scholarly journals Angular differential kernel phases

2020 ◽  
Vol 636 ◽  
pp. A21
Author(s):  
Romain Laugier ◽  
Frantz Martinache ◽  
Nick Cvetojevic ◽  
David Mary ◽  
Alban Ceau ◽  
...  
Keyword(s):  
Binary Star ◽  
Contrast Imaging ◽  
Point Spread ◽  
High Contrast Imaging ◽  
Calibration Methods ◽  
Spread Function ◽  
Common Technique ◽  
The Stability ◽  
Differential Imaging ◽  
Flux Leakage

Context. To reach its optimal performance, Fizeau interferometry requires that we work to resolve instrumental biases through calibration. One common technique used in high contrast imaging is angular differential imaging, which calibrates the point spread function and flux leakage using a rotation in the focal plane. Aims. Our aim is to experimentally demonstrate and validate the efficacy of an angular differential kernel-phase approach, a new method for self-calibrating interferometric observables that operates similarly to angular differential imaging, while retaining their statistical properties. Methods. We used linear algebra to construct new observables that evolve outside of the subspace spanned by static biases. On-sky observations of a binary star with the SCExAO instrument at the Subaru telescope were used to demonstrate the practicality of this technique. We used a classical approach on the same data to compare the effectiveness of this method. Results. The proposed method shows smaller and more Gaussian residuals compared to classical calibration methods, while retaining compatibility with the statistical tools available. We also provide a measurement of the stability of the SCExAO instrument that is relevant to the application of the technique. Conclusions. Angular differential kernel phases provide a reliable method for calibrating biased observables. Although the sensitivity at small separations is reduced for small field rotations, the calibration is effectively improved and the number of subjective choices is reduced.

scholarly journals A New Algorithm for Point‐Spread Function Subtraction in High‐Contrast Imaging: A Demonstration with Angular Differential Imaging

2007 ◽  
Vol 660 (1) ◽  
pp. 770-780 ◽  
Author(s):  
David Lafreniere ◽  
Christian Marois ◽  
Rene Doyon ◽  
Daniel Nadeau ◽  
Etienne Artigau
Keyword(s):  
Point Spread Function ◽  
High Contrast ◽  
Contrast Imaging ◽  
Point Spread ◽  
High Contrast Imaging ◽  
Spread Function ◽  
Differential Imaging

scholarly journals The In-orbit Performance of SEVIRI From Observations of Mercury and Venus

2021 ◽  
Author(s):  
Martin Burgdorf ◽  
Stefan Buehler ◽  
Viju John ◽  
Thomas Müller
Keyword(s):  
Finite Impulse Response ◽  
Field Of View ◽  
Promising Alternative ◽  
Narrow Channels ◽  
Vicarious Calibration ◽  
The North ◽  
Point Spread ◽  
Spread Function ◽  
The Stability ◽  
Calibration Coefficients

<p>We investigated various aspects of the in-orbit performance of SEVIRI on Meteosat-10 (launch: 05 Jul 2012) and -11 (launch: 15 Jul 2015) with images, where Mercury or Venus appeared in a corner. These objects are of similar or smaller size than the instantaneous field of view, and therefore they are well suited for checks of geometric requirements. From comparing the position of Venus in different channels we conclude that the North-South distance between the two focal planes is shorter than the nominal value by 0.66 km at SSP (Sub-Satellite Point) with Meteosat-10 and longer by 1.44 km at SSP with Meteosat-11. The tilt of the detector array against the equator is less than 0.0037° for SEVIRI on Metosat-10. The sampling with narrow channels is 3.0016 km, with a one-sigma uncertainty of 30 cm at sub-satellite point. The tests we carried out to check the geometric performance of the instrument confirmed that SEVIRI is compliant with the requirements. The Point Spread Function as determined from the image of a planet agrees well with the expectations based on its combination with the finite impulse response. Finally we determined the stability of the calibration coefficients from the counts obtained on the planetary targets and found the reproducibility of the measurements of planetary fluxes similar to those of vicarious calibration targets. Hence planets are a promising alternative to established methods of in-flight characterisation and validation of imagers.</p>

scholarly journals Medium-resolution integral-field spectroscopy for high-contrast exoplanet imaging

2018 ◽  
Vol 617 ◽  
pp. A144 ◽  
Author(s):  
H. J. Hoeijmakers ◽  
H. Schwarz ◽  
I. A. G. Snellen ◽  
R. J. de Kok ◽  
M. Bonnefoy ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Cross Correlation ◽  
High Contrast ◽  
Contrast Imaging ◽  
Data Set ◽  
Stellar Spectrum ◽  
High Contrast Imaging ◽  
Medium Resolution ◽  
Differential Imaging ◽  
Integral Field

