自从美国的第一颗军用卫星“发现者”问世以来,科学家们有机会把科学仪器放在保密卫星上进行试验。除极少数外,这些试验实际上是未曾公布于众的。有许多试验,利用了大多数军用卫星采用的极地轨道之优点,而在六十年代中期,NASA的民用卫星一般是不能达到这种轨道的。携带的仪器曾用以绘制低高度粒子沉降辐射区域图和高高度核试验造成的人工辐射区域图,如同探测高层大气一样,探测了极光辐射。在第一次空间测地研究中曾使用西科尔卫星。试验仪器通常安装在阿金纳发动机的后部。 Since the advent of Discovery, America’s first military satellite, scientists have had the chance to experiment with science instruments on confidential satellites. Except for a very small number, these tests have not actually been publicly announced. There are many tests that take advantage of the polar orbits used by most military satellites, and in the mid-1960s NASA civilian satellites were generally unable to reach that orbit. The instruments carried were used to map low-level particle-fall radiation maps and maps of artificial radiation from high-level nuclear tests to detect auroral radiation as well as to the upper atmosphere. Sikors satellites were used in the first space geodesy. The test equipment is usually mounted on the rear of the Agine engine.