The large antennas of the Deep Space Network (in California, Australia, and Madrid) They periodically listen for the weak signals from the probe Voyager 1, which has been flying through space since 1977. Almost 45 years. Normally, the data it receives is about plasma density, magnetic fields, and cosmic rays. These are the only instruments on the spacecraft that are still functioning, as the others were shut down long ago to save power; furthermore, the region it's currently traveling through no longer has anything of interest to—for example—its television cameras.
