Help understanding this passage 首次在天空中被人目击不到两年之后，中国新型“空警”-500预警机已经加入现役。“空警”-500预警机可以同时对470公里范围内的60多架飞机进行跟踪。“空警”-500“空中预警与控制系统”(AWACS)看起来更像是美国的空中预警机(其上部有圆形雷达穹顶)，但体积小一些，由运-9四引擎涡轮螺旋桨飞机(类似于美国的C-130)搭载。

I know what the first sentence means, but what I am getting from this passage is that the AWACS is slightly smaller than the 空中预警机 and needs transporting by another vehicle, but a search on google images shows that it is an independent jet.  This is from sina.com
Hope I didn't make too many mistakes! Makes a change from my text book!

首次在天空中被人目击不到两年之后，

For the first time in the air in 2 years, 

中国新型“空警”-500预警机已经加入现役。

China's new type of 'sky patrol' early warning aircraft has joined active service.

“空警”-500预警机可以同时对470公里范围内的60多架飞机进行 跟踪。

This 'sky patrol'-500 early warning aircraft can simultaneously track more than 60 aircraft within a radius of 470 Kilometers.

“空警”-500“空中预警与控制系统”(AWACS)

'Sky patrol'-500 airborne early warning and control system (AWACS) 

看起来更像是美国的空中预警机，

resembles the American airborne early warning system 

(其上部有圆形雷达穹顶)

(whose upper section is a circular radar dome)

但体积小一些，

however, the dome is somewhat smaller,

由运-9四引擎涡轮 螺旋桨飞机

The aeroplane is powered by 4 Yun-9 turboprop engines

(类似于美国的C-130)搭载。

(similar to the American C-130) transporter aircraft.