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 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>

Improving position accuracy for telescopes with small aperture and wide field of view utilizing point spread function modelling

2020 ◽  
Vol 497 (3) ◽  
pp. 4000-4008
Author(s):  
Rongyu Sun ◽  
Shengxian Yu ◽  
Peng Jia ◽  
Changyin Zhao
Keyword(s):  
Point Spread Function ◽  
Large Scale ◽  
Field Of View ◽  
Wide Field ◽  
Position Measurement ◽  
Small Aperture ◽  
Position Accuracy ◽  
Point Spread ◽  
Wide Field Of View ◽  
Spread Function

ABSTRACT Telescopes with a small aperture and a wide field of view are widely used and play a significant role in large-scale state-of-the-art sky survey applications, such as transient detection and near-Earth object observations. However, owing to the specific defects caused by optical aberrations, the image quality and efficiency of source detection are affected. To achieve high-accuracy position measurements, an innovative technique is proposed. First, a large number of raw images are analysed using principal component analysis. Then, the effective point spread function is reconstructed, which reflects the state of the telescope and reveals the characteristics of the imaging process. Finally, based on the point spread function model, the centroids of star images are estimated iteratively. To test the efficiency and reliability of our algorithm, a large number of simulated images are produced, and a telescope with small aperture and wide field of view is utilized to acquire the raw images. The position measurement of sources is performed using our novel method and two other common methods on these data. Based on a comparison of the results, the improvement is investigated, and it is demonstrated that our proposed technique outperforms the others on position accuracy. We explore the limitations and potential gains that may be achieved by applying this technique to custom systems designed specifically for wide-field astronomical applications.

scholarly journals Expected performances of the Characterising Exoplanet Satellite (CHEOPS)

2020 ◽  
Vol 635 ◽  
pp. A24 ◽  
Author(s):  
S. Hoyer ◽  
P. Guterman ◽  
O. Demangeon ◽  
S. G. Sousa ◽  
M. Deleuil ◽  
...  
Keyword(s):  
Light Curves ◽  
Field Of View ◽  
Current Status ◽  
Point Spread ◽  
Single Target ◽  
Science Operations ◽  
Spread Function ◽  
And Performance ◽  
Irregular Point

The CHaracterizing ExOPlanet Satellite (CHEOPS) is set to be launched in December 2019 and will detect and characterize small size exoplanets via ultra high precision photometry during transits. CHEOPS is designed as a follow-up telescope and therefore it will monitor a single target at a time. The scientific users will retrieve science-ready light curves of the target that will be automatically generated by the CHEOPS data reduction pipeline of the Science Operations Centre. This paper describes how the pipeline processes the series of raw images and, in particular, how it handles the specificities of CHEOPS data, such as the rotating field of view, the extended irregular point spread function, and the data temporal gaps in the context of the strict photometric requirements of the mission. The current status and performance of the main processing stages of the pipeline, that is the calibration, correction, and photometry, are presented to allow the users to understand how the science-ready data have been derived. Finally, the general performance of the pipeline is illustrated via the processing of representative scientific cases generated by the mission simulator.

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.

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