Application of Airborne Remote Sensing Data Transmission System in Earth Environment Monitoring
1. System Scheme and Principle
In order to monitor disasters, there must be a remote sensor and a data link system. There are many kinds of remote sensors, so the data collected by sensors is different in bit rate, data scheme, etc. In order to meet the need of the sensors, a system with variable bit rate must be realized, The system is composed of a down-link subsystem and a receiver earth station. Fig 1. is the block diagram of the down-link subsystem on aeroplane.
Fig 1. Down-link Subsystem on Airplane
the need of monitoring different disasters, we can use the most sensitive sensors in the gathering of the important data, the weather also plays a key role in the choice of sensors, In flood, SAR is very sensitive to the difference of water and land, it is a microwave sensor which can be used in all weather. In the case of forest fire, MSS is sensitive to infrared ray. In evaluation the output of the plants, MSS is also suitable, but cloud and rain may decrease its efficiency.
The second is a data processing block and a modem, in the block, the image information is transformed to digital signals then to serial data ( fig.2 is the structure of the data ), then the data is sent to a modem and become QPSK signals, the data bit rate is 17.18Mb/s, IF is 70MHz, fig. 3 is the net-figure of modulated signal. Fig. 4 is the frequency spectrum of IF.
Fig 2. Data Structure
Fig 3. Net-fig of QPSK
Fig 4. IF specturm of modem
