Understanding Venus: An International Effort

Within five years of the dawn of the space age with Sputnik, the Mariner 2 fly-by (1962) and Venera-4 probe's entry (1967) into another atmosphere demonstrated that our nearest neighbor was a world very different from our own home planet. With regular launches from the Soviet Union in the early decades of exploration of Venus and missions launched by NASA, the knowledge about Venus grew significantly. It was only after the COSPAR general assembly held in Philadelphia in 1976 that collaboration began between US and USSR with exchange of data, leading to some small joint efforts with the Pioneer Venus Orbiter and Probe missions (1978-1983) followed by collaboration in planning and carrying out the VeGa mission in 1985 involving many countries. The nearly two-dozen missions flown to Venus have painted a puzzling picture of Venus. Presently JAXA's Akatsuki orbiter is collecting observations that are adding more questions about the planet. They can be summed up by perhaps just one question: why did Venus evolve so differently from Earth? What we have learnt from the many missions to Venus is that to understand Venus, we need to observe its surface, sample its deep atmosphere, explore its magnetosphere and ionosphere, infer the interior structure and monitor the deep, global cloud cover. Just like Earth is being observed by multiple spacecraft in different orbits, airplanes, ships, automated surface and ocean stations, observing Venus and its environment requires a combination of platforms. Single, focused missions are effective at tackling some of the questions about Venus, but the synergy of near simultaneous and long term monitoring of Venus is needed for a better understanding of the planet.The International space agencies and scientists have been considering various approaches to exploring Venus through small and large missions. The Venus Exploration Analysis Group (NASA) has developed a Venus Exploration Roadmap and a comprehensive list of goals, objectives and investigations (www.lpi.usra.edu/vexag). Venus science and questions for future missions have been periodically discussed by international Venus scientists at dedicated conferences. Following discussions at such meetings, the International Venus Exploring Working Group was formed during the 2012 general assembly in Mysore India to promote collaboration among the global Venus scientific community and coordination of efforts to explore Venus by the spacefaring nations, which worked so successfully for the VeGa, Venus Express and Akatsuki missions in particular. At present a collaborative effort limited to Roscosmos and NASA is being conducted by the Joint Science Definition Team assembled to study the implementation approach for Russia's Venera-D mission. It is recognized that Venera-D would represent an important piece of an international Venus exploration strategy. Leading up to and following this step an ongoing effort and additional missions by all space agencies are desirable to address the many un-answered questions. ESA is currently evaluating EnVision, a proposed mission that could carry a small contributed probe (such as those being studied by NASA), allowing for a coordinated and complementary international exploration plan. Such a plan is needed to maximise the returns from future Venus exploration.