German radar imaging satellite launched into space
BY STEPHEN CLARK
Posted: June 15, 2007
A German satellite carrying a cloud-piercing, night-vision radar was launched early Friday to create the most precise maps and imagery ever produced by a civilian space radar system.
Called TerraSAR-X, the craft will spend the next five years circling the planet at an altitude of about 319 miles to gather vast volumes of data using a cutting edge X-band radar system.
The nearly 3,000-pound satellite was launched Friday from the Baikonur Cosmodrome in Kazakhstan. The three-stage Dnepr rocket flew out of its underground missile silo at 0214 GMT (10:14 p.m. EDT Thursday) and successfully guided the spacecraft into a Sun-synchronous orbit, according to project officials.
TerraSAR-X contacted a ground station in Kenya about 30 minutes after liftoff, confirming the craft was in good health following the ride to space.
The mission's launch was postponed several months after an earlier flight of the Dnepr rocket suffered a major failure last year. The Dnepr, a converted ballistic missile from former Soviet military arsenals, was grounded for about nine months while engineers wrestled with technical problems.
Managers at Kosmotras, the international firm in charge of marketing Dnepr launch services commercially, also had to convince Kazakh officials to allow Dnepr flights to resume from the country's territory.
The Dnepr returned to flight in April, when it launched a group of small satellites for international customers.
Another Dnepr launcher is awaiting launch late this month with Genesis 2, the second inflatable module for Bigelow Aerospace, the private space company.
TerraSAR-X will undergo a testing phase through this fall, during which ground controllers will validate the health of the satellite's radar system. Officials expect to enter the operational phase of the nearly $250 million mission by the end of the year.
The mission's cost is split between the public and private sectors, including satellite-builder EADS Astrium, the imagery sales company Infoterra, and DLR, the German space agency.
TerraSAR-X's radar will be capable of imaging up to one million square kilometers, or almost 400,000 square miles, of Earth's surface per day, according to a written statement from the mission partners.
The X-band synthetic aperture radar system works by sending radar beams toward Earth and collecting the returns of the pulses after bouncing off the surface. This method will yield precise maps of the entire planet with resolutions as high as one meter, or about three feet.
The radar can also steer its radio pulses without maneuvering the spacecraft, which will allow scientists to gather data using three techniques. The methods include imaging the Earth's surface in a fixed strip mode, scanning across the satellite's ground track, and continuously training radar beams on a specific area as the craft flies overhead.
Each technique covers different land areas and offers varying image resolutions.
Satellite radar systems are useful because they can peer through thick clouds and darkness, unlike conventional remote sensing instruments relying on visible light.
"This is decisive, especially in regions near the Equator which are often clouded," said Wolfgang Pitz, TerraSAR-X project manager at EADS Astrium.
TerraSAR-X can trace its heritage to previous X-band radar systems that flew on three space shuttle missions in 1994 and 2000. Germany participated on all three missions.
"X-band technology has always been a German specialty," Pitz said last year. "In this field, we are at the leading edge worldwide."
TerraSAR-X aims to improve current topographic imagery by a factor of ten, according to project officials. Topographic mapping is a major application for mission data.
The data will be evenly split between scientific and commercial applications. DLR, the German space agency, is responsible for utilizing science data, while Infoterra will place imagery on the commercial market.
Scientists and customers will use the information to help monitor vegetation and crops across the globe, and special emphasis will be placed on keeping tabs on environmental changes. Polar sea ice, coastal regions and areas with seismic activity will also be potential targets for the satellite. In addition, TerraSAR-X data will be used to track urban development and its impact on the environment.
Governments can also use radar imagery to aid in disaster response and military reconnaissance.
"In the first year of operation, we will gain a lot of experience and encounter applications we do not even consider at the moment," said Jorg Herrmann, chief executive officer of Infoterra.
A follow-on satellite – TerraSAR-X2 – is already in development. The craft would be financed by Infoterra profits from TerraSAR-X imagery if the project is commercially successful. Its launch could occur in 2011.
TanDEM-X, which consists of a complementary satellite flying in formation with TerraSAR-X, is also on tap for the future. A second satellite would help collect three-dimensional topographic images of Earth.