ANALYTICAL PARAMETERIZED MODELS IN COMPUTER VISION *

Object recognition is a key problem in machine vision. Model-based recognition depends on the ability to depict graphical information. This paper extends present methods of shape description of objects using especial equations with arbitrary number of internal parameters, representing transformation of coordinates, changeable dimension, color, texture, etc. We can also use model equations as a measure of distance between the model and points of object image. With the purpose of visualization we can draw colored, grayscale or binary pictures of 2-D and 3-D objects.

OMEGA : Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité

International audienc

OMEGA : Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité

International audienc

First observations of H2O and CO2vapor in comet 67P/Churyumov-Gerasimenko made by VIRTIS onboard Rosetta

Context. Outgassing from cometary nuclei involves complex surface and subsurface processes that need to be understood to investigate the composition of cometary ices from coma observations. Aims. We investigate the production of water, carbon dioxide, and carbon monoxide from the nucleus of comet 67P/Churyumov-Gerasimenko (67P). These species have different volatility and are key species of cometary ices. Methods. Using the high spectral-resolution channel of the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-H), we observed the ν3 vibrational bands of H2O and CO2 at 2.67 and 4.27 μm, respectively, from 24 November 2014 to 24 January 2015, when comet 67P was between 2.91 and 2.47 AU from the Sun. Observations were undertaken in limb-viewing geometry at distances from the surface of 0 to 1.5 km and with various line-of-sight (LOS) orientations in the body-fixed frame. A geometry tool was used to characterize the position of the LOS with respect to geomorphologic regions and the illumination properties of these regions. Results. The water production of 67P did not increase much from 2.9 to 2.5 AU. High water column densities are observed for LOS above the neck regions, suggesting they are the most productive in water vapor. While water production is weak in regions with low solar illumination, CO2 is outgassing from both illuminated and non-illuminated regions, which indicates that CO2 sublimates at a depth that is below the diurnal skin depth. The CO2/H2O column density ratio varies from 2 to 60%. For regions that are in sunlight, mean values between 2 and 7% are measured. The lower bound value is likely representative of the CO2/H2O production rate ratio from the neck regions. For carbon monoxide, we derive column density ratios CO/H2O < 1.9% and CO/CO2< 80%. An illumination-driven model, with a uniformly active surface releasing water at a mean rate of 8 × 1025 s-1, provides an overall agreement to VIRTIS-H data, although some mismatches show local surface inhomogeneities in water production. Rotational temperatures of 90–100 K are derived from H2O and CO2 averaged spectra

VIRTIS: The Visible and Infrared Thermal Imaging Spectrometer

The VIRTIS imaging spectrometer built for ESA's Rosetta cometary mission is a versatile instrument that is also well-suited to Venus observations. The discovery of the near-IR windows in the atmosphere of Venus from ground-based observations in the 1980s showed that the surface of the planet can be studied via IR observations over the nightside. Imaging spectroscopy in the visible and near-IR can study the atmosphere from the uppermost layers down to the deepest levels. With its unique combination of mapping capabilities at low spectral resolution (VIRTIS-M) and high spectral resolution slit spectroscopy (VIRTIS-H), the instrument is ideal for making extensive IR and visible spectral images of the planet

VIRTIS: The Visible and Infrared Thermal Imaging Spectrometer

The VIRTIS imaging spectrometer built for ESA's Rosetta cometary mission is a versatile instrument that is also well-suited to Venus observations. The discovery of the near-IR windows in the atmosphere of Venus from ground-based observations in the 1980s showed that the surface of the planet can be studied via IR observations over the nightside. Imaging spectroscopy in the visible and near-IR can study the atmosphere from the uppermost layers down to the deepest levels. With its unique combination of mapping capabilities at low spectral resolution (VIRTIS-M) and high spectral resolution slit spectroscopy (VIRTIS-H), the instrument is ideal for making extensive IR and visible spectral images of the planet