By MARCIA DUNN

CAPE CANAVERAL, Fla. (AP) — Astronauts launched an extraordinarily complicated series of spacewalks Friday to fix a cosmic ray detector at the International Space Station.

Armed with dozens of dissecting tools, Italian astronaut Luca Parmitano removed two protective covers to gain access to the inside of the Alpha Magnetic Spectrometer. He handed them to his U.S. spacewalking partner, American Andrew Morgan, for tossing overboard.

“OK, 3-2-1, release,” Morgan said as he let go of the 4-foot-long (127-centimeter) shield high above the Pacific.

Later, over the South Atlantic, Morgan ditched the second, smaller cover. “Another great pitch,” Mission Control radioed.

These latest pieces of space junk pose no danger to the orbiting lab, according to NASA. The larger shield should remain in orbit a year or so before re-entering the atmosphere and burning up. The smaller one should re-enter in a few weeks.

NASA considers these spacewalks the most difficult since the Hubble Space Telescope repairs a few decades ago. Unlike Hubble, the spectrometer was never meant to undergo space surgery. After 8 ½ years in orbit, its cooling system is almost dead.

Parmitano and Morgan will go out at least four times this month and next to revitalize the instrument. Their second spacewalk is next Friday.

Delivered to orbit by Endeavour in 2011 on the next-to-last space shuttle flight, the $2 billion spectrometer is hunting for elusive antimatter and dark matter.

It’s already studied more than 148 billion charged cosmic rays. That’s more than what was collected in over a century by high-altitude balloons and small satellites, said lead scientist Samuel Ting, a Nobel laureate at the Massachusetts Institute of Technology. He monitored Friday’s 6 ½-hour spacewalk from Mission Control in Houston.

The huge spectrometer — 16 feet by 13 feet by 10 feet (5 meters by 4 meters by 3 meters), with a mass of 7 ½ tons (6,800 kilograms) — was designed to operate for three years. By installing four new and improved coolant pumps, the astronauts can keep it working throughout the life of the space station, or another five to 10 years. The replacement pumps arrived at the space station nearly two weeks ago, along with an assortment of new tools.

Parmitano, the lead spacewalker, and Morgan trained extensively for the plumbing job before rocketing into orbit in July. They hustled through Friday’s cover removals and even got a jump on future chores.

Next week’s spacewalk will involve slicing through stainless steel tubes and splicing in connections for the new pumps, which like the old will use liquid carbon dioxide as the coolant.

In some respects, this work, 250 miles (400 kilometers) up, is even trickier than the Hubble spacewalks, said NASA project manager Ken Bollweg. As before, the stakes are high.

“Any time you do heart surgery you’re taking some risks,” Bollweg said in an interview earlier this week.

Morgan is an emergency physician in the Army — a bonus for this kind of intricate work. He’s making his first spaceflight.

For second-time station resident Parmitano, it marked his return to spacewalking following a close call in 2013. He almost drowned when his helmet flooded with water from the cooling system of his spacesuit. Unable to talk because of the rising water, he managed to keep his cool as he made his way back to the safe confines of the space station.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

By JULIE PACE, BILL BARROW and STEVE PEOPLES

WASHINGTON (AP) — Former Massachusetts Gov. Deval Patrick announced Thursday he is running for president, making a late entry into the Democratic race less than three months before primary voting begins.

In an announcement video, Patrick highlighted his poverty-stricken childhood on Chicago’s South Side, saying he’s running for the “people who feel left out and left back.”

As the first in his family to go to college and law school, Patrick said, “I’ve had a chance to live my American Dream.” But over the years, the “path to that dream” has closed off for others, he said, as government and economy have been “letting us down.”

Patrick made history as the first black governor of Massachusetts and has close ties to former President Barack Obama and his network of political advisers. But he faces significant fundraising and organizational hurdles this late in the race.

His announcement comes as some Democrats worry about the strength of the party’s current field of contenders. Another Democrat, former New York City Mayor Michael Bloomberg, is also weighing a last-minute bid for the party’s nomination.

Bloomberg has taken steps toward launching a presidential campaign, filing candidate papers in Alabama and Arkansas. Even 2016 nominee Hillary Clinton this week said in a BBC interview that she is “under enormous pressure from many, many, many people to think about it,” adding that she has no such plans but still would “never, never, never say never.”

