NEOPOPS - Spectroscopy for planetary defense

The study of Near-Earth Objects (NEO) is of crucial importance for several reasons. From the science perspective, these objects are the keys to understand the origin and the evolution of the early Solar System, as well as their role in delivering organic materials and water to Earth (Morbidelli et al., 2000, Marty et al., 2016). From a planetary defense standpoint, NEOs pose a major threat, caused mass extinctions in the past – such as the K-Pg event 65 million years ago, which led to the extinction of dinosaurs following the impact of a ~10 km asteroid. More recently, the detection of 2024 YR4 - a NEO with an initial impact probability of 3% (later revised to less than 0.001 %, according to the CNEOS) – highlighted that threats can also originate from much smaller objects.

On one hand, because NEOs are close to Earth, they are more easily observed, allowing us to better understand the asteroid population of the entire Solar System. On the other hand, their small sizes (ranging from tens to hundreds meters in diameter) mean they become bright enough to observe only for very limited time spans, typically on the order of a few weeks. Moreover, small NEOs are the most likely to impact Earth and can cause regional or local-scale catastrophes (Perna et al., 2015). This necessitates rapid-response physical observations to keep pace with the increasing discovery rate of small NEOs.

In addition to other observational methods (e.g., photometry and polarimetry), the NEOPOPS project (for NEO Physical Observations and Properties Simulation) aims to conduct spectroscopic observations. These observations are coordinated by INAF, which is responsible for WP4 (spectroscopy) and WP6 (Rapid Response). Using the 3.5m NTT (La Silla Chile), the 3.58m TNG (La Palma, Spain), the 1.2m Galileo telescopio, and the 1.82m Copernico telescopio (both located in Asiago, Italy), our goal is to characterize the mineralogical surface composition and the taxonomy of observed objects.

These observations will be conducted in the visible to near-infrared range, enabling comparisons with available meteorite samples. Within this wavelength range, we can identify spectroscopic features - such as absorption bands – associated with specific minerals, some of which may have undergone aqueous alteration.

The compositional characterization, combined with meteorite comparisons, will help constrain the Yarkovsky effetcs (Farnocchia et al., 2013), which results from the radiative recoil due to anisotropic thermal emission. Prior to the approval of this project, we conducted spectroscopic observations on recently discovered NEOs in order to build a physical properties database and to test a rapid-response framework.

These spectroscopic observations will be integrated with additional datasets provided by collaborators, contributing to a continuously updated monthly database maintained by the European Space Agency (ESA). Furthermore, NEOPOPS operates as part of a coordinated effort with ESA.

In this presentation, we will focus on the spectroscopic observation component of the project. We will present examples of the methodology (spectra, parameters computation, estimation of the taxonomy, meteorite comparison), based on data obtained during a pilot program obtained by INAF at the TNG.

References: Morbidelli et al., M & PS, volume 35, (2000); Marty et al., EPSL, volume 441, (2016); Perna et al., PSS, volume 118, (2015); Farnocchia et al., Icarus, volume 224, (2013)