We have used a Fourier Transform Spectrometer on the James Clerk Maxwell Telescope to study the submillimetre continuum emission from dust in three hot molecular cores ( HMC ) .
The spectral index \beta of the dust emission for these sources has been determined solely within the 30 GHz wide 350 GHz ( 850 µm ) passband to an accuracy comparable to those determined through multi-wavelength observations .
We find an average \beta \simeq 1.6 , in agreement with spectral indices determined from previous submillimetre observations of these sources and with those determined for HMC in general .
The largest single source of uncertainty in these results is the variability of the atmosphere at 350 GHz , and with better sky subtraction techniques we show that the dust spectral index can clearly be determined within one passband to high accuracy with a submillimetre FTS .
Using an imaging FTS on SCUBA-2 , the next generation wide-field submillimetre camera currently under development to replace SCUBA at the JCMT in 2006 , we calculate that at 350 GHz it will be possible to determine \beta to \pm 0.1 for sources as faint as 400 mJy/beam and to \pm 0.3 for sources as faint as 140 mJy/beam .