China Launches World's First Pulsar Navigation Satellite (ibtimes.com)

hackingbear writes: After launching the world's first quantum communication satellite this year, China today successfully launched the world's first pulsar-based navigation satellite (Warning: may be paywalled, alternate source), which will conduct in-orbit experiments using pulsar detectors to demonstrate new technologies. The X-ray pulsar navigation satellite XPNAV-1 was sent skyward at 7:42 AM (local time) atop a Long March 11 solid-fueled rocket from the Jiuquan Satellite Launch Center in China's northwest. China's new system is expected to be a significant improvement over the earth-based systems currently used by spacecraft as it would eliminate the time delay with sending signals back to Earth and processing.

Comments

Didn't know pulsars got lost

[I'm New Around Here]

Pulsars! How do they work?

Re:Didn't know pulsars got lost

[Anonymous Coward]

Hey, I had to wake up to respond to this!
BeauHD is usually clueless, and indianexpress isn't much better...

Let's put it this way:
China... I've worked with their Physicists for decades; their worst are pretty bad, but their best are pretty fucking brilliant.

One major problem with Navigation Satellites is with an agreed upon Earth-Based Time Standard. There are many artificial and recently patented ones, but Pulsars are pretty good as an alternative; they aren't patented, and they have been around for a very long time, and very far away. On top of that, they for all intents and purposes, can't possibly be knobbled.
Another little bit of good news in a week that so desperately needs some.
Not bad, China.

Not bad, at all.

Re:Didn't know pulsars got lost

[K. S. Kyosuke]

It will blow your mind, but they're basically giant magnets. Now we've reduced it to a known problem, so you know what to do next.

the real news is china has launched and inter

[Anonymous Coward]

-steller mission ...

sorry no that is not true so this even if it where true is totally useless

polls?

[MancunianMaskMan]

From TFA:

X-ray pulsars consist of a magnetized neutron star that draws gas from a companion normal star, forming a rotating disk that channels the gas to its magnetic polls, resulting in the generation of intense energies

hope they get these right...

Eliminate the time delay?

[fredrated]

How can they do that when they are still limited by the speed of light?

Re:Eliminate the time delay?

[Anonymous Coward]

For the same reason you can eliminate your commute time by working from home. The speed limits no longer matter.

Re:Eliminate the time delay?

[dinfinity]

FTA:
"The X-ray pulsar captures X-ray signals emitted from pulsars. By mapping those signals, they can be used to determine spacecraft location in deep space, which will eliminate the hours-long delays incurred in using ground-based navigation like the Deep Space Network and European Space Tracking network." (my emphasis)

Re: Eliminate the time delay?

[Anonymous Coward]

well, it's taken into account.

baically it's just using pulsars as gps satellites to figure out where it is.

or something. it's not glonass or gps.

Re:Eliminate the time delay?

[bruce_the_loon]

At the moment the spacecraft need data fed to them from Earth about their position and that takes time because of the speed of light.

With this system, the spacecraft itself can calculate its position using the pulsars as if they were GPS satellites. So no delay caused by the comms to and from Earth.

Re:Eliminate the time delay?

[Sir Holo]

FTA:
"The X-ray pulsar captures X-ray signals emitted from pulsars. By mapping those signals, they can be used to determine spacecraft location in deep space, which will eliminate the hours-long delays incurred in using ground-based navigation like the Deep Space Network and European Space Tracking network." (my emphasis)

Replying here because it's highest-Modded.

This is a brilliant way to coordinate deep-space travel. Pulsars have not only a known position, but also a know frequency of pulsing.

Man, do I wish I had thought of this! It's nominally just like GPS, only using the periodicity of a known pulsar, rather than a human-launched GPS satellite. Genius!

Re:Eliminate the time delay?

[coastwalker]

This launch is also to characterize the x-ray pulsar data as the signals cannot be studied from within the shielding atmosphere. It is unlikely that there is enough data currently to make the position calculation reliable.

Re:Eliminate the time delay?

[CanEHdian]

Well, the Voyagers carried plates that showed the elative position of the Sun to the center of the Galaxy and 14 pulsars, so there pulsars were already linked to position in deep space (from the aliens point of view).

Re:Eliminate the time delay?

[Anonymous Coward]

Man, do I wish I had thought of this! It's nominally just like GPS, only using the periodicity of a known pulsar, rather than a human-launched GPS satellite. Genius!

