Weather satellites are used to monitor Earth’s atmosphere, oceans, land, and ice. This information is vital for warning and forecasting severe weather events, such as tornadoes, floods, hurricanes and wildfires.
There are two main types of satellites: geostationary and polar orbiting. Both can measure atmospheric and surface parameters such as air temperature, cloud cover, moisture levels, wind speed and direction.
Geostationary Orbit
Weather satellites are usually located in geostationary orbit, which means that they are in a position over Earth at a fixed elevation. This allows ground-based antennas to stay pointed towards the satellite without requiring a constant change in direction.
This type of satellite is most common for telecommunications and weather monitoring purposes. Since it has an orbital period of one sidereal day, it appears stationary in the sky to ground observers. The first geostationary satellite was launched in 1963, and was popularized by science fiction writer Arthur C. Clarke in his 1945 article “Extra-Terrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?”
A geostationary orbit is an equatorial circular orbit in which a satellite remains directly over the same point on the equator. The inclination of this orbit is zero degrees, and it has a mean motion of 1.002701 revolutions per day (roughly 1436 minutes).
The satellite’s apogee engine “kicks” it into this orbit. It’s a solid-fuel rocket engine that provides the force necessary to keep the satellite in a stable, circular equatorial orbit.
In addition to their fixed location over the equator, geostationary satellites are also quite high above the Earth. This gives them a relatively wide field of view, with most of the Earth’s surface visible from their location.
However, their long distance from the Earth may cause them to wander about in orbit. This is called drifting or libration and can be harmful to other geostationary satellites.
To combat this, a small number of satellites have on board thrusters that help to correct the drifting behavior before it can become too severe. Some satellites, such as GOES (Goes West) satellites in the US, are even boosted at the end of their lifetime to prevent them from causing problems with other geostationary satellites.
Another problem is that geostationary satellites are prone to flare ups, or sudden increases in brightness. These are most often observed when they enter or leave the shadow of the earth’s equator about two weeks before and after each equinox. This is especially true during a solar storm, as the flares can be very bright and visible to many people.
Polar Orbit
When it comes to weather satellites, there are a couple of different types that are used for forecasting and monitoring the weather. One type, known as geostationary, orbits 22,236 miles above the equator and provides constant vigilance to monitor weather patterns and environmental conditions. The other, called polar orbiting, orbits around the polar regions of the Earth.
The orbit of a polar satellite is a circle that passes from pole to pole several times a day, so that it can collect data in a swath beneath the satellite. A swath is defined by a series of passes that are spaced a few kilometers apart from each other. The areas scanned are nearly adjacent at the equator on consecutive passes, and further pole-wards their overlaps progressively become less.
Many of the most widely used weather satellites are polar-orbiting. These satellites are primarily used for meteorological purposes, but they can also be used to study the Earth’s atmosphere, oceans, and land cover.
Some polar-orbiting satellites use microwave sensors to detect surface wind movements and help forecasters predict the direction and strength of storms. These microwave sensors measure the amount of radiation reflected or emitted by small wavelets that form when the ocean’s surface winds blow.
Since the 1980s, polar-orbiting satellites have provided information about surface wind motions and how they affect weather conditions. The data they collect is processed and analyzed to determine how changes in weather will impact people on the ground.
In addition, polar-orbiting satellites can capture images of the Earth’s surface that are more detailed than those from geostationary orbits. This allows meteorologists to see more detail in cloud structures and other weather phenomena.
These specialized satellites can also measure atmospheric pressure and temperature, as well as solar wind speeds and changes in sea ice. The information they provide is essential for developing accurate weather forecasts.
There are a few different kinds of polar orbiting satellites, but most are Sun-synchronous (SSO). These satellites synchronize their positions with the Sun so that they always observe a specific location at a fixed time each day. This is useful for comparing how something changes over time, and for using the data to compare different places on the Earth.
Low-Earth Orbit
In low-Earth orbit, satellites are located at an altitude of about 160 to 2,000 km (99 to 1200 mi) above the surface. These are the lowest altitudes attainable for human-made objects.
There are currently a total of thousands of LEO satellites, including imaging, weather, communications, and government satellites as well as the International Space Station (ISS). Every month, dozens of new satellites are launched into orbit.
Typically, satellites in this orbit follow an oval-type path called an ellipse. They have an orbital period of between 88 and 127 minutes, which is a little longer than the perihelion of the Earth’s orbit.
However, the orbits of satellites in low-Earth orbit can vary significantly. For example, a satellite in an elliptical orbit may have an altitude that can change by as much as 30 kilometers (19 miles).
This can cause some complications for the instruments onboard these spacecraft. For example, an elliptical orbit can be difficult for the satellite’s thermal control system to keep cool, especially when it is placed above the equator.
