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Simon
2002-Mar-01, 11:52 AM
Okay, I'd just like some clarification on something... One of the arguments I've seen that the Apollo landings were fake was a radio signal would take about 2.5 seconds to make a round trip from the earth to the moon. Therefore, each order from mission control should have a 2.5 second delay before the astronauts answer. I've listened to a couple snippets of radio logs, and it does seem that the astronauts reply immedietly after Mission Control talks.

This was bugging be because I didn't know how to shoot it down... /phpBB/images/smiles/icon_wink.gif

David Hall
2002-Mar-01, 12:11 PM
Well, for one thing, are they really replying to what's being said? Or are they in fact continuing their own side of the conversation irregardless of what Mission Control was saying? I'm also sure very often the astronauts could anticipate what was going to be asked next and started giving the answer before the question was even asked.

I'd need to see an actual example of a clear-cut question-answer exchange that couldn't be explained as above before questioning this too seriously.

SeanF
2002-Mar-01, 12:13 PM
My simple guess would be that the logs have had the dead space edited out so people don't get bored listening to it . . .

/phpBB/images/smiles/icon_smile.gif

JayUtah
2002-Mar-01, 03:53 PM
David is right; the communications were, for the most part, not responsive conversations. The astronauts knew what they had to report and when. Just because an astronaut statement follows directly after a mission control statement doesn't mean it was given in response to it.

You must also recall that the recorder was on earth and that it's not always possible to distinguish between the capcom and the astronaut. If an astronaut makes a statement and the capcom responds, it will properly sound as if the capcom's answer directly follows because no communication delay applies to the recordings of the capcom.

Michael Collins describes his amusements with comm delay. After the Eagle landed and the capcom said, "Be advised there are lots of smiling faces around the room," Collins remarked, "And one in the command module." But because the comm interval was longer for Collins (three trips instead of two), his comment is recorded on the tape after Houston's next comment: "That was a beautiful job, you guys." And so the tape makes a shambles of the flow of the conversation and Collins is spending the rest of his life explaining that he was pleased at a successful landing, not fishing for a compliment.

The best way to convince yourself that comm delays really did happen is to listen to the first hour or so of the Apollo 11 EVA. Very often when Neil or Buzz keys his mike you can hear the tail end of mission control's last statement echoing from the astronaut's earphones to his microphone, exactly 2.6 seconds after it was directly recorded on the tape. It went onto the tape, but also to the moon and back and onto the tape again.

When people say there's no evidence of comm delay, it's because they haven't looked for any evidence of comm delay. This, actually, is an example of what irks me most about hoax believers. They say, "We should observe X, but there's no X." Usually it takes me only a few minutes to find all kinds of examples of X. But of course the hoax believer's audience isn't necessarily equipped or motivated to look for X themselves; they just assume the hoax author has made an exhaustive search and failed to find X. But really the hoax believer simply hasn't put any real effort or intelligence into his charges; he's just ignorantly and lazily asserting there's no X because he knows it will take effort to prove him wrong -- effort few people will make.

<font size=-1>[ This Message was edited by: JayUtah on 2002-03-01 10:54 ]</font>

johnwitts
2002-Mar-01, 09:59 PM
Listening to the Apollo 11 landing Flight controllers loop and the capcom/Eagle loop shows up the really bad 'tripping over each others words' that went on during the landing. These portions are edited out of the 'official' documentaries of the landings, probably because it sounds such a mess. There are examples where capcom Charlie Duke starts a sentence, then about a second later Neil or Buzz starts talking over him, then stop mid sentence to listen to what Charlie was saying. In the meantime, Charlie stops talking to listen to the communications coming from Eagle, not wanting to interupt. It all sounds comical, and so unslick, it makes you wonder how they didn't get into such a mess. You've also got the data delay, even longer than the voice, as it had to be processed, and sometimes got relayed to mission control via a different route. Here, the astronauts would call out an event, and the controllers would take a few seconds to confirm. If you go to the Apollo Archive site, you can download the .rm file for yourself to see what I mean.

Jigsaw
2002-Mar-02, 01:36 AM
On 2002-03-01 16:59, johnwitts wrote:
If you go to the Apollo Archive site, you can download the .rm file for yourself to see what I mean.
Okay, I'm here at the website, http://www.apolloarchive.com/ under "Multimedia" (that's what you're talking about, right?) but I have NO clue which one it is, other than it's an "Apollo 11 audio". Hint? /phpBB/images/smiles/icon_biggrin.gif

SpacedOut
2002-Mar-02, 10:06 AM
Try these two files from the site (about 2/3 down the Apollo 11 multimedia section):

EVA long-play part 1 (includes MOCR ground loop audio)
EVA long-play part 2 (includes MOCR ground loop audio)

Iím not sure that these the specific ones that johnwitts is referring to but I think they demonstrate his point.


