From the optical characteristics of Herschel-hifi to in-orbit spatial response calibration using Mars

Making use of all Mars observations taken by Herschel-HIFI, we present a detailed comparison of the measured and predicted beam profiles observed in space. Starting with a number of instrument beam profile models, including one based on actual wavefront measurements in the 480-1625 GHz frequency range, we developed a forward model predicting the detailed characteristics of the beam profile at the sky. Once convolved with the actual brightness temperature distribution and appearance of Mars, this forward model can be compared in detail with the observed spatial response towards Mars, using the science data of HIFI. Since the HIFI instrument is a single-mode coherent receiver, and given the availability of phase-sensitive measurements at instrument level, the results suggest that it is possible to extract some interesting optical characteristics of the Herschel telescope in addition. We discuss a possible way to extract the location of the telescope focus from these observations, which could provide useful feedback to the thermo-elastic properties of the SiC telescope assembly under zero-g and cryogenic conditions.</p

Open data and smallholder food and nutritional security

This report was commissioned CTA as a member of the GODAN initiative. It aims to provide a better understanding of the actual impact of the open data movement on the food and nutrition security of smallholders and highlight the areas of potential unfilled opportunity

1958 Payton Lectures: Faith and Reason in Philosophy

Fuller Theological Seminary instituted the Payton Lectures in 1948, providing for a series of divinity lectures by a notable scholar outside the regular faculty. The lectureship is named for Dr. John E. and Mrs. Eliza Payton, parents of the late Mrs. Grace Fuller, wife of seminary founder Charles E. Fuller. El Seminario Teológico de Fuller instituyó las Conferencias Payton en 1948, proveyendo una serie de conferencias en divinidades por una persona erudita de renombre fuera de la facultad regular. Las conferencias llevan el nombre del Dr. John E. y la Sra. Eliza Payton, padres de la fallecida Sra. Grace Fuller, esposa del fundador del seminario Charles E. Fuller. 풀러신학대학원은 1948년 페이튼 강좌를 개설하여 정규 교수진 외에 저명한 학자의 신학 강연을 제공해왔습니다. 강좌의 명칭은 학교 설립자 찰스 풀러 (Charles E. Fuller)의 아내인 그레이스 풀러 (Grace Fuller) 부인의 양친 존 페이튼 (John E. Payton) 박사와 엘리자 페이튼 (Eliza Payton) 부인의 이름을 따라 붙여졌습니다

Modeling the partially coherent behavior of few-mode far-infrared grating spectrometers

Modelling ultra-low-noise far-infrared grating spectrometers has become crucial for the next generation of far-infrared space observatories. Conventional techniques are awkward to apply because of the partially coherent form of the incident spectral field, and the few-mode response of the optics and detectors. We present a modal technique for modelling the behaviour of spectrometers, which allows for the propagation and detection of partially coherent fields, and the inclusion of straylight radiated by warm internal surfaces. We illustrate the technique by modelling the behaviour of the Long Wavelength Band of the proposed SAFARI instrument on the well-studied SPICA mission.Comment: This paper is submitted to Journal Optical Society of America A. When accepted, the paper can be found here: https://opg.optica.org/josaa/home.cf

