Eirik Gjerløw

• Bortolami, M.; Raffuzzi, N.; Pagano, L.; Puglisi, G.; Anand, A. & Banday, A.J. [Show all 110 contributors for this article] (2025). First release of LiteBIRD simulations from an end-to-end pipeline. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/042. Full text in Research Archive Show summary

  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 δr ∼ 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 μK 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 Nside=512. The simulations include also one year of Time Ordered Data (TOD) for approximately one-third of LiteBIRD's total detectors.

• Kypriotakis, John A.; Joshi, Bhushan; Blinov, Dmitry; Kiehlmann, Sebastian; Anche, Ramya M. & Liodakis, Ioannis [Show all 22 contributors for this article] (2025). Wide area linear optical polarimeter control software. Journal of Astronomical Telescopes, Instruments, and Systems (JATIS). ISSN 2329-4124. 11(3). doi: 10.1117/1.jatis.11.3.037001. Full text in Research Archive Show summary

  The WALOPControl software is designed to facilitate comprehensive control and operation of the Wide Area Linear Optical Polarimeter (WALOP) polarimeters, ensuring safe and concurrent management of various instrument components and functionalities. This software encompasses several critical requirements, including control of the filter wheel, calibration half-wave plate, calibration polarizer, guider positioning, focusers, and four concurrent charge-coupled device cameras. It also manages the host telescope and dome operations while logging operational parameters, user commands, and environmental conditions for troubleshooting and stability. It provides a user-friendly graphical user interface and secure access control, a notification system for errors, and a modular configuration for troubleshooting that are integral to the software’s architecture. It is accessible over the internet with the backend developed using NodeJS and ExpressJS, featuring a RESTful API that interacts with a MongoDB database, facilitating real-time status updates and data logging. The frontend utilizes the React.JS framework, with Redux for state management and Material UI for the graphical components. The system also allows for automatic observations based on user-defined schedules. A continuous integration and continuous deployment pipeline ensures the software’s reliability through automated testing and streamlined deployment. The WALOPControl software is a key component of the Polar-Areas Stellar Imaging in Polarimetry High Accuracy Experiment project, which aims to study the dust and magnetic field of the Milky Way by observing the polarization of starlight.

• Aurvik, Ragnhild; Galloway, Mathew; Gjerløw, Eirik; Fuskeland, Unni; Basyrov, Artem & Bortolami, M. [Show all 110 contributors for this article] (2025). On the computational feasibility of Bayesian end-to-end analysis of LiteBIRD simulations within Cosmoglobe. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/041. Full text in Research Archive Show summary

  We assess the computational feasibility of end-to-end Bayesian analysis of the JAXA-led LiteBIRD experiment by analysing simulated time ordered data (TOD) for a subset of detectors through the Cosmoglobe and Commander3 framework. The data volume for the simulated TOD is 1.55 TB, or 470 GB after Huffman compression. From this we estimate a total data volume of 238 TB for the full three year mission, or 70 TB after Huffman compression. We further estimate the running time for one Gibbs sample, from TOD to cosmological parameters, to be approximately 3000 CPU hours. The current simulations are based on an ideal instrument model, only including correlated 1/ f noise. Future work will consider realistic systematics with full end-to-end error propagation. We conclude that these requirements are well within capabilities of future high-performance computing systems.

• Tomasi, M.; Pagano, L.; Anand, A.; Baccigalupi, C.; Banday, A.J. & Bortolami, M. [Show all 114 contributors for this article] (2025). A simulation framework for the LiteBIRD instruments. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(11). doi: 10.1088/1475-7516/2025/11/040. Full text in Research Archive Show summary

  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).

