Better optical and radar observations are needed to determine the asteroid's orbit, but the best measurements cannot be made until 2013.

Most optical observations take minutes to hours, so phenomena that change faster than this cannot readily be observed.

The ratings are based on 961 optical observations dating from February 16, 2002.

Ground-based radar and optical observations would have been used to track the vehicle's return.

It is an ideal location for submillimeter, infrared and optical observations.

This was supplemented by optical observations intended to build a lightcurve.

He proposed to change from radio to optical observations to receive useful data.

The orbiting Hubble telescope is designed for optical and ultraviolet observations.

Few other optical observations have been recorded with current instruments.

Too bad we can't make an optical observation, since normal light hasn't yet bridged the distance of 20 light-years.