We present a parametric component separation forecast for the QUIJOTE–MFI2 instrument (10–20 GHz) that assesses its impact on constraining polarised synchrotron emission at 1° full width at half maximum and Nside = 64. Using simulated sky maps based on power-law and curved synchrotron spectra, we show that adding QUIJOTE-MFI2 to existing WMAP+Planck+MFI data yields statistically unbiased parameter estimates with substantial uncertainty reductions. The improvement factors reach ∼10 for the synchrotron spectral index (βs), ∼5 for the curvature parameter (Cs), and ∼43 for polarisation amplitudes in bright regions. Deep QUIJOTE cosmological fields enable βs constraints even in intrinsically low S/N regions, where WMAP+Planck alone remain prior-dominated. Current combined sensitivities are insufficient to detect a synchrotron curvature of Cs = −0.052 on a pixel-by-pixel basis, but a 2σ detection is achievable for |Cs|≳0.14 in the brightest regions of the Galactic plane. In those deep cosmological fields, combining QUIJOTE-MFI2 with WMAP and Planck reduces the median synchrotron residual at 100 GHz by a factor of six to 0.033 μ KCMB. These results demonstrate that QUIJOTE-MFI2 will provide critical low-frequency information for modelling Galactic synchrotron emission, therefore offering valuable complementary constraints for future cosmic microwave background surveys such as LiteBIRD and the Simons Observatory.

We present the commissioning and first results of the Thirty and Forty Gigahertz Instrument (TFGI), which observes the sky at 31 and 41 GHz with angular resolutions of 21' and 18' from the second QUIJOTE telescope at the Teide Observatory. Its primary goal is to conduct a deep cosmological survey in selected regions of the Northern sky with high-sensitivity polarization measurements. The commissioning phase covered Nov2021-Oct2022, during which the instrument operated with a configuration of 7 receivers, 4 at 31 GHz and 3 at 41 GHz. Over this period, approximately 1200 h of data were acquired. Of these, 380 h were dedicated to calibration sources, used to characterize the instrumental properties of TFGI, including the pointing model, beam response, gain stability, polarimetric performance, and instantaneous sensitivity. We provide a detailed characterization of these properties and describe how they are being improved for future observing runs. We use 230 h of observations from bright Galactic regions (Cygnus, W43, W44, and W47) to further validate the instrument performance. As an illustrative example, we present the intensity and polarization spectral energy distributions of W44, finding good agreement with existing measurements. From the noise map of these observations, we measure a polarization sensitivity of 8.3 μK deg^-1 after an effective observing depth of 0.57 h deg^-2. This performance, achieved considering only 2 detectors at 31 GHz, is already comparable to that achieved by WMAP (with almost 3 times the integration time per unit area, 1.61 h deg^-2). Extrapolating these results to the full TFGI array, with up to 29 detectors, we show that the instrument is expected to reach the target sensitivity of 1 μK deg^-1 at both 31 and 41 GHz over three cosmological fields covering a total area of 3600 deg^2 after an effective integration time of 5.7 years.

We present an analytical instrument model of the TMS radiometer, a pseudo-correlation system designed for absolute sky-temperature measurements through a continuous comparison between sky and reference-load signals. The goal of this work is to quantify and understand the impact of instrumental non-idealities that are intrinsic to absolute radiometric measurements. We used a combination of the Jones-matrix formalism, to describe non-ideal signal mixing effects in the different instrument components, and the Friis formalism, to account for noise-temperature contributions which introduce specific offset terms. The model includes all components from the cryostat entrance window onwards and allows us to propagate realistic losses, return losses, and noise figures through the system. We find that non-ideal mixing effects, such as intensity-to-polarization and sky-to-load leakage, are expected to appear at the percent level, but they could be in principle calibrated out. The total TMS intensity response exhibits a frequency-dependent offset with a band-averaged level of 6.9 K, dominated by the cryostat window, and with smaller contributions from the infrared filter and orthomode transducers. Under the required TMS thermal stability of 1 mK over one hour, the resulting variation in the output signal can reach up to 91.3 mK, which sets the fundamental limit on the absolute sky-temperature accuracy. In contrast, relative spectral measurements across the 10-20 GHz band are stable at the few-microkelvin level, consistent with the instrument target sensitivity of 10 Jy/sr. This work provides a detailed and quantitative assessment of the systematic effects affecting absolute radiometric measurements and establishes a robust framework for the calibration and performance optimization of the TMS instrument.

