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October 24, 2011 - STEREO Transit

STEREO Transit A pair of Sun-watching satellites took to the skies five years ago this week in a bid to make the first regular stereo observations of our nearest star. The twin Solar TErrestrial RElations Observatory (STEREO) satellites were launched into a unique orbit that has one of them traveling ahead of Earth and the other behind. Eventually, as the distance between the two spacecraft gradually increased, they were so far apart that stereo imaging of the Sun was no longer possible. In February, 2011, they were on opposite sides of the Sun, allowing simultaneous observations of the entire Sun for the first time in history. In February, 2007, the STEREO-B spacecraft captured this image of the Moon crossing in front of the Sun; from the spacecraft’s position, the Moon was smaller than seen from Earth.

Image credit: NASA

Weekly Calendar

October 24-30, 2011

Holidays - Sky Events - Space History

Moon phase Monday 24

United Nations Day

1851: William Lassell discovers Uranus moons Umbriel & Ariel
1968: 199th and final X-15 flight
1998: Deep Space 1 launched
2001: Mars Odyssey arrives at Mars
2007: Chang'e-1 lunar spacecraft launched

Moon phase Tuesday 25

1671: Giovanni Cassini discovers Iapetus, moon of Saturn
1877: Henry Norris Russell born
1975: Venera 10 lands on Venus
2006: STEREO spacecraft launched

Moon phase Wednesday 26

New Moon 3:56 PM ET
Moon at perigee

1977: Fifth and final glide test of Space Shuttle Enterprise
2004: Cassini spacecraft completes first flyby of Titan

Moon phase Thursday 27

Mercury 0.2° north of Moon

1961: SA-1 launched, first Saturn rocket
2003: ISS Expedition 7 crew returns to Earth after 184 days in orbit

Moon phase Friday 28

Venus 1.8° north of Moon
Jupiter at opposition

1971: Britain launches its first satellite
1974: Luna 23 launched
2009: Ares I-X test flight

Moon phase Saturday 29

1964: First flight of Lunar Landing Research Vehicle
1987: Cosmos 1894 becomes 2,000th satellite
1991: Galileo flies past Gaspra
1998: STS-95 Discovery launched

Moon phase Sunday 30

1981: Venera 13 launched
1985: STS-61A Challenger launched
1997: First successful Ariane 5 rocket launched

Suggestions for new history dates or better links? Corrections for errors on this page? Please e-mail me.