Context.
The Atacama Large Millimeter/submillimeter Array (ALMA) has been in operation since 2011, but it has not yet been populated with the full suite of its planned frequency bands. In particular, ...ALMA Band 2 (67−90 GHz) is the final band in the original ALMA band definition to be approved for production.
Aims.
We aim to produce a wideband, tuneable, sideband-separating receiver with 28 GHz of instantaneous bandwidth per polarisation operating in the sky frequency range of 67−116 GHz. Our design anticipates new ALMA requirements following the recommendations of the 2030 ALMA Development Roadmap.
Methods.
The cryogenic cartridge is designed to be compatible with the ALMA Band 2 cartridge slot, where the coldest components – the feedhorns, orthomode transducers, and cryogenic low noise amplifiers – operate at a temperature of 15 K. We use multiple simulation methods and tools to optimise our designs for both the passive optics and the active components. The cryogenic cartridge is interfaced with a room-temperature (warm) cartridge hosting the local oscillator and the downconverter module. This warm cartridge is largely based on GaAs semiconductor technology and is optimised to match the cryogenic receiver bandwidth with the required instantaneous local oscillator frequency tuning range.
Results.
Our collaboration has resulted in the design, fabrication, and testing of multiple technical solutions for each of the receiver components, producing a state-of-the-art receiver covering the full ALMA Band 2 and 3 atmospheric window. The receiver is suitable for deployment on ALMA in the coming years and it is capable of dual-polarisation, sideband-separating observations in intermediate frequency bands spanning 4−18 GHz for a total of 28 GHz on-sky bandwidth per polarisation channel.
Conclusions.
We conclude that the 67−116 GHz wideband implementation for ALMA Band 2 is now feasible and that this receiver provides a compelling instrumental upgrade for ALMA that will enhance observational capabilities and scientific reach.
The European Space Agency’s Planck satellite was launched on 14 May 2009, and surveyed the sky stably and continuously between August 2009 and October 2013. The scientific analysis of the Planck data ...requires understanding the optical response of its detectors, which originates partly from a physical model of the optical system. In this paper, we use in-flight measurements of planets within ∼1° of boresight to estimate the geometrical properties of the telescope and focal plane. First, we use observed grating lobes to measure the amplitude of mechanical dimpling of the reflectors, which is caused by the hexagonal honeycomb structure of the carbon fibre reflectors. We find that the dimpling amplitude on the two reflectors is larger than expected from the ground, by 20% on the secondary and at least a factor of 2 on the primary. Second, we use the main beam shapes of 26 detectors to investigate the alignment of the various elements of the optical system, as well as the large-scale deformations of the reflectors. We develop a metric to guide an iterative fitting scheme, and are able to determine a new geometric model that fits the in-flight measurements better than the pre-flight prediction according to this metric. The new alignment model is within the mechanical tolerances expected from the ground, with some specific but minor exceptions. We find that the reflectors contain large-scale sinusoidal deformations most probably related to the mechanical supports. In spite of the better overall fit, the new model still does not fit the beam measurements at a level compatible with the needs of cosmological analysis. Nonetheless, future analysis of the Planck data would benefit from taking into account some of the features of the new model. The analysis described here exemplifies some of the limitations of in-flight retrieval of the geometry of an optical system similar to that of Planck, and provides useful information for similar efforts in future experiments.
The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL) is the fourth medium (M4) mission selected in the context of the ESA Cosmic Vision 2015–2025 programme, with a launch planned ...in 2028. During 4 years of flight operations, ARIEL will probe the chemical and physical properties of approximately 1000 known exoplanets by observing their atmosphere, to study how planetary systems form and evolve
1
,
2
. The mission is designed as a transit and eclipse spectroscopy survey, operated by a 1-m class telescope feeding two instruments, the Fine Guidance system (FGS) and the ARIEL InfraRed Spectrometer (AIRS), that accommodate photometric and spectroscopic channels covering the band from 0.5 to 7.8 μm in the visible to near-IR range
3
,
4
. The mission high sensitivity requirements ask for an extremely stable thermo-mechanical platform. The payload thermal control is based on a passive and active cooling approach. Passive cooling is achieved by a V-Groove shields system that exploits the L2 orbit favourable thermal conditions to cool the telescope and the optical bench to stable temperatures <60 K. The FGS focal planes operate at the optical bench temperature while the AIRS channel detectors require a colder reference, lower than 42 K. This is provided by an active cooling system based on a Neon Joule-Thomson cold end, fed by a mechanical compressor. In this paper we report the thermal architecture of the payload at the end of Phase B1 and present the requirements that drive the design together with the analyses results and the expected performances.
The Simultaneous Medicina-Planck Experiment (SiMPlE) is aimed at observing a selected sample of 263 extragalactic and Galactic sources with the Medicina 32-m single-dish radio telescope in the same ...epoch as the Planck satellite observations.
The data, acquired with a frequency coverage down to 5 GHz and combined with Planck at frequencies above 30 GHz, will constitute a useful reference catalogue of bright sources over the whole Northern hemisphere. Furthermore, source observations performed in different epochs and comparisons with other catalogues will allow the investigation of source variabilities on different time-scales.
In this work, we describe the sample selection, the ongoing data acquisition campaign, the data reduction procedures, the developed tools and the comparison with other data sets.
We present 5 and 8.3 GHz data for the SiMPlE Northern sample, consisting of 79 sources with δ≥ 45° selected from our catalogue and observed during the first 6 months of the project. A first analysis of their spectral behaviour and long-term variability is also presented.
The Planck satellite in orbit mission ended in October 2013. Between the end of Low Frequency Instrument (LFI) routine mission operations and the satellite decommissioning, a dedicated test was also ...performed to measure the Planck telescope emissivity. The scope of the test was twofold: i) to provide, for the first time in flight, a direct measure of the telescope emissivity; and ii) to evaluate the possible degradation of the emissivity by comparing data taken in flight at the end of mission with those taken during the ground telescope characterization. The emissivity was determined by heating the Planck telescope and disentangling the system temperature excess measured by the LFI radiometers. Results show End of Life (EOL) performance in good agreement with the results from the ground optical tests and from
in-flight
indirect estimations measured during the Commissioning and Performance Verification (CPV) phase. Methods and results are presented and discussed.
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