NASA's Planetary Science Decadal Survey has concluded that isotopic measurements of cometary water vapor are a means to unraveling the mysteries involving the origin of Earth's water and the evolution of our solar system. To support this, a recent Jet Propulsion Laboratory internal research program has developed quantum limited superconductor-insulator-superconductor (SIS) receivers in the important 500-600 GHz submillimeter frequency band. These instruments can be used to detect the deuterated water (HDO) ground state (110-101), H216O ortho ground state (110-101), and the oxygen isotopologues H217O and H218O with exquisite sensitivity. To achieve the presented results, we have investigated aluminum oxide (AlOx) and aluminum nitride (AlNx) barrier SIS tunnel junction mixers on the 6-μm silicon-on-insulator substrate. The AlOx and AlNx junction mixer blocks utilize diagonal and smooth-profile conical horns, respectively. In both cases, a commercial 4-8-GHz intermediate frequency low-noise amplifier (LNA) has been integrated into the mixer block. The AlOx (low-current-density) barrier SIS junctions were fabricated with 2-μm gold beam-lead technology, whereas in the case of the AlNx SIS tunnel junction, we use capacitive RF decoupling tabs. The latter approach simplifies fabrication, increases yield, eases the mounting process, and facilitates scaling to higher frequencies. For an actual flight mission, with operation ≤4.2 K, the allowed heat dissipation of the mixer-integrated LNA needs to be minimized. In this article, we also investigate the receiver sensitivity as a function of the LNA dc power consumption. We find that the dc power consumption of the LNA can be reduced to ∼1.6 mW with minimal loss in sensitivity. It is anticipated that the continued InP HEMT development for quantum computer applications are likely to reduce the required LNA power dissipation even further.

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We present observations of the Trumpler 14/Carina I region carried out using the Stratospheric Terahertz Observatory 2. The Trumpler 14/Carina I region is in the western part of the Carina Nebula Complex (CNC), which is one of the most extreme star-forming regions in the Milky Way. We observed Trumpler 14/Carina I in the 158 μm transition of [C ii] with a spatial resolution of 48″ and a velocity resolution of 0.17 km s^-1. The observations cover a 0.25 by 0.28 area with central position l = 297.34, b = -0.60. The kinematics show that bright [C ii] structures are spatially and spectrally correlated with the surfaces of CO clouds, tracing the photodissociation region (PDR) and ionization front of each molecular cloud. Along seven lines of sight (LOSs) that traverse Tr 14 into the dark ridge to the southwest, we find that the [C ii] luminosity from the H ii region is 3.7 times that from the PDR. In the same LOS, we find in the PDRs an average ratio of 1 : 4.1 : 5.6 for the mass in atomic gas : dark CO gas : molecular gas traced by CO. Comparing multiple gas tracers, including H i 21 cm, [C ii], CO, and radio recombination lines, we find that the H ii regions of the CNC are well described as H ii regions with one side freely expanding toward us, consistent with the Champagne model of ionized gas evolution. The dispersal of the GMC in this region is dominated by EUV photoevaporation; the dispersal timescale is 20-30 Myr.

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We present the design of a dielectric lens to correct the spherical aberration in spherical reflector antennas for use at centimeter through submillimeter wavelengths. A set of near-field measurements at a frequency of 100 GHz of a 30 cm diameter spherical antenna with 30 cm radius of curvature confirm improvement in illumination efficiency from 20.2% for the feed at the paraxial focus of the spherical primary to 42.4% with the feed position optimized as described by [M. Alonso-DelPino, P. Goldsmith, C. Elmaleh, T. Reck, and G. Chattopadhyay, 'Efficiency optimization of spherical reflectors by feed position adjustments,' IEEE Antennas and Wireless Propagation Letters, vol. 16, pp. 2865-2868, 2017] to 53.1% with the present TPX corrective lens. Further improvement should be possible by antireflection treatment of the lens surfaces, and by using both lens surfaces to optimize the amplitude in addition to the phase distribution of the antenna illumination. This technique offers advantages for antenna systems used for communication and for a variety of remote sensing applications.@en

This letter presents a numerical study of the best performance achievable using a spherical reflector with a point feed and without any corrective element. We evaluate in detail the aperture efficiency that can be obtained with a spherical reflector with linearly polarized Gaussian beam illumination. A 100 GHz, 30 cm diameter spherical reflector from a parent sphere of 30 cm radius has been built and measured. The maximum directivity of 46.1 dB agrees closely with the predictions of electromagnetic modeling, as does the increase in the directivity by more than 3 dB resulting from moving the feed by 0.7 cm closer to the reflective surface relative to the paraxial focal point.@en