Stargazing: Orbiting Solar Observatory 7 Launch Anniversary

At the center of our solar system glows a huge, hot ball of hydrogen and helium gases. Nuclear fusion reactions generate the Sun’s massive heat. Without the energy and light it radiates, life on Earth would not exist as we know it. From times of antiquity, the Sun has been the source of veneration, poetry, and curiosity.

From 1962–1975, NASA launched satellites to study the Sun, creating the Orbiting Solar Observatory (OSO) series. OSO 7 was launched on Sept. 29, 1971. A mishap at launch nearly stopped the mission before it fully began. The loss of hydraulic pressure in a guidance control system meant the spacecraft was tumbling out of position. It had only 12 hours of battery power to get the direction of the transmitting antenna corrected. With an hour of battery left, orientation control was recovered, and OSO 7 went on to achieve the first optical observation of a coronal mass ejection (CME).

A CME is when the Sun expels a sudden and substantial amount of plasma from its corona, the outermost layer of the Sun’s atmosphere. If the ejection is massive enough, it can continue into interplanetary space and collide with Earth’s magnetic field. These strong solar influences, geomagnetic storms, are known as “space weather” and can affect astronauts in space as well as wreak havoc on power grids and communication systems on Earth.