 Greetings and welcome to the Introduction to Astronomy. In this week's Exploration of the Solar System, we are going to look at the Surveyor series of spacecraft, in fact, Surveyers 1 through 7, which were some of the earliest exploration of the Moon by the United States. So let's take a look at what these were. It was a total of seven spacecraft launched between May of 1966 and January of 1968. The landing sites are shown in the yellow here. So you can see those landing sites for 1, 3, 5, 6, and 7. And note that 2 and 4 were unsuccessful. So what we were looking at here, what we were trying to do, well, this is getting prepared for the Moon landings. We know that the Moon landings were only a couple of years after this time. So we wanted to demonstrate the possibility of soft landing on the Moon successfully. In preparation for the human landings, which would be only about a year and a half after the last Surveyor mission. And one of the things we wanted to know was how deep was the lunar soil. And that was something that was looked at here. And we can see the soil here as we have the landing foot of the craft. And you can see that it did penetrate into the lunar soil a little bit, but not tremendously. We did not know how thick that lunar soil was or how quick the craft would sink into it. So this was something very important that we wanted to know before humans landed on the Moon. How successful was it going to be? How easy was it going to be to land on them? And of course, we also wanted to evaluate possible landing sites. Where could we land on the Moon for these first missions? Now what we saw was, first of all, we actually had a couple of other things going on with these Surveyor missions. And in fact, Surveyor 6 was the very first craft to lift off from another world. How far did it lift off? Not very much. It lifted off again and moved about 10 feet. But again, this is all preparation for the Moon landings, what you're coming up. So we wanted to be able to see how easy it was going to be to lift off that surface and not necessarily in this case get back into orbit, but enough fuel to be able to lift up from one location and then re-land in another location nearby. Now that was Surveyor 6, which was the first craft to actually lift off from some place other than Earth. And the other one that was actually studied again was the Surveyor 3 craft. It was actually studied by the astronauts at the Apollo 12 mission. So here we have an image from the Apollo 12 mission. We have the Apollo module off here in the distance. So that is the landing module of Apollo 12. And the astronaut here is examining Surveyor 3, which of course had explored the Moon a couple of years before. And we could see that and actually check some of the equipment to verify that. So it was actually planned to land one of the craft, one of the lunar landings was planned to be relatively close to this and in fact close enough that the astronauts could walk to the Surveyor craft and inspect it to be able to get a better understanding of what it had been like to be on the Moon for a couple of years. So let's go ahead and finish up here with our summary. And what we've looked at with the Surveyor craft is that they were a set of seven craft that were sent to soft land on the Moon. Five of these were successful and it did give us, tell us that it was feasible to soft land on the Moon and to lift off again as we saw with Surveyor 6. Surveyor 3 was actually visited a couple of years later by the astronauts from the Apollo 12 mission. So that concludes this lecture on the Surveyor 1 through 7 craft and we'll be back again next week for another exploration of the solar system. So until then, have a great day everyone and I will see you in class.