Speaker
Description
Polarimetric observations of NEOs are important for a number of reasons:
• Determination of the geometric albedo and hence possible derivation of diameter
• Determination of some surface regolith properties
• For taxonomic classification purposes
• Because it is useful to identify special classes of objects having anomalous compositions
• Because it is useful to identify objects exhibiting cometary properties
• Because it can be useful for the physical characterization of newly discovered near-Earth objects • Because it provides data to constrain the theories of light scattering from asteroid surfaces
The above item list shows that polarimetry nicely complements the results coming from other observing techniques, in particular spectroscopy, and allows observers to infer important physical properties of NEOs.
The Calern Asteroid Polarimetric Survey (CAPS) is a project started in 2018 in collaboration with Observatory of Torino (Italy). It has provided in five years a major database of asteroid polarimetric data. The limited magnitude was V= 14 and the observations were essentially made in V band.
Since 2023 a new setup has been installed on a 1m in diameter telescope of Observatoire de la Cˆote d’Azur on Plateau de Calern. CAPS version 2.0 relies on a Finnish-UK-Italian-German-French collaboration and that allows us to equip the 1m Omicron telescope of the Calern observing station with DIPol-UF (Double Image Polarimeter-Ultra Fast), capable of high precision (10−5 % ) polarimetric observations simultaneously in three passbands (B,V,R).
The instrument utilizes electron-multiplied EM CCD cameras for high efficiency and fast image readout. The key features of DIPol-UF are: (i) optical design with high throughput and inherent stability; (ii) great versatility which makes the instrument optimally suitable for observations of bright and faint targets; (iii) control system which allows using the polarimeter remotely.
One full month over three of telescope time is dedicated to CAPS.
First observations allows to reach V=16 magnitude asteroid in 60s exposure time with a SNR of about several tens opening new perspectives for NEO polarimetric studies
