美国空军的研究人员正在美国几个地点将激光宙达射入天空,为国家航天飞机计划取得大气密度的数据。汉斯科姆空军基地的空军地球物理实验室有两台激光雷达工作,一台为装在拖车上的可移动装置,另一台为功率较大的屋顶型装置。研究人员两个月前开始开动其中一台的激光系统,每周一个晚上,定期工作。两年来该装置一直不断地运转。长时间的测量结果将用于表征80～100公里高处的大气密度。为了得到大气密度的测量结果,将激光束射向天空,在大气较高层处的粒子使一小部分光返回发射点,发射点的接收器可接收到后向 Researchers at the U.S. Air Force are launching a laser beam into the sky at several locations in the United States to obtain atmospheric density data for the state space shuttle program. The Air Force Geophysical Laboratory at Hanscom Air Force Base operates with two LIDARs, one for the mobile unit mounted on the trailer and the other for the more powerful roof-mounted unit. The researchers started the laser system on one of them two months ago, working one night a week and on a regular basis. The device has been running continuously for two years. Long time measurements will be used to characterize atmospheric density at altitudes of 80-100 km. To obtain atmospheric density measurements, a laser beam is directed to the sky and particles in the upper layers of the atmosphere return a small fraction of the light back to the launch site. The receiver at the launch site receives the backward