 Greetings and welcome to the Introduction to Astronomy. In this week's Exploration of the Solar System, we are going to talk about three spacecraft, Luna 1 through 3, which began our very early exploration of our Moon. So, let's take a look at these craft. And what we have is that the very first craft was Luna 1, which was launched January 2, 1959. Now, if you think about that, that's a pretty good jump from October of 1957, which was the launch of Sputnik 1, the very first craft into Earth orbit. And here, well, less than two years, only a little over a year and a few months later, we were traveling to the Moon. And at least sending a very small craft, and you may see its resemblance to Sputnik 1 here. Now, the whole idea of Luna 1 was to crash it into the Moon. However, there was a maneuvering failure, and that failed, so it actually passed by the Moon at a relatively large distance. But it did give us something very important, which was the first direct observation of the solar wind. Now, we can't detect the solar wind here on Earth. We can see its effects in the aurora, but you can't detect it because our magnetic field buffers all of those particles away. So here we could get the first measurements of the intensity of that solar wind. Now, following on that, Luna 2 was launched in September of 1959, and this was the first craft to actually impact on another celestial object. It actually impacted on the Moon and crashed into its surface. Now, we were able to see that then from Earth Observatory, so it was actually visible from Earth Observatories. Now, finally, Luna 3, launched in October of 1959, gave us the very first images of the far side of the Moon. Now, when we think about that, the far side of the Moon is never visible from Earth. It always points away from Earth in its orbit. So even though the Moon is our closest neighbor, this is something that had never been seen in history. This was the first time it had ever been seen. And the difficulties here, if you think about it in the 1950s, was sending specific cameras to be able to image the Moon and then to be able to develop that film, using old 35-millimeter film, to be able to develop that and then to scan the photograph, to do a kind of scan of it and transmit that back to Earth. So while the image may look horrible compared to images we have today, it was still an amazing view of the far side of the Moon, something that no one had ever seen before. So let's go ahead and finish up with our summary. And what we've looked at this time is the Luna 1 through 3 were the earliest craft to travel to and study our Moon. Luna 2 was the first man-made object to impact on any other celestial object. And Luna 3 gave us our very first view of the far side of the Moon. So that concludes this discussion of the Luna 1 through 3 spacecraft. We'll be back again next time for another lecture on exploration of the solar system. So until then, have a great day, everyone, and I will see you in class.