An application

Intelligent on board image coding

Motivation:

The wide usage of small satellite imagery, especially its commercialization makes application based on-board compression not only meaningful but also necessary in order to solve the bottleneck between the huge volume of data generated on-board and the very limited downlink bandwidth: A Surrey microsatellite can hold in memory roughly 200 images, but remains over the horizon of the tracking station for approximately 10 minutes. During this time only a couple of images can be downloaded.

Solution:

• According to the specific application, the regions of interest are identified on-board. The region identification algorithms include:

  • Maximum Likelihood Classification for multi-spectral images;
  • Texture boundary detection with morphological postprocessing to detect land regions for panchromatic land/sea images;
  • Region-growing based algorithms to detect clouds in panchromatic images;
  • Other customized region identification methods.

• Encode arbitrarily shaped regions with different shape-adaptive coding schemes. Candidate schemes include:

  • Block DCT based shape adaptive coding[2]
  • Object-based Wavelet Transform (OWT)[1]
  • Convert 2-D regions to 1-D signal with Hilbert scan and encode with 1-D wavelet coding.