NASA Probe Blasts 461 Gigabytes of Moon Data Daily

coondoggie writes "On its current space scouting mission, NASA's Lunar Reconnaissance Orbiter (LRO) is using a pumped up communications device to deliver 461 gigabytes of data and images per day, at a rate of up to 100 Mbps. As the first high data rate K-band transmitter to fly on a NASA spacecraft, the 13-inch-long tube, called a Traveling Wave Tube Amplifier, is making it possible for NASA scientists to receive massive amounts of images and data about the moon's surface and environment. The amplifier was built by L-3 Communications Electron Technologies in conjunction with NASA's Glenn Research Center. The device uses electrodes in a vacuum tube to amplify microwave signals to high power. It's ideal for sending large amounts of data over a long distance because it provides more power and more efficiency than its alternative, the transistor amplifier, NASA stated." It kills me that the moon has better bandwidth than my house.

Comments

This is not exactly a new device...

[Manuka]

Traveling Wave Tubes have been a mainstay of microwave communications and radar systems for the better part of a century. They're a very efficient way of amplifying microwave signals to the very high power levels needed to cross long distances.

Re:This is not exactly a new device...

[Lumpy]

You need an electron gun and some electron optics to make the beam,

Check, old 19" TV tube... all the parts are there.

and then the section where the RF interacts with the beam, either a helix or a series of coupled resonant cavities.

Again, can be found in other surplus tech.

but screw it, just buy one....

http://cgi.ebay.com/NEC-LD7306A-B61-Travelling-Wave-Tube-TWT_W0QQitemZ200255211587QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2ea0240843&_trksid=p3286.c0.m14

Re:Vacuum Tube?

[Andy Dodd]

When you need to make serious power, tubes are still the way to go. Transistors have a significant reliability benefit.

Also, for 99% of applications, transistors are better. For the other 1%, you have very application-specific tube designs such as TWTs and magnetrons, which rearrange the tubes in such a manner as to negate its usual disadvantage (large size USUALLY translates to nasty frequency limits - TWTs and magnetrons are exceptions that use various Neat Tricks to allow microwave operation from a large device.)

BTW, one of the other common microwave tubes (magnetrons), while it is a "niche" device, it is a VERY widely deployed niche - basically all microwave ovens use magnetron tubes.

Re:Spam

[Anonymous Coward]

Vacuum tubes have always had higher frequency limits than transistors, since WWII in fact. Take a look at THz radiation sources, all tubes. No tranny is going to touch that for a while. And then tubes will have gotten better too.
http://en.wikipedia.org/wiki/Backward_wave_oscillator
Tubes just have more geometric freedoms to create bizarre fields and strange structures to do whatever you need.

Re:Insane

[CecilPL]

Actually 10base is 10Mbps, or 1.25 MB/s.

5.46MB/s is close to half of a 100BaseT.

if not, the tube would be ruined before launch

[swschrad]

curious thing about tubes, they don't become useful until they're sealed in vacuum, and boiled out in a high RF magnetic field to take impurities off the elements. and then you have to flash the last of the gases off by igniting a getter inside the envelope.

that provides a higher vacuum on earth, inside the tube, than you can ever develop in space. and the electrons can do their work, instead of hitting stuff and just making a useless glow.