Energetic Gamma Ray Experiment Telescope

EGRET was created for the purpose of detecting and collecting data on gamma rays ranging in energy level from 30 MeV to 30 GeV.

Scientists were able to map an entire sky of gamma rays with EGRET's results as well as find out interesting facts about Earth's Moon and the Sun.

[1] With the purpose of detecting individual gamma rays ranging from 30 MeV to 30 GeV, EGRET was equipped with a plastic scintillator anti-coincidence dome, spark chamber, and calorimeter.

Finally, to record the data from the electron or positron about the gamma ray, scientists equipped EGRET with a thallium-activated sodium iodide (NaI(Tl)) calorimeter at its base.

Since NASA scientists wanted only certain types of gamma rays to be processed and recorded, they set up EGRET with many systems of checks to filter out any unwanted information.

The most basic type of filter EGRET had was only allowing gamma rays entering the telescope from certain angles to be let into the spark chamber.

Once the gamma ray came in contact with a plate of metal, it initiated the process of electron-positron pair production and created an electron and positron.

NASA scientists also discovered that pulsars, which are “rotating neutron stars that emit a beam of electromagnetic radiation,” are the best sources of gamma rays.