Monitoring Global Forests: The Functionality of the ESA's Biomass Mission

The European Space Agency (ESA) is preparing to launch its ambitious Biomass mission later this month.

This mission aims to create a comprehensive global map of the world's forests, providing the first extensive measurements of forest biomass. It will investigate how forests are evolving and enhance our understanding of their role within the carbon cycle.

The satellite is scheduled for launch on April 29 aboard a Vega C rocket from ESA’s spaceport in Kourou, French Guiana. It will be positioned in a sun-synchronous orbit, ensuring it maintains a consistent position relative to the sun, at an altitude of approximately 666 kilometers.

What are the objectives of the Biomass mission?

All life on Earth, from the tiniest microbes to the towering California Redwoods, is fundamentally carbon-based. Carbon is the essential element that enables life as we know it. However, the Earth does not gain or lose carbon; instead, it circulates among the atmosphere, living organisms, the Earth's crust and soil, and the oceans.

This circulation is referred to as the carbon cycle, in which forests play a crucial role. Forests sequester significant amounts of carbon, with scientists estimating that they absorb around 16 billion metric tonnes of carbon dioxide (CO2) annually and currently store 861 gigatonnes of carbon within their soils and vegetation.

Regrettably, global data on forest biomass—the total mass of organic matter in forests—are severely inadequate. This lack of information hinders our understanding of forest conditions and their influence on the carbon cycle and climate.

The Biomass mission seeks to address this knowledge deficiency. It will enable scientists to more precisely assess how carbon distribution on the planet is changing as deforestation continues and atmospheric CO2 levels rise.

In 2023, the Earth experienced a loss of 3.7 million hectares of tropical forests, which is equivalent to losing about ten football fields of forest land every minute, according to a report from the World Resources Institute.

Simonetta Cheli, the director of Earth Observation Programmes at the European Space Agency (ESA), stated in an interview with The Observer, “Understanding the health of our tropical forests is essential… We must assess the quality and diversity of their vegetation, as well as the carbon stored within them. To obtain this data, we will create three-dimensional images that capture everything from the forest canopy down to the roots of the trees.”

In addition to monitoring forests, the Biomass mission will track the movement of ice sheets in Antarctica and produce digital models of areas covered by thick vegetation.

How will the Biomass mission monitor forests?

To achieve its goals, the mission will employ synthetic aperture radar (SAR) technology to map the Earth's surface. Significantly, the satellite will be equipped with a large 12-meter antenna and will be the first in space to utilize a long-wave P-band SAR.

This capability will allow it to penetrate dense forest canopies, enabling the assessment of carbon stored on the forest floor and within the tree branches, as well as tracking changes in these levels over time. It is important to note that, generally, shorter wavelengths of electromagnetic radiation are less effective at penetrating materials compared to longer wavelengths.

Shaun Quegan, a researcher at the University of Sheffield and the head of the Biomass science team, remarked to The Guardian: “Essentially, the mission will quantify the weight of the forests it examines… We understand that half of that weight is composed of carbon. Therefore, we will be able to measure the carbon content of the world’s forests from space and, importantly, determine how these levels are changing over time. This will provide us with crucial insights into the carbon balance between the atmosphere and the forests, which is of immense significance.”