Next-generation of GPS satellites are headed to space

https://phys.org/news/2018-12-next-generation-gps-satellites-space.html

by dnetesn • 8 years ago

88 42 8 years ago

xvilka• 8 years ago

In a few years many GNSS (Galileo, BeiDou, GLONASS) will update (or complete) their fleet and software, according to the respective schedules. So consumer electronics that can work with all of them will increase location precision and accuracy drastically.

izzydata• 8 years ago

My work involves software testing consumer electronics with GPS and I always find it amusing when the requirement comes up that the devices should not be capable of accurately tracking position when traveling at 1200 mph.

I'm curious if Galileo will still have this limitation as I assume the purpose is not to be able to jerry rig long range missiles.

dr_orpheus3• 8 years ago

You are correct that the original intention of this (called the CoCom limit [1]) was to prevent use in ICBMs. The specific regulation was originally implemented to prevent GPS receivers with that capability to end up in communist countries during the cold war.

However, with the proliferation of small satellites and cubesats the CoCom rules are no longer really enforced. Many commercial GPS receivers still have them, but the regulations are different now.

[1] https://en.wikipedia.org/wiki/Coordinating_Committee_for_Mul...

JoeDaDude2• 8 years ago

If I understand correctly, GPS receivers are also (loosely) constrained by the Missile Technology Control Regime, a voluntary agreement between several countries not to export certain technologies applicable to missiles or UAVs.

http://mtcr.info/

https://en.wikipedia.org/wiki/Missile_Technology_Control_Reg...

finnh• 8 years ago

Also of note is Japan's Quasi-Zenith Satellite System[0], which finished placing its 4 satellites in October 2017. These provide GPS coverage from near-vertical angles over Japan at all times, giving accurate location fixes despite Tokyo's deep urban canyons. The geosync orbits designed for this are pretty cool.

[0] https://en.wikipedia.org/wiki/Quasi-Zenith_Satellite_System

walrus01• 8 years ago

Interesting to see they're using molniya orbits but for a very different purpose than the Russian telecom, military comms and broadcast satellites which most commonly use them.

moftz3• 8 years ago

It's not really that different of a purpose. You want at least one satellite visible in the sky, not on the horizon, nearly overhead. A highly elliptical geo tundra orbit gives you that overhead pass that a normal geostationary orbit can't give you. US Satellite radio (like Sirius) uses a tundra orbit with multiple satellites to cover the US and some parts of Canada and Mexico. You get max overhead time over the US with at least one satellite at all times so the connection is always good unless things on the ground interfere. Japan is doing the exact same thing as everyone else here.

deepsun• 8 years ago

It's not Molniya orbits. Molniyas are highly elliptical.

GolDDranks2• 8 years ago

As a Tokyo dweller, I'm also quite excited about the QZSS system which has a constellation of 4 satellites one of which is always in a near zenith position and provides a GPS signal even amidst the highest skyscrapers.

londons_explore• 8 years ago

The thing is... One satellite isn't enough to get a position fix... You need at least 4 (or 3 if you want a very rough position fix and are happy to assume your altitude = ground level)

So effectively, this QZSS system provides 1 extra satellite over what GPS would normally have visible - which is helpful, but really just an incremental improvement.

GolDDranks2• 8 years ago

Ah, dang. You are totally right. Well at least I welcome the incremental improvement. GPS sometimes really struggles where I work.

jamiek88• 8 years ago

Yes but that increment massively increases the utility on the ground so sometimes baby steps mean huge useability leaps.

mikeash• 8 years ago

The geometry of those satellites matters a lot, especially when you have tall buildings in the way. Always having one more or less straight overhead is a pretty big improvement.

moftz3• 8 years ago

QZSS adds one geosynchronous and three tundra orbit satellites so depending on where you are in the city, you could be seeing two or more QZSS satellites. It's not going to replace GPS but its going to help with getting a quicker location solution than not having it.

Something where you have beacons on every major intersection would be a better step for a city to introduce. The beacons would just be sending compatible messages so there is no need for additional hardware. If the roads are straight enough, you could see multiple beacons plus whatever satellite is overhead.

politelemon• 8 years ago

Can anyone shed some light on how this new setup will be more difficult to jam?

cwt137• 8 years ago

The article said the signal is stronger. That is the new anti-jamming countermeasure.

tialaramex• 8 years ago

Just broadcasting a similarly strong signal won't jam GPS family transmissions. This is because the transmission is based on a pseudorandom bit sequence. It looks like noise unless you also know what the pseudorandom sequence should be. If you do you can pick this out from any not related signal trying to jam it, until the jammers pour in so much more power that it overwhelms your receiver.

The new birds know a pseudorandom sequence that was state of the art ten years ago rather than forty years ago (times approximate). This is a shared key system. If you either break the system or know the key, you get position data or can effectively jam it. You can put several transmissions on the same bird, and give away some of the keys, voila you're a public service. Keep one or more for your military and they've got position information that can't be jammed.

dr_orpheus3• 8 years ago

The new block of GPS satellites contain a new acquisition code called M-code. It is an encrypted code from the GPS satellites that allows military receivers to still be able to perform positioning if the regular coarse acquisition (C/A) code (what we all use) is being jammed.

