Despite a large number of innovations and developments in ground-based telescopes such as refractive and reflective telescopes, space telescopes are beyond comparison. They are the best options when we wish to look into Space – and this is because they avoid blurriness because of the space atmosphere. One such way is to use a Cosmic Background Explorer (COBE) to detect radiations is Space.
So far, NASA has been able to construct four highly functioning telescopes that orbit in Space. These include Hubble Space Telescope, Compton Gamma Ray Telescope, Chandra X-ray Observatory, and the Spitzer Space Telescope.
However, there are others such as Webb Space Telescope that is expected to come in the near future.
Challenges of Using Space Telescopes
Although Space telescopes are a great plus when it comes to astronomy, but they have some drawbacks that limit the usage.
- Their building and launching are expensive than ground-based Telescopes as they have to stay in the Space.
- Their size has to be smaller than ground-based observatories as they are launched outside the Earth through a spacecraft.
- Since they are sent to Space and keep orbiting – their maintenance or repair is nearly impossible.
- It is essential to keep their angles and dimension within appropriate limits while sending them into Outer Space.
- They are like a one-time thing; once they are in Space, they break down with the wear and tear of Time and Space.
- Once they have gone, we cannot retrieve them.
- But if we think deeply into it – astronomers are finally able to view the universe in a much better way than before by placing space telescopes in orbit above the Earth. Thus, they are providing humanity the best image and conditions of the exoplanets out there.
The Cosmic Background Explorer (COBE)
The COBE launched in 1989 initially. The primary purpose of COBE was to study the infrared and microwave radiations that were very faint, and we could not detect them from the ground.
However, the radiations we obtained from COBE were termed as Cosmic Background Radiations. According to some theories from the scientists, the radiation is a result of the Big Bang – the reaction that caused a massive star to break up into different parts, which later cooled down to form planets.
Type of Telescope
In Simpler words, we consider Cosmic Background Explorer as a “Detector” type telescope that detected various radiations in Space and around exoplanets.
Light Collecting Instruments in COBE
In COBE, microwave receivers were installed as integral parts of the observatory, which received and detected the different forms of electromagnetic radiations of different spectra.
Observed Radiation Ranges
Although the radiations in Space vary widely, the Cosmic Background Explorer can only detect microwave and infrared radiation. Thus, we can say it is sensitive to only these types of radiations.
Distance from the Earth
COBE orbits some 880 kilometers about the surface of the Earth in the atmosphere.
Instrumentation of COBE Space Telescope
The main three instruments of the Cosmic Background Explorer included the following:
- Far Infrared Absolute Spectrophotometer (FIRAS)
- Differential Microwave Radiometer (DMR)
- Diffuse Infrared Background Experiment (DIRBE)
Far Infrared Absolute Spectrophotometer
The acronym for FIRAS is a spectrophotometer that detects infrared radiations into Space and records it in the form of a graph or chart with the recordable devices. The whole instrument was surrounded by liquid helium to keep it cool at a temperature of around 1.5 K. This was to ensure that the instrument emitted radiations of much lesser intensity than the Cosmic Microwave Background Radiations.
Differential Microwave Radiometer
It is also known as the DMR. The main purpose of this radiometer is to map out the microwave radiations present in the Space. Its unique design helped it to measure the radiation at three different frequencies – mainly 31.4, 53, and 90 GHz). There were in total of two receivers for each frequency range. The shortest frequency receivers were kept at room temperature, whereas the other two were cooled down to 140 Kelvin temperature. This helped to increase sensitivity.
Diffuse Infrared Background Experiment
In astronomy, we call and write it as DIRBE. It did fantastic work to detect the cosmic radiation spectrum. It was a small telescope to reject the stray light or the lights that did not belong to the infrared or microwave spectrum.
Launching of the Cosmic Background Explorer (COBE)
A Delta 2 rocket launched the explorer directly into orbit – around 900 kilometers above the Earth. The trajectory is synchronous with the Sun and is at an inclination of 99 degrees to the Earth’s equator.
The orientation of the Spacecraft
The Orientation of the spacecraft was such that it points away from the Earth and perpendicular to the Sun. This orientation prevented it from being illuminated by the direct radiation from the Sun.
Additional Instrument of the COBE
In addition to the main instruments, COBE had solar panels that collected light from the Sun and provided energy. It used a funnel-shaped object on top of it to direct sunlight on a particular part of the satellite to keep the sensitive part from heating up.
The liquid hydrogen within the COBE assembly kept the telescope cool. Otherwise, it would give radiations of its own that could interfere with the radiations from external sources – thereby altering the results and increasing the infrared signal that was obtained originally.
If we compare COBE with the telescopes of today, we will find out that it is not very sensitive. However, it helped scientists confirm the Big Bang theory and provided enough information to create different sky maps in IR and microwave radiation regions. It completed its mission in 1993.
The COBE is an explorer and not a typical telescope. However, it fulfilled the purpose that it was launched for – that is, to detect the Cosmic Background radiations and confirm the Big Bang Theory’s authenticity. The results of COBE clearly indicate that the Big Bang theory is valid. Thus, we can say that the Cosmic Background Explorer mission has been a complete success. It further opened ways for us to observe the deep sky better as it provided us what to expect in outer Space.