Narrowband Photometry of Comet P/Halley: Variation with Heliocentric Distance, Season, and Solar Phase Angle

Icarus ◽  
1998 ◽  
Vol 132 (2) ◽  
pp. 397-417 ◽  
Author(s):  
David G. Schleicher ◽  
Robert L. Millis ◽  
Peter V. Birch
Keyword(s):  
Phase Angle ◽  
Heliocentric Distance ◽  
Solar Phase

First High Solar Phase Angle Observations of Rhea Using Cassini VIMS: Upper Limits on Water Vapor and Geologic Activity

2008 ◽  
Vol 680 (1) ◽  
pp. L65-L68 ◽  
Author(s):  
K. M. Pitman ◽  
B. J. Buratti ◽  
J. A. Mosher ◽  
J. M. Bauer ◽  
T. W. Momary ◽  
...  
Keyword(s):  
Water Vapor ◽  
Phase Angle ◽  
Upper Limits ◽  
Solar Phase ◽  
Geologic Activity

scholarly journals High polarization degree of the continuum of comet 2P/Encke based on spectropolarimetric signals during its 2017 apparition

2018 ◽  
Vol 620 ◽  
pp. A161
Author(s):  
Y. G. Kwon ◽  
M. Ishiguro ◽  
Y. Shinnaka ◽  
T. Nakaoka ◽  
D. Kuroda ◽  
...  
Keyword(s):  
Phase Angle ◽  
Near Infrared ◽  
Scattered Light ◽  
Infrared Camera ◽  
Polarization Vector ◽  
Dust Particles ◽  
Polarization Degree ◽  
High Polarization ◽  
Solar Phase ◽  
The Continuum

Context. Spectropolarimetry is a powerful technique for investigating the physical properties of gas and solid materials in cometary comae without mutual contamination, but only a few spectropolarimetric studies have been conducted to extract each component. Aims. We attempt to derive the continuum (i.e., scattered light from dust coma) polarization degree of comet 2P/Encke, free of the influence of molecular emissions. The target is unique in that its orbit is dynamically decoupled from Jupiter, like the main-belt asteroids, but it ejects gas and dust like ordinary comets. Methods. We observed the comet using the Hiroshima Optical and Near-Infrared Camera attached to the Cassegrain focus of the 150 cm Kanata telescope on UT 2017 February 21 when the comet was at the solar phase angle of α = 75°.7. Results. We find that the continuum polarization degree with respect to the scattering plane is Pcont, r = 33.8 ± 2.7% at the effective wavelength of 0.82 μm, which is significantly higher than those of cometary dust in a high-Pmax group at similar phase angles. Assuming that an ensemble polarimetric response of the dust of 2P/Encke as a function of phase angle is morphologically similar with those of other comets, its maximum polarization degree is estimated to Pmax ≳ 40% at αmax ≈ 100°. In addition, we obtain the polarization degrees of the C2 swan bands (0.51–0.56 μm), the NH2 α bands (0.62–0.69 μm), and the CN-red system (0.78–0.94 μm) in a range of 3–19%, which depend on the molecular species and rotational quantum numbers of each branch. The polarization vector is aligned nearly perpendicularly to the scattering plane with an average of 0°.4 over a wavelength range of 0.50–0.97 μm. Conclusions. From the observational evidence, we conjecture that the high polarization degree of 2P/Encke might be attributable to a dominance of large dust particles around the nucleus, which have remained after frequent perihelion passages near the Sun.

scholarly journals VIRTIS-H observations of the dust coma of comet 67P/Churyumov-Gerasimenko: spectral properties and color temperature variability with phase and elevation

2019 ◽  
Vol 630 ◽  
pp. A22 ◽  
Author(s):  
D. Bockelée-Morvan ◽  
C. Leyrat ◽  
S. Erard ◽  
F. Andrieu ◽  
F. Capaccioni ◽  
...  
Keyword(s):  
Phase Angle ◽  
Thermal Inertia ◽  
Color Temperature ◽  
Dust Particles ◽  
Infrared Thermal Imaging ◽  
Imaging Spectrometer ◽  
Fixed Phase ◽  
Dust Coma ◽  
Solar Phase ◽  
Comet 67P

