10-5-1993 Landsat 6 failed to achieve orbit due to a ruptured hydrazine manifold which stopped fuel from reaching the satellite's stabilizing engines, preventing its ability to attain a stable orbit.

Landsat 6 (made by GE) was carrying the first version of the Enhanced Thematic Mapper (ETM) sensor which had the new capability of imaging in a 15 m pan band as was well as the other 7 spectral bands.

The MSS sensor aboard Landsat 5 failed and all of the MSS data acquired after after July 14, 1998 were unusable. An error in the scanning mirror, and general deterioration of the sensor after 15 years of operation, caused an error in the 'line start' which produced irreparable scanline errors in Band 4. As a result MSS data acquisitions were stopped.

Landsat 4 (launched in 1982) and Landsat 5 (launched in 1984) were already well beyond their designed life spans but Landsat 5 continued to supply imagery to downlink stations until 2001 when it was decommissioned by Space Imaging (who operated Landsat 5) at the request of USGS who could not afford to pay for continued maintenance. The main reasons for keeping the system online were as a backup in case Landsat 7 failed and to augment the global archive in tropical regions where clouds severely restricted successful acquisitions. $2.6 million dollar operating budget that Space Imaging requested was however not worth it.

Landsat 4 lost the ability to transmit data to ground stations in August of 1993, but continued to be useful to test orbit adjustments and program routines on before implementing them on Landsat 5.

More Info:
Black Days in Remote Sensing
http://www.itc.nl/~bakker/launches.html
The Satellite Morgue
http://www.watleo.uwaterloo.ca/~piwowar/geog376/EOSatellites/Morgue.html