Sat
Jul 20 2019
07:44 am

Fifty years ago right now, Astronauts Buzz Aldrin and Neil Armstrong were entering the lunar landing module to check out the systems and prepare for descent to the lunar surface. At about 4:17 PM Eastern time they landed on the surface of the Moon. Here's audio of the radio transmissions during final decent and landing.

They overshot their approach by about four miles, ending up at a rough patch of lunar surface unsuitable for landing. Furthermore, the guidance computer was crashing and generating numerous alarms. Neil Armstrong took manual control and flew the thing, searching visually for a clear place to land. His heart rate reached 150 BPM. They had not trained for this in simulations. Neil Armstrong landed Eagle with about 20 seconds of fuel to spare.

Although everyone sounds calm on the radio, the missed approach, course corrections, radio/telemetry dropouts and computer alarms created much panic back at Mission Control. It was Flight Director Gene Kranz's job to sort through all the chaos, evaluate the staggering flow of information and analysis, make GO or ABORT decisions in real time, and decide how much or how little information to relay to the Astronauts via CAPCOM.

Following is a transcript of radio communications during the lunar landing (CDR is Commander Neil Armstrong, LMP is Lunar Module Pilot Buzz Aldrin, CMP is Command module pilot Michael Collins, CC is Misson Control Capsule Communicator Charles Duke)...

04 06 17 27 LMP (EAGLE)
Houston, Eagle. How do you read?

04 06 17 29 CC
Five by, Eagle. We're standing by for your burn report. Over.

04 06 17 36 LMP (EAGLE)
Roger. The burn was on time. The residuals before nulling: minus 0.1, minus 0.4, minus 0.1, X and Z nulled to zero ... nulling ...

04 06 18 25 CC
Columbia, Houston. We've lost all data with Eagle. Please have him reacquire on the high gain, Over.

04 06 18 37 CMP (COLUMBIA)
Eagle, this is Columbia. Houston would like you to reacquire on the high gain. They've lost your data. Over.

04 06 18 50 CMP (COLUMBIA)
Eagle, did you copy Columbia?

04 06 18 54 CC
Eagle, Houston. Did you call?

04 06 19 05 LMP (EAGLE)
Eagle, Houston - Houston, Eagle. How do you read now?

04 06 19 08 CC
Roger. Five by, Neil. We copied up to the AGS residuals. Would you please repeat the AGS residuals in the trim - correction - the Sun check? Over.

04 06 19 19 LMP (EAGLE)
Roger. AGS residuals: minus 0.1, minus 0.2, minus 0.7. And we used the PGNS NOUN 86 for DELTA-VZ which was 9.5, versus yours which was 9.1, and I believe that may explain the difference. Apogee 57.2, perilune 9.1, Sun check to three marks, NOUN 20, minus NOUN 22, plus 0.19, plus 0.16, plus 0.11. Over.

04 06 19 54 CC
Roger. Copy. Looks great.

04 06 22 37 CC
Columbia, Houston. We've lost Eagle again. Have him try the high gain. Over.

04 06 22 46 CMP (COLUMBIA)
Eagle, this is Columbia. Houston lost you again. They're requesting another try at the high gain.

04 06 23 57 CC
Eagle, Houston. We have you now. Do you read? Over.

04 06 24 02 LMP (EAGLE)
Loud and clear.

04 06 24 04 CC
Roger. We see your VERB 47.

04 06 24 12 LMP (EAGLE)
Yes. I don't know what the problem was there. It just started oscillating around in yaw. According to the needle, we're picking up a little oscillation right now, as a matter of fact.

04 06 24 23 CC
Roger. We'll work on it.

04 06 24 38 CDR (EAGLE)
Horizon checklist right on time.

04 06 24 41 CC
Roger.

04 06 24 45 LMP (EAGLE)
Did you copy the star - I mean the Sun check, Charlie?

04 06 24 48 CC
That's affirmative. We did, Buzz. Out.

04 06 25 35 CC
Eagle, Houston. The AGS initialization looked good to us. Over.

04 06 25 43 LMP (EAGLE)
Roger.

04 06 26 28 CDR (EAGLE)
Our radar checks indicate 50,000 foot perilune. Our visual altitude checks steadying out at about 53,000.

04 06 26 37 CC
Roger. Copy.

04 06 26 55 LMP (EAGLE)
And, Houston, we got a 500 alarm early in the program. Went to DESCENT 1, proceeded on it, and we're back at AUTO again. Over.

04 06 27 06 CC
Roger. We saw that, Buzz. Thank you much. Out.

04 06 27 09 LMP (EAGLE)
All right. I say again - Okay. That wasn't an alarm; that was a code. Okay.

04 06 27 14 CC
Roger. We saw that.

