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Envisat Smashes Terabyte Data Barrier

A European satellite recently passed a mind-boggling data transmission milestone while monitoring Earth’s environment from its 800-kilometer-high orbit.

Envisat (ENVIronmental SATellite), launched three months ago by the European Space Agency (ESA), on Sunday exceeded the terabyte mark for data transferred over a satellite channel. A terabyte is roughly equivalent to the text contained in about one million books.

Because each byte of imagery data is multicast to about four users, the fact that the satellite has surpassed the terabyte threshold means the total volume of data transmitted amounts to 4 terabytes — or about the same volume of information that could be stored on 6,000 compact disks. The data is delivered to end-users through the land-based observation data dissemination system (DDS).

What Goes Up
Envisat program manager Jacques Louet told that the massive amount of data sent through the satellite is downloaded to a station in Sweden and routed to a number of scientific users via satellite links through the DDS network. According to him, the data comprises images of the Earth taken from space by the eight-ton satellite, using the 10 optical, radar, infrared and other cutting-edge instruments it carries on board. “We are capturing images of the oceans, ice caps and land features for use by scientists around the world,” he said in an interview from Envisat’s Paris, France, headquarters.

The Real World
Envisat’s observations include examinations of topography and, especially, changes in the Earth’s features created by volcanoes and earthquakes.

“The data is being used by scientists in many different disciplines, using techniques proven with previous satellites launched by ESA,” Louet said. Perhaps most important, he added, is the fact that DDS transfers information within three hours of observation, which is about as close to real-time access as science currently has available.

Take Five
Louet explained that data transmission is accomplished using digital video broadcast (DVB), a standard that includes a specification for sending images over satellite links.

Envisat is a critical component of ESA’s strategy for Earth observation. From its orbit over the poles, the satellite will monitor – for the next five years – environmental processes ranging from changes in ocean circulation to land use, to atmospheric pollution, Louet said. According to ESA, the “super satellite” can register the smallest surface movement and provide advance warning of floods, mud and snow avalanches, and storms. It will observe polar ice and the level of the oceans; recognize El Nino before it builds in the Pacific ocean; measure the ozone layer; identify bush and forests fires, and pinpoint water sources in deserts.