Omnisys Instruments (Sweden)

Abstract. The Arctic Weather Satellite (AWS) is a project led by the European Space Agency (ESA) that has several novel aspects. From a technical perspective, it serves as a demonstrator of how to expand the network of operational satellite-based microwave sensors cost-effectively and acts as the proto-flight model for a suggested constellation of satellites, denoted as EUMETSAT Polar System (EPS) Sterna. The design philosophy has been to reduce complexity and instead focus the efforts on critical parts and characterise the instrument well before the launch. The single instrument onboard is a 19-channel microwave cross-track radiometer. There are 15 channels covering ranges around 54, 89 and 174 GHz. These are channels similar to ones found on existing sensors, however, thanks to the short development process, allowing use of more modern and recent technology, the performance and resolution of these channels on AWS exceed or match similar sensors, despite being a small satellite. Additionally, four channels around 325.15 GHz form a completely new frequency band for observations from space. The addition of these new channels aims to improve sensitivity to ice hydrometeors. In this article, we outline the mission and describe the instrument in detail, to support the usage of radiances measured by AWS. The satellite was launched in August 2024, and the status towards the end of the commissioning phase is reflected here. For example, a characterisation of the noise performance is provided, showing that the target specifications have been met, for most channels with a margin. This is except for two channels identified to have technical issues already before the launch. If EPS-Sterna is selected by EUMETSAT, these and other identified problems will be corrected, but otherwise the constellation is expected to consist of recurrent models of AWS with minor modifications.

Abstract. The Arctic Weather Satellite (AWS) is a project led by the European Space Agency (ESA) that has several novel aspects. From a technical perspective, it serves as a demonstrator of how to expand the network of operational satellite-based microwave sensors cost-effectively and acts as the proto-flight model for a suggested constellation of satellites, denoted as EUMETSAT Polar System (EPS) Sterna. The design philosophy has been to reduce complexity and instead focus the efforts on critical parts and characterise the instrument well before the launch. The single instrument onboard is a 19-channel microwave cross-track radiometer. There are 15 channels covering ranges around 54, 89 and 174 GHz. These are channels similar to ones found on existing sensors, however, thanks to the short development process, allowing use of more modern and recent technology, the performance and resolution of these channels on AWS exceed or match similar sensors, despite being a small satellite. Additionally, four channels around 325.15 GHz form a completely new frequency band for observations from space. The addition of these new channels aims to improve sensitivity to ice hydrometeors. In this article, we outline the mission and describe the instrument to support the usage of radiances measured by AWS. The satellite was launched in August 2024, and the status towards the end of the commissioning phase is reflected here. For example, a characterisation of the noise performance is provided, showing that the target specifications have been met, for most channels with a margin. This is except for two channels identified to have technical issues already before the launch. If EPS-Sterna is selected by EUMETSAT, these and other identified problems will be corrected, but otherwise the constellation is expected to consist of recurrent models of AWS with minor modifications.

The Arctic Weather Satellite (AWS) is a prototype mission for an operational constellation of microwave sounders, complimenting existing meteorological sounders. The AWS is a microsatellite with a single cross-track scanning radiometer operating in the 54, 89, 183 and 325 GHz bands. Due to the small platform size, the core design focus of the radiometer’s quasi-optics is less complexity and a more compact setup than comparable spaceborne microwave sounders. To achieve this, the instrument utilises a splitblock feedarray which directly illuminates the off-axis parabolic scanning reflector. A secondary parabolic reflector is used to couple into a wedge-shaped load which is used for calibration in combination with cold sky measurements. The main challenge for instrument performance is that only one of the four horns can be located in the focus of the scanning reflector. Consequently, scan angle dependent spillover variations and beam asymmetries can occur. This paper details the simulation and optimisation efforts of the quasi-optics to minimise the aforementioned effects.

