We present a plan for sub/millimeter-wave line intensity mapping (LIM) using an imaging spectrograph based on the Terahertz Integral Field Units with Universal Nanotechnology (TIFUUN) architecture. We aim to measure the dust-enshrouded cosmic star formation rate density within the first 2 billion years by conducting LIM observations of ionized carbon [C II] 158 μm and oxygen [O III] 88 μm lines, redshifted to sub/millimeter wavelengths. The proposed imaging spectrograph will simultaneously observe two frequency bands: Band-1 (139-179 GHz) and Band-2 (248-301 GHz). Each band will feature up to ∼100 imaging pixels (spaxels), with each spaxel having 100 spectral channels, providing a modest spectral resolution (R~500). The total number of detectors (voxels) will reach ~20,000. This dual-band configuration will allow simultaneous measurement of key spectral lines, e.g., [C II] 158 μm and [O III] 88 μm lines at z = 10.2 - 12.6, and CO(4-3), (7-6), [C I](1-0) and (2-1) at z = 1.9 - 2.2, enabling cross-correlation analysis. We will develop data-scientific methods to remove atmospheric noise using sparse modeling and to extract signals from the observed data using deep learning.

We present the on-sky commissioning and science verification of DESHIMA 2.0: the first science-grade integrated superconducting spectrometer (ISS) for ultra-wideband mm-submm spectroscopy. With an instantaneous band coverage of 205-392 GHz at a spectral resolution of F/dF = 500, DESHIMA 2.0 will be applied to emission line surveys and redshift measurement of dusty star-forming galaxies, spectroscopic Sunyaev–Zeldovich effect observations of galaxy-clusters, and other new science cases that utilize its ultra-wide bandwidth. Compared to its predecessor (DESHIMA 1.0), DESHIMA 2.0's superconducting filterbank chip with a x4 higher optical efficiency, x4 wider instantaneous bandwidth, x20 faster position switching on the sky, and a remotely-controlled optics alignment system. DESHIMA 2.0 is currently installed on the ASTE 10-m telescope at 4860 m altitude with excellent sky transmission, and is being commissioned for science operation. In the conference we will report the on-sky performance and latest results in the science-verification campaign at ASTE.

Integrated superconducting spectrometer (ISS) technology will enable ultra-wideband, integral-field spectroscopy for (sub)millimeter-wave astronomy, in particular, for uncovering the dust-obscured cosmic star formation and galaxy evolution over cosmic time. Here we present the development of DESHIMA 2.0, an ISS for ultra-wideband spectroscopy toward high-redshift galaxies. DESHIMA 2.0 is designed to observe the 220-440 GHz band in a single shot, corresponding to a redshift range of z=3.3-7.6 for the ionized carbon emission ([C II] 158 μm). The first-light experiment of DESHIMA 1.0, using the 332-377 GHz band, has shown an excellent agreement among the on-sky measurements, the lab measurements, and the design. As a successor to DESHIMA 1.0, we plan the commissioning and the scientific observation campaign of DESHIMA 2.0 on the ASTE 10-m telescope in 2023. Ongoing upgrades for the full octave-bandwidth system include the wideband 347-channel chip design and the wideband quasi-optical system. For efficient measurements, we also develop the observation strategy using the mechanical fast sky-position chopper and the sky-noise removal technique based on a novel data-scientific approach. In the paper, we show the recent status of the upgrades and the plans for the scientific observation campaign.

The next technological breakthrough in millimeter-submillimeter astronomy is 3D imaging spectrometry with wide instantaneous spectral bandwidths and wide fields of view. The total optimization of the focal-plane instrument, the telescope, the observing strategy, and the signal-processing software must enable efficient removal of foreground emission from the Earth's atmosphere, which is time-dependent and highly nonlinear in frequency. Here we present TiEMPO: Time-Dependent End-to-End Model for Post-process Optimization of the DESHIMA Spectrometer. TiEMPO utilizes a dynamical model of the atmosphere and parametrized models of the astronomical source, the telescope, the instrument, and the detector. The output of TiEMPO is a time-stream of sky brightness temperature and detected power, which can be analyzed by standard signal-processing software. We first compare TiEMPO simulations with an on-sky measurement by the wideband DESHIMA spectrometer and find good agreement in the noise power spectral density and sensitivity. We then use TiEMPO to simulate the detection of a line emission spectrum of a high-redshift galaxy using the DESHIMA 2.0 spectrometer in development. The TiEMPO model is open source. Its modular and parametrized design enables users to adapt it to design and optimize the end-to-end performance of spectroscopic and photometric instruments on existing and future telescopes.