Various so-called anomalies have been found in both the WMAP and Planck cosmic microwave background (CMB) temperature data that exert a mild tension against the highly successful best-fit 6 parameter cosmological model, potentially providing hints of new physics to be explored. That these are real features on the sky is uncontested. However, given their modest significance, whether they are indicative of true departures from the standard cosmology or simply statistical excursions, due to a mildly unusual configuration of temperature anisotropies on the sky which we refer to as the "fluke hypothesis", cannot be addressed further without new information. No theoretical model of primordial perturbations has to date been constructed that can explain all of the temperature anomalies. Therefore, we focus in this paper on testing the fluke hypothesis, based on the partial correlation between the temperature and E-mode CMB polarisation signal. In particular, we compare the properties of specific statistics in polarisation, built from unconstrained realisations of the ΛCDM cosmological model as might be observed by the LiteBIRD satellite, with those determined from constrained simulations, where the part of the E-mode anisotropy correlated with temperature is constrained by observations of the latter. Specifically, we use inpainted Planck 2018 SMICA temperature data to constrain the E-mode realisations. Subsequent analysis makes use of masks defined to minimise the impact of the inpainting procedure on the E-mode map statistics. We find that statistical assessments of the E-mode data alone do not provide any evidence for or against the fluke hypothesis. However, tests based on cross-statistical measures determined from temperature and E modes can allow this hypothesis to be rejected with a moderate level of probability.

Anomalous Microwave Emission (AME) is a diffuse microwave component thought to arise from spinning dust grains, though it remains poorly understood. We analyzed AME in 144 Galactic clouds by combining low-frequency maps from S-PASS (2.3 GHz), C-BASS (4.76 GHz), and QUIJOTE (10-20 GHz) with 21 ancillary maps. Using aperture photometry and parametric spectral energy distribution (SED) fitting via Markov chain Monte Carlo methods without informative priors, we measured AME emissivity, peak frequency, and spectral width. We achieved peak frequency constraints nearly three times tighter than previous work and identify 83 new AME sources. The AME spectra are generally broader than predicted by spinning dust models for a single phase of the interstellar medium, suggesting either multiple spinning dust components along the line of sight or incomplete representation of the grain size distribution in current models. However, the narrowest observed widths match theoretical predictions, supporting the spinning dust hypothesis. The AME amplitude correlates most strongly with the thermal dust peak flux and radiance, showing similar to 30% scatter and sublinear scaling, which suggests reduced AME efficiency in regions with brighter thermal dust emission. The AME peak frequency increases with thermal dust temperature in a trend current theoretical models do not reproduce, indicating that spinning dust models must incorporate dust evolution and radiative transfer in a self-consistent framework where environmental parameters and grain properties are interdependent. Polycyclic aromatic hydrocarbon tracers correlate with AME emissivity, supporting a physical link to small dust grains. Finally, a log-Gaussian function provides a good empirical description of the AME spectrum across the sample, given current data quality and frequency coverage.

Upcoming cosmic microwave background (CMB) experiments aim to detect primordial gravitational waves with unprecedented sensitivity. Effective foreground removal is essential to avoid biases in the measurement of the tensor-to-scalar ratio (r) in this high-precision regime. Recent analyses highlight the unexpected complexity of synchrotron emission at low frequencies, underscoring the need for more sensitive low-frequency data. To address this challenge, the European Low-Frequency Survey (ELFS) initiative and the Simons Array collaboration propose installing two European low-frequency receivers on one of the Simons Array telescopes. These receivers will enable measurements in the Southern Hemisphere between 6 and 20,GHz, complementary to those of current and proposed experiments targeting the measurement of cosmological gravitational waves. In this work, we study the benefits of combining these low-frequency observations with a representative future CMB experiment operating from the Southern Hemisphere. We find that the extra information can improve the knowledge of the underlying synchrotron spectral energy distribution (SED), with positive impacts on the robustness of measurement of the tensor-to-scalar ratio, r, against the complexity of low-frequency foregrounds.