We analyze 2–5 μm spectroscopic observations of the dust coma of comet 67P/Churyumov-Gerasimenko obtained with the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-H) instrument on board Rosetta from 3 June to 29 October 2015 at heliocentric distances rh = 1.24–1.55 AU. The 2–2.5 μm color, bolometric albedo, and color temperature were measured using spectral fitting. Data obtained at α = 90° solar phase angle show an increase in bolometric albedo (0.05–0.14) with increasing altitude (0.5–8 km), accompanied by a possible marginal decrease in color and color temperature. Possible explanations include dark particles on ballistic trajectories in the inner coma and radial changes in particle composition. In the phase angle range 50°–120°, phase reddening is significant (0.031%/100 nm deg−1) for a mean color of 2%/100 nm at α = 90°, which might be related to the roughness of the dust particles. Moreover, a decrease in color temperature with decreasing phase angle is also observed at a rate of ~0.3 K deg−1, consistent with the presence of large porous particles, with low thermal inertia, and showing a significant day-to-night temperature contrast. Comparing data acquired at fixed phase angle (α = 90°), a 20% increase in bolometric albedo is observed near perihelion. Heliocentric variations in dust color are not significant in the time period we analyzed. The measured color temperatures vary from 260 to 320 K, and follow a rh−0.6 variation in the rh = 1.24–1.5 AU range, which is close to the expected rh−0.5 value.

scholarly journals Phase-angle dependence of colour ratios and potential implications for lunar remote sensing

2020 ◽  
Vol 644 ◽  
pp. A30
Author(s):  
Yazhou Yang ◽  
Pei Ma ◽  
Le Qiao ◽  
Hao Zhang ◽  
Weidong Jin ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Particle Size ◽  
Phase Angle ◽  
Remote Sensing Data ◽  
Target Surface ◽  
Phase Dependence ◽  
Imaging Device ◽  
Angle Dependence ◽  
Solar Phase ◽  
Phase Angles

Context. The colour-ratio technique has been widely used in mapping planetary surfaces, but its solar phase-angle dependence is not well understood. Understanding the phase-angle dependence of the colour ratio would enhance our abilities in interpreting planetary remote sensing data. Aims. We aim to investigate the dependence of the colour ratio indices on mineralogy, phase angle, particle size, and the degree of simulated space weathering. Methods. We measured the multi-band (i.e. 458, 633, 750, and 905 nm) and multi-angle reflectance spectra of four typical lunar-type minerals with different particle sizes using a custom multi-angular imaging device. Results. The colour ratio does have a phase-angle dependence that is more sensitive to the mineralogy and wavelength and less sensitive to particle size distribution. Conclusions. The combined analysis of the colour ratio and its phase dependence can improve efficiency in mapping the lunar surface. With a prior knowledge of the phase behaviours of colour ratios of specific lunar-type minerals, an optimised colour ratio at certain phase angles can be found to efficiently distinguish the composition of a target surface.

Study of body composition and phase angle in relation to nutritional parameters in patients with neuroendocrine tumors

2019 ◽  
Author(s):  
Carmen Hernandez-Garcia ◽  
Isabel Maria Cornejo-Pareja ◽  
Miguel Damas-Fuentes ◽  
Jose Ignacio Martinez-Montoro ◽  
Cristina Maria Diaz-Perdigones ◽  
...  
Keyword(s):  
Body Composition ◽  
Phase Angle ◽  
Neuroendocrine Tumors ◽  
Nutritional Parameters

Descriptive analysis of body composition and phase angle (PA) in achondroplastic patients: Case-control study

2020 ◽  
Author(s):  
Vegas-Aguilar Isabel Mª ◽  
Cornejo Pareja Isabel Maria ◽  
Gea Antonio Leiva ◽  
Francisco J Tinahones ◽  
García-Almeida Jose Manuel
Keyword(s):  
Body Composition ◽  
Phase Angle ◽  
Case Control Study ◽  
Descriptive Analysis ◽  
Case Control ◽  
Control Study
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