Galileo’s Two Giant Steps Back

September 24, 2014  - By
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Galileo’s first two full-operational capability (FOC) satellites have been in a safe state since August 28, under control from the European Space Agency’s (ESA’s) center in Darmstadt, Germany, despite having been released on August 22 into lower and elliptical orbits instead of the expected circular orbits.

ESA continues investigating the possible exploitation of the out-of-position satellites to maximum advantage, despite their unplanned injection orbits and within the limited propulsion capabilities. ESA specialists, supported by industry and France’s CNES space agency, are analyzing different scenarios that would yield maximum value for the program, and safeguard — as much as possible — the original mission objectives.

Galileo orbits viewed from above: Orbits of the fifth and sixth satellites in red, compared to their intended position in dashed green, and the position of the four satellites launched in 2011 and 2012 in solid green. This view looks down over the South Pole to illustrate how the inclination relative to the equator is less than intended. The satellites are in an elliptical rather than circular orbit, with a maximum altitude of about 25,900 km and a minimum altitude of about 13,700 km, compared to a planned circular orbit of 23,222 km altitude.

Galileo orbits viewed from above: Orbits of the fifth and sixth satellites in red, compared to their intended position in dashed green, and the position of the four satellites launched in 2011 and 2012 in solid green. This view looks down over the South Pole to illustrate how the inclination relative to the equator is less than intended. The satellites are in an elliptical rather than circular orbit, with a maximum altitude of about 25,900 km and a minimum altitude of about 13,700 km, compared to a planned circular orbit of 23,222 km altitude.

Experts representing the Galileo Program provided a frank and open update at the ION GNSS+ conference in Tampa on September 10, as reported by Richard Langley:

  • An inquiry board is looking into problem to find the root cause of the anomaly. The board has already met several times.
  • An intermediate report is due shortly; a final report and recommendations will come next month.
  • ESA is considering what can be done with the two satellites; ESA hopes to be able to use them operationally as much as possible.
  • ESA is also looking at the impact on the commercial Galileo service and the search-and-rescue service.
  • ESA is narrowing down the possible causes of the anomaly.
  • ESA is waiting for the enquiry board to report before deciding on when and how the next two satellites will be launched.
  • The payloads of the errant satellites are currently off.
  • ESA wants to try to raise the perigees of the satellites to get them out of the van Allan radiation belt as soon as possible to prevent damage to the satellites. Raising the perigrees will also to reduce the maximum Doppler frequency shift from 9.6 kHz to at least 6.8 kHz to allow receivers to easily acquire and track the satellites, but leave enough hydrazine for future station keeping.
  • ESA is looking at the almanac problem and whether unused bits in the Galileo navigation message might be able to support a special almanac for the satellites.
  • ESA is also looking at possible rephasing of the satellites to optimize their use with the other satellites in the constellation.
Galileo orbits viewed side-on: The fifth and sixth Galileo satellites in red, compared to their intended position in dashed green, and the position of the four satellites launched in 2011 and 2012, in solid green. This view looks side on to the two satellites’ orbital plane, which is off-center relative to Earth. The targeted orbit was circular, inclined at 55º to the equator at an altitude of 23,222 km.They are in a safe state, correctly pointing towards the Sun, properly powered and fully under control of an ESA–CNES team.

Galileo orbits viewed side-on: The fifth and sixth Galileo satellites in red, compared to their intended position in dashed green, and the position of the four satellites launched in 2011 and 2012, in solid green. This view looks side on to the two satellites’ orbital plane, which is off-center relative to Earth. The targeted orbit was circular, inclined at 55º to the equator at an altitude of 23,222 km.They are in a safe state, correctly pointing towards the Sun, properly powered and fully under control of an ESA–CNES team.

Soyuz at Fault? On August 28, the Russian newspaper Izvestia reported that “The failure of the European Union’s Galileo satellites to reach their intended orbital position was likely caused by software errors in the Fregat-MT rocket’s upper stage.”

“The nonstandard operation of the integrated management system was likely caused by an error in the embedded software. As a result, the upper stage received an incorrect flight assignment, and, operating in full accordance with the embedded software, it has delivered the units to the wrong destination,” an unnamed source from Russian space Agency Roscosmos was quoted as saying by the newspaper.

An independent inquiry panel has been set up by Ariane and headed by former ESA Inspector General Peter Dubock. It started work on August 28. The panel includes a couple of academics and a majority of ESA and EC figures.

The new EC commissioner in this area, Ferdinando Nelli Feroci, invited ESA and Arianespace to his study during the first week of September to present the initial results of the inquiry.

The commissioner commented, “The problem with the launch of the two Galileo satellites is very unfortunate. The European Commission will participate in an inquiry with ESA to understand the causes of the incident and to verify the extent to which the two satellites could be used for the Galileo programme. I remain convinced of the strategic importance of Galileo, and I am confident that the deployment of the constellation of satellites will continue as planned.”

The commissioner expects that the Galileo constellation will be fully deployed by the end of this decade. This may qualify as optimism because system planners had envisioned for six spares ­— and three are already blown.

Ariane and ESA did not insure the satellites.

According to back-of-the-envelope calculations, system operators are now one short of the minimum 24 needed for full 24/7 global coverage, as they have four in orbit validation satellites up (one broken) and 22 FOCs on order (two launched and now in what could be called a junk orbit), which makes a potential maximum 23 satellites that have actually been ordered ­­— one short of the target.

The Satellites Are Alright. Satellite manufacturer OHB Systems of Bremen, Germany, issued a release stating that “Controllers at ESA’s ESOC control centre in Darmstadt, Germany, confirm the good health and the nominal behavior of both satellites. They are in a safe configuration, are thermally stable, have stable pointing to the sun and sufficient power production. All platform subsystems have been checked and they work properly. Also, the procedures to deploy the solar arrays are successfully performed and all solar arrays are properly unfolded.”

Further, “The orbit anomaly has no impact on the production and delivery of the in total further 20 satellites. Two FOC satellites are currently at ESTEC test facilities in Noordwijk, the remaining are in various status of integration. ”

Blogs Alive; BBQ Mode. The chairman of the Executive Board of the German Aerospace Center, Johann-Dietrich ‘Jan’ Wörner, writes an interesting blog. A recent installment opened with a quote from Elon Musk: “Rockets are tricky.”

Wörner went on to say, “The Soyuz launcher lifted off from the European Spaceport in French Guiana. Initially, all of the measurements suggested a perfect mission; the launcher took off at the scheduled time, followed the prescribed trajectory, and the stage separation was carried out correctly. However, the first problem became apparent when the two satellites proved unable to deploy their solar arrays as intended. A more detailed analysis then revealed that the eccentricity, the altitude and the inclination of the satellites’ orbits with respect to Earth’s equator did not meet the specifications. The upper stage had also evidently failed to induce the planned rotation around the longitudinal axis of the spacecraft (known as ‘barbeque’ mode, designed to maintain favourable thermal conditions during exposure to the Sun).”

Further discussion of the possible causes of the anomaly can be found on a Russian site, which focuses on the Fregat stage thrusters and indicates that the Russians think the barbeque maneuver was completed, and thus not the problem.

The other big issue is how the telemetry didn’t pick up the issue straight away.

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Alan Cameron is editor-in-chief and publisher of GPS World magazine, where he has worked since 2000. He also writes the monthly GNSS Insights column for the weekly Navigate! e-newsletter.

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