A European-Japanese BepiColombo probe headed to Mercury zoomed past Venus on Tuesday (Aug 10), beaming back selfies and other measurements that might reveal new facts about the cloudy planet's atmosphere.
The European Space Agency (ESA), which cooperates on this mission with the Japan Aerospace Exploration Agency (JAXA), released the first Venus flyby image, taken shortly after BepiColombo's closest approach to the planet, on Tuesday evening (Aug. 10). During the encounter, the probe zipped within 340 miles (552 kilometers) of Venus. More images are expected to follow, ESA has said.
The first Venus selfie image, taken on Tuesday at 9:57 a.m. EDT (13:57 pm GMT) when BepiColombo was at a distance of 977 miles (1,573 km) from the surface of Venus, was captured with one of the three 'selfie cameras' aboard the spacecraft.
The three cameras, providing black and white images with a resolution of 1024 x 1024 pixels, were originally intended to monitor the deployment of BepiColombo's solar arrays after its launch in October 2018. But the BepiColombo team has since found creative ways of taking advantage of them during the overall nine planetary flybys that the spacecraft has to perform to get to its destination.
In April 2020, BepiColombo took images of Earth as it waved its home planet goodbye for the last time from a distance of 7,900 miles (12,689 km). In October 2020, the spacecraft got its first glimpse of Venus when it swung by the planet at a distance of 6,650 miles (10,700 km). Tuesday's encounter was much closer to the planet.
BepiColombo's next planetary photo opportunity is less than two months away (October 1), when the spacecraft — named after Italian physicist Giuseppe (Bepi) Colombo — takes its first look at Mercury. BepiColombo will make overall six flybys at the smallest and innermost planet of the solar system, before entering its intended orbit in 2025. All these flybys are designed to adjust BepiColombo’s trajectory and slow it down against the gravitational pull of the sun, so that it can eventually approach Mercury in the right way.
Better photo opportunities ahead
Speaking about the latest Venus flyby, Johannes Benkhoff, BepiColombo project scientist at ESA, told Space.com that the Venus images were, unfortunately, overexposed because of the planet's strong albedo, or its reflectivity.
"Venus is a very bright planet and those selfie cameras weren't designed to observe such bright objects from such a close distance," Benkhoff said.
BepiColombo also carries a high resolution stereoscopic camera, however, that cannot be used during its cruise through the inner solar system.
The satellite actually consists of three spacecraft stacked on top of each other, which means that some of the instruments are hidden. The spacecraft carries two orbiters, the European Mercury Planetary Orbiter and the Japanese Mercury Magnetospheric Orbiter, which sit atop the Mercury Transfer Module. With its 15-meter solar arrays, the transfer module is responsible for getting the two orbiters to Mercury and will be dumped once the trio reaches its destination. Only after the two orbiters separate and enter their respective orbits will they be able to fully use all their instruments.
But even in the travel configuration, some of the instruments have been taking valuable data during the flybys. The latest flyby at Venus could provide especially interesting information about the chemical composition of Venus’ atmosphere as the spacecraft flew so close to the planet, Benkhoff said.
The upcoming flyby at Mercury is expected to produce better quality images than this one at Venus, Benkhoff added, because Mercury is a darker planet.
"At Mercury, we really hope that we will see some structures on the surface, which we couldn't see at Venus because of its brightness," Benkhoff said.
The Venus flyby, due to its close proximity to the planet, provided the first opportunity to test BepiColombo's scientific instruments at about the same distance from a surface that they were designed to operate at.
The upcoming Mercury flyby will come even closer, to a distance of only 125 miles (200 km) from the surface of Mercury. The October flyby will be the first time any spacecraft will have visited the scorched rocky planet close to the sun since the end of NASA's Messenger mission in 2015.
The BepiColombo team hopes their orbiters will help shed light on some of the mysteries of the tiny planet uncovered but not fully explored by Messenger, for example, whether it really has water ice in its polar craters.
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