Consumer cameras, particularly onboard smartphones and UAVs, are now commonly used as scientific instruments. However, their data processing pipelines are not optimized for quantitative radiometry ...and their calibration is more complex than that of scientific cameras. The lack of a standardized calibration methodology limits the interoperability between devices and, in the ever-changing market, ultimately the lifespan of projects using them. We present a standardized methodology and database (SPECTACLE) for spectral and radiometric calibrations of consumer cameras, including linearity, bias variations, read-out noise, dark current, ISO speed and gain, flat-field, and RGB spectral response. This includes golden standard ground-truth methods and do-it-yourself methods suitable for non-experts. Applying this methodology to seven popular cameras, we found high linearity in RAW but not JPEG data, inter-pixel gain variations >400% correlated with large-scale bias and read-out noise patterns, non-trivial ISO speed normalization functions, flat-field correction factors varying by up to 2.79 over the field of view, and both similarities and differences in spectral response. Moreover, these results differed wildly between camera models, highlighting the importance of standardization and a centralized database.
Many citizen science projects depend on colour vision. Examples include classification of soil or water types and biological monitoring. However, up to 1 in 11 participants are colour blind. We ...simulate the impact of various forms of colour blindness on measurements with the Forel-Ule scale, which is used to measure water colour by eye with a 21-colour scale. Colour blindness decreases the median discriminability between Forel-Ule colours by up to 33% and makes several colour pairs essentially indistinguishable. This reduces the precision and accuracy of citizen science data and the motivation of participants. These issues can be addressed by including uncertainty estimates in data entry forms and discussing colour blindness in training materials. These conclusions and recommendations apply to colour-based citizen science in general, including other classification and monitoring activities. Being inclusive of the colour blind increases both the social and scientific impact of citizen science.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Even though tens of directly imaged companions have been discovered in the past decades, the number of directly confirmed multiplanet systems is still small. Dynamical analysis of these ...systems imposes important constraints on formation mechanisms of these wide-orbit companions. As part of the Young Suns Exoplanet Survey we report the detection of a second planetary-mass companion around the 17 Myr-old, solar-type star TYC 8998-760-1 that is located in the Lower Centaurus Crux subgroup of the Scorpius–Centaurus association. The companion has a projected physical separation of 320 au and several individual photometric measurements from 1.1 to 3.8 microns constrain a companion mass of 6 ± 1
M
Jup
, which is equivalent to a mass ratio of
q
= 0.57 ± 0.10% with respect to the primary. With the previously detected 14 ± 3
M
Jup
companion that is orbiting the primary at 160 au, TYC 8998-760-1 is the first directly imaged multiplanet system that is detected around a young, solar analog. We show that circular orbits are stable, but that mildly eccentric orbits for either/both components (
e
> 0.1) are chaotic on gigayear timescales, implying in situ formation or a very specific ejection by an unseen third companion. Due to the wide separations of the companions TYC 8998-760-1 is an excellent system for spectroscopic and photometric follow-up with space-based observatories such as the James Webb Space Telescope.
We present an approach to spectropolarimetry that requires neither moving parts nor time dependent modulation, and that offers the prospect of achieving high sensitivity. The technique applies ...equally well, in principle, in the optical, UV, or IR. The concept, which is one of those generically known as channeled polarimetry, is to encode the polarization information at each wavelength along the spatial dimension of a two-dimensional data array using static, robust optical components. A single 2D data frame contains the full polarization information and can be configured to measure either two or all of the Stokes polarization parameters. By acquiring full polarimetric information in a single observation, we simplify polarimetry of transient sources and in situations where the instrument and target are in relative motion. The robustness and simplicity of the approach, coupled with its potential for high sensitivity, and applicability over a wide wavelength range, is likely to prove useful for applications in challenging environments such as space.
One of the main challenges for the direct imaging of planets around nearby stars is the suppression of the diffracted halo from the primary star. Coronagraphs are angular filters that suppress this ...diffracted halo. The Apodizing Phase Plate coronagraph modifies the pupil-plane phase with an anti-symmetric pattern to suppress diffraction over a 180 degree region from 2 to 7 λ/D and achieves a mean raw contrast of 10(-4) in this area, independent of the tip-tilt stability of the system. Current APP coronagraphs implemented using classical phase techniques are limited in bandwidth and suppression region geometry (i.e. only on one side of the star). In this paper, we introduce the vector-APP (vAPP) whose phase pattern is implemented through the vector phase imposed by the orientation of patterned liquid crystals. Beam-splitting according to circular polarization states produces two, complementary PSFs with dark holes on either side. We have developed a prototype vAPP that consists of a stack of three twisting liquid crystal layers to yield a bandwidth of 500 to 900 nm. We characterize the properties of this device using reconstructions of the pupil-plane pattern, and of the ensuing PSF structures. By imaging the pupil between crossed and parallel polarizers we reconstruct the fast axis pattern, transmission, and retardance of the vAPP, and use this as input for a PSF model. This model includes aberrations of the laboratory set-up, and matches the measured PSF, which shows a raw contrast of 10(-3.8) between 2 and 7 λ/D in a 135 degree wedge. The vAPP coronagraph is relatively easy to manufacture and can be implemented together with a broadband quarter-wave plate and Wollaston prism in a pupil wheel in high-contrast imaging instruments. The liquid crystal patterning technique permits the application of extreme phase patterns with deeper contrasts inside the dark holes, and the multilayer liquid crystal achromatization technique enables unprecedented spectral bandwidths for phase-manipulation coronagraphy.
