An ultra-wideband, large field-of-view (sub)millimeter wave imaging spectrometer is imperative for uncovering the evolution of dust-enshrouded cosmic star formation rate, galaxy evolution, and structure formation, over cosmic time. Here we report the first on-sky demonstration of DESHIMA. DESHIMA (Deep Spectroscopic High-redshift Mapper) is a new type of submillimeter wave spectrometer, which uses a superconducting filterbank on a chip to achieve a very wide instantaneous bandwidth. Compared to an optical spectrometer with equivalent performance, such an on-chip spectrometer is not only compact, but also offers a higher degree of potential scalability to multiple spatial pixels. On the filterbank spectrometer chip of DESHIMA, the signal captured by the lens-antenna travels through a coplanar waveguide made of superconducting NbTiN, from which planar NbTiN bandpass filters branch out to divide the signal into frequency channels. At the output of each filter is a NbTiN/Al hybrid kinetic inductance detector (KID). These KIDs are operated at 120 mK with a 2-stage adiabatic demagnetization refrigerator (ADR), and their response is read out using the SpaceKIDs readout electronics. Being in its phase-1 configuration, DESHIMA currently covers the 330-370 GHz band with 49 spectral channels, offering a spectral resolution F/dF = 400, or dV = 700 km/s. This design is intended as a scalable prototype towards the phase-2 DESHIMA instrument, which targets at 240-720 GHz instantaneous band coverage with a resolution of F/dF = 500 (dV = 600 km/s), and >2 spatial pixels. In the laboratory, the sensitivity and frequency response of DESHIMA was characterized using a black-body calibration source and a THz photo-mixer source, respectively. The sensitivity is photon-noise limited at a detector loading power of ~1 pW, with a photon-noise limited optical Noise Equivalent Power of 1-2 x 10^-16 W Hz^-0.5. From October to November 2017, DESHIMA was installed on the Atacama Submillimeter Telescope Experiment (ASTE), a 10 m diameter antenna in the Atacama Desert of Chile. The sensitivity of DESHIMA measured inside the ASTE cabin is similar to lab results. At the time of submission of the abstract, DESHIMA has successfully detected multiple astronomical sources, in both continuum and line emission. At the conference we will report the lessons learned in the first actual operation of an on-chip filterbank spectrometer on a telescope, including the influence of thermal cycles on the filters, system susceptibility to telescope environment and motion, on-sky beam pattern, and sensitivity to continuum and line emission.
We report on a plan to construct a 50-m-class single-dish telescope, the Large Submillimeter Telescope (LST). The conceptual design and key science behind the LST are presented, together with its tentative specifications. This telescope is optimized for wide-area imaging and spectroscopic surveys in the 70-420 GHz frequency range, which spans the main atmospheric windows at millimeter and submillimeter wavelengths for good observation sites such as the Atacama Large Millimeter/submillimeter Array (ALMA) site in Chile. We also target observations at higher frequencies of up to 1 THz, using an inner high-precision surface. Active surface control is required in order to correct gravitational and thermal deformations of the surface, and will be useful for correction of the wind-load deformation. The LST will facilitate new discovery spaces such as wide-field imaging with both continuum and spectral lines, along with new developments for time-domain science. Through exploitation of its synergy with ALMA and other telescopes, the LST will contribute to research on a wide range of topics in the fields of astronomy and astrophysics, e.g., astrochemistry, star formation in our Galaxy and galaxies, the evolution of galaxy clusters via the Sunyaev-Zel'dovich (SZ) effect, the search for transients such as γ-ray burst reverse shocks produced during the epoch of re-ionization, electromagnetic follow up of detected gravitational wave sources, and examination of general relativity in the vicinity of super massive black holes via submillimeter very-long-baseline interferometry (VLBI).
We have developed a 30-cm submillimeter-wave telescope intended to survey the Milky Way in 500 GHz emission lines at the Dome Fuji station in Antarctic plateau. Transportability and low power consumption are required while keeping low system noise temperature for the operation in Antarctica. The telescope is designed to be divided into five components and to operate with less than 2.5 kW of electric power. Its receiver noise temperature is less than 85 K in SSB at 461 and 492 GHz. We succeeded in operating the telescope at -30◦C in laboratory that is a typical temperature of the Dome Fuji in summer.