Tuesday, 22 January 2019

The Galileo satellite constellation

The Galileo satellite constellation is a keystone European project. It is designed to provide Europe with an independent global navigation satellite system (GNSS), similar to the global American GPS, Russian Glonass and Chinese BeiDou systems (along with regional ones such as India's NAVIC system or Japan's little-known QZSS).

There are two major aspects to such systems: the civilian, which you or I use (generally for free) to tell us where we are, and a secure subsystem (in the case of Galileo, called the 'Public Regulated Service') [4], which is encrypted. In times of war, the civilian system can have its accuracy degraded, be spoofed, or even be switched off, whilst military and other official users maintain their access via the secure PRS. The US GPS system operates a similar encrypted system called 'Precision Code' or 'Military Code', which is only accessible to US military users.

Satellite navigation systems have become a massively important part of our nation's infrastructure. As the government says [1]:
"Recent estimates indicate that over 11 per cent of the UK’s GDP is directly supported by satellite navigation systems and the Blackett review [3] estimated that a failure of service could cost the UK economy £1 billion a day."
With at least three competing global systems, it is unlikely that they will all be degraded simultaneously for the civilian user - and if they are, it will probably be the least of our worries.

But access to such systems are becoming vital for military and governmental users, with all sorts of equipment requiring accurate positioning and timing information, from the big-ticket items such as ships and planes, through missiles and smart bombs to communication systems. Losing access to guaranteed accurate positioning and timing information could well make even the best equipped and trained force a loser.

If you are a world power, you have to have trusted access to the secure parts of a GNSS. Failure to do so could literally leave you adrift in a conflict.

The Galileo project was started by the European Space Agency in 1999, and the European Union took it over, somewhat controversially, in mid-2006 after funding problems. This is part of a trend of the EU taking over and assimilating ESA projects - even after Brexit, the UK will remain a firm member of ESA.

The first Galileo satellites, GIOVE-A and GIOVE-B, were launched in 2005 and 2008 respectively. GIOVE-A was built by Surrey Satellite Technology Ltd in the UK, and it was designed to secure the frequencies required by the Galileo system and to test some of its key technologies. The first two In-Orbit Validation (IOV) satellites were launched in 2011, and the first Full Operational Capability satellites were launched in August 2014.

The Galileo constellation will eventually consist of 30 satellites for full global coverage, with 24 operational at any time, and 6 active spares. Each satellite weights about 700kg, and four can be launched on the same Ariane 5 launch. About 18 satellites are currently operational, with another 4 under commission. This is enough to operate Galileo's civilian side, and many devices can access the signals, including most recent smartphones. The secure side of the system is due to start operation in 2026.

In addition to the satellites, ground stations of various types needed to be constructed, including control centres, data uplink and telemetry stations. Many of these have to be spread globally to allow full control of the satellites, and are costly to run.

Galileo has two additional features: a paid-for commercial system that gives increased accuracy over the standard civilian signals, and the MEOSAR search and rescue system (Galileo's implementation of MEOSAR also include a downlink, so messages can be sent to a beacon). Galileo is also designed to allow emergency access to first responders in the case of a national disaster.

Galileo is a vital piece of infrastructure for Europe. It has not been plain sailing, especially financially, but much of the constellation is now in orbit and operational.

Finally, an aside. One of the reasons the UK government under Blair was so keen on getting the Galileo project started was a proposal that would allow tracking of road vehicles [2]. This would allow governments to implement road pricing by usage - albeit with some rather major privacy implications.

If you want to know more about how GNSS systems such as Galileo work, then chapter 1 of the Blackett review [3] goes into a great deal of relatively-understandable detail.

[1]: https://www.gov.uk/government/news/uk-to-tell-eu-it-will-no-longer-seek-access-to-secure-aspects-of-galileo
[2]: https://www.theregister.co.uk/2007/02/22/blair_road_pricing_privacy/
[3]: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/676675/satellite-derived-time-and-position-blackett-review.pdf
[4]: https://www.gsa.europa.eu/security/prs

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