The radar image of the tropical rainforest area in Bolivia captured by the Biomass satellite launched by the European Space Agency (ESA) at the end of April is shown. This satellite is equipped with a Synthetic Aperture Radar (SAR) that synthesizes the electromagnetic waves reflected from the ground into a single image. The satellite orbits at an altitude of 666 km and travels at a speed of 7.5 km per second, capturing an area measuring 90 km in length and 60 km in width.
Each color represents distinct features of the terrain. Green indicates tropical rainforests, red denotes floodplains and wetlands, cyan signifies grasslands, and black represents rivers and lakes. The right side of the image indicates north. Based on this, it can be seen that a significant portion of the northern region has converted into grassland. Bolivia's tropical rainforest has recently been suffering from severe illegal deforestation. Trees and shrubs that had flourished around rivers and wetlands for thousands of years have vanished due to human greed in just a few years.
During the Living Planet Symposium held in Vienna, Austria, from June 23 to 27, ESA unveiled the first images captured by the Biomass satellite, garnering applause from scientists and environmental experts around the world for the incredible scenes captured globally. At the event, ESA explained, 'The successful launch of the Biomass satellite has made significant progress in our ability to understand how the forests of the Earth are changing and how they contribute to the Earth's carbon cycle.'
Held every three years, this event is considered one of the premier events in Earth observation. This year's theme was 'Climate Action and Transition to Earth Sustainability.' Accordingly, the images captured by the Biomass satellite, which was launched on April 29 from the Guiana Space Centre in French Guiana aboard the Vega C rocket, drew the most attention.
The Biomass satellite was developed to collect comprehensive information about the carbon absorption capacity of forests and mountains worldwide. Forests, often referred to as 'the green lungs of the Earth,' absorb approximately 8 billion tons of carbon dioxide from the atmosphere each year. However, illegal logging and degradation in tropical regions are exacerbating climate change by releasing carbon back into the atmosphere. Scientists believe that it is essential to continuously monitor the precise conditions of forests.
The Biomass satellite is equipped with P-band SAR. The SAR is also installed on Korea's multipurpose practical satellite, Arirang 5, and utilizes various frequency bands. The P-band has the longest wavelength among them. Longer wavelengths can penetrate beneath the surface, making it useful for studying terrestrial plants and soils. The P-band SAR analyzes the surface characteristics through images obtained from four combinations of horizontal and vertical electromagnetic waves. The images are displayed in red, green, and blue (RGB) according to the surface objects.
Experts believe that the photographs taken by the Biomass satellite will serve as a significant milestone in understanding how the Earth stores carbon and how climate change alters ecosystems, especially in identifying changes in the carbon storage amount within forests.
ESA evaluated that the Biomass satellite showed sufficient potential just two months after its launch. Although it is still in the testing phase, they stated that initial images sufficiently demonstrated its performance. ESA released images of the Earth's forests, deserts, and glaciers captured by the Biomass satellite during May and June.
◇Tropical rainforest and Beni River in Bolivia
The strengths of the Biomass satellite are clearly evidenced when compared to optical satellite images. At first glance, the photos taken by the Biomass satellite and those captured by ESA's optical satellite, Copernicus Sentinel-2, appear similar. However, the images from the Biomass satellite provide much more information regarding the carbon storage capacity of forests.
In reality, the Sentinel-2 satellite photos only show the canopy of the forest. In contrast, the Biomass satellite's capability lies in unveiling biomass according to height. This is made possible by the long-wavelength radar that penetrates the canopy to reveal the overall structure of the forests. The Biomass satellite also provides essential three-dimensional (3D) structures of forests needed for accurate carbon calculations. Scientists believe that this method enhances the accuracy of estimating the carbon storage of forests and understanding the role of tropical rainforests in the Earth's carbon cycle.
◇Northern Amazon rainforest in Brazil
The Biomass satellite captured its first images on May 22 while flying at an altitude of 666 km over the northern Amazon rainforest in Brazil. The pink and red areas in the image represent wetlands. This indicates that the Biomass satellite has the capability to detect down to the forest floor through dense vegetation.
The prominent red areas along the river indicate a floodplain formed by sediment buildup when the river overflowed during floods. Conversely, the dark green regions depicted in the north reveal dense forests that are rugged and richly populated with NAMUGA.
◇Volcanic tropical rainforest on Halmahera Island, Indonesia
The tropical rainforest landscapes in the Indonesian islands have also been revealed. Indonesian forests are threatened by deforestation, habitat loss, and increased carbon emissions due to the rise of timber coal power plants and increased exports of wood pellets.
