When NASA's Voyager program launched two robotic probes in 1977 called Voyager 1 and Voyager 2, they had one mission: explore the outer Solar System. On August 25, 2012, Voyager 1 entered interstellar space and had traveled further than any other man-made object. On September 5, 2017, Voyager 1 will be 40 years old, and NASA wants to celebrate by sending the probe a message.

The message sent will be decided upon by the team at NASA and a public vote. But before that happens, NASA wants ideas for what message to send, and it is turning to social media to collect your suggestions.

Uplifting messages can be posted on Twitter, Instagram, Facebook, Google+, or Tumblr. They can be a maximum of 60 characters long and must also contain the tag #MessageToVoyager. Submissions will be accepted until 11:59pm PDT on August 15. After that, JPL, NASA, and the Voyager team will select their favorites and then those message will be put to a public vote.

The winning message will be beamed into interstellar space on September 5 to celebrate the 40 year mission anniversary.

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After that, Voyager 1 will continue its extended mission traveling at a velocity of 17km/s. But that mission does have an end date falling between 2025-2030 due to the radioisotope thermoelectric generator powering all on-board instruments no longer generating enough power for operation.

Before then, the Data Tape Recorder operation will be terminated in 2018 before scientific instrumentation shutdowns start happening from 2020. Voyager 1 will continue its journey indefinitely, though, carrying a golden record packed with information in case it does ever come into contact with intelligent life forms again.

This article originally appeared on PCMag.com.