Abstract: The goal of the Millimetron project is to develop a space observatory operating in the millimeter, sub-millimeter and infrared wavelength ranges using a 12-m actively cooled telescope in a single-dish mode and as an interferometer with the space-ground and space-space baselines (the later after the launch of the second identical space telescope). The Millimetron’s main reflector and other optics will be cooled down to 4K thus enabling astronomical observations with super high sensitivity in MM and subMM (down to nanoJansky level). Heterodyne observations in an interferometer mode at frequencies 0.1-1 THz will provide super high angular resolution. The main instruments, planned to be installed are wide-range imaging arrays, radiometers with spectrometers and polarimeters, VLBI heterodyne receivers, and Mikelson type interferometer devices. Wide-range MM and subMM imaging arrays and spectrometers will be based on a superconducting hot electron direct detectors with Andreev mirrors operating at 0.1 K. Such detectors are the best candidates to reach the noise equivalent power level of 10 -19 -10 -20 W/√Hz. Heterodyne receivers will be both SIS based superconducting integrated receiver with flux-flow oscillator as LO (0.1-0.9 THz range) and HEB based receivers using multiplied Gunn oscillator as LO for 1-2 THz range and quantum cascade lasers as LO for 2-5 THz range. For observations in middle IR region there will be installed large arrays of superconducting single photon detectors, providing imaging with very high dynamic range and ultimate sensitivity.

Abstract: Millimetron is a Russian-led 12m diameter submillimeter and far-infrared space observatory which is included in the Space Plan of the Russian Federation and funded for launch after 2015. With its large collecting area and state-of-the-art receivers, it will enable unique science and allow at least one order of magnitude improvement with respect to the Herschel Space Observatory. Millimetron is currently in a conceptual design phase carried out by the Astro Space Center in Moscow and SRON Netherlands Institute for Space Research. It will use a passively cooled deployable antenna with a high-precision central 3.5m diameter mirror and high- precision antenna petals. The antenna is specified for observations up to ~2 THz over the whole 12m diameter, and to higher frequencies using the central 3.5m solid mirror. Millimetron will be operated in two basic observing modes: as a single-dish observatory, and as an element of a ground-space VLBI system. As single-dish, angular resolutions on the order of 3 to 12 arcsec will be achieved and spectral resolutions of up to 10 6 employing heterodyne techniques. As VLBI antenna, the chosen elliptical orbit will provide extremely large VLBI baselines resulting in micro-arcsec angular resolution. The scientific payload will consist of heterodyne and direct detection instruments covering the most important sub-/millimeter spectral regions (including some ALMA bands) and will build on the Herschel and ALMA heritage.