NASA’s Voyager 1 is on the verge of making history, but the aging spacecraft is having a little trouble keeping in touch with home. Just weeks before becoming the first human-made object to travel a full light-day away from Earth, the probe briefly went silent, and NASA engineers are still working to understand why.

NASA lost contact with Voyager 1 in mid-October after engineers failed to detect its radio signal during two communication attempts 24 hours apart. The signal reappeared a day after the second attempt, but engineers are still investigating what caused the outage, according to NASA .

Launched in 1977, Voyager 1 has traveled an astonishing 16 billion miles (26 billion kilometers) from Earth, but NASA engineers aren’t ready to let it go just yet.…