[time-nuts] Satelles PNT from Iridium satellites

Mon Aug 10 16:10:24 UTC 2020

I did attend those conferences, it was my first ex poser to Dual Mixer, NIST presented it for high precision frequency measurements. Still have copies of the proceedings.Time is and was key but I do not recall any papers addressing using GPS for time distribution as we know it today, and that is what I was responding to the question that I answered to. Also writing the proposals and attending all project reviews it was never covered. Bert Kehren   In a message dated 8/10/2020 10:48:12 AM Eastern Standard Time, kb8tq at n1k.org writes: 
Hi

>From what I saw as the system was developed, the people doing it realized that timing
was at the core of the design. If there was a timing problem, nothing was going to work.
There were GPS (and before that other sat-nav) presentations at the Frequency Control
Symposium for many years. The “big boys” in timing all were involved in GPS one way 
or the other. 

NIST was doing time transfer work on GPS before the system was fully up and running. 
Their results are (to a great degree) what got everybody believing  that GPS *could* 
be a good source of time. Those papers started early and kept on flowing …. Until they
put their “stamp of approval” on the technique, I don’t think anybody was ready to call it
a super time source.

This is by no means to imply that NIST was the only outfit involved or that the others
who also evaluated GPS somehow did not contribute. That’s far from the case. The only
point is that NIST got out there early. 

Bob

> On Aug 10, 2020, at 5:09 AM, ew via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Attached are two pictures from my TI days as program Manager of the first GPS. There was no discussions of consumer use or timing application. Focus was on military application being able to guide a bomb in to a chimney. The cost per device was $ 300 000. Because of my high security clearance I was asked to brief the NSA and CIA on the future of GPS equipment. With my semiconductor background Moores Law and previously involved in consumer calculator development I predicted the size of a brick and $ 3000.  I was declared the company Idiot lost all credibility as a strategic thinker ans subsequently left TI. When Magellan came out with there handheld unit they remembered me and send me one. Still have it. When two years later the units the size of a cigarette pack came out and where given away if you took a Cadillac test drive the asked for it back. I refused. History.Bert Kehren    In a message dated 8/9/2020 11:23:33 PM Eastern Standard Time, time-nuts at lists.febo.com writes: 
> I've done some quick research.  I do not see timing as one of the services provided.  I wonder if it can be achieved by just listening into what's already transmitted (like GPS) and do some math on our side. 
> 
> On more broader sense, was GPS originally designed to provide timing service?  Or is it a byproduct of needing to measure location and speed, thus it needed a constant signal, and that using it to sync reference signal is just an ancillary and after-thought use cases?
> 
> --------------------------------------- 
> (Mr.) Taka Kamiya
> KB4EMF / ex JF2DKG
> 
> 
>    On Sunday, August 9, 2020, 9:21:23 PM EDT, Bob kb8tq <kb8tq at n1k.org> wrote:  
> 
> Hi
> 
> 
> 
>> On Aug 9, 2020, at 7:03 PM, Tom Van Baak <tvb at LeapSecond.com> wrote:
>> 
>> Hi Stu,
>> 
>> There's no problem with a semi-commercial posting here. You've been a member for a decade and frequent contributor plus the subject matter is exactly on-topic. So thanks for posting.
>> 
>> I spent a while on your web site and didn't uncover a trove of white papers. If you could post some URL's that would be appreciated. You don't have to worry about being less accurate than GPS. I mean, there are often far more important factors than nanosecond precision.
> 
> To that point ( as accurate as GPS ) ….. GPS is simply a convent comparison system. Saying that 
> this or that is better or worse at this or that tau is *not* the same as saying it has more or less value. 
> It’s simply a system that is out there to be compared to.
> 
> Bob
> 
> 
>> You didn't mention pricing; it's hard to imagine it's as free as GPS so that seems like another disadvantage to me.
>> 
>> Your comment about fewer satellites is spot on. That will be taken care of if you give SpaceX / Starlink a call and join that bandwagon. There are already 597 Starlink [1] satellites up there vs. 82 Iridium [2] satellites, yes?
>> 
>> If you have entry-level / hobbyist grade evaluation kits I'm sure a number of us would be very interested to try it out.
>> 
>> Thanks,
>> /tvb
>> 
>> [1] https://en.wikipedia.org/wiki/Starlink
>> 
>> [2] https://en.wikipedia.org/wiki/Iridium_satellite_constellation
>> 
>> 
>> On 8/9/2020 2:53 PM, Stewart Cobb wrote:
>>> Taka Kamiya and Forrest Christian both asked recently about the alternative
>>> satellite PNT system using the Iridium satellites. That system was
>>> developed by my company, Satelles. It has been commercially available for
>>> more than a year now.
>>> 
>>> The biggest advantage is that our signal is at least 30 dB stronger than
>>> GNSS signals (the exact numbers depend on whether you're talking to
>>> engineering or marketing :). You can easily get a usable signal in deep
>>> jungle, or a data center in the middle of a building's basement, or even
>>> inside a locked shipping container. The stronger signal is correspondingly
>>> more difficult to jam or spoof than GNSS, and our signal has anti-spoofing
>>> features as well.
>>> 
>>> The biggest disadvantage is that it is not quite as accurate as GPS,
>>> because there are fewer satellites in view at any given time.
>>> 
>>> I don't want to quote exact timing numbers here, because they depend a lot
>>> on system integration details, but you can easily steer an OCXO within a
>>> few hundred nanoseconds of USNO time. With a rubidium, you can do
>>> considerably better.
>>> 
>>> If you want to know more, our website is www.satellesinc.com.
>>> 
>>> (If this message has been too commercial, I apologize in advance. The
>>> boundary between information and salesmanship is not always sharp.)
>>> 
>>> Cheers!
>>> --Stu
>>> _______________________________________________
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>>> 
>> 
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