We are developing an ultra-wideband spectroscopic instrument, DESHIMA (DEep Spectroscopic HIgh-redshift MApper), based on the technologies of an on-chip filter bank and microwave kinetic inductance detector (MKID) to investigate dusty starburst galaxies in the distant universe at millimeter and submillimeter wavelengths. An on-site experiment of DESHIMA was performed using the ASTE 10-m telescope. We established a responsivity model that converts frequency responses of the MKIDs to line-of-sight brightness temperature. We estimated two parameters of the responsivity model using a set of skydip data taken under various precipitable water vapor (PWV 0.4–3.0 mm) conditions for each MKID. The line-of-sight brightness temperature of sky is estimated using an atmospheric transmission model and the PWVs. As a result, we obtain an average temperature calibration uncertainty of $$1\sigma =4$$%, which is smaller than other photometric biases. In addition, the average forward efficiency of 0.88 in our responsivity model is consistent with the value expected from the geometrical support structure of the telescope. We also estimate line-of-sight PWVs of each skydip observation using the frequency response of MKIDs and confirm the consistency with PWVs reported by the Atacama Large Millimeter/submillimeter Array.

The integrated superconducting spectrometer (ISS) enables ultra-wideband, large field-of-view integral-field-spectrometer designs for mm-submm wave astronomy. DESHIMA 2.0 is a single-pixel ISS spectrometer for the ASTE 10-m telescope, designed to observe the 220-440 GHz band in a single shot, corresponding to a [CII] redshift range of z=3.3-7.6. The first-light experiment of DESHIMA, using a 332-377 GHz configuration has shown excellent consistency between the performance derived from on-sky measurements, lab-measurements and the design. Ongoing upgrades towards the octave-bandwidth full system include the development of a filterbank chip with ~350 channels and higher optical efficiency, a wideband quasioptical design, and observing methods for efficiently removing the atmosphere.

Terahertz spectrometers with a wide instantaneous frequency coverage for passive remote sensing are enormously attractive for many terahertz applications, such as astronomy, atmospheric science, and security. Here we demonstrate a wide-band terahertz spectrometer based on a single superconducting chip. The chip consists of an antenna coupled to a transmission line filterbank, with a microwave kinetic inductance detector behind each filter. Using frequency division multiplexing, all detectors are read-out simultaneously, creating a wide-band spectrometer with an instantaneous bandwidth of 45 GHz centered around 350 GHz. The spectrometer has a spectral resolution of F / ΔF = 380 and reaches photon-noise limited sensitivity. We discuss the chip design and fabrication, as well as the system integration and testing. We confirm full system operation by the detection of an emission line spectrum of methanol gas. The proposed concept allows for spectroscopic radiation detection over large bandwidths and resolutions up to F / ΔF ∼ 1000, all using a chip area of a few cm2. This will allow the construction of medium resolution imaging spectrometers with unprecedented speed and sensitivity.

Ultra-wideband, three-dimensional (3D) imaging spectrometry in the millimeter–submillimeter (mm–submm) band is an essential tool for uncovering the dust-enshrouded portion of the cosmic history of star formation and galaxy evolution1–3. However, it is challenging to scale up conventional coherent heterodyne receivers4 or free-space diffraction techniques5 to sufficient bandwidths (≥1 octave) and numbers of spatial pixels2,3 (>102). Here, we present the design and astronomical spectra of an intrinsically scalable, integrated superconducting spectrometer6, which covers 332–377 GHz with a spectral resolution of F/ΔF ~ 380. It combines the multiplexing advantage of microwave kinetic inductance detectors (MKIDs)7 with planar superconducting filters for dispersing the signal in a single, small superconducting integrated circuit. We demonstrate the two key applications for an instrument of this type: as an efficient redshift machine and as a fast multi-line spectral mapper of extended areas. The line detection sensitivity is in excellent agreement with the instrument design and laboratory performance, reaching the atmospheric foreground photon noise limit on-sky. The design can be scaled to bandwidths in excess of an octave, spectral resolution up to a few thousand and frequencies up to ~1.1 THz. The miniature chip footprint of a few cm2 allows for compact multi-pixel spectral imagers, which would enable spectroscopic direct imaging and large-volume spectroscopic surveys that are several orders of magnitude faster than what is currently possible1–3. By using a superconducting integrated circuit to filter incoming millimetre, submillimetre and far-infrared light from distant galaxies, a prototype spectrometer holds promise for wideband spectrometers that are small, sensitive and scalable to wideband spectroscopic imagers.

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.

In the process to develop the transition edge sensor (TES) bolometer technology for the SAFARI FIR Imaging Spectrometer on the SPICA telescope and for future FIR space telescopes, we have recently demonstrated a TiAu TES with a Ta thin film absorber on a thin SiN membrane, which has a dark NEP as low as 4.2 × 10-19 W/√Hz. It is known that superconductors are sensitive to magnetic fields. Therefore, it is important to know how these extremely sensitive TES detectors are affected by external magnetic fields. This is desirable from an application point of view since the design of the SAFARI instrument demands such knowledge and interesting from a fundamental point of view. In this paper, we will describe a detailed experimental study of the effects of magnetic fields, both parallel and perpendicular to the TiAu plane, on the performance of a TES. We investigated the effect on the current, responsivity, speed, and TES parameters of α (dependence of temperature) and β (dependence of current), around the operating points. In order to achieve this highly sensitive measurement, the temperature stability has been improved and a new coil assembly has been designed. The latter allows accurately applying a parallel magnetic field.