The Ariel space mission, set to launch in 2029, will conduct the first homogenous spectroscopic survey of hundreds of exoplanets in the visible and infrared, as the M4 mission of ESA’s Cosmic Vision. Since before adoption, Ariel has developed advanced simulators able to model the expected performance of the payload and complex astrophysical and instrumental systematics, including pointing jitter, to demonstrate compliance with scientific requirements ahead of launch. ExoSim2 can simulate an end-to-end observation in the time domain, from the astrophysical source to the focal planes of the instruments, producing photometric and spectroscopic timelines of science frames as will be collected by Ariel. The PSFs vs wavelength at each instrument focal plane are calculated using PAOS, an open-source generic physical optics propagation code able to model the propagation of the electromagnetic field through complex optical systems, including off-axis ones.  The early development of these advanced simulators was motivated by the desire to avoid unnecessary complexity in the payload design, thereby minimizing potential risks to the mission. We report on the recent study of Ariel jitter detrending as an example of space mission preparation through the application of simulators.

How to cite: Bocchieri, A. and Mugnai, L. V.: Leveraging advanced simulators to optimize the Ariel space mission preparation, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-224, https://doi.org/10.5194/epsc-dps2025-224, 2025.

The forthcoming Ariel space mission will conduct the first spectroscopic survey of the atmospheres of hundreds of exoplanets in the visible and infrared bands of the electromagnetic spectrum. The mission is currently in Phase C and a Dry-Run exercise is ongoing to assess early preparedness and highlight key areas for further work ahead of launch in 2029. The Ariel-IT community has set up an end-to-end procedure from target identification to simulated primary transit observations and retrieval. The current focus is on a sample of hot Jupiters and planets orbiting active stars, with key activities including determination of stellar and planetary properties, planetary formation and evolution models, star-planet interaction, atmospheric evolution, and spectral synthesis. These simulations are passed as inputs to the latest version of the exoplanet observation simulator, ExoSim2, alongside the Ariel payload description and the PSFs vs wavelength for each instrument and focal plane generated with PAOS, a generic open-source physical optics simulator. ExoSim2 produces photometric and spectroscopic timelines of a simulated Ariel observation in the time domain, including the effects of stellar activity and jitter in the spacecraft's line of sight, a source of disturbance when measuring the spectra of exoplanet atmospheres. Our preliminary results for WASP-69b showcase the ability to achieve photon noise-limited observations across the entire Ariel spectrum post-processing and the possibility to discriminate between different input atmospheric compositions in the studied cases. Current limitations will be discussed along with the next steps needed to complete the analysis of our sample.

How to cite: Bocchieri, A., Lorenzani, A., Petralia, A., Pascale, E., and Micela, G.: Ariel-IT end-to-end exercise from the astrophysical scene to planetary spectra: simulations and retrieval, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-384, https://doi.org/10.5194/epsc-dps2025-384, 2025.

How to cite: Moretto, G., Langlois, M., Kuhn, J., Lodieu, N., Rebolo, R., Rolland, J., Zhou, Y., Fonteneau, V., and Graf, C.:  The ExoLife Finder (ELF) telescope project — a cutting-edge hybrid interferometer telescope explicitly designed for the high-contrast direct detection of exoplanets. , EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1382, https://doi.org/10.5194/epsc-dps2025-1382, 2025.

Recent advancements in high-contrast exoplanet imaging have opened the door to adaptive coronagraphy, a new approach that leverages the use of active optical components to dynamically adapt to science goals or observing conditions, for example, to observe multiple star systems. Enabling technologies include liquid-crystal-on-silicon (LCoS) spatial light modulators (SLMs) as programmable focal-plane phase masks (FPMs), or digital micro-mirror devices (DMDs) as dynamic pupil apodizers.

However, these active devices introduce new challenges, such as limitations in spatial resolution, phase precision and accuracy, as well as extra weaknesses due to their pixelated and scalar nature. In this contribution, we present the detailed performance parameter space for pixelated FPM coronagraphs (see Figure 1). We are notably studying the impacts of key parameters such as spatial sampling, phase resolution and stability, and a few typical calibration errors. Using SLM-based systems as a case study, we evaluate several FPM coronagraphs: vortex masks, four-quadrant phase mask (FQPM), Roddier & Roddier and its dual-zone equivalent, and azimuthal cosine masks (ACM). Both monochromatic and broadband (20 percent bandwidth) conditions are considered. Scenarios with and without central telescope obstructions are also assessed, along with varying Lyot stop sizing parameters. Performance is quantified using metrics such as raw contrast (η_*), throughput (η_p), and the throughput-to-contrast ratio η_p/√η_* , which serves as a proxy for signal-to-noise on an off-axis point source.

