We demonstrate a compact and inexpensive microcontroller based YDFA control system built around a PyBoard V1.1 and programmed in MicroPython. We demonstrate power ramping, housekeeping and shutdown in case of SBS induced back-reflections.

We demonstrate a Yb-doped fiber amplifier (YDFA) designed for large aperture bidirectional laser phased arrays locked to a remote coherent Beacon. The amplifier is CW, single-mode (λ = 1064 nm), gain of 30 dB, high slope efficiency of 86 ± 2.2% extremely large dynamic range > 100 dB and broad temperature range with low residual phase noise of ≤ 30 mrad when the array is phase locked to the Beacon.

We demonstrate a sparse 3-channel Laser Phased Array (40 dBm/ch) locked to an ultra low-power (-55 dBm/ch) remote Beacon. We measured a combination efficiency ≥ 17% and 12 µs to peak power. In a nominal closed packed array the combining efficiency is about 62%. This demonstration is a key step in realizing directed energy for space applications.

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.

Effective transfer of beamed optical energy to a spacecraft requires that the source have a sufficiently small angular divergence to contain the beam within the area of the spacecraft collector. Such a directed energy system could be achieved by coherently combining many small optical sources distributed throughout a large-scale array. The fundamental unit of such a system is a master oscillator power amplifier (MOPA) which consists of a frequency stabilized laser source distributed to amplifier trees in the array. A fundamental challenge in long baseline coherent beam combination is that each source be combined with sub-wavelength accuracy over the entire array. In addition to perturbations due to mechanical and atmospheric disturbances, phase noise introduced by the amplifiers and the seed distribution network must also be accounted for in order to achieve the necessary accuracy. This work investigates the excess phase noise introduced by the amplifier stages and fiber optic links. Locking schemes that could be used to synchronize such an array are presented. The test bed used to interrogate phase noise is based on an all polarization maintaining fiber Mach-Zehnder interferometer (MZI), controlled by an FPGA based digital quadrature detection at a sampling rate of 1 MS/s yielding direct measurement of amplitude and phase with servo control for phase locking. Results for various MOPA and fiber link configurations based on Yb-doped fiber amplifiers operating at 1064 nm and kilometer scale link lengths are presented.

Parity violating extensions of the standard electromagnetic theory cause in vacuo rotation of the plane of polarization of propagating photons. This effect, also known as cosmic birefringence, impacts the cosmic microwave background (CMB) anisotropy angular power spectra, producing non-vanishing T–B and E–B correlations that are otherwise null when parity is a symmetry. Here we present new constraints on an isotropic rotation, parametrized by the angle α, derived from Planck 2015 CMB polarization data. To increase the robustness of our analyses, we employ two complementary approaches, in harmonic space and in map space, the latter based on a peak stacking technique. The two approaches provide estimates for α that are in agreement within statistical uncertainties and very stable against several consistency tests. Considering the T–B and E–B information jointly, we find α = 0. ◦31 ± 0. ◦05 (stat.) ± 0. ◦28 (syst.) from the harmonic analysis and α = 0. ◦35 ± 0. ◦05 (stat.) ± 0. ◦28 (syst.) from the stacking approach. These constraints are compatible with no parity violation and are dominated by the systematic uncertainty in the orientation of Planck’s polarization-sensitive bolometers.

We present an updated description of the Planck Low Frequency Instrument (LFI) data processing pipeline, associated with the 2015 data release. We point out the places where our results and methods have remained unchanged since the 2013 paper and we highlight the changes made for the 2015 release, describing the products (especially timelines) and the ways in which they were obtained. We demonstrate that the pipeline is self-consistent (principally based on simulations) and report all null tests. For the first time, we present LFI maps in Stokes Q and U polarization. We refer to other related papers where more detailed descriptions of the LFI data processing pipeline may be found if needed.