Abstract
We use observations with the infrared-optimized Magellan Adaptive Optics (MagAO) system and Clio camera in 3.9
μ
m light to place stringent mass constraints on possible undetected companions ...to Sirius A. We suppress the light from Sirius A by imaging it through a grating vector-apodizing phase plate coronagraph with a 180° dark region (gvAPP-180). To remove residual starlight in postprocessing, we apply a time-domain principal-components-analysis-based algorithm we call PCA-Temporal, which uses eigen time series rather than eigenimages to subtract starlight. By casting the problem in terms of eigen time series, we reduce the computational cost of postprocessing the data, enabling the use of the fully sampled data set for improved contrast at small separations. We also discuss the impact of retaining fine temporal sampling of the data on final contrast limits. We achieve postprocessed contrast limits of 1.5 × 10
−6
–9.8 × 10
−6
outside of 0.″75, which correspond to planet masses of 2.6–8.0
M
J
. These are combined with values from the recent literature of high-contrast imaging observations of Sirius to synthesize an overall completeness fraction as a function of mass and separation. After synthesizing these recent studies and our results, the final completeness analysis rules out 99% of ≥9
M
J
planets from 2.5 to 7 au.
Aerosols in the atmospheres of cloudy gas giant exoplanets and brown dwarfs scatter and polarize these objects' thermal emission. If such an object has an oblate shape or nonuniform cloud ...distribution, the net degree of linear polarization can show an increase ranging from several tenths of a percent to a few percent. Modern high-contrast imaging polarimeters are now poised to detect such low-polarization signals, opening up a new window into the rotational velocities and cloud properties of substellar companions to nearby stars. In this paper, we present the results of a near-IR survey searching for linearly polarized thermal emission from a sample of two planetary-mass companions and five brown dwarf companions using GPI and SPHERE-IRDIS. We probe the subpercent linear polarization regime that typifies polarized free-floating brown dwarfs and place limits on each object's degree of linear polarization. We relate our upper limits on each target's degree of linear polarization to its rotation rate, and place our results in the context of rotation rates measured using high-resolution spectroscopy.
Isotope abundance ratios have an important role in astronomy and planetary sciences, providing insights into the origin and evolution of the Solar System, interstellar chemistry and stellar ...nucleosynthesis1,2. In contrast to deuterium/hydrogen ratios, carbon isotope ratios are found to be roughly constant (around 89) in the Solar System1,3, but do vary on galactic scales with a12C/13C isotopologue ratio of around 68 in the current local interstellar medium4-6. In molecular clouds and protoplanetary disks,12CO/13CO ratios can be altered by ice and gas partitioning7, low-temperature isotopic ion-exchange reactions8 and isotope-selective photodissociation9. Here we report observations of13CO in the atmosphere of the young, accreting super-Jupiter TYC 8998-760-1 b, at a statistical significance of more than six sigma. Marginalizing over the planet's atmospheric temperature structure, chemical composition and spectral calibration uncertainties suggests a12CO/13CO ratio of 31-10(90% confidence), a substantial enrichment in13C with respect to the terrestrial standard and the local interstellar value. As the current location of TYC 8998-760-1 b at greater than or equal to 160 astronomical units is far beyond the CO snowline, we postulate that it accreted a substantial fraction of its carbon from ices enriched in13C through fractionation.
Consumer cameras, especially on smartphones, are popular and effective instruments for above-water radiometry. The remote sensing reflectance
R
rs
is measured above the water surface and used to ...estimate inherent optical properties and constituent concentrations. Two smartphone apps, HydroColor and EyeOnWater, are used worldwide by professional and citizen scientists alike. However, consumer camera data have problems with accuracy and reproducibility between cameras, with systematic differences of up to 40% in intercomparisons. These problems stem from the need, until recently, to use JPEG data. Lossless data, in the RAW format, and calibrations of the spectral and radiometric response of consumer cameras can now be used to significantly improve the data quality. Here, we apply these methods to above-water radiometry. The resulting accuracy in
R
rs
is around 10% in the red, green, and blue (RGB) bands and 2% in the RGB band ratios, similar to professional instruments and up to 9 times better than existing smartphone-based methods. Data from different smartphones are reproducible to within measurement uncertainties, which are on the percent level. The primary sources of uncertainty are environmental factors and sensor noise. We conclude that using RAW data, smartphones and other consumer cameras are complementary to professional instruments in terms of data quality. We offer practical recommendations for using consumer cameras in professional and citizen science.
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