SOLRAD I

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The SOLar RADiation satellite program (SOLRAD) was conceived in the late 1950s to study the Sun's effects on Earth, particularly during periods of heightened solar activity. It served as a cover project for the Project Dyno ELINT intelligence satellites with the covernames GRAB and POPPY operated by the U.S. Naval Research Laboratory (NRL). SOLRAD I was launched in June 1960, with ten additional SOLRADs to follow through 1976. The Thor Able rocket launched both Transit 2A and Solrad 1 at 1:54 a.m. EDT, as the first multiple payload launch into multiple orbits. Alternate names for SOLRAD I: GRAB 1, Sunray 1, SR 1, 00046, and Solrad 1.

INSTRUMENTS

The X-ray and Lyman-alpha experiment on board Solrad 1 was designed to provide long-term observations of ionizing radiation from the Sun by monitoring solar emission in soft X-rays (0.2-0.8 nm) and the hydrogen Lyman-alpha (105.0-135.0 nm). The principal investigator for the study was Dr. Herbert D. Friedman of the US Naval Research Laboratory. Measurements were made by two Lyman-alpha photometers and one X-ray photometer mounted on the satellite equator. Each Lyman-alpha detector was an ion chamber that contained nitric oxide gas. The X-ray photometer contained argon in its ion chamber. Data were collected between Jun 22 1960 and Nov 1 1960, during periods when the solar aspect angle was < 30°.

To eliminate responses of the X-ray photometer from Van Allen belt radiation (charged particles), a 2400-gauss permanent magnet was incorporated into the chamber design. This shielding magnet had a significant effect upon the rotational stability of the satellite and in part was responsible for a severe reduction in the amount but not the quality of data received.

Scientific accomplishments

As the world's first orbiting astronomical observatory, SOLRAD I determined that radio fade-outs were caused by solar X-ray emissions.

See also

  • X-ray astronomy

The content of this article was adapted and expanded from NASA's National Space Science Data Center: Solrad 1 1 (Public Domain)