NASA的“逐日”计划

NASA的“逐日”计划

NASA宣布明年将发射探测器进入日冕“接触”太阳，这将使得人类近距离观测太阳活动成为可能。

测试中可能遇到的词汇和知识：

corona日冕[kə'rəʊnə]

particle颗粒['pɑːtɪk(ə)l]

heroic英雄的；英勇的[hɪ'rəʊɪk]

radiation辐射；发光[reɪdɪ'eɪʃ(ə)n]

thermal热的；热量的['θɜːm(ə)l]

ejection喷出；排出物[ɪ'dʒɛkʃən]

terrestrial地球的；陆地的[tə'restrɪəl]

Nasa unveils pathfinding mission to ‘touch the Sun’（659 words）

By Clive Cookson

A US spacecraft will swoop inside the Sun's corona, its superheated outer atmosphere, on a pathfinding mission to learn more about how stars work.

Nasa's $1.5bn Parker Solar Probe, which will be protected by a shield that can withstand temperatures of 1,400C, will journey within 6m km of the Sun's surface, seven times closer than any previous spacecraft.

“We will finally touch the Sun,” Nicola Fox, senior mission scientist, told a conference in Chicago at which Nasa gave a progress report on the spacecraft planned to launch next year.

The spacecraft is named in honour of Eugene Parker, a solar physics pioneer from the University of Chicago who in 1958 predicted the solar wind — the stream of energy and electrically-charged particles that flow from the Sun into space at more than 1m miles per hour.

“I am greatly honoured to have been associated with this heroic space mission,” said Professor Parker, the first living individual to have a Nasa spacecraft named after him. He turns 90 next week.

Nasa and the European Space Agency have launched several satellites in the past to observe the Sun but they have operated from further away, where the heat and radiation are less intense.

Advances in thermal engineering and materials technology make the closer approach of the Parker Probe possible, in particular a carbon-composite shield 11.4cm thick that protects its payload. The four scientific instruments will remain at around terrestrial room temperature. Their main goal is to trace the origin of the solar wind and how it gathers speed through the corona.

“Until we go there and touch the Sun, we can't answer basic questions like ‘Why is the corona much hotter than the Sun itself?’,” said Ms Fox of Johns Hopkins University.

Instabilities in the corona lead to solar flares and mass ejections of highly magnetised material. When these reach Earth's atmosphere, they cause “space weather” — changes in the terrestrial magnetic field and radiation levels.

Scientists say solar super-storms might destroy vulnerable infrastructure such as electric grids and communications satellites, though operators could take emergency action to reduce the damage if they receive advance warning.

Nasa plans to launch the 685kg craft from Kennedy Space Center in Florida next summer on its Delta IV-Heavy rocket, the most powerful available. It will take almost seven years to reach the Sun via a series of fly-bys of the planet Venus.

The European Space Agency is also preparing a mission to the Sun, though it will not get as close as the Parker Solar Probe. Esa's Solar Orbiter is due to launch no earlier than October 2018, also from Kennedy Space Center. The two missions will be co-ordinated to make complementary observations of the same events in the corona from different positions.