SOURCEFORGE » RALF » 2015 Weather images of NOAA satellites

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h1. *2.1 NOAA and POES*

NOAA (National Oceanic and Atmospheric Administration) satellites are American meteorological polar orbit satellites which observe the Earth from about 850 km heigh. They are part of the Global Meteorological Organisation. The National Oceanic and Atmospheric Administration (NOAA) [www.noaa.gov/] is a federal agency that focuses on the condition of the oceans and the atmosphere. It is an American scientific agency in the the United States within the Department of Commerce. NOAA objectives are a holistic understanding of the Earth system through research, accurate and reliable data from sustained and integrated earth observing systems and an integrated environmental modelling system. [1]

Their main missions are to observe the meteorological phenomenon, to map the thermical structure of the oceans and to study the coastal environment evolution.

The first one has been put into orbit in 1970. 18 more NOAA satellites have been sent since this year.

The National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA) [https://www.nasa.gov/] have jointly developed a number of series of Polar-orbiting Operational Environmental Satellites (POES). The system consists of a pair of satellites, which ensures that every part of the Earth is observed at least twice every 12 hours. The satellites provide global coverage of numerous atmospheric and surface parameters, providing quantitative measurements for atmospheric and model forecast models. Thus, enabled consistent and accurate prediction and allowed avoidance of catastrophic environmental events. Last but not least, many countries and over much of the oceans satellite data is the only source of weather information.

This serie of satellites started flying in 1978 and was named Advanced TIROS-N (ATN), after the prototype satellite TIROS-N (Television Infrared Observation Satellites). It has been credited for saving over 24,500 lives since 1982 by detecting and locating emergency beacons from ships, aircraft and people in distress.

In 1998, the European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) [www.eumetsat.int/] and NOAA agreed to collaborate in the Initial Joint Polar-orbiting Operational Satellite System (IJPS). The mission objectives were to collect and exchange polar satellite data between NOAA and EUMETSAT for improved meteorological and environmental forecasting. This agreement commits NOAA to provide the NOAA-18 and NOAA-N Prime and EUMETSAT agrees to provide three European built-in satellites MetOP-A, MetOP-B and MetOP-C. MetOP (Meteorological Operational) carries a new generation of operational meteorological European instruments developed my EUMETSAT, ESA (European Space Agency) [www.esa.int] and CNES (Centre National d'Etudes Spatiales).[https://cnes.fr/en].

MetOp-A was launched in October 2006 and MetOp-B was launched in September 2012. At an altitude of 817 km, it takes about 100 minutes to complete one orbit. During the time it needs to complete an orbit, the Earth has rotated around 25° which means observations are made over a different section of the Earth in each orbit. Within the Joint Polar System, MetOp is responsible for the morning orbit which passes over the Equator at 09.30 local time, whilst the NOAA satellite occupies the afternoon orbit which passes over the Equator at 14.30 local time.

h2. *2.1.1 NOAA-N Prime Instruments*

The NOAA satellites are equipped with a sensor called AVHRR (Advanced Very High Resolution Radiometer).

It is a radiometer which has a large observation coverage.

* AVHRR/2 2600km coverage, 0,5 km resolution in visible frequencies and 1,0 km in IR

* AVHRR/2 2940km coverage, 0,5 km resolution in visible frequencies and 1,0 km in IR

This sensor is able to map the vegetation, the clouds and is able to measure the temperature and the humidity both in the atmosphere and on Earth (0,12°c resolution in IR).

NOAA-N Prime is the latest satellite in the ATN series and carries the following instruments :

*AVHRR/3* – Advanced Very High Resolution Radiometer:

The instrument measures reflected solar (visible and near-IR) energy and radiated thermal energy from land, sea, clouds, and the intervening atmosphere.

*HIRS/4* – High Resolution Infrared Radiation Sounder: The instrument measures scene radiance in the IR spectrum. Data from the instrument is used, in conjunction with the AMSU-A instrument, to calculate the atmosphere’s vertical temperature profile from Earth’s surface to about 40 km altitude. The data is also used to determine ocean surface temperatures, total atmospheric ozone levels, water, cloud height and coverage, and surface radiance.

*AMSU-A* – Advanced Microwave Sounding Unit-A: Measures scene radiance in the microwave spectrum. The data from this instrument is used in conjunction with the HIRS to calculate global atmospheric temperature and humidity profiles from Earth’s surface to the upper stratosphere, approximately 48 km of altitude. The data is used to provide precipitation and surface measurements including snow cover and sea ice concentration.