• Carralot, F.; Carones, A.; Krachmalnicoff, N.; Ghigna, T.; Novelli, A. & Pagano, L. [Show all 109 contributors for this article] (2025). Requirements on the gain calibration for LiteBIRD polarisation data with blind component separation. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(1). doi: 10.1088/1475-7516/2025/01/019. Full text in Research Archive Show summary

  The detection of primordial B modes of the cosmic microwave background (CMB) could provide information about the early stages of the Universe's evolution. The faintness of this signal requires exquisite calibration accuracy and control of instrumental systematic effects which otherwise could bias the measurements. In this work, we study the impact of an imperfect relative polarisation gain calibration on the recovered value of the tensor-to-scalar ratio r for the LiteBIRD experiment, through the application of the blind Needlet Internal Linear Combination (NILC) foreground-cleaning method. We derive requirements on the relative calibration accuracy of the overall polarisation gain (Δgν) for each LiteBIRD frequency channel. Our results show that minimum variance techniques, as NILC, are less sensitive to systematic gain calibration uncertainties compared to a parametric approach, if the latter is not equipped with a proper modelling of these instrumental effects. In this study, the most stringent requirements are found in the channels where the CMB signal is relatively brighter, with the tightest constraints at 166 GHz (Δgν ≈ 0.16%). This differs from the outcome of an analogous analysis performed with a parametric method, where the tightest requirements are obtained for the foreground-dominated channels. Gain calibration uncertainties, corresponding to the derived requirements, are then simultaneously propagated into all frequency channels. By doing so, we find that the overall impact on estimated r is lower than the total gain systematic budget for LiteBIRD approximately by a factor 5, due to the correlations of the impacts of gain calibration uncertainties in different frequency channels. In order to decouple the systematic effect from the specific choice of the model, we derive the requirements assuming constant spectral parameters for the foreground emission. To assess the robustness of the obtained results against more realistic scenarios, we repeat the analysis assuming sky models of intermediate and high complexity. In these further cases, we adopt an optimised NILC pipeline, called the Multi-Clustering NILC (MC-NILC). We find that the impact of gain calibration uncertainties on r is lower than the LiteBIRD gain systematics budget for the intermediate-complexity sky model. For the high-complexity case, instead, it would be necessary to tighten the requirements by a factor 1.8.

• Hoz, E. de la; Diego-Palazuelos, P.; Errard, J.; Gruppuso, A.; Jost, B. & Sullivan, Raelyn [Show all 115 contributors for this article] (2025). LiteBIRD science goals and forecasts: constraining isotropic cosmic birefringence. Journal of Cosmology and Astroparticle Physics (JCAP). 2025(7). doi: 10.1088/1475-7516/2025/07/083. Full text in Research Archive Show summary

  Cosmic birefringence (CB) is the rotation of the photons' linear polarisation plane during propagation. Such an effect is a tracer of parity-violating extensions of standard electromagnetism and would probe the existence of a new cosmological field acting as dark matter or dark energy. It has become customary to employ cosmic microwave background (CMB) polarised data to probe such a phenomenon. Recent analyses on Planck and WMAP data provide a hint of detection of the isotropic CB angle with an amplitude of around 0.3° at the level of 2.4 to 3.6σ. In this work, we explore the LiteBIRD capabilities in constraining such an effect, accounting for the impact of the more relevant systematic effects, namely foreground emission and instrumental polarisation angles. We build five semi-independent pipelines and test these against four different simulation sets with increasing complexity in terms of non-idealities. All the pipelines are shown to be robust and capable of returning the expected values of the CB angle within statistical fluctuations for all the cases considered. We find that the uncertainties in the CB estimates increase with more complex simulations. However, the trend is less pronounced for pipelines that account for the instrumental polarisation angles. For the most complex case analysed, we find that LiteBIRD will be able to detect a CB angle of 0.3° with a statistical significance ranging from 5 to 13σ, depending on the pipeline employed, where the latter uncertainty corresponds to a total error budget of the order of 0.02°.

