While radio waves, near-infrared (near-IR), and visible light are observable from surface of the Earth, we need to introduce tools into space to observe other frequencies of the EM-band.This section will introduce:
In order to see the small window of the near-IR spectrum from the ground, some novel approaches have been designed and implemented. Viewing of the near-IR is possible only by:
To view the residual IR spectrum, high altitude observatories – or orbiting satellites – are required. Another method is to observe from Antarctica – if you like the cold!
There are two in-flight observatories:
In addition, the following observatories are (and were) in orbit around the Earth:
This high-energy portion of the EM-band is only visible from space. Between 1949 to 1962, sounding rockets traveling up to 100 km above the surface would carry Geiger counters to measure X-ray emission. A sounding rocket is nothing more than a standard rocket with the Geiger counter and other related electronics housed in within the nose.
By 1970, several orbiting X-ray observatories would begin capturing valuable data. These include the following observatories:
Objects observed by X-ray are (but not limited to) supernovaremnants, accretion disks, pulsars, and black holes.
The ultraviolet (UV) region of the EM-band allows the study of very hot, young stars. Additionally, populations of young, hot stars within the disks of spiral galaxies are within easy view of a UV telescope. This also requires satellite observatories. Here is a list of UV observatories:
Gamma rays are the highest energy radiation resulting in extremely short wavelengths. Sources of gamma rays are supernovas, neutronstars, intense gravity regions and active galaxies (galaxies with a large and active black hole at the center). Here is a list of some gamma ray satellites: