Physical properties of accessible Near Earth Objects, including the primitive (68278) 2001 FC7

We used the Spitzer Space Telescope to carry out infrared spectroscopy (between 5.2 and 38 μ m ) of nine Near Earth Objects: (2063) Bacchus, (6239) Minos, (11284) Belenus, (17511) 1992 QN, (18109) 2000 NG11, (67367) 2000 LY27, (68278) 2001 FC7, (68359) 2001 OZ13 and (136618) 1994 CN2. These objects were selected because they are among the most accessible for a space mission in terms of Δ V . Our aim was to determine their size and albedo, and to constrain their surface composition. The data were processed using the Spitzer pipeline. We modelled the asteroids’ spectral energy distribution using the Near Earth Asteroid Thermal Model to determine their sizes and albedos. We complemented emissivity spectra with visible and near-infrared (VNIR) spectroscopic data from the literature to infer taxonomic classes and meteorite analogs. Photometric observations of eight NEOs, including four Spitzer targets plus (3361) Orpheus, (7088) Ishtar, (8035) 1992 TB, and (54071) 20000 GQ146, were also carried out at the New Technology Telescope to determine their absolute magnitude and visible colors. The selected targets have diameters ranging from 0.5 to 1.6 km. Five of the objects in our sample are S-complex or Q-type near-Earth objects (Bacchus, Minos, Belenus, 2001 OZ13 and 1994 CN2), with albedos ranging from 20% to 39%. Their VNIR and emissivity spectra indicate similarities with ordinary chondrites, suggesting silicaceous-rich composition. Three other targets belong to the X-complex (1992 QN, 2000 NG11 and possibly 2000 LY27), with albedos ranging from 15% to 33% for 1992 QN, which is likely to be an Xe-type object. 2001 FC7 is the largest NEO in the sample studied here (diameter = 1.6 km), the darkest (albedo 3.2 ± 0.03%), the most accessible ( Δ V =5.05 km s −1 ) for a space mission, and its emissivity and VNIR spectrum is best matched by carbonaceous chondrites, indicating a very primordial surface composition. • Precise size and albedo estimation of 9 Near Earth Objects from Spitzer observations. • First emissivity measurements of five silicate-rich NEOs analogs to ordinary chondrites. • The primitive NEO (68278) 2001 FC7 is extremely dark, analog to carbonaceous chondrites, and an easily accessible target for space missions. • Visible colors of eight NEOs from ESO-NTT telescope.