• Remazeilles, M.; Douspis, M.; Rubiño-Martín, J.A.; Banday, A.J.; Chluba, J. & Bernardis, P. de [Show all 107 contributors for this article] (2024). LiteBIRD science goals and forecasts. Mapping the hot gas in the Universe. Journal of Cosmology and Astroparticle Physics (JCAP). 2024(12). doi: 10.1088/1475-7516/2024/12/026. Full text in Research Archive Show summary

  We assess the capabilities of the LiteBIRD mission to map the hot gas distribution in the Universe through the thermal Sunyaev-Zeldovich (SZ) effect. Our analysis relies on comprehensive simulations incorporating various sources of Galactic and extragalactic foreground emission, while accounting for the specific instrumental characteristics of the LiteBIRDmission, such as detector sensitivities, frequency-dependent beam convolution, inhomogeneous sky scanning, and 1/f noise. We implement a tailored component-separation pipeline to map the thermal SZ Compton y-parameter over 98% of the sky. Despite lower angular resolution for galaxy cluster science, LiteBIRD provides full-sky coverage and, compared to the Plancksatellite, enhanced sensitivity, as well as more frequency bands to enable the construction of an all-sky thermal SZ y-map, with reduced foreground contamination at large and intermediate angular scales. By combining LiteBIRD and Planck channels in the component-separation pipeline, we also obtain an optimal y-map that leverages the advantages of both experiments, with the higher angular resolution of the Planck channels enabling the recovery of compact clusters beyond the LiteBIRD beam limitations, and the numerous sensitive LiteBIRD channels further mitigating foregrounds. The added value ofLiteBIRD is highlighted through the examination of maps, power spectra, and one-point statistics of the various sky components. After component separation, the 1/f noise fromLiteBIRD's intensity channels is effectively mitigated below the level of the thermal SZ signal at all multipoles. Cosmological constraints on S8 = σ8 (Ωm/0.3)0.5 obtained from the LiteBIRD-Planck combined y-map power spectrum exhibits a 15 % reduction in uncertainty compared to constraints derived fromPlanck alone. This improvement can be attributed to the increased portion of uncontaminated sky available in the LiteBIRD-Planck combined y-map.

• Ghigna, T.; Adler, A.; Aizawa, K.; Akamutsu, H.; Akizawa, R. & Allys, E. [Show all 157 contributors for this article] (2024). The LiteBIRD mission to explore cosmic inflation. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 13092. doi: 10.1117/12.3021377. Full text in Research Archive Show summary

  LiteBIRD, the next-generation cosmic microwave background (CMB) experiment, aims for a launch in Japan’s fiscal year 2032, marking a major advancement in the exploration of primordial cosmology and fundamental physics. Orbiting the Sun-Earth Lagrangian point L2, this JAXA-led strategic L-class mission will conduct a comprehensive mapping of the CMB polarization across the entire sky. During its 3-year mission, LiteBIRD will employ three telescopes within 15 unique frequency bands (ranging from 34 through 448 GHz), targeting a sensitivity of 2.2 μK-arcmin and a resolution of 0.5° at 100 GHz. Its primary goal is to measure the tensor-toscalar ratio r with an uncertainty δr = 0.001, including systematic errors and margin. If r ≥ 0.01, LiteBIRD expects to achieve a > 5σ detection in the ℓ = 2–10 and ℓ = 11–200 ranges separately, providing crucial insight into the early Universe. We describe LiteBIRD’s scientific objectives, the application of systems engineering to mission requirements, the anticipated scientific impact, and the operations and scanning strategies vital to minimizing systematic effects. We will also highlight LiteBIRD’s synergies with concurrent CMB projects.