We introduce a novel approach to estimate the spectral index, beta(s), of polarised synchrotron emission, combining the moment expansion of Cosmic Microwave Background foregrounds and the constrained Internal Linear Combination method. We reconstructed the maps of the first two synchrotron moments, combining multi-frequency data, and applied the 'T-T plot' technique between two moment maps to estimate the synchrotron spectral index. This approach offers a new technique for mapping the foreground spectral parameters, complementing the model-based parametric component separation methods. Applying this technique, we derived a new constraint on the spectral index of polarised synchrotron emission using QUIJOTE MFI wide-survey 11 and 13 GHz data, Wilkinson Microwave Anisotropy Probe data at K and Ka bands, and Planck LFI 30 GHz data. In the Galactic plane and North Polar Spur regions, we obtained an inverse-variance-weighted mean synchrotron index of beta(s) = -3.11 with a standard deviation of 0.21 due to intrinsic scatter, consistent with previous results based on parametric methods using the same dataset. We find that the inverse-variance-weighted mean spectral index, including both statistical and systematic uncertainties, is beta(plane)(s) = -3.05 +/- 0.01 in the Galactic plane and beta(high-lat)(s) = -3.13 +/- 0.02 at high latitudes, indicating a moderate steepening of the spectral index from low to high Galactic latitudes. Our analysis indicates that, within the current upper limit on the Anomalous Microwave Emission polarisation fraction, our results are not subject to any appreciable bias. Furthermore, we infer the spectral index over the entire QUIJOTE survey region, partitioning the sky into 21 patches. This technique can be further extended to constrain the synchrotron spectral curvature by reconstructing higher-order moments when better-quality data become available.

LiteBIRD is a JAXA-led space mission designed to produce all-sky microwave polarization maps. Its primary science goal is to test representative inflationary models by measuring the cosmic microwave background B-mode polarization generated by primordial gravitational waves, while also providing new insights into cosmology, particle physics, and astrophysics. The mission concept has been updated following the reformation activities initiated after the Mission Definition Review in 2024. The current concept preserves the central scientific objectives, while simplifying the payload configuration: a single telescope covers 12 frequency bands with band centers spanning 40 to 402 GHz, corresponding to an optical coverage of 34–448 GHz. The telescope is a cross-Dragone reflector with a 500 mm aperture diameter, cooled to approximately 5 K and coupled to transition-edge-sensor bolometer arrays operated at 0.1 K. LiteBIRD will observe from a Lissajous orbit around the Sun–Earth L2 point during a nominal 3-year survey. More specifically, the primary scientific objective is to achieve total uncertainty in the tensor-to-scalar ratio of δr < 0.002 (68% C.L.), including contributions from foreground residuals, statistical uncertainties, instrumental systematics, and margin contingency. The corresponding map-noise requirements are specified separately for the low-, mid-, and high-frequency ranges over the reionization and recombination multipole ranges. This sensitivity makes LiteBIRD unique not only for inflationary science but also for a broad range of scientific investigations probing the history of both the early and late Universe, as well as for astrophysical processes, including Galactic science. This paper summarizes the scientific objectives, updated payload and instrument concepts, observation strategy, and ground segment plans.

Detection of primordial B-mode polarization in the cosmic microwave background (CMB) from tensor perturbations generated during inflation is a major scientific goal of future CMB missions. Its success will strongly depend on the characterization of polarized foregrounds, a challenge that the LiteBIRD satellite aims to tackle with its 15 frequency bands ranging from 40 to 402 GHz. In this work, we forecast the ability of LiteBIRD to characterize polarized dust and synchrotron emission in the diffuse interstellar medium (ISM), at the angular power spectrum level. From simulated LiteBIRD intensity and polarization maps with different foreground complexities, we compute cross-frequency angular power spectra and fit them to dust and synchrotron spectral energy distributions, which are modeled by a modified black body and a power law, respectively. We find that LiteBIRD will be able to measure the dust temperature, dust and synchrotron spectral indices and spatial correlation with dispersions as low as σ(T_ d)∼0.2 K, σ(β_ d)∼0.006, σ(β_ s)∼0.04 and σ(ρ)∼10^-2, as well as to detect and quantify deviations from the proposed parametric model due to variations of the emission properties in the three dimensions of our Galaxy. Additionally, LiteBIRD is likely to rule out the power-law model of polarized foreground angular power spectra suggested by Planck data. It will also be able to detect differences in the values of β_ d, T_ d, and β_ s between E modes, B modes, and intensity in the diffuse ISM for the first time, highlighting the joint variations of the physical conditions and the magnetic field structure across the Galaxy. We conclude that in addition to detailed studies of CMB polarization, LiteBIRD will open a new window onto the physical conditions governing the ISM of the Milky Way.

