OT: Moon Landing

One of the triggers for Britain to activate all its submarine launched nuclear missiles was the absence of the BBC's Today radio programme on Radio 4 long wave for 3 days. The radio engineers who worked at the broadcast end always wondered why they were given so many back up generators and whatnot to ensure even if the national grid went down, there were 2 spare 1MW generators on site kept fully serviced and tested monthly so even if the grid went down and genny 1 failed, genny 2 could step in. Presumably if genny 2 failed as well, they'd have 3 days to arrange for the hire of *another* spare one and if they couldn't do that in 3 days then it was clear the country was toast anyway.

Russia has a similar system that will activate its doomsday autonomous underwater drones that will make their way to their targets in the absence of a regular confirmatory signal that all is well. I think they had to bring these drones into service after Dubya announced they'd abandoned the 'no first use' doctrine for the US's nuclear weapons.

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Sounds dubious. How would a submarine receive TV broadcasts? If they stuck their heads up enough to receive a TV signal they would be detected each day and the entire purpose of using submarines would be lost.

If they used the same type of very low frequency broadcasts everyone else uses to command their subs someone on the ground would have to relay the message and those people would have knowledge of the situation and so no need to watch for a TV show.

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  Rick C. 

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Same with the Airbus planes:

There are many heavy transport programmes aired at Discovery, etc. "How do we transport wingd from the UK to France?" They give no answer to why would anyone in their right mind do that in the first place. But this arrangement apparently makes the socialists happy.

Best regards, Piotr

Radio 4 long wave is on 200kHz it has quite good penetration into sea water with a wavelength of 1500m. I think MSF rugby on 60kHz and the Omega network on even lower frequencies around the 16kHz band could also be used to communicate slowly with deeply submerged submarines. It all became a lot easier after SQUIDs became available.

It was a radio show on 1500m.

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Martin Brown

The long-standing Today programme on long wave. It's a *radio* programme that at that time if not now was on 1500 meters AM.

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They only have to have an antenna on the surface for a short time, once a day. It wasn't TV broadcasts (short range) but globalshortwave (aka long wave) radio that was the signal.

Nothing socialist about it. The theory was that anybody who was going to compete with Boeing had to be big, and the way to get a big European competitor was to amalgamate the biggest surviving French, British and German aerospace companies.

The British-French Concorde project had shown it could work.

The Soviet Union might have started off with the idea that it would have only one aerospace business, but capitalist Europe had got to the same situation driven by economies of scale.

--
Bill Sloman, Sydney

stuck their heads up enough to receive a TV signal they would be detected e ach day and the entire purpose of using submarines would be lost.

day.

radio that was the signal.

Nuclear missile subs don't surface... at all. Not until they return to hom e port. Shortwave is even worse than TV. They would need a long antenna. Funny the term "short" wave was coined a long time ago when 30 MHz was pre tty high frequency. There is literally no way they would surface long enou gh to erect a long wire antenna and receive the signal. Any exposure at al l puts them at risk of being tracked and taken out before a war was started .

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  Rick C. 

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ELF (3 to 30 Hz) signals propagate somewhat through deep salt water. Send a "come closer to surface" command at a very slow data rate, say

1 bit/minute. This command might be a dozen or two (with authentication) bits long.

The submarine comes closer to surface, puts out a long wire (kilometers) with a float at the far end. This is then used to receive the actual command at ULF/VLF (300 Hz to 30 kHz) at a much higher data rate. The float should ideally remain 10 m below the surface to avoid detection by ordinary microwave airborne radar.

Incorrect. I wrote down many of the facts, direct from the Honeysuckle engineers involved at the time, with whom I shared lunch just yesterday. I have email addresses and phone numbers, and a promise from at least one of them to scan and send the original documentation after their return home. Bernard Smith was most helpful (he has amazing recall of the details!), and Keith Brockelsby helped.

There was one S-band uplink (IIRC 2282.5MHz) modulated with:

• a 30KHz FM audio subcarrier

• a 70KHz biphase modulated command (data) channel,

• direct carrier phase modulation from the ranging PRNG

• Doppler from the relative velocity

The spacecraft receiver demodulated the ranging signal and directly applied it to the transmit carrier. I have not been able to find out whether that signal was squared-up (adding phase noise) before re-transmitting. Ranging data was used to calibrate and separate the Doppler vs oscillator drift.

There were two S-band downlink signals, one for TV, the other with a

1.024KHz telemetry signal and a 1.125MHz audio carrier. The telemetry downlink was frequency-synthesised from the uplink frequency, using analog phase locking. A ratio of 240/221 was mentioned and I think this was the ratio, TBC.

