The hemispheric view of Venus that we see in the accompanying picture was first published by NASA on June 4, 1998. A composite image colour-coded to represent elevation and processed to emphasise even small features, it is the result of a decade of radar investigations that culminated in the Magellan mission.
Magellan was the first deep space probe launched by the U.S. in over 10 years. Much of the basic system was assembled using spare parts left over from previous missions, including that of Voyager, Galileo and
Mariner 9. Originally scheduled for launch in 1988, the mission was pushed by at least a year owing to the Space Shuttle Challenger disaster in 1986.
Launched by a space shuttle
Space Shuttle Atlantis (STS-30R) was launched on May 4, 1989. Magellan was released from the cargo bay of the Space Shuttle Atlantis by the crew of STS-30R on May 5. There was something to celebrate right at the start as Magellan became the first planetary spacecraft launched from a space shuttle.
Three trajectory corrections later, Magellan arrived in Venus orbit on August 10, 1990. Following a 15-hour communication outage and another 17-hour interruption on two separate occasions, the ground team sent new software to reset the system to tackle such issues.
Designed to map 70% of the Venusian surface down to a resolution of 120-300 m, Magellan went about its task and started returning high-quality radar images from September 15, 1990. These showed volcanism, tectonic movement and kilometres of lava channels, among others.
Radar mapping
By May 15, 1991, Magellan completed its first 243-day cycle of radar mapping the Venusian surface. This included 1,200 gigabits of data – more data than all previous NASA planetary missions combined at the time – and provided clear views of over four-fifths of the surface of Venus.
Having already achieved more than what it set out to, Magellan completed five more cycles. While the second and third served as additional mapping cycles and increased the coverage to 96% and then 98% of the Venusian surface, the remaining three cycles were focussed on obtaining other data.
Surface features persist
In May 1993, NASA lowered Magellan into the outermost regions of the Venusian atmosphere and then circularised its orbit using a then-untried method called aerobraking. On October 13, 1994, Magellan was commanded to gather aerodynamic data by plunging into the Venusian atmosphere. That marked the end of a highly successful mission, as the spacecraft burnt up in the atmosphere of Venus.
The mission was able to show that over 85% of the Venusian surface is covered with volcanic flows; that continental drift isn’t evident in Venus; and that surface features can stay on for hundreds of millions of years. The last of these is due to the complete absence of water, which makes erosion an extremely slow process despite Venus’ high surface temperatures and pressures. And, of course, as mentioned right at the start, Magellan contributed immensely in providing the highest-resolution radar maps of Venus so far.
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Magellan arrived when Magellan set sail…
Ferdinand Magellan.
You might have figured out that the Magellan mission is named after Portuguese explorer Ferdinand Magellan.
It is interesting to note that August 10, the date on which the space probe arrived in Venus’ orbit in 1990, is also the date on which Magellan, the explorer, set out from Spain on his famous voyage.
On August 10, 1519, Magellan began his exploration with a fleet of five ships and an overall crew of 270.
The Strait of Magellan is named after him and he is also the first European to cross the Pacific Ocean.
Only 18 of the original crew of 270 and one of the five ships returned home three years later. Magellan himself wasn’t one of them as he had lost his life in a battle during the expedition.
