The Main Electronics Box (MEB) of the HAO coronagraph/polarimeter

The Solar Maximum Mission (SMM) was launched in February, 1980 with a complex of instruments designed to study the active Sun. The HAO instrument (C/p) operated satisfactorily until July when a series of partial failures began. Analysis and resolution of problems up to the terminal failure on September 23, 1980 are described. The Main Electronic Box (MEB) was replaced in orbit in April, 1984, restoring the observational capability of the c/p instrument. The process of trouble-shooting and restoration of the failed MEB is described. Conclusions are presented regarding the cause of the failures encountered.