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The spacecraft’s high-gain antenna and communications system transmits science data every 13.7 days, each time TESS is closest to Earth. Such regular data transfers allow scientists to frequently monitor changes in a star’s brightness and determine whether a transit is occurring. The transmitter uses 2 watts of power and transfers data at a rate of 100 megabits per second during four-hour intervals at each orbital perigee, when TESS is about 67,000 miles (108,000 kilometers) away. This is 45,000 miles (72,000 km) higher than geosynchronous orbit, where most communications satellites operate, and nearly 30 percent as far as the Moon.