• Maharana, Siddharth; Ramaprakash, A.N.; Rajarshi, Chaitanya; Khodade, Pravin; Joshi, Bhushan & Chordia, Pravin [Show all 31 contributors for this article] (2024). Systems design, assembly, integration, and lab testing of WALOP-South Polarimeter. Proceedings of SPIE, the International Society for Optical Engineering. ISSN 0277-786X. 13096. doi: 10.1117/12.3016144. Full text in Research Archive Show summary

  Wide-Area Linear Optical Polarimeter (WALOP)-South is the first wide-field and survey-capacity polarimeter in the optical wavelengths. On schedule for commissioning in 2024, it will be mounted on the 1 m SAAO telescope in Sutherland Observatory, South Africa to undertake the PASIPHAE sky survey. PASIPHAE program will create the first polarimetric sky map in the optical wavelengths, spanning more than 2000 square degrees of the southern Galactic region. In a single exposure, WALOP-South’s innovative design will enable it to measure the linear polarization (Stokes parameters q and u) of all sources in a field of view (FoV) of 35 × 35 arc-minutes-squared in the SDSS-r broadband and narrowband filters between 500-750 nm with 0.1 % polarization accuracy. The unique goals of the instrument place very stringent systems engineering goals, including on the performance of the optical, polarimetric, optomechanical, and electronic subsystems. In particular, the major technical hurdles for the project included the development of: (a) an optical design to achieve imaging quality PSFs across the FoV, (b) an optomechanical design to obtain high accuracy optical alignment in conjugation with minimal instrument flexure and stress birefringence on optics (which can lead to variable instrumental polarization), and (c) an on-sky calibration routine to remove the strong polarimetric cross-talk induced instrumental polarization to obtain 0.1% across the FoV. All the subsystems have been designed carefully to meet the overall instrument performance goals. As of May 2024, all the instrument optical and mechanical subsystems have been assembled and are currently getting tested and integrated. The complete testing and characterization of the instrument in the lab is expected to be completed by August 2024. While the instrument was initially scheduled for commissioning in 2022, it got delayed due to various technical challenges; WALOP-South is now on schedule for commissioning in second half of 2024. In this paper, we will present (a) the design and development of the entire instrument and its major subsystems, focusing the instrument’s opto-mechanical design which has not been reported before, and (b) assembly and integration of the instrument in the lab and early results from lab characterization of the instrument’s optical performance.

• Pelgrims, V.; Mandarakas, N.; Skalidis, R.; Tassis, K.; Panopoulou, G.V. & Pavlidou, V. [Show all 24 contributors for this article] (2024). The first degree-scale starlight-polarization-based tomography map of the magnetized interstellar medium. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 684. doi: 10.1051/0004-6361/202349015. Full text in Research Archive Show summary

  We present the first degree-scale tomography map of the dusty magnetized interstellar medium (ISM) from stellar polarimetry and distance measurements. We used the RoboPol polarimeter at Skinakas Observatory to conduct a survey of the polarization of starlight in a region of the sky of about four square degrees. We propose a Bayesian method to decompose the stellar-polarization source field along the distance to invert the three-dimensional (3D) volume occupied by the observed stars. We used this method to obtain the first 3D map of the dusty magnetized ISM. Specifically, we produced a tomography map of the orientation of the plane-of-sky component of the magnetic field threading the diffuse, dusty regions responsible for the stellar polarization. For the targeted region centered on Galactic coordinates (l, b) ≈ (103.3°, 22.3°), we identified several ISM clouds. Most of the lines of sight intersect more than one cloud. A very nearby component was detected in the foreground of a dominant component from which most of the polarization signal comes and which we identified as being an intersection of the wall of the Local Bubble and the Cepheus Flare. Farther clouds, with a distance of up to 2 kpc, were similarly detected. Some of them likely correspond to intermediate-velocity clouds seen in H I spectra in this region of the sky. We found that the orientation of the plane-of-sky component of the magnetic field changes along distance for most of the lines of sight. Our study demonstrates that starlight polarization data coupled to distance measures have the power to reveal the great complexity of the dusty magnetized ISM in 3D and, in particular, to provide local measurements of the plane-of-sky component of the magnetic field in dusty regions. This demonstrates that the inversion of large data volumes, as expected from the PASIPHAE survey, will provide the necessary means to move forward in the modeling of the Galactic magnetic field and of the dusty magnetized ISM as a contaminant in observations of the cosmic microwave background polarization.

View all works in NVA