Our findings shed light on the error budgets and fundamental trade-offs inherent to pixelated FPM coronagraphs. This is particularly timely with the upcoming first light of the Programmable Liquid-crystal Active Coronagraphic Imager for the 4-m DAG telescope (PLACID) instrument, which will be the first active high-contrast direct imaging instrument to field a LCOS SLM as a programmable digital FPM, operating in the H- to Ks-band. However, the lessons learned from this work may also provide valuable insights beyond the sole use of SLM panels, for instance to printed discretized FPMs or to other future photonic modulators that may exhibit sufficiently fine actuator pitch for focal-plane coronagraphy.

Figure 1, Illustration of the discretization for 8 commonly used coronagraphic FPMs, assuming 10 pixels per diffraction beamwidth: vortex with topographic charge 2, 4, 6 and 8, four-quadrant phase mask (FQPM), Roddier & Roddier, dual zone and azimuthal cosine mask (ACM) with charge 2.

Figure 2, SNR estimate for various coronagraphs in realistic conditions (20% broadband light, DAG telescope pupil with central obstruction, 10 SLM pixels per λ/D, 8-bits digitization). SNR of planetary companion is proportional to ~ η_p /√η_* , where η_p is the throughput on an off-axis companion and η_* is the transmission on the on-axis host star (null depth).

How to cite: Lin, L., Kühn, J., Potier, A., Tandon, R., and Marquis, L.: Simulating Pixelated Focal-Plane Phase Masks for Coronagraphic High-Contrast Imaging, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-127, https://doi.org/10.5194/epsc-dps2025-127, 2025.

ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) is an ESA mission scheduled for launch around 2030, aimed at investigating the atmospheres of exoplanets through infrared spectroscopy. To support the ground qualification of the Primary Mirror - Structural Model (M1 - SM), INAF – Osservatorio Astronomico di Palermo is converting the historic XACT (X-ray Astronomy Calibration and Test) chamber into a cryogenic vacuum facility dedicated to low-temperature, high-vacuum testing.

The new facility will operate at pressures of 7×10^-7 mbar and reach cryogenic temperatures ∼90 K, achieved through a Helium recirculation cooling system. The setup will be measured using a 4D technology interferometer, capable of rapidly capturing the surface shape of the mirror while minimizing the influence of environmental fluctuations during the measurement process. The test campaign will provide key data on the temperature distribution over the mirror and support the validation of thermal and mechanical FEM (Finite Element Method) models developed for the mission, both with and without flexure-based mounting systems.

The infrastructure is fully compatible with the SM's mounting and handling requirements and has been designed to be reconvertible for future XACT applications, ensuring experimental flexibility. Local execution of the test campaign on M1 SM will allow direct validation of the component’s behavior under realistic environmental conditions, reducing the reliance on simulations alone and contributing to optimizing the final flight configuration.

The facility will remain available for future test campaigns involving optical and structural components intended for space applications in visible and Infrared wavelengths, reinforcing INAF Palermo’s role as a national reference center for vacuum and cryogenic environmental qualification.

How to cite: Guerriero, E., D'Anca, F., Collura, A., Micela, G., Scippa, A., Fernandez, A. J., Perez, J., Pace, E., Preti, G., Picchi, P., Tozzi, A., Filizzolo, M., Varisco, S., Saitta, C., Gulizzi, A., Cardinale, D. V., Todaro, M., Sciortino, L., Lo Cicero, U., and Barbera, M. and the Ariel Telescope Assembly Team, INAF Laboratory of Palermo & ASI Ariel TEAM: Development of a Cryogenic Vacuum Facility for Structural and Thermal Testing of ARIEL’s Primary Mirror (M1 SM) at INAF Palermo, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-567, https://doi.org/10.5194/epsc-dps2025-567, 2025.

Ariel is a European Space Agency (ESA) mission that aims to study the atmospheres of a large and diverse sample of transiting exoplanets (Tinetti et al. 2021).  Scheduled for launch in 2029 to the L2 Lagrange point. Ariel will observe exoplanets in visible and near-infrared wavelengths (0.5–7.8 µm) via low-resolution spectroscopy. Ariel will use various spectroscopic techniques, including transmission and emission spectroscopy during transits and eclipses, as well as phase curve observations. These measurements will reveal wavelength-dependent variations in the observed spectra, caused by molecular absorption and emission in the planets' atmospheres. This will enable detailed studies of atmospheric composition, clouds, hazes, and thermal structure. To achieve its science objectives, the Ariel consortium must ensure that the noise budget is resilient to different sources of systematics, from the detector, the instrument, or the science scene itself.

