A total of 18 hexagonal mirrors, each coated with 48g of gold to maximise their infrared reflectivity, have now clipped into place. 

The mirror is so big that it had to be folded in an orgami-style to fit in the rocket that blasted from South America two weeks ago. The riskiest operation occurred earlier in the week, when the 71ft sunshield unfurled, providing subzero parasole for the mirror and infrared detectors.

Flight controllers in Baltimore began opening the primary mirror on Friday, unfolding the left side like a drop-leaf table. 

As the right side snapped into place on Saturday, there was a flurry of applause, but the controllers had to stifle their celebrations as they began remotely locking the mirrors into place.

This mirror is made of beryllium, a lightweight and cold-resistant metal. The hexagonal, coffee table-size segments must be adjusted in the coming days and weeks ahead so they can focus as one.