Implications of CrIS Full Spectral Resolution Operations on Suomi NPP High Rate Data Direct Broadcast

The suite of instruments on board the Suomi National Polar-orbiting Partnership (Suomi NPP) satellite, launched October 28, 2011, retrieve global measurements of the Earth's atmosphere, oceans, land surfaces, and near-space environment with precision and detail never before achieved by operational weather satellites. On February 28, 2012, Suomi NPP began to broadcast these instrument data real-time via the satellite's High Rate Data (HRD) antenna. The HRD broadcast provides users around the world with access to free, high quality sensor data that they can use for a wide range of applications from weather forecasting to disaster response. Suomi NPP transmits HRD at a fixed rate of 15.0 Megabits per second (Mbps), appending fill data to variable-sized sensor data as necessary to maintain this rate.

In 2012, members of the NOAA Suomi NPP science community successfully advocated for a program directive to change the permanent operational configuration of the Cross-track Infrared Sounder (CrIS) instrument, to acquire full-length interferograms in the Short Wave Infrared (SWIR) and Mid Wave Infrared (MWIR) bands. When operating in this “full spectrum” mode, the CrIS instrument generates data at a higher rate than the baseline, adding approximately 0.94Mbps of CrIS data to the total mission data stream. Since Suomi NPP broadcasts HRD at a fixed rate, it was necessary to perform an assessment of expected and observed peak instrument data rates to ensure the total data rate with CrIS in full spectrum mode remains within the 15.0Mbps specification for HRD. We found that expected peak data rates exceed this specification, and consequently have developed methods to optimize the composition and configuration of HRD. These innovative solutions will permit CrIS to operate in full spectrum mode, allow for HRD broadcast within its specification, and maintain Suomi NPP direct broadcast user requisites.

This paper will provide an overview of the current HRD configuration, implications of operating CrIS in full spectrum mode, and the results from our analyses of expected and observed instrument data rates that compose the HRD. We will present our mitigation strategies for a new HRD configuration that will allow NOAA to satisfy the program directive for CrIS full spectrum while preserving the fidelity of direct broadcast data products for the Suomi NPP user community.