The European Space Agency has selected PLATO (PLAnetary Transits and Oscillations of stars) for its M3 launch which is scheduled for 2026. With its extremely large field of view, PLATO is designed to obtain photometric measurements over an extended period for bright stars in order to detect and characterise (primarily) rocky planets in the habitable zones of solar type stars. The PLATO measurements will have sufficient sensitivity to determine the mass, radius and age of the host stars with unprecedented accuracy. The PLATO planet database will provide the first large-scale catalogue of accurately and homogeneously characterised small planets at intermediate orbital periods, which will can be used to severely constraint planet formation theories. This would facilitate large scale comparative exo-planetology. In addition the bright PLATO host stars will be ideal targets for atmospheric study with next generation facilities such as the ELT. The PLATO sensitivity will be sufficient to detect pulsations from stars across the HR diagram allowing a deep understanding of stellar structure and evolution to be developed using parameters determined from asteroseismology.

PLATO (PLAnetary Transits and Oscillations of stars)1 is the M3 class ESA mission dedicated to the discovery and study of extrasolar planetary systems by means of planetary transits detection. PLATO Payload Camera units are integrated and vibrated at CSL before being TVAC tested for thermal acceptance and performance verification at 3 different test facilities (SRON, IAS and INTA). 15 of the 26 Flight Cameras were integrated, tested and delivered to ESA for integration by the Prime between June 2023 and June 2024, with the remaining flight units to be tested by the end of 2024. In this paper, we provide an overview of our serial testing approach, some of the associated challenges, key performance results and an up-to-date status on the remaining planned activities.

PLATO (PLAnetary Transits and Oscillations of stars) is an M3 medium-class space mission in ESA's Cosmic Vision program devoted to detecting and studying a large number of extrasolar planetary systems. Its launch is planned for the end of 2026 from Europe's Spaceport in French Guiana. The PLATO Payload consists of 26 wide field-of-view Cameras, each observing a specific part of the sky, associated data processing units and power supply units. The 24 Normal-Cameras will provide a very high-resolution photometric measurement of light from a large number of stars, while the other two Fast Cameras will provide the colour information and will deliver the pointing data to the AOCS (Attitude and Orbital Control System). The Cameras will be integrated into an optical bench. Each of them is composed of the Telescope Optical Unit (TOU), the Focal Plane Assembly (FPA) and the Front-End Electronics (FEE). Currently, the serial production of the Cameras has already started facing critical key points, non-conformities and challenging problems. The status of the Product Assurance activities during the serial production for which the first flight models are being delivered after the AIT phase is reported.

In the context of PLATO Camera Subsystem development, it has been decided to take advantage of MBSE methodologies using Enterprise Architect by Sparx Systems as tool. A Local SysML Camera model for PLATO mission(1) has been built from different Excel spreadsheets, i.e. Verification Control Matrices, released by Subsystems. Same approach has been used for the Camera-System itself. The complete flow-down of requirements has been created in order to easily identify and monitor any impact on the design due to changes, deviations and non-compliances. The model can be updated at any time importing Excel spreadsheet while it can be used as source to export documentation needed during formal reviews, both as Word and Excel files. In addition, Model architecture and constraints have been created through Block Definition Diagram and Internal Block Diagram so that structure, interfaces as well as interaction between different items, can be easily identified and monitored at both System and Subsystem level.

PLATO (PLAnetary Transits and Oscillation of Starts) is the third medium class mission of ESA devoted to exoplanets detection and partial characterization together to the associated star activity evaluation through its astroseismology. It is consisting on 26 telescopes mounted on the same platform, 24 called 'normal' and composed of four full-frame CCDs and 2 'fast' composed of four frame-transfer CCDs mounted on their respective focal plane assemblies (FPAs). For completing the detection chain, they are using their front-end electronics (FEE), being the optics and opto-mechanics of the telescope optical unit (TOU) the last element of the PLATO-CAMs. In the framework of the mission development, the PLATO-CAMs, after their proper alignment and assembly, are required to be calibrated and tested on simulated working conditions. INTA is one of the European institutions (together to IAS and SRON, in France and Netherlands, respectively), in which such telescopes testing and calibration is carried out by simulating the L2 conditions corresponding to the PLATO-CAMs working environment. In this paper, the setup preparation for PLATO-CAM calibration and testing details are reported on, including design, and fabrication of the different elements, all the ground support equipment (GSE) required for the PLATO-CAMs full characterization and performance evaluation. In addition, the results on the first model tested at INTA, the engineering model (EM) are summarized.