A high spectral resolution airborne microwave sounder has been developed by Omnisys Instruments in collaboration with the National Research Council Canada (NRC) and McGill University from a European Space Agency (ESA) funding. Two single sideband radiometers have been designed with different operating frequency range, 50 – 58 GHz and 176.3 – 184.3 GHz, observing the H and V polarizations. Each unit is composed of two heterodyne receivers combined with 2 polyphase digital Fast Fourier Transform spectrometers with 5 GHz bandwidth, with up to 16384 channels. The microwave sounder presents system noise temperatures below 250K and 850 K for the 54 GHz band and 183 GHz band, respectively. The two units have been installed onboard the NRC Convair-580 research aircraft for high spectral resolution remote sensing of the atmosphere

Ribonucleotide reductases (RNRs) are key enzymes in DNA metabolism, with allosteric mechanisms controlling substrate specificity and overall activity. In RNRs, the activity master-switch, the ATP-cone, has been found exclusively in the catalytic subunit. In two class I RNR subclasses whose catalytic subunit lacks the ATP-cone, we discovered ATP-cones in the radical-generating subunit. The ATP-cone in the Leeuwenhoekiella blandensis radical-generating subunit regulates activity via quaternary structure induced by binding of nucleotides. ATP induces enzymatically competent dimers, whereas dATP induces non-productive tetramers, resulting in different holoenzymes. The tetramer forms by interactions between ATP-cones, shown by a 2.45 Å crystal structure. We also present evidence for an MnIIIMnIV metal center. In summary, lack of an ATP-cone domain in the catalytic subunit was compensated by transfer of the domain to the radical-generating subunit. To our knowledge, this represents the first observation of transfer of an allosteric domain between components of the same enzyme complex.

We present a novel waveguide-to-suspended stripline loop-probe transition operating over the entire WR-1.0 waveguide band. The loop probe is designed for broadband response with simulated RL > 15 dB, and has an integrated DC return path, which can also be extended for biasing. The measured insertion loss for a back-to-back configuration is 1–2 dB in almost the entire frequency range of 750–1100 GHz.

We report on a heterodyne terahertz spectrometer based on a fully integrated 557-GHz receiver and a digital fast Fourier transform spectrometer. The receiver consists of a chain of multipliers and power amplifiers, followed by a heterostructure barrier varactor tripler that subharmonically pumps a membrane GaAs Schottky diode mixer. All sub-components are newly developed and optimized with regard to the overall receiver performance such as noise temperature, power consumption, weight and physical size. The receiver works at room temperature, has a double sideband noise temperature as low as 2000 K at a maximum power consumption of 4.5 W with an Allan time of 10 s and a sideband gain ratio of 0.52. The performance of the spectrometer is demonstrated by absorption spectroscopy of H <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> O and CH <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex></formula> OH with an instantaneous bandwidth of 1.5 GHz and a resolution of 183 kHz. Several pressure broadening parameters of methanol absorption lines were determined, that agree with other published data. Using the experimentally determined molecular parameters the CH <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{3}$</tex> </formula> OH absorption spectrum could be modeled with very high precision.

The cluster of differentiation (CD) 44v6 antigen has been suggested to be involved in tumor formation, invasion, and metastasis formation, and has been observed in a majority of primary and metastatic squamous cell carcinomas of the head and neck. Probes specifically binding to this region may be utilized as tools for the challenging tasks of early detection and targeted treatments of small residual disease. In this project, an epitope-guided phage display selection of human fragment antigen-binding (Fab) fragments with affinity to the v6 sequence was performed. A selected set of Fab fragments was shown to specifically recognize increasingly complex forms of the target sequence, both in the form of a short synthetic or recombinant peptide and in the context of a purified extracellular domain of CD44. The binding was independent of known v6-sequence variation and posttranslational modifications that are common in the CD44 protein family. Furthermore, real-time interaction measurements on antibody fragments labeled with ¹²⁵I showed specific and high-affinity binding to the antigen present on cultured head and neck squamous cell carcinoma cells. There was no cross-reactivity toward cells that lack the target protein. As hypothesized, characterization of the interaction between Fab fragments and the targets using the mathematical tool Interaction Map revealed more heterogeneous interactions on cells than with pure proteins analyzed by surface plasmon resonance. One main candidate Fab fragment with optimal affinity for all forms of the target sequence was identified. The flexible recombinant source of the Fab fragments might aid the development of tailored molecules adapted for therapeutic or diagnostic applications in the future.

In this letter, we present results of fully integrated 90-130 GHz receiver based on 100 nm mHEMT technology. The receiver contains a low noise amplifier (LNA), mixer and LO multiplier chain integrated into a single monolithic microwave integrated circuit (MMIC). The circuit is packaged into a waveguide block, characterized and compared to on-wafer measurements. Waveguide to microstrip transitions are used to interface the MMIC to the waveguide. A breakout LNA circuit is also packaged, and its performance is compared to the receiver. The LNA noise was characterized on a wafer and after packaging. The packaged module is measured at both room and cryogenic temperatures, NF of 3.7 dB is measured at 300 K and 0.9 dB at 20 K.

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