04 06 27 22 CC
Eagle, Houston. We recommend you yaw 10 right. It will help us on the high gain signal strength. Over.

04 06 28 08 CC
Eagle, Houston. If you read, you're GO for powered descent. Over.

04 06 28 18 CMP (COLUMBIA)
Eagle, this is Columbia. They just gave you a GO for powered descent.

04 06 28 22 CC
Columbia, Houston. We've lost them on the high gain again. Would you please - We recommend they yaw right 10 degrees and reacquire.

04 06 28 34 CMP (COLUMBIA)
Eagle, this is Columbia. You're GO for PDI and they recommend you yaw right 10 degrees and try the high gain again.

04 06 28 46 CMP (COLUMBIA)
Eagle, you read Columbia?

04 06 28 48 LMP (EAGLE)
Roger. We read you.

04 06 28 49 CMP (COLUMBIA)
Okay.

04 06 28 51 CC
Eagle, Houston. We read you now. You're GO for PDI. Over.

04 06 28 57 LMP (EAGLE)
Roger. Understand. AELD control circuit breakers. DECA GIMBAL AC - closed?

04 06 29 07 CDR (EAGLE)
What?

04 06 29 08 LMP (EAGLE)
DECA GIMBAL AC - closed? Circuit breaker? COMMAND OVERRIDE - off? GIMBAL ENABLE? RATE SCALE - 25.

04 06 29 23 CC
Eagle, Houston. Your alignment is GO on the AGS. On my Mark, 3 30 until ignition.

04 06 29 29 LMP (EAGLE)
Roger.

04 06 29 33 CC
Mark.

04 06 29 34 CC
3 30 until ignition.

04 06 29 38 LMP (EAGLE)
Roger. Copy. Thrust translation - four jets - Balance couple - ON. TTCA throttle - MINIMUM. Throttle - AUTO CDR. Prop button - RESET. Prop button. Okay. ABORT/ABORT STAGE - RESET. ATT CONTROL - three of them to MODE CONTROL. 0kay, MODE CONTROL is set. AGS is reading 400 plus 1. Standing by for ...

04 06 30 45 LMP (EAGLE)
Hit VERB 77?

04 06 31 04 LMP (EAGLE)
Okay. Sequence camera coming on.

04 06 31 32 CC
Eagle, Houston. If you'd like to try high gain, pitch 212, yaw 37. Over.

04 06 31 45 LMP (EAGLE)
Roger. I think I've got you on high gain now.

04 06 31 49 CC
Roger.

04 06 32 03 LMP (EAGLE)
Say again the angles, though.

04 06 32 05 CC
Roger.

04 06 32 06 LMP (EAGLE)
I'll set them in to use them before we yaw around.

04 06 32 08 CC
Roger. Pitch 212, yaw plus 37.

04 06 32 24 LMP (EAGLE)
OMNI's in.

04 06 33 09 LMP (EAGLE)
... 10 ... 10 percent ...

04 06 33 41 CC
Columbia, Houston. We've lost them. Tell them to go aft OMNI. Over.

04 06 33 51 CMP (COLUMBIA)
They've lost you. Use the OMNI's again.

04 06 34 01 LMP (EAGLE)
...

04 06 34 05 CMP (COLUMBIA)
Say again, Neil?

04 06 34 07 LMP (EAGLE)
I'll leave it in SLEW. Relay to us. See if they have got me now. I've got good signal strength in SLEW.

04 06 34 13 CMP (COLUMBIA)
Okay. You should have him now, Houston.

04 06 34 16 CC
Eagle, we've got you now. It's looking good. Over.

04 06 34 23 CC
Eagle - -

04 06 34 24 LMP (EAGLE)
- - descent looks good.

04 06 34 25 CC
Eagle, Houston. Everything is looking good here. Over.

04 06 34 29 LMP (EAGLE)
Roger. Copy.

04 06 34 34 CC
Eagle, Houston. After yaw around, angles: S band pitch, minus 9, yaw plus 18.

04 06 34 46 LMP (EAGLE)
Copy.

04 06 34 59 LMP (EAGLE)
AGS and PNGS agree very closely.

04 06 35 01 CC
Roger.

04 06 35 14 LMP (EAGLE)
Beta ARM. Altitudes are a little high.

04 06 35 45 LMP (EAGLE)
Houston. I'm getting a little fluctuation in the AC voltage now.

04 06 35 51 CC
Roger.

04 06 35 52 LMP (EAGLE)
Could be our meter, maybe, huh?

04 06 35 54 LMP (EAGLE)
Stand by, Looking good to us. You're still looking good at 3, coming up 3 minutes.

04 06 36 13 LMP (EAGLE)
... real good .... about on.

04 06 36 18 CDR (EAGLE)
Our. position checks downrange show us to be a little long.

04 06 36 21 CC
Roger. Copy.

