Author Topic: Losing Telemetry Data  (Read 873 times)

Offline BDL

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Losing Telemetry Data
« on: September 08, 2018, 10:28:39 AM »
Hello everybody. I think I'm a bit confused about what telemetry data really is, its value to NASA, and why NASA lost some of the Apollo 11 telemetry data.
I'm not sure I understand the full story about how they lost the data in the first place, and why it happened. Can someone explain it to me?
“One small step for [a] man, one giant leap for mankind.” - Neil Armstrong, 1969

Offline MBDK

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Re: Losing Telemetry Data
« Reply #1 on: September 08, 2018, 03:01:23 PM »
It appears to be basically an unfortunate episode of NASA taping over data they thought was expendable (since it was, for the most part, already copied to other media) when they realized they had no more tapes to retrieve information from another project several years after the Apollo program.  Here is a decent link for more detailed information - https://www.npr.org/2009/07/16/106637066/houston-we-erased-the-apollo-11-tapes
"Laugh-a while you can, monkey-boy." - Lord John Whorfin

Offline Northern Lurker

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Re: Losing Telemetry Data
« Reply #2 on: September 08, 2018, 03:51:43 PM »
I have a vague recollection that those data tapes were made with whale product. When whaling was banned, there was shortage of tapes before manufacturers found new material to replace whale product. It is a pity that we lost the A11 tapes, but it would also been pity to lose unique data from new missions.

Lurky

Offline BDL

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Re: Losing Telemetry Data
« Reply #3 on: September 08, 2018, 06:40:25 PM »
It appears to be basically an unfortunate episode of NASA taping over data they thought was expendable (since it was, for the most part, already copied to other media) when they realized they had no more tapes to retrieve information from another project several years after the Apollo program.  Here is a decent link for more detailed information - https://www.npr.org/2009/07/16/106637066/houston-we-erased-the-apollo-11-tapes
Thank you. Most of the places that tried to explain didn’t do too good at explaining. And I don’t trust the HB’s version of the story.
“One small step for [a] man, one giant leap for mankind.” - Neil Armstrong, 1969

Offline BDL

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Re: Losing Telemetry Data
« Reply #4 on: September 08, 2018, 06:46:03 PM »
So, did NASA ever have any special plan for those tapes in the first place? Did they plan to have them archived somewhere special?
I mean, I would presume that NASA didn’t expect people would deny they ever went to the moon, so maybe it wasn’t that much of a priority.
« Last Edit: September 08, 2018, 07:22:01 PM by BDL »
“One small step for [a] man, one giant leap for mankind.” - Neil Armstrong, 1969

Offline Obviousman

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Re: Losing Telemetry Data
« Reply #5 on: September 08, 2018, 07:18:47 PM »
So, did NASA ever have any special plan for those tapes in the first place? Did they plan to have them archived somewhere special?

Well, they WERE archived... just not very well. When the new generation of tapes began to fail and they needed to re-use the older tape, the A11 tapes were swept up in the gathering. Perhaps whoever was in charge didn't appreciate what the tapes were (poor archiving) or perhaps someone made a decision that the data was recorded elsewhere / no longer relevant and therefore they could be recycled. For example, the imagery from the SSTV was already available on other media; it's just that if we did have the original SSTV tapes we could of had better quality.

I certain know that a number of Defence publications I managed were never archived despite there being regular requests for them (e.g. When did this policy change? Why did it change?).
« Last Edit: September 08, 2018, 07:21:31 PM by Obviousman »

Offline Peter B

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Re: Losing Telemetry Data
« Reply #6 on: September 09, 2018, 12:53:25 AM »
I certain know that a number of Defence publications I managed were never archived despite there being regular requests for them (e.g. When did this policy change? Why did it change?).

That's an issue in my line of work too (HR / Payroll / Employee Relations). When you look at someone's pay file and want to know why one of your predecessors did something to someone's pay record, it's useful to know what the relevant legislation or conditions of service document in effect at that time said.

