How is it that my cell phone still loses connection in the city and my laptop barely gets the Internet in the mountains, yet NASA’s Lunar Reconnaissance Orbiter (LRO) can keep in touch with Earth from 238,800 miles away, 24 hours a day? Additionally, LRO can transmit 461GB of data per day (the equivalent amount of information found in a huge library), sending this information at a rate of up to 100Mb/s, while my so-called high-speed Internet service struggles to provide about 1-3Mb/s. Obviously, it’s not what you know but who you know!
When NASA engineers designed the Lunar Reconnaissance Orbiter (LRO), they knew it would pointless blasting it to the moon if it couldn’t send and receive information. So they created an extraordinary communications system, one robust enough to send back all the information NASA's robotic scout will collect about the moon's surface and environment over the next 12 months – far more than any previous mission.
At the hub of the space-age communications system is a 13-inch-long tube, called a Traveling Wave Tube Amplifier. It is the first high data rate K-band transmitter to fly on a NASA spacecraft, making it possible for scientists to receive massive amounts of images and data from the orbiter at an unusually fast rate.
The new amplifier lets the LRO transmit 461GB of data per day at a speed of 100Mb/s – so much faster than a typical broadband connection.
L-3 Communications Electron Technologies built the amplifier under the guidance of NASA's Glenn Research Center in Cleveland. The device uses electrodes in a vacuum tube to amplify microwave signals to high power, making it perfect for sending large amounts of data over long distances because it provides more power and more efficiency than its alternative, the transistor amplifier.
LRO’s communication system transmits all the information it collects about the moon's geography, climate and environment, and transmits it to a receiver at a Ka band antenna network at White Sands Test Facility in New Mexico. The large amount of data is needed in order for scientists to compile high-resolution, 3D maps of the lunar surface.
"We're sending back more data than ever, faster and it's nearly real time," said Glenn project manager Todd Peterson.
Traveling Wave Tube Amplifiers have been used for other planetary missions, such as Kepler and Cassini, but previous designs weren’t as powerful as this one, according to Rainee Simons, chief of Glenn's Electron and Optoelectronic Device Branch. He said engineers had to redesign the internal circuitry of the amplifier.
"In order to provide the power and frequency needed to send communications from the vicinity of the moon, it had to be custom designed and handmade," he said.
The redesign also made the device lighter, which makes it more energy efficient – a heavier spacecraft requires more fuel, especially at take-off.
The amplifier was subjected to vigorous spaceflight testing - including vibration, thermal vacuum, radiation and electromagnetic interference tests - to ensure that it could withstand the intense conditions of launch and lunar orbit.
LRO is a said to be a vital step toward returning humans to the moon, but the data is also being analyzed to see if it can be used to improve life on Earth. No wonder Glenn team members were delighted when LRO entered its final orbit and began transmitting data.
It's hoped that if the amplifier can be used on communication satellites, it could allow for much better tracking, monitoring and control of transoceanic flights and ships traveling beyond the reach of radar.
It also could enable real-time data transfer from future Earth-orbiting satellites. Such satellites will study climate change, track migratory animals, endangered species, icebergs, volcanic eruptions and forest fires, and aid in search and rescue operations.
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