As scientists have doubled the data rate with New Horizons

Late last year, woke interplanetary probe New Horizons, sent to study Pluto and its moon Charon in 2006. The station made images for optical navigation, but they fall to Earth in two weeks. Why so long? After all, the camera LORRI every day makes only ten images. The answer is simple: Pluto from Earth is at a distance of thirty distance from Earth to the sun. Therefore, the radio signal is weak: New Horizons can transmit one kilobits per second. And receives data only three semidesyatimetrovye plates Deep Space Network NASA.

But the team has a station козырь in the sleeve - trick to increase the transfer rate nearly doubled.






How station transmits data now? H4> To transfer data to Earth New Horizons uses one radio antenna and amplifier. The speed is 1 kbps. Receive data from such a distance capable of three 70-meter dish Deep Space Network NASA for the work that has to fight - in the best case, the team will receive one eight-hour session per day communication. During this time, can send 28 8 megabits of data. While station New Horizons aims to Earth, she does not look at Pluto, so have to choose between the transmission and collection of data.

Camera sensor LORRI, which uses the station is a square with a side of 1024 pixels at 12 bits, we get the file size of 12,582,912 bits. The image can shrink up to 2, 5 megabits lossless, especially - when it takes part of the blackness of space. You can shrink more in JPEG, but for optical navigation need greater precision. 8 hours we get 11 images, if we only pass them. But this is not the only type of data that collects New Horizons.

All this means that during an active data collection station fills the wheels, which then can release - does not have time to send information back to Earth. How to transfer all the data? Need to increase the speed.

70-meter dish in Canberra, Australia. I>



How to increase the speed? H4> New Horizons communication system includes two nearly identical radio amplifier TWTA in the event of failure of one of them. The difference between the two - sided circular polarization. With this TWTA can transmit the same data simultaneously, and special equipment in the Deep Space Network NASA and will combine them. This will increase the signal 1, 9 times in comparison with using one TWTA.

Researchers have come up with this hack after the start station and tried it at the beginning of the mission, but the amplifiers need a lot of energy, and the radioisotope power sources New Horizons degraded almost a decade of use. Its capacity is not enough for the simultaneous operation of two amplifiers together with the provision of other plant systems. So you need to turn off the "something unnecessary." For example, navigation and control system. The following question arises:

How to keep a station aimed at the Earth? H4> To keep the antenna station oriented to the Earth, the energy needed for the positioning system. But scientists have figured out how to work around this limitation. Before long the session using two transmitters station twisted around its axis. Gyroscopic effect stabilizes its direction. To promote the station to spend fuel - hydrazine. Although the pictures using LORRI will be impossible.

To make room for the data the team plans to conduct two long-term communication. The first - from March 10 to April 4, the second - from 15 to 27 May. At this time, the station will not do photos, but some other systems - SWAP, PEPSSI, SDC - will continue to work.

This trick can be used only if both the transmitter will be in the ranks. In any case, you will need more than a year before the Earth will go all the data: they are too many. Soon the energy is not enough for the simultaneous operation of TWTA. By the time the study Kuiper Belt probably will work only one transmitter, so that New Horizons will be a lesson for all patience.






Source: geektimes.ru/post/245238/

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