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Aims. This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods. The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480−1250 GHz with SIS mixers and the 1410−1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s −1 . Results. After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations.

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We report on the design and performance of a 2 3 3 frequency multiplier chain to the 1.7-1.9 THz band. GaAsbased planar Schottky diodes are utilized in each stage. A W-band power amplifier, driven by a commercially available synthesizer, was used to pump the chain with 100 mW of input power. The peak measured output power at room temperature is 3 W at 1740 GHz. When cooled to 120 K, the chain provides more than 1.5 W from 1730 to 1875 GHz and produced a peak of 15 W at 1746 GHz.

We consider the problem of variable selection in high-dimensional statistical models where the goal is to report a set of variables, out of many predictors X 1 , . . . , Xp, that are relevant to a response of interest. For linear high-dimensional model, where the number of parameters exceeds the number of samples (p > n), we propose a procedure for variables selection and prove that it controls the directional false discovery rate (FDR) below a pre-assigned significance level q ∈ [0, 1]. We further analyze the statistical power of our framework and show that for designs with subgaussian rows and a common precision matrix Ω ∈ R p×p , if the minimum nonzero parameter θ min satisfiesthen this procedure achieves asymptotic power one. Our framework is built upon the debiasing approach and assumes the standard condition s 0 = o( √ n/(log p) 2 ), where s 0 indicates the number of true positives among the p features. Notably, this framework achieves exact directional FDR control without any assumption on the amplitude of unknown regression parameters, and does not require any knowledge of the distribution of covariates or the noise level. We test our method in synthetic and real data experiments to assess its performance and to corroborate our theoretical results.MSC 2010 subject classifications: Primary 62F03, 62J05, 62J07; secondary 62F12.

International audienceWe report on the design, fabrication and characterization of a 300 GHz Schottky-diode frequency tripler made of two mirror-image integrated circuits that are power-combined in-phase in a single waveguide block using compact Y-junctions at the input and output waveguides. Each chip features six anodes on a 5 μm thick GaAs membrane. The tripler has 5-15% conversion efficiency measured across the 265-330 GHz band when driven with 50-250 mW of input power at room temperature. At 318 GHz it delivers a peak power of 26 mW with 11% conversion efficiency. The power-combined frequency multiplier is compared with a single-chip tripler designed for the same band using the same integrated circuit