Optical and thermal infrared observations of six near-Earth asteroids in 2002

We present thermal infrared photometry and spectrophotometry of six Near-Earth Asteroids (NEAs) using the 3.8 m United Kingdom Infrared Telescope (UKIRT) together with quasi-simultaneous optical observations of five NEAs taken at the 1.0 m Jacobus Kapteyn Telescope (JKT). For Asteroid (6455) 1992 HE we derive a rotational period P = 2.736 ± 0.002   h , and an absolute visual magnitude H = 14.32 ± 0.24 . For Asteroid 2002 HK12 we derive H = 18.22 ( + 0.37 , − 0.30 ) . The Standard Thermal Model (STM), the Fast Rotating Model (FRM) and the Near-Earth Asteroid Thermal Model (NEATM) have been fitted to the measured fluxes to derive albedos and effective diameters. The derived geometric albedos and effective diameters are (6455) 1992 HE: p v = 0.26 ± 0.08 , D eff = 3.55 ± 0.5   km ; 1999 HF1: p v = 0.18 ± 0.07 , D eff = 3.73 ( + 1.0 , − 0.5 )   km ; 2000 ED104: p v = 0.18 ± 0.05 , D eff = 1.21 ± 0.2   km ; 2002 HK12: p v = 0.24 ( + 0.25 , − 0.11 ) , D eff = 0.62 ± 0.2   km ; 2002 NX18: p v = 0.031 ± 0.009 , D eff = 2.24 ± 0.3   km ; 2002 QE15: p v = 0.15 ( + 0.08 , − 0.06 ) , D eff = 1.94 ± 0.4   km . The limitations of using the NEATM to observe NEAs at high phase angles are discussed.