An Early Gift from — and for — Galileo

December 19, 2014  - By
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Image: GPS World

They said it wasn’t possible — well to be frank, I said it wasn’t possible – but one of the two “misplaced” Galileo satellites, plucky Doresa, has delivered an early Christmas present to the European GNSS community by providing a first fix on Tuesday, December 9. The signal was received at the European Space Agency’s (ESA’s) technical centre in Noordwijk, the Netherlands and at the Galileo In-Orbit-Validation (IOV) test station at Redu in Belgium. Doresa teamed with the remaining three functioning Galileo IOV satellites to provide a Galileo positioning data first fix with horizontal accuracy better than two metres.

Since then fixes have also been performed using Galileo’s Public Regulated Service (PRS), the civilian encrypted highest-precision signal and one of the constellation’s unique selling points.

The satellite had transmitted its first navigation signal in space on November 29, following its attainment of a safer, more stable, and more circular orbit with the perigee some 3,500 kilometres higher than its original placement.

Doresa’s salvage has been a slow and steady journey since it was placed, with sister satellite Melina, into a fairly useless orbit in August following a launch anomaly. The original orbit, with a 26,000-kilometer apogee and a 13,800-kilometer perigee, prevented their use for navigation services because they were too low during part of their orbit to sense the horizon and correctly determine their own position. They were also getting a daily dose of radiation from the Van Allen belts.

Elevation

The elevation of the satellite started in late October and involved 11 firings of Doresa’s on-board thrusters. The craft now has only 15 kilos left from its original 65 kilo fuel payload but, given the fact that normally Galileo satellites are not required to make regular orbital manoeuvres, ESA engineers estimate this should be enough for a good 12 years of operation in the new orbit.

The next stage will be to repeat this manoeuvre with the second Full Operational Capability (FOC) satellite, Melina, according to a plan to get that into a similar orbit by the New Year. Pending tests of their positioning, navigation, and timing payloads, the two spacecraft are then likely to be able to contribute to the future Galileo navigation constellation. This was confirmed by Didier Faivre, ESA’s director for navigation, during the agency’s ministerial council meeting on December 2 in Luxembourg.

This end result is the best possible scenario given where the satellites were left after launch and is a considerable triumph for ESA’s mission control teams and flight engineers. Doresa is now able to use its Earth sensor continuously and keep its antennae orientated towards the Earth. Despite more than a month’s exposure to the Van Allen radiation, testing so far has shown no ill effects.

“The very good geometry of the satellites in the sky relative to the receivers helped us to achieve this result, plus the signal strength of the fifth satellite,” explained Gustavo Lopez Risueno, coordinating the receiver team at the Navigation Laboratory in ESA’s ESTEC technical centre.

The satellite signals should be usable immediately, in combination with additional navigation message information provided through ground networks, with mass market receivers. In fact the ESTEC Navigation Laboratory, working in conjunction with the European Commission and the European GNSS Agency (GSA), have already performed position fixes with both Galileo and GPS satellites using only navigation-assistance information.

With some adjustments to the Galileo network’s ground infrastructure, it looks like Doresa and Melina will be able to carry out most of the roles they were originally designed to do. They are the first of 22 Galileo FOC satellites to be built by OHB and launched by ESA over the next few years.

Toasted antennae

More good news. The problem with Galileo’s fourth IOV satellite, named Sif, that took it out of action at the end of May seems to have been characterised and — again — indicates that the satellite is not a complete loss to the constellation. While Sif’s E5 and E6 frequency bands are definitively blown, the satellite’s E1 Open Service band should be capable of broadcast.

The problem appears to have been a defective antennae. The four IOV satellites utilise one antennae design, while the FOC satellites have a different design. Fortunately there is no sign of a similar issue with the three other IOV craft, but they have been operating on reduced power as a precaution while the root cause of Sif’s failure is determined. ESA is currently fail-testing an example of the culprit antennae in the laboratory to see if the failure mode can be characterised.

“One of the possible root causes links the problem with the power emitted by the antenna. When we know more we’ll decide what to do with the other three. Since this event occurred in May and June, no more issues have arisen,” Faivre said.

Agreement

This is all a remarkable turnaround and good news for the wider European GNSS community and those stakeholders who have invested in the Galileo programme and its burgeoning application industry. Let’s hope the good fortune continues through 2015.

The administrative side of things is certainly moving on with the signing in October of an agreement which delegates a range of exploitation tasks for Galileo from the European Commission to the GSA, providing a framework and budget for the development of services and operations through to 2021.The signing of the agreement is an initial step towards the full Galileo Exploitation Phase. Current planning calls for this exploitation phase to be progressively rolled out from 2015, with full operability scheduled for 2020.

“With Galileo, we aim to provide a tangible service to European citizens, and this Delegation Agreement ensures we have the tools and funding necessary to achieve this,” said GSA Executive Director Carlo des Dorides. The agreement was signed by Daniel Calleja Crespo of the European Commission and des Dorides. The document specifically sets the actions to be implemented, the amount of funding provided, and the conditions for the overall management.

Innovation

In the same month, the First Satellite Masters Conference took place in Berlin on October 23 and 24. The conference encompassed the 2014 edition of the European Satellite Navigation Competition (ESNC). The event was a great showcase for the innovation, skill, and passion of the entrepreneurs, usually young, who are building the satellite application market in Europe.

For example, the winner of the GSA special prize at ESNC 2014 is developing Galileo modules for the Google Ara modular smartphone concept, a potential game-changer for positioning in the mobile-phone market. Ara uses interchangeable modules to deliver a smartphone that can be whatever a user wants it to be, complete with first- and third-party components including sensors, cameras, radio antennas, and more. Consumers will be able to order them as of January 2015.
Google developers believe an Ara smartphone will last multiple years, much longer than current hardware, since it won’t be obsolete nearly as quickly. Further, Ara could open the smartphone market to billions of new users across the globe.

I spoke with Giovanni Vecchione of Deimos Space, who received the € 40 000 GSA/ESNC prize during the awards ceremony at Deutsche Telekom’s magnificent headquarters in the German capital.

“With a traditional chip structure, all of a smartphone’s functions are currently combined into a single component, which makes it difficult to add or change a function,” explained Giovanni. “With a modular structure, you have the option to simply switch out a component, meaning a smartphone’s capabilities can be easily enhanced.”

Vecchione’s innovation is to use another of Galileo’s unique selling points: the E5 broadband signal. While mass market smartphones will use the E1 signal, the availability of high-end phones offering enhanced accuracy through the use of the E5 signal will appeal to many users. A second module will implement an external antenna interface. Together these developments could deliver an ARA phone offering high precision (centimetre-level accuracy) positioning and multipath-resistant solutions.

Wishing you all a very peaceful and prosperous New Year and hoping Santa has your coordinates accurately entered in his sleigh satnav!

A bientôt, as they say in these parts.

About the Author:


Alan Cameron is the former editor-at-large of GPS World magazine.

1 Comment on "An Early Gift from — and for — Galileo"

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  1. Bob Munt says:

    It is nice to be wrong sometimes!!

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