There are some differences from GPS satellites. A GPS bird does not send a completely monotonous signal. They actually tell time. So comparing to a known good clock, you immediately know the exact distance to that satellite. A few more satellite distances, and you have a fix.

A pulsar does not tell time. If you observe it continously, you can use deviation from the completely monotonous signal to infer that the spacecraft has moved towards or away from the pulsar. So you can start with a known position (earth) and add up changes for a few pulsars. That gives you a position. But don't reboot or anything - if the reference timing is lost, you won't get it back! Quite unlike GPS . . .

Re:Eliminate the time delay?

[dj245]

FTA: "The X-ray pulsar captures X-ray signals emitted from pulsars. By mapping those signals, they can be used to determine spacecraft location in deep space, which will eliminate the hours-long delays incurred in using ground-based navigation like the Deep Space Network and European Space Tracking network." (my emphasis)

All good stuff, and it has many practical peacetime applications. I wonder about how much of this technology can be applied to military hardware. We often forget that the space race is often at least 50% military in nature. Could the same sensors detect nuclear detonations on earth? Could the navigation method be a useful secondary method for ICBMs to navigate in addition to other guidance systems?

Re:Eliminate the time delay?

[Anonymous Coward]

A mistake. A _grave_ mistake.

Re:Eliminate the time delay?

[Solandri]

Basically, pulsars "transmit" all the time. Coordinating signals from Earth are only transmitted as needed, so there's a delay due to the speed of light.

Re:Eliminate the time delay?

[SNRatio]

if time delay is an issue then "as needed" means continuously - and thus no time delay so long as you have enough stations broadcasting.

NASA NuStar 2012

[Anonymous Coward]

You realize that their satellite didn't use quantum entanglement and didn't communicate anything. Nor will it, because the 'successful entanglement' filtering signal needs to be sent separately by other means. Nor will it ever do anything useful, because the 'successful entanglement' signal is sent using whatever traditional encryption is available. So what you actually have is nothing more secure than a line of sight laser.

Article suggests its a pulsar detector for radioastronomy, for space probes to use these pulsars for navigation. And its certainly not the world first, e.g. Nasa NuSTAR is an x-ray space based telescope for looking at pulsars.

Re:NASA NuStar 2012

[Impy the Impiuos Imp]

Maybe they detected alien signals that can only be found outside the atmosphere from the pulsars, and don't want anyone knowing!

Re:Boycott US goods.

[mukinrestak]

What US goods?

Re:Hooray to china

[Anonymous Coward]

At least they're launching. What you got?

Re:Boycott US goods.

[stealth_finger]

American cheese?

the real annoyance is

[stealth_finger]

people who start their comment in the subject box.

Re:Boycott US goods.

[50000BTU_barbecue]

Weapons and comic book movies?

Re:Boycott US goods.

[amalcolm]

American cheese? Isn't that an oxymoron?

Re:Boycott US goods.

[Anonymous Coward]

It is good to know that the whites can pull together to repair the country. Trump 2016!

Maybe orientation, but not distances

[Laxator2]

Pulsar navigation may allow to determine the direction in which the spacecraft is traveling, but not the actual distance from Earth, unless the spacecraft has traveled very large distances.

A simple example. Last time I checked, Voyager1 was 18 light-hours away from Earth. Now Alpha Centauri is 4 light-years away. Multiply 4 by 365 and then by 24 and divide by 18.
That tells us that Alpha Centauri is about 2000 times more distant than Voyager1.

Put two dots on a blackboard, 2 meters apart. The dots represent Earth and Alpha Centauri. Then Voyager1, the spacecraft that has traveled farthest from Earth, is a full 1 millimeter away from the Earth point.

The closest pulsar to Earth is at an estimated distance of about 250 light-years. The pulsars will be very useful to find the direction, but for distance timing radio signals from Earth to the spacecraft remains the best method.

Re:Maybe orientation, but not distances

[Anonymous Coward]

You are right, but distance to earth is not really an issue, because you can measure it integrating any doppler offset, or, if you have a precise time base on board (you'll need it to distinguish the pulsars anyway), you can infer the distance from telemetry timestamps (works in both ways, for satellite and station).

Of course you can mash up with other measurements.

Cheers.

Re:Maybe orientation, but not distances

[Anonymous Coward]

You're wrong about a few things:
- Pulsar navigation can determine distance traveled along a pulsar's direction, which is a lot more information than just the direction it is traveling.
- The distance of the pulsars doesn't matter, the sharpness of their signal does.

