The Landsat 4 system was an experimental earth resources monitoring system with the new powerful remote-sensing capabilities of the thematic mapper (TM), and it provided a transition for both foreign and domestic users from the multispectral scanner (MSS) data to the higher resolution and data rate of the TM. It had a complete end-to-end highly automated data system, which was designed to be a new generation system, and was a major step forward in global remote-sensing applications. The Landsat 4 mission consisted of an orbiting satellite (flight segment) with the necessary wideband data links and support systems, and a ground segment. The Landsat 4 flight segment consisted of two major systems: (1) the instrument module, containing the instruments together with the mission unique subsystems, such as the solar array and drive, the TDRS antenna, the wide-band module (WBM), and the global positioning system (GPS); and (2) the multimission modular spacecraft (MMS) that contained the modularized and standardized power, propulsion, attitude control, and communications and data handling subsystems. The flight segment was designed with 3 years nominal lifetime in orbit and could be extended through in-orbit replacement capability when the Space Shuttle became operational. The spacecraft was placed into an orbit having a descending node equatorial crossing between 9:30 and 10:00 a.m. local time. The spacecraft and attendant sensors were operated through the GSTDN stations before the Tracking And Data Relay Satellite System (TDRSS) was available. [An identical back-up spacecraft, Landsat-D Prime (NSSDC ID Landsat-E) was placed in storage and launched on March 1, 1984.] On October 1, 1982, NOAA assumed responsibility for Landsat data production and archiving activities at the Department of Interior's EROS Data Center. On January 31, 1983, NOAA also took over the MSS operation and maintenance of the Landsat spacecraft and ground system resources from NASA. The RBV operation was under NOAA as of Oct. 1, 1984.
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