04 06 36 24 LMP (EAGLE)
AGS has gone about 2 feet per second greater ...

04 06 36 36 CDR (EAGLE)
... ought to be ... Stand by.,

04 06 36 43 LMP (EAGLE)
Altitude ...

04 06 37 00 LMP (EAGLE)
... it's going to stop.

04 06 37 18 CC
Eagle, Houston. You are GO to continue - -

04 06 37 19 LMP (EAGLE)
... closed ... GO ... at 4 minutes.

04 06 37 22 CC
Roger. You are GO - You are GO to continue powered descent. You are GO to continue powered des cent.

04 06 37 30 LMP (EAGLE)
Roger.

04 06 37 35 CC
And, Eagle, Houston. We've got data dropout. You're still looking good.

04 06 38 04 LMP (EAGLE)
... PGNS. We got good lock-on. Altitude lights OUT. DELTA-H is minus 2 900.

04 06 38 18 CC
Roger. We copy.

04 06 38 20 LMP (EAGLE)
Got the Earth right out our front window.

04 06 38 23 CDR (EAGLE)
Houston, you're looking at our DELTA-H?

04 06 38 25 CC
That's affirmative.

04 06 38 26 CDR (EAGLE)
PROGRAM ALARM.

04 06 38 28 CC
It's looking good to us. Over.

04 06 38 30 CDR (EAGLE)
It's a 1202.

04 06 38 32 LMP (EAGLE)
1202.

04 06 38 48 CDR (EAGLE)
Give us a reading on the 1202 PROGRAM ALARM.

04 06 38 53 CC
Roger. We got - We're GO on that alarm

04 06 38 59 CDR (EAGLE)
Roger. P30.

04 06 39 01 CC
6 plus 25, throttle down - -

04 06 39 02 LMP (EAGLE)
Looks like about 820 -

04 06 39 03 CC
- - 6 plus 25, throttle down.

04 06 39 06 CDR (EAGLE)
Roger. Copy. 6 plus 25.

04 06 39 14 LMP (EAGLE)
Same alarm, and it appears to come up when we have a 1668 up.

04 06 39 17 CC
Roger. Copy.

04 06 39 23 CC
Eagle, Houston. We'll monitor your DELTA-H.

04 06 39 24 LMP (EAGLE)
... worked out beautifully.

04 06 39 28 CC
DELTA H - -

04 06 39 29 LMP (EAGLE)
... looks good now.

04 06 39 30 CC
Roger. DELTA H is looking good to us.

04 06 39 34 LMP (EAGLE)
Ah! Throttle down - -

04 06 39 35 CDR (EAGLE)
Throttle down on time!

04 06 39 36 CC
Roger, We copy throttle down - -

04 06 39 37 LMP (EAGLE)
- - ... throttles down. Better than the simulator.

04 06 39 42 CC
Roger.

04 06 39 48 LMP (EAGLE)
AGS and PGNS look real close.

04 06 40 08 CC
At 7 minutes, you're looking great to us, Eagle.

04 06 40 13 LMP (EAGLE)
Okay. I'm still on SLEW so we may tend to lose as we gradually pitch over. Let me try AUTO again now and see what happens.

04 06 40 21 CC
Roger.

04 06 40 23 LMP (EAGLE)
Okay. Looks like it's holding.

04 06 40 24 CC
Roger. We got good data.

04 06 40 49 CC
Eagle, Houston. It's descent 2 fuel to MONITOR. Over.

04 06 40 55 CDR (EAGLE)
Going to 2.

04 06 41 01 LMP (EAGLE)
Give us an estimated switchover time please, Houston.

04 06 41 05 CC
Roger. Stand by. You're looking great at 8 minutes.

04 06 41 10 LMP (EAGLE)
At 7000 -

04 06 41 12 CC
Eagle, you've got 30 seconds to P64.

04 06 41 15 LMP (EAGLE)
... Roger.

04 06 41 27 CC
Eagle, Houston. Coming up 8 30; you're looking great.

04 06 41 35 LMP (EAGLE)
P64.

04 06 41 37 CC
We copy.

04 06 41 51 CC
Eagle, you're looking great. Coming up 9 minutes.

04 06 42 05 CDR (EAGLE)
Manual attitude control is good.

04 06 42 08 CC
Roger. Copy.

04 06 42 10 CC
Eagle, Houston. You're GO for landing. Over.

04 06 42 17 LMP (EAGLE)
Roger. Understand. GO for landing. 3000 feet. PROGRAM ALARM.

04 06 42 19 CC
Copy.

04 06 42 22 LMP (EAGLE)
1201

04 06 42 24 CDR (EAGLE)
1201.

04 06 42 25 CC
Roger. 1201 alarm. We're GO. Same type. We're GO.

