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

Sat Nov 18 01:14:54 UTC 2017

With 197dB of path attenuation and, say, 1W or 2W of transmitter
power, I think that a modest antenna is insufficient. The usual yagi
array for this distance is made by 8 27-element antennas like this:
<http://ok1teh.nagano.cz/dl5fn.jpg>

On Sat, Nov 18, 2017 at 12:54 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
> Hi
>
>
>> 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
>> DO NOT GO PUBLIC YET
>
> 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
>>
>
> Bob
>
>>
>> *"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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