The same is true for polar-orbiting satellites, which are used for weather observations. These satellites are at a lower altitude than other types of orbits, so they can provide highly accurate observations of the Earth’s atmosphere and oceans.
These satellites also operate at a slower speed than other types of orbits. As a result, they can cover different areas of the Earth in each orbit. This is especially useful for observing ocean temperatures and the amount of carbon dioxide in the atmosphere.
In addition, polar-orbiting satellites can provide high-resolution imagery and sounder data for use in the modeling of climate change. The combination of these technologies enables the Joint Polar Satellite System to better inform the National Weather Service’s forecasting and warning systems.
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High-Earth Orbit
Weather satellites are used to monitor Earth’s weather and climate, identifying severe weather and environmental hazards. They provide critical data for forecasts and are also the first line of defense against tornadoes and hurricanes.
The most common types of weather satellites are geostationary and polar-orbiting satellites. The former orbit 22,236 miles above the equator, completing one orbit of the Earth in 24 hours.
This allows them to observe the same region of the Earth, allowing them to provide constant vigilance to identify and track storm systems in real-time.
Geostationary weather satellites, such as NOAA’s operational GOES-A and -B satellites, are located at an altitude of 35,786 km (22,236 miles). They take one day to orbit the Earth, so they appear to stay still from the ground, but in fact, they revolve at the same speed that Earth rotates.
In contrast, polar-orbiting satellites, such as NOAA’s Joint Polar Satellite System’s Terra and Suomi-NPP satellites, are located at an altitude below the equator. This is because it is more difficult to launch satellites from the equator than from other locations, so these satellites are launched from sites near the equator.
These satellites are often launched towards the east, which helps to accelerate the launch impulse. This is especially important for polar-orbiting satellites, since it increases the speed of the rocket’s propellant by 460 meters per second.
However, the disadvantage of this type of orbit is that it only covers a narrow area. This results in fewer pictures taken by these satellites, and less coverage in the tropics.
To avoid this problem, NOAA launches its polar-orbiting satellites from Guiana Space Center in French Guiana, which is a remote and pristine place that is not crowded and has no population centers. It also has access to open water towards the south or north, which is important for polar-orbiting satellites that need to cross the poles several times each day.
These satellites are often used for weather forecasts, especially to predict when a storm will move from the ocean to the land. This is done by tracking the storm’s movement and comparing it to previous weather patterns. The information is then used to create a forecast of the weather for the next few days.
Satellites can provide us with an abundance of data about Earth’s atmosphere, such as measuring rain, snow, ice, fire, cloud systems, dust storms, air pollution levels, volcanic ash deposits and ocean currents.
Weather satellites come in two primary varieties. Geostationary models orbit at high altitude above the equator and spin at an equal pace with Earth.
Geostationary
Geostationary weather satellites are situated above the equator at an altitude of around 22,236 miles (35,786 km). Their orbits around Earth follow its rotation in sync.
As seen in the animation above, geostationary orbits are stable – always remaining above a particular spot on Earth’s surface – enabling meteorologists to monitor any region by receiving updates every 15-60 minutes from satellite. This gives meteorologists access to vital meteorological data sets.
Forecasting requires multiple images for accurate prediction; one image alone cannot provide as much detail. Satellites such as GOES and METEOSAT provide full disk images of Earth as well as more focused zoom-in images to provide meteorologists with more comprehensive details about an area they’re monitoring.
United States weather satellites include five geostationary weather satellites: GOES-East and GOES-West provide coverage over eastern U.S. as well as Atlantic and Pacific oceans, while METEOSAT covers Europe.
Soon-to-launch satellites include two GOES-R Series satellites which will mark the next generation of geostationary environmental satellites – significantly improving atmospheric measurements and imagery collection capabilities.
These satellites not only possess imaging capabilities but can also detect atmospheric water vapor in the upper atmosphere to indicate moisture levels in the air. Their water vapor channels measure the amount of energy absorbed by water molecules at specific wavelengths in order to determine moisture content in the atmosphere.
Meteorologists use this spectral information to accurately predict rainfall intensity and location, cloud types and their movements over time and severe weather events more reliably.
Polar satellites also measure temperature and humidity levels in the atmosphere, track storm movements, tropical cyclones and can track tropical cyclones with enough precision for meteorologists to make accurate forecasts. Their resolution may be lower, but often capture enough data to enable meteorologists to make accurate forecasts. Wind speed/direction measurements as well as cloud cover information is provided by these satellites which allows meteorologists to predict where weather systems will form more accurately.
