An optical thickness of less than 0.1 indicates a clear sky with maximum visibility; a value of 1 or above indicates very hazy conditions.
光学厚度小于0.1意味着是能见度高的晴天；1或者以上则意味着烟雾天气。
2
The three are all optical satellites, which can capture images in daylight and in clear weather.
这三颗卫星均为光学卫星，它们可以在白天和良好天气下抓拍图像。
3
As one of the most important parts in optical components, reflect-mirror was the key technology in laser communication and provided clear imaging for the system.