Shuttle Radar Topography Mission

A space ship went on a big mission.

It flew for eleven days in space. The ship had two tools to look down. One tool sat on a long pole.

These tools used light to make a map. This map shows where the land is high or low. It shows big mountains and deep valleys. People can use these maps for free on the web. It is a way to see our whole world.

The Shuttle Radar Topography Mission, or SRTM, was a big project.

It used a space shuttle to map our Earth. The mission lasted for 11 days in February 2000. It used a special tool called radar. Radar uses waves to see the ground from space.

The shuttle had two antennas to help it work. One antenna sat in the payload bay. The other sat on a long mast. This mast was 60 meters long. Using two antennas allowed for single-pass interferometry. This is a way to make very good maps. The radar used two types of waves. The C-band gave wide coverage. The X-band gave high resolution, which means more detail.

These maps show the height of the land. They show mountains and deep canyons. Some parts of the maps have gaps. These gaps happen in very high mountains. Scientists work hard to fill these empty spots. Many people around the world use this data. You can even download it for free online.

The Shuttle Radar Topography Mission, or SRTM, was a huge project to map our world.

It created digital elevation models, which are maps that show the height of the land. These maps cover a massive area from 56°S to 60°N. This means they show almost the whole Earth except for some parts. This work was very important for making high-resolution maps. Before this mission, we did not have such a complete view of the Earth's surface.

The mission worked using a special way to use radar called interferometric synthetic aperture radar.

The shuttle used two different antennas to do this job. One antenna stayed in the payload bay of the shuttle. The other antenna sat on a long mast that was 60 meters long. The mast extended out into space once the shuttle was in orbit. The radar used two types of waves called C-band and X-band. The C-band provided wide coverage of the ground. The X-band had a narrower coverage but provided much higher resolution.

This mission took place in February 2000. It was an 11-day mission called STS-99. The shuttle used for this work was the Space Shuttle Endeavour. The project was led by two big groups in the United States. These were the National Aeronautics and Space Administration, known as NASA, and the National Geospatial-Intelligence Agency. Intermap Technologies was the main company that helped process all the radar data. In 2003, NASA moved the mission tools to a museum. You can see the antenna and mast at the Udvar-Hazy Center in Virginia.

There are many important facts about the data the SRTM collected. The raw data has a resolution of one arcsecond. This means each piece of data covers about 30 meters on the ground. The maps show many places like Africa, Europe, North America, and Asia. Some areas have gaps in the data. These gaps often happen at very high mountain summits over 8,000 meters. They also happen in deep canyons or gorges. Some scientists use special math to fill these empty spots.

You can see how this mission links to the world around you. Many people use these maps in geographic information systems to study the Earth. You can even download these files for free over the Internet. In 2011, there were already 750,000 people using this data. People from 221 different countries have accessed these maps. These maps help us understand the shape of our mountains and valleys. They turn invisible radar waves into a picture we can see.

The Shuttle Radar Topography Mission, known as SRTM, was a massive international research project.

Its primary goal was to create digital elevation models of the Earth. These models are digital maps that show the height and shape of the land. The mission captured data on a near-global scale. It covered a vast area from 56°S to 60°N latitude. This effort provided the most complete high-resolution topographic database available at that time.

These maps are vital for geographic information systems. They help scientists and researchers understand the physical structure of our planet.

The mission used a sophisticated technique called interferometric synthetic aperture radar. This process relies on two different radar antennas to measure the Earth's surface. One antenna was located inside the payload bay of the Space Shuttle. The second antenna was mounted on a 60-meter mast. This mast extended from the payload bay once the shuttle reached space.

The radar system operated using two specific frequencies: C-band and X-band. The C-band provided a wider aperture, which allowed for broader coverage under the shuttle's tracks. In contrast, the X-band had a narrower aperture but offered much higher resolution. This dual-band approach allowed the mission to capture both wide areas and fine details.

The SRTM mission was a collaborative effort between several major organizations. The project was spearheaded by the U.S. National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA). The NGA is an agency of the U.S. Department of Defense. Intermap Technologies served as the prime contractor for processing the complex radar data. The mission itself was the STS-99 flight of the Space Shuttle Endeavour. It took place over an 11-day period in February 2000.

After the mission, NASA transferred the hardware to the Smithsonian National Air and Space Museum. The antenna and mast are now displayed at the Steven F. Udvar-Hazy Center in Virginia.

Data from the mission is organized into specific digital tiles. Each tile covers one degree of latitude and one degree of longitude. These tiles are named based on their southwestern corners, such as "n45e006." The raw data resolution is one arcsecond. At the equator, this resolution represents about 30 meters on the ground. This high-resolution data covers much of Africa, Europe, North America, South America, Asia, and Australia. For the rest of the world, the available data is at a three-arcsecond resolution. This means those areas have a resolution of about 90 meters.

Despite the mission's success, some areas of the data contain "voids" or gaps. These gaps are most common in areas of very high relief. They affect almost all mountain summits over 8,000 meters and most summits over 7,000 meters. Voids also appear in many deep gorges and canyons. These gaps account for about 0.2% of the total surveyed area. In the Version 2 data, these voids covered approximately 836,000 square kilometers.

Scientists have developed different ways to handle these empty spaces. Some use interpolation, which is a mathematical way to estimate values based on surrounding data. However, if a void is too large, such as over a major ridge, interpolation may be inaccurate.

NASA has released several versions of the SRTM data over the years. Version 1, released between 2003 and 2004, consisted of nearly raw data. Version 2.1 was an edited version that removed artifacts but left large voids. In 2013, NASA released Version 3, also called SRTM Plus. This version used data from ASTER GDEM2 and USGS GMTED2010 to fill many of the voids. A significant milestone occurred in 2014 with the release of SRTM-GL1. This was a global 1-arcsecond release with a 30-meter resolution. It provided the highest possible resolution of global topographic data derived from the mission.

The impact of the SRTM data is visible in its widespread use. By June 2011, there were 750,000 confirmed users of the dataset. People from 221 different countries have accessed this information. The data is essential for many scientific fields, including hydrology and geography. For example, the USGS HydroSHEDS dataset was created specifically for studying water flow and drainage. Other researchers use the data to create cleaned terrain models. In Australia, scientists released a version that removes features like trees and buildings. This allows for a clearer view of the actual ground elevation. The mission continues to serve as a foundation for global mapping technology.