Solar Particle Alert Network

The Solar Particle Alert Network (SPAN) observatory, installed early in 1965, was critical to the safety of the Apollo astronauts. The study of the relationship between sunspot activity and intense solar flares would hopefully enable NASA to predict radiation hazards to astronauts on Apollo missions.

The three NASA multiple-telescope observatories (Boulder, USA; Canary Islands; and Carnarvon) were spaced at approximately 120° intervals around the world. They maintained continuous 24-hour monitoring of the sun with real-time reporting of flare activity, assisted by an observatory at Houston and four other observatories contracted to NASA. Several other observatories, associated with the Solar Forecast Centre, also contributed data to SPAN Control.

The SPAN site hosted several other facilities relatively unimportant to the main work of the station: a Riometer (Relative Ionospheric Opacity Meter), a Jupiter Monitor and, briefly, a Satellite Tracking Camera and a Mobile Laser Tracking System.

SPAN Site: Behind the Security Hut (on left) are the Riometer antenna back-plane masts; centre is SPAN building with Razdow telescope dome on the roof; and to the right back is the Radio Telescope radome just behind the white-light telescope dome. Far distant right is the R&RR VHF antenna. The Town of Carnarvon can be seen on the far horizon.

We are indebted to Jim Gregg, David Johns, and Hans Lemmens for their contributions to the SPAN sections.