Most people are familiar with maps on their smart-phone, with their location displayed, either with pin-point accuracy or at least good enough. I’ll not normally give any thought to perhaps eight satellites providing signals that are interpreted and combined to provide not only latitude and longitude, but also height relative to a calculated earth’s surface. A gravitational anomaly under southern England distorting the earth’s roundness means I frequently appear to be driving or walking underwater.
This use of satellites already in orbit is referred to as “down-stream”: in economic terms, globally this is expected by 2030 to have an economic value in the order of £400B pa. Of this, some 10% of is projected to be generated in the United Kingdom.
Ships and aeroplanes can also fix their location using the same GPS satellites, then send data including position via communications satellites. As a trivial example, this allows smart phone apps like Flightradar24 to tell my airport transfer driver how delayed I’m going to be. This allows them to minimise the time they’re at expensive airport parking. There are more important uses being developed by Southampton company Snowflake Software. Satellite communications also allow rapid reporting of volcanic ash clouds and patches of turbulent air. These reports allow other aircraft to avoid these hazards. Turbulence can lead to significant injuries to passengers and crew. Taking steps to avoid injury reduces insurance premiums, so subscriptions to the service are self-financing.
Similar principles can be applied to air-traffic control (NATS in the UK). If there is significant congestion NATS can instruct aircraft within their jurisdiction to slow down. This means the planes are burning less fuel per mile, reducing or avoiding the passenger frustration of being in a “holding pattern stack” (having hurried to the destination), and generating less CO₂ overall.
Theme 3 of the Catapult Satellite Applications initiative in the UK covers various aspects of satellite communications integrity and security. There is the infinitesimal risk of a space junk destroying or disabling a satellite, ironically making yet more space junk; a major solar-storm like the Carrington Event of 1859; malicious actors setting out to disable, block or distort satellite communications. One satellite malfunctioning should not affect Satnav, as usually data from at least five satellites are amalgamated. In today’s era of the cyber ‘shadow war’, the additional risks of wilful degradation of the entire service with a strong interference signal, or the satellite owners turning off the service, needs to be considered. While my car has a built in Satnav, plus I have two map apps on my smart phone, still I keep a road atlas in my car too. As a side note, it should be realised of course that civilian transport issues will be trivial compared to the national security issues implicit in a sabotage of satellite communications.
Satellite technology not only guide vehicles or track trains, it is also used to monitor the infrastructure these use. On 14th August 2018 the Morandi road bridge through the Italian city of Genoa collapsed without warning, killing 43 people. A project to monitor the Forth Road Bridge in Scotland, to provide some warning, is now in place. There are nine GPS receivers installed, in addition to accelerometers, anemometers and inclinometers. The signals from these instruments are used to determine the health of the bridge and the safety of its users.
Thanks: I am indebted to the faculty of the University of Portsmouth for three events they organised about advances in down-stream satellite technology.
Brexit Footnote: the European Space Agency is not a European Union agency. On the face of it, there should be no “Brexit Effect”, but there could be minor secondary disruption such as travel visa requirements.
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