  Far-infrared astronomy has advanced rapidly since its inception in the late
1950's, driven by a maturing technology base and an expanding community of
researchers. This advancement has shown that observations at far-infrared
wavelengths are important in nearly all areas of astrophysics, from the search
for habitable planets and the origin of life, to the earliest stages of galaxy
assembly in the first few hundred million years of cosmic history. The
combination of a still developing portfolio of technologies, particularly in
the field of detectors, and a widening ensemble of platforms within which these
technologies can be deployed, means that far-infrared astronomy holds the
potential for paradigm-shifting advances over the next decade. In this review,
we examine current and future far-infrared observing platforms, including
ground-based, sub-orbital, and space-based facilities, and discuss the
technology development pathways that will enable and enhance these platforms to
best address the challenges facing far-infrared astronomy in the 21st century.