Anomalous microwave emission (AME) represents an excess of radiation in the 10-60 GHz range, distinct from synchrotron, free-free, or thermal dust emission. Although most commonly attributed to electric dipole radiation from rapidly rotating small dust grains (spinning dust), alternative mechanisms such as magnetic dipole emission (MDE) remain plausible. The detection of AME across diverse environments, from diffuse interstellar clouds to protoplanetary disks and external galaxies, suggests that multiple physical processes or carriers may contribute to its origin. Understanding AME is essential for both Galactic astrophysics and cosmology, as it constitutes a significant foreground for cosmic microwave background (CMB) studies, potentially biasing measurements. This chapter reviews current theoretical frameworks and observational evidence for AME, highlighting the key outstanding questions concerning its emission mechanisms, carriers, and polarization properties. We discuss how the Square Kilometre Array Observatory (SKAO), through its unprecedented sensitivity, angular resolution, and frequency coverage, will transform AME studies. SKA observations will enable detailed mapping of AME morphology, precise characterisation of its spectral energy distribution, and the identification of its carriers in Galactic and extragalactic environments. By combining SKA-mid data with higher-frequency observations from ALMA and other facilities such as SPHEREx, it will be possible to disentangle competing models and exploit AME as a diagnostic probe of interstellar grain physics and the small-scale structure of the interstellar medium.

We introduce a novel approach to estimate the spectral index, βs, of polarised synchrotron emission, combining the moment expansion of Cosmic Microwave Background foregrounds and the constrained Internal Linear Combination method. We reconstructed the maps of the first two synchrotron moments, combining multi-frequency data, and applied the ‘T-T plot’ technique between two moment maps to estimate the synchrotron spectral index. This approach offers a new technique for mapping the foreground spectral parameters, complementing the model-based parametric component separation methods. Applying this technique, we derived a new constraint on the spectral index of polarised synchrotron emission using QUIJOTE MFI wide-survey 11 and 13 GHz data, Wilkinson Microwave Anisotropy Probe data at K and Ka bands, and Planck LFI 30 GHz data. In the Galactic plane and North Polar Spur regions, we obtained an inverse-variance-weighted mean synchrotron index of βs = −3.11 with a standard deviation of 0.21 due to intrinsic scatter, consistent with previous results based on parametric methods using the same dataset. We find that the inverse-variance-weighted mean spectral index, including both statistical and systematic uncertainties, is βsplane = −3.05 ± 0.01 β s plane = − 3.05 ± 0.01 $ \beta_{s}^{\mathrm{plane}} = -3.05 \pm 0.01 $ in the Galactic plane and βshigh-lat = −3.13 ± 0.02 β s high - lat = − 3.13 ± 0.02 $ \beta_{s}^{\mathrm{high}\text{-}\mathrm{lat}} = -3.13 \pm 0.02 $ at high latitudes, indicating a moderate steepening of the spectral index from low to high Galactic latitudes. Our analysis indicates that, within the current upper limit on the Anomalous Microwave Emission polarisation fraction, our results are not subject to any appreciable bias. Furthermore, we infer the spectral index over the entire QUIJOTE survey region, partitioning the sky into 21 patches. This technique can be further extended to constrain the synchrotron spectral curvature by reconstructing higher-order moments when better-quality data become available.