For example, a couple of months ago I was looking at an employee's pay record when I found she'd been allowed to count her time working at a charity towards the time needed to qualify for a particular entitlement. The relevant law says you can only count government service towards the qualifying time, but it can be a murky question as to what exactly counts as government service. So the law has a regulation which lists the eligible organisations. The thing is, the list is often updated as organisations are created, disbanded, merged, or even have their legal nature changed.

So in this employee's case we needed to know whether the charity she worked for back in the 1990s was by some chance on the list as the regulation existed 20 years ago. And, as it happened, one of my colleagues had a copy of the late 1990s version of the regulation, and we were able to check it directly. And no, the charity wasn't on the list, so she shouldn't have been allowed to count her time working at the charity. Whoops.

We could probably have checked online, as something as significant as legislation is usually archived properly. But it can be a different thing with conditions of service documents, where it's often only because of a slightly obsessive employee that old versions of such documents are preserved; usually when employees transfer out of these teams they throw out all the old papers they don't need any more, without thinking that it might be useful to the team as a whole.

Offline Kiwi

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Re: Losing Telemetry Data
« Reply #7 on: September 09, 2018, 10:25:57 AM »
JayUtah wrote two long posts about this at the old BAUT forum, now CosmoQuest, back in 2011. I'm guessing he wouldn't mind them being posted here in full for the ApolloHoax.net record.

I'll include the current links to each post.

Note the usual layperson's misconception by GG300: "No one would re-use the Apollo 11 television tape recordings..." That is NOT what was re-used -- telemetry tapes were nothing like ordinary video tape.

Quote
BAUT Forum
JayUtah
18 Oct 2011 04:05 AM
Has any HB dared challenge Gene Kranz?
Reply 47
Posts 11,114
http://forum.cosmoquest.org/showthread.php?8184-Has-any-HB-dared-challenge-Gene-Kranz&p=1947042#post1947042

Originally Posted by GG300 
http://www.bautforum.com/showthread.php?p=1946947#post1946947
No one would re-use the Apollo 11 television tape recordings, for some other recordings, I simply refuse to believe that !

Your disbelief is irrelevant. When you have your own space program, you can run it any way you see fit. But as long as you're limited to commenting on someone else's work, your coulda-shoulda-woulda's don't really establish a standard for authenticity.

The hidden premise to your disblief is the mistaken notion that people at the time considered these tapes original copies, of great historic value. That is not true. That is a modern reinterpretation of the situation put forward by people who don't care to study the story. You don't get to judge the decisions of people who, for very good reasons, didn't share your expectations.

As others have said, these were not videotapes, these were telemetry tapes. They are very large, very expensive, and can only be played on telemetry recorders, which are also in turn very large, very expensive, very temperamental, and these days also very rare. The telemetry signal from a spacecraft in the 1960s and 1970s consisted of several channels of largely analog data modulated on a complex carrier signal. The Apollo 11 television signal -- which was not a standard video signal, but rather a special compressed format that was used only for a few space missions -- was part of this complex set of signals. Those signals are what the tape records.

In the form received by the ground stations and subsequently recorded on the tape, it was useless. It could not be played on a regular television or sent to the television networks. It had to first be converted to a standard signal. This was done using a custom-built equipment the size of two refrigerators. It extracted the television portion of the signal, converted it to standard formats, and then recorded that extracted and converted signal on standard (at the time) broadcast videotape.

That converted signal was considered the original recording, and that survives. The telemetry tape, containing the special compressed format, was treated as the backup. In case anything went wrong with the real-time conversion hardware, the telemetry tapes could be played back after the mission and the repaired big clunky converter could be used then to produce the standard-format signals after the fact. But that wasn't necessary. The converter worked fine, the broadcast went out live, and the standard-format NTSC first-generation recordings were carefully preserved.

The NTSC-format video is the only one that's usable. After Apollo 11, the slow-scan converter was decommissioned and replaced by the system that took advantage of the bigger bandwidth available on subsequent missions that used high-gain antennas and their own S-band channel for television. But that's incompatible with the old telemetry format. The NTSC conversion made live during the missions was the most faithful that could be made, and from the engineers' perspective, the most faithful that could ever be made. Any subsequent attempts to extract the video from the telemetry would produce a video signal no better than the one they had in hand.

