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時間:2022-08-15 來源:本站 點擊:258次

NASA's new space telescope reaches destination in solar orbit******

NASA's James Webb Space Telescope, designed to give the world an unprecedented glimpse of infant galaxies in the early stages of the universe, arrived at its gravitational parking spot in orbit around the sun on Monday, nearly a million miles from Earth.

With a final five-minute, course-correcting thrust of its onboard rocket, Webb reached its destination at a position of gravitational equilibrium known as the second Sun-Earth Lagrange point, or L2, one month after launch.

The thruster was activated by mission control engineers at the Space Telescope Science Institute in Baltimore, with radio signals confirming Webb was successfully "inserted" into its desired orbital loop around L2.

Webb will follow a special "halo" path that keeps it in constant alignment with Earth but out of its shadow, as the planet and telescope circle the sun in tandem. The L2 orbit within the larger solar orbit enables uninterrupted radio contact, while bathing Webb's solar-power array in non-stop sunlight.

Minimizing drift

By comparison, Webb's 30-year-old predecessor, the Hubble Space Telescope, orbits the Earth 547 kilometers away, passing in and out of the planet's shadow every 90 minutes.

The combined pull of the sun and Earth at L2 – a point of near gravitational stability first deduced by 18-century mathematician Joseph-Louis Legrange – will minimize the telescope's drift.

But ground teams will need to fire Webb's thruster briefly again about once every three weeks to keep it on track, Keith Parrish, the observatory's commissioning manager from NASA's Goddard Space Flight Center said.

Mission engineers are preparing next to fine-tune the telescope's primary mirror – 18 hexagonal segments of gold-coated beryllium metal measuring 6.5 meters across, far larger than Hubble's main mirror.

US reinstates 352 product exclusions from China tariffs******

The US Trade Representative's office said on Wednesday it will reinstate 352 expired product exclusions from US "Section 301" tariffs on Chinese imports.

The reinstated exclusions, initially granted by the Trump administration to provide certain sectors relief from the punitive tariffs on Chinese goods, had expired at the end of 2020. 

US Trade Representative Katherine Tai last October had launched a review to reinstate exclusions on a narrow list of 549 individual product categories.

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Colin Powell dies of Covid******

Colin Powell, the first black secretary of state who saw his legacy tarnished when he made the case for war in Iraq in 2003, has died from complications from COVID-19. He was 84.

"We have lost a remarkable and loving husband, father, grandfather and a great American," the family said in a statement posted to social media yesterday.

The retired four-star general and former chairman of the Joint Chiefs of Staff who served four presidents made his reputation as a man of honor distant from the political fray – an asset in the corridors of power.

After the 1991 Gulf War he was so widely respected that he was even touted as a future president of the United States, but ultimately he never ran for the White House.

"General Powell is an American hero, an American example, and a great American story," George W. Bush said as he announced the nomination of Powell, the son of Jamaican immigrants, who became the Republican president's secretary of state in 2000.

"In directness of speech, his towering integrity, his deep respect for our democracy, and his soldier's sense of duty and honor, Colin Powell demonstrates ... qualities that will make him a great representative of all the people of this country."

But he found it hard to live down his infamous February 2003 speech to the United Nations Security Council about the alleged existence of weapons of mass destruction in Iraq – evidence which was later proven to be false.

"It's a blot ... and will always be a part of my record. It was painful. It's painful now," Powell said in a 2005 interview with ABC News.

Tributes nevertheless poured in from Congress, where Democratic Senator Mark Warner praised Powell as "a patriot and a public servant," while House Republican Peter Meijer described him as a rarity in the modern age: "a true soldier statesman."

The family statement said Powell had been fully vaccinated.

Born April 5, 1937 in Harlem, Powell's "American Journey" – the title of his autobiography – started in New York, where he grew up and earned a degree in geology.

He also participated in the Reserve Officers' Training Corps in college, and upon his graduation in June 1958, he received a commission as a second lieutenant in the US Army, and was posted in what was then West Germany.

Powell completed two tours of duty in Vietnam – in 1962-1963 as one of John F. Kennedy's thousands of military advisers, and again in 1968-1969 to investigate the My Lai massacre.

He earned a Purple Heart.

But he also faced questions about the tone of his report into the hundreds of deaths at My Lai, which to some seemed to dismiss any claims of wrongdoing.




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