Astronomical satellites are not simply a product of modern thinking, but its roots lie in the human psychology. It’s an inherent curiosity to find what lies beyond the sky? The same quest to explore our surroundings has always motivated the scientists to develop means to see farther than what normally our eyes are capable of. From ancient times, people have tried to derive logic in the solar events whether it is the rotation of the earth or the patterns in the night sky.

The advancement in technology and reasoning based on scientific theories extended our understanding of the universe. The researchers like Galileo had used rigorous calculations and telescopic methods to derive the solar system structure and the location of the planets like Venus in the space. Finally, with the launch of first satellite Sputnik1 by the Soviet Union in the earth’s orbit a new scope of study and research opened up for the scientists. The idea was to use a satellites for space observation as an eye in the sky which can produce real-time images of the planetary movements in the space. Astronomical satellites were designed specifically for observing planets and taking the pictures to understand their behaviour and predict the future astronomical events precisely. It defeated the prime hindrance of observing the planets from the earth which was the dense atmospheric layers near the earth surface filled with dust and pollution.

Launched on 25 January 1983, Infrared Astronomical Satellite (IRAS) was the first astronomical satellite to carry out a survey of the night sky. It was a joint mission of NASA, NIVR, Netherland and SERC, UK. The satellite used infrared rays to capture the stars and planets. The discoveries with the first telescope mission include the galaxy core and six numbers of new comets. It also corroborated the planetary systems around the other stars citing the solid material found around the stars Vega and Fomalhaut as evidence. It lasted for ten months, and after that, it stopped functioning as the cryogen had exhausted. Since then, countries through their individual space observation missions or collective missions of two or more nations have sent astronomical satellites to mark their presence and contributed to the space observation and mapping programs significantly.

Photo creation methods

An Astronomical satellite is designed and placed in the earth’s orbit to continuously monitor the astronomical events or in some cases a specific planet. The images from Astronomical satellites like Hubble telescope and other such satellites are not camera images. The satellite employs electromagnetic spectrum analysis method for wavelength regions such as Ultra violet, X-ray, visible spectrum, microwaves and gamma rays to take images of the solar objects. A picture taken from Hubble telescope of distant galaxies is shown below.

The Hubble Space Telescope took this picture of the Tadpole Galaxy and its tail of large, bright blue star clusters. Credits: NASA

Applications

Astronomical satellites are not the same as space exploration satellites as they only observe the space from the earth orbits, unlike exploration satellites which go for rigorous investigation. They have various applications ranging from observational to forecast related cosmological events. Below are some of the main key functions of the astronomical satellites.

A) Star Mapping: They are used for observing the earth or any other star and can, therefore, be used for mapping the stars in the cosmos.
B) Observe Black Holes and the Quasars formations: They are used to study and research the various stages of black hole formation or the other significant solar activities.
C) Taking Photos and analysing them: Taking photos for comparison of size and shapes before and after an astronomical event and highlighting the changes in the locations of the planets and galaxies is one of the main objectives of using them.
D) Forecasting through observation: The precise calculations on the basis of exact locations of the planets can predict the cosmological events such as a comet collision or meteors shower. These predictions help us to be prepared for any chain effects on the earth due to the events in space.

They are classified according to the wavelength of the rays they use for observation. Satellite Groups are there as per the different wavelength rays that they employ for picturing the planets. The wave-groups are classified as gamma-ray, X-ray, ultraviolet, visible, infrared microwave, and radio. There are telescopes which have a wide frequency range of operation and come under all the corresponding ray-groups. For example 3rd high energy Astronomy Observatory (Head 3) falls within both gamma ray and X-ray. To specify the orbit of the satellite the maximum and minimum altitude values are sufficient.

They have been instrumental in studying the mysteries related to our cosmos such as the various states of a star i.e. red giant, supernova, black hole among many others. The precise mapping of star’s surface, their patterns, and 3D location tracking have revealed various new concepts in cosmology and corroborated many old theories.

Usefulness of satellite images of the earth

The scientific understanding of earth surface and changes after natural disasters are studied through the satellite photos of the earth. For example, after Tsunami a big chunk of the landmass got submerged into the sea, and also some island coordinates keep changing continuously from threats such as global warming. Hence the astronomical satellites not only provide information regarding outer universe but also plays a vital role in understanding the phenomenon that affects the earth. Earth mapping using satellites can enhance our understanding of the industrial side effects on our planet and warn us for the drastic rise in sea levels and submerge land masses due to the burning of fossil fuels. Therefore, if utilized efficiently, they can be of significant use in sustaining the balance of life on earth or may be on the other planets of the universe as well.