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Fri September 6, 2013
NASA Craft to Sniff Moondust, Test Laser Broadband
Originally published on Fri September 6, 2013 5:20 pm
IRA FLATOW, HOST:
This is SCIENCE FRIDAY. I'm Ira Flatow. Back in 1972, during Apollo's final mission to the moon, Apollo 17 astronaut Gene Cernan spotted a strange phenomenon, a glow along the horizon of the moon just before sunrise, followed by mysterious streamers of light, sort of like, you know, the rays of sunlight you see peaking through a cloud. Well, he made a sketch describing it, and since then, scientists have been trying to figure out what the heck he saw.
And tonight, NASA is launching a mission that might get to the bottom of that, might explain that mystery. It's called the Lunar Atmosphere and Dust Environment Explorer or LADEE, and they'll also be the first test of a space-based broadband. Yeah, it's going to be shooting wideband data back to Earth riding a laser beam. Richard Elphic is LADEE project scientist at NASA Ames Research Center in Moffett Field, California. He joins us today from Wallops Island, Virginia, where the orbiter will launch, scheduled for 11:27 p.m. Eastern time. Welcome to SCIENCE FRIDAY.
RICHARD ELPHIC: Thanks, Ira. Good to be here.
FLATOW: Are we going to be able to see that launch along the East Coast here?
ELPHIC: Oh, boy, you should be able to see it all up and down the coastline from Maine all the way south to parts of South Carolina.
FLATOW: Eleven - almost - get out there about 11 so your eyes are used to it, and you'll be able to see it.
ELPHIC: Yeah. It should be pretty bright. And if your skies are clear, you should be able to see it that far away from the launch site.
FLATOW: So the LADEE is going to be sniffing the very thin lunar atmosphere, will it not? I don't think people realize it even has an atmosphere.
ELPHIC: Yeah. We're all taught from an early age that the moon has no atmosphere, but in fact, that's not true. It has a very thin, tenuous atmosphere that's composed of rather exotic species. It's very unlike our own atmosphere. It has - we know for a fact that it has sodium, for instance, as a gas and potassium as a gas and argon and helium. But we don't know what else is there, and we suspect there are plenty of other culprits in there. But it's very, very, very thin.
And it's insubstantial enough that it can't loft dust, and that's what made Gene Cernan's observations of these rays, these sunset rays or sunrise rays so mysterious. And so the going hypothesis then, this is indeed loft of dusts that must be a special mechanism that lofts it like electric forces.
FLATOW: Wow. Getting spooky.
FLATOW: You mean electric - you mean static electric forces or...
ELPHIC: Exactly, yeah. The place where we saw it was a transition from sunlight to darkness where the sun is actually going up on the moon. And in locations like that, the surface of the moon that's exposed to sunlight is actually positively charged, and places that are in darkness are negatively charged. So when you've got differences like that, electric fields can be strong, and they can in fact loft dust particles that are also charged to some levels, some high altitude. And so that's been the going hypothesis all these years for the last 40 years that that's the explanation, but we don't know for sure.
FLATOW: Will LADEE be able to solve that mystery for us?
ELPHIC: It will at least put to bed the question of whether it's actually dust particles that are up there at high altitudes because we have two instruments that are aimed specifically at answering that question. One actually is the Lunar Dust Experiment, and it captures dust particles as LADEE flies through them. So there's no escaping LDX. It will be able to analyze each and every particle that it runs into. The other instrument that can address this question is the Ultraviolet Invisible Light Spectrometer, which can gaze from a distance and see the scattered light from this - so the same thing that Gene Cernan was looking at - and analyze the spectrum of it and get to the bottom of what could be behind that glow.
FLATOW: And tell us about is laser communications system.
ELPHIC: Ah, the laser comm system is a whole new way of doing communications from deep space. It uses infrared laser light which has intrinsically just a lot more capacity to transmit information. In fact, it's the same thing that's used in fiber optics here on Earth to transmit broadband information on the Internet into your homes. So we're basically trying to get that capability into space so we can telemeter down things like HD imagery and huge volumes of data that we take of other planets. For LADEE, we're going to test it and see that it indeed works and really open the door to this possibility for future missions.
FLATOW: So you're going to beam a laser beam back to Earth from the moon?
ELPHIC: That's correct, yes.
FLATOW: Now, it starts out as a tiny little beam. How big is it by the time it hits the Earth?
ELPHIC: Right. It's about four inches across when it's transmitted from LADEE, but by the time it gets to Earth, it's going to be two to three miles across at the ground station. So it's dispersed pretty widely. And that means it becomes, in fact, a little bit harder to target than radio waves, which can be spread out over at a much larger distance.
So the trick is going to be to - for the laser communication system on LADEE to pickup a probing beam from the ground station and then tell the ground, indeed, we saw the beam and then make the two-way transfer possible. So it's uploaded and downloaded, just as you would do in the Internet.
FLATOW: Wow. And ironically, LADEE is going to eventually crash into the moondust it's exploring?
ELPHIC: Yes. That's true. It's the fate of a vehicle that has a limited amount of fuel traveling around the moon, which has a very lumpy gravity field that causes all kinds of perturbations. And without fuel to maintain the orbit - to adjust the orbit periodically, as we will be doing in the course of the mission, it must inevitably run into the surface, and it will do so. But we will do it in a controlled fashion. And we'll be taking data all the way down. So if there's dust at lower altitudes, we'll be able to measure that before we impact.
FLATOW: All right. Tonight, 11:27 schedule. Is there a launch window you have to hit? Or?
ELPHIC: It's about a four-minute long window tonight. If we scrub for some reason tonight, tomorrow night is another window that opens. It's actually a longer window. It's a 15-minute long window in which we can launch and similar the night after that. So we have a block of about five days during which we can actually launch the spacecraft and get to the moon at basically exactly the same date on October 6, 2013.
FLATOW: Well, here's wishing you good luck tonight and hopefully we all can get out and see that.
ELPHIC: Thanks very much, Ira. I encourage everybody to go out and take a look because this is going to be spectacular.
FLATOW: Richard Elphic is a LADEE project scientist at NASA Ames Research Center in Moffett Field, California. Transcript provided by NPR, Copyright NPR.