The Martian

Back on Earth, JPL receives the Pathfinder signal. While Watney has been traveling, they have been building a control center that can use the Deep Space Network to connect to the old Pathfinder system. The camera on Pathfinder is working, and Watney knows this because, when JPL connects to the Pathfinder, he sees the antenna on Pathfinder move to acquire the signal. For the first time, when this antenna moves, Watney knows that NASA and JPL know that he is alive.

At this point, he has been stranded on Mars for 3 months; it is sol 97. Because NASA is using the camera to communicate, he can write messages and send pictures to them, but they have no way to respond. Watney develops a quick and crude system by which he asks yes/no questions, and they point the camera at a sign that says yes or the one that says no. From there, he develops the system to incorporate ASCII, a code to convey letters, numbers, and other symbols; he draws cards and holds them up to the camera, and the camera points at different cards to spell out messages. However, this doesn’t solve the fact that the transmission time is about a half hour per message.