IJPS satellites series from EUMETSAT and NOAA provides meteorological data to users via direct broadcast to user receiving stations and recorded data that down load to IJPS ground stations. The stored data collected will be available to meteorological services at the raw data level within 2 hours and 15 minutes from the time of observation.

Summary of IJPS Recorded Data and Direct Broadcast Data

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.

Example of NOAA  AVHRR GAC 4 km Resolution

Example of NOAA  AVHRR LAC 1 km Resolution