The Spacecraft uses an Earth-coverage pattern antenna to provide downlink for Direct Broadcast Users. It provides real-time mission data (which includes instrument
science data, instrument engineering data, and instrument telemetry data), and real-time Spacecraft housekeeping data. The data rate is 15 Mbps at a nominal downlink
frequency of 7812 MHz. In normal operations broadcast data will operate continuously providing real-time data to the Direct Broadcast Users.
For the JPSS-1 mission, the HRD direct broadcast is a continuous downlink of mission environmental data to users on the ground that are equipped with the resources necessary to capture the broadcast when the satellite is within view. The objective of the HRD content is to include the full set of science and calibration data from the mission instruments, as well as the spacecraft attitude and ephemeris data necessary for data product generation, in order to meet the needs of the direct broadcast community. However, due to the 15 Mbps HRD data rate transmission limitation, the content of the High Rate Data (HRD) direct broadcast may not be the same as the SMD. Since there are no explicit JPSS Level 1 data content requirements for the HRD downlink, any modifications to the HRD content will have to be negotiated between the JPSS program science and field terminal support personnel who represent the direct broadcast community for the JPSS program. As the content of the HRD link varies as a function of scene content and other factors, it is necessary to maintain the HRD data rate at a constant 15 Mbps using fill data as part of the spacecraft data packet processing.
The JPSS Program posted the Joint Polar Satellite System-2 (JPSS-2) Satellite High-Rate Data (HRD) to Direct Broadcast Stations (DBS) Radio Frequency (RF) Interface Control Document (ICD) on the JPSS Website. The ICD applies to JPSS-3 and JPSS-4 as well https://www.jpss.noaa.gov/technical_documents.html.