This paper presents the characterization of the in-flight beams, the beam window functions, and the associated uncertainties for the Planck Low Frequency Instrument (LFI). The structure of the paper is similar to that presented in the 2013 Planck release; the main differences concern the beam normalization and the delivery of the window functions to be used for polarization analysis. The in-flight assessment of the LFI main beams relies on measurements performed during observations of Jupiter. By stacking data from seven Jupiter transits, the main beam profiles are measured down to –25 dB at 30 and 44 GHz, and down to –30 dB at 70 GHz. It has been confirmed that the agreement between the simulated beams and the measured beams is better than 1% at each LFI frequency band (within the 20 dB contour from the peak, the rms values are 0.1% at 30 and 70 GHz; 0.2% at 44 GHz). Simulated polarized beams are used for the computation of the effective beam window functions. The error budget for the window functions is estimated from both main beam and sidelobe contributions, and accounts for the radiometer band shapes. The total uncertainties in the effective beam window functions are 0.7% and 1% at 30 and 44 GHz, respectively (at ` ≈ 600); and 0.5 % at 70 GHz (at ` ≈ 1000).

We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400 deg$^2$ patch of sky centered on RA 0h, Dec. $-57.5\deg$. The combined maps reach a depth of 57 nK deg in Stokes $Q$ and $U$ in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2 $\mu$K deg in $Q$ and $U$ at 143 GHz). We detect 150$\times$353 cross-correlation in $B$-modes at high significance. We fit the single- and cross-frequency power spectra at frequencies $\geq 150$ GHz to a lensed-$\Lambda$CDM model that includes dust and a possible contribution from inflationary gravitational waves (as parameterized by the tensor-to-scalar ratio $r$), using a prior on the frequency spectral behavior of polarized dust emission from previous \planck\ analysis of other regions of the sky. We find strong evidence for dust and no statistically significant evidence for tensor modes. We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the $r$ constraint. Finally we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for $r$, and yields an upper limit $r_{0.05}<0.12$ at 95% confidence. Marginalizing over dust and $r$, lensing $B$-modes are detected at $7.0\,\sigma$ significance.

The Second Planck Catalogue of Compact Sources is a catalogue of sources detected in single-frequency maps from the full duration of the Planck mission and supersedes previous versions of the Planck compact source catalogues. It consists of compact sources, both Galactic and extragalactic, detected over the entire sky. Compact sources detected in the lower frequency channels are assigned to the PCCS2, while at higher frequencies they are assigned to one of two sub-catalogues, the PCCS2 or PCCS2E, depending on their location on the sky. The first of these catalogues covers most of the sky and allows the user to produce subsamples at higher reliabilities than the target 80% integral reliability of the catalogue. The PCCS2E contains sources detected in sky regions where the diffuse emission makes it difficult to quantify the reliability of the detections. Both the PCCS2 and PCCS2E include polarization measurements, in the form of polarized flux densities, or upper limits, and orientation angles for all seven polarization-sensitive Planck channels. The improved data-processing of the full-mission maps and their reduced noise levels allow us to increase the number of objects in the catalogue, improving its completeness for the target 80 % reliability as compared with the previous versions, the PCCS and ERCSC catalogues.

Based on cosmic microwave background (CMB) maps from the 2013 Planck Mission data release, this paper presents the detection of the integrated Sachs-Wolfe (ISW) effect, that is, the correlation between the CMB and large-scale evolving gravitational potentials. The significance of detection ranges from 2 to 4σ, depending on which method is used. We investigated three separate approaches, which essentially cover all previous studies, and also break new ground. (i) We correlated the CMB with the Planck reconstructed gravitational lensing potential (for the first time). This detection was made using the lensing-induced bispectrum between the low-` and high-` temperature anisotropies; the correlation between lensing and the ISW effect has a significance close to 2.5σ. (ii) We cross-correlated with tracers of large-scale structure, which yielded a significance of about 3σ, based on a combination of radio (NVSS) and optical (SDSS) data. (iii) We used aperture photometry on stacked CMB fields at the locations of known large-scale structures, which yielded and confirms a 4σ signal, over a broader spectral range, when using a previously explored catalogue, but shows strong discrepancies in amplitude and scale when compared with expectations. More recent catalogues give more moderate results that range from negligible to 2.5σ at most, but have a more consistent scale and amplitude, the latter being still slightly higher than what is expected from numerical simulations within ΛCMD. Where they can be compared, these measurements are compatible with previous work using data from WMAP, where these scales have been mapped to the limits of cosmic variance. Planck’s broader frequency coverage allows for better foreground cleaning and confirms that the signal is achromatic, which makes it preferable for ISW detection. As a final step we used tracers of large-scale structure to filter the CMB data, from which we present maps of the ISW temperature perturbation. These results provide complementary and independent evidence for the existence of a dark energy component that governs the currently accelerated expansion of the Universe.

