
Next-generation of GPS satellites are headed to space - dnetesn
https://phys.org/news/2018-12-next-generation-gps-satellites-space.html
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finnh
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](https://en.wikipedia.org/wiki/Quasi-
Zenith_Satellite_System)

~~~
walrus01
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.

~~~
moftz
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.

~~~
kevin_thibedeau
Sirius XM is now geo only.

~~~
moftz
Makes sense, those satellites are well past their scheduled lifespan.

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GolDDranks
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
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.

~~~
moftz
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.

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xvilka
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
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_orpheus
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...](https://en.wikipedia.org/wiki/Coordinating_Committee_for_Multilateral_Export_Controls)

~~~
mirashii
I would not say the cocom limits aren't enforced, any exportable GPS receiver
is required to have the cocom limits and needs a special license to unlock
under EAR regulations. This means that anyone building a cubesat and using a
commercial receiver has had to specifically get that exception.

~~~
dr_orpheus
You are correct, I did not mean to say that there are no more regulations on
export of GPS receivers. Yes you still have to obtain an EAR license for a GPS
receiver capable of tracking at > 600 m/s. But the specific CoCom limits are
at least relaxed since they specified that the GPS receiver will stop
functioning if velocity is > 1000 knots or the altitude is computed to be
above 18,000 meters. The latter part was restricting operation of high
altitude balloons which is why I believe there is only a restriction on the
velocity and not altitude now.

Sorry for the mixed units, but that is the actual wording from original CoCom,
for reference: 600 m/s = 1342 mph 1000 knots = 1150 mph

~~~
dylan604
>The latter part was restricting operation of high altitude balloons which is
why I believe there is only a restriction on the velocity and not altitude
now.

A group of friends and I did a ~90,000' balloon launch on the "cheap". We used
a consumer handheld GPS unit that reported it's location every 10 minutes to a
server we could keep an eye on. We suffered through the issue of altitude
limitations as well, but it was still better than nothing. Learned a lot of
stuff from that project. A big take away was using a mobile version of Google
Maps when using Lat/Long coordinates is not very accurate, as it seemed to
always want to put the location close to a road. When using the same coords in
the desktop version of Google Maps satellite view, the Maps' pin dropped to
within 3 feet of where the payload had landed. Using the mobile version, we
wandered around in the wilderness for an embarrassingly long amount of time
before I got fed up with it and though there must be a better way. Using the
desktop location, we were able too pretty much walk up directly to the
payload.

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root_axis
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
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](https://celestrak.com/NORAD/elements/master.php)

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bradknowles
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.

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miller_joe
> 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! =)

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

~~~
michaelt
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....](https://www.mitre.org/sites/default/files/pdf/betz_overview.pdf)

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

~~~
AWildC182
GPS signals are sufficiently low frequency that a phased array would need to
be fairly large. Each antenna in the array would need to be around 5cm and
you'd need quite a few of them on each axis. Totally doable but someone
probably decided a dish was easier/cheaper than a big board of antennas or
waveguides and associated circuitry. Phased array would be nice to have
though, since if the array was large enough you could have multiple beams
produced by different parts of the array and cover more/multiple areas.

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sonar_un
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.

~~~
Rebelgecko
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.

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Tech1
Hopefully the week field is longer than 10 bits. That was a headache.

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

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elfchief
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.

~~~
samnardoni
Well, yes, that's true. But my point was that they aren't going to change the
legacy nav data structure.

