Earth Observation Satellites


Something to watch over us

The Earth should be monitored more carefully

Blind Earth  

ON APRIL 8th Envisat, Europe’s largest Earth-observing satellite, unexpectedly stopped talking to its users on the Earth below. Since then those users have been frantically trying to re-establish contact. They rely on Envisat’s radars and other sensors for a wide range of measurements, from the temperature of the oceans to the chemistry of the stratosphere. Scientists have used it to gauge ocean conditions for shipping and to investigate earthquakes; its data have been the basis of thousands of scientific papers.

Envisat had, unlike much of Europe, forgone early retirement: designed for five years of operation, it was on its tenth. Given its advanced years, you would think that planning for its eventual end would be well in hand. You would expect that successor instruments would already be in orbit, their measurements carefully cross-correlated with Envisat’s so that the elucidation of the scope and pace of global environmental change could continue seamlessly. You would be wrong.

Wilful blindness

Providing earthlings with a reliable, continuous record of their planet’s condition would seem a sensible aim in any circumstances. With the state of the atmosphere and oceans upset in ways whose consequences are not easily foreseen, and may well prove catastrophic, it becomes an imperative. You do not need to know every little thing about the environment in order to make policy about it. But only long-term measurements will allow researchers to get a reliable grip on the science of climate change and other environmental stresses. A firm grasp of the basic trends is a necessary precondition for understanding and for informed policy.

The governments that build and operate satellites like Envisat are not taking that necessity seriously. According to a damning report from America’s National Academies, the number of civilian Earth-observing satellites flown by the United States government looks likely to fall from 23 today to just six in 2020, and the number of instruments in orbit could drop from 90 to 20. The situation in Europe is somewhat less disastrous, but has its own problems. The European Space Agency is unwilling to move forward with a new generation of satellites that can monitor the environment continuously until the European Union promises to pay their operating costs.

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