Great Space Observatories – NASA’s Chandra X-ray Observatory

Space Observatory is a type of space telescope that is located in outer space to observe the far off planets, galaxies, and other celestial and astronomical objects. The Space Telescopes avoid interference with ultraviolet (UV) frequencies, X-rays, and gamma rays. Moreover, they encounter scintillation (distortion) of electromagnetic radiation signals and light pollution to a lesser, and thus controllable extent. The Great Space Observatories are an example to the space observatories.

Great Space Observatories

NASA has a series of Great Space Observatories that are four in number. They are very powerful, robust, and space-based astronomical Telescopes that launched periodically from 1990 to 2003. However, each one of the great observatories detects different celestial objects in other areas of the electromagnetic spectrum. At present, two of these are still operational.

The 4 Great Space Observatories of NASA

  • Hubble Space Telescope (HST)
  • Compton Gamma Rays Observatory (CGRO)
  • Chandra X-ray Observatory (CXO)
  • Spitzer Space Telescope (SST)

The Chandra X-ray Observatory (CXO)

Let’s get to the bottom of Chandra X-ray Observatory, which NASA officially launched in the year 1999.

Principle Type of Telescope

The Chandra Observatory uses a reflector type telescope which employs curved mirrors to pass the light.

Light Collecting Instrument in CXO

Since the purpose of Space Observatory is to collect the light in a specific region of the EMR spectrum, therefore, it uses certain collectors. The light collector in Chandra X-ray Observatory is glass mirrors with a coating of 8 iridium on them. Hence, they are very sensitive to the X-rays.

Mirror Diameter of the Optics

The mirrors – used as optics in the telescope have a diameter of about 32.8 inches or 83.3 centimeters.

The distance of CXO from Earth

It orbits is an elliptical path that ranges from 16000 kilometers at the nearest point and 133,000 kilometers at the farthest point from the Earth.

Observation in Electromagnetic Region

It observes X-rays of the electromagnetic radiation and objects that appear within this range.

Significant Discoveries of Chandra Telescope

The CXO enabled the astronomers to study certain celestial events with greater precision, such as black holes, galaxies, and supernovae. In addition to this, it was the Chandra X-ray Telescope that discovered the presence of planet-forming discs around certain planets.

Black holes:

A black hole is a region of space between a galaxy, which contains a significant amount of mass gathered into a very small volume. A black hole’s gravitational field is so strong that not even the light can escape it.


Supernova is the death of a massive whose energy causes the gases to glow brightly for an extended period of time. Hence, it is a remnant of a massive star that remains as glowing and expanding gases.

History of Great Space Observatories

The concept of X-ray telescope first started back in the 1970s, when the USA launched its X-ray based telescope – Uhuru. Uhuru – launched in space spent three years in the sky scanning and looking for the sources of X-ray radiation that had fascinated the human for a long time. However, they were not able to detect them from the ground through their ground-based telescopes.

A Simple X-ray Telescope

It is a telescope that detects the high energy X-rays. The detection involves the X-rays to go through the telescope rather than bouncing off their surface. The mirrors are so arranged that the rays tend to skip across them.

After a long period of about 29 years, NASA was able to launch a better and more sophisticated version of the X-ray observatory. It took its name from the Nobel Prize-winning physicist Subrahmanyan Chandrasekhar.

Position of Chandra X-ray Telescope in the Space

Chandra is somewhere 200 times higher than Hubble Space Telescope. It detects even the faint sources of the X-ray radiations. The Chandra Space Telescope orbits in an elliptical or oval-shaped orbit. Owing to its ability to detect very faint radiations, it effectively studies different objects such as black holes, supernovae, and dark matter than emit X-rays.

Instrumentation of Chandra X-ray Observatory

Gyroscopes in Chandra X-ray Observatory

It uses mechanical gyroscopes for the purpose of sensing the direction of the telescope.

Navigation Systems

CXO has navigation systems, including an aspect camera, reaction wheels, and sensors for Earth and Sun.

Thrusters to Control Movement

It has two pairs of thrusters – one for the momentum and the other for movement.

Solar Panels

It has solar panels that have two rigid structures that are able to convert sunlight into electricity that, in turn, power the Telescope.

In addition to these, the CXO consists of the following critical integral instruments:

  • High Resolution Camera (HRC)
  • Advanced CCD Imaging Spectrometer (ACIS)
  • High Energy Transmission Grating Spectrometer (HETGS)
  • Low Energy Transmission Grating Spectrometer (LETGS)

Working of the Chandra X-ray Observatory

In Chandra Space Telescope, the mirrors lie at right angles to each other. Therefore, the X-rays tend to glance off their surfaces. X-rays are not easy to observe because of the high energy that they possess. Hence, an X-rays will penetrate the mirror of a conventional telescope instead of reflecting back.

Scientifically dividing the instruments, Chandra has four parts. Two of them provide facts about the position, energy, and arrival time of the X-rays. While the other two provide detailed information, particularly about the energy.

The Verdict about Great Space Observatories

All the Great Space Observatories including the Chandra X-ray Observatory has really helped the astronauts in finding out black holes, supernovae, and other celestial objects that are present within the electromagnetic radiation spectrum. However, the whole world is looking forward to launching the latest version of the telescope – the James Webb Telescope. It is quite impressive how the space observatories and telescopes have surpassed the presence of reflective and refractive telescopes. Although we come so far into the world of astronomy, there is still so much room for more discoveries and innovations.