Shu Lin’s ‘Messaging Code’ Helps NASA Communicate with IRIS Spacecraft

Shu LinOne of NASA’s recent missions, the IRIS Solar Observatory, has been communicating its results via a 7/8 Low-Density Parity-Check (LDPC) code developed by Shu Lin, a professor in the UC Davis Department of Electrical and Computer Engineering. 

The Interface Region Imaging Spectrograph (IRIS) spacecraft was launched on June 27, 2013, aboard an Orbital Sciences Pegasus XL rocket. The IRIS mission addresses the need to understand the interface between the photosphere and corona, in our sun’s lower atmosphere: a fundamental challenge in solar and heliospheric science. The mission will trace the flow of energy and plasma through the chromosphere and transition region into the corona, using spectrometry and imaging. The goal is to extend the scientific output of existing heliophysics spacecraft that follow the effects of energy-release processes from the sun to Earth. 
The IRIS team opened the spacecraft’s telescope door on July 17, allowing scientists to view the mysterious lowest layers of the sun’s atmosphere; NASA described the data coming in as “crisp and clear, showing unprecedented detail of this little-observed region.” 

The information is being transmitted via Lin’s 7/8 LDPC code, a linear error-correcting code capable of sending accurate messages over a noisy transmission channel. In recent years, LDPC codes have become increasingly popular in applications that require reliable and highly efficient information transfer over bandwidth or return channel-constrained links in the presence of data-corrupting noise. Aside from their use by NASA, LDPC codes have become a standard for the satellite transmission of digital television, and also are part of the Wi-Fi 802.11 standard. 

After obtaining his PhD at Rice University in 1965, Lin served as a faculty member at the University of Hawaii (Manoa) and Texas A&M; he then returned to Hawaii to become Chair of the Department of Electrical Engineering at U:Manoa. He joined the UC Davis College of Engineering in 1999, where he has furthered his research into algebraic coding theory, coded modulation, error control systems and satellite communications. In 2002, Lin was part of the research team that shared in a $5 million DARPA grant designed to further the development of cell phone technology for optical communications. 

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