Centre for Basic Space Science (CBSS)

Introduction
Nigeria is one of the few countries in sub-saharan Africa where modern astronomy is taught at both undergraduate and postgraduate levels. The astronomical community has been involved in main stream research activities in modern astronomy and astrophysics. Between 1980 – 2007 Astronomers in Nigeria have made significant progress in the area of theoretical High Energy Astronomy. In observational astronomy, there are astronomers who have been trained in astronomical observations at different observatories including Hartebesthoek Radio Observatory (HartRAO) South Africa, National Astronomical Observatory Japan (NAOJ) among others.

It is important to note that the Nigerian Space policy statement emphasizes that Nigeria will vigorously pursue the attainment of space capabilities as an essential tool for its socio-economic development and enhancement of the quality of life for its people. The National Space Research and Development Agency, (NASRDA) – the Agency responsible for the actualization of this lofty idea hopes to achieve this through research, rigorous education, engineering development, design and manufacture of appropriate hardware and software in space technology and antennas for scientific research and applications. And it is for these reasons that CBSS, an activity centre of the (NASRDA) has embarked on this ambitious project of setting up a 25m Radio Telescope in Nigeria for frontline space research.

The electromagnetic spectrum
The electromagnetic spectrum is made up of light of many different wavelengths. Most wavelengths are invisible to us. In fact, our eyes can only detect the small portion of the spectrum between 400 and 700 nanometres. We call these wavelengths "visible light."

Radio Telescope
What is a radio telescope? A radio telescope is a device for measuring radio frequency energy from the cosmos. Radio telescopes come in hundreds of configurations. For illustrative purposes, we first describe a very generalized type called the total power radio telescope shown in diagrammatic form below. It collects radio waves from very distant objects in space such as planets, stars, galaxies, etc. The waves collected by the telescope are then processed and interpreted by means of receivers and computers. It has other wider applications in space science such as tracking and collecting data from satellites and space probes, monitoring our space satellites and satellite communication. Radio telescope has a wider window for observation in electromagnetic spectrum than optical telescope.

A professional radio telescope is an astronomical instrument consisting of a radio receiver and an antenna system that is used to detect radio-frequency radiation emitted by extraterrestrial sources.

Radio telescopes are generally reflecting telescopes. A huge parabolic dish collects incoming radio waves and focuses them at the receiver, which is mounted at the focal point of the dish. Radio dishes are big, but some radio waves are so long that a single dish is too small to collect them. Astronomers tackle this problem by building antenna arrays, like the one shown in the picture above in which computers allow many individual dishes to work together as one. Because radio wavelengths are much longer than those of visible light, radio telescopes must be very large in order to attain the resolution of optical telescopes or better.
As indicated above, the most familiar type of radio telescope is the radio reflector consisting of a parabolic antenna -- the so-called dish -- which operates in the same manner as a television-satellite receiving antenna to focus the incoming radiation onto a small antenna referred to as the feed, a term that originated with antennas used for radar transmissions. In a radio telescope the feed is typically a waveguide horn and is connected to a sensitive radio receiver. Cryogenically cooled solid-state amplifiers with very low internal noise are used to obtain the best possible sensitivity.
Observing times up to many hours are expended and sophisticated signal-processing techniques are used to detect astronomical radio signals that are as much as one million times weaker than the noise generated in the receiver. Signal-processing and analysis are usually done in a digital computer. Although some of the computations may be carried out by microcomputers (i.e., those of the personal-computer class), other tasks require large, high-speed machines to translate the raw data into a form useful to the radio astronomer.
The performance of a radio telescope is limited by various factors: the accuracy of a reflecting surface that may depart from the ideal shape because of manufacturing irregularities; the effect of wind load; thermal deformations that cause differential expansion and contraction; and deflections due to changes in gravitational forces as the antenna is pointed to different parts of the sky. Departures from a perfect parabolic surface become important when they are a few percent or more of the wavelength of operation. Since small structures can be built with greater precision than larger ones, radio telescopes designed for operation at millimetre wavelength are typically only a few tens of metres across, whereas those designed for operation at centimetre wavelengths range up to 100 metres in diameter.
Some radio telescopes, particularly those designed for operation at very short wavelengths, are placed in protective radomes that can nearly eliminate the effect of both wind loading and temperature differences throughout the structure. Special materials that exhibit very low absorption and reflection of radio waves have been developed for such structures, but the cost of enclosing a large antenna in a suitable temperature-controlled radome may be almost as much as the cost of the movable antenna itself.
Radio telescopes are used to measure broad-bandwidth continuum radiation as well as spectroscopic features due to atomic and molecular lines found in the radio spectrum of astronomical objects. In early radio telescopes, spectroscopic observations were made by tuning a receiver across a sufficiently large frequency range to cover the various frequencies of interest. This procedure, however, was extremely time-consuming and greatly restricted observations. Modern radio telescopes observe simultaneously at a large number of frequencies by dividing the signals up into as many as several thousand separate frequency channels that may range over a total bandwidth of tens to hundreds of megahertz.

