Photometric survey of 67 near-Earth objects

¹ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monte Porzio Catone, Rome, Italy
e-mail: simone.ieva@oa-roma.inaf.it
² LESIA – Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ, Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
³ IFAC – CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy
⁴ ESA SSA-NEO Coordination Centre„, Largo Galileo Galilei 1, 00044 Frascati (RM), Italy
⁵ Agenzia Spaziale Italiana, Via del Politecnico 1, 00100 Rome, Italy
⁶ Department of Physics and Astronomy “Galileo Galilei”, University of Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy

Received: 23 October 2017
Accepted: 29 March 2018

Abstract

Context. The near-Earth object (NEO) population is a window into the original conditions of the protosolar nebula, and has the potential to provide a key pathway for the delivery of water and organics to the early Earth. In addition to delivering the crucial ingredients for life, NEOs can pose a serious hazard to humanity since they can impact the Earth. To properly quantify the impact risk, physical properties of the NEO population need to be studied. Unfortunately, NEOs have a great variation in terms of mitigation-relevant quantities (size, albedo, composition, etc.) and less than 15% of them have been characterized to date.

Aims. There is an urgent need to undertake a comprehensive characterization of smaller NEOs (D < 300 m) given that there are many more of them than larger objects; their small sizes make them intrinsically fainter and therefore harder to study. One of the main aims of the NEOShield-2 project (2015–2017), financed by the European Community in the framework of the Horizon 2020 program, is therefore to retrieve physical properties of a wide number of NEOs in order to design impact mitigation missions and assess the consequences of an impact on Earth.

Methods. We carried out visible photometry of NEOs, making use of the DOLORES instrument at the Telescopio Nazionale Galileo (TNG, La Palma, Spain) in order to derive visible color indexes and the taxonomic classification for each target in our sample.

Results. We attributed for the first time the taxonomical complex of 67 objects obtained during the first year of the project. While the majority of our sample belong to the S-complex, carbonaceous C-complex NEOs deserve particular attention. These NEOs can be located in orbits that are challenging from a mitigation point of view, with high inclination and low minimum orbit intersection distance (MOID). In addition, the lack of carbonaceous material we see in the small NEO population might not be due to an observational bias alone.