The moves reflect uncertainty about the direction of the Democratic contest with no commanding front-runner. Joe Biden, Obama’s vice president, entered the race as the presumptive favorite and maintains significant support from white moderates and black voters, whose backing is critical in a Democratic primary. But he’s facing spirited challenges from Patrick’s home state senator, Elizabeth Warren, and Vermont Sen. Bernie Sanders, progressives whose calls for fundamental economic change have alarmed moderates and wealthy donors.

Patrick was asked on CBS if he supports the “Medicare for All” health care plan, which is pushed by Sanders and would replace job-based and individual private health insurance with a government-run plan that guarantees coverage for all with no premiums or deductibles and only minimal copays for certain services.

“No, not in the terms we’ve been talking about,” Patrick said. “I do support a public option, and if Medicare is that public option, I think it’s a great idea.”

Patrick also acknowledged the challenges posed by his late entry in such a big field of candidates.

“When I was thinking about it many months ago, one of the questions was: How do you break though in a field this large and this talented without being a celebrity or sensationalist? And I’m none of those things,” Patrick said on “CBS This Morning.”

Patrick could present himself as a potential bridge across the moderate, liberal and progressive factions — as candidates like South Bend, Indiana, Mayor Pete Buttigieg, California Sen. Kamala Harris and New Jersey Sen. Cory Booker are trying to do.

But the former governor faces significant hurdles to raise enormous amounts of money quickly and to build an organization in the traditional early voting states that most of his rivals have focused on for the past year. And he’ll have to pivot to the expensive and logistically daunting contests of Super Tuesday, when voters in more than a dozen states and territories head to the polls. Bloomberg’s team has said they will skip the early states of Iowa, New Hampshire, Nevada and South Carolina to focus on the Super Tuesday roster.

It’s also a near certainty that Patrick — and possibly Bloomberg — wouldn’t make a Democratic debate stage until January, if at all, because of debate rules set by the party.

Those dynamics left some prominent Democrats questioning Patrick’s viability.

“Stop. We have enough candidates,” said Kathy Sullivan, a Democratic National Committee member from New Hampshire, which hosts the party’s first presidential primary following the Iowa caucuses.

Texas Democratic Chairman Gilberto Hinojosa, whose state boasts the second-largest number of Super Tuesday delegates behind California, argued that donors and media are mistaken to think that rank-and-file Democrats see Biden, Warren and others as unable to take down President Donald Trump.

Besides, Hinojosa said, “most of the people you need to build out a campaign have already chosen sides.”

Patrick, a former managing director for Bain Capital, has close ties to Wall Street donors. As only the nation’s second elected black governor since Reconstruction, Patrick also could run as a historic boundary breaker trying to dent Biden’s support among African Americans — though Harris and Booker, the only two black Democrats in the Senate, have been unable to do that thus far.

Patrick has remained active in politics since his term as governor ended in 2015. During the 2018 midterm elections, he traveled across the country in support of Democratic candidates, raising his national profile. He also campaigned for Doug Jones during Alabama’s contentious 2017 special election for U.S. Senate.

Last year, some of Patrick’s supporters and close advisers launched the Reason to Believe political action committee, which held meetups across the country, including in early presidential primary states.

By December, however, Patrick cooled to the idea of a presidential bid.

“After a lot of conversation, reflection and prayer, I’ve decided that a 2020 campaign for president is not for me,” Patrick posted on his Facebook page at the time. Patrick said he and his wife worried that the “cruelty of our elections process would ultimately splash back on people whom Diane and I love, but who hadn’t signed up for the journey.”

After Trump’s election, Patrick’s initial criticism of the Republican president was somewhat less pointed than other Democrats offered. “We need our presidents to succeed,” he said, while still expressing concern about what he described as Trump’s belittling of those with opposing points of view.

Patrick also urged the party at the time to look in the mirror, saying that “the outcome of the 2016 election was less about Donald Trump winning than Democrats and our nominee letting him do so.”

Early in his career, Patrick served as assistant attorney general for civil rights in President Bill Clinton’s administration and later worked as an executive at Texaco and Coca-Cola. Since leaving the governor’s office, Patrick has worked as a managing director for Bain Capital, a company co-founded by 2012 Republican presidential nominee Mitt Romney, Patrick’s predecessor as governor.

