.S. Geological Survey. Goddard and Ball Aerospace each built one of the instruments, and the spacecraft was built by Northrop Grumman.

The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey (USGS). Landsat satellites have been consistently gathering data about our planet since 1972. They continue to improve and expand this unparalleled record of Earth’s changing landscapes for the benefit of all.

Video credit: NASA’s Goddard Space Flight Center/Matthew R. Radcliff (USRA): Lead Producer/Aaron E. Lepsch (ADNET): Technical Support/Matthew R. Radcliff (USRA): Editor/Matthew R. Radcliff (USRA): Narrator/Kate Ramsayer: Writer/Jeffrey Masek (NASA/GSFC): Scientist/Music Marble Place by Matias Suescun [SACEM], published by KTSA Publishing [SACEM], available from Universal Production Music

Wikipedia dixit:

“The Landsat program is the longest-running enterprise for acquisition of satellite imagery of Earth. On July 23, 1972 the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat. The most recent, Landsat 8, was launched on February 11, 2013. The instruments on the Landsat satellites have acquired millions of images. The images, archived in the United States and at Landsat receiving stations around the world, are a unique resource for global change research and applications in agriculture, cartography, geology, forestry, regional planning, surveillance and education, and can be viewed through the U.S. Geological Survey (USGS) ‘EarthExplorer’ website. Landsat 7 data has eight spectral bands with spatial resolutions ranging from 15 to 60 meters; the temporal resolution is 16 days. Landsat images are usually divided into scenes for easy downloading. Each Landsat scene is about 115 miles long and 115 miles wide (or 100 nautical miles long and 100 nautical miles wide, or 185 kilometers long and 185 kilometers wide).

[…] Landsat missions 1 through 5 carried the Landsat Multispectral Scanner (MSS), while missions 4 and 5 used the Landsat Thematic Mapper (TM) scanner. The Multispectral Scanner had a 230 mm (9 in) fused silica dinner-plate mirror epoxy bonded to three invar tangent bars mounted to base of a Ni/Au brazed Invar frame in a Serrurier truss that was arranged with four “Hobbs-Links” (conceived by Dr. Gregg Hobbs), crossing at mid-truss. This construct ensured the secondary mirror would simply oscillate about the primary optic axis to maintain focus despite vibration inherent from the 360 mm (14 in) beryllium scan mirror. This engineering solution allowed the United States to develop LANDSAT at least five years ahead of the French SPOT, which first used CCD arrays to stare without need for a scanner. However, LANDSAT data prices climbed from $250 per computer compatible data tape and $10 for black-and-white print to $4,400 for data tape and $2,700 for black-and-white print by 1984, making SPOT data a much more affordable option for satellite imaging data. This was a direct result of the commercialization efforts begun under the Carter administration, though finally completed under the Reagan administration.

The MSS FPA, or Focal Plane Array consisted of 24 square optical fibers extruded down to 0.005 mm (0.0002 in) square fiber tips in a 4×6 array to be scanned across the Nimbus spacecraft path in a ±6 degree scan as the satellite was in a 1.5 hour polar orbit, hence it was launched from Vandenberg Air Force Base. The fiber optic bundle was embedded in a fiber optic plate to be terminated at a relay optic device that transmitted fiber end signal on into six photodiodes and 18 photomultiplier tubes that were arrayed across a 7.6 mm (0.30 in) thick aluminum tool plate, with sensor weight balanced vs the 230 mm telescope on opposite side. This main plate was assembled on a frame, then attached to the silver-loaded magnesium housing with helicoil fasteners.

Key to the success of the multi spectral scanner was the scan monitor mounted on the underbelly of the magnesium housing. It consisted of a diode light source and a sensor mounted at the ends of four flat mirrors that were tilted so that it took 14 bounces for a beam to reflect the length of the three mirrors from source to sender. The beam struck the beryllium scan mirror seven times as it reflected seven times off the flat mirrors. The beam only sensed three positions, being both ends of scan and the mid scan, but by interpolating between these positions that was all that was required to determine where the multi spectral scanner was pointed. Using the scan monitor information the scanning data could be calibrated to display correctly on a map.”

Video credit: NASA Goddard