What do radio telescopes do?
Radio telescopes are constantly evolving, but the basic principles remin the same A telescope collects and concentrates electromagnetic radiation
The bigger the parabolic reflector or dish, the more EM radiation it can collect. The more radiation it collects, the fainter the galactic or extragalactic objects it allows us to see. A radio telescope basically focuses EM radiation and creates a radio image
To create a clear image, radio telescope dishes or mirrors bring EM radiation to meet at a single point, the focal point. If the EM “rays” don’t meet at the same point, the image is blurry. The shape of the dish is designed to make EM radiation meet at a single focal point.

The image is recorded
Once an image forms, it must be recorded for research. Originally, people drew the images they saw through optical telescopes. Later, photography allowed people to take pictures of the image on film. Today, astronomers use charge coupled devices (CCDs), electronic light-sensing devices like those in digital cameras, to record images

What can I do with a radio telescope?
There are few things that come to mind when asked this. Of course, radio astronomy is like so many other fields of knowledge...the more you know and do in the field, the more you find yourself stumbling upon new and intriguing avenues of discovery. But the following are just a few examples taken at random:

Study Jupiter's noise storms.
Record flares and predict geomagnetic activity.
Detect a pulsar using DSP (digital signal processing).
Detect stronger radio sources.
Look for HEPs (high energy pulses} from the galactic centre.
Search for radio correlations to gamma ray bursts.
Study ionospheric scintillation and refraction.
Detect meteors invisible to the eye.
Develop a long base line interferometer.
Learn radio technology.
Learn astronomy.

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What makes a good radio telescope?
A radio telescope is judged on the following qualities:
Its sensitivity and resolving power
Except in the case of solar telescopes, magnification or gain is the least important element of a research radio telescope. Gain depends on focal length. As the gain increases, the telescope focuses on a smaller piece of the sky. Most research radio telescopes are designed to operate at the smallest gain possible, to examine a larger piece of sky. The distance and details they see depends more on their radiation-collecting ability and resolution than their gain. Solar telescopes, however, can rely on gain because they don't have to look deep into space, see much of the sky, or gather much radiation to clearly view the Sun.
Instrument quality
A modern research radio telescope is only as good as the filters and receivers and other instruments that record and analyze the electromagnetic radiation that it captures.
Its radiation-collecting ability
Faint objects are hard to see. Objects appear faint because they are either far away, and/or because they glow dimly. The more electromagnetic (EM) radiation a telescope can collect, the better it can see faint objects. Large dishes and arrays allow radio telescopes to collect more radiation.
Its resolution
Resolution is the ability to see detail in an object. A telescope with high (good) resolution will be able to see two point radio sources as being separate from one another. A radio telescope with low resolution will blur the two points together into a single point of light.