Date: October 24, 2010
Title: EPOXI: Triple the Mission, Triple the Fun
Podcaster: Roz Brown & Tom Bank
Organization: Ball Aerospace & Technologies Corp. – www.ballaerospace.com
Description: On November 4, scientists anticipate ultra-close-up images of Comet Hartley 2 when the flyby spacecraft from NASA’s 2005 Deep Impact mission passes within 450 miles (700 kilometers) of the comet’s nucleus for the EPOXI mission. The flyby spacecraft was only designed for one mission, but is proving to be an orbiting workhorse when it comes to teaching us more about comets.
Bio: Ball Aerospace & Technologies Corp. supports critical missions of important national agencies such as the Department of Defense, NASA, NOAA and other U.S. government and commercial entities. The company develops and manufactures spacecraft, advanced instruments and sensors, components, data exploitation systems and RF solutions for strategic, tactical and scientific applications. Roz Brown is the Media Relations Manager for Ball Aerospace.
Today’s sponsor: This episode of “365 Days of Astronomy” is dedicated to Shelley Goldner by her husband in honor of 28 years of sunny days and starry nights together.
This episode of “365 Days of Astronomy” is also sponsored by Alice and Jason Enevoldsen, in honor of all the unborn future astronomers of the world.
Transcript:
Roz: I’m Roz Brown, here with Tom Bank, spacecraft systems engineer for Ball Aerospace on the EPOXI mission. Can you give us a broad view, Tom, of what the EPOXI mission is about?
Tom: The EPOXI mission is actually two missions. It’s the extended missions of the Deep Impact spacecraft that spectacularly impacted Temple 1 in 2005. After that successful encounter, NASA asked for proposals on what to do with the spacecraft next, and they selected two. The first was EPOCh, which was looking at planets orbiting around other stars, and the second was DIXI to fly by another comet.
Roz: So we’ve got the EPOCh mission and the DIXI mission – can you tell us a little more about each of those.
Tom: The EPOCh mission is run by Drake Deming out of the Goddard Space Flight Center and they are observing known giant planets looking for possible rings or moons, and they’re also searching for new planets in the system and finally they’re looking at some distant earth observations to calibrate what a planet might look like, orbiting around another star. Those observations were completed in August 2008. DIXI, the second part of the extended mission has yet to happen. On November 4, we’ll be flying by comet Hartley 2, much like the Deep Impact comet flyby, but without the impact, of course. We expect to get some great images from that comet.
Roz: I know you’ve been on this program for quite some time. Ball Aerospace launched the Deep Impact vehicle in 2005 – so the spacecraft has been up there for almost six years. Can you tell us what’s happening with the spacecraft?
Tom: Well, after the Tempel-1 encounter in July 2005, we did a burn to bring the spacecraft back to Earth’