PLATO (Planetary Transits and Oscillation of Stars) will be used for finding the hugest amount of exoplanets ever found and to characterize them together to the associated star activity evaluation through its astroseismology. For such a purpose, 26 telescopes will be mounted on the same platform: 24 of them, called 'normal' and composed of four full-frame CCDs and the last 2, known as 'fast' composed of four frame-transfer CCDs. In both cases, CCDs will be installed on their respective focal plane assemblies (FPAs). For completing the detection chain, they are using their front end electronics (FEE), being the optics and opto-mechanics of the telescope optical unit (TOU) the last element of the PLATO CAMs. As a part of the payload development, assembly, integration and test, the PLATO CAMs are required to be calibrated and tested on simulated working conditions. INTA is one of the European institutions (together to IAS and SRON, in France and Netherlands, respectively), in which such telescopes testing and calibration is carried out. As a part of the product assurance activities, a protocol for reaching safe conditions on the telescopes during TVAC (thermal vacuum) testing under any unexpected and dangerous event happening was prepared. In this paper, we are describing the need of the protocol activation for answering to one of the worst events that could be present during a TVAC testing campaign: an unexpected power outage making the vacuum pumps critically fail. The room conditions recovered in a safe way is reported on.

The preparation of the different institutes (IAS, SRON and INTA at France, Netherlands and Spain, respectively) for being ready for testing the PLATO (Planetary transits and oscillation of starts) telescopes (PLATO CAMs) under working condition has been a long trip full of requirements updates and needs adaptation. For this ESA mission devoted to the Exoplanets detection and partial characterization together to the associated star activity evaluation through its astroseismology, 26 telescopes are going to be mounted on the same platform. There are 24 identical 'normal' and 2 'fast' PLATO CAMs, all formed by four CCDs mounted on the focal plane assembly (FPA), the front end electronics (FEE) used for completing the detection chain, and optics and optomechanics that forms the telescopes optical unit (TOU). After their alignment and integration verification done at CSL, they are sent to the corresponding institute for running at the best focus temperature at which the telescope provides the best image the performance checks required for considering them properly characterized and ready to be installed in their final configuration at OHB. In this paper, a brief summary on the main details of the tests carried out at INTA on the PLATO CAM flight model (FM) number three are reported on. In addition, preliminary results obtained together to the rest of the consortium and related to the telescopes capabilities are included for the particular case of such first flight model tested at INTA.

In 2021 BL Lacertae underwent an extraordinary activity phase, which was intensively followed by the Whole Earth Blazar Telescope (WEBT) Collaboration. We present the WEBT optical data in the BVRI bands acquired at 36 observatories around the world. In mid 2021 the source showed its historical maximum, with R = 11.14. The light curves display many episodes of intraday variability, whose amplitude increases with source brightness, in agreement with a geometrical interpretation of the long-term flux behaviour. This is also supported by the long-term spectral variability, with an almost achromatic trend with brightness. In contrast, short-term variations are found to be strongly chromatic and are ascribed to energetic processes in the jet. We also analyse the optical polarimetric behaviour, finding evidence of a strong correlation between the intrinsic fast variations in flux density and those in polarisation degree, with a time delay of about 13 h. This suggests a common physical origin. The overall behaviour of the source can be interpreted as the result of two mechanisms: variability on time scales greater than several days is likely produced by orientation effects, while either shock waves propagating in the jet, or magnetic reconnection, possibly induced by kink instabilities in the jet, can explain variability on shorter time scales. The latter scenario could also account for the appearance of quasi-periodic oscillations, with periods from a few days to a few hours, during outbursts, when the jet is more closely aligned with our line of sight and the time scales are shortened by relativistic effects.

