Taking an image of Earth is no easy feat. Since NASA’s Explorer 6 satellite first took a blurry photo of our world back in 1959, methods and techniques to snap that perfect picture of our home have come on leaps and bounds, and the images often become very famous. In fact, 2002’s Blue Marble image was so popular that it eventually ended up as the default background on Apple’s iPhone.
The first Blue Marble image of the entire Earth – coined for apparently portraying our planet as a marble-like object – was taken by Apollo 17 astronauts in 1972 as they made their way back from a mission. The image they took 40 years ago was just a single snapshot, but today image-editing software such as Photoshop is used to enhance the picture, though great pains are gone to not to detract from the reality of the shot.
NASA’s most recent Earth portrait, dubbed ‘Blue Marble 2012’, was taken by an Earth observation satellite called Suomi NPP. For the satellite to shoot this image technicians on the ground had to take a picture of Earth six times as the satellite passed over one point, allowing them to combine several layers into one image.
There are five different instruments on board Suomi NPP, but by far the most important for this task is the Visible/Infrared Imager Radiometer Suite (VIIRS). This scanning radiometer can collect visible and infrared imagery of Earth in addition to measurements of the planet’s atmosphere, land mass and oceans.
The image was taken in January 2012 and compiled by NASA scientist Norman Kuring. The satellite flies in a polar orbit at a height of 824 kilometres (512 miles). However, the perspective of the image is from an altitude of 12,743 kilometres (7,918 miles) at a point ten degrees south latitude and 45 degrees east longitude, owing to the nature of the composite image.
For a scale representation of how far Suomi NPP is from the surface, imagine our planet as a basketball. The Earth has a diameter of about 12,756 kilometres (7,926 miles), while a basketball has a diameter of 25 centimetres (ten inches). If you hold the basketball 1.5 centimetres (half an inch) from your face, that’s how close Suomi NPP is to Earth. The width of each section of Earth the VIIRS images as it flies over is about 3,001 kilometres (1,865 miles). In comparison, the Apollo 17 astronauts who captured the first Blue Marble were about 76 centimetres (30 inches) away from the basketball (45,000 kilometres/ 28,000 miles from Earth).