106 research outputs found
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
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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
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
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