The sun was just rising over Tibet when he spotted the Himalayas 350 km below his spacecraft. "The low sun angle gave tremendous relief to the mountains," he recalled. "Mt. Everest seemed to jump out at me! It was just one of those sights that will be forever burned into my brain." He captured the scene using a digital camera and emailed it to Earth -- a breathtaking postcard from the International Space Station (ISS).
Above: Astronaut Dan Bursch, a member of the Expedition 4 crew on the International Space Station, snapped this picture of Mt. Everest in late March 2002. [more]
It's the largest and clearest viewing port on the station. "Astronauts Tom Jones and Marsha Ivins said it was so clear on orbit they felt they could fall through it when they were looking at Earth," says Karen Scott of The Aerospace Corporation. "It was like it wasn't there."
Scott, who designed and tested the 20-inch wide window, explains that "an ideal window would be one that has no affect on light that passes through it. The Destiny window comes close." It transmits 98.5% of any visible light that hits it -- in pristine condition. "You could point a 16-inch telescope through the window and see no distortions."
Try that at home some night. Point a telescope through your living room window and note how the stars become colorful smears. The Destiny window is impressively better than ordinary glass.
The window is a favorite spot for astronauts, who often stop by with a camera for snapshots. Julie Robinson and her colleagues at the Johnson Space Center (JSC) Earth Science and Imaging Analysis Lab have analyzed thousands of those pictures and find them to be remarkably crisp. Some of the photos show details on Earth smaller than six meters -- about the size of a bus. (Even more amazing: Earth is moving in the window, and the astronauts use no tripods to steady their cameras. Constantly experimenting with camera settings and focus, the astronauts have developed their own methods to track objects on the ground without smearing the details.)
A crystal clear window, an astronaut, and a camera. "It's a powerful combination," says Greg Byrne, the manager of NASA's Crew Earth Observations Project at JSC. "Most satellites look straight down, but astronauts can look in any direction and notice what's unusual. They can snap photos between clouds, quickly swap between zoom and wide-angle lenses, and track curious features."
Earth scientists love it. "The Everest picture that Dan took with its low Sun angle, you could never get that from an Earth-observing satellite," says Robinson.
It's not unusual for astronauts to see what satellites do not. In 1994, for example, the crew of the space shuttle Columbia (STS-65) spotted a curious haze over the Caribbean Sea. It turned out to be a huge dust cloud from Africa, thousands of miles from the desert where it formed. Few scientists at the time had considered the possibility that such dust could drift all the way across the Atlantic Ocean. Down-looking satellites did not notice the thin clouds, yet astronauts looking at an angle saw them easily.
Now we know that dust clouds kicked up by wind storms in the Sahara desert carry microbes and allergens to the Americas every summer. The clouds sometimes cause red tides when they sprinkle mineral-laden dust over water; they can also damage coral reefs and sicken people who inhale the dust. Without astronauts taking pictures, scientists might not yet understand many outbreaks of allergies and red tides around the Caribbean.
Observing Earth from space is considered to be so important that astronauts are taught to do it long before their first mission. "Astronaut candidates learn about geology, environmental science, and deforestation," says Robinson. They also learn to use the equipment. The ISS carries video recorders, digital cameras, 35- and 70-mm film cameras, and lenses for each.
"We train the astronauts to look for the unusual -- for example, to look for sunglint," says Byrne. Photographs of bright sunlight reflected from ocean waters can reveal unexpected currents and island wakes. "The problem is that sunglint sweeps across the earth rapidly. They have only two or three seconds to take that photo."
Each week Byrne's team sends dozens of photo requests to the crew of the space station. They come from Earth scientists studying among other things coral reefs, urban growth, pollution, glaciers and river deltas. "The requests we send up require less than 30 minutes a day at the window," he says. "We receive thousands of photos from each mission -- more than we ask for. The majority is the astronaut just looking out the window. They see something appealing, they take a picture. Serendipitous discoveries happen that way."
Above: The Fangatau Atoll in French Polynesia photographed by an astronaut on the ISS (left, 5.3 meters resolution) and the Landsat 7 satellite (right, 30 meters resolution). Image courtesy Julie Robinson and Serge Andrefouet.
"We don't keep track of how much time astronauts spend Earth watching. But we've known since the days of Skylab that it's good for their mental health," adds Byrne. "Astronauts are cooped-up and busy -- looking out the window helps them relax."
It's hard to imagine a more delightful chore: floating at the window, the earth below, a camera poised for some new discovery. The worst-case scenario: a lovely picture. You can see the latest images from the International Space Station at NASA's Gateway to Astronaut Photography. Some of them will make you feel like floating ... right at your keyboard.
Editor's Note: As delightful as Earthgazing can be, astronauts can't spend too much time at the window. They have dozens of other experiments to tend and a station to build. That's why they are about to get some help from WORF, which stands for Window Observational Research Facility. Stay tuned to Science@NASA for a forthcoming story about WORF and what it can do.more information
NASA Human Spaceflight -- Learn more about the space station and its crew.
Gateway to Astronaut Photography -- (JSC) highly recommended.
Dan Bursch's 120-day report from space -- (Spaceflight.nasa.gov) Dan relates his experience spotting Mt. Everest from the ISS, and much more.
Astronaut Photography -- (EarthObservatory.nasa.gov) This feature story by Julie Robinson and Cindy Evans explains the many things Earth scientists learn from astronaut photography.
Destiny Lab Window: Optical Scientist Develops Window for Space Station (The Aerospace Corporation); Space Window Promises Best-Ever View of Earth (The Aerospace Corporation)
International Space Station Astronauts Set New Standard for Earth Photography -- a news release from the Johnson Space Center
Dust Links: Mobile Homes for Microbes (Science@NASA); Desert Dust Kills Florida Fish (Science@NASA)
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