Although we may not notice it in our everyday lives, eyes in space are always watching us and the environment we live in. Every day, they collect and transmit valuable data about oceans, forests, ice caps, urban expansion, and other features, both natural and artificial, of our planet. No, these are not aliens preparing to invade the earth, but rather spacecraft that orbit high above us, and later this week, they will gain a new asset in the form of the latest Earth-observation satellite, Landsat 9. We may not think much about them, but these satellites are indispensable for all on Earth, whether it be through daily weather forecasts or more long-term updates to the progression of climate change.
To some, the idea of exploring our planet from space might seem like an unnecessary endeavour. After all, we inhabit the Earth, and what better way is there to learn about a place than to actually travel around it? Well, the answer to this comes down to a matter of perspective.
By exploring Earth first-hand through research expeditions, we might be able to learn about the intricate details of an ecosystem, but we would also be missing out on a part of the bigger picture. Oftentimes, unravelling this bigger picture involves indirect observation methods that utilize different perspectives. This idea, called remote sensing, or gathering information from an object without actually coming into contact with it, had its roots in the development of aerial photography, first experimented with in the late 19th century. Early images were practically unusable for map-making purposes, but by the early 20th century it was possible to produce relatively clear pictures that had both scientific and military value. This new technology found one of its first uses in the First World War, when aerial reconnaissance played a key role in strategic planning. Advanced reconnaissance aircraft used in the Cold War took the idea of remote sensing to a whole new level by using sheer altitude and speed to capture large swaths of land in short amounts of time.
To some, the idea of exploring our planet from space might seem like an unnecessary endeavour. After all, we inhabit the Earth, and what better way is there to learn about a place than to actually travel around it? Well, the answer to this comes down to a matter of perspective.
By exploring Earth first-hand through research expeditions, we might be able to learn about the intricate details of an ecosystem, but we would also be missing out on a part of the bigger picture. Oftentimes, unravelling this bigger picture involves indirect observation methods that utilize different perspectives. This idea, called remote sensing, or gathering information from an object without actually coming into contact with it, had its roots in the development of aerial photography, first experimented with in the late 19th century. Early images were practically unusable for map-making purposes, but by the early 20th century it was possible to produce relatively clear pictures that had both scientific and military value. This new technology found one of its first uses in the First World War, when aerial reconnaissance played a key role in strategic planning. Advanced reconnaissance aircraft used in the Cold War took the idea of remote sensing to a whole new level by using sheer altitude and speed to capture large swaths of land in short amounts of time.
However, aerial photography had its limits. For one, flights could only operate for short amounts of time, meaning it was difficult, if not impossible, to judge changes to the landscape over longer periods. Additionally, airborne missions used for reconnaissance purposes were dangerous to the pilots who put their lives on the line. To mitigate these issues, military leaders began looking into putting cameras into space, where they would be able to operate for extended periods of time without putting humans in danger. The first satellites dedicated solely to Earth-observation were those of the American CORONA program, which began in the 1950s under the codename of Discoverer. While this particular program was tasked with spying on the Soviet Union and other foreign countries, it also paved the way for a new generation of observation satellites.
By the late 1950s, scientists who noticed the successes of space-based reconnaissance began to consider a more civil use for satellite observation technologies: weather forecasting. TIROS-1, the first dedicated weather satellite, was launched by NASA in 1960, and it didn’t take long for other countries, like the Soviet Union, to recognize the value of this new method of forecasting.
The roots of what is now called the Landsat program, one of the most well-known and successful Earth-observation programs, can be traced back to the 1960s, not long after the launch of TIROS-1. There was no doubt at the time that data from weather satellites was extremely valuable, but the idea of applying the same technology towards terrain monitoring was met with skepticism until the middle of the decade, when a proposal to use satellites to gather information about Earth’s natural resources was put forward by the US Geological Survey (USGS). Still, fears that such a program would compromise the secrecy of reconnaissance satellites remained. To complicate the matter further, questions were raised about the geopolitical consequences of photographing foreign countries, and consequently, it took until 1970 for NASA and the USGS to gain authorization to build the first Earth Resources Technology Satellite, which was later renamed Landsat 1.
In the years following the 1972 launch of Landsat 1, plans were developed to add more satellites to the program; Landsat 2 was launched in 1975, and Landsat 3 followed not long after in 1978. The combined achievements of these first few missions led to the creation of even more satellites, and 50 years later, it is safe to say that the collaboration between NASA and the USGS has produced one of the most successful programs in the history of space exploration. The Landsat program has become the longest-running satellite imagery operation in history, and it is still going strong today as Landsats 7 and 8 are still in service. With new and upgraded sensors and cameras, Landsat-9 will soon join the ranks of the hundreds of Earth-observation satellites in orbit and carry the Landsat program through the next decade.
Images from satellites such as those from the Landsat program are incredibly detailed, with the new cameras on Landsat 9 being able to resolve objects as small as 15 meters. Despite the almost military-grade image quality, however, these images are free to use by anyone, meaning both professional and citizen scientists can contribute to our ever-expanding knowledge about Earth. Furthermore, by offering a unique vantage point, Earth-observation satellites can collect data from remote locations and track the movement of weather patterns around the globe. The value of this was displayed during the recent eruption of the Cumbre Vieja volcano when satellites provided critical information on the movement of a massive ash cloud generated by the eruption. Additionally, because satellites remain in orbit for many years and pass over the same areas hundreds of times during their missions, scientists can observe long-term changes to the landscape. For instance, the Landsat program has been keeping track of deforestation in the Amazon rainforest, ICESat-2 has monitored polar ice thickness, Sentinel-6 has kept track of sea levels, and countless other satellites have recorded other phenomena associated with climate change. And for those living in areas where natural disasters like hurricanes happen frequently, satellites play an even greater role as accurate weather forecasting can often make the difference between life and death.
Perhaps most importantly, the data from remote-sensing satellites can be used to build a picture of our planet’s future. Over the last couple of decades, they have played an instrumental role in monitoring climate change through data collected on extreme weather events, glacial melt, and greenhouse gas emissions, and this data can be used to make predictions about what might happen if these processes continue unchecked. However, we can also use this information to find innovative ways to slow the progression of climate change. As such, Earth-observing satellites don’t just show us the problem; they can also show us the solution.
Since its humble beginnings in aerial photography, and not-so-humble beginnings in the ashes of war, Earth-observation satellites have become an integral part of how we live and plan out our everyday lives. Many things that impact our day to day lives, from weather forecasting to the latest climate data, are only available to us because of these remarkable satellites, and with the upcoming launch of Landsat 9, there is no doubt space-based Earth observation will continue to play an instrumental role in society for decades to come. You could even say that the most important work being done in space is not about the stars or Mars, but rather our home planet.
Sources & Further Reading
History of Earth observation satellites
Landsat 9
NASA Earth Observatory