On Saturday, the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) successfully sent two probes on a joint mission to Mercury, the closest planet to the Sun.
THE LAUNCH: An Ariane 5 rocket, launched from French Guyana, lifted an unmanned spacecraft, BepiColombo, which is carrying the two probes. The spacecraft separated and went into orbit for the 7-year trip to Mercury.
THE MISSION: It is the first European mission to Mercury, and the first to send two spacecraft to make complementary measurements of the planet and its environment at the same time. The orbiters are ESA’s Mercury Planetary Orbiter (MPO) and JAXA’s Mercury Magnetospheric Orbiter (MMO, or ‘Mio’). The ESA-built Mercury Transfer Module (MTM) will carry the orbiters to Mercury using a combination of solar electric propulsion and gravity assist flybys, with one flyby of Earth, two at Venus, and six at Mercury, before entering orbit at Mercury in late 2025.
VENUS EN ROUTE: The two orbiters will be able to operate some of their instruments during the cruise phase, to try and collect data at Venus. Moreover, some of the instruments designed to study Mercury in a particular way can be used in a completely different way at Venus, which has a thicker atmosphere.
MERCURY: A few months before reaching Mercury, the transfer module will be jettisoned, leaving the two science orbiters to be captured by Mercury’s gravity. MPO will separate and descend to its own orbit. Together the orbiters will make measurements (see graphic).
CHALLENGES: The Sun’s enormous gravity makes it difficult to place a spacecraft into a stable orbit around Mercury. The mission will have to ensure a controlled fall. The spacecraft has been specially designed for extreme temperatures. —European Science Agency
Explained Snippets | India’s longest river bridges, over Brahmaputra & elsewhere
A YEAR after India’s longest river bridge was opened in Assam, the government has announced plans for a longer bridge, again over the Brahmaputra. The announcement came ahead of the opening of the world’s longest sea bridge, between the Chinese mainland and Hong Kong. The new bridge over the Brahmaputra, proposed for completion by 2026-27, will run between Dhubri in Assam and Phulbari in Meghalaya, close to the Bangladesh border. At 19.3 km, it will be twice as long as the Dhola-Sadiya bridge, which is currently the longest. Here are some of the numbers that define the country’s longest bridges:
19.3 km The proposed new bridge, between Dhubri and Phulbari. At present, people cross the river either in small boats and by vehicles that have to take a detour of 100 km before climbing the Naranarayan bridge.
4 Number of proposed lanes. The Ministry of Road Transport and Highways is preparing a detailed project report through the National Highways and Industrial Development Corporation Ltd (NICL) and an initial loan amount has been approved by Japanese funding agency JICA, said an official of the Assam’s Public Works Department.
9.15 km The country’s longest river bridge, as of now. Between Dhola and Sadiya in Assam, it extends to 28.50 km if the approach roads on either side are included. It reduces the distance from Rupai (Assam) to Roing (Arunachal Pradesh) by 165 km, and travel time from 6 hours to 1 hour.
6.2 km In Arunachal Pradesh, over the river Dibang, opened this year. Second only to Dhola-Sadiya bridge so far.
5.75 km Patna-Hajipur, over the Ganga, next on the list of river bridges
5.6 km Bandra Worli Sea Link in Mumbai, longest bridge over sea
4.94 km To be opened this year, India’s longest rail-cum-road river bridge (the river bridges above are all road). This bridge, too, will be over the Brahmaputra, connecting Dibrugarh (Assam) to Pasighat (Arunachal).