Blazars are active galactic nuclei (AGN) with relativistic jets whose non-thermal radiation is extremely variable on various timescales1-3. This variability seems mostly random, although some quasi-periodic oscillations (QPOs), implying systematic processes, have been reported in blazars and other AGN. QPOs with timescales of days or hours are especially rare4 in AGN and their nature is highly debated, explained by emitting plasma moving helically inside the jet5, plasma instabilities6,7 or orbital motion in an accretion disc7,8. Here we report results of intense optical and γ-ray flux monitoring of BL Lacertae (BL Lac) during a dramatic outburst in 2020 (ref. 9). BL Lac, the prototype of a subclass of blazars10, is powered by a 1.7 × 108 MSun (ref. 11) black hole in an elliptical galaxy (distance = 313 megaparsecs (ref. 12)). Our observations show QPOs of optical flux and linear polarization, and γ-ray flux, with cycles as short as approximately 13 h during the highest state of the outburst. The QPO properties match the expectations of current-driven kink instabilities6 near a recollimation shock about 5 parsecs (pc) from the black hole in the wake of an apparent superluminal feature moving down the jet. Such a kink is apparent in a microwave Very Long Baseline Array (VLBA) image.

The ExoClock project is an inclusive, integrated, and interactive platform that was developed to monitor the ephemerides of the Ariel targets to increase the mission efficiency. The project makes the best use of all available resources, i.e., observations from ground telescopes, midtime values from the literature, and finally, observations from space instruments. Currently, the ExoClock network includes 280 participants with telescopes capable of observing 85% of the currently known Ariel candidate targets. This work includes the results of ∼1600 observations obtained up to 2020 December 31 from the ExoClock network. These data in combination with ∼2350 midtime values collected from the literature are used to update the ephemerides of 180 planets. The analysis shows that 40% of the updated ephemerides will have an impact on future scheduling as either they have a significantly improved precision or they have revealed biases in the old ephemerides. With the new observations, the observing coverage and rate for half of the planets in the sample has been doubled or more. Finally, from a population perspective, we identify that the differences in the 2028 predictions between the old and the new ephemerides have an STD that is double what is expected from Gaussian uncertainties. These findings have implications for planning future observations, where we will need to account for drifts potentially greater than the prediction uncertainties. The updated ephemerides are open and accessible to the wider exoplanet community both from our Open Science Framework repository and our website.

PLATO (PLAnetary Transits and Oscillations of stars) is a European Space Agency medium class mission, whose launch is foreseen for 2026. Its primary goal is to discover and characterise terrestrial exoplanets orbiting the habitable zone of their host stars. This goal will be reached with a set of 26 wide field-of-view cameras mounted on a common optical bench. Here we show some results of the first cryogenic vacuum test campaign made on the Engineering Model (EM) of one PLATO camera, performed at the Netherlands Institute for Space Research (SRON). In particular we present the search for the best focus temperature, which was done first by using a Hartmann mask, and then by maximizing the ensquared energy fractions of the point spread functions (PSFs) on the entire field of view taken at different temperature plateaus. Furthermore we present the PSF properties of the EM at the nominal focus temperature over all the field of view, focusing on the ensquared energy fractions. The Engineering Model camera was successfully integrated and validated under cryo-vacuum tests, allowing the mission to pass ESA's Critical Milestone, and confirming the mission is on track for launch in 2026.

Context. A stellar occultation by Neptune’s main satellite, Triton, was observed on 5 October 2017 from Europe, North Africa, and the USA. We derived 90 light curves from this event, 42 of which yielded a central flash detection. Aims. We aimed at constraining Triton’s atmospheric structure and the seasonal variations of its atmospheric pressure since the Voyager 2 epoch (1989). We also derived the shape of the lower atmosphere from central flash analysis. Methods. We used Abel inversions and direct ray-tracing code to provide the density, pressure, and temperature profiles in the altitude range ~8 km to ~190 km, corresponding to pressure levels from 9 µbar down to a few nanobars. Results. (i) A pressure of 1.18 ± 0.03 µbar is found at a reference radius of 1400 km (47 km altitude). (ii) A new analysis of the Voyager 2 radio science occultation shows that this is consistent with an extrapolation of pressure down to the surface pressure obtained in 1989. (iii) A survey of occultations obtained between 1989 and 2017 suggests that an enhancement in surface pressure as reported during the 1990s might be real, but debatable, due to very few high S/N light curves and data accessible for reanalysis. The volatile transport model analysed supports a moderate increase in surface pressure, with a maximum value around 2005-2015 no higher than 23 µbar. The pressures observed in 1995-1997 and 2017 appear mutually inconsistent with the volatile transport model presented here. (iv) The central flash structure does not show evidence of an atmospheric distortion. We find an upper limit of 0.0011 for the apparent oblateness of the atmosphere near the 8 km altitude.