<font size=-1>[ This Message was edited by: SpacedOut on 2002-03-02 05:07 ]</font>

johnwitts
2002-Mar-02, 05:01 PM
Here's the flight controllers loop and capcom/eagle loop, left and right channels.

http://www.hq.nasa.gov/office/pao/History/alsj/ktclips/ap11_landing_with_FD_loop.rm

It takes a while...

Oh yes, right click and 'Save Target as...' etc

<font size=-1>[ This Message was edited by: johnwitts on 2002-03-02 12:02 ]</font>

Donnie B.
2002-Mar-02, 06:32 PM
What a fascinating recording!

I remember the capcom/Eagle side very well from the actual event and subsequent replays on the many documentaries on the Apollo 11 landing. I have also seen transcripts of parts of the controller loop, but this is the first time I've heard the whole thing, synced to the radio communications.

Excellent!

Does anyone know whether there are recordings available of the subsequent events? I know there was a bit of a crisis a minute or two after the landing (pressure buildup in a fuel line of the descent stage, which might have required them to take off again). I'd love to hear the controller loop of that!

johnwitts
2002-Mar-02, 10:19 PM
It is rather good isn't it! The story I heard about this recording is that it was a backup copy that had recently been found. It was in quite a state, with the oxide layer almost a powder that was repidly disintigrating. There are bits missing altogether. For instance, Capcom 'copies' an alarm, yet Eagle doesn't call it. With a lot of messing about, they managed to save most of it. As far as I know, it's the only recording with both the flight loop and the capcom/LM loop. This is a pity, as it would be interesting to hear the Apollo 13 flight loop when the tank burst.

Donnie B.
2002-Mar-02, 10:56 PM
Hmmm, that's odd... I just listened to that file from the same site, and I could have sworn I heard at least some of the controller loop stuff in it (it's a compilation, not a single channel).

Was I wrong? Maybe I'll head back for another listen...

Perhaps this is the only surviving tape that is *only* the controller loop, not some mixture of channels?

johnwitts
2002-Mar-02, 11:13 PM
I havn't done an exhaustive search, by any stretch of the imagination. I've only got a slow connection so it takes literally hours to download each file. Maybe I should rephrase a bit and say it's the only recording with both FD loop and capcom/LM loop at the same time, that I have found so far. I can't remember hearing another recording where we can hear all that the Flight Controllers have to say. If only this A11 recording carried on a bit, then I'm sure we'd hear the fuel pipe crisis unfolding.

<font size=-1>[ This Message was edited by: johnwitts on 2002-03-02 18:15 ]</font>

Jigsaw
2002-Mar-03, 01:33 AM
Okay, thanks. /phpBB/images/smiles/icon_smile.gif

GrapesOfWrath
2002-Mar-04, 09:12 AM
On 2002-03-02 13:32, Donnie B. wrote:
Excellent!

Seems like an appropriate comment upon your graduation post. <a name=" fireworks ">Congratulations (http://antwrp.gsfc.nasa.gov/apod/ap020302.html)!

2002-Mar-04, 11:56 AM
<a name="20020304.5:44"> page 20020304.5:44 aka Edited for Pr time
On 2002-03-04 04:12, GrapesOfWrath wrote: To: 11 MEN 13 KAYAB

2day i began {maybe} a thread about Pioneer 10
about power a signal to noise ratios

Congratulations (http://antwrp.gsfc.nasa.gov/apod/ap020302.html)!
two lines of it include
PST a 200 Kw uplink
was sent to Pioneer-10 and 22 hours later {Madrid}

Donnie B.
2002-Mar-04, 07:37 PM
On 2002-03-04 04:12, GrapesOfWrath wrote:


On 2002-03-02 13:32, Donnie B. wrote:
Excellent!

Seems like an appropriate comment upon your graduation post.
Congratulations!


Thanks, GoW ! Noticed it myself yesterday... nice to be done w/that damn thesis defense...
/phpBB/images/smiles/icon_smile.gif

SAMU
2002-Mar-05, 05:12 AM
I agree that the lack of time delay in many ground to Apollo transmissions can be explained by indirectly responsive transmissions and by anticipation responses. But we can all now directly observe speed of light communication delays on a daily basis in the communications between the cable news personel and their counterparts in Afghanistan. The round trip travel time for those messages traveling apx 200,000 miles is one second (25,000 up to geosync, 25,000 to the first relay satelite, 25,000 to the second above Afghanistan and 25,000 down then the reply coming back the same route.)