The Planck nominal mission cosmic microwave background (CMB) maps yield unprecedented constraints on primordial non-Gaussianity (NG). Using three optimal bispectrum estimators, separable template-fitting (KSW), binned, and modal, we obtain consistent values for the primordial local, equilateral, and orthogonal bispectrum amplitudes, quoting as our final result f(NL)(local) = 2.7 +/- 5.8, f(NL)(equil) = -42 +/- 75, and f(NL)(ortho) = 25 +/- 39 (68% CL statistical). Non-Gaussianity is detected in the data; using skew-C 'statistics we find a nonzero bispectrum from residual point sources, and the integrated-Sachs-Wolfe-lensing bispectrum at a level expected in the CDM scenario. The results are based on comprehensive crossvalidation of these estimators on Gaussian and non-Gaussian simulations, are stable across component separation techniques, pass an extensive suite of tests, and are confirmed by skew-C `, wavelet bispectrum and Minkowski functional estimators. Beyond estimates of individual shape amplitudes, we present model-independent, three-dimensional reconstructions of the Planck CMB bispectrum and thus derive constraints on early-Universe scenarios that generate primordial NG, including general single-field models of inflation, excited initial states (non-Bunch-Davies vacua), and directionally-dependent vector models. We provide an initial survey of scale-dependent feature and resonance models. These results bound both general single-field and multi-field model parameter ranges, such as the speed of sound, cs 0 : 02 (95% CL), in an e ff ective field theory parametrization, and the curvaton decay fraction rD 0 : 15 (95% CL). The Planck data significantly limit the viable parameter space of the ekpyrotic / cyclic scenarios. The amplitude of the four-point function in the local model NL < 2800 (95% CL). Taken together, these constraints represent the highest precision tests to date of physical mechanisms for the origin of cosmic structure.

In this paper we discuss the Planck-LFI in-flight calibration campaign. After a brief overview of the ground test campaigns, we describe in detail the calibration and performance verification (CPV) phase, carried out in space during and just after the cool-down of LFI. We discuss in detail the functionality verification, the tuning of the front-end and warm electronics, the preliminary performance assessment and the thermal susceptibility tests. The logic, sequence, goals and results of the in-flight tests are discussed. All the calibration activities were successfully carried out and the instrument response was comparable to the one observed on ground. For some channels the in-flight tuning activity allowed us to improve significantly the noise performance.

Destriping is a well-established technique for removing low-frequency correlated noise from Cosmic Microwave Background (CMB) survey data. In this paper we present a destriping algorithm tailored to data from a polarimeter, i.e. an instrument where each channel independently measures the polarization of the input signal. We also describe a fully parallel implementation in Python released as Free Software and analyze its results and performance on simulated datasets, both the design case of signal and correlated noise, and with additional systematic effects. Finally we apply the algorithm to 30 days of 37.5 GHz polarized microwave data gathered from the B-Machine experiment, developed at UCSB. The B-Machine data and destriped maps are made publicly available. The purpose is the development of a scalable software tool to be applied to the upcoming 12 months of temperature and polarization data from LATTE (Low frequency All sky TemperaTure Experiment) at 8 GHz and to even larger datasets.

We present the calibration and scientific performance parameters of the Planck Low Frequency Instrument (LFI) measured during the ground cryogenic test campaign. These parameters characterise the instrument response and constitute our optimal pre-launch knowledge of the LFI scientific performance. The LFI shows excellent 1/f stability and rejection of instrumental systematic effects; its measured noise performance shows that LFI is the most sensitive instrument of its kind. The calibration parameters will be updated during flight operations until the end of the mission.

