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ESA trusts fixes to Swarm's Russian-built launcher

Posted: November 11, 2013

Going into the Nov. 22 launch of the European Space Agency's $300 million Swarm mission, which promises to collect exquisite data on Earth's magnetic field, European officials say they trust Russian authorities have done all they can to ensure Swarm's Rockot launch vehicle and Breeze upper stage are not afflicted with the problems that have caused a series of launch failures in recent years.

The three Swarm satellites are pictured in Russia before they were attached to the Rockot's custom-built adapter. Credit: ESA/M. Shafiq
The three identical Swarm satellites, each weighing about 1,043 pounds when fueled for launch, will attempt to detect the disparate sources of Earth's magnetic field, a bubble which shields the planet from cosmic and solar radiation. But the magnetospheric bubble is also susceptible to solar storms, which cause communications and electrical blackouts, and scientists say there is strong evidence the magnetic field is weakening.

The launch of ESA's Swarm mission was delayed more than a year to wait for its turn in a backlog of missions assigned to Russia's Rockot booster, which uses decommissioned Soviet-era missile engines and a Breeze KM upper stage.

"We are ready to get going, that's for sure," said Rune Floberghagen, Swarm's mission manager. "Having said that, of course, we can only trust that all the work that needs to be done to give us a reliable upper stage has been carried out."

The Breeze stages are built by Khrunichev State Research and Production Space Center, and the Rockot manifiest is managed by Khrunichev and the Russian Aerospace Defense Forces, a branch of the Russian military.

The Rockot missions lined up after a series of mishaps on missions using Breeze upper stages, including the Breeze KM version flown on Rockot flights and the larger Breeze M, which carries extra propellant and launches atop the heavier Proton rocket.

Breeze rocket stages encountered trouble on five flights since February 2011, with two of the anomalies striking Rockot launches and three malfunctions occurring on Proton flights.

Astrium GmbH of Germany, Swarm's prime contractor, had the three satellites ready for launch in July 2012, but unremitting anomaly investigations and delays brought on by launch mishaps forced engineers to put the spacecraft in storage.

The most recent Breeze KM problem occurred in January, when the stage's liquid-fueled engine failed to complete a maneuver to remove the rocket from orbit following its successful deployment of three Russian military satellites.

"The Rockot still has a very good track record," Floberghagen said. "On the other hand, we know this Breeze family of upper stages has been rather, shall we way, beleaguered in the last few years, and there has been trouble in the industrial consortium and the programmatic setup for these upper stages."

The Rockot is a modified two-stage missile originally built to deliver nuclear payloads to distant targets. Engineers converted the wartime weapon, known to Western observers as the SS-19, to a peacetime space launcher by adding a third stage to inject satellites into orbit.

Artist's concept of the Swarm satellites deploying from the Rockot's Breeze KM upper stage. Credit: ESA
"People are taking it seriously, and we can only count on the fact that this job has been done properly," Floberghagen said. "That being said, we are definitely ready to go on our side. We have a bunch of scientists that are really eager to get their hands on excellent new data on the magnetic field and on the geospace environment."

For Swarm's mission, the Breeze upper stage will fire two times, first to inject itself and the payloads into an elliptical parking orbit, then to circularize its altitude at about 490 kilometers, or 304 miles, Floberghagen said.

Floberghagen said the Swarm team used the extra time to improve the precision of the mission's science data. The satellites are "magnetically clean," meaning they are mostly free of materials that emit their own magnetic fields, which could throw off the mission's research aimed at Earth's magnetism.

And engineers have catalogued all components which could muddle Swarm's magnetic field measurements so scientists can account for the known errors when they analyze data.

In their review, engineers found measurements from Swarm's absolute scalar magnetometers, which measure the magnetic field at the tip of each satellite's extendable 13-foot boom, could be distorted by temperature changes as the spacecraft fly in and out of shadow.

While the satellites were in storage last year near Munich, workers replaced a titanium bracket near the magnetometer, rerouted power cables and changed out connectors to get rid of the imprecision.

"We have been able to essentially eliminate this effect of this temperature sensitivity on that unit. That means that, in the end, our vector field measurements of the magnetic field will be accurate to many times better - all the simulations show that so far - than the mission requirement, which is 1 nanotesla," Floberghagen said.

A tesla is a unit to measure the strength of a magnetic field.

"We think we have [an error] that is very low, in the order of 100 picotesla or so," Floberghagen said. "If that will be the case, the data from Swarm will be truly spectacular."

The latest launch delay from Nov. 14 to Nov. 22 allowed Russian technicians to replace a suspect gyroscopic unit in the Breeze KM's guidance system. Ground crews slowed preparations of the Swarm satellites to wait for rocket processing to get back on track.

ESA is spending 220 million euros, or about $295 million, to develop and operate the Swarm mission. CNES, the French space agency, separately funded the design and construction of one of Swarm's science instruments.

Artist's concept of the Swarm satellites operating in two distinct orbits, with two spacecraft in close formation and another flying higher to distinguish variations in Earth's magnetic field. Credit: ESA/ATG Medialab
Volker Liebig, head of ESA's Earth observation programs, said officials never considered switching Swarm's launch to a different rocket. The adapter connecting the Swarm satellites to the Rockot launch vehicle was custom-designed by Khrunichev to accommodate the three satellites, which measure 17 feet long with their deployable magnetometer booms stowed for launch. It would have taken two years to develop another adapter for a different booster, Liebig said in an interview.

According to Liebig, ESA has three launch contracts for Rockot missions beyond Swarm.

Eurockot, a joint German-Russian venture, manages commercial sales of the Rockot launch vehicle to international customers like ESA.

ESA is shifting launches of most of its Earth observation satellites to the European Vega rocket after the Italian-led launcher completed two successful test flights in February 2012 and May 2013.

Two launches of Sentinel Earth observation satellites are booked for Rockot launches under the umbrella of the European Commission's Copernicus climate and security program. Another Rockot mission is under contract by ESA to launch another Sentinel satellite or serve as a backup in case the Vega rocket encounters delays in the future.

Liebig said ESA views the Rockot as the most viable backup to Vega. The silo-launched Dnepr rocket, another converted Soviet-era missile, is being phased out of service in the coming years.

Follow Stephen Clark on Twitter: @StephenClark1.