by Jennifer Allerton, British Science Festival
If you’re a space lover, you may often wish that we had unlimited funds to explore the great unknown. In recent years, missions like the Rosetta-Philae comet lander have captured the public’s imagination. But with satellites costing upwards of £10million to launch, and in some cases reaching into the hundreds of millions of pounds, it is often asked by policy makers and taxpayers alike what the justification is – what are the benefits to society?
At the British Science Festival, Rodney Forster, marine biologist from the University of Hull and Carol Wright, who works with the European Space Agency, tried to provide one answer to this question.
As a researcher in applied marine sciences Rodney is particularly interested in the health of our oceans and what they contain. A key indicator of ocean health is ocean colour. At the bottom of the ocean’s food chain, and a staple of the diet of many fish, are phytoplankton, microorganisms which live suspended just beneath the ocean’s surface and photosynthesise. Under the right conditions they can reproduce at a rapid rate, creating ‘blooms’ which are visible from the air or from space.
Image credit: ESA (Envisat)
For over 70 years, the best technology available for measuring ocean colour and the contents of the ocean was the Continuous Plankton Recorder (CPR). The CPR was developed by fishery biologist Alister Hardy during a voyage to Antarctica from 1925-1927. In 1928 Hardy took up a post as Professor of Zoology at what was then the newly founded University College Hull, and soon refined a smaller version of his prototype CPR for use on merchant ships. This prototype was used in the first CPR Survey from Hull to Bremen, Germany in 1931. The instrument is about a metre long and is towed at a depth of 5-10 metres, filtering plankton and other particulate matter in the water through bands of silk. The silks are then analysed by an expert team of plankton analysts from the CPR Survey team at the Marine Biological Association, who today analyse approximately 5,500 samples per year.
Example of a Continuous Plankton Recorder instrument
There are limitations to these methods though. Only regular shipping routes are well surveyed, and it’s time consuming to collect a lot of data. Using satellites for Earth observation provides a good way to cover vast areas in much shorter timespans. Monitoring ocean colour can tell us a lot about the health of oceans and their ecosystems. The pigments in phytoplankton are clearly visible when blooms occur and analysing satellite images of variations in ocean colour can provide important information about the state and seasonal cycles of plankton populations.
The European Space Agency’s Copernicus programme incorporates a group of satellite missions called Sentinels whose focus is Earth observation for monitoring key climate variables. Sentinel-1 measures in radar, meaning that it can see through clouds and image the land and sea during day and night. Sentinel-2 takes images in bands mainly in the visible and infrared, making it ideal for monitoring the colour of our land and oceans. Other Sentinel missions will have instruments designed for further specialist tasks. One application is illustrated below, where you can see the browning of vegetation across Western Europe throughout the recent summer.
Image credit: ESA (Sentinel-3)
Dr Rodney Forster described research that he and his colleagues at the University of Hull have been able to conduct with the use of satellite data in the past few years. Dr Forster demonstrated the decrease in water clarity in the North sea throughout the late 20th century and the decline in production of phytoplankton. This directly and indirectly affects higher levels of the marine food chain, and is very important to the fishing industry, which in 2017 contributed an estimated £1.4bn to the UK economy¹.
As well as the benefits that Earth observation satellite technology can offer to industry, and their important role in monitoring climate change, Carol Wright and Rodney Forster highlighted the emerging low-cost future of satellite technology. This technology features cheap, small and easy to build ‘CubeSats’ and aircraft-based satellite launching, which significantly reduce the amount of fuel needed when compared to a ground-based launch. So, it seems that the question of whether space is worth the cost will only become an easier one to answer.
¹House of Commons Library Debate Pack CDP 2017/0256 “The UK Fishing Industry”