ABSTRACT. This contribution will present the overall instrument concept of the heterodyne array receiver for the Line Emission Terahertz Observatory (LETO), an ESA M8 mission proposal. The heterodyne receiver has 4 bands between 450 GHz and 5.3 THz. Each band has at least 8 mixers with a goal of 16. The major challenges are to design a performant instrument for point source observations as well as for large area mapping. Another challenge is to keep mass, volume, power and cooling requirements within the scope of an M-class mission.

ABSTRACT. This paper reports on the development and characterization of a compact 2.06 THz all-solid-state Schottky receiver prototype, which integrates a subharmonic mixer, LO and IF chains, and a CMOS spectrometer to meet rigorous mission requirements. The receiver demonstrates robust performance at room temperature with a Double Sideband (DSB) equivalent noise temperature below 7000 K and high stability, achieving an Allan time of 35 s. Furthermore, retrieval algorithms confirm the system's capability for precision wind velocity measurements, paving the way for future extensions to multi-spacecraft constellations.

ABSTRACT. The Arctic Weather Satellite (AWS) is a meteorological satellite from the European Space Agency (ESA) carrying a microwave radiometer that operates at four frequency bands: 54, 89, 183 and 325 GHz. During the commissioning phase, the satellite performed a pitch-over maneuver. In this maneuver, the satellite scanned through the cold sky, allowing the characterization of scan biases due to reflector far-sidelobes, spillover, and reflector losses. In this work, we focus on the reflector losses and their variation due to polarization rotation while scanning. We compare the pitch maneuver observations with measurements performed on a sample of the AWS reflector using a microwave resonator. Finally, we assess their impact on radiometric calibration.

ABSTRACT. ESO has supported ALMA development in its member state institutes since 2010. These studies aim to maintain ALMA at the forefront of sub/mm technology. During the first decade, a range of studies have led to projects implementing Bands 5 and 2, the last two rounds are instead directed towards the implementation of the technological challenges of the wideband sensitivity upgrade (WSU). In this presentation, I will present an overview of the ongoing and upcoming ESO ALMA development studies covering a wide range of topics from receiver components to software development aiming towards an efficient implementation of the WSU.

ABSTRACT. We have enhanced the harmonic-balance (HB) frequency-domain simulations to calculate more accurately the image rejection and single sideband (SSB) noise for the upgraded ALMA Band 6 (Band 6v2) sideband separating (2SB) receiver. Improvements include new measured components of RF section of the receiver and the inclusion of individual frequency-dependent Superconductor-Insulator-Superconductor (SIS) mixer parameters derived from measured SIS I-V curves.

ABSTRACT. We present the design concept of the Band 1 array receiver for the Line Emission Terahertz Observatory (LETO), based on mature superconductor–insulator–superconductor (SIS) mixer technology. The baseline receiver covers 450–570 GHz, targeting key molecular and isotopic transitions including HDO 110→000, H18 2 O 110→101, 13CO J=5→4 and H2O 110→101, while a goal configuration extends the bandwidth to 820 GHz to enable observations of the [CI] 370µm line. We describe the SIS mixer chip designs and discuss the challenges of extending performance beyond 680 GHz due to increased losses in niobium transmission lines. The array architecture is also presented, demonstrating flexible, electronically reconfigurable operation in single- and dual-polarisation observing modes.

ABSTRACT. The Submillimeter Wave Instrument (SWI) onboard ESA’s JUpiter ICy moons Explorer (JUICE) mission is a heterodyne spectrometer tunable over two frequency bands centered around 600 GHz and 1.2 THz. The instrument was launched in April 2023 and is designed to investigate Jupiter’s stratosphere as well as the atmospheres and surfaces of the Galilean moons during the nominal science phase from 2031 to 2034. During the Lunar–Earth Gravity Assist (LEGA) maneuver in August 2024, the SWI instrument performed observations of the lunar surface and Earth’s atmosphere. In this contribution, we compare these observations with the modeled antenna response and with simulated atmospheric spectra.

ABSTRACT. The OSAS-B instrument is a balloon-based heterodyne spectrometer for measuring atomic oxygen in the mesosphere and lower thermosphere. The dual-channel version of the receiver measures both terahertz transitions at 2.1 and 4.7 THz. It comprises a superconducting hot-electron bolometer as a mixer, a multiplier-based local oscillator for 2.1 THz and a quantum-cascade laser for 4.7 THz. The first flight with a stratospheric balloon took place in August 2025 in Timmins, Canada.

ABSTRACT. We present a new class of stacked dielectric optical diplexers enabling simultaneous multi-band, dual-polarization operation in millimeter and submillimeter astronomical receivers. These devices overcome key limitations of conventional dichroics by providing low loss, wide angle-of-incidence tolerance, and immunity to Wood’s anomalies. As part of the tri-band receiver architecture for the next-generation Event Horizon Telescope (ngEHT), two diplexers are implemented: an ambienttemperature diplexer separating the 86 - 115 GHz and 230 - 345 GHz bands, and a cryogenic diplexer dividing the 230 and 345 GHz bands. Performance is validated through hot-cold load tests, quasi-optical VNA measurements, and a comb-injection technique. Results demonstrate a robust, low-loss multiplexing solution suitable for wideband, multi-frequency instrumentation in current and future millimeter and submillimeter telescopes.

