MSC-07631 09. Separation through LM touchdown

[edit] 9.1 Command Module

Evans

In optics tracking, I tracked RP-3 which is about 5 minutes prior to the subsolar point. And that's too close to the subsolar point to be doing any optics tracking. As soon as I got to the TCA on that thing, I completely lost the visibility of the landmark. So the only good marks on that are going to be prior to TCA.

Cernan

What was that landmark?

Evans

That was the landmark for updating the mapping camera film. Actually, it is a recalibration of those particular points that had been tracked on previous launches.

The circularization burn was a good burn. The only anomalous-type thing on that is that the residuals prior to trimming were plus 1.70 and minus 0.6. The minimum impulse is a 4-second burn. It underburned in the minimum-impulse case by 1.7 ft/sec. It turned out to be no problem. The ORDEAL worked as advertised throughout the flight.

[edit] 9.2 Lunar Module

Cernan

Prep for PDI - just went out of the Activation Checklist into the Timeline Book. There are no notes concerning any anomalies. We stayed on the time line and as I said, we met the milestones with the ground. We came around the horn for PDI and established comm, and the ground had a load waiting for us. We had no NOUN 69 prior to P63.

Schmitt

We did have the communications problem prior to PDI. The thing that started it off was the ground started up-linking on the omni, which they had never done before in the sims that I remember, unless it was a situation where we hadn't gotten the steerable. They started on the omni. I was not watching that, and I switched out of the omni to the steerable in the middle of the up-link. That started the problem, which apparently was compounded, as I found out last night. Anyway, the Goldstone antenna went belly up somehow, and the men who talked to me last night still do not know how. Somebody may, and I'm sure it'll be worked out. The up-link did get in and all you had to do was proceed on the VERB 33. We did have a good up-link, and that whole thing was in there but nobody's quite sure how it actually got in there. The ground surprised us by coming up almost immediately with that up-link, which we've never seen before. In fact, I expected it would be quite late.

Cernan

We'd seen them come up fast, but they always waited for the steerable.

Schmitt

Yes. That's what caught me by surprise. At any rate, we got it in there and there was no subsequent problem. The comm thing did delay us, and we were running a little bit behind the time line.

Let me mention one thing on the DPS start which I didn't mention yesterday. And that is monitoring 471 in the AGS showed essentially no Delta-V accumulation in Y. That was a good idea, although it was unnecessary.

Cernan

As far as the start was concerned, the LMP confirmed ullage. I had my physiological cue, and I knew we had ullage. I was prepared to back up the ullage and back up the start, but we got an automatic performance in both.

Schmitt

It was very clear that the SHe tank had opened up within a few seconds. We got our first jump in pressure a lot sooner than I expected.

Cernan

All the pyro functions prior to PDI in the LM we could verify with a physiological cue. We could feel, and/or hear all of these functions.

Schmitt

And this was suited.

Cernan

In some cases, it was suited; not all.

I covered the performance of the engine. The PGNCS performed admirably. I called up the NOUNs I needed: 68s and 92s. We loaded NOUN 69s, and she just spit them out just like she always has.

Schmitt

The SHe pressures during descent held low. About 30 psi, as I recall, beneath the predicted number.

Cernan

NOUN 69 was plus 3400 feet, and that sounded very familiar, as I recall. Didn't we almost always in the sims have a plus? Even the nominal ones have a plus. Is that the problem they had? As it turns out, as soon as I pitched over, I took it right back out to get to our landing area.

Schmitt

Is that right?

Cernan

It was almost exactly the same number, which means that their targeting was essentially perfect, because the planned landing area was about at least a crater diameter short of Camelot. That's where we pitched over and that's where we would have landed, which was the planned, targeted landing area.

We did not say anything about DOI-2. DOI-2 was slightly smaller than we'd seen in the past, because of the orbit degradation we were in. I think it went down to something like 11 miles, but the DOI-2 just went super. We got the residuals down to 00 and 0.1, something to that effect. We saw a 7.0 perilune out of the PGNCS and a 6.7 out of the AGS, which is exactly the type of thing we expected. We went around to PDI in good shape. We got excellent radar and VHF ranging correlation during that radar checkout.