Polarized synchrotron emission from ultra-relativistic electrons spiraling the Galactic magnetic field has recently become one of the most relevant emissions in the interstellar medium because the quality of low-frequency observations has improved. One recent experiment designed to explore this emission is QUIJOTE. We study the spatial variations in the synchrotron emission in QUIJOTE MFI data by dividing the sky into physically separated regions. For this task, we first used a novel component-separation method based on artificial neural networks to clean the synchrotron maps. After training the network with simulations, we fit EE and BB spectra by assuming a power-law model. Then, we estimated the index α_S, the amplitude, and the ratio of the B and E amplitudes. When analyzing the real data, we found a clear spatial variation in the synchrotron properties throughout the sky at 11 GHz, consistent with previous analyses. We obtained a steeper index in the Galactic plane of α_ S ^ EE = -3.10 ± 0.30 and α_ S ^ BB = -3.10 ± 0.28 and a flatter index at high Galactic latitudes of α_ S ^ EE = -3.05 ± 0.16 and α_ S ^ B = -2.98 ± 0.23. We found average values throughout the sky of α_ S ^ EE = -3.04 ± 0.18 and α_ S ^ BB = -3.00 ± 0.26. Furthermore, after obtaining an average value of A_ S ^ EE = 3.31 ± 0.17 μ K^ 2 and A_ S ^ BB = 0.93 ± 0.04 μ K^ 2 , we estimated a ratio of the B and E amplitudes of A_ S ^ BB /A_ S ^ EE = 0.28 ± 0.06. Based on the results, we conclude that although neural networks appear to be valuable methods for application to real observations of the interstellar medium, in future QUIJOTE MFI2 data, combined analyses with , WMAP, and/or CBASS data are mandatory to reduce the noise contamination from QUIJOTE-estimated maps and then improve the accuracy of the estimations. Planck

The LiteBIRD satellite mission aims at detecting Cosmic Microwave Background B modes with unprecedented precision, targeting a total error on the tensor-to-scalar ratio r of delta r similar to 0.001. Operating from the L2 Lagrangian point of the Sun-Earth system, LiteBIRD will survey the full sky across 15 frequency bands (34 to 448 GHz) for 3 years.The current LiteBIRD baseline configuration employs 4508 detectors sampling at 19.1 Hz to achieve an effective polarization sensitivity of 2 mu K arcmin and an angular resolution of 31 arcmin (at 140 GHz). We describe the first release of the official LiteBIRD simulations, realized with a new simulation pipeline developed using the LiteBIRD Simulation Framework. This pipeline generates 500 full-sky simulated maps at a HEALPix resolution of N-side=512. The simulations include also one year of Time Ordered Data (TOD) for approximately one-third of LiteBIRD's total detectors.

Cosmic microwave background (CMB) photons are deflected by large-scale structure through gravitational lensing. This secondary effect introduces higher-order correlations in CMB anisotropies, which are used to reconstruct lensing deflections. This allows mapping of the integrated matter distribution along the line of sight, probing the growth of structure, and recovering an undistorted view of the last-scattering surface. Gravitational lensing has been measured by previous CMB experiments, with Planck's 42 s detection being the current best full-sky lensing map. We present an enhanced LiteBIRD lensing map by extending the CMB multipole range and including the minimum-variance estimation, leading to a 49 to 58 s detection over 80% of the sky, depending on the final complexity of polarized Galactic emission. The combination of Planck and LiteBIRD will be the best full-sky lensing map in the 2030s, providing a 72 to 78 s detection over 80% of the sky, almost doubling Planck's sensitivity. Finally, we explore different applications of the lensing map, including cosmological parameter estimation using a lensing-only likelihood and internal delensing, showing that the combination of both experiments leads to improved constraints. The combination of Planck + LiteBIRD will improve the S8 constraint by a factor of 2 compared to Planck, and Planck + LiteBIRD internal delensing will improve LiteBIRD's tensor-to-scalar ratio constraint by 6%. We have tested the robustness of our results against foreground models of different complexity, showing that improvements remain even for the most complex foregrounds.

