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December 18, 2017 - Discovered and Photographed by Cassini

Discovered and Photographed by Cassini  Giovanni Cassini was an astronomer at the Panzano Observatory in Bologna from 1648 to 1669, and in 1671 he became director of the Paris Observatory. A talented observer, Cassini made numerous contributions to the understanding of the solar system. He made direct measurements of the distance to Mars, co-discovered Jupiter’s Great Red Spot, was the first to see the gap in Saturn’s rings that now bears his name, and discovered four of Saturn’s moons. One of those moons, Rhea, he discovered 345 years ago this week. Rhea is an icy moon covered with large and small impact craters. This enhanced-color image, take by the (appropriately named) Cassini spacecraft in early 2015, is one of the highest resolution color views of the Rhea ever obtained.

Image credit: NASA / JPL-Caltech / Space Science Institute

Weekly Calendar

December 18-24, 2017

Holidays - Sky Events - Space History


Moon phase Monday 18

New Moon 1:31 AM ET
Moon at apogee

1999: Terra spacecraft launched

Moon phase Tuesday 19

1960: MR-1A launched, first Mercury capsule
1961: CNES founded
1966: United Nations approves Outer Space Treaty
1999: STS-103 Discovery launched
2012: Soyuz TMA-07M launched carrying ISS Expedition 34/35 crew
2013: Gaia spacecraft launched

Moon phase Wednesday 20

1904: Mount Wilson Solar Observatory founded
1972: Final M2-F3 lifting body flight
1978: Venera 12 lander lands on Venus
2009Soyuz TMA-17 launched carrying ISS Expedition 22/23 crew

Moon phase Thursday 21

Solstice 11:28 AM ET
Ceres appears stationary
Saturn in conjunction with Sun

1968: Apollo 8 launched
: Vega 2 launched
: Cosmonauts Titov and Manarov return after spending one year aboard Mir space station
2011Soyuz TMA-03M launched carrying ISS Expedition 30/31 crew
2015: SpaceX Falcon 9 makes first powered vertical landing of orbital booster

Moon phase Friday 22

Mercury appears stationary
Ursid meteor shower

1966: Luna 13 launched
1966: First glide test of the HL-10 lifting body

Moon phase Saturday 23

Ursid meteor shower

1672: Giovanni Cassini discovers Saturn’s moon Rhea

Moon phase Sunday 24

Neptune 1.4° north of Moon
Pallas appears stationary

1968: Apollo 8 enters lunar orbit
1978: Venera 11 lands on Venus
1979: European Space Agency launches first Ariane rocket

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