Safari:Instrument design of the far-infrared imaging spectrometer for spica

The next great leap forward in space-based far-infrared astronomy will be made by the Japanese-led SPICA mission, which is anticipated to be launched late 2020's as the next large astrophysics mission of JAXA, in partnership with ESA and with key European contributions. Filling in the gap between JWST and ALMA, the SPICA mission will study the evolution of galaxies, stars and planetary systems. SPICA will utilize a deeply cooled 3m-class telescope, provided by European industry, to realize zodiacal background limited performance, high spatial resolution and large collecting area. Making full advantage of the deeply cooled telescope (&lt;6K), the SAFARI instrument on SPICA is a highly sensitive wide-field imaging photometer and spectrometer operating in the 34-210 μm wavelength range. Utilizing Nyquist-sampled focal-plane arrays of very sensitive Transition Edge Sensors (TES), SAFARI will offer a photometric imaging (R ≈ 2), and a low (R = 100) and medium resolution (R = 2000 at 100 μm) imaging spectroscopy mode in three photometric bands within a 2'x2' instantaneous FoV by means of a cryogenic Mach-Zehnder Fourier Transform Spectrometer. In this paper we will provide an overview of the SAFARI instrument design and system architecture. We will describe the reference design of the SAFARI focal- plane unit, the implementation of the various optical instrument functions designed around the central large-stroke FTS system, the photometric band definition and out-of-band filtering by quasioptical elements, the control of straylight, diffraction and thermal emission in the long-wavelength limit, and how we interface to the large-format FPA arrays at one end and the SPICA telescope assembly at the other end. We will briefly discuss the key performance drivers with special emphasis on the optical techniques adopted to overcome issues related to very low background operation of SAFARI. A summary and discussion of the expected instrument performance and an overview of the astronomical capabilities finally conclude the paper.</p

A Fourier optics approach to evaluate the astrometric performance of MICADO

We present our investigation into the impact of wavefront errors on high accuracy astrometry using Fourier Optics. MICADO, the upcoming near-IR imaging instrument for the Extremely Large Telescope, will offer capabilities for relative astrometry with an accuracy of 50 micro arcseconds ({\mu}as). Due to the large size of the point spread function (PSF) compared to the astrometric requirement, the detailed shape and position of the PSF on the detector must be well understood. Furthermore, because the atmospheric dispersion corrector of MICADO is a moving component within an otherwise mostly static instrument, it might not be sufficient to perform a simple pre-observation calibration. Therefore, we have built a Fourier Optics framework, allowing us to evaluate the small changes in the centroid position of the PSF as a function of wavefront error. For a complete evaluation, we model both the low order surface form errors, using Zernike polynomials, and the mid- and high-spatial frequencies, using Power Spectral Density analysis. The described work will then make it possible, performing full diffractive beam propagation, to assess the expected astrometric performance of MICADO.Comment: 13 pages, 13 figures, to be submitted to the SPIE Astronomical Telescopes & Instrumentation 2020 conferenc

Full characterization and analysis of a terahertz heterodyne receiver based on a NbN hot electron bolometer

We present a complete experimental characterization of a quasioptical twin-slot antenna coupled small area (1.0×0.15 µm^2) NbN hot electron bolometer (HEB) mixer compatible with currently available solid state tunable local oscillator (LO) sources. The required LO power absorbed in the HEB is analyzed in detail and equals only 25 nW. Due to the small HEB volume and wide antenna bandwidth, an unwanted direct detection effect is observed which decreases the apparent sensitivity. Correcting for this effect results in a receiver noise temperature of 700 K at 1.46 THz. The intermediate frequency (IF) gain bandwidth is 2.3 GHz and the IF noise bandwidth is 4 GHz. The single channel receiver stability is limited to 0.2–0.3 s in a 50 MHz bandwidth

Complex Beam Mapping and Fourier Optics Analysis of a Wide-Field Microwave Kinetic Inductance Detector Camera

For astronomical instruments, accurate knowledge of the optical pointing and coupling are essential to characterize the alignment and performance of (sub-)systems prior to integration and deployment. Ideally, this requires the phase response of the optical system, which for direct (phase insensitive) detectors was not previously accessible. Here we show development of the phase sensitive complex beam pattern technique using a dual optical source heterodyne technique for a large field of view Microwave Kinetic Inductance Detector camera at 350 GHz. We show here how you can analyze the measured data with Fourier optics, which allows integration into a telescope model to calculate the on sky beam pattern and telescope aperture efficiency prior to deployment at a telescope.Comment: This is a post-peer-review, pre-copy edit version of an article published in Journal of Low Temperature Physics. The final authenticated version is available onlin

Value of symptoms and additional diagnostic tests for colorectal cancer in primary care: systematic review and meta-analysis

Objective To summarise available evidence on diagnostic tests that might help primary care physicians to identify patients with an increased risk for colorectal cancer among those consulting for non-acute lower abdominal symptoms