Venus is the best mapped planet in the solar system. Thanks to the Magellan Mission more than 98% of the planet is mapped with great detail.

(Venus global view)

(Magellan at Kennedy Space Center)

(Magellan Being Deployed from the Space Shuttle)

Why isn't Earth better mapped than Venus?

• Because Venus doesn't have water anymore and is easier to identify the relief.
• 70% of the Earth is covered with water what makes the ocean depths very hard to map with precision.

(Volcano Sapas Mons, about 400 kilometers (248 miles) across and 1.5 kilometer (0.9 mile) high)

Mission Summary

The name:
The Magellan spacecraft was named after the sixteenth-century Portuguese explorer whose expedition first circumnavigated the Earth, Fernão de Magalhães.

Tasks:
Map Venus collecting radar images with approximately 100m resolution.
Assess surface topography and electrical characteristics.
Measure Venus' gravitational field.

Basically: To conduct the first global geological understanding of Venus, the planet most like Earth in our solar system.

Some dates:

04 May 1989 - Launch
10 Aug 1990 - Venus orbit insertion and spacecraft checkout
15 Sep 1990 - Cycle 1: Radar mapping (left-looking)
15 May 1991 - Cycle 2: Radar mapping (right-looking)
15 Jan 1992 - Cycle 3: Radar mapping (left-looking)
14 Sep 1992 - Cycle 4: Gravity data acquisition
03 Aug 1993 - Cycle 5: Gravity data acquisition
12 Oct 1994 - Termination experiment - loss of signal
13 Oct 1994 - Presumed loss of spacecraft

(Magellan Combined Radar & Altimetry Image of Three Volcanos)

See you tomorrow for more “Useless information”
RMach

Sources:
http://www2.jpl.nasa.gov/magellan/
http://nssdc.gsfc.nasa.gov/planetary/magellan.html
Debra Rosenberg. 1993. «The volcanoes of Venus». Technology Reviews 96: 15-16