Structures, Pointing, And Control Engineering Laboratory


Digital Data Communication

An effective and efficient communication mechanism is necessary in an environment where image data and control signals must be disseminated in real-time or in off-line fashion for visualization, off-site analysis, and distance control. Key technologies toward this end include computer network protocols, image compensation, image/signal scalable compression (lossless/lossy compression for different research purposes, scalable browsing), and pre- and post-image processing (de-noising, enhancement, etc.).

For control signals, reliability is important; for astronomical images, scalable delivery should be supported to meet the requirements of different applications. In this activity, a prioritized transmission scheme is employed. For example, areas of interest (AOI) in the images will be assigned higher priority and a higher level of protection during transmission.

Compression is another important component of this activity. Due to the large volume of astronomical images, compression technology is essential to reduce communication cost as well as to achieve more efficient storage. Wavelet-based compression attracts a lot of attention due to its superior performance in texture compression, e.g. there is no block effect. In addition, the multi-resolution nature of wavelet transform supports scalable compression very well, which is a highly desirable feature for layered streaming, scalable browsing, among others. In this research, a real-time content-based wavelet image codec is designed to achieve time and space efficiency. For the continuous image sequence obtained by the telescope, 3-D wavelet compression is employed to increase the compression ratio. The quality of reconstructed images can be improved by pre- and post-processing them to remove possible noise and artifacts.