A satellite is a body or mass which orbits a larger body or mass. The moon is an example of a satellite. Weather satellites are man-made machines that orbit the earth in either a sun-synchronous orbit (POES) or are geostationary (GOES) (see below). The sensors onboard weather satellites help to image and research atmospheric, oceanic and land systems by looking at specific frequencies in the electromagnetic spectrum. The most common frequencies sensed are visible light, infrared and microwave radiation. Weather satellites are initially placed into orbit with rocket boosters, or formerly by the Space Shuttle.
Satellites are useful for weather observation because they are at an ideal vantage point. Satellites are placed either in a low altitude orbit (POES) or in a high-altitude stationary spot (GOES), but both are well above the troposphere (the lowest sphere in the atmosphere) which is where most of Earth's weather takes place. This makes weather satellites immune to any weather effects and gives it a clear view of the weather patterns below.
Geosynchronous satellites are at a fixed position above the earth and are at a higher altitude than sun-synchronous satellites. The satellite is positioned at a high enough altitude from the Earth (usually around 22,236 miles) such that its orbital velocity coincides with the rotation of the Earth.
Essentially, the satellite's speed matches the speed of the Earth's rotation and the satellite appears to be stationary relative to a fixed point on the surface. An advantage of a geosynchronous satellite over a sun-synchronous satellite is that it can monitor the same area in a greater amount of time, thus improving the temporal resolution. GOES (Geostationary Operational Environmental Satellites), which are in a geosynchronous orbit, transmit data every 15 minutes of the CONUS (Continental United States) with a "full disk" (entire hemispheric) scan every 3 hours. Further, they are able to transmit data every minute (rapid scan mode) and every half minute (super rapid scan mode) for a particular area when scheduled. During severe weather events, such as hurricanes, data can be transmitted every 5 minutes for constant monitoring as was the case during Hurricanes Katrina (2005) and Rita (2005).
Although GOES satellites have a greater temporal resolution, the spatial resolution is more coarse with the exception of the visible imagery, which is approximately 1km. The spatial resolution of the remaining sensors range from 4km to 8km depending on the sensor (see table below for more information). weatherTAP receives data from two GOES satellites, GOES-10 (West) and GOES-12 (East) which cover most of the western hemisphere.