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 in 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 (FIRM) 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 QE(15): 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. (c) 2004 Elsevier Inc. All rights reserved.