The systematics expected are the jitter of the Line of Sight of the telescope (LoS), the pixels’ response non-linearity (PRNL) and bad pixels on the focal plane. PRNL can be explained as capacitive leakage on the readout electronics of each pixel during the integration time. Bad pixels, identified by their non-nominal behavior, are masked from the detector array. Reaction wheels, meant to ensure the stability of the spacecraft, can eventually reach some resonance frequencies, producing a jitter of the LoS of the telescope. The point spread function on the focal plane is shifted and distorted from frame to frame by this jitter effect. Since the pixel response function varies across and within individual pixels (intra-pixel variations), jitter induces photometric noise. This noise level needs to remain under the threshold of 5% above the photon noise as specified by Ariel design requirements. A jitter detrending method has been designed for this purpose (Bocchieri et al, 2025). We found all these effects to be detrendable. For instance, the attached figure is the Allan deviation plot at a one-hour timescale, an indicator of the noise level at the timescale of a planet transit in front of its host star, as a function of the wavelength. The red curves are the noise level without jitter correction, for three different levels of jitter amplitude. The blue curves are the levels of noise after performing jitter correction. Finally, the green curve is the noise level of the Ariel requirement, i.e., 5% above the level of the photon noise, computed with a reference observation containing no jitter at all. These curves are the averaged Allan deviation results obtained from 50 different random noise realizations (photon noise and readout noise); all the other parameters being left unchanged. After jitter correction, the blue curves meet Ariel’s requirement.

In this contribution, the work will be presented as a part of the Ariel Simulators Software, Management and Documentation (S2MD) Working Group, on studying the combined effect of the jitter of the LoS of the telescope, the PRNL, and the presence of permanent bad pixels on the focal plane of the telescope. This work is based on the use of the ExoSim2.0 simulator (Mugnai et al, 2025) to produce simulated Ariel observations, including a chosen set of systematic effects. I used jitter timelines produced by Airbus Defence and Space (ADS), PRNL maps from the JWST NIRSpec detector as representative of the Ariel focal planes, and random maps of permanently masked bad pixels. This work focuses on the Ariel spectrometer AIRS (AIRS-CH0 and AIRS-CH1).  The simulated image time series are processed to correct for the injected systematics, using calibration data with well-defined uncertainty levels, or no calibration data at all, to quantify how sensitive the extracted planet spectrum is to jitter, bad pixels, and PRNL. The models used to correct the previous set of systematics using Bayesian inference will be presented. The results come from three different targets (HD189733, HD209458, and GJ1214), a very bright, bright, and faint target, to capture possible different regimes in the jitter effect, as the exposure time is not the same. This work confirms the resilience of the Ariel instrument design against the set of systematics investigated here. It provides a definition of detrending algorithms that can be considered for implementation in the Ariel data reduction pipeline.

References:

• Giovanna Tinetti et al. “Ariel: Enabling planetary science across light-years”. In: arXiv e-prints,arXiv:2104.04824 (Apr. 2021), arXiv:2104.04824. arXiv: 2104.04824
• Mugnai, L.V., Bocchieri, A., Pascale, E., Lorenzani, A., & Papageorgiou, A. (2025). ExoSim 2: the new exoplanet observation simulator applied to the Ariel space mission. Experimental Astronomy.
• Bocchieri, Andrea, Lorenzo V. Mugnai, Enzo Pascale, Andreas Papageorgiou, Angele Syty, Angelos Tsiaras, Paul Eccleston, Giorgio Savini, Giovanna Tinetti, Renaud Broquet, Patrick Chapman and Gianfranco Sechi. “De-jittering Ariel: an optimized algorithm.” (2025).

Acknowledgments: This work has received support from France 2030 through the project named Académie Spatiale d'Île-de-France (https://academiespatiale.fr/) managed by the National Research Agency under bearing the reference ANR-23-CMAS-0041, and from the Centre National d’Études Spatiales (CNES).

How to cite: Syty, A., Beaulieu, J.-P., Bocchieri, A., Drossart, P., Mugnai, L., and Pascale, E.: Assessing the impact of instrumental systematics on Ariel spectrometer performance using simulated observations, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-742, https://doi.org/10.5194/epsc-dps2025-742, 2025.

