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6.3 Description of wideband data downlinked from the Satellite to the Landsat Ground System

The satellite contains the ETM+ instrument and a solid state recorder (SSR). The ETM+ instrument takes the data and separates the data into two formats. Format 1 (channel 1 also referred to as channel I contains bands 1-6 and format 2 (channel 2 also referred to as channel Q contains bands 6, 7, and 8 (PAN). Each format is transferred at 75 Mbps to a baseband switching unit (BSU) where the data is modulated and either downlinked in real-time to the Landsat Ground Station located at Sioux Falls, South Dakota, via an X-band link at a combined aggregate rate of 150 Mpbs, or recorded on the SSR. The data recorded on the SSR can be played back using one or two 150 Mbps bitstreams and downlinked to the LGS via the X-band link. When the spacecraft flies over LGS, it downlinks two 150 Mbps data streams, either 1 real-time and 1 playback, or 2 playbacks. Therefore, when the data is transmitted to the LGS, it is a combined rate of 300 Mbps, 150 Mbps bitstreams from the ETM+ and 150 Mbps bitstreams from the SSR or two 150 Mbps bitstreams from the SSR. Once the data is received at the LGS, the data is demodulated and transmitted to the LPS as 4 physical channels. Each of the 4 channels is transferred as 75 Mbps bitstream to the LPS.

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link and the housekeeping telemetry downlink will be via s-band while all the science data will be downlinked via x-band. A command and data handling subsystem will provide onboard commanding, data collection, processing and storage. A state-of-the-art solid state recorder capable of storing 380 gigabits of data (100 scenes) will be used to store selected scenes from around the world for playback over a U.S. ground station. In addition to stored data, real-time data from the ETM+ can be transmitted to cooperating international ground stations or to the U.S. ground station.