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Europe's Earth observing system ready for liftoff

Posted: April 2, 2014

The first spacecraft in a multi-billion dollar fleet of European environmental satellites is set for launch on a Soyuz rocket Thursday to begin supplying global radar coverage for scientists and security institutions to track maritime threats, manage resources and respond to emergencies.

Artist's concept of the Russian Soyuz rocket launching the Sentinel 1A satellite. Photo credit: ESA/ATG medialab
Fitted with a cloud-piercing, night-watching C-band radar instrument, the Sentinel 1A satellite will inaugurate the Copernicus program, a joint initiative between the European Space Agency and the European Commission, the EU's executive body.

"It is the most ambitious Earth observation program ever conceived worldwide," said Josef Aschbacher, director of ESA's Copernicus space office. "Nothing else [like Copernicus] exists in any other part of the world."

Four more satellites will join the Sentinel constellation by the end of 2015, followed by a steady cadence of launches extending into the 2020s to maintain worldwide coverage, according to Guido Levrini, ESA's manager of Copernicus satellite development.

The Sentinel fleet will together monitor the world's land surfaces, oceans and atmosphere.

Sentinel 1A is mounted to a Europeanized version of Russia's Soyuz rocket on a launch pad in French Guiana. Managed by Arianespace, the French launch services firm, the mission is scheduled for liftoff at precisely 2102:26 GMT (5:02:26 p.m. EDT: 6:02:26 p.m. local time) Thursday.

"It has been 10 years of professional life to build up to this moment," Levrini said in an interview Tuesday. "Of course, this moment is not the only one. It's just the launch of the first satellite in a series, but still the first one is the most emotional one for sure."

The Soyuz rocket and its Russian-built Fregat-M upper stage will deploy the 4,755-pound spacecraft in a 430-mile-high orbit about 23 minutes after launch.

The Sentinel 1A spacecraft is enclosed inside the Soyuz rocket's 13.5-foot-diameter (4.1 meter) payload fairing. Photo credit: ESA/CNES/Arianespace - Optique Video du CSG - JM Guillon
"I have been working for so long on this program," Aschbacher said. "It will be a fantastic system, which we are building up for the benefit of mankind [and] for the benefit of citizens in Europe."

Manufactured by Thales Alenia Space of France and Italy, the Sentinel 1A satellite is designed for a seven-year operational lifetime.

Building on previous radar payloads aboard two European Remote Sensing satellites, the Envisat observatory and Canada's Radarsat program, it carries a C-band synthetic aperture radar developed by Airbus Defence and Space. The advanced instrument will record up to 8,000 gigabits of data every day for thousands of users, according to the European aerospace contractor.

"Radar is very [special] because it allows images day and night," Aschbacher said. "It is independent of weather, so you can see through clouds and through rain, and you can get an image of almost anything when the satellite is flying over an area."

European institutions will use Sentinel 1A's data to survey coastlines and maritime environments, watching for oil spills, tracking iceberg and ice sheet movements in shipping lanes, and detecting sea vessels.

The European Maritime Safety Agency based in Lisbon, Portugal, will be one of the primary users of Sentinel 1A imagery.

"EMSA is using the satellite images to detect potential threats in European waters," said Olaf Trieschmann, senior project officer at EMSA. "People on the coastline are dependent on the environment on the coastline, and trying to reduce the impact of oil reaching the coastline is tremendous."

Anne Glover, chief scientific advisor to European Commission President Jose Manuel Barroso, said maritime surveillance is crucial because the oceans help regulate the world's climate, provide a wealth of natural resources and a route for international transport.

Artist's concept of the Sentinel 1A satellite in orbit during radar mapping operations. Photo credit: ESA/ATG medialab
Sentinel 1A will help officials estimate ocean waves and currents and measure soil moisture, a key factor in crop security.

"There's an application that allows us to measure subsidence," Aschbacher said. "That means if a building is sinking in by a few millimeters you can monitor this from space from 700 kilometers in orbit, which is quite amazing that you can detect such small scale changes."

Within a half-day of Sentinel 1A's launch, the spacecraft will extend two solar panel wings to generate electricity and unfurl a 40-foot by 3-foot rectangular C-band radar antenna array comprised of 560 dual-polarized small transmitters and receivers to detect radar waves reflected from Earth's surface.

According to Levrini, ground controllers at the Sentinel operations center in Darmstadt, Germany, will switch on the radar and receive its first data Sunday, assuming an on-time launch Thursday.

Officials will release the first image from the Sentinel 1A radar approximately three weeks after launch, Levrini said, and the satellite will be declared operational in July.

