For roughly two weeks every two years, the solar conjunction takes place, when Mars and Earth are on opposite sides of the sun. This year it’s happening between Oct. 2 and Oct. 14. During this time, the sun obscures the two planets from each other, essentially making Earth and Mars invisible to each other. That means communication with NASA spacecraft on Mars is reduced to a quiet chatter. Normally, the sun ejects hot, ionized gas from its corona, which then makes its way deep into space. That's usually not a problem, but during solar conjunction, this gas can interfere with radio signals when engineers try to communicate with their spacecraft on and above Mars. Commands can be corrupted and result in unexpected behavior from Mars' mission equipment. So, a communication moratorium is put in place during which mission controllers at NASA's Jet Propulsion Lab turn off some instruments and collect and store data from the Odyssey and Mars Reconnaissance Orbiters. While NASA stops sending new signals to its spacecraft during the solar conjunction, controllers front-load their communications and send two weeks' worth of messages in advance to avoid the increased risk of radio interference. When it's over, engineers will spend about a week downloading the information before resuming normal communication operations. If it's determined that any of the collected data is corrupted, engineers can usually have that data retransmitted …. just from a lot farther away.
