Friendship 7 launch. Image: NASA.

Hermann Potonik, an Austrian Army officer writing under the pseudonym Hermann Noordung, described the benefits of telescopes in space in his seminal 1929 book Das Problem der Befahrung des Weltraums: der Raketen-Motor. The 1995 NASA-sponsored English translation of Noordungs work includes a brief section titled Unlimited Visibility. It describes how, beyond Earths blanket of air,

nothing weakens the luminosity of the stars; the fixed stars no longer flicker; and the blue of the sky no longer interferes with the observations. At any time, the same favorable, almost unlimited possibilities exist, [and] telescopes of any arbitrary size, even very large ones, could be used. . .

In 1946, Princeton University astronomer Lyman Spitzer also wrote about the possibilities of space-based astronomy, and it was with him that U.S. efforts to place telescopes into space originated. In 1960, NASA Goddard Space Flight Center (GSFC) in Greenbelt, Maryland, began work on the Orbiting Astronomical Observatory (OAO) series of space telescopes. The Grumman-built satellites would image the cosmos in wavelengths that could not easily penetrate Earths atmosphere and radio the images they captured to receiving stations on Earth.

Astronomers eagerly anticipated the OAOs, but for the general public NASA in 1960 was all about Project Mercury. The first manned Mercury orbital flight, designated MA-6, took place on Feb. 20, 1962. An Atlas rocket propelled astronaut John Glenn into space on board the Friendship 7spacecraft (image above). Glenn orbited Earth three times and splashed down safely in the Atlantic Ocean a little less than five hours after launch.

Faith 7 readies for launch. Image: NASA.

Three more astronauts rode Mercury capsules into orbit. The last Mercury mission, MA-9, saw Gordon Cooper orbit Earth 22.5 times in the Faith 7 capsule. His 34-hour mission spanned May 15-16, 1963.

If Windsor Sherman, an engineer at NASAs Langley Research Center (LaRC) in Hampton, Virginia, had had his way, then Mercury would have found a new role as part of NASAs space astronomy program. In a NASA Technical Note published a year and a half after MA-9, Sherman proposed that NASA modify manned Mercury capsules to serve as recoverable unmanned Earth-orbiting observatories.

Shermans Mercury-derived observatory would weigh more than the manned Mercury (2150 kilograms versus 1660 kilograms) and would require a higher orbit (at least 500 kilometers) to ensure that it would operate above Earths atmospheric airglow. The manned Mercurys Atlas booster would not be up to the task, so the recoverable observatory would launch on an Atlas with an Agena B upper stage. A similar rocket launched Ranger robot explorers to the moon.

Cutaway of Sherman's Mercury-derived recoverable observatory. Image: NASA.

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Mercury Space Observatory (1964)