Characterization of the frequency response of coherent radiometric receivers is a key element in estimating the flux of astrophysical emissions, since the measured signal depends on the convolution of the source spectral emission with the instrument band shape.Laboratory Radio Frequency (RF) measurements of the instrument bandpass often require complex test setups and are subject to a number of systematic effects driven by thermal issues and impedance matching, particularly if cryogenic operation is involved.In this paper we present an approach to modeling radiometers bandpasses by integrating simulations and RF measurements of individual components. This method is based on QUCS (Quasi Universal Circuit Simulator), an open-source circuit simulator, which gives the flexibility of choosing among the available devices, implementing new analytical software models or using measured S-parameters. Therefore an independent estimate of the instrument bandpass is achieved using standard individual component measurements and validated analytical simulations.In order to automate the process of preparing input data, running simulations and exporting results we developed the Python package python-qucs and released it under GNU Public License.We discuss, as working cases, bandpass response modeling of the COFE and PLANCK Low Frequency Instrument (LFI) radiometers and compare results obtained with QUCS and with a commercial circuit simulator software. The main purpose of bandpass modeling in COFE is to optimize component matching, while in LFI they represent the best estimation of frequency response, since end-to-end measurements were strongly affected by systematic effects.

We present a system-level description of the Low Frequency Instrument (LFI) considered as a differencing polarimeter, and evaluate its expected performance. The LFI is one of the two instruments on board the ESA Planck mission to study the cosmic microwave background. It consists of a set of 22 radiometers sensitive to linear polarisation, arranged in orthogonally-oriented pairs connected to 11 feed horns operating at 30, 44 and 70 GHz. In our analysis, the generic Jones and Mueller-matrix formulations for polarimetry are adapted to the special case of the LFI. Laboratory measurements of flight components are combined with optical simulations of the telescope to investigate the values and uncertainties in the system parameters affecting polarisation response. Methods of correcting residual systematic errors are also briefly discussed. The LFI has beam-integrated polarisation efficiency >99% for all detectors, with uncertainties below 0.1%. Indirect assessment of polarisation position angles suggests that uncertainties are generally less than 0 degrees.5, and this will be checked in flight using observations of the Crab nebula. Leakage of total intensity into the polarisation signal is generally well below the thermal noise level except for bright Galactic emission, where the dominant effect is likely to be spectral-dependent terms due to bandpass mismatch between the two detectors behind each feed, contributing typically 1-3% leakage of foreground total intensity. Comparable leakage from compact features occurs due to beam mismatch, but this averages to < 5 x 10(-4) for large-scale emission. An inevitable feature of the LFI design is that the two components of the linear polarisation are recovered from elliptical beams which differ substantially in orientation. This distorts the recovered polarisation and its angular power spectrum, and several methods are being developed to correct the effect, both in the power spectrum and in the sky maps. The LFI will return a high-quality measurement of the CMB polarisation, limited mainly by thermal noise. To meet our aspiration of measuring polarisation at the 1% level, further analysis of flight and ground data is required. We are still researching the most effective techniques for correcting subtle artefacts in polarisation; in particular the correction of bandpass mismatch effects is a formidable challenge, as it requires multi-band analysis to estimate the spectral indices that control the leakage.

The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries eleven radiometer subsystems, called radiometer chain assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20 K and the back-end at 300 K, and with an external input load cooled to 4 K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e. g. 1/f noise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential inputs to the Planck-LFI data analysis.

In this paper we present the Low Frequency Instrument (LFI), designed and developed as part of the Planck space mission, the ESA program dedicated to precision imaging of the cosmic microwave background (CMB). Planck-LFI will observe the full sky in intensity and polarisation in three frequency bands centred at 30, 44 and 70 GHz, while higher frequencies (100-850 GHz) will be covered by the HFI instrument. The LFI is an array of microwave radiometers based on state-of-the-art Indium Phosphide cryogenic HEMT amplifiers implemented in a differential system using blackbody loads as reference signals. The front-end is cooled to 20K for optimal sensitivity and the reference loads are cooled to 4K to minimise low frequency noise. We provide an overview of the LFI, discuss the leading scientific requirements and describe the design solutions adopted for the various hardware subsystems. The main drivers of the radiometric, optical and thermal design are discussed, including the stringent requirements on sensitivity, stability, and rejection of systematic effects. Further details on the key instrument units and the results of ground calibration are provided in a set of companion papers.

Planck's Low Frequency Instrument is an array of 22 pseudo-correlation radiometers at 30, 44, and 70 GHz. Before integrating the overall array assembly, a first set of tests has been performed for each radiometer chain assembly (RCA), consisting of two radiometers. In this paper, we describe Rachel, a software application which has been purposely developed and used during the RCA test campaign to carry out both near-realtime on-line data analysis and data storage (in FITS format) of the raw output from the radiometric chains.