04 06 42 31 LMP (EAGLE)
2000 feet. 2000 feet. Into the AGS, 47 degrees.

04 06 42 35 CC
Roger.

04 06 42 36 LMP (EAGLE)
47 degrees.

04 06 42 41 CC
Eagle, looking great. You're GO.

04 06 42 58 CC
Roger. 1202. We copy it.

04 06 43 01 LMP (EAGLE)
35 degrees. 35 degrees. 750. Coming down to 23.

04 06 43 07 LMP (EAGLE)
700 feet, 21 down, 33 degrees.

04 06 43 11 LMP (EAGLE)
600 feet, down at 19.

04 06 43 15 LMP (EAGLE)
540 feet, down at - 30. Down at 15.

04 06 43 26 LMP (EAGLE)
At 400 feet, down at 9.

04 06 43 29 LMP (EAGLE)
... forward.

04 06 43 32 LMP (EAGLE)
350 feet, down at 4.

04 06 43 35 LMP (EAGLE)
30, ... one-half down.

04 06 43 42 LMP (EAGLE)
We're pegged on horizontal velocity.

04 06 43 46 LMP (EAGLE)
300 feet, down 3 1/2, 47 forward.

04 06 43 51 LMP (EAGLE)
... up.

04 06 43 52 LMP (EAGLE)
On 1 a minute, 1 1/2 down.

04 06 43 57 CDR (EAGLE)
70.

04 06 44 04 LMP (EAGLE)
Watch your shadow out there.

04 06 44 07 LMP (EAGLE)
50, down at 2 1/2, 19 forward.

04 06 44 13 LMP (EAGLE)
Altitude-velocity light.

04 06 44 16 LMP (EAGLE)
3 1/2 down, 220 feet, 13 forward.

04 06 44 23 LMP (EAGLE)
11 forward. Coming down nicely.

04 06 44 24 LMP (EAGLE)
200 feet, 4 1/2 down.

04 06 44 26 LMP (EAGLE)
5 1/2 down.

04 06 44 31 LMP (EAGLE)
160, 6 - 6 1/2 down.

04 06 44 33 LMP (EAGLE)
5 1/2 down, 9 forward. That's good.

04 06 44 40 LMP (EAGLE)
120 feet.

04 06 44 45 LMP (EAGLE)
100 feet, 3 1/2 down, 9 forward. Five percent.

04 06 44 51 LMP (EAGLE)
...

04 06 44 54 LMP (EAGLE)
Okay. 75 feet. There's looking good. Down a half, 6 forward.

04 06 45 02 CC
60 seconds.

04 06 45 04 LMP (EAGLE)
Lights on. ...

04 06 45 08 LMP (EAGLE)
Down 2 1/2. Forward. Forward. Good.

04 06 45 17 LMP (EAGLE)
40 feet, down 2 1/2. Kicking up some dust.

04 06 45 21 LMP (EAGLE)
30 feet, 2 1/2 down. Faint shadow.

04 06 45 25 LMP (EAGLE)
4 forward. 4 forward. Drifting to the right a little. Okay. Down a half.

04 06 45 31 CC
30 seconds.

04 06 45 32 CDR (EAGLE)
Forward drift?

04 06 45 33 LMP (EAGLE)
Yes.

04 06 45 34 LMP (EAGLE)
Okay.

04 06 45 40 LMP (EAGLE)
CONTACT LIGHT.

04 06 45 43 LMP (EAGLE)
Okay. ENGINE STOP.

04 06 45 45 LMP (EAGLE)
ACA - out of DETENT.

04 06 45 46 CDR (EAGLE)
Out of DETENT.

04 06 45 47 LMP (EAGLE)
MODE CONTROL - both AUTO. DESCENT ENGINE COMMAND OVERRIDE - OFF. ENGINE ARM - OFF.

04 06 45 52 LMP (EAGLE)
413 is in.

04 06 45 57 CC
We copy you down, Eagle.

04 06 45 59 CDR (TRANQ)
Houston, Tranquility Base here.

04 06 46 04 CDR (TRANQ)
THE EAGLE HAS LANDED.

04 06 46 06 CC
Roger, Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot.

04 06 46 16 CDR (TRANQ)
Thank you.

04 06 46 18 CC
You're looking good here.

04 06 46 23 CDR (TRANQ)
Okay. We're going to be busy for a minute.

04 06 46 25 LMP (TRANQ)
MASTER ARM, ON. Take care of the ... I'll get this ...

04 06 46 38 LMP (TRANQ)
Very smooth touchdown.

R. Neal's picture

You notice in the transcript

You notice in the transcript that they had trouble keeping radio communications up. It was later determined that a shield added near a thruster nozzle was blocking the antenna. Instructions for the Astronauts to adjust the lander's flight orientation corrected for the problem.

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