NASA announced yesterday that it plans to start testing the DSAC (Deep Space Atomic Clock) soon. The device is nothing more than an extremely precise clock – and as bland as it may sound, it is a piece that can greatly facilitate space exploration missions in the future.
Atomic clocks have been around for some time. They work based on the frequency of energy oscillation of certain atoms, such as Cesium-133, and so are the most accurate clocks that exist. But even so, they are still not accurate enough to allow spacecraft to make navigation decisions without consulting a terrestrial satellite. DSAC, however, should change that.
Signs that come and go
When a spacecraft is going to make any kind of change in its course, it must first know precisely where it is. For this, a satellite on Earth sends a very precise radius of radio waves to the ship and, when the waves arrive there, the ship’s communication equipment responds. The waves, however, take some time to go back and forth – based on the time the signal has taken, it is possible to calculate the exact position of the spacecraft, and then guide it in its trajectory.
This process, however, has some problems. Since ships usually stay at enormous distances from Earth, the travel time of the signal can be a few hours – even considering that the waves travel at the speed of Light. And because of this, any small error in the round trip time of the signal can lead to an error of many kilometers in the estimation of the ship’s position. This can lead to errors in the spacecraft’s trajectory.
In the right nanosecond
With a more accurate clock, according to NASA, spacecraft would not depend on a signal coming from (and then to) Earth. They could simply send a signal to Earth and measure the time it takes to get there. This would give more autonomy for space vehicles to determine their own trajectory.
Otherwise, it would also allow each satellite on Earth to serve simultaneously several spacecraft. As satellites now need to send the signal to the spacecraft, they need to be pointed at them very accurately, and they can only communicate with one ship at a time. If the spacecraft did not depend on the signal sent by the satellites, each satellite could receive signals from several ships (and guide them all) at the same time.
According to Engadget, the DSAC will be launched this year aboard the General Atomic’s Orbital Test Bed. It has the approximate size of a large toaster, and so can be easily shipped. The US space agency expects it to have a precision of two nanoseconds (two billionths of a second), but its ultimate goal is to reach a precision of 0.03 nanoseconds (thirty trillionths of a second).