[time-nuts] time sync by moonbounce

Mon Jun 8 19:51:46 UTC 2020

On 6/5/20 3:43 PM, Wannes Sels wrote:
> I bought a used copy of Uplink-Downlink on Ebay.
> Unfortunately the quality is downright bad. Printed on what looks like
> bright white copy paper with a laser printer.
> All the images and illustrations are rasterized, the text is low
> resolution. The photo on the cover shows compression artifacts.

The pdf on the NASA site is of similar quality, and probably what the 
"print to order" version is printed from.

I don't know where one would go about getting a copy of the GPO printed 
version  - perhaps a used book dealer.
Conceivably, someone could get a good copy from a library that happens 
to have it and spend the time to scan it.

> 
> The last page reveals the culprit: "Printed in Great Britain by Amazon.co.uk
> "
> A quick search shows similar experiences with other print on demand books
> from Amazon.
> 
> Unfortunately there's no way to tell if a book was printed on demand, most
> listings just show the cover image instead of a photo of the actual book.
> 
> I will try to return it, if I don't have to cover shipping costs.
> 
> Buyer beware...
> 
> Wannes
> 
> On Mon, May 25, 2020 at 4:46 PM EB4APL <eb4apl at gmail.com> wrote:
> 
>> Hi Jim,
>>
>> This explains a lot of things. As an old time user of the Moon Bounce
>> time synchronization in the Madrid Space Complex, I can say that the
>> system was never popular among the users, it was cumbersome to use and
>> there were already other systems with better accuracy and availability,
>> such as VLBI and Loran-C.  We used Loran-C as our daily reference
>> because we had a station at a distance of 650 Km and the signal was very
>> good, even with an old receiver who needed manual estimation of the
>> delay the results were very good.  Maybe the aliens who designed the
>> system were not very aware of the humans idiosyncrasies
>>
>> I think that the idea was good, but the implementation was not so good.
>> I can summarize the "peculiarities" as I remember them:
>>
>> - The transmissions had to be scheduled for a period of common moon
>> view. The receiving station was manned 7/24 but the transmitting station
>> (DSS13, if I remember it correctly) had to be manned specially for the
>> event by a crew probably from Barstow, some 40 miles away.
>>
>> - Normally there were not provisions for voice communications between
>> the two end points, so if we did not got correlations we didn't know if
>> the transmitting station was working ok or even if it was not manned due
>> to some problem.
>>
>> - There were not monitoring aids in the receiver, so if we did not have
>> correlations, we has to climb to the roof, verify the pointing of the
>> antenna (there were a rifle scope for that), and if it was, tried to
>> contact DSS13 by phone and pray.
>>
>> - As you can figure it out, the antenna was not remotely controlled. One
>> had to climb to the roof, set the moon declination for that day using a
>> handwheel, slew the hour angle with a switch and select the hour angle
>> rate with another switch. The moon position and rate was obtained from a
>> nautical almanac and when the sky was clear we used the above mentioned
>> rifle scope.
>>
>> The receiver was quite dumb, all intelligence was on the transmitter
>> site. The TX equipment  generated a PN code that lasted about 1s, and a
>> full observation cycle lasted about a minute, I don't remember the exact
>> figures. The code was sent advanced to take care of the round trip light
>> time but an additional time bias of 30 us was also introduced which was
>> the basis of the measurement. The bias was decreased 1us/s, so
>> theoretically it was received just on time in the second 30.
>>
>> The receiver generated the same PN using the station timing reference
>> (from a HP 5065A Rb) and it was correlated with the received code. The
>> output of the correlator was integrated and sent to a strip chart
>> recorder. The graph consisted in one trace with a quite noisy ramp and
>> the other trace with 1PPS from the station reference.  Now the weird
>> thing: after finishing an observation, we put the graph in a desk and
>> using a drafting rule we draw a straight line that tried to be the "best
>> fit" to the noisy ramp. Were the line crossed the zero we read the PPS
>> mark there and counting back to the start of the minute we got the PPS
>> offset with respect to the transmitting station. Of course we averaged
>> the values obtained from several minutes, after discarding the noisiest
>> ones.
>>
>> Since we didn't had any faith in the system we didn't tried to suggest
>> improvements or improve it ourselves. A good one could be to use a
>> computer program to perform the best fit analytically, but this would
>> mean to type the hundreds of points manually from the graph and we never
>> tried this. There were not a digital version of the output, we also
>> could use a digital voltmeter for acquiring it. We suggested or
>> implemented a lot of improvements to other operational things, but this
>> contraption was felt as a dead horse from the beginning and its
>> operational life was short. Later it was replaced with a GPS based one:
>> 2 full height racks filled with equipment and an antenna made from a 10
>> or 20 gallon hermetic paint drum for housing the front end electronics,
>> topped with a fiberglass radome about 1 1/2 ' in diameter. It was
>> painted white, but the cylinder origin was discovered during a
>> maintenance. It was a beautiful prototype that worked very well during
>> its shot life.
>>
>> I don't keep pictures of this equipment, but I have one with the same
>> antenna used for other purposes.
>>
>> Sorry for the bandwidth, but the thread brought me old memories.
>>
>> Best regards,
>>
>> Ignacio
>>
>>
>> El 23/05/2020 a las 19:17, jimlux escribió:
>>> On 5/23/20 9:18 AM, Mike Millen wrote:
>>>> Probably a good idea... there are two page 19s and no page 20 in the
>>>> pdf.  :-(
>>>>
>>>
>>>
>>> That's the page where the aliens came and told us how to build the
>>> DSN, then the story resumes with 26m antenna design and operation.
>>>
>>> (If anyone's interested, I can probably ask the librarians to find it
>>> at JPL - correcting the pdf/microfilm is probably beyond scope)
>>>
>>>
>>
>> --
>> El software de antivirus Avast ha analizado este correo electrónico en
>> busca de virus.
>> https://www.avast.com/antivirus
>>
>>
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