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GOES Rebroadcast (GRB)

The GOES-R Series satellite’s scientific instruments sense the environment and distribute data to the onboard computer for processing and distribution to the X-Band antenna for transmission to Earth as a digital data stream. The ground system software at Wallops Command and Data Acquisition Station (WCDAS) processes the Level 0 data and creates Level 1b products. For example, the measurements from the ABI are converted to units of radiance and calibrated, navigated, and remapped to a fixed grid. The antenna at WCDAS transmits the products to the GOES-R Series satellite for relay through the satellite’s GOES Rebroadcast (GRB) transponder and L-Band antenna to GRB receive stations, including GRB receive stations at the NOAA Satellite Operations Facility (NSOF).

The GRB provides the primary GOES-16 and GOES-17 relay of full resolution, calibrated, near-real-time direct broadcast Level 1b data from each instrument and Level 2 data from the Geostationary Lightning Mapper (GLM). The GRB is a significant increase in capability from the GOES VARiable (GVAR) service on GOES 13, 14, and 15. The GRB contains the ABI, GLM, space environment, and solar data that drive the data flow in the NOAA space and Earth environment research and operational frameworks.

To receive the GRB signal, a user installs a receive station consisting of an antenna, Low Noise Amplifiers, RF/Intermediate Frequency (IF) downconverter, Digital Video Broadcasting-S2 (DVB-S2) capable receiver and GRB-compatible demodulator, and processing software. The GRB link data rate is 31 Mbps and between 1.5 TB and 2 TB of data are transmitted during a 24-hour period.

The GRB data stream includes the ABI Level 1b products. In Mode 4, or Continuous full disk mode, the ABI produces a full disk image every 5 minutes. In Mode 3, or Flex Mode, the ABI produces a full disk every 15 minutes, a CONUS image (resolution 3000 km by 5000 km) every 5 minutes, and two mesoscale domains (resolution 1000 km by 1000 km) every minute or one domain every 30 seconds if it is set to that scanning rate. All 16 Bands are available. A new mode, Mode 6, is being tested and if approved by NESDIS and NWS then it would provide a full disk image every 10 minutes, CONUS image every five minutes, and images from both mesoscale domains every minute.


GRB to GVAR comparison

GOES
Variable
(GVAR)
GOES
Rebroadcast
(GRB)
Full
Disk
Image
Hemispheric
view every
30 minutes
5 mins (Mode 4),
15 mins (Mode 3),
and 10 mins (Mode 6)
Other
Modes
Rapid Scan,
Super Rapid
Scan
3000 km X 5000 km
(CONUS: 5 minute)

1000 km X 1000 km
(Mesoscale: 30 seconds)
Polarization None Dual Circular Polarized
Polarization None Dual Circular Polarized
Receiver
Center Freq
1685.7 MHz
(L-Band)
1681.6 MHz
(L-Band)
Date Rate 2.11 Mbps 31 Mbps
Antenna
Coverage
Earth Coverage
to 50
Earth Coverage
to 5
Data
Sources
Imager
and
Sounder
ABI (16 bands),
GLM, SEISS,
EXIS, SUVI,
MAG
Space
Weather
None ~2 Mbps
Lightning
Data
None 0.5 Mbps

In addition to the NOAA NESDIS GRB receive stations at the WCDAS, NSOF, and CBU, about 70 other sites have installed or plan to install GRB receive stations.

The GRB downlink signal from the satellite is at a center frequency of 1686.600 MHz and requires an antenna gain-to-noise-temperature (G/T) of 15.2 dB/K for worst-case locations. Modulation is either 8PSK with a symbol rate of 7.825768 Million symbols per second (Msps) with a rate 2/3 Forward Error Correction coding or QPSK with a symbol rate of 8.665938 Million symbols per second (Msps) with a rate 9/10 Forward Error Correction coding. However, the GOES-R program designated QPSK the default modulation mode in 2017. The nominal antenna size: 4.5-meter dish with a system noise temperature of 120 degrees Kelvin. Off-the-shelf DVB-S2 receivers are available to receive the IF outputs from the antenna system for each polarization. The DVB-S2 receiver extracts and outputs CCSDS Channel Access Data Units (CADUs) at a rate of 15.5 Megabits per second (Mbps) from each polarization channel. The dual circular polarization facilitates a data rate of 31 Mbps. For more information go to GRB Downlink Specifications.

The Product Definition and Users’ Guide (PUG) Volume 4 describes the GRB product content and format and documents the communications and application level protocols used in the GRB. The PUG Volume 4 lists the products that are on the Left Hand Circular Polarized (LHCP) channel and on the Right Hand Circular Polarized (RHCP). The ABI Level 1b products on the LHCP channel are similar to the products that were available on legacy GOES Variable (GVAR) DB service provided by GOES-NOP.For more information go to PUG Volume 4.

GRB users can generate products with software purchased from a vendor, developed by the user, or downloaded from the University of Wisconsin – Madison Space Science and Engineering Center’s (SSEC) Cooperative Institute for Meteorological Satellite Studies (CIMSS). SSEC/CIMSS developed the Community Satellite Processing Package for Geostationary Data (CSPP Geo) software with funds provided by the GOES-R Program Office.

As of January 2019, NESDIS had accounted for 100 GRB receive stations are accounted for (planned and installed). GRB is a broadcast so registration is not required. NESDIS requests that users complete a survey on the DCS Administration and Data Distribution System (DADDS) website and join the GRB User Group.

View GRB for more information.

The Rebroadcast (Grb) Downlink Specifications For Users, August 6, 2012, is available at:
https://www.goes-r.gov/users/docs/GRB_downlink.pdf

GOES-R Series GRB Ground Antenna Sizes

Also The George C. Marshall Space Flight Center maintains a GOES Health Monitor.