Context. Angular differential imaging (ADI) and spectral differential imaging (SDI) are well-established high-contrast imaging techniques, but their application is challenging for companions at small angular separations from their host stars. Aims. The aim of this paper is to investigate to what extent adaptive-optics assisted, medium-resolution (R ~ 5000) integral field spectrographs (IFS) can be used to directly detect the absorption of molecular species in the spectra of planets and substellar companions when these are not present in the spectrum of the star. Methods. We analysed archival data of the β Pictoris system taken with the SINFONI integral field spectrograph located at ESO’s Very Large Telescope, originally taken to image β Pictoris b using ADI techniques. At each spatial position in the field, a scaled instance of the stellar spectrum is subtracted from the data after which the residuals are cross-correlated with model spectra. The cross-correlation co-adds the individual absorption lines of the planet emission spectrum constructively, while this is not the case for (residual) telluric and stellar features. Results. Cross-correlation with CO and H2O models results in significant detections of β Pictoris b with signal-to-noise ratios (S/Ns) of 13.7 and 16.4 respectively. Correlation with a T = 1700 K BT-Settl model provides a detection with an S/N of 22.8. This in contrast to application of ADI, which barely reveals the planet. While the adaptive optics system only achieved modest Strehl ratios of 19–27% leading to a raw contrast of 1:240 at the planet position, cross-correlation achieves a 3σ contrast limit of 2.7 × 10−5 in this 2.5 hr data set, a factor ~40 below the raw noise level at an angular distance of 0.36′′ from the star. Conclusions. Adaptive-optics assisted, medium-resolution IFS, such as SINFONI on the VLT and OSIRIS on the Keck Telescope, can be used for high-contrast imaging utilizing cross-correlation techniques for planets that are close to their star and embedded in speckle noise. We refer to this method as molecule mapping, and advocate its application to observations with future medium resolution instruments, in particular ERIS on the VLT, HARMONI on the ELT and NIRSpec, and MIRI on the JWST.

scholarly journals A Multiwavelength Differential Imaging Experiment for the High Contrast Imaging Testbed

2009 ◽  
Vol 121 (881) ◽  
pp. 716-727 ◽  
Author(s):  
Beth Biller ◽  
John Trauger ◽  
Dwight Moody ◽  
Laird Close ◽  
Andreas Kuhnert ◽  
...  
Keyword(s):  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Imaging Experiment ◽  
Differential Imaging

scholarly journals Search for cool extrasolar giant planets combining coronagraphy, spectral and angular differential imaging

2013 ◽  
Vol 8 (S299) ◽  
pp. 21-25
Author(s):  
Anne-Lise Maire ◽  
Anthony Boccaletti ◽  
Julien Rameau ◽  
Gaël Chauvin ◽  
Anne-Marie Lagrange ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Point Sources ◽  
Giant Planets ◽  
Phase Mask ◽  
Evolutionary Models ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Nearby Stars ◽  
Differential Imaging

AbstractSpectral differential imaging (SDI) is part of the observing strategy of current and on-going high-contrast imaging instruments on ground-based telescopes. Although it improves the star light rejection, SDI attenuates the signature of off-axis companions to the star, just like angular differential imaging (ADI). However, the attenuation due to SDI has the peculiarity of being dependent on the spectral properties of the companions. To date, no study has investigated these effects. Our team is addressing this problem based on data from a direct imaging survey of 16 stars combining the phase-mask coronagraph, the SDI and the ADI modes of VLT/NaCo. The objective of the survey is to search for cool (Teff<1000-1300 K) giant planets at separations of 5-10 AU orbiting young, nearby stars (<200 Myr, <25 pc). The data analysis did not yield any detections. As for the estimation of the sensivity limits of SDI-processed images, we show that it requires a different analysis than that used in ADI-based surveys. Based on a method using the flux predictions of evolutionary models and avoiding the estimation of contrast, we determine directly the mass sensivity limits of the survey for the ADI processing alone and with the combination of SDI and ADI. We show that SDI does not systematically improve the sensitivity due to the spectral properties and self-subtraction of point sources.

scholarly journals GRAPHIC: The Geneva Reduction and Analysis Pipeline for High-contrast Imaging of planetary Companions

2013 ◽  
Vol 8 (S299) ◽  
pp. 38-39
Author(s):  
Janis Hagelberg ◽  
Damien Ségransan ◽  
Stéphane Udry ◽  
François Wildi
Keyword(s):  
Radial Velocity ◽  
Fourier Transforms ◽  
Signal Loss ◽  
Contrast Imaging ◽  
Analysis Pipeline ◽  
Computer Clusters ◽  
High Contrast Imaging ◽  
Image Shifting ◽  
Differential Imaging ◽  
Disk Mode

AbstractWe present a new analysis and reduction pipeline for the detection of planetary companions using Angular Differential Imaging. The pipeline uses Fourier transforms for image shifting and rotation in order to achieve very low signal loss. Furthermore it is parallelised in order to run on computer clusters of up to 1024 cores. The pipeline was developed in Geneva for the ongoing direct imaging campaign for stars with radial velocity drifts in the HARPS and CORALIE radial-velocity planet-search surveys. In addition to that, a disk mode has been implemented in the context of observations of the protoplanetary disk around HD142527.

scholarly journals Angular Differential Imaging: A Powerful High‐Contrast Imaging Technique

2006 ◽  
Vol 641 (1) ◽  
pp. 556-564 ◽  
Author(s):  
Christian Marois ◽  
David Lafreniere ◽  
Rene Doyon ◽  
Bruce Macintosh ◽  
Daniel Nadeau
Keyword(s):  
Imaging Technique ◽  
High Contrast ◽  
Contrast Imaging ◽  
High Contrast Imaging ◽  
Differential Imaging
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