"From July onward, we will start serving all the users," Levrini said.

By itself, Sentinel 1A will map the entire planet every 12 days and achieve full coverage of European territories in about three days. With the launch of the identical Sentinel 1B satellite at the end of 2015, the revisit time will be cut to six days globally and less than two days for Europe, Levrini said.

Such a rapid revisit time is feasible because of the spacecraft's wide viewing swath as Sentinel 1A flies through space at a speed of more than 17,000 mph, or nearly 8 kilometers per second. Its radar will scan Earth in strips as the spacecraft circles the planet from the North Pole to the South Pole in less than 100 minutes.

In its most high-resolution mapping mode, the Sentinel radar returns images with a pixel size of 5 meters, or about 16 feet, with a swath width of 80 kilometers, or about 50 miles.

Artist's concept of the two Sentinel 1 satellites circling the globe to observe the entire planet every six days. Photo credit: ESA/ATG medialab
But the satellite can adjust the radar sensor to a wide-angle mode to see a strip of Earth as wide as 450 kilometers, or 280 miles, trading resolution for viewing area.

"The revisit is the parameter in which all Sentinels excel," Levrini said.

European governments have spent or committed 7.2 billion euros, or about $10 billion, covering Copernicus planning and development since 1998 and satellite operations through 2020.

The Sentinel satellites were conceived to be primarily operational spacecraft, extending many observations pioneered by Europe's flagship Envisat environmental research satellite which failed in 2012.

Levrini said the next Copernicus satellite set for launch is Sentinel 2A in early 2015, followed by the launch of Sentinel 3A in mid-2015. The Sentinel 2 and Sentinel 3 series of satellites are smaller than Sentinel 1 and able to fit on light-class European Vega or Russian Rockot launchers.

Sentinel 2 satellites carry a multi-spectral optical camera, and the first two Sentinel 3 spacecraft will measure sea-surface topography, temperatures, and ocean and land color.

A small spacecraft named Sentinel 5 Precursor is also scheduled to launch at the end of next year to bridge a data gap between the failed Envisat satellite's atmospheric chemistry instrument and the next generation of European MetOp polar-orbiting weather observatories.

Around the end of 2015, Sentinel 1B will be launched on another Soyuz rocket to join Sentinel 1A. Levrini said the Sentinel 1B schedule is holding on to a launch opportunity in late 2015, but the flight may delay to early 2016.

Levrini said the Sentinel 1A satellite cost about 280 million euros, or $385 million, under current economic conditions. The mission's launch on a Soyuz rocket cost 67 million euros, or $92 million, he said.

The Sentinel 1 system's ground segment cost about 36 million euros, or $50 million, and the twin Sentinel 1 satellites will cost a combined 28 million euros, or $39 million, to operate annually.

The Sentinel 4 family includes hosted payloads on Europe's Meteosat Third Generation geostationary weather satellites to study the atmosphere.

Sentinel 1A inside an anechoic test chamber during radio frequency tests at Thales Alenia Space in Cannes, France. Photo credit: ESA/S. Corvaja
Officials say the collective observations of the Sentinel satellites and sensors will allow climate scientists, policymakers, and emergency responders to take the pulse of the planet with unparalleled precision, scope and timeliness.

European officials adopted an open data policy to share measurements from the Sentinel satellites to the global community free of charge, much like the data distribution models established by the U.S. Geological Survey's Landsat program and the U.S. Air Force's GPS navigation constellation.

"Access to data depends on two main factors," Aschbacher said. "One is how many times does a satellite fly over a certain area. The [Sentinel 1] satellite constellation has two satellites. With two satellites you see the same spot on the Earth at least every six days at the equator, and even more frequently at mid-latitudes. This is an improvement by a factor of at least six compared to Envisat, which was our workhorse up until two years ago."

Officials also must link end users with fresh satellite data for the Sentinel observations to have the most impact for decision-makers.

"The second point is how long does it take for the data after acquisition to get to the user," Aschbacher. "There we have a very rapid data access and dissemination system put in place, which allows near real-time data to get to the user within three hours after acquisition, which is very fast."

For some specialized users, such as the European Maritime Safety Agency in Lisbon, Aschbacher said the Copernicus program developed a data stream to supply the user with imagery within 10 minutes.

The Sentinel 1 satellites carry laser communications terminals to beam imagery to control centers through communications satellites in geostationary orbit, ensuring officials do not have to wait for a pass over a ground station to relay data.

"Ten minutes after an image is taken of an oil spill, the images can be provided to the user and then to the coast guards to take action," Aschbacher said.

Follow Stephen Clark on Twitter: @StephenClark1.