Voyager Probes Give Us ET's View 166
astroengine writes "For the first time, scientists have been able to measure a type of radiation streaming out from the Milky Way that in other galaxies has been linked to the birthplaces of young, hot stars. There was no way to make our own galaxy's measurement of the radiation, known as Lyman-alpha, until the Voyager probes were about 40 times as far away from the sun as Earth — any closer and the solar system's own emissions drowned out the fainter glow from the galaxy."
Question About Voyager(s)... (Score:4, Interesting)
Re:Question About Voyager(s)... (Score:5, Interesting)
I don't think it's encrypted, but I think the methods of encoding the transmissions are incredibly arcane and the formats for the data are nothing even approaching standard (standards for such things didn't exist back then). Probably more important is that the only radio receivers in the entire world that are capable of detecting its signal are run by NASA...
Re:So Cool... (Score:5, Interesting)
The Voyager computers are awesome [nasa.gov] too. How many other 18-bit word [nasa.gov] systems are actively maintained [space.com] today?
I'd love to see the source code, though I'm sure it's terribly boring.
Re:Question About Voyager(s)... (Score:5, Interesting)
In the linked article I didn't find that "only three" such antennae exist. The deep space network made of three big antennae is able to follow and control Voyager without interruption, but other isolated and big antennae exist and might be used to perturb the spacecrafts, probably with slight modifications.
Germany has a 100 m radiotelescope (Effelsberg), UK a 76m one (Jodrell Bank), Australia a 64 m one (Parkes), and China builds a 300m equivalent one, FAST, to be ready in 2013 (http://en.wikipedia.org/wiki/Five_hundred_meter_Aperture_Spherical_Telescope).
Re:Impressive (Score:5, Interesting)
The distance at which the Voyagers are still collecting and transmitting useful data back to Earth, is mind boggling.
Over a light day away! [nasa.gov]
Back in 1989, when Voyager 2 flew past Neptune, the JPL command center was probably dismantled and refitted for the next glamor project, while the long final phase of the Voyager mission was relocated to a much tinier space, probably the basement, with a couple of old-school, hardcore Voyager geeks down there, living on Doritos, pizza and Usenet, a rickety AC rattling and slowly dripping water over a puddle, unfixed for months because the Maintenance Department is constantly needed up at Voyager's old stomping ground, kept immaculate for the Galileo probe people, or Cassini, or the Mars Rovers, whatever the Flavor Of The Lustrum [wikipedia.org] was / is.
Nice and quiet down there among the rusted ceiling pipes and aged Crays, though. They didn't bother nobody, nobody bothered them. Beer could be smuggled to work and no one would notice, everybody upstairs would be swooning over Neil DeGrasse Tyson filming a segment on Pluto and the Horizons mission. Only time anybody saw the strange Voyager geeks, was when they went up to the ground floor vending machines, as the supply guy always forgot to restock the one in the JPL basement, forgot there was one in the basement.
Little did anybody know (except for these guys) that the Voyagers were like an aging boxer with one good fight left in them, very low bitrate coupled with an ultra-weak signal perhaps, but with still one final, grand potential payoff - a peek at the outside, which may end up being the longest lasting legacy of all.
Look at it now bitches, it's on the other side of the heliopause!
Re:30 years later... (Score:5, Interesting)
Oh [nasa.gov], I don't know... electrostatic ion propulsion is already proven to be more efficient than ordinary chemical propulsion (once you get out of the gravity well).
As long as you have fuel, you'll keep accelerating, albeit at a very small rate. It might take ten or twenty years, but I reckon that if an ESI probe was launched tomorrow it'd overtake Voyager and still have propellant to go faster.
The bonus is with computer technology; that while it's gotten thousands of times faster in practically every respect, it's also gotten a lot smaller [intel.com] - a non-hardened computer package these days weighs no more than 3lb [wikipedia.org], with terrestrial ruggedised coming in at little more [toughbook.eu]. The advantage of this is obvious: with the single biggest non-fuel component of the spacecraft now the size of a paperback, you have far less mass to push.
Of course, you don't need a screen or a keyboard in deep space, so cut the weight in half and you've got something a smidge lighter than the several hundred pounds of GE custom machine that went up with Voyager, that has its own battery, that pulls about ten Watts rather than over a hundred, that uses solid state storage, and in most cases can automagically govern its own power load (this would be why the later Shuttle missions used self-contained laptops rather than a room full of mathematicians and radio that meant data moved at the speed of speech) - I've metered my netbook off the line and found it runs on between 3-35W, averaging 11, including the screen on minimum brightness.
That said, you do need to protect the computer against hard radiation. That will obviously push the weight up, but not so much as to make it unmanageable. A couple or three pounds of lead and a steel cage to protect against EMI/RFI I think is all that is needed. The major part of the probe is then going to be propulsion systems and fuel, and the science package.
Re:30 years later... (Score:5, Interesting)
The costs of space technology haven't changed much at all relative to the rate of inflation
When you get away from government projects and missions you find an interesting thing. They've gone down in absolute dollars. It's not rare to find private analogues which cost an order of magnitude or more less than the government counterpart.
For example, prior to the early 80s, there was no commercial space flight of any sort. When it first opened up with offerings from Arianespace, Boeing, and Lockheed, prices were on the order of $20k per kg (to low Earth orbit or "LEO"), a bit better than the Space Shuttle. Now there's perhaps a dozen private space launch providers, some offering flight costs well under $10k per kg. So we've gone from $20k per kg in 80s dollars to under $10k per kg in today's dollars. And if SpaceX delivers, we'll be hitting $5k per kg (in today's dollars), perhaps less. The Russians have a good chance of meeting that price point as well.
