So, imagine that you urgently need to contact a rover on Mars. How can you do this? In order for humanity to have the opportunity to even virtually visit Mars, the signal sent from the Earth must travel at least fifty-five million kilometers! Even with such a distance, which is considered the smallest and happens once every 15-17 years during the Great Confrontation, the delay in the received signal will be approximately 3 minutes. So how, then, can you get through to Mars, and preferably without interference?
How are rovers controlled from Earth?
Despite the fact that the planet Mars is very far from us, rovers, created by man, already plow its rusty surface. These small devices not only take full-color images, but also transmit a huge amount of scientific data to Earth.
In order for you and me to enjoy panoramic photographs of the Martian landscape, scientists have created a real system that allows us to track the entire process of transmitting data received on the Red Planet.
So, most often in the process of transmitting data from Mars, 3 main figures are involved - a space communications center located on Earth, a satellite located in Mars orbit and the rover itself.
Due to the fact that the planet Earth rotates very quickly on its axis, in order to provide a continuous signal from Mars, we need to have several points for receiving and transmitting data. These points are called DSN stations. The stations are located in the United States, Spain and Australia, and when our planet turns the other way, the signal is simply transferred from one station to another, allowing him to operate the spacecraft 24 hours a day.
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The most commonly used station for communication with rovers is the DSN station located near the Australian capital, Canberra. This complex has three active antennas of different sizes: DSS-34 and DSS-45, whose diameters are 34 meters, and DSS-43, which is more than 70 meters.
In general, the station has 4 different functions. So, in order to receive a clear signal coming from Mars, the Canberra station must not only receive encrypted data, but also monitor the possibility of communication between the two planets, process the data, transmit the control teams of scientists to the rover and monitor the systems of the DSN station itself.
DSN station in Canberra, Australia.
All information to be received by the rover is sent to the DSN station, from where it is sent on a space journey to the distant "Red Planet". The signal goes to the planet for about 5-10 minutes, provided that Mars is at a relatively close distance from the Earth, after which it is caught by an orbiting Martian satellite, which sends a coded signal to the rover's receiver.
All rovers are equipped with special antennas, each of which is used to receive and transmit data. So, the Curiosity rover is equipped with three antennas at once, each of which has its own functions. The LGA antenna is responsible for receiving information, the UHF antenna is most commonly used for transmitting data, and the HGA equipment is responsible for receiving commands to control the rover.
Sometimes the rover generates so much information that it is not always possible to send all the useful data to Earth. In order to solve this problem, NASA specialists set priorities of importance, due to which part of the data is simply deleted before it reaches our planet.
Do you need satellites to contact Mars?
As we found out earlier, to communicate with the rovers, we need to use satellites in orbit of the "Red Planet". Each of these satellites communicates with the rover through special communication windows, which usually only last a few minutes. Despite the short interaction time, this time is quite enough to transfer all the necessary amount of information.
If until 2006 the Odyssey satellite performed the work of a signalman, at present a new satellite Mars Reconnaissance Orbiter or MRO is working with it. In addition to having a very impressive arsenal of state-of-the-art scientific instruments, the MRO is equipped with the latest HiRISE camera, which allows you to take high-resolution images.
DSN stations are in contact with the MRO for about 16 hours a day, since the rest of the time the satellite is located on the far side of Mars and is closed from signal transmission by the thickness of the planet.
Despite the seeming simplicity of the process, the cost of one hour call is currently about $ 10,000. So, if one day you suddenly want to make a call to a future Martian colony, then first you have to collect a decent amount. Well, after reading this article, you will at least know why your call will cost so much money.
Daria Eletskaya