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission focused on primordial cosmology and fundamental physics. In this paper, we present the LiteBIRD Simulation Framework (LBS), a Python package designed for the implementation of pipelines that model the outputs of the data acquisition process from the three instruments on the LiteBIRD spacecraft: LFT (Low-Frequency Telescope), MFT (Mid-Frequency Telescope), and HFT (High-Frequency Telescope). LBS provides several modules to simulate the scanning strategy of the telescopes, the measurement of realistic polarized radiation coming from the sky (including the Cosmic Microwave Background itself, the Solar and Kinematic dipole, and the diffuse foregrounds emitted by the Galaxy), the generation of instrumental noise and the effect of systematic errors, like pointing wobbling, non-idealities in the Half-Wave Plate, et cetera. Additionally, we present the implementation of a simple but complete pipeline that showcases the main features of LBS. We also discuss how we ensured that LBS lets people develop pipelines whose results are accurate and reproducible. A full end-to-end pipeline has been developed using LBS to characterize the scientific performance of the LiteBIRD experiment. This pipeline and the results of the first simulation run are presented in Puglisi et al. (2025).

We present and analyse the results of the Science Data Challenge 3a (SDC3a, https://sdc3.skao.int/challenges/foregrounds), an epoch of reionization (EoR) foreground-removal exercise organized by the Square Kilometre Array Observatory (SKAO) on SKA simulated data. The challenge ran for 8 months, from 2023 March to October. Participants were provided with realistic simulations of SKA-Low data between 106 and 196MHz, including foreground contamination from extragalactic and Galactic emission, instrumental, and systematic effects. They were asked to deliver cylindrical power spectra of the EoR signal, cleaned from all corruptions, and the corresponding confidence levels. Here, we describe the approaches taken by the 17 teams that completed the challenge, and we assess their performance using different metrics. The challenge results provide a positive outlook on the capabilities of current foreground-mitigation approaches to recover the faint EoR signal from SKA-Low observations. The median error committed in the EoR power spectrum recovery is below the true signal for seven teams, although in some cases, there are some significant outliers. The smallest residual overall is 4.2(-4.2)(+20) x10(-4) K(2)h(-3) cMpc(3) across all considered scales and frequencies. The estimation of confidence levels provided by the teams is overall less accurate, with the true error being typically underestimated, sometimes very significantly. The most accurate error bars account for 60 +/- 20 per cent of the true errors committed. The challenge results provide a means for all teams to understand and improve their performance. This challenge indicates that the comparison between independent pipelines could be a powerful tool to assess residual biases and improve error estimation.

This work focuses on the study of the anomalous microwave emission (AME), an important emission mechanism between 10 and 60,GHz whose polarisation properties are not yet fully understood and is therefore a potential contaminant for future cosmic microwave background (CMB) polarisation observations. We used new QUIJOTE-MFI maps at 11, 13, 17, and 19,GHz obtained from the combination of the public wide survey data and additional 1800,h of dedicated raster scan observations together with other public ancillary data, including WMAP and Planck to study the polarisation properties of the AME in three Galactic regions: ρ,Ophiuchi, Perseus, and W43. We obtained the spectral energy distributions (SEDs) of the three regions over the frequency range $0.4--3000$,GHz in intensity and polarisation. The intensity SEDs are well described by a combination of free-free emission, thermal dust, AME, and CMB anisotropies. In polarisation, we extracted the flux densities using all available data between 11 and 353,GHz. We implemented an improved intensity-to-polarisation leakage correction that allowed reliable polarisation constraints well below the 1% level from Planck -LFI data to be derived for the first time. A frequency stacking of maps in the range 10--60,GHz allowed us to reduce the statistical noise and to push the upper limits on the AME polarisation level. We obtained upper limits on the AME polarisation fraction of the order lesssim 1% (95% confidence level) for the three regions. In particular, we obtained AME < 1.0% (at 28.4,GHz) AME < 0.9% (at 28.4,GHz), and AME < 0.28% (at 33,GHz) in ρ,Ophiuchi, Perseus, and W43, respectively. At the QUIJOTE 17,GHz frequency band, we found AME < 5.0% for ρ,Ophiuchi AME < 3.4% for Perseus, and Π_ AME < 0.85% for W43. We note that for the ρ,Ophiuchi molecular cloud, the new QUIJOTE-MFI data allowed us to set the first constraints on the AME polarisation in the range 10--20,GHz. Our final upper limits derived using the stacking procedure are AME < 0.58% for ρ,Ophiuchi AME < 0.67% for Perseus, and Π_ AME < 0.31% for W43. Altogether, these are the most stringent constraints to date on the AME polarisation fraction of these three star-forming regions.

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015-2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14,000 deg^2 of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.