ABSTRACT. A cryogenically compatible waveguide 3-dB power divider for ALMA Band 7 (275–373 GHz) is presented for sideband-separating (2SB) SIS receivers. The divider provides equal-amplitude LO drive with reduced insertion loss, reflections, and inter-port coupling that limit image rejection. The design is a modified E-plane T-junction incorporating an integrated matched termination that absorbs reflected power and suppresses output crosstalk. Re-optimised from lower-frequency concepts, this implementation targets Band-7 tolerances and cryogenic integration and employs thin-film lumped loading elements for broadband matching/isolation. The device is fabricated by split-block waveguide machining and thin-film microfabrication of a quartz termination chip. Room-temperature VNA measurements show low excess loss beyond the ideal 3 dB split, return loss >18 dB at all ports over most of the band, and output isolation >15 dB, confirming suitability for ALMA Band-7 2SB receivers.

ABSTRACT. The Habitable Worlds Observatory (HWO)—NASA’s next-generation ultraviolet/optical/infrared space telescope—requires detector readout electronics capable of processing extremely wide-bandwidth data from large Microwave Kinetic Inductance Detector (MKID) arrays. MKIDs, which employ frequency-division multiplexing, have demonstrated scalability in sub-orbital missions using FPGA-based architectures. To extend this capability to spaceflight, this work presents a high-speed polyphase filterbank (PFB) implementation optimized for real-time MKID readout in radiation-tolerant FPGA environments. The PFB serves as the primary coarse channelization stage in the HWO readout chain, converting digitized signals into finely resolved frequency bins while minimizing spectral leakage and inter-channel crosstalk. A fixed-point digital design methodology for a critically sampled PFB was developed in MATLAB Simulink and implemented on an AMD Kintex UltraScale FPGA. The design employs a time-multiplexed 4-tap prototype filter combined with a 1024-point FFT, achieving 10 kHz frequency resolution across a 2.4 GHz science bandwidth at 5 GHz sampling. Simulation and hardware tests demonstrate greater than 50 dB channel isolation, efficient resource utilization, and scalability for large-format MKID arrays. These advancements directly address the signal-processing needs of HWO and future space-based astrophysics missions.

ABSTRACT. The frequency multiplexing of Microwave Kinetic Inductance Detectors (MKIDs) enables the construction of cameras with thousands of detectors. One of these cameras is the A-MKID camera at the 12 meter submm-telescope Atacama Pathfinder Experiment (APEX) in Chile. The U-Board provides a heterogeneous processing architecture for radio astronomy. It combines signal generation and acquisition, as well as a Field Programmable Gate Array (FPGA) and a General Purpose Graphics Processing Unit (GPGPU) for the signal processing. On the basis of this architecture, an MKID readout for the A-MKID camera was developed. Here, we present the readout itself, as well as the beginning of the commissioning of the readout on sky.

ABSTRACT. We demonstrate, for the first time, a monolithic dual-polarization sideband-separation SIS mixer operating at 2 mm wavelengths (125–163 GHz) based on a silicon substrate. The integrated SIS mixer achieves a sideband rejection ratio exceeding 10 dB and a single-sideband receiver noise temperature of 80–120 K over a 4–8 GHz IF band across most of the RF range. This SIS chip, serving as a key component of the hybrid planar integration method, clarifies the feasibility of realizing large-format heterodyne arrays, which can significantly expand the field of view of millimeter and sub-millimeter radio telescopes.

ABSTRACT. The Black Hole Explorer (BHEX) mission, a Space Very Long Baseline Interferometry (VLBI) requires a low-noise millimeter-wave receiver to achieve the goal of black hole photon-ring imaging. We report the design and performance evaluation of a prototype 300-GHz-band Superconductor–Insulator–Superconductor (SIS) mixer developed for this mission. An SIS mixer with an Aluminum oxide tunnel barrier was fabricated, achieving a critical current density of 12 kA/cm2. Intermediate-frequency spectra were measured at 285 GHz, and a double-sideband (DSB) noise temperature of 30 K was achieved over the 4–9 GHz IF band. This performance corresponds to twice the quantum noise limit, demonstrating the technological maturity of low-noise SIS mixers operating in the 300-GHz band.

ABSTRACT. In this study we present the superconductor terahertz-range local oscillator based on the arrays of Josephson junctions connected in series and embedded into the central electrode of the coplanar line. The chosen topology allowed to fabricate the local oscillator for superconductor integrated receiver with frequency tuning over the entire frequency range from 100 GHz up to 700 GHz limited only by the matching circuit characteristics. The linewidth was less than 1 MHz in the best points which allowed the phase-locking of the array to the external stable synthesizer. Theoretical estimate of the linewidth using the model for the junction with the shunt resistor is in qualitative agreement with the experiment. We also suggest the model for the synchronization phenomena between the junctions in the array.

ABSTRACT. Large-scale superconducting transition-edge sensor arrays, suitable for the detection of primordial gravitational waves, require multiplexing readout techniques. Microwave SQUID multiplexing (uMUX) is promising since it works with ~GHz bandwidth and provides a high multiplexing factor. We present a 60-channel uMUX modular design based on 16-channel chips including weak and strong coupling structures. The resonator bandwidth and maximum frequency shift are about 520 kHz and 302 kHz for the weak coupling structures. The median open-loop white current noise is ~60 pA/√Hz, subdominant to the noise of TES bolometers.