*MHS* – Microwave Humidity Sounder: The MHS is a five-channel microwave instrument intended primarily to measure profiles of atmospheric humidity. It is also sensitive to liquid water in clouds and so measures cloud liquid water content. Additionally, it provides qualitative estimates of the precipitation rate.

*SBUV/2* – Solar Backscatter Ultraviolet Spectral Radiometer: The SBUV/2 measures solar irradiance and Earth radiance (backscattered solar energy) in the near ultraviolet spectrum and the properties opbtained by thes data are:

The global ozone concentration, the vertical distribution of atmospheric ozone, the long-term solar spectral irradiance and the photochemical processes and the influence of “trace” constituents on the ozone layer.

*SEM-2* – Space Environment Monitor: The SEM-2 provides measurements to determine the intensity of Earth’s radiation belts and the flux of charged particles at satellite altitude.

*ADCS* – Advanced Data Collection System: The ADCS has a downlink transmitter (TXU). The function of the TXU is to send messages to beacons on the ground but also receiving processing messages from the next generation of beacons.

*IASI* – Infrared Atmospheric Sounding Interferometer : Atmospheric temperaure information

*ASCAT* – Advanced Scatterometer : Ocean surface wind speed and direction

*GOME-2* – Global Ozone Monitoring Experiment : Ozone observations

*SAR* – Search And Rescue Instruments

*DDR* – Digital Data Recorder: Recording and data storage system that stores selected sensor data during each orbit for subsequent playback.

h2. *2.1.2 NOAA Data Transmissions*

The spacecraft transmits instrument data to the ground for three primary functions: Data Acquisition, Direct Broadcast, and Search and Rescue. 

There are three types of direct broadcasting: real-time HRPT, real-time very high frequency (VHF) beacon transmissions and Automatic Picture Transmission.

HRPT - High Resolution Picture Transmission: HRPT provides worldwide direct readout of full-resolution spacecraft parameters and instrument data to ground stations within the footprint of the NOAA polar-orbiting satellite.

APT – Automatic Picture Transmission: APT data is smoothed 4-km resolution IR and visible imagery derived from the AVHRR/3 instrument and transmitted within the footprint of the NOAA polar-orbiting satellite. The data is transmitted continuously over a dedicated VHF link as an analog signal consisting of an amplitude-modulated 2400Hz subcarrier frequency modulating the RF carrier at 137.1 MHz or 137.9125 MHz.

h2. *2.1.3 NOAA Characteristics*

Characteristics of the operations fleet of NOAA satellites.

|\4=._Table 2.1_ NOAA Characteristics                         |

|                    |NOAA 19 (Prime) | NOAA 15     | NOAA 18 |

|Altitude [km]        |   870         | 807         | 854     |

|Period   [min]            | 102.14   | 101.1       | 102.12  |

|Inclination Angle [degrees] | 98.7   | 98.5        | 98.74   |

The Advanced Very High Resolution Radiometer (AVHRR) in NOAA 15 is in yellow status indicating operational limitations or standby mode [2].

h2. *2.1.4 AVHRR/3 Characteristics*

|\2=._Table 2.2_ AVHRR/3 Characteristics                         |

|Full name | Advanced Very High Resolution Radiometer / 3 |

|Type of Instrument | Moderate-resolution optical imager |

|Purpose | Multi-purpose imagery |

|Short description| 6-channel radiometer covering VIS, NIR, SWIR, MWIR and TIR 

[see detailed characteristics below] |

|Background| Evolution of the AVHRR/2 flown on NOAA-7/9/11/12/13/14. SWIR channel added, 

transmitted in alternative to MWIR. Operations on NOAA-17 stopped in 2010|

|Scanning Technique| Cross-track: 2048 pixel of 800 m s.s.p., swath 2900 km 

Along-track: six 1.1-km lines/s|

|Resolution | 1.1 km s.s.p. IFOV |

|Coverage / Cycle | Global coverage twice/day (IR) or once/day (VIS) |

|Mass | 33kg|

|Power | 27W |

|Data Rate | 621.3kbps |

h2. References

[1] http://www.ppi.noaa.gov/enterprise-objectives/

[2] http://www.ospo.noaa.gov/Operations/POES/status.html#noaa15