The revealed region is the tropical rainforest on Halmahera, the largest island in the northern Maluku Islands of Indonesia, characterized by a mountainous terrain formed by volcanic activity. The island features a total of 16 volcanoes, including five active ones. The mountain Gamkonora can be seen near the northern coast.
The radar of the Biomass satellite captured the outlines of the volcano and the surrounding forest terrain. The radar's electromagnetic waves can penetrate through dense underbrush to reveal terrain characteristics. This satellite serves as a prime example of the capability to map both biomass and terrain.
◇Forest and Ivindo River in Gabon
The Biomass satellite captured this scene of tropical rainforest over Ivindo National Park in Gabon, Africa, near the equator. The Ivindo River is prominently visible at the center of the photo. Aside from the river and its tributaries, the image predominantly displays shades of green, indicating dense forests.
The radar electromagnetic waves pass through the branches and leaves of the forest, distinctly revealing the terrain features. The satellite captured an area measuring approximately 100 km in length and 60 km in width while flying in a space orbit.
◇Structures under the Sahara Desert in Chad
P-band radar can penetrate up to 5 m below the surface of the desert, allowing for exploration of ancient riverbeds and geological structures buried beneath dry terrains.
The Biomass satellite photographed buried structures hidden beneath the sand while flying over the Sahara Desert in Central Africa, Chad, in May. This image captures a region measuring 100 km wide and 60 km long, including parts of the Tibesti mountain range, the northernmost mountains of the Sahara.
Scientists hope that the P-band radar will help in understanding past climates and exploring fossil water resources in desert areas.
◇Nimrod Glacier crossing the Transantarctic Mountains
ESA revealed the frozen landscapes of the Antarctic continent as the final image from the Biomass satellite. The photo depicts the Nimrod Glacier flowing into Ross Ice Shelf along the Transantarctic Mountains.
The 0.7 m wavelength emitted by the P-band radar allows for viewing inside the ice and tracking glacier structures and flow rates. Experts believe it will provide essential data on glacier dynamics and stability needed to understand sea level rise in the age of global warming.
◇Earth's carbon cycle: enhancing accuracy of carbon absorption and emission
The P-band radar mounted on the Biomass satellite was developed by Airbus Defense and Space, while the satellite's symbol, a 12 m diameter umbrella antenna, was developed by the American company L3Harris. About a week after the satellite was launched, on May 7, an event unfolded in orbit where this umbrella antenna unfurled.
ESA is conducting demonstrations on-site to obtain accurate measurements of carbon absorption in forests. P-band radar alone cannot directly measure biomass values in forests. In the case of tropical rainforests, where plant species and ecosystem diversity are so vast that categorization from space is challenging, ground verification is essential. Instead, on-site experts use values measured from tree samples as proxy indicators to estimate carbon storage.
In practice, forest scientists, botanists, and technicians are measuring biomass values, such as the thickness and height of tree trunks, in various locations worldwide, including Brazil, Peru, and Colombia, to accurately measure the amount of carbon stored in trees. The branches and trunks are where the most carbon is stored.
Olive Phillips, a professor at the University of Leeds in the UK, noted, 'There are more than 10,000 species of NAMUGA in the Amazon,' and emphasized that 'even the most advanced satellites technologically cannot distinguish between mahogany and Brazil nut trees without help from the ground.'
Scientists say that the launch of the Biomass satellite marks the beginning of a new 'Forest Space Era.' ESA noted that there has never been such a significant number of 'eyes in the sky' focused on forests that have either entered space orbit or will be launched soon.
In addition to the Biomass satellite, devices such as GEDI (Global Ecosystem Dynamics Investigation), a laser radar operated by the National Aeronautics and Space Administration (NASA) from the International Space Station (ISS), NISAR, a SAR device jointly operated by NASA and the Indian Space Research Organisation (ISRO), Copernicus Sentinel-1, another ESA satellite, and Advanced Land Observing Satellite (ALOS), a phased array radar satellite by the Japan Aerospace Exploration Agency (JAXA), are either operational or set to launch.
ESA aims to create three-dimensional (3D) maps of global forests and develop five global maps estimating forest heights and terrestrial biomass over the next five years. This is expected to significantly enhance understanding of carbon storage, forest health, and temporal changes in forest ecosystems.
The scientific community anticipates that this will lead to significant progress in understanding how Earth's forests are changing and contributing to the carbon cycle. Providing consistent information on global forest areas is expected to give crucial data for climate model development and assessing corporations based on greenhouse gas emissions and reductions.