The study of the sky at radio wavelengths shorter than 1 mm, specifically 0.3–1.0 mm. As with millimetre-wave astronomy, this part of the spectrum is rich in lines emitted by interstellar molecules, dust, and jets close to black holes. This region was previously considered part of the far infrared, but is now regarded as an extension of the radio spectrum since instrumental techniques developed to investigate it have more in common with radio astronomy than infrared astronomy. Atmospheric water vapour and other molecules obscure shorter wavelengths from ground-based observation, but this can be partly overcome by placing the instruments at high altitude. Major submillimetre telescopes include the 15-m James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array.