Dr. Butler Hine is the project manager of the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft. The vehicle, successfully launched in September, will characterize the dust environment of the moon.
NASA Tech Briefs: What is the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft?
Dr. Butler Hine: It’s a small robotic orbiter. We launched on September 6 on a Minotaur V rocket. We’re currently in phasing loops around the Earth. We’re on our way to the moon, and once we get there, we’re going to check out our science instruments and do an optical laser-com experiment. We’ll drop down into a very low orbit and do our science missions.
NTB: What instruments are on the LADEE spacecraft?
Hine: We have three science instruments. One is a neutral mass spectrometer from NASA Goddard. One is an ultraviolet visible spectrometer from NASA Ames, and the third instrument is an in situ dust detector that was built by the University of Colorado.
NTB: You’re testing the instruments at this point?
Hine: They haven’t been activated yet. We’re still in the cruise phase on the way to the moon. We’ll start doing early checkouts of the instruments a little later in the cruise phase, but after we do our capture burn to get us into lunar orbit and go into our commissioning orbit, that’s when the science instruments will be extensively checked out and prepared for their science phase.
NTB: What does LADEE do, and why is it important?
Hine: There is a leftover question from the early Surveyor and Apollo days. The astronauts saw evidence of streaks or glow as the terminator approached, and there are a lot of theories about what this is. One of the theories is that you have elevated dust that occurs when the terminator passes. This is a very interesting scientific question. It [relates] to the transport mechanisms around the moon, how material moves around the moon, and collects in various places.
LADEE will fly several times a day during the mission, and try to measure the dust levels and characterize the dust. We’re also looking at elements: atoms, molecules, and various elements around the lunar atmosphere. It’s actually an exosphere, a collisionless atmosphere. It’s of interest for scientific purposes in its own right, but it’s also of interest to determine how transport mechanisms can carry material around the moon.
The previous Lunar CRater Observation and Sensing Satellite (LCROSS) mission confirmed water ice at the permanently shadowed pole on the moon. One of the questions is: How does that material get there, so we’re trying to help answer the questions of transport material around the moon.
NTB: How does it collect the data? And how quickly does it collect the data?
Hine: We orbit the moon about 13 times every terrestrial day, so during that time, we fly into and out of the terminators on both sides: the dawn terminator and the dust terminator. At those points, at local midnight and local noon, the instruments are activated in various sequences to make their measurements. The neutral mass spectrometer is measuring the environment right around the spacecraft, trying to detect atoms and molecules. The dust detector is measuring the dust impacts as we fly through the environment. The ultraviolet visible spectrograph is a remote sensing instrument. We use that to watch for the absorption of spectrographic lines against the sun as the sun sets or rises behind the moon.
NTB: The spacecraft was successfully launched at 11:27 p.m. EDT Friday, Sept. 6. Can you talk about the launch? Did all go as expected?
Hine: We launched on a Minotaur V rocket out of Wallops, Virginia. That’s a lot of firsts; this is the first flight of a Minotaur V. It’s a five-stage derivative of a Peacekeeper ICBM [missile]. The first three stages are assets from the Air Force, which are repurposed for civilian use. Those three stages are an ICBM, and then Orbital Sciences, under contract with the Air Force, added a fourth stage to make it a Minotaur IV. We added a fifth stage to make it a Minotaur V, because we needed not only the capability of going into Earth orbit; we actually needed a kick stage to get us into trans-lunar injection trajectory.
So we launched out of Wallops. It’s one of the launch locations that you can use for peacekeeper missiles, and we wanted a spot that could launch us eastward. That’s a safe location from Wallops to launch us out over the ocean, and it was a spectacular launch. It achieved exactly the orbit we needed. In fact, it did not give us a hot or cold insertion. It gave us a pretty much perfect insertion on Sept 6. So we were really happy.
NTB: What has been your day-to-day work with LADEE? And how does that change now?
Hine: Before launch, it was all about the development of the spacecraft, the development of the launch vehicle, the range preparations. We spent all summer out at Wallops doing testing of the spacecraft and integration with the fifth stage and encapsulation into the fairing. We spin balanced it. We checked out its propulsion system.