It'll never be a Moore's Law thing, but we are seeing a remarkable long term decline in launch costs over a few decades. So no breakthrough in launch technology (with the exception of the creation of commercial space flight in the 80s and the possible exception of SpaceX now) yet we still manage to drop prices considerably even before adjusting for inflation.
Second, there are great economies of scale in launching tens of probes. For example, R&D is divided up over a large number of probes. There are learning curve effects from building tens of probes and part costs will go down. Now maybe building a Voyager-level vehicle wouldn't be as cheap as the original poster claimed, but I bet $3 billion can buy a lot of interstellar probes, just the same. Especially, if one cuts out the slick tools that Voyager used for its planet flybys, but which weren't used for the interstellar portion of the mission (such as the imaging cameras).
Re:30 years later... (Score:5, Interesting)
They wouldn't be using state of the art chips, but even the old radiation hardened chips needed for space travel would be an big improvement over 30 year old technology.
Probably the biggest improvement would be in propulsion. Isn't this the exact sort of mission the new ion propulsion systems would be perfect for?
Re:Question About Voyager(s)... (Score:4, Interesting)
Obvious troll is obvious
No... you're just dumb. I've always wondered this, too. Not just about Voyagers, but all space exploration probes. No states have an interest in sending these false commands, but I wonder if it is possible or practical.
:)
Edit: I just reread the grandparent's reply, and the way he posed the question makes him out to be an idiot. I won't suggest modding him up, but his question is at least valid. Anyone know about how secure communications with space probes is accomplished?
Re:Question About Voyager(s)... (Score:5, Interesting)
It's not just single large antennae that can be used to detect signals from Voyager.
The VLA uses technology developed in Britain (actually, a quirk of physics) to use several small antennae to simulate one large antenna. You can do the same, using similar frequencies to those used for the Voyager downlink (2.3GHz), a few lengths of coaxial cable, some one and a half inch nails, and four feet of marine ply.
1. Set two nails in the ply a set distance apart, call this distance D. You'll need this.
2. Connect each nail to its own demodulator (AKA receiver), then connect the receivers to a phase correlator.
3. Set the phase correlator to cycle the sinD differential between the two signals.
4. Take the output to a computer for decoding.
It is possible to do the phase correlation on the computer, or simply use the computer to record the signals from each receiver (forgetting about the phase correlator altogether) and combine them later. If you're dealing with streaming data (like you would be if using WiFi) you'll need a phase correlator* or set sinD as close to zero as you can get it (by setting the nails in the case of WiFi at multiples of 1.21"/30.734mm apart - as far apart as you can get them).
*There is a way around this, but it also requires precise angle measurement. If you know which direction your signal is coming from, you can point your interferometer toward it (the elements set exactly perpendicular to the signal source so they receive the signal in precise phase alignment). It helps if the interferometer is mounted on a common axis as this does away with the need for a phase correlator.
An improvement on this extremely simple design is the use of "cantennas" or other narrow-field antenna, which develops a narrow but high gain cone for the receiving antenna, making life a bit easier for finding the transmitter. If you want to get ambitious, the VLA uses 27 antennas, a 21+21+21km 3-way rail baseline, and several supercomputers.
Re:Question About Voyager(s)... (Score:5, Interesting)
40 times as far away? (Score:4, Interesting)
Um, no. (Score:4, Interesting)
You're confusing antenna angular resolution with antenna effective area. The problem with reception of the Voyager probes isn't being able to discern them among other relevant signals. The problem is that the signals are so weak that they need an antenna with large area just to collect enough energy per bit to reliably overcome noise generated in the receiving system. Until you do this, you can't get a signal strong enough for your correlator to work on -- all you'll get out of the correlator is noise, because that's all that's going in to the correlator from your receivers.
Ergo, the 70m dishes.
Re:Question About Voyager(s)... (Score:5, Interesting)
Not that anyone is probably interested but I worked in the group that made the radios that are in Voyager. I just missed working on those specific models but I worked on the next generation following those use on Voyager. Working there (Motorola GED) I worked close with NASA and was in the loop on all the programs, past and current that we were working on with NASA. What is really remarkable here is both Voyager probes have "failed" receivers on them. There was a problem with the capacitors that were used for the input loop bandwidth filters. These failed in such a manner as to cause the acquisition loop bandwidth to be a very narrow band instead of the intended wide band. NASA was able to recover using these radios by basically making an empirical model of each of the spacecraft. They did this when the spacecraft were relatively close to the earth and they could blast them with wideband signals to ensure acquisition. What they did with the model was to identify exactly how the on board xtals in the radio aged or varied with power and temp and then threw in compensation for age and doppler. With all of this data then then had a model that told them on such and such a date, the correct xmit frequency to use to put the carrier in the middle of the narrow band filter is X. They would dial it in, send it out and everything still worked. Actually a very clever fix for what would have been a disaster.
Re:30 years later... (Score:2, Interesting)
My understanding is that the noise from radiation only became a significant problem with newer chips running at lower voltages. The radiation shielding is a better solution for better systems, but ironically the old technology wasn't good enough to have this problem. Older logic systems (eg TTL but possibly not in this case) were designed for noisier, less stable circuits in general and radiation in space just happened to be just the sort of interferance it could tolerate.