[time-nuts] time sync by moonbounce

Mon Jun 8 23:48:27 UTC 2020

My 2001 copy of Uplink-Downlink was printed by GPO and is 674 pages of
10-point type. I would not want to scan it! Anyway, it was only $25 from an
Abebooks seller including tax and shipping and is in near-new condition
including a plastic-wrapped dust jacket.

Jeremy

On Mon, Jun 8, 2020 at 1:01 PM jimlux <jimlux at earthlink.net> wrote:

> 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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