EXAMPLES data downloaded from CLASS and processed with HRPT Reader

The Comprehensive Large Array-data Stewardship System (CLASS) is NOAA’s information technology system designed to support long-term, secure preservation and standards-based access to environmental data collections and information. The NOAA National Data Centers are responsible for the ingest, quality control, stewardship, archival storage of and public access to data and science information. The CLASS system is modeled to support the NOAA-adopted Open Archival Information System-Reference Model (OAIS-RM), which identifies high-level roles and responsibilities of various archival components and illustrates the connections between functional entities in order to fulfill archive requirements.

With the prospect of higher data-rate earth observation systems planned for deployment and the incorporation of existing NOAA data collections into the Data Centers, management of these exponentially increasing volumes of environmental data will require a rapid expansion in storage capacity, additional access methods, and improved automation of data ingest, archive and quality control. Together, the NOAA National Data Centers, utilizing the IT infrastructure of CLASS, will provide the necessary ingredients to fulfill NOAA's data stewardship mission.

Currently, the NOAA National Data Centers support POES, DMSP, GOES, MetOp, Jason-2 data, and selected model reanalysis data within the CLASS infrastructure. Future satellite-based collections planned for archival storage in the system include NPP, JPSS (formerly NPOESS), GOES-R, Jason-3, and planned Earth-based observing systems include NEXRAD products. To ensure the preservation of these data, the distributed system replicates data and metadata holdings automatically to operational nodes at the National Climatic Data Center in Asheville, NC, and the National Geophysical Data Center in Boulder, CO. System development and integration is located at NOAA’s Satellite Operations Facility in Suitland, MD and is managed by the Office of Systems Development Ground Systems Division.



IJPS Satellite Direct Broadcast Services
Satellite direct broadcasting, more commonly called direct readout service, is used to distribute "raw" or minimally preprocessed satellite data to anyone anywhere in the world in real-time. The direct broadcasts supported by all IJPS satellites are the High Resolution Picture Transmission (HRPT) of AVHRR at 1 km. The HRPT transmissions also include soundings from the Advanced Microwave Sounding Unit/A1 and A2 (AMSU) instruments. For the low resolution direct broadcast, NOAA POES will continue to use the Automatic Picture Transmission (APT) while METOP will provide the Low Resolution Picture Transmission (LRPT) of AVHRR at 4 km.

A satellite passing directly over an antenna site will be within view of the antenna (horizon-to-horizon) for about 15 minutes when the satellite is at 833-km altitude for about 16 minutes when the satellite is at an altitude of 870 km. Coverage is the area the satellite can see while it can be seen from the ground station. For an overhead pass of the satellite, this area is ~ 6,200 x 3,200 Km

NOAA High Resolution Picture Transmission (HRPT) Service
The HRPT data are digital and include all five channels of AVHRR data as well as AMSU, HIRS/3, SEM, SBUV/2 data and satellite house keeping telemetry data. Resolution is 1 km at nadir and about 0.7 degree C accuracy on sea surface temperature products.

The data are transmitted to the ground receiving stations by one of three 5.25 Watt, S-Band transmitters coupled to one of three quadraphase antennas on the NOAA satellites. The S-Band, real-time data consists of a split-phase PSK digital bit stream at 665.4 Kbits per second at 1698 MHz or 1707 MHz, Right hand Circular Polarization. The HRPT data may also be transmitted on 1702.5 MHz, Left-hand Circular Polarization.

Example of NOAA AVHRR HRPT 1 km Resolution.

NOAA Automatic Picture Transmission (APT) Services
APT services and subsystems were initially designed to broadcast direct readout satellite imagery to low-cost ground receiving equipment. In 1990, more than 5000 stations, established in at least 123 countries, received APT data from U.S. and Russian satellites. APT signals from U.S. satellites are transmitted on 137.50 or 137.62 MHz FM transmitters as a 2.4 KHz DSB-AM subcarrier. Basic receivers consist of a low-cost steerable helix, yagi or omni-directional antenna, VHF receivers, and a display device such as a personal computer, a facsimile receiver, a photographic device or a CRT. APT data are acquired whenever a NOAA POES passes within range of a ground station (at least four times in a 24 hour period). The number of satellite overpasses depends on the latitude of the station; high latitude stations can receive far more than four passes a day. Each station receives only while the spacecraft is within range (for about 15 minutes). The data rate is 33.28 Kbps. Only two of the five AVHRR channels are transmitted. The AVHRR channels are described in IJPS instruments. Besides providing the location of clouds, the data, depending on the presence or absence of clouds, will provide cloud top or sea surface temperature (SST) to an accuracy of ~2 degree C with a 4 km resolution.

NOAA GAC and LAC Coverage Stored On-board Satellites
The NOAA National Environmental Satellite, Data and Information Service (NESDIS) maintains ground stations at Wallops Island, Viginia and Fairbanks, Alaska to capture POES data stored onboard satellites both for immediate use and for permanent archiving.

The 4-km, low resolution data are known as Global Area Coverage (GAC). An entire orbit of GAC (115 minutes) can be stored by a single recorder. Only 11.5 minutes of high- resolution imagery (1.1-km resolution), known as Local Area Coverage (LAC) can be stored on a single recorder. LAC therefore must be scheduled.

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