ESA GALILEO: Satellite Recovered and Transmittting Navigation Signals

ESA's Galileo satellites are placed in medium orbits, at 23 222 km altitude along three orbital planes so that a minimum of four satellites will be visible to user receivers at any point on Earth once the constellation is complete. 

Credit: ESA

ESA’s fifth Galileo satellite, one of two delivered into a wrong orbit by VS09 Soyuz-Fregat launcher in August, has transmitted its first navigation signal in space on Saturday 29 November 2014.

It has reached its new target orbit and its navigation payload has been successfully switched on.

A detailed test campaign is under way now the satellite has reached a more suitable orbit for navigation purposes.

Recovery

The fifth and sixth Galileo satellites, launched together on 22 August, ended up in an elongated orbit travelling up to 25 900 km above Earth and back down to 13 713 km.

A total of 11 manoeuvres were performed across 17 days, gradually nudging the fifth satellite upwards at the lowest point of its orbit.

As a result, it has risen more than 3500 km and its elliptical orbit has become more circular.

“The manoeuvres were all normal, with excellent performance both in terms of thrust and direction,” explained Daniel Navarro-Reyes, ESA Galileo mission analyst.

“The final orbit is as we targeted and is a tribute to the great professionalism of all the teams involved.”

The commands were issued from the Galileo Control Centre by Space Opal, the Galileo operator, at Oberpfaffenhofen in Germany, guided by calculations from a combined flight dynamics team of ESA’s Space Operations Centre, ESOC, in Darmstadt, Germany and France’s CNES space agency.

The commands were uploaded to the satellite via an extended network of ground stations, made up of Galileo stations and additional sites coordinated by France’s CNES space agency.

Satellite manufacturer OHB also provided expertise throughout the recovery, helping to adapt the flight procedures.

Until the manoeuvres started, the combined ESA–CNES team maintained the satellites pointing at the Sun using their gyroscopes and solar sensors. This kept the satellites steady in space but their navigation payloads could not be used reliably.

In the new orbit, the satellite’s radiation exposure has also been greatly reduced, ensuring reliable performance for the long term.

2014 Arctic Sea Ice Minimum Sixth Lowest on Record

Arctic sea ice hit its annual minimum on Sept. 17, 2014. 

The red line in this image shows the 1981-2010 average minimum extent. 

Data provided by the Japan Aerospace Exploration Agency (JAXA) GCOM-W1 satellite.

Image Credit: NASA/Goddard Scientific Visualization Studio

Arctic sea ice coverage continued its below-average trend this year as the ice declined to its annual minimum on Sept. 17, according to the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder.

Over the 2014 summer, Arctic sea ice melted back from its maximum extent reached in March to a coverage area of 1.94 million square miles (5.02 million square kilometers), according to analysis from NASA and NSIDC scientists.

This year’s minimum extent is similar to last year’s and below the 1981-2010 average of 2.40 million square miles (6.22 million square km).

"Arctic sea ice coverage in 2014 is the sixth lowest recorded since 1978. The summer started off relatively cool, and lacked the big storms or persistent winds that can break up ice and increase melting," said Walter Meier, a research scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

“Even with a relatively cool year, the ice is so much thinner than it used to be,” Meier said. “It’s more susceptible to melting.”

This summer, the Northwest Passage above Canada and Alaska remained ice-bound.

A finger of open water stretched north of Siberia in the Laptev Sea, reaching beyond 85 degrees north, which is the farthest north open ocean has reached since the late 1970s, according to Meier.


An animation of daily Arctic sea ice extent from March 21 to Sept. 17, when the ice appeared to reach it’s minimum extent for the year. 

It’s the sixth lowest minimum sea ice extent in the satellite era. The data was provided by the Japan Aerospace Exploration Agency (JAXA) GCOM-W1 satellite.

Image Credit: NASA/GSFC Scientific Visualization Studio/T. Schindler

While summer sea ice has covered more of the Arctic in the last two years than in 2012’s record low summer, this is not an indication that the Arctic is returning to average conditions, Meier said.

This year’s minimum extent remains in line with a downward trend; the Arctic Ocean is losing about 13 percent of its sea ice per decade.

To measure sea ice extent, scientists include areas that are at least 15 percent ice-covered. The NASA-developed computer analysis, which is one of several methods scientists use to calculate extent, is based on data from NASA’s Nimbus 7 satellite, which operated from 1978 to 1987, and the U.S. Department of Defense’s Defense Meteorological Satellite Program, which has provided information since 1987.

Due to global warming, larger and larger areas of sea ice melt in the summer and when sea ice freezes over in the winter it is thinner and more reduced. 

As the Arctic summers are getting warmer we may see an acceleration of global warming, because reduced sea ice in the Arctic will remove less CO2 from the atmosphere, according to Danish scientist Dorte Haubjerg Søgaard, PhD Fellow, Nordic Center for Earth Evolution, University of Southern Denmark and the Greenland Institute of Natural Resources, Nuuk..

In addition to monitoring sea ice from space, NASA is conducting airborne field campaigns to track changes in Arctic sea ice and its impact on climate.

Operation IceBridge flights have been measuring Arctic sea ice and ice sheets for the past several years during the spring.

A new field experiment, the Arctic Radiation – IceBridge Sea and Ice Experiment (ARISE) started this month to explore the relationship between retreating sea ice and the Arctic climate.