As we all know,different regions observed at different observation points according to the latitude.For example,Polaris cannot be viewed in the southern hemisphere while the Crux couldn't be observed in high latitudes in the northern hemisphere as well.Telescopes in different latitude are needed to cover the while sky.
In addition,a main point in radio band is the poor resolution attributed to the extreme long wavelength.An efficient and inexpensive method to improving observation effect is establishing telescope array.Radio telescopes around the world could take advantage of the length of the earth so as to reach the target.
研究生是直升的,英语不太好,还请楼主见谅……= =