In the current GPS setup there is already an encrypted code (called P-code) but it often requires the GPS receiver first acquiring on the C/A code before being able to track solely on the P code. By contrast, military GPS receivers will be able to lock directly on to the M-code without any coarse acquisition.

https://en.wikipedia.org/wiki/GPS_signals#Military_(M-code) https://www.gpsworld.com/the-promises-of-m-code-and-quantum/

michaelt• 8 years ago

1. Adds a new directional 'spot beam' that can provide a 20dB signal boost (100x power boost) in a target region several hundred kilometres in diameter.

2. A new(-ish) military signal, the 'M Code', which is present on some but not all satellites from Block II. It has a number of features including [1]:

* Secretive design.

* Much wider bandwidth than civilian C/A code, meaning wideband jamming needs more energy.

* Power distribution different to the civilian C/A code, and unlike the older P(Y) code doesn't need the receiver to acquire the C/A code first, so less impacted if someone jams the civilian C/A code.

* A more modern spread-spectrum design (from 2000 rather than 1973) that provides better noise immunity and forward error correction, and hence better jamming immunity.

* The parts of the spread-spectrum design that rely on the transmitter and receiver having a common source of pseudorandom data use more modern cryptography.

[1] https://www.mitre.org/sites/default/files/pdf/betz_overview....

toomuchtodo• 8 years ago

Interesting that the spot beam is not phased array, but a parabolic dish on the satellite body.

Tech1• 8 years ago

Hopefully the week field is longer than 10 bits. That was a headache.

samnardoni2• 8 years ago

Erm, they aren’t going to change the nav data.

elfchief• 8 years ago

Untrue. There's a newer format for NAV data -- CNAV. It's currently broadcast on the L2 and L5 bands, and does indeed include a larger week number field -- 13 bits to be exact.

tatersolid• 8 years ago

Why would a GPS satellite broadcast anything other than TAI in nanoseconds?

I don’t know anything about GPS coding, but it would seem that anything calendar related like “weeks” is best left up to the receiver.

root_axis• 8 years ago

Slightly off topic, but is there any research going on regarding how to manage all the satellites being pushed into orbit? What happens when these things start to collide with other satellites or other trash accumulating in orbit? Is there a practical limit to what we can throw up into orbit before we start to see some adverse consequences?

trothamel• 8 years ago

It's more regulation than research. The idea of a Kessler cascade (where debris collides with a satellite, causing more debris, causing more collisions) is well known, and there is a lot of work to avoid it.

This means everything from eliminating things that might be jettisoned from rockets (like the despin weights on the upper stage of the Delta II), to deorbiting rocket boosters, to designing stages and satellites to fail safely without causing debris.

One of the more interesting things is the design for SpaceX's new Starlink satellites, which will be in a low enough orbit that they will deorbit within a few years if one fails. (If not, they can boost themselves into higher orbits.)

The other thing that helps is that there are only 43,864 objects large enough to track ever launched, and Only about 18,000 of them are still up there. While that seems like alot, that's the number of people at a baseball game, spread out over an area larger than the surface of the earth. (And even larger in volume.)

https://celestrak.com/NORAD/elements/master.php

jandrese• 8 years ago

The Kessler syndrome is not a concern for geo orbits for a couple of reasons. One is that there is so much more space in geo orbits that the odds of collision are even more rare. The other is that everything in Geo is more or less moving at the same speed in the same direction. Unlike LEO you don't have satellites flying with intersecting orbits.

JoeDaDude2• 8 years ago

The ESA has written guidelines for the responsible disposal of end-of-life satellites, and created this short film to illustrate the concepts.

http://www.esa.int/spaceinvideos/content/view/embedjw/484820

miller_joe• 8 years ago

But some of their most highly touted features will not be fully available until 2022 or later because of problems in a companion program to develop a new ground control system for the satellites, government auditors said.

Hey, maybe they need AWS GroundStation! =)

bradknowles• 8 years ago

So, I worked for six months as a subcontractor on the Raytheon GPS OCX project, but only the unclassified stuff.

We helped them take their datacenter deployments from a matter of months to a matter of hours -- using Chef. Once it's all powered and racked and stacked, we got the base OS plus the core apps and their configurations deployed very quickly. Towards the very end of the time I was there, we did a demo on a virtual datacenter that literally took just about three hours to execute from start to finish.

Definitely one of the projects that I am proudest of working on.

One of the things I heard many times while I was in Colorado was that the Lockheed guys got the easy job -- all they had to do was design and launch new birds.

The Raytheon guys said that they had gotten the hard job, because they had to handle all ground control operations for the current fleet of satellites, plus all the ground control operations for the new fleet of satellites.

And the Raytheon guys were pretty proud of that fact.

sonar_un• 8 years ago

How many satellites will be needed to be operational? What’s chips are comparable with the new bands? I know that there is currently only one phone with the Motorola chip, the Huawei P20 Pro.

How long until the satellite launches will it be operational after the tests? I couldn’t seem to find any of this information anywhere. Just basic press releases.

Rebelgecko2• 8 years ago

The only new signal (which I think isn't actually on a new band, it uses the same frequency as an existing signal) won't be online until 2020something when the new ground station software is ready. It may be a while before cell phones ship with chips that actually use the new signal. The L5 signal has been broadcast since 2010 and I think it took until this year for the first phones to ship with support for it.

Next-generation of GPS satellites are headed to space

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