First Sentinel satellite in orbit after successful Soyuz launch
BY STEPHEN CLARK
Posted: April 4, 2014
Europe's first Sentinel satellite blasted off Thursday and deployed its radar antenna and solar panels overnight, inaugurating a multi-billion dollar series of satellites to take the pulse of Earth's land surfaces, oceans and atmosphere with unmatched regularity.
A Russian Soyuz rocket boosted the spacecraft north from French Guiana, streaking through low-level clouds and into the upper atmosphere as ground-based tracking cameras recorded dazzling views of the 151-foot-tall launcher shedding its boosters and disappearing into the evening sky.
The Soyuz rocket's Fregat upper stage ignited for a 10-minute firing to put the Sentinel 1A spacecraft into a 425-mile-high orbit over Earth's poles.
The Fregat upper stage deployed the Sentinel 1A satellite about 23 minutes after liftoff. After a slight delay to receive data confirming the separation, officials declared the launch a success.
"Tonight was the seventh success of Soyuz from the Guiana Space Center," said Stephane Israel, chairman and CEO of Arianespace, operator of Soyuz missions from French Guiana. "As its heavy-lift Ariane 5 and lightweight Vega siblings in the Arianespace family, Soyuz provides unrivaled quality, reliability and schedule assurance to our customers."
Manufactured by Thales Alenia Space in Italy and France, the Sentinel 1A satellite is the first of five spacecraft set for launch before the end of 2015 under the auspices of the Copernicus program, a joint initiative between the European Space Agency and the European Commission, the EU's executive body.
"The launch of the Sentinel 1A satellite from the European space center marks the takeoff of the Copernicus program," said Jose Manuel Barroso, president of the European Commission. "It's an important step forward for the European Union."
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.
"Once all the Sentinel satellites have been launched, the Copernicus program will be the most efficient and fullest Earth observation program in the world," Barroso said. "It will have specific and tangible economic, social and environmental consequences in Europe."
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.
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.
The sophisticated radar antenna, comprised of five panels folded around the satellite's main body for launch, completed a complex deployment sequence about 10 hours after liftoff.
Sentinel 1A's two solar array wings also unfurled to charge the satellite's batteries.
Engineers choreographed the deployments so the most critical steps occurred while the satellite was over ground stations, giving controllers real-time insight into the status of the spacecraft.
When the antenna and arrays were extended, Sentinel 1A radioed home a "space selfie" showing one of its solar panels and half of the rectangular radar backdropped by Earth more than 400 miles below.
The 40-foot by 3-foot rectangular C-band radar antenna array is comprised of 560 dual-polarized small transmitters and receivers to detect radar waves reflected from Earth's surface. The instrument will be switched on early Sunday and ESA plans to release its first images in about three weeks. Officials expect Sentinel 1A to be returning operational data by July.
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.
The Sentinel 4 family includes hosted payloads on Europe's Meteosat Third Generation geostationary weather satellites to study the atmosphere.
Each class of Sentinel satellite -- Sentinels 1, 2, 3, 4 and 5 -- are designed to always have two spacecraft in orbit at the same time.
The satellites will collectively monitor Earth's land surfaces, maritime zones and the atmosphere, beaming back data through a laser communications link with satellites orbiting overhead in geostationary orbit.
Officials plan to provide data to users within an hour, but Copernicus will supply some expedited data to security forces, emergency responders and other institutions within minutes, if necessary.
"This will be a complete coverage in every frequency band, which will be operational at the end of the decade," said Jean-Jacques Dordain. "This first of the dedicated satellites for the Copernicus program is a major step to put it into orbit."
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.
"Our fellow citizens will benefit from the wide range of services to protect their environment, their quality of life and their security," Barroso said. "For example, the data collected will contribute to the monitoring of climate change on the Earth's surfaces, including forests and oceans. It will also provide support in emergency situations, which do not spare our continent."
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