Now, decades hence of course, we have better methods of handling those analog signals and extracting more information from them. And an organization has painstakingly restored and preserved in working order one of the old telemetry recorders. But that was unanticipated in 1969. They had what they needed, so the telemetry tapes were placed dutifully in storage. It's not as if they just threw them in the Dumpster when the spacecraft landed.

I mentioned these tapes were large and very expensive. They're also environmentally unfriendly because the binder (the glue that holds the magnetic material to the plastic substrate) was made from a whaling product. The manufacturers of those tapes were eventually forced to find a greener process. They did, but it didn't work as well.

Keep in mind that these telemetry recorders are large, clunky, and expensive machines. You don't just pick one up in the showroom. They're made largely by hand, on an ARO basis. You don't just have warehouses of them sitting around. So after Apollo was over, the machines were immediately retasked to other space missions. They work for unmanned missions too. In fact, for unmanned missions the telemetry recorder is considered a Criticality 1 item. Without that recorder, you have no mission.

So when the new environmentally-friendly tapes were tested and found to be unsatisfactory, NASA found itself in quite a pickle. They had no way to record the data from missions that were already in progress and running out of good tape. The tape manufacturer couldn't fix the process in time. There were no other manufacturers for it -- remember, it's not just Panasonic VHS tape we're talking about. So the only course of action left was to reuse the good tapes from previous missions. Since the choice was between archived data of dubious value (since more useful copies existed), and new data from new missions, it's pretty much a no-brainer.

Real history works this way. We have practically no film from D-Day, because all the film from the battlefield was loaded onto one boat to be taken back out to the fleet. That boat was sunk and took all the film with it to the bottom of the English Channel. Just because something seems important, or is considered decades later to be important, does not mean it will invariably be preserved intact.
« Last Edit: September 09, 2018, 11:20:07 AM by Kiwi »
Don't criticize what you can't understand. — Bob Dylan, “The Times They Are A-Changin'” (1963)
Some people think they are thinking when they are really rearranging their prejudices and superstitions. — Edward R. Murrow (1908–65)

Offline Kiwi

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Re: Losing Telemetry Data
« Reply #8 on: September 09, 2018, 10:28:28 AM »
Next post by Jay:

Quote
BAUT Forum
JayUtah
19 Oct 2011 09:59 AM
Has any HB dared challenge Gene Kranz?
Reply 57
Posts 11,118
http://forum.cosmoquest.org/showthread.php?8184-Has-any-HB-dared-challenge-Gene-Kranz&p=1947594#post1947594

Originally Posted by cjameshuff
http://www.bautforum.com/showthread.php?p=1947452#post1947452
They weren't archival tapes in the first place...they were never supposed to be more than a temporary storage medium...

I can't emphasize this enough. They are not archival tapes.

The video portion of the Apollo 11 telemetry stream was recorded appropriately on professional videotape. It was also delivered live to worldwide television news services. That's the archival copy, at least of the video portion.

I answered this in a private message, but it bears answering here in public. The other portions of the signal were telemetered values such as Neil Armstrong's heart rate, the voltage on Main Bus A, the temperature of the RCS thrusters, the switch positions of the ECS console, and so forth. These were extracted and recorded on separate magnetic tape, typically the 9-track 6250 BPI computer tape that was relatively cheap and common at the time, or more typically on paper strip charts. Paper tape is easy to read (requiring only the Mark 1 eyeball) and easy to copy (just ask Xerox) and reasonably suitable for most post-mission analysis.

The telemetry recorders were not the primary means of access to the telemetry during and after the missions. Mission analysts didn't say, "Hm, I wonder whether there were any guidance anomalies during Apollo 11's 1202 program alarms. Let's just pop that tape in the machine and play back the telemetry." Why? Because, as I said, the machines are large, expensive, and therefore in high demand for recording telemetry. Strip charts, videotape, and 9-track computer tape record the telemetry channels in real time as they are broken out. The recording exists briefly as a backup, or in some cases as the primary data source if the demultiplexing cannot provide enough real-time channels.

