[time-nuts] Time and frequency practical exercise 2018 late quarter; precision measure of 432mhz band Sat in Lunar Orbit

Bob kb8tq kb8tq at n1k.org
Fri Nov 17 18:54:11 EST 2017


> On Nov 17, 2017, at 4:26 PM, Patrick Barthelow <apolloeme at gmail.com> wrote:
> From me, Pat a newbie, second post:
> A new project, STEM opportunity.   A STEM/CitizenScience/Ham Space Science
> project. Kids welcome.
> In formative stages so this is for internal discussion, not for public
> announcements yet.
> Will do a frequency measurement of a Cubesat at about 437 mhz that will
> orbit the Moon in 2018.
> Can be received by modest yagi antennas while orbiting the moon.

That sounds like a pretty high ERP … Of course your definition of a modest antenna
may not be quite the same as mine :) Consider that there *are* SNR implications 
when you get into your accuracy requirements below. 

> Challenge is to get/use/build precision frequency references and counters,
> and measure the carrier frequency.    Cesium, Rubidium,  MASER, GPS based,
> commercial standards, and their derivations all welcome.
> Have found 4 (and More)  more hydrogen line masers in diverse locations
> around the world, who wish to participate.
> USA, Netherlands, South Africa, Australia, Mexico, and other locations have
> expressed interest.
> I am a member of  Team Alpha Cubesat.  We and some other teams are in the
> NASA CUBEQUEST challenge.  Launching next year a 6u  cubesat to lunar
> orbit.  I am not an expert at the freq measurement aspect of this, so, I am
> a Newbie. With tons of questions, but  I was surprised how quickly a check
> of the world's Hydrogen line MASERS got many to offer to come on board.
> MASER is overkill, but that is OK.

The MASER is a cute device. It is not an accurate device by it’s self. It is a 
very *stable* device. Yes, that is a subtle distinction. In this case I think it is
a pretty important one. 

>  The Chief Scientist of the project is
> in the USA and wants to make measurements to the HZ level, at 437 mhz so
> with MASERS and Cesium, Rubidium we are overkill but it could generate
> STEM/Citizen Science participation.  That is what we are doing.  So the
> satellite will be on 437.5 mhz  plus  minus doppler.  We have to measure
> its received freq to 1 HZ or less.

Ok, 1 Hz at 437.5 MHZ is roughly 2 ppb. That is pretty much “slam dunk” accuracy
with a GPSDO. Much easier to obtain and set up in a school environment. The
key will be orbit estimation for the +/- doppler part of it.  Orbit estimation is not
quite a slam dunk sort of thing. The GPSDO would also give accurate location.
Even with good orbit data, the solution still requires a good location estimate.

>   So I talked to the chief scientist,
> and we decided to go with a public STEM related program

I’ve been down the road (from scratch to running) on STEM competitions. The
KISS principle is one to keep in mind. At the same time you *do* want a topic
that presents a challenge. 

>  with it. [PLEASE

This *is* a public list, it’s “out” now. 

> this is confidential for now.] Announcement of a
> competition for anyone to measure the frequency of the sat as it is in moon
> orbit.  So I decided to check with  about 5 geographically diverse located
> MASERS. ( Australia,  South Africa, UK, Holland, Mexico and USA,  and got
> or am getting buy-in from them to make the measurement.  I was surprised
> they did not just say go away... a half million dollar MASER is, or should
> be busy with similar but necessary measurements from paying customers.
> Overkill, I admit, but it is a chance for Citizen Science publicity,
> Popular Science, STEM, etc..
> Anyway I got a bunch of MASERS  to participate and will develop a website
> for people to measure the freq and send in their "answer".  We will have
> (are looking for) sponsors that will pay prizes or wall paper awards,  for
> very close accurate measurements.
> This is like a modern day Frequency Measurement Test that ARRL did years
> ago.  I will in fact call ARRL to see if they want to play in this.  I will
> CC others to see if they want to play.  Other frequency references used may
> be commercial variations of
> Cesium Beam and Rubidium references.  But the King Kong in accuracy is the
> MASER.  I got to learn a bit about the MASER they had at Arecibo when I was
> there.   And now know a school in Europe a Technical Instrumentation
> school, that offers a project to build a Hydrogen Line Maser using modern
> simpler, cheaper methods and hardware.
> Arecibo may play on this event next year.   So, you only need modest yagis
> to pick up the Sat at moon distances  on 437.5 mhz  should be fun...
> ​The Goldstone MASER; above:
>> https://www.nist.gov/pml/time-and-frequency-division
>> https://www.nist.gov/pml/time-and-frequency-division/radio-stations/wwv
>> http://tf.nist.gov/stations/wwvtimecode.htm
>> https://www.nist.gov/pml/time-and-frequency-division/time-se
>> rvices/history-radio-station-wwv
>> https://www.nist.gov/pml/time-and-frequency-division/time-se
>> rvices/wwv-and-wwvh-digital-time-code-and-broadcast-format
>> http://tf.nist.gov/phase/Properties/main.htm
> ​See/Search Also:
> ​Precise Time and Time Interval Clocks Time Frames and Frequency, James R.
> Clynch  Navy Postgraduate School.
> ​Introduction to Frequency Standards  by Lindon Lewis
> ​Interested?   Get back to me to start planning for the 2018 launch, and
> cubesat in lunar orbit,  exact date not known.​
> Best, 73,   Pat Barthelow AA6EG
> apol <apolloeme at gmail.com>loeme at gmail.com


> *"The most exciting phrase to hear in Science, the one that heraldsnew
> discoveries,  is not "Eureka, I have found it!"    but:*
> "That's funny..."  ----Isaac Asimov
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