Speaker
Description
To assess the risk of an impact from a Near Earth Object (NEO), it is crucial to estimate both the size and density of the object. These estimations can be more easily inferred if the albedo of the object is known. In this context, polarization observations are a key tool for swiftly determining the size of a NEO, and consequently, their potential threat to Earth.
The degree of linear polarization is inversely proportional to the albedo of the scattering surface of an asteroid. This relation is better constrained at high phase angles at which NEOs are usually observed and where polarization is more significant. This translates into low albedo objects consistently exhibiting higher degree of polarization compared to high albedo objects.
Thus, polarimetry allows for direct albedo measurement without relying on additional data, such as the absolute magnitude. Also, polarimetry measurements are independent on the shape of the observed object, so we are not affected by the rotational phase at which the object is observed. Consequently, determining albedo through polarimetry serves as a crucial complementary and independent method to thermal modeling.
In this poster, we will present the design of Rapid-Defender, a polarimeter specifically designed to rapidly characterize NEOs to assess their hazard to Earth. This instrument features a double Wollaston prism, enabling simultaneous measurement of two orthogonal light intensities and yielding the degree of polarization in a single observation. This allows for the estimation of an object's albedo and size within minutes. Additionally, a half-wave plate located before the double Wollaston prism would allow to self-calibrate our observations by swapping the ordinary and extra-ordinary beam by rotating the plane of polarization of the incoming light before the Wollaston prism.
This new instrument would allow to reach V ~ 16 mag when located at 1 meter telescopes, leading to the observation of approximately 20 newly discovered NEOs per year.