Motivation

The main science goal of PLATO (PLAnetary Transits and Oscillations of stars) is to detect and characterize extrasolar planets, including terrestrial planets in the habitable zone (HZ) of their host stars. Detecting rocky planets in the HZ requires high photometric stability, which depends on the telescope’s pointing performance. PLATO’s pointing performance is managed by the Fine Guidance System (FGS), which utilizes a catalog of guide stars (fgPIC) to determine the spacecraft’s attitude. The FGS compares the position of these guide stars within the telescope’s CCDs to their position in the sky to determine the spacecraft’s orientation. This is critical, as PLATO’s science mission requires an extremely high level of pointing accuracy. High amounts of variable activity in these guide stars can cause apparent shifts in their centroids in presence of background stellar contaminants. If this happens during science operations, the apparent movement in the guide stars’ centroids will cause the spacecraft to move in an attempt to maintain pointing direction. This movement creates systematic bias in any measurements taken by the spacecraft. The goal of this project is to quantify what, if any, effect astrophysical variability in guide stars will have on PLATO’s pointing stability.

Sample

Two preliminary viewing fields for PLATO’s Long-duration Observation Phase (LOP) have been identified: LOPN1 in the Northern hemisphere and LOPS2 in the Southern hemisphere. For this project, focus was placed on the LOPS2 field, although it is fairly simple to adapt this approach for an arbitrary field.

Figure 1: LOPS2  (sourced from PLATO SWT)

A cone search was performed for all G<9 stars in Gaia DR3 within LOPS2, yielding 14681 total stars. Cuts were then placed in the resulting catalog to select those stars that fit the predetermined fgPIC requirements. A final cut was utilized to select those stars that will be seen by PLATO’s CCDs during its initial observations, yielding 1503 total stars. From this, a randomly drawn sample of 30 stars was chosen for testing.  For the stars in this sample, light curves were obtained from TESS full frame images using the Eleanor python library (Feinstein et al. 2019). For each star in our sample, contaminants within 1 arcminute were obtained from Gaia Data Release 3 and the Stellar Pollution Ratio (SPR) was calculated. For a star with  contaminants, SPR is defined as

where F_* is the flux of the target star and F_i is the flux of the i-th contaminant.

Variability Analysis

To quantify stellar variability, we utilized an estimator known as FliPer (Flicker in the Power Domain) (Bastien et al. 2018). FliPer is defined as the averaged power spectral density (PSD) from some arbitrary initial frequency to the Nyquist frequency, corrected for photon noise. Photon noise for our TESS photometry was calculated using an empirical relation found by Kunimoto et al 2022.

FliPer serves as a robust measure of stellar variability as it has shown a strong correlation with fundamental stellar properties, particularly surface gravity.

Figure 2: FliPer vs. log(g) for stars in TESS Sector 33

Simulation

Simulated PLATO imagettes were created using the PlatoSim python library. Each round of simulations was performed with all sources of instrumental noise turned off and a constant background to minimize systematic effects. Three rounds of simulations were performed on each star in the sample. In the first round, the stars were constant. In the second round, the TESS photometry was introduced. Finally in the third, constant contaminants were added. 200 exposures per star were simulated for the first round, and 40320 exposures were simulated for the next two, as this number was close to the upper limit before memory issues were encountered.

Pointing Stability

Centroid coordinates for each simulated exposure are obtained through a PSF fitting algorithm. In this algorithm, an observation h(i, j) of a given pixel is modelled as a Gaussian PSF

with centroid position (u_c, v_c), PSF width σ, intensity I, background D, and random noise ξ.  The centroid is then determined by minimizing the distance function

for each pixel y(i, j) and unknowns α = (u_c, v_c, σ, I, D). (Grießbach et al. 2021). Since the FGS relies on measuring the guide stars’ centroids for attitude determination, we choose the transverse T of the centroid coordinates x and y 

in the boresight reference frame as an estimator of pointing stability.

Results

For each simulated dataset, the Spearman correlation coefficient  between the centroid noise and the base-10 logarithm of the FliPer was calculated. For the constant light curves, no significant correlation  was found, as expected. Low correlation was found for the variable cases without contaminants and with contaminants. However, correlation increases significantly for the case with contaminants when only considering stars with SPR >0.002.

Figure 3: FliPer vs. noise for sample with constant light curves.

Figure 4: FliPer vs. noise for sample without contaminants

Figure 5: FliPer vs. noise for sample including contaminants

How to cite: Bowling, S., Cabrera, J., Rauer, H., Heller, R., Lieu, R., Grießbach, D., Paproth, C., and Jiang, C.: The Effect of Guide Star Variability on PLATO Pointing Stability, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1665, https://doi.org/10.5194/epsc-dps2025-1665, 2025.