The ranging PRNG had a bit rate of 992Kbps, sequence length about 5.5M, for a 5.5 second repeat interval. It was composed of either a short code or a long code, each produced from shift-register feedback generators of various lengths. The short codes were 11,15,31,63 bits, and the long codes were 11,31,63,127 bits. Ranging consisted of sending these in turn and correlating each one (receiver had a delayed copy of the PRNGs). The best correlation yielded a "Chinese number" (c.f. Chinese remainder theorem) that was added in to start correlation using the next longer sequence.

This was capable of range accuracy around 20cm at lunar distance, a spectacular achievement at the time.

The ranging data was used for trajectory estimation (by variation from the calculated path), because the earth baseline wasn't long enough for accurate triangulation.

More details as I get them.

Clifford Heath.

The final crash site of the discarded Apollo 11 LEM is still unknown, despite years of high-resolution mapping. Strange, because the footprints are clearly visible.

Not a rigid rod. It was a curved tape, exactly like that used in a tape measure. The flag was touched several times, and it waved until the fabric's own friction slowed it - the decay rate clearly shows the lack of aerodynamic drag

Clifford Heath.

Incorrect. I wrote down many of the facts, direct from the Honeysuckle engineers involved at the time, with whom I shared lunch just yesterday. I have email addresses and phone numbers, and a promise from at least one of them to scan and send the original documentation after their return home. Bernard Smith was most helpful (he has amazing recall of the details!), and Keith Brockelsby helped.

There was one S-band uplink (IIRC 2282.5MHz) modulated with:

• a 30KHz FM audio subcarrier

• a 70KHz biphase modulated command (data) channel,

• direct carrier phase modulation from the ranging PRNG

• Doppler from the relative velocity

The spacecraft receiver demodulated the ranging signal and directly applied it to the transmit carrier. I have not been able to find out whether that signal was squared-up (adding phase noise) before re-transmitting. Ranging data was used to calibrate and separate the Doppler vs oscillator drift.

There were two S-band downlink signals, one for TV, the other with a

1.024KHz telemetry signal and a 1.125MHz audio carrier. The telemetry downlink was frequency-synthesised from the uplink frequency, using analog phase locking. A ratio of 240/221 was mentioned and I think this was the ratio, TBC.

The ranging PRNG had a bit rate of 992Kbps, sequence length about 5.5M, for a 5.5 second repeat interval. It was composed of either a short code or a long code, each produced from shift-register feedback generators of various lengths. The short codes were 11,15,31,63 bits, and the long codes were 11,31,63,127 bits. Ranging consisted of sending these in turn and correlating each one (receiver had a delayed copy of the PRNGs). The best correlation yielded a "Chinese number" (c.f. Chinese remainder theorem) that was added in to start correlation using the next longer sequence.

This was capable of range accuracy around 20cm at lunar distance, a spectacular achievement at the time.

The ranging data was used for trajectory estimation (by variation from the calculated path), because the earth baseline wasn't long enough for accurate triangulation.

More details as I get them.

Clifford Heath.

Do you think the moon landing would have been possible/feasible if the tran sistor had not yet been invented? Sometimes I wonder how limited we are wi th the current technology.

I recall meeting some guys who worked at NASA facility in Florida. They cl aimed that even today (well, 10 years ago) there was no off the shelf techn ology that would substitute for the TTL logic based design they used to tie all the control center equipment together with the same level of fault pro tection and speed/latency. It was pretty interesting.

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  Rick C. 

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Clifford Heath wrote in news:sy7ZE.40412$472.6431 @fx12.iad:

Huh? Crash site?

No. They LANDED the ENTIRE LEM. They launched leaving behind the LEM base. All of the Apolla landing sites are known. Nothing is missing. Nothing was 'discarded'. All of our gear still up on the Moon is still all our gear. We discarded nor relenquished ownership of none of it.

A VK5 (South Australia) amateur yesterday made a real-time 50yr replay of the landing audio via 5.6GHz EME link to Goonhilly. They used a 28m dish at one end and 33m at the other, and when setting it up on Saturday, found that they each were illuminating such a small part of the Moon's surface with their narrow beams that adjustment got them +4dB on the link.

!!!

Clifford Heath.

After re-entering the command module, the ascent part crashed on the Moon. No-one knows where.

That site is maintained by Colin McKellar, who assisted greatly with organising yesterday's reunion. There's a bunch of other stuff that's been shared privately with the attendees too.

Clifford Heath.

Clifford Heath wrote in news:gp8ZE.70070$jl6.12463 @fx04.iad:

Ahhh...

That would follow that they all did that.

If they cannot locate one, it is likely buried in the side wall of a crater