Infrared thermo-vision image panorama of city, showing difference temperature

Binoculars in space: telescope to monitor energy output of buildings

Image credit: Ivansmuk/Dreamstime

A prototype space telescope, developed by researchers at the University of Cambridge, seeks to help monitor the energy efficiency of individual buildings.

Winter snowfall can reveal which homes are better insulated than others – but it’s an unreliable seasonal barometer. A radical plan to launch accurate thermal infrared telescopes into space to look back down at Earth could give a more accurate picture of where energy is leaking. This matters at a global level – buildings account for more than a quarter of greenhouse gas emissions on Earth. And this information could help hold governments, businesses, and individuals to account for climate goals – and spur them on to clean up their act.

This is the idea behind a project underway at the Institute of Astronomy at the University of Cambridge, where scientists are creating a prototype unfolding telescope that could continuously adjust itself in space and take high-resolution infrared thermal images to track energy emissions around the world for the first time.

“Technologically, it’s a challenge because of the physics,” says Dr Ian Parry, who’s more used to focusing on stars than back at Earth. A prototype telescope sits in his lab and his team are considering how it might withstand the rigours of launch into space. Any telescope has to be large enough to capture enough detail from a low Earth orbit and light enough to be affordable. “The greater the wavelength – and infrared has a longer wavelength than visible light – the larger the telescope required,” he says.

This wouldn’t be the first earth observation satellite to take thermal images of Earth, but it would provide the highest resolution to date – giving about 7m per pixel – enough to distinguish individual buildings, ships and other structures leaking warmth, according to the researchers. It would also be the first of its type that could continuously self-correct for accurate images, they added. “We get (thermal infrared images) free from Nasa, but definition is quite crude – 100m a pixel – so you can just about pick out a football field but nothing smaller.”

Earth observations are a powerful tool with which to analyse climate change. “To look at the thermal signature of individual buildings rather than just a blob – that’s a novel thing on a global scale,” says climate scientist Erik Mackie, engagement manager at Cambridge Zero which has been collaborating with Parry on the project. Buildings make up 23 per cent of total greenhouse gas emissions in the UK, and worldwide they’re responsible for 28 per cent (rising to 38 per cent if including emissions from the construction industry). An objective, accurate view would be useful – for governments and campaigners, he says.

In many ways, says Parry, the telescope, packed into a box about the size of a “crate of beer” – 22cm by 34cm, relies on old-fashioned mechanical engineering – but it must operate some 450km in space. Once in orbit, four mirrors at the base will unfold like drawbridges, while a red box containing the metrology system will rise on aluminium arms that extend like a firefighter’s ladder.

When unfolded, the telescope will measure 60cm wide and 1.1m long. “The problem is how to align the optics – they need to be put in place with the same accuracy as the wavelengths – to less than the width of a human hair,” says Parry. Traditionally, large telescopes of space have been correctly aligned before their launch. “They’re built to be sturdy enough to survive the launch, but putting an extremely big and heavy satellite into space is expensive. We’re trying to be clever to bring the costs down.”

To achieve the levels of accuracy required, Parry and his team have incorporated an internal measuring system. The position of light beams reflected back from the lower mirrors back to the top is fed into an onboard computer. Actuators fitted to each mirror then adjust and correct for errors – a first for space, says Parry. “The telescope will self-correct continuously and automatically and this won’t prevent it from collecting data at the same time.”

This will allow the delicate telescope to operate in extreme temperature changes of its low earth orbit, passing from cold night of -50°C to intense sunlight of up to 60°C. “This means it expands and contracts, which is why it must continually align itself.”

Nor will it be limited to capturing data only in the daytime – night infrared images are more revealing, says Parry. “In the dark, you don’t have the complication of disentangling what has been heated by the sun and what is emitted by heating systems – you get a cleaner signal.” And infrared is more weatherproof – it can pass through thin clouds to give some 30-50 per cent better coverage than optical wavelengths.

Currently, the project is a prototype sitting on Parry’s optical bench and he believes a prototype could be in space within two to three years. His is one of several projects funded by the UK Space Agency’s National Space Innovation Programme for businesses universities and research organisations.

But to achieve coverage of the world’s surface, a constellation of between 20 to 50 individual satellites – at an estimated £3m apiece – will be required, adding to a busy space zone where thousands of small satellites are already in orbit.

Still under consideration is the precise altitude – Parry favours some 450km above Earth – low enough for better resolution but potentially giving the satellite a longer life – ideally of around three years. He believes the best application will be to image the Earth 50 degrees on either side of the equator, across parts of the earth where most emissions occur.

And the tiny satellites could be welcomed by other sectors, says Parry. Infrared thermal images from space could be useful for industry and agriculture, for farmers to monitor crops, or oil companies to oversee expensive infrastructure and pipelines. Satellites are already used to monitor wildfires – infrared could add an extra layer of information.

At the same time, Parry is producing his prototype, Cambridge Zero is preparing to use its own buildings as a project testbed. A drone equipped with infrared thermal cameras will fly above university buildings to mimic images from a satellite – and cross-reference these with figures from university buildings’ energy usage – the university has already committed to cut greenhouse gas emissions to zero by 2038.

While the telescope might highlight individual culprits, it’s not designed to name and shame the public, says the team behind the project. But it could be a useful tool to flag poorly insulated properties – and direct government grants for better insulation. It could validate the certification of energy performance of buildings and reveal if they’re inaccurate.

“If we are serious as a country of reaching net-zero (carbon emissions) by 2050, these are the conversations we need to be having,” says Mackie. “We know how to reduce emissions – better insulation, and ideally to replace gas central heating. The energy system is hard to decarbonise but with the right incentives, we could make progress.”

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