Weather monitoring by satellite
Weather satellite is primarily used to monitor weather and climate conditions on Earth. It can either be orbiting earth, or geostationary over a same spot on the equator.
Besides its primary use, It may also be used to monitor City lighting, fire, air and water pollution, and even energy waste. Depending on the type of sensor the satellite acquires.[1]
U.S. NOAA-N Prime weather satellite
History
The world's very first satellite launched was Vanguard 2, on February 17, 1959. It was designed to measure cloud cover and resistance, but due to its unstable axis rotation, the observed data could not be used.[2]
The world's first successful weather satellite was TIROS-1, launched by NASAon April 1, 1960. Which operated 78 days and was much more successful than Vanguard 2. [3]
Observation instruments / sensors in weather satellites
Visible Infrared Imaging Radiometer Suite (VIIRS)
VIIRS is a scanning radiometer, which collects visible and infrared light. It also does radiometric measurements of the land, atmosphere, cryosphere and oceans. Data that VIIRS collects is used to analyze cloud movements, water (sea and ice) amounts and temperatures and other visible phenomena’s. Data is also used to better understand the climate change.
It is a wide-swath (3,040 km) instrument with spatial resolutions of 370 m and 740 m at nadir. Its 22 bands span the spectrum between 0.412 micrometers and 11.5 micrometers.
- Mass: Approximately 275 kilograms
- Average Power: 200 Watts
- Development Institutions: Raytheon Company
- Purpose: To collect measurements of clouds, aerosols, ocean color, surface temperature, fires, and albedo.
VIIRS extends and improves upon a series of measurements initiated by the Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) [4] [5].
VIIRS and Ocean Science
Sea surface temperature and ocean pigment concentration measurements were started at 1978 with Nimbus-7 weather satellite and few years after 1981 continued with NOAA-7 weather satellite. These satellites gave benchmark information to researches behind Sea-viewing Wide Field-of-view Sensors (SeaWiFS) and the Moderate Resolution Imaging Spectroradiometer (MODIS), which both provided good quality data by increasing the spectral range and adjustment exactness.
VIIRS is alike to MODIS a multi-disciplinary sensor delivering data from oceans, surface, aerosol and clouds. VIIRS allows similar data to SeaWiFS from sea surface temperature, which is one of the most essential climate variables. VIIRS provides a global coverage every two days, which is similar to SeaWiFS and MODIS.
The VIIRS design includes equivalent turning telescope assembly as SeaWiFS, which shields the optical gears from on-orbit pollution. This design gives in better on-orbit steadiness. VIIRS alike to MODIS has a solar diffuser installed with a permanency observer for tracking on-orbit functioning in observable wavelengths, and a MODIS-like black body adjustment object for the infrared bands.
Typical necessity for ocean ecology and carbon research is a two-day coverage as microscopic marine plants are usual to vary, especially in coastal areas. VIIRS with a 750-meter resolution scan gives double coverage compared to MODIS and SeaWiFS, which is important improvement for coastal and estuarine research. VIIRS also provides additional shortwave infrared bands that give data that can be used for turbid water aerosol corrections.
VIIRS helps with the measurements of pigment concentrations; water clarity, suspended particulates and other properties coastal zone controlling, fisheries organization, and naval setups. Likewise, precise estimations of sea temperatures are needed for many purposes like hurricane prediction and weather forecasting [4][5].
VIIRS and Land Science
VIIRS mainly helps in energy and water balance, vegetation dynamics, land cover and the cryosphere. Energy and water balance analyses involve measuring surface albedo, photo synthetically active radiation (PAR), land surface temperature, evapotranspiration and the associated radioactive forcing and surface atmosphere exchanges. This information is used to parameterize local to global scale climate and hydrological simulations [4] [5].
VIIRS and Cloud Science
Already from 1980, weather satellites have included both imagers and sounders. These sensors record data by using different wavelengths to measure information of clouds all around Earth. The information is used to predict cloud formation, make weather forecast and gather information of clouds.
VIIRS provides data from clouds, aerosol and surface properties at a spatial resolution of 750 meters for most spectral measurements. VIIRS records data at a set of separate wavelengths from the ultraviolet (0.45 micrometers) to the infrared (12 micrometers). Cross-track Infrared Sounder
(CrIS) is a hyper spectral (> 1000 spectral wavelengths) sensor, which delivers complementary data from clouds, exclusively in difficult areas such as the poles, over bright surfaces such as snow and ice and in zones that have large temperature inversions [4] [5].
Instrument
The VIIRS is a 5-channel cross-track scanning radiometer that measures radiance in five bandwidths from the visible to the infrared spectral regions: 0.63, 1.6, 3.75, 10.80, and 12.0 micrometers at 2km resolution. Although the VIIRS mechanism is meant mainly to collect data from clouds and precipitation, it is also capable of recognizing active fires. The collected data is summarized every month and it is used to monitor natural and man-made fires in the Tropical and Sub-tropical areas (+/- 40 degrees from the equator) [6].
References:
[1] http://www.noaa.gov/satellites.html
[2] http://www.nrl.navy.mil/accomplishments/rockets/vanguard-project/
[3] http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1960-016A
[4] http://en.wikipedia.org/wiki/Visible_Infrared_Imaging_Radiometer_Suite
[5] http://npp.gsfc.nasa.gov/viirs.html
[6] http://wdc.dlr.de/sensors/virs/
[7] http://en.wikipedia.org/wiki/Moderate-Resolution_Imaging_Spectroradiometer