A field spectral radiometer includes a support structure and a remote sensing head disposed on the support structure. The remote sensing head includes a central axis, a first optical element disposed on a first side of the central axis and defining a first optical path for a first optical channel, and a second optical element disposed on a second side of the central axis and defining second optical path for a second optical channel. An instrumentation assembly disposed on the support structure. the instrumentation assembly includes a first detection path associated with the first optical channel and a second detection path associated with the second optical channel, the first and second detection path include optical indexers for manipulating the first and second optical channels. The field spectral radiometer may include a calibration assembly disposed on the base. The calibration assembly may include a calibrating light source for calibrating the remote sensing head.