The ‘Big Data’ era of space
There is certainly no shortage of data from satellites. Earth observation sensors will soon deliver over 1,000 times more data than those early satellites, as there are now hundreds of them in orbit and the resolution of their measurements is now higher.
What’s more, this glut of data is increasingly being made open access. For example, Europe’s flagship EO programme, Copernicus, is the largest of its kind in the world and will provide all of its environmental data for anybody to use, for free.
In recognition of the opportunity that this brings, the UK government launched the ‘Space for Smarter Government’ programme in 2014. It aims to ensure that space-based data is used effectively across government, whilst stimulating innovation and saving money in the process.
A need for quality and quantity
When it comes to monitoring climate change, quality matters as much as quantity. Large capital decisions made by governments on adapting to climate change are based on climate model projections. These combine satellite observations of many global climatic variables, measured over many years, to quantify long-term human-induced signals of climate change against the day-to-day ‘noise’ of weather.
By making the data that goes into these climate models more accurate, the resulting model predictions improve. Better forecasts will enable more robust and timely decisions to be made on adapting to climate change, helping to reduce its future economic and societal impact.
Improving the accuracy of EO data
Satellites are already impressively accurate considering the journey each one takes to get into orbit. The precision instruments on-board a rocket are subject to intense vibrations and g-forces. Once in space, satellites are bombarded with solar radiation and extreme temperatures, and make their measurements hundreds of kilometres from Earth and at speeds of nearly 8 kilometres per second.
Despite these conditions, satellites deliver data with uncertainties of only a few percent. Still, the more those uncertainties are reduced, the quicker we can see which future climate scenario we are likely facing, making it easier to agree appropriate mitigation and adaptation strategies. There is therefore an international drive to develop new techniques and technologies to make satellites even more accurate, and the UK is at the heart of these efforts.
The National Physical Laboratory (NPL), the UK’s national measurement institute, set up the Centre for Carbon Measurement five years ago to bring together NPL’s measurement expertise to tackle climate change. One of the Centre’s core themes is to reduce uncertainties in climate data across the full supply chain; from calibrating the satellites before they’re launched, to assuring the quality of the information that they deliver.
A novel approach to reducing uncertainty is to rethink how satellites operate. The Centre, with a wide consortium of partners, has designed a proposed satellite mission called TRUTHS (Traceable Radiometry Underpinning Terrestrial-and-Helio Studies). This will, if launched, put highly accurate laboratory calibration methods onto the satellite itself, giving TRUTHS the capability to recalibrate its instruments whilst in orbit. This new approach will allow TRUTHS to take measurements at an accuracy around ten times better than currently possible.
However, the key and truly unique benefit of TRUTHS is that it can transfer its calibration to other satellites by measuring the same area and comparing the offset in the measurements. This provides an opportunity to upgrade the accuracy of the global optical EO system, making it easier to compare between different satellites and improving the availability of high quality climate data.
As the amount of satellite data grows, the need for accurate measurement and well-calibrated data will only grow with it. The benefits of accessing extensive and accurate data is clear: helping us understand our environment in unparalleled detail and facilitating more timely action on climate change.