The ERS 2, is built by a consortium led by, Daimler-Benz Aerospace. The 2,516kg spacecraft is based on the design of the Matra Marconi Space Spot commercial remote-sensing satellite. With the exception of the GOME and a visible wavelength band for the Along Track Scanning Radiometer (ATSR), the instruments are similar to those carried on the ERS 1:
active microwave instrument: C-band synthetic-aperture radar (SAR), with wind scatterometer and radar altimeter;
along-track scanning radiometer: six visible and infra-red channels, used to measure sea-surface temperatures and classify vegetation cover, and a microwave sounder;
global ozone-monitoring experiment;
precise-range and range-rate equipment: determines the orbit and trajectory of the ERS, to enhance the accuracy of the information from the other instruments, with laser reflector.
The ERS 2 will take three days and 43 orbits to observe the entire planet from its Sun-synchronous, 785km orbit. The imaging radar will need 35 days, or 501 orbits, to cover the planet, because of its high resolution and narrower observation swaths. Low-bit data-rate instruments generate 1 million bit/s of information, but as the SAR generates 105 million bit/s of data - the equivalent of 5,600 typescript A4 pages - this is transmitted directly to the ground, rather than stored on board.
As the SAR uses a high amount of electricity, acquisition is possible only for 10% of each orbit, so the scheduled image taking has to be carefully planned and coordinated by ESA's Italian ground station at Frascati, near Rome.
The SAR data is transmitted directly to a worldwide network of ground stations in Sweden, the Canary Islands and Italy, with four associate stations also in Sweden and the Canary Islands, and in Canada, which also receive the low-bit stored data. In addition, more than 20 other SAR stations receive data on ESA's behalf.
Although some data can be transmitted directly to users - called Fast Delivery Products - most is sent on magnetic tape to one of ESA's four processing and archive centres in Germany, the UK, France and Italy. The raw data is catalogued and converted into data products for customers.
Source: Flight International