Polar
Weather satellites provide images of Earth to help forecast and prepare for extreme weather events, such as dust storms, forest fires, algae blooms, ice coverage, volcanic eruptions, heat waves and vast storms with embedded lightning.
Weather forecasts are created using data and imagery gathered by satellites and processed and disseminated to the public. The National Oceanic and Atmospheric Administration operates our weather satellite system, consisting of geostationary operational environmental satellites (GOES) for short-range warning and “nowcasting”, and polar weather satellites for longer term forecasting.
GOES satellites orbit Earth in a circular, sun-synchronous (see image below) orbit between 700 and 850 km altitude, slightly tilted northwestward for optimal data collection and efficient control by NOAA Command and Data Acquisition stations near Fairbanks, Alaska and Wallops Island, Virginia.
GOES satellites feature highly stable orbits; they remain in one spot over the Earth for roughly six hours before retreating back into storage positions. This allows the satellites to track cloud movement as well as receive transmissions from free-floating balloons, buoys, and remote automatic data collection stations.
GOES satellites use their high-resolution images to monitor storm development and track their path of movement, as well as help predict severe weather such as snowstorms or hurricanes.
GOES satellites help keep an eye on the Polar Vortex, a band of strong winds circling the North Pole that can produce some of the coldest weather on Earth, according to NOAA’s Laura Ciasto. Global warming may disrupt this natural phenomenon.
Climate change poses an existential threat to the polar climate, which explains why the ice caps that cover these areas are melting away. These ice caps serve as home to numerous animals such as polar bears and seals – essential parts of their ecosystem.
Undermining the polar climate are other threats such as overfishing, pollution of waters and habitat loss – each can impact wildlife as well as people alike.
High-Earth Orbit
Weather satellites in high-earth orbit provide meteorologists with images they use for forecasting. They also help track storms, hurricanes and other weather phenomena like volcanic ash or smoke from wildfires – something no other agency does as efficiently or reliably as NOAA’s mission of protecting lives, property and resources by providing accurate, up-to-date information for public consumption.
GOES system satellites are geostationary satellites that orbit 35,800 km above the equator and rotate at an equal pace as Earth itself, offering valuable weather monitoring. Their constant presence makes GOES satellites invaluable tools in tracking fast-developing weather events.
The National Oceanic and Atmospheric administration operates two satellites known as GOES East and GOES West that cover eastern U.S. and Canada as well as Hawaii and Mexico. GOES-East was launched June 25, 2008 for coverage over Atlantic region; on March 1 2018 its counterpart launched over 137o West region.
These satellites are aligned in line with the Sun, enabling them to observe all areas of Earth from space and providing a stable path for communication. Each of the satellites can be shielded against solar irradiation using a single heat shield.
Most satellites are placed near Earth’s equator, with an inclination angle of around 35 degrees, to minimize sunlight that reaches their solar panels, thus improving efficiency in data collection.
An orbit with such characteristics typically takes 12 hours to complete its trip and spends roughly two-thirds of that time centered over one hemisphere of Earth. This type of semi-synchronous orbit provides consistent and predictable results.
Molniya orbit is another medium-Earth orbit that’s highly eccentric, moving along an extreme ellipse with Earth close to one edge. This orbit lasts 12 hours with high-altitude part passing over same path every 24 hours.
Low-Earth Orbit
Many weather satellites orbit Earth in low Earth orbit, usually no higher than 1000 km above its surface and as low as 160 km above it.
Spacecraft orbits are critical in shaping how they view Earth and can transmit vital data back home. Some satellites remain stationary while others move across it all day long, giving a clearer perspective of global affairs than their stationary counterparts can offer.
As each satellite’s weather monitoring requires different altitudes, some orbit at lower or higher altitudes than others. For instance, Tropical Rainfall Measuring Mission (TRMM) satellite has an almost circular orbit near the equator with an inclination angle of 35 degrees.
This orbit enables satellites to view both day and night, making it easier for them to monitor rain, snow and other forms of precipitation as well as providing more detailed images of Earth’s surface.
Polar orbits are another common choice for weather satellites. They typically travel over both the North and South Poles every 100 minutes, providing observations such as cloud cover, surface distributions of ice and snow, sea surface temperature (SST), land surface temperature (LST), aerosol distribution patterns, etc.
These observations are fed into numerical weather prediction (NWP) models to help meteorologists make accurate and life-saving forecasts of the weather. NWP also gives meteorologists an image of what’s going on in the atmosphere that helps them identify wildfires, volcanic ash releases, and hurricane development.
Low-Earth-Orbiting satellites can also be used for communications. Working together as part of a constellation, these satellites form an invisibly thin net around Earth and cover vast regions, offering consistent coverage for various tasks such as telecoms or internet connectivity.