"" The astronaut, along with other contemporary symbols was added in 1992 during restoration work on the "new" cathedral. The person responsible for the restoration, Jeronimo Garcia, reportedly chose an astronaut as a fitting symbol of the twentieth century. According to an
article about the restoration (in Portuguese - Click
here for Google translation to English), it is a tradition of cathedral builders and restorers to include a contemporary symbol on the building as a means of "signing" their work.
A
Wikipedia article about the cathedral concurs:
Its main entrance consists of 3 arcs, each leading to the 3 naves (sections) of the church. All three are richly carved. Among the ornate carvings on the façade is the incongruous likeness of an astronaut floating in space; it was added by an artist during restoration work in 1992 as a symbol of the 20th century.
Thus, there is actually no mystery about the Cathedral "spaceman" whatsoever. """