Professor Shaun Quegan was awarded the NERC Economic Impact award on 3rd December for his work on the European Space Agency’s Biomass Satellite Mission. The instrument on Biomass will be built by Airbus UK.
Working out how much carbon is stored in forests using Earth observation satellites is difficult, because most of it is hidden from view by leaves in the forest canopy. Forests are clearly visible from space and satellites have been monitoring them for decades. But they give only a two-dimensional view of the area covered by leaves. The canopies hide the trunks and branches beneath, where the mass mostly resides. That makes an accurate measure of the total mass of wood a daunting task.
Shaun Quegan, National Centre for Earth Observation scientist and Professor of Mathematics at the University of Sheffield, however, was undaunted. And in four years, BIOMASS, the satellite he has been pushing for more than a decade, should change the way we view the Earth’s forests.
Once it is unfolded after launch, the satellite’s 12-metre antenna will act as three eyes in one, capable of measuring the mass in the world’s forests, the height of the trees, and the internal forest structure. It will also lead to better insight into rates of habitat loss and the impact that this has on biodiversity.
Particularly important, will be the ability to track forest degradation. If someone cuts down all the trees from a site, they leave scars that can be seen with conventional imaging, though we still wouldn’t be able to weigh them. On the other hand, if someone thins an area they can remove large quantities of living wood without leaving a visible mark.
With experience working on satellite missions, combined with 16 years building NERC-backed expertise through leading the multi-institution NERC Centre for Terrestrial Carbon Dynamics and later the carbon cycle theme of the National Centre for Earth Observation, Shaun has many of the skills needed to make the mission succeed.
At the centre of the mission is a radar using what the insiders call a P-band wavelength. These ‘Goldilocks’ waves are just right – not too long and not too short – allowing them to penetrate through the forest canopy and to reflect off the larger, woody mass beneath. They also don’t get too scrambled when passing through the ionosphere, a region of charged particles extending upwards from around 80km above the Earth’s surface.
As this is the radar band that early warning systems use to spot incoming missiles and track space debris, any space-borne P-band radar would blind those defensive capabilities. It was only in 2004 that international agreement was reached to allow P-band to be accessed by satellites for secondary use, where it does not conflict with the military.
These early warning systems are focused on the north, over the Atlantic and Arctic, so Shaun saw the opportunity to instead operate the satellite over the tropics, the critical and least understood region of the world’s forests. But the earlier ban meant there was no experience of using P-band radar in space. A trial system, AirSAR, flown on NASA planes in the early 1990s had shown the way; analysis of the data by Shaun and other researchers convinced them of the power of the technology. ESA has since funded further airborne campaigns that proved the technology over French Guiana, Gabon and Indonesia.
But this is a space-based mission, and that means BIOMASS has to peer through the interfering effects of charged particles in the ionosphere. Shaun established that, of the two key effects, one could be corrected, while the other could be avoided by putting BIOMASS in a special orbit, which crosses the equator at dawn and dusk when the ionosphere is at its most stable.
The Biomass mission should launch in 2020.