  Nowadays, hyperspectral imaging is recognized as cornerstone remote sensing
technology. The explosive growth in image data volume and instrument data
rates, compete with limited on-board storage resources and downlink bandwidth,
making hyperspectral image data compression a mission critical on-board
processing task. The Consultative Committee for Space Data Systems (CCSDS)
extended the previous issue of the CCSDS-123.0 Recommended Standard for multi-
and hyperspectral image compression to provide with Near-Lossless compression
functionality. A key feature of the CCSDS-123.0-B-2 is the improved Hybrid
Entropy Coder, which at low bit rates, provides substantially better
compression performance than the Issue 1 entropy coders. In this paper, we
introduce a high-throughput hardware implementation of the CCSDS-123.0-B-2
Hybrid Entropy Coder. The introduced architecture exploits the systolic design
pattern to provide modularity and latency insensitivity in a deep and elastic
pipeline achieving a constant throughput of 1 sample/cycle with a small FPGA
resource footprint. This architecture is described in portable VHDL RTL and is
implemented, validated and demonstrated on a commercially available Xilinx
KCU105 development board hosting a Xilinx Kintex Ultrascale XCKU040 SRAM FPGA,
and thus, is directly transferable to Xilinx Radiation Tolerant Kintex
UltraScale XQRKU060 space-grade devices for space deployments. Moreover,
state-of-the-art SpaceFibre (ECSS-E-ST-50-11C) serial link interface and test
equipment were used in the validation platform to emulate an on-board
deployment. The introduced CCSDS-123.0-B-2 Hybrid Entropy Encoder achieves a
constant throughput performance of 305 MSamples/s. To the best of our
knowledge, this is the first published fully-compliant architecture and
high-throughput implementation of the CCSDS-123.0-B-2 Hybrid Entropy Coder,
targeting space-grade FPGA technology.
