[time-nuts] moon bounce for synchronization
eb4apl at gmail.com
Sat Jan 30 23:01:29 UTC 2016
I was a lot of times at the other side of the link, the receiving end,
those days (and I also have no hair).
The procedure was cumbersome: you have to climb to the roof to manually
point a small parabolic antenna to the moon using handwheels and a rifle
scope. The antenna had an hourangle electrical drive which moved it at
sidereal rate through a differential gear and a variable speed motor so
you can select an offset to the rate that matched the moon motion at the
Back to the Control Room you contact the transmitting station (I think
it was DSS12) by voice to insure that they have the station manned and
transmitting, and began to operate the "thing". The transmission were
specific for each receiving station, because all the complex processing
was done at the transmission end: the transmitting equipment accounted
for the instantaneous round trip distance between the transmitter and
the receiver via the moon and continuously adjusted the modulating code
"early" in order to to be received on time. The equipment also
introduced a one microsecond shift each second. The receiver had a
correlator whose output went to an HP strip chart recorder which draw
the correlator output in one channel and a PPS with a minute mark in the
If everything went OK we recorded several ramps from the correlator
output, and here comes where the fun started: we had to adjust the noisy
ramp to a straight line and extrapolate it to the zero crossing.
Counting the seconds from the minute mark + 30 up to the zero crossing
we got the local clock offset.
Fortunately we relied on Loran C as our main clock offset determination
method until the arrival of GPS.
Good old times.
Ignacio, EB4APL and former DSN engineer.
El 30/01/2016 a las 20:19, jimlux wrote:
> On 1/30/16 10:43 AM, Jeremy Nichols wrote:
>> Ooh! Ooh! Not only a 5245 with a 5265 voltmeter plug-in but a 5360
>> Computing Pig! Great picture, thanks for posting it.
> I like how none of the push buttons in the panel below the counters
> have labels, either on the faceplate or on the button themselves.
> I'll see if I can track down more info. That handsome devil of an
> engineer in the picture probably still works at the lab (albeit with
> gray or no hair). Heck, the rack with the instruments is probably
> still out at Goldstone and being used. It's old enough that it
> doesn't have the new inventory barcodes on it, though.
> I just checked, and there are no pieces of property with the 5360 in
> the model number. So that piece of gear may have been excessed.
> There are, however, 3 of the 5245 counters around, and judging from
> the location codes, I think they're still out at the DSN sites or
> similar. No 5265s in the database, but they may not have been
> separately inventoried.
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