One of the most amazing things about the mission is the path the spacecraft has taken. Because it’s so big (about the size of a bus), there was no way to directly launch it from here all the way to Saturn. Instead, we launched it towards Venus.
By taking advantage of the force of gravity that Venus exerts on the orbiter (and carefully calculating trajectories), we were able to get a free ride: this force, and the momentum force of the orbiter at the proper angle, combined to shoot Cassini towards Earth again. Once it got far enough into Earth’s gravity field, we used the same trick to propel the orbiter on its final course towards Saturn. (Of course, Cassini also recorded lots of data about Venus and Earth in the process.) The ride isn’t actually free; the planet loses the energy gained by the orbiter. It’s a negligible loss for the massive planet, but a huge energy gain for the (relatively) tiny Cassini.
The amount of data Cassini sends to Earth is also amazing:
Once the spacecraft’s onboard recording device reaches capacity, it will point its high-gain antenna toward Earth and download the data through one of the 70-meter (230-foot) antennas of the Deep Space Network. Cassini will be sending home several gigabytes of data daily.
Several gigs per day? Good thing they aren’t using Comcast as their ISP...
