[time-nuts] Time and frequency practical exercise 2018 late quarter; precision measure of 432mhz band Sat in Lunar Orbit
kb8tq at n1k.org
Fri Nov 17 20:48:17 EST 2017
As you get into a bigger array, your antenna pointing / tracking requirements
become more exotic. I doubt that your 8 X array antenna has to do much more
than track the moon, I could be wrong ….
> On Nov 17, 2017, at 8:14 PM, Azelio Boriani <azelio.boriani at gmail.com> wrote:
> 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:
> On Sat, Nov 18, 2017 at 12:54 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
>>> 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:
>>> 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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