Current results of the PERSEE testbench: the cophasing control and the polychromatic null rate

Stabilizing a nulling interferometer at a nanometric level is the key issue to obtain deep null depths. The PERSEE breadboard has been designed to study and optimize the operation of a cophased nulling bench in the most realistic disturbing environment of a space mission. This presentation focuses on the current results of the PERSEE bench. In terms of metrology, we cophased at 0.33 nm rms for the piston and 80 mas rms for the tip/tilt (0.14% of the Airy disk). A Linear Quadratic Gaussian (LQG) control coupled with an unsupervised vibration identification allows us to maintain that level of correction, even with characteristic vibrations of nulling interferometry space missions. These performances, with an accurate design and alignment of the bench, currently lead to a polychromatic unpolarised null depth of 8.9E-6 stabilized at 3E-7 on the [1.65-2.45] \mum spectral band (37% bandwidth).Comment: 17 pages, 10 figures, proceedings of the Optics+Photonics SPIE conference, San Diego, 201

First stellar photons for an integrated optics discrete beam combiner at the William Herschel Telescope

We present the first on-sky results of a four-telescope integrated optics discrete beam combiner (DBC) tested at the 4.2mWilliamHerschel Telescope. The device consists of a four-input pupil remapper followed by a DBC and a 23-output reformatter. The whole device was written monolithically in a single alumino-borosilicate substrate using ultrafast laser inscription. The device was operated at astronomical H-band (1.6 μm), and a deformable mirror along with a microlens array was used to inject stellar photons into the device. We report the measured visibility amplitudes and closure phases obtained on Vega and Altair that are retrieved using the calibrated transfer matrix of the device. While the coherence function can be reconstructed, the on-sky results show significant dispersion from the expected values. Based on the analysis of comparable simulations, we find that such dispersion is largely caused by the limited signal-to-noise ratio of our observations. This constitutes a first step toward an improved validation of theDBCas a possible beam combination scheme for long-baseline interferometry. © 2021 Optical Society of America

Calibration of Flight Model CCDs for the Corot mission

International audienc

Calibration of Flight Model CCDs for the Corot mission

International audienc

SIAMOIS: Seismic Interferometer to Measure Oscillations in the Interior of Stars

International audienceSIAMOIS is a project devoted to ground-based asteroseismology, involving an instrument to be installed at the Dome C Concordia station in Antarctica. SIAMOIS provides an asteroseismic programme that can follow the way currently opened by the space project CoRoT, with unique information on G and K type bright stars on the main sequence. In addition, spectrometric observations with SIAMOIS will be able to detect oscillation modes that cannot be analyzed in photometry: the Doppler data, less affected by the stellar activity noise, yield a more precise mode structure inversion. The SIAMOIS concept is based on Fourier Transform interferometry. Such a principle leads to a small instrument designed and developed for the harsh conditions in Antarctic. The instrument will be fully automatic, with no moving parts, and a very simple initial set up in Antarctic. The dedicated scientific programme will avoid the complications related to a versatile instrument. Data reduction will be performed in real time, and the transfer of the asteroseismic data to Europe will require only a modest bandwidth. SIAMOIS will observe with a dedicated small 40-cm telescope. Dome C appears to be the ideal place for ground-based asteroseismic observations. The unequalled weather conditions yield a duty cycle as high as 90% over 3 months, as was observed during the 2005 wintering. This high duty cycle, a crucial point for asteroseismology, is comparable to the best space-based observations. Long time series (up to 3 months) will be possible, thanks to the long duration of the polar night. SIAMOIS can be seen as one of the very first observational projects in astronomy at Dome C. Its scientific programme will take full advantage of the unique quality of this site, and will constitute a necessary first step in preparation of future more ambitious programmes requiring more sophisticated instrumentation and larger collectors

Calibration strategy for the COROT photometry

International audienc

Calibration strategy for the COROT photometry

International audienc

Calibration strategy for the COROT photometry

International audienc

Calibration of flight model CCDs for CoRoT mission

International audienceCoRoT (Convection, Rotation and Transit) is a mission of high-accuracy photometry with two scientific programmes: asteroseismology and planet finding, using CCDs as detectors. Ten 2048×4096 CCDs manufactured by E2V (42-80) were calibrated on Meudon test bench in order to choose the best ones for flight. A very high instrument stability is needed. Taking into account the environmental perturbations (temperature, attitude control system jitter, radiations, etc.) we studied sensitivity of CCD gain and quantum efficiency to temperature and sensitivity of the output signal to bias voltages. Special attention was paid to pixel capacity and noise sources coming from dark current and pixel response non-uniformity. The calibration results together with the expected voltages and temperature fluctuations are compared with the specifications