When a white package fell from the sky and landed in central New Jersey this week, the people who found it were alarmed not only by the device’s strange hissing sound — but also by the handwritten note that referred to President Trump, the authorities said.

On Tuesday morning, the Styrofoam-wrapped package attached to a red parachute floated down from the atmosphere. It dropped onto a solar panel field in South Brunswick, N.J., about 25 miles south from where Mr. Trump was staying in Bedminster. People who work nearby called the authorities, and police officers, firefighters and a bomb squad responded to investigate the potential threat, according to a news release from the South Brunswick Police Department.

The note, which appeared to have been written in black marker, said, “NASA Atmospheric Research Instrument NOT A BOMB!”

It went on: “If this lands near the President, we at NASA wish him a great round of golf.”

The all-caps assurance that the package was not, in fact, a bomb did little to quell the anxieties of those who discovered it.