In the meantime, back at Ames, the mission ops team was doing readiness testing. They were doing rehearsals, they were doing simulations, they were getting ready to operate the spacecraft. And then after launch, all of that changes. You’re no longer in development. You’re actually flying the spacecraft.
Since Friday night, we’ve been very busy doing the initial characterization and tests of all the subsystems on the spacecraft: learning how to fly it, learning all the quirks that you suspect on the ground but never can confirm until you actually get into space. We had our first main engine burn yesterday [Sept. 12] to characterize the main engine and make sure that we could depend on it before we really needed to do the burns for real.
NTB: What were some of the other “quirks” that you noticed?
Hine: Right after we launched, when we first woke up, we noticed the reaction wheels were off. That was because of our fault protection system. It actually did its job. It detected something that it didn’t like and turned off the reaction wheels. Of course, when you’re first waking up after a launch, that gets your attention right away. So that took us about two hours after launch to figure out the proper settings for the fault protection system, and then rest the wheels and turn them on. After that we were operating just fine, but I think it was on Monday, we were in a thermal conditioning mode prior to doing one of our test burns, and in that thermal conditioning mode, we went into safe mode because of the two star-tracker cameras onboard. When the sun was going through the field of view on one of the star trackers, an alignment offset between the two star trackers made the spacecraft think that it had an anomaly. Of course, fault protection is designed to “safe” the spacecraft anytime it sees something that’s unusual. We went into safe mode there, and we discovered what the issue was with the alignment offset, the cameras, and uploaded a new alignment matrix to the spacecraft, which took care of that. Those are the kinds of things that you do when you first wake up and are first characterizing your spacecraft.
NTB: What are your next priorities now that you’ve had a successful launch?
Hine: The next big event is on Friday [September 13]. We’re going to do a perigee maneuver. The way we get to the moon is not a direct trajectory. We go into these elliptic orbits around the earth, and with each orbit, we boost the apogee. By the third orbit, we boosted the apogee far enough where the moon swings by and captures us. We’ve done our first apogee, and now coming up on Friday is our first perigee. At that maneuver, we will do the burn of the main engine and boost our elliptic orbit, but a little higher. So we do three of those before we get to the moon. Right now we’ll do those elliptic orbits for the next couple weeks and then starting Oct. 6, we’ll do our lunar orbit insertion maneuvers.
NTB: Looking back to the summer when you were building this, what would you say were your biggest technical challenges?
Hine: Whenever you have a small spacecraft and a big engine, one of the things you worry about is whether you’re precisely lined up on the center of gravity. So one of the big activities this summer was to spin balance it, and that means you take the spacecraft dry and you put it up on this spin table and you spin it at high speeds. So it’s kind of a nerve-racking moment. You’re taking your “baby” and spinning it very fast. Then we balance it. We do precise balancing of it to get the thruster alignment right over the CG. Then you fill it with fuel, which is also very exciting, because you’re actually putting fuel and oxidizer in the tanks, and then we spin it again because we want to make sure that the thrust alignment is along the center of gravity with a full fuel tank. Those were the most exciting moments this summer were spinning and then fueling the spacecraft.
NTB: How will this work help guide future missions?
Hine: We have a laser communications experiment on board. This is a very promising technology that’s going to be important for NASA in the future. The laser comm onboard the spacecraft will talk to the Earth and transmit data at roughly 622 megabits per second from the moon. That’s kind of the heart of an interplanetary trunk line, where instead of radio communications, we can use optical communications and get a whole lot of bandwidth back. That’s an important technology, and that’ll be used for lots of missions in the future.
As far as the science that we’re getting with our science instruments, any type of basic science to understand the environment of the bodies you visit will help future spacecraft. [LADEE will] characterize the dust environment of the moon, so that when we send other spacecraft to the moon, we’re more aware of any problems or issues and can design around them.
NTB: What is your favorite part of the job, specifically working with LADEE?
Hine: I enjoyed the whole thing. I have a phenomenal team, and working with these people has been a real joy. This is a really hard working group, and I really enjoy every moment working with these folks.
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