VHF Ranging and Radar Tracking - Everything was nominal during PDI right through pitchover. We got throttledown on time. We watched the computer and followed NOUN 92. The computer was happy, the GDC was happy, and everything was just perfect. At 13,000 feet, I could look over the edge of the window and see the South Massif. At 13,000 feet, I knew we were coming down in the valley because I could see the South Massif, and I could tell that we were in the valley or coming into it. At 13,000 feet, I had the impression we were level with the top of those mountains. (Laughter) I really did.

We pitched over, the needles dropped, pitchover occurred, 64, everything was nominal. Our target point was about a crater diameter short of Camelot. I used LPD frequently. I don't know how many times I used LPD, several clicks back, a couple left, a couple right. I just flew it where I wanted to fly it. I brought it back to an area in the vicinity and to the right of Poppy. As soon as I did that, I just sort of tumbled in on that area and did some more LPDs to finally what I'd call a suitable landing site. That suitable landing site became more evident the closer you got. Initial LPD changes to bring the landing site back east were just gross to change the area.

Once I had my area, I started tweaking it up to find what I considered a blockless and level area. I ended up taking over in P66 just a little below 300 feet. The reason I took over is that I wanted to slow our forward velocity down. I did not want to go any farther west, because there were more blocks and more hummocky terrain. As a result of all of our aft LPDing, we ended up (1) with a great deal more fuel than we might have anticipated, between 7 and 9 percent, I believe, and (2) the rate of descent, H-dot, was a little bit higher than normal, because of our steeper descent in the latter phases of the braking and landing. But as far as the CDR was concerned, they were very comfortable rates of descent. The LMP passed them on and said they were a little higher. I knew where we were. I think the most significant part of the final phases from 500 feet down, as far as the CDR was concerned, was that it was extremely comfortable flying the bird, either LPDing in P64, and/or flying manually in P66. I contribute that primarily to the LLTV flying operations. That's why the rates of descent and what have you were just very comfortable.

I kept a good rate of descent down through 200 feet, slowed it down at a little bit over 100 feet to 1 or 2 feet per second, and then started it on down again. We started to get dust somewhere around 100 feet.

Schmitt

In my window, I didn't see dust until about 60 or 70 feet.

Cernan

The dust layer was so very thin that I could definitely see through it all the way down. It didn't hamper our operations at all. When I was satisfied that that was my landing site, I made sure we had between 1 and 3 feet per second on the crosspointer forward velocity, and to the best of my ability, zero left and right. We continued on down with about 3 feet per second to landing.

I saw the shadow come right on up to me, and this is very well done in the simulator. When it passed on under me, I was expecting a blue light. It seemed like it didn't quite come, when the shadow passed on under me for just a split second or two. We got the touchdown light. I had planned to say, "1 potato, 2" and then push the stop button. But I didn't. As soon as we got the touchdown light, I, like most everybody else, hit the stop button. Then things just went "plunk." We plunked down with a relatively good thud, I'd say.

Visibility through the final phase was excellent. The tendency, once you redefine your landing area, is to become a little bit less concerned with your peripheral landmarks out there, because you know now about where you're going to go. You get more tunnel vision, and you are concerned with finding these specific touchdown points within that landing area. That's effectively what I did. I had no Sun angle problems. At that point in time, estimation of distances didn't mean much, because I was concerned more with what was right down below me and in front of me.

I can't say enough for what I consider the accuracy of the guidance. Manual control of the spacecraft was hard and firm, different certainly than the command module operation but exactly what I expected the LM to be. The simulator, I think, does an excellent job of controlling the firm good solid ATTITUDE HOLD, RATE COMMAND capabilities. of the LM. I'd say that I touched down with about 1 to 3 ft/sec forward, and 0 left and right, and about 3 ft/sec down. We'll just have to find out what those numbers were. I don't know. The fuel remaining was between 7 and 9 percent. From the CDR's side, the systems were excellent.

---

Edits and errors by Eric Hartwell are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 2.5 license. The original NASA material is copyright-free.