Patrick’s Massachusetts record is mixed. His successes include helping oversee the 2006 health care law signed by Romney that would go on to serve as a blueprint for Obama’s 2010 health care law.

But Patrick also was forced to publicly apologize for a disastrous effort to transition to the federal health care law during which the state’s website performed so poorly it created a backlog of more than 50,000 paper applications.

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Barrow reported from Atlanta. Peoples reported from Concord, N.H.

By LISA MASCARO and MARY CLARE JALONICK

WASHINGTON (AP) — The U.S. House launched the first public hearing Wednesday of Donald Trump’s impeachment investigation, the extraordinary process to determine whether the 45th president of the United States should be removed from office.

Rep. Adam Schiff, the Democratic chairman of the House Intelligence Committee, immediately outlined the question at the core of the impeachment inquiry — whether the president used his office to pressure Ukraine officials for personal political gain.

“The matter is as simple and as terrible as that,” Schiff said. “Our answer to these questions will affect not only the future of this presidency but the future of the presidency itself, and what kind of conduct or misconduct the American people may come to expect from their commander in chief.”

It was a remarkable moment, even for a White House full of them. The hearing is the first chance for America, and the rest of the world, to see and hear for themselves about Trump’s actions toward Ukraine and consider whether they are, in fact, impeachable offenses.

The proceedings were being broadcast live, and on social media, from a packed hearing room on Capitol Hill. The country has been here only three times before, and never against the 21st century backdrop of real-time commentary, including from the Republican president himself.

Testifying will be two seasoned diplomats, William Taylor, the graying former infantry officer now charge d’affaires in Ukraine, and George Kent, the deputy assistant secretary in Washington, telling the striking, if sometimes complicated story of a president allegedly using foreign policy for personal and political gain ahead of the 2020 election.

So far, the narrative is splitting Americans, mostly along the same lines as Trump’s unusual presidency. The Constitution sets a dramatic but vague bar for impeachment, and there’s no consensus yet that Trump’s actions at the heart of the inquiry meet the threshold of “high crimes and misdemeanors.”

Trump calls the whole thing a “witch hunt,” a retort that echoes Nixon’s own defense. “READ THE TRANSCRIPT,” he tweeted Wednesday.

At its core, the inquiry stems from Trump’s July 25 phone call with Ukraine’s newly elected president, Volodymyr Zelenskiy when he asked the Zelenskiy for “a favor.”

Trump wanted the Ukraine government to investigate Democrats in the 2016 election and his potential 2020 rival, Joe Biden, all while holding as leverage military aid the young democracy relies on as it confronts an aggressive Russia.

An anonymous whistleblower first alerted officials to concerns about the phone call. The White House released a rough transcript of the conversation, with portions deleted.

Democratic House Speaker Nancy Pelosi was initially reluctant to launch a formal impeachment inquiry. But she pressed ahead in September after the whistleblower’s complaint.

The White House has instructed administration officials not to testify in the inquiry. But over the past month, witness after witness has appeared behind closed doors to tell the investigators what they know.

Most received subpoenas to appear, and both Taylor and Kent had fresh subpoenas Wednesday.

Trump lashed out at the witnesses, tweeting they were “NEVER TRUMPERS,” but the two are career diplomats working for both Republican and Democratic administrations. There’s no evidence they engaged in partisan activity opposing Trump.

Whether Wednesday’s proceedings begin to end a presidency or help secure Trump’s position, it was certain his chaotic term had finally arrived at a place he could not control and a force, the constitutional system of checks and balances, that he could not ignore.

Unlike the Watergate hearings and Richard Nixon, there is not yet a “cancer-on-the-presidency” moment galvanizing public opinion. Nor is there the national shrug, as happened when Bill Clinton’s impeachment ultimately didn’t result in his removal from office. It’s perhaps most like the partisanship-infused impeachment of Andrew Johnson after the Civil War.

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Associated Press writers Colleen Long, Mike Balsamo, Eric Tucker, Laurie Kellman, Alan Fram, Zeke J. Miller and Matthew Daly in Washington contributed to this report.