Let me paint you a picture. Imagine a commercial kitchen refrigerator, one of those that's about a meter and a half wide and a bit over two meters tall. The left side is a patch panel. The right side is a tape drive and a control panel for adjusting each individual recording head. In the tape drive are the supply and takeup reels. Each is about 18 inches in diameter and a about an inch thick, made by Memorex. Tape speed is well over 100 inches per second, about ten times faster than a consumer reel-to-reel tape deck. You move these things around with forklifts.

You don't just pop the tapes in and out either. The recorders are highly configurable, so you have to know the head position and bias settings for each of the several physical tape channels. Yes, I said they were clunky. Very powerful, flexible, and completely suited to the task of recording Apollo instrumentation. But not the sort of thing you deal with for routine analysis. The Unified S-band telemetry signal was a custom design. Therefore only a highly configurable recorder could record it, and only a highly configurable decoder and demultiplexer could break out the individual instrument signals. The TV image was just another "instrument" in the overall format. The goal is to get these data into universal formats as soon as possible so they can be disseminated amongst the various researchers.
Don't criticize what you can't understand. — Bob Dylan, “The Times They Are A-Changin'” (1963)
Some people think they are thinking when they are really rearranging their prejudices and superstitions. — Edward R. Murrow (1908–65)

Offline BDL

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Re: Losing Telemetry Data
« Reply #9 on: September 09, 2018, 03:53:04 PM »
Thank you Kiwi. That certainly explains a lot.
Jay really does know a bunch, eh?
“One small step for [a] man, one giant leap for mankind.” - Neil Armstrong, 1969

Offline nomuse

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Re: Losing Telemetry Data
« Reply #10 on: September 11, 2018, 10:58:49 PM »
Kinda like the Beeb. As I remember, they had a bunch of their stuff archived off-site. Trouble was, they thought significant chunks of early Doctor Who (among other things) were being stored at the off-site archive, and the off-site archive thought the BBC had them stored at the studios.

It's actually a fascinating historical and technical journey how some of these episodes have been found, rescued, and re-constructed.

It also echoes Apollo in that at the time, NASA had bigger and better plans. They thought they were on the cusp of a huge expansion into space and the old data with older instruments was going to be quickly overshadowed. There was certainly awareness of the historical significance, but of the stuff that the public would actually want (medical telemetry not really a part of it. Surface video of the first EVAs certainly). They had a first generation (depending on how you look at it) format conversion of the First Step and as far as anyone knew that was going to be good enough.

Thing is, no-one had any idea then how voracious the drive towards more and more pixels, higher and higher resolution was going to be. Or how clever the algorithms would get -- once the hardware was fast enough -- in cleaning up old data. Nobody knew then. Record companies weren't saving original session tapes except by accident. Moore had only published in 1965 and his predicted doubling effect had yet to be demonstrated or to show just how huge its impact would be. The idea of hauling out first-generation material (or the earliest generation available) to remaster for modern audiences wasn't really out there until the almost the turn of the 21st century.

Offline nomuse

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Re: Losing Telemetry Data
« Reply #11 on: September 11, 2018, 11:04:51 PM »
Off the subject a bit, but those massive Memex machines always make me think of another artifact of early recording; the steel tape machine. Those things are terrifying!

Offline JayUtah

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Re: Losing Telemetry Data
« Reply #12 on: September 14, 2018, 10:15:13 AM »
Thanks for reproducing those posts.  I was afraid I was going to have to type all that in again.  ;D
"Facts are stubborn things." --John Adams

Offline Abaddon

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Re: Losing Telemetry Data
« Reply #13 on: September 14, 2018, 11:12:51 AM »
Thanks for reproducing those posts.  I was afraid I was going to have to type all that in again.  ;D

Alas, there is always some young turk who happens upon the Apollo CT idiocy and considers themselves some form of genius for "figuring it all out".