In the normal conversations of the news men the delay is very noticable and even somewhat annoying. In the transmissions of Apollo the structure of the transmissions vis a vis the speed of light delay, which although twice as much as for the transmissions from Afghanistan is very much less noticable.

SAMU

JayUtah
2002-Mar-05, 01:44 PM
Delivery delays can actually be much longer in television. Until recently I was employed working with the technology that provides exactly that mode of satellite communication. It's a fairly good analogue to the Manned Space Flight Network.

You certainly have light travel time to and from the satellite, and perhaps in Afghanistan's case two satellites. You also have some delays in the transponders on the satellite. But there is also substantial delay in the ground equipment at both the uplink and downlink sites. In the case of digital streams they may need to be spooled for a fraction of a second until they are injected into a satellite transport stream.

Let me explain that last sentence. In the case of digital television, each transponder handles a transport stream (a digital signal on a carrier) composed of up to about eight complete television programs (where program is loosely defined) and supporting information at bit rates close to 35 million bps. The format of this signal is rigidly defined. For packets containing video or audio, you simply cannot send them up to the satellite as soon as they are available from the encoder. They must wait until the appropriate "slot" in the transport stream is available.

Further, MPEG-2 compression and decompression (the basic standard for practially all such transmissions) requires substantial prebuffering in the decoder. It's not uncommon for broadcast-quality MPEG decoders to spool a few seconds' worth of data prior to starting the decode.

From Afghanistan the signal may have to make two satellite hops to get to Atlanta or New York. This is because there isn't any satellite that springs to mind which has both locations in line-of-sight. So an intermediate link in Europe is likely. Stream injection protocols apply at all sites. Then it must be sent back up to the distribution satellite so that your local cable company can pick it up. In the case of DirecTV and Dish Network, another satellite trip is required to get to their distribution satellite. Now the last two steps don't affect a conversation between the anchorman and his correspondent in Afghanistan.

The current MSFN/TDRS network has many of the same real-time limitations as the consumer satellite network. The Apollo MSFN used less packet-multiplexing and less digitized communication. Only the telemetry data was transmitted over the MSFN in digital format because it was already digital. Other signals such as voice were carried in analog format.

The astronaut speaking into his microphone transmitted from the VHF antenna to the EVA antenna on the LM. The LM communication equipment upconverted this to S-band an frequency and transmitted it either over its built-in steerable S-band antenna or over the erectable S-band antenna. This relay was provided by the LRV on J-missions.

The signal was received by one of several receiving stations in the MSFN and transmitted to mission control over a redundant and rather hodge-podge collection of leased telephone lines and satellites. A collation station at MCC selected the appropriate signal and fed it to MCC computers and communication switchboards. It was broadcast back out on a different S-band frequency for the benefit of the orbiting command module, which generally cannot pick up the VHF signals from the suits and cannot intercept the S-band transmission to earth.

I recommend Kranz's Failure Is Not an Option and Lindsay's Tracking Apollo to the Moon for detailed explanations.

K. Hovis
2002-Mar-06, 01:03 PM
On 2002-03-05 08:44, JayUtah wrote:


From Afghanistan the signal may have to make two satellite hops to get to Atlanta or New York. This is because there isn't any satellite that springs to mind which has both locations in line-of-sight. So an intermediate link in Europe is likely. Stream injection protocols apply at all sites. Then it must be sent back up to the distribution satellite so that your local cable company can pick it up. In the case of DirecTV and Dish Network, another satellite trip is required to get to their distribution satellite. Now the last two steps don't affect a conversation between the anchorman and his correspondent in Afghanistan.



I have DirecTV and experience the satellite delay effect fairly often. I can have a tv show on a tv connected to the over-the-air antenna and have the same show in the satellite reciever. There's a 2 to 3 (sometimes 5) second delay in the satellite signal compared to O-T-A. I had to explain to my wife awhile back why this happens. She was at her cousin's house outside St. Louis watching the Rams play on the broadcast station. I was watching the satellite. While talking on the phone a really good play happened. I could hear the sound, but of course it hadn't shown on my tv yet. It took a good ten minutes to explain why I didn't see the play at the same time my wife did!

<font size=-1>[ This Message was edited by: K. Hovis on 2002-03-06 08:05 ]</font>