If you can detect a particular spot on the pulse curve to within 16 microseconds, then by counting pulses since a known position, you can compute the distance traveled along the pulsar direction to within 5 km, which is typical for the most accurate pulsars. By triangulation with many pulsars you can compute your X,Y,Z coordinates in space. The X,Y,Z coordinates are the end product you wanted in the first place, not the distance from Earth which was a means to that end. If for some strange reason the spacecraft needs the distance from Earth, then it can always subtract its coordinates from a mathematical model of Earth's orbit.

Editors why can't you write a decent summary

[Anonymous Coward]

Dear editors, please write better summaries.. Something such as below is much more informative...

China today successfully launched the world's first pulsar-based navigation satellite. The X-ray pulsar navigation satellite XPNAV-1 was sent skyward at 7:42 AM (local time) atop a Long March 11 solid-fueled rocket from the Jiuquan Satellite Launch Center in China's northwest. Pulsar navigation allows the satellite to determine its position in space by using the periodic signal emitted from pulsars, much like earth-based GPS. This will eliminate time delays incurred using ground based navigation.

Re:Editors why can't you write a decent summary

[Big Hairy Ian]

Mod Parent Up

Re:Editors why can't you write a decent summary

[Solandri]

The more interesting aspect of this is that pulsars are effectively an interstellar GPS. If we ever become a space-faring race, they're going to be crucial for interstellar navigation. The beam a pulsar emits from its poles is highly directional, so sweeps out the surface of a cone in space as the pulsar spins. As you travel through space, your "home" pulsars will fade out of view while new ones become visible. In that way, you can use the signal from 3 known pulsars to fix your location to a certain section of space (intersection of three cones). The more pulsars you can see, the more accurately you can refine your location.

Re:Editors why can't you write a decent summary

[Anonymous Coward]

i have an autistic nephew who likes cones, and he will line them up and count them for hours. we bought him a cone-shaped inflatable ball pit for his birthday this year and he was ecstatic.

Re:Boycott US goods.

[Big Hairy Ian]

American components, Russian components all made in Taiwan!

Telcom

[gaiageek]

Isn't that the satellite that's raining debris all over Eur... err, Myanmar?

Re:Boycott US goods.

[Anonymous Coward]

American components, Russian components all made in Taiwan!

That reference tho!

You don't have a supercomputer in space

[Laxator2]

The problem with relying on the timing of the pulses is dispersion of the wave packet in interstellar space. Keep in mind that these signals travel hundreds of light years trough interstellar space, which is by no means a perfect vacuum.

Sometimes entire pulses are missing from the signal. Pulsar study groups use computer clusters for the sole purpose of reconstructing the original form of the pulse. For example, the one at McGill Univ. was student-built, but it made it to the (bottom of the) Top 500 list at the time it was built.

A spacecraft has very limited computing power, certainly not of the magnitude required to reconstruct pulses. The signal is very dirty, it would be a bad idea to rely on its timing. The pulses are very regular, "when the signal is good".

Re:You don't have a supercomputer in space

[Anonymous Coward]

Reconstructing pulses from first principles, for purposes of understanding what the pulsar is doing or mapping out the stuff between us and the pulsar, does take a lot of computational effort. That effort is not needed for navigation purposes, as the stuff between the pulsar and us changes very little on human timescales. All that is need is some characterization of the relative timing of different pulsars, which is the exact purpose of this satellite. The computational effort for implementing it on future probes is then pretty minor.

Iridium

[hduff]

Are the Iridium sats still up there and working?

Re: Hooray to china

[Anonymous Coward]

What do I got? This was a satellite launch. The US has no less than 3 providers of launch capability for this kind of mission.

Idiot.

Thanks for signing your name but it really wasn't necessary.

im a bit worried

[KingBenny]

This is the second time today my pc reboots when im reading an article on why the chinese understand the need for space a lot more than the leaders of the free world, i live in europe myself and dont worry, i wanna move to mongolia, not china (less humans per square metre there).
so .. .my battery has been charging all day too and the led is still on, is that you, drill ?
or the trump squad ?
or zee russians perhaps ?
cos as far as i see it , according to euh whats her name colonel corazon santiagos granddaughter, the apex of military power no longer rests at airpower
it rests in outer space so if you want your arms race
MISTER president
i suggest you race the chinese to space first
thank you, dont ddos me