The panda cam is back on! Government offices are open, too.

WASHINGTON -- The federal government is open again. But it will take more than unlocking the doors, flipping the lights back on and turning on the panda cam before it’s business as usual.

Thousands of federal workers returned to their jobs Thursday after Congress passed and President Obama signed a measure ending the 16-day shutdown. The barricades at the World War II memorial in Washington were removed, and virtually all national parks were back open.

And the panda cam at the National Zoo was back in operation.

“Within 10 minutes of turning the panda cam back on this morning, we reached capacity,” said zoo spokeswoman Pamela Baker-Masson.

But the zoo won’t reopen to the public until Friday because it will take a day to prepare it for visitors, including restocking the refrigerators of food sold to visitors. Zoo officials are worried about the lost revenues during the shutdown

FULL COVERAGE: The U.S. government shutdown

“We just want to get back to business as usual,” said Baker-Masson.

William R. Dugan, president of the National Federation of Federal Employees said it will take a while “for things to start to get back to normal.”

At the National Oceanic and Atmospheric Administration headquarters in Silver Spring, Md., administrator Kathryn Sullivan was at the front door welcoming employees back to work.

Vice President Joe Biden made a surprise visit to the Environmental Protection Agency, bringing muffins. “I didn’t bring enough,” he said when he saw the long line.

As employees entered they were handed a one-page memo including a welcome back note from EPA Administrator Gina McCarthy:

“Dear friends, let me be one of the first to welcome you back to EPA and tell you that we have certainly missed you!” she wrote.

The memo also includes information about transitioning back to work. One note says that “All Government travel is canceled through October 20, 2013.” And lastly: “Please remember to remove your ‘out of office’ messages from email and voicemail and touch base with your supervisor on your immediate work priorities.”

Sally Katzen, a senior advisor at the Podesta Group who worked in the Office of Management and Budget during the last government shutdown 17 years ago, said, “There are inevitably some morale problems that have to be addressed on the return.”

An Interior Department memo welcoming employees back to the job said: “We appreciate your sacrifices through these difficult times and we understand that the lapse in government activities has imposed hardships on you, your families, and the people we serve.”

At NASA’s Ames Research Center in California, furloughed scientist Lee Stone was dreading the 16 days of work piled up on his desk. “We’re going to be expected to catch up,” he said.

Employees may need a bit of time to get back into their routines after “a period of time that has been emotionally draining,” said John Hudak, a fellow in governance studies at the Brookings Institution.

At the EPA, Barbara Bruce, a 38-year employee, said she was happy the shutdown was over.

“I am truly glad to be back,” she said.

The measure approved Wednesday could offer comfort: It provides back pay for furloughed employees.

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Rebecca Clemons in the Washington bureau contributed to this report.