Man’s endless curiosity has been the driving force behind his quest for knowledge. And things beyond human purview have intrigued man from the beginning of life. Thus arose the desire to look closer into outer space and all that it held. Astrophotography helped in discovering astronomical objects like the planets and stars and galaxies and the sun.
In the mid-nineteenth century, Louis Jacques Mande Daguerre started the process of photography with his invention of the daguerreotype process. In 1840, the American physician and scientist, John William Draper, was the first to capture the image of the moon with his reflecting telescope. This was a daguerreotype image and this process became the dominant process used in astrophotography. Further improvements were made enabling the photography of the sun during an eclipse. Later, the first picture of the star, Vega, was taken with a Great refractor in the Harvard College observatory in 1850.
In the late nineteenth century there was a major breakthrough in astrophotography. This was the invention of dry plate photography by Sir William Huggins. A little later, Henry Draper was able to photograph the Orion nebula with the help of a refracting telescope.
Astrophotography has come a long way since then with the onset of computers and computer-controlled telescopes. Digital data is now routinely collected through ‘Remote Telescopes’. This is then made available to the general public through internet sites like the Bareket observatory.
Satellite photography has taken the viewing of outer space into an altogether different level. Now satellites going around the earth are used to take pictures not only of outer space, but also vivid images of the earth itself. These images can be highly complex and minutely detailed. They can capture a portion of the earth through composite images or zero in and display a very small portion of a city and even zoom in on an individual home.
There are innumerable applications and uses of satellite imaging. They are not only used in scientific endeavors, but also in everyday life as in agriculture and forestry, meteorology and biodiversity conservation. More importantly it is heavily used in national defense and for gathering intelligence and for applications in warfare. Some of the valuable uses in everyday life are the enabling of the forest ranger to detect forest fires. Seismology and oceanography are largely helped by satellite imagery. Earthquakes, volcanoes and tsunamis can be predicted when changes to land formations or the water depth are perceived through these images.
Remote sensing through satellite photography uses four types of resolution. Spacial Resolution is where the land surface area is measured in pixels. Spectral Resolution uses electromagnetic spectrum measurement of wavelength intervals. Images through Temporal Resolution depend on measuring through the amount of time passing between the collections of images of any given surface. Radiometric Resolution, on the other hand, uses the sensor’s bit depth on the levels of gray scales. Thus it is expressed in 8-bit, 11-bit, 12-bit or 16-bits.
GSD or Grand Sample Distance is an example of geometric resolution. Here it combines optical and systemic noise sources to view an object on land in a single pixel.
Satellite photography is aided by aerial photography quite often. The advantage of aerial photography is that it has a higher resolution. So when the two technologies are combined, it gives a much truer picture. While aerial photography uses cameras, satellites mainly have electronic scanners which record images in digital form. The National Aeronautic and Space Administration (NASA) is one of the major organizations which use both technologies to advantage. Astrophotography helps with their space programs and all the spacecraft launched by them have used it extensively.
Apart from mapping the earth, astronomers enjoy mapping the sky. Astrographs are used in astronomy in order to map the vast portion of the sky and marking the positions of different objects in it. Stellar classifications also use astrographs using two cameras. This helps with measuring the distance of stars based on color and brightness of the images. It also helps with the discovery of meteors, comets, novae and asteroids.
Thus astrophotography and satellite photography have played an important role in the furtherance of science in the modern world. But as seen above, applications using these technologies touch our lives every day.