Photometric Calibration for Stereo Camera with Gamma-like Response Function in Direct Visual Odometry

Direct visual odometry algorithms assume that every frame from the camera has the same photometric characteristics. However, the cameras with auto exposure are widely used outdoors as the environment often changes. The vignetting also affects the pixel’s brightness on different frames, even if the exposure time is fixed. We propose an online vignetting correction and exposure time estimation method for stereo direct visual odometry algorithms. Our method works on a camera that has a gamma-like response function. The inverse vignetting function and exposure time ratio between neighboring frames are estimated. Stereo matching is used to select correspondences between the left image and right image in the same frame at the initialization step. Feature points are used to pick the correspondences between different frames. Our method provides static correction results during the experiments on datasets and a stereo camera.

Calibration and Validation of Infrared Sounders with Moon and Mercury

<p>Serendipitous observations of airless bodies of the inner solar system provide a unique means to the calibration of instruments on meteorological research satellites, because the physical properties of their surfaces change very little, even on large time scales. We investigated how certain instrumental effects can be characterised with observations of the Moon and Mercury. For this we identified and analysed intrusions of the Moon in the deep space views of HIRS/2, /3, and /4 (High-resolution Infrared Sounder) on various satellites in polar orbits and as well some images obtained with SEVIRI (Spinning Enhanced Visible Infra-Red Imager) on MSG-3 and -4 (Meteosat Second Generation), which had Mercury standing close to the Earth in the rectangular field of view.</p><p>A full-disk, infrared Moon model was developed that describes how the lunar flux density depends on phase angle and wavelength. It is particularly helpful for inter-calibration, checks of the photometric consistency of the sounding channels, and the calculation of an upper limit on the non-linearity of the shortwave channels of HIRS. In addition, we used the Moon to determine the co-registration of the different spectral channels.</p><p>Studies of the channel alignment are also presented for SEVIRI, an infrared sounder with an angular resolution about a hundred times better than HIRS. As we wanted to check the image quality of this instrument with a quasi-point source as well, we replaced here the Moon with Mercury. We found the typical smearing of the point spread function in the scan direction and occasionally a nearby ghost image, which is three to four times fainter than the main image of the planet. Both effects cause additional uncertainties of the photometric calibration.  </p>

BVRI photometric calibration of the Nedeljkovic telescope

We have done photometric calibration of the 60 cm Nedeljkovic telescope equipped with the FLI PL 230 CCD camera, mounted at the Astronomical Station Vidojevica (Serbia), using standard stars from the Landolt catalog. We have imaged 31 fields of standard stars using Johnson's BVRI filters during three nights in August 2019. We have measured both extinction and color correction. Relating our calibrated magnitudes to the magnitudes of standard stars from the Landolt catalog, we have achieved accuracy of 2%-5% for the BVRI magnitudes.

Photometric calibration of 28-cm telecsope of NCAS KFU by jointly modeling equations of transformations and the extinction

This work is devoted to study of transformations equations between Binstr, Ginstr, Rinstr photometric system of 28-cm Schmidt-Cassegrain telescope mounted in NCAS KFU to standard Johnson—Cousins BJ , VJ , RC using modern numerical methods. Observations of Landold Standards at the SA110 region were performed. Absolute photometry of selected stars was obtained with estimatiuon of observational errors. To transform the observational data into the standart system numerical model was built with the use of Markov Chain Monte Carlo sampling. So, we found average parameters of transformations between systems (color reduction coefficients are 0.165, −0.120, −0.378 for B0 J , V 0 J , R0C in dependence of (B − G)0 instr, (G − R)0 instr, (G − R)0 instr respectievely) and medium extinction at the observational period (0.276, 0.205, 0.159 for Binstr, Ginstr, Rinstr respectievely).

A synthetic Roman Space Telescope High-Latitude Imaging Survey: simulation suite and the impact of wavefront errors on weak gravitational lensing

ABSTRACT The Nancy Grace Roman Space Telescope (Roman) mission is expected to launch in the mid-2020s. Its weak lensing program is designed to enable unprecedented systematics control in photometric measurements, including shear recovery, point spread function (PSF) correction, and photometric calibration. This will enable exquisite weak lensing science and allow us to adjust to and reliably contribute to the cosmological landscape after the initial years of observations from other concurrent Stage IV dark energy experiments. This potential requires equally careful planning and requirements validation as the mission prepares to enter its construction phase. We present a suite of image simulations based on galsim that are used to construct a complex, synthetic Roman weak lensing survey that incorporates realistic input galaxies and stars, relevant detector non-idealities, and the current reference 5-yr Roman survey strategy. We present a first study to empirically validate the existing Roman weak lensing requirements flowdown using a suite of 12 matched image simulations, each representing a different perturbation to the wavefront or image motion model. These are chosen to induce a range of potential static and low- and high-frequency time-dependent PSF model errors. We analyse the measured shapes of galaxies from each of these simulations and compare them to a reference, fiducial simulation to infer the response of the shape measurement to each of these modes in the wavefront model. We then compare this to existing analytic flowdown requirements, and find general agreement between the empirically derived response and that predicted by the analytic model.