The Terra satellite was launched in 1999 as the flagship of NASA’s Earth science missions. The satellite provides data on trends in global carbon monoxide and other pollutants as well as monitoring the atmosphere, land, ice, and oceans. The image above shows the extent of the Deepwater Horizon oil slick (the grey galaxy-shaped spot) in the Gulf of Mexico in 2010. (NASA Earth Observatory/Jesse Allen)

The Landsat satellites have been providing spectacular global land images since 1972. In these nearly 40 years, the program has generated a historical archive unmatched in quality, detail, and coverage, allowing scientists to assess long-term changes to our planet. The latest satellite, Landsat-7, was launched in 1999, and provides images useful in agriculture, geology, forestry, surveillance, and education. Another satellite, Landsat-5, was launched in 1984 and is still functioning today. A new Landsat satellite is scheduled to launch in 2013. Sakurajima volcano in Japan has been erupting almost every year for 55 years. This image from 2000 shows a thin trail of smoke rising from the mountain. (NASA/Landsat)

The Aquarius satellite was launched in 2011. Jointly operated under NASA and Argentina’s National Space Activities Commission (CONAE), the Aquarius mission measures salt levels on the sea surface. Necessary for climate change computer models, salinity has mostly been detected from ocean-going boats in limited areas. Over its mission lifetime, Aquarius will make as many sea surface salinity measurements as the entire 125-year historical record from ships and buoys. This image shows a global map of sea surface salinity that Aquarius produced after its first two and a half weeks of data collection. (NASA/GSFC/JPL-Caltech)

These two satellites have a fun job: staring at clouds. Clouds are major players regulating the exchange of solar and thermal energy between the oceans, atmosphere, and space. Even small changes in cloud distribution can cause large changes in climate. CALIPSO was launched in 2006 and has been providing insight into the way that clouds and aerosol particles help regulate Earth’s weather and climate. CloudSat, also launched in 2006, uses radar to study the altitude and properties of clouds. The CALIPSO satellite’s 3 billionth image captured a vertical profile from space showing the smoke plume from wildfires in Arizona. (NASA/Kurt Severance, Jason Tackett and the CALIPSO team)

Suomi NPP was launched in 2011 and now orbits the Earth about 14 times each day to observe nearly the entire surface. Scientists use data from Suomi to create global models of temperature and moisture changes for weather forecasting and climate change simulations. Earlier this year, data from the Suomi satellite swept the Internet in this series of new images of our planet. (NASA/NOAA)

The Aqua satellite studies water. While this may not sound particularly exciting, data about precipitation, evaporation, and water cycling on Earth are crucial to understanding climate change. Launched in 2002, Aqua produces about 89 Gigabytes of data per day, including information on aerosols, vegetation cover on land, phytoplankton in the ocean, and air, land, and water temperatures. Carbon monoxide pollution rises from burning in the Amazon rainforest as well as forest fires in sub-Saharan Africa in this image. (AIRS Science Team at NASA/JPL)

Launched in 1997, the Tropical Rainfall Measuring Mission (TRMM) is a joint mission between NASA and the Japanese Space Agency JAXA. TRMM monitors tropical rainfall and the associated release of energy that helps power global atmospheric circulation, shaping both weather and climate. The satellite completed all of its research and technology objectives in 2001, and continues to provide data used worldwide in the monitoring and forecasting of hazardous weather. This image shows spring floods and mudslides in 2012 in the Dominican Republic, which have resulted in the deaths of at least nine people and forced 11,000 people to flee their homes. (NASA/TRMM)

The Gravity Recovery and Climate Experiment (GRACE) is a pair of twin satellites launched in 2002 to create the most precise measurements of the Earth’s gravitational field ever obtained. By detecting minute changes in gravity, the satellites allow scientists to monitor movements of ice sheets, underground water aquifers, and magma deep under the crust. GRACE also helps understand global ocean circulation and sea level rise, and has been used to analyze shifts in Earth’s crust from the earthquake that generated the 2004 Indian Ocean tsunami. This image features a gravitational model of the Americas, showing the distribution of mass. Red areas have higher gravity while blue have lower. (University of Texas Center for Space Research and NASA)

