Astronomy Cast Episode 115: The Moon Part 3 – Return to the Moon Fraser Cain: Hey Pamela, how is Europe? Dr. Pamela Gay: [Laughter] well this is a little bit of a cheat – we’re recording this 2 days before I leave but by the time you’re all hearing this, I should be over at Munich working on Portal to the Universe with its wonderful program lead, Lars Lindberg Christensen and getting ready to hopefully meet some of you on November 23rd at Mabel’s Tavern in London. Fraser: Alright, it’s time for the third Lunar chapter. We’ve talked about the physical characteristics of the Moon and exploration of the Moon and now we going to talk about plans to return to the Moon. From the current missions orbiting the Moon right now to the upcoming Lunar Reconnaissance Orbiter to the plans to have humans set foot on the Moon again for the first time in more than half a century. Let’s just bring everybody up to speed and let’s talk about who’s hanging out at the Moon right now. In late 2008, who’s at the Moon? Pamela: Well currently there is both a Japanese mission – Selene and a Chinese mission Chang’e and an Indian mission which I can’t Fraser: Say it. Pamela: Oh, it’s scary and I’m going to be made fun of but I will go for it for the sake of our audience. Forgive me Chandrayaan – 1, maybe? People really need to add pronunciations of the missions to their websites please a desperate plea from podcasters everywhere. Fraser: Let’s start with the – where do you want to start? Which mission? Pamela: Well, why don’t we go ahead and start with Selene since it’s one of the ones that have been up the longest. Fraser: a.k.a. Kaguya. Pamela: Yes, the mission with two names, one of which is more pronounceable than the other. Fraser: Right, so right now – and this is the Japanese Spacecraft that took those amazing high-definition movies of the Lunar surface and Earth rising over the horizon – if you haven’t seen them we’ll link to the show notes again. They’re awesome. What are the plans for the Kaguya right now? 1 Pamela: This is a mission that largely has proprietary data. They’re taking lots of gorgeous images, lots of laser altimetry, lots of science data and are holding on to their data for a fairly significant period of time to allow the Japanese scientists a chance to go through and get their data papers out before the rest of the world can get their hands on the data. This is fairly common with the very large array here in the United States. Scientists for instance get 6 months before their data goes public. They’re taking all of this amazing data, putting high-definition video on-line of things like the Earth rise over the Moon. Along the way they are working to try and better define the surface of the Moon and work on trying to define some of the chemistry of the Moon. There are a whole range of different instruments onboard, everything from a plasma analyzer looking for things in the atmosphere of the Moon to using a variety of different Doppler shift techniques to try and better map the mass density of the Moon. This is actually 3 different satellites that they have in orbit. One is a relay satellite and the other two are working together to do a variety of different radio measurements where as they fly over the surface of the Moon, one craft will first get accelerated by an overly dense region under the surface. Then the other one will get accelerated by this. By very carefully measuring the separation between the two different Spacecraft, they can map the density of stuff that we can’t see beneath the surface of the Moon and thus map the gravity of the Moon. They’re using these three different missions to better map out the Moon, to take very careful altimetry data by bouncing lasers off the surface off the Moon. This way you can go, ah this region looks flat but it’s denser, or rather it has a larger gravitational pull so you know it’s denser. You can look at regions and go ah, hill but less gravitational pull so it’s a less dense region. Fraser: Right and this is one of those problems that we had talked about in a previous episode. The gravity of the field of the Moon is very lumpy bumpy and if you’re trying to orbit a Spacecraft fairly low to the surface of the Moon it’s almost impossible to keep them in a stable orbit and they tend to crash. Pamela: And that’s a problem. They’re looking at things like what are reflected gamma rays coming off of the surface? Reflected is probably not quite the right word. When a Solar Flare hits the surface of the Moon you can get all sorts of neat reactions that throw off gamma rays. That helps us understand the chemistry of the Moon a bit better. 2 Basically they’re trying to open the door for the plans to eventually put men on the Moon. This is something that is going to come up over and over in the show is all these different countries that are currently flinging metal bits at the Moon. All have the goal of understanding the Moon a bit better so that they can understand how to put people on its surface a bit better in the future. Fraser: Let’s move on then and talk about the Chinese Spacecraft. Pamela: Chang’e is a whole lot more equipment. It has a neat stereo camera where they have two different CCDs separated that allow them to get a pseudo-stereo view – well it’s not pseudo – an actual stereo view of the surface. It’s not quite as impressive as what we get with the stereo mission with the Sun where you’re separating out the cameras on two different Spacecraft, but it’s still separated and gives us a new impression. Along with the stereo camera they have their own laser altimeter that again is working to measure the surface of the Moon. They have their own gamma ray and x-ray spectrometers. It’s a lot of the same instruments over and over again as each country tries to get their: who gets the better resolution with this; who gets the better resolution of that. Each country’s program has its own strengths and weaknesses. Fraser: Right and then the last one is the Indian one. What are the plans for that one? Pamela: It’s launched; I believe it injected itself into orbit this week. It’s another mission that is out to do high-resolution imagery. This one has a lot of different instruments that are focused to try and understand the chemistry of the surface of the Moon. It has what’s called a hyperspectral imager. This is similar in technology to some of the stuff that was used to study the surface of Mars. It’s going to allow us to start understanding what are the minerals on the surface of the Moon? Again, it has its own laser altimeter to measure the surface. They are also carrying their own little side-satellite that they’re going to fling at the surface of the Moon. It’s a Moon impact probe. It’s going to be ejected and basically it carries with it a picture of the Indian flag and it’s going to basically mark another nation’s presence at the surface of the Moon. Now this mission is also carrying a bunch of instruments that aren’t Indian- made. It’s carrying some ESA equipment, some NASA equipment, again looking to try and understand what the chemistry of the Moon is. There’s another mineral mapper – M3 built by Brown University and JPL. It’s carrying a near infrared spectrometer from ESA. It’s similar to the technology from Smart-1. 3 We’re learning how to re-use technology effectively to build more and more missions that get us more and more data by taking designs we used for one object and using them to study another object. Fraser: So, all of these missions are all going to suffer from the problem of orbiting the Moon, right? They’re not going to last too long. Pamela: It varies from mission to mission. So Selene has been in orbit for awhile. It ejected itself into orbit in 2007 and they’re planning to keep going for awhile. Current plans for Selene are that in August of 2009 they are going to de-orbit it rather violently impacting it into the surface. As far as I know – and it is hard to find information on these things on the web – there are similar plans to do the same with Chang’e. It’s just hard to keep things in long-term orbits around the Moon. There’s a lot of data to be gathered by impacting things and studying the plume. It’s possible by studying the plume of dust that comes up to start looking for water, to start looking at different facets of mineralogy. In fact that’s a good way to segue to our next mission LRO. Fraser: Right, so this is now a future mission.