  Far-infrared detectors for future cooled space telescopes require
ultra-sensitive detectors with optical noise equivalent powers of order 0.2
aW/\sqrt Hz. This performance has already been demonstrated in arrays of
transition edge sensors. A critical step is demonstrating a method of
fabrication and assembly that maintains the performance but that is extendable
to create large-scale arrays suitable, for example, for application in
dispersive spectrometers where it may be advantageous to fabricate the array
from smaller sub-arrays. Critical here are the methods of assembly and
metrology that maintain the required tolerances on the spatial alignment of the
components in order to maintain overall performance. These are discussed and
demonstrated.
