Perigean spring tide Perigean spring tide A proxigean spring tide (also known as a perigean spring tide) is a tide that occurs three or four times per year when the Moon's perigee (its closest point to Earth during its 29.5-day elliptical orbit) coincides with a spring tide (when the Earth, Sun and Moon are nearly aligned every two weeks). This tide usually adds only a couple of inches to normal spring tides. The Moon's orbit around Earth is elliptical, which causes the Moon to be closer to Earth and farther away at different times. The Moon and the Sun are aligned every two
Campo Imperatore Near-Earth Object Survey Campo Imperatore Near-Earth Object Survey The CINEOS program (Campo Imperatore Near-Earth Object Survey), started in 2001, is dedicated to the discovery and follow-up of near-Earth objects (NEOs), namely asteroids and comets which periodically approach or intersect the Earth's orbit. In particular CINEOS is addressed to the discovery of Atens and Interior-Earth Objects (IEOs) by extending survey coverage at small solar elongations, and to the discovery of the other kind of NEOs by observing with longer exposures (up to a limiting magnitude of 21) in the opposition region. Between August 2001 and November 2004, CINEOS measured more than 61000 asteroid positions