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By Jonathan AmosBBC Science Correspondent SolO was launched in February and is on a mission to understand what drives our star's dynamic behaviour. The close pass, known as a perihelion, puts the probe between the orbits of Venus and Mercury. In the coming years, SolO will go nearer still, closing to within 43 million km of the Sun on occasions. As it stands today, only five other missions have dived deeper into the inner Solar System: Mariner 10, Helios 1 & 2, Messenger, and Parker Solar Probe. Earth orbits 149 million km (93 million miles) on average from the Sun. SolO is a European Space Agency (Esa) craft that was assembled in the UK by the aerospace company Airbus. BBC Radio 4's In our time: What is the solar wind and how does it affect us? It has spent the four months since launch undergoing a checkout phase. Engineers have been running the rule over all the probe's systems and commissioning its 10 scientific instruments. Routine operations for the full suite of onboard experiments are still a year away, but SolO's magnetometer is up and running and will remain so. Sitting at the end of a long boom at the back of the spacecraft, the MAG senses the magnetic fields embedded in the solar wind - the stream of charged particles billowing away from the Sun. Already, the instrument is catching the disturbances that result from big explosions on the star called coronal mass ejections - in addition to the everyday waves and turbulence that trace the wind's structure. "We switched on, on 24 February - we've already got over 2 billion magnetic field vectors on the ground. We've got a happy, busy science team working away at the data," said Prof Tim Horbury, the MAG principal investigator at Imperial College London. One of the reasons the British group's instrument got turned on very early was so it could start to characterise the confounding magnetic fields generated by the electronics in the rest of the spacecraft. This signal is small but needs to be subtracted from the Sun measurements to finesse the detail in the data properly. The early start also gave the London team the chance to do some tandem study with the magnetometer instrument on Esa's BepiColombo mission. As chance would have it, this probe was making a return visit to Earth in April on its way to Mercury. The two missions were therefore able to do some multi-point sensing of the solar wind in relatively close proximity to each other. The same has been true with the American Parker Solar Probe - but at a much greater separation. This US mission is in the process of making some very deep dives past the Sun (on 7 June it passed just 19 million km from the star). "We're now just one of a constellation of spacecraft flying around the Sun," Prof Horbury told BBC News. The next major event for SolO is a flyby of Venus. This occurs at the end of December and will see the probe track about 500,000 km above the planet's surface. The full science phase of the mission is due to start in 2021 when all 10 of SolO's instruments, including its imagers, will begin regular observations. "I was so nervous when we launched," said Prof Horbury. "I guess the more you know about a project, the more you know about the things that can go wrong. But Solar Orbiter is out there, it's working and it's going to be a fantastic success." Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos
Europe's Solar Orbiter (SolO) probe makes its first close pass of the Sun on Monday, tracking by at a distance of just over 77 million km.

Ministry spokesman Hong Lei said the view, expressed by Secretary of State Hillary Clinton, "neglects the facts". Mrs Clinton had warned that the US opposed any action that would undermine Japanese administration of the islands. The row over the islands, called Diaoyu in China and Senkaku in Japan, has left ties between Tokyo and Beijing tense. In her comments on Friday following a meeting with Japanese Foreign Minister Fumio Kishida, Mrs Clinton said the US did not take an official view on the sovereignty of the islands. But she said Washington opposed "any unilateral actions that would seek to undermine Japanese administration". "We want to see China and Japan resolve this matter peacefully through dialogue." "We do not want to see any action taken by anyone that could raise tensions or result in miscalculation that would undermine the peace, security and economic growth in this region." In Monday's regular briefing to journalists, Mr Hong said the US "bears undeniable historical responsibility on the Diaoyu issue". "The US comments ignore facts and confuse truth with untruth," he said. "China is strongly displeased and firmly opposed to it. We urge the US to responsibly treat the Diaoyu issue, watch their words and deeds, maintain regional stability and Sino-US relations, so that Chinese people can trust them." Mr Hong added that there was no doubt that China owns the islands, and said the reason for the "extreme tensions" was Japan's "illegal purchase" of them. It was the second time in two days the foreign ministry had condemned the remarks - on Sunday, spokesman Qin Gang said the ministry "resolutely opposes" the US remarks. The row over ownership of the islands, which lie south of Okinawa and north of Taiwan, has been rumbling for years. It reignited in September when the Japanese government purchased three of the islands from their private Japanese owner, leading to protests in some Chinese cities and fall-out for some Japanese businesses operating in China. Chinese government ships have since sailed many times through what Japan says are its territorial waters around the islands. On Monday, Japan said three Chinese maritime surveillance ships had again entered waters around the islands in the early morning, spending about 15 minutes there. China had already said it had three ships patrolling the area. It announced last week it would be carrying out a geological survey of the islands as part of its "programme to safeguard its maritime rights and interests". Japan's foreign ministry lodged a protest with the Chinese embassy, the Kyodo news agency reports.
China's foreign ministry has strongly criticised the US for backing Japan's control of a disputed group of islands in the East China Sea.

The 119 trains, nearly all in London, will run from 5 September. The operator introduced a reduced service in July after months of delays and cancellations, which it blamed on "unprecedented" staff sickness. Southern is in a long-running dispute with its guards and the latest 48-hour strike begins on 7 September. The reinstated trains include: Southern said it planned to "steadily" bring back further services, for Sussex and Surrey, in the coming weeks as train crew became available. The RMT rail union is fighting moves to turn conductors on Southern into "on-board supervisors", with drivers taking over responsibility for opening and closing carriage doors. The union has said it has concerns over safety and job cuts, but the company began imposing the changes earlier in August.

Southern rail is to reinstate more than a third of the 341 daily services it axed earlier in the summer to provide a more reliable timetable.

