To accomplish its task, EGRET was equipped with a spark chamber, calorimeter, and plastic scintillator anti-coincidence dome. The spark chamber was used to induce a process called electron-positron pair production as a gamma ray entered the telescope. The calorimeter on the telescope was then used to record the data from the electron or positron. To reject other energy rays that would skew the data, scientists covered the telescope with a plastic scintillator anti-coincidence dome. The dome acted as a shield for the telescope and blocked out any unwanted energy rays.