The Geostationary Operational Environmental Satellite (GOES) system has been a basic element of U.S. weather forecasting since 1974. There are currently four GOES satellites in geosynchronous orbit – meaning they are parked above one point on Earth – launched in successive waves between 2001 and 2010. The National Weather Service uses the continuously updated GOES data to monitor weather, storms, and the environment, while scientific researchers use the data to better understand land, atmosphere, ocean, and climate interactions. The next two GOES satellites are scheduled to launch in 2015 and 2017, respectively. The GOES-12 satellite snapped this shot of Hurricane Katrina in 2005. (NOAA OSEI, CIMSS and NOAA NESDIS ORA, NOAA SEC, CIMSS and NESDIS/ORA/ARAD/ASPT)

The Laser Geodynamics Satellites (LAGEOS) bounce laser beams off different points of the Earth and measure their separations to better than an inch in a thousand miles. LAGEOS 1, launched in 1976, and LAGEOS 2, deployed in 1992, have been used to determine tectonic plate movement and continental drift as well as measure the exact shape of the Earth. They have also determined with 99 percent accuracy the frame-dragging effect from the Earth’s gravitational field predicted by Einstein’s theory of general relativity. The first LAGEOS satellite carries a plaque designed by Carl Sagan, showing the numbers one through 10 in binary, the Earth orbiting the sun, and three maps: one showing the continents as they appeared 268 million years ago fused into one mass, another with the continents as they currently appear, and a third with an estimation of the Earth’s surface 8.4 million years from now, which is roughly how long the satellite will orbit before re-entering the Earth’s atmosphere. (Carl Sagan/NASA)

Two satellites, ACRIMSAT and SORCE, observe variations in the sun’s radiation. Scientists theorize that as much as 25 percent of Earth’s climate change may be solar in origin and even small changes in the sun’s output can cause significant climatological alterations. Built during NASA’s “faster, better, cheaper” phase, ACRIMSAT has been in orbit since 1999, with a total lifetime mission cost of less than $30 million. In 2005, the experiment noticed a drastic drop in solar irradiance levels caused by Venus’ 2004 transit between the Earth and sun, a decrease equal to all energy used by humans in a single year. SORCE was launched in 2005 and data from the satellite has been used to estimate past and future solar behavior and climate response. This image shows an artist conception of the ACRIMSAT. (NASA/JPL)

Two satellites, Jason-1 and the Ocean Surface Topography Mission (OSTM), measure the structure of the ocean. Monitoring both long-term events like El Niño and short-term changes in ocean circulation and interactions between the sea and atmosphere, the missions have helped improve climate-change models, hurricane forecasting, shipping routes, and can even track plankton and marine mammals. Jason-1 was launched in 2001 while OSTM took off in 2008. The satellites have spotted planetary-scale waves thousands of miles wide, which are driven by wind and the Earth’s rotation. Perhaps not surprisingly, their data is beloved by surfers. This image combines data from Jason-1 and OSTM taken after the 2011 Tohoku earthquake in Japan, confirming the existence of long-hypothesized “merging tsunamis” capable of traveling long distances without losing power. (NASA/JPL-Caltech/Ohio State University)

NOAA-N was launched in 2005 and is the 15th in a series of polar-orbiting satellites dating back to 1978. The latest satellite, NOAA-N Prime launched in 2009. The missions collect information about Earth’s atmosphere and environment. Severe weather is monitored, reported, and broadcast to the global community. The satellites also have instruments that support an international search-and-rescue program. COPAS-SARSAT transmits the location of emergency beacons from ships, aircraft, and people in distress to ground stations around the world. In place since 1982, the program has saved about 18,000 lives. This is a satellite image of North American weather from the NOAA-N satellite taken in 2007. (NASA/NOAA)

Aura looks at atmospheric chemistry, specifically monitoring the ozone layer, air quality, and global climate. It was launched in 2004, and has been used to confirm that levels of sulfur dioxide – a major contributor to acid rain and health problems — from eastern U.S. coal plants have fallen by nearly half since 2005.This image shows levels of sulfur dioxide from 2005 to 2007 and 2008 to 2010. (NASA’s Earth Observatory)

The EO-1 satellite is a gift that keeps on giving. Originally planned as a technology demonstration mission, the satellite was launched in 2000 and expected to last 12 months. Over its lifetime, it has produced many beautiful images of the Earth. This picture features lower Manhattan in New York City, shortly after the tragic events of Sept. 11, 2001. (NASA)

Launched in 1999, QuickScat provides data about winds over the ocean and has helped forecast tropical cyclones. Using the satellite, scientists found clear evidence that warm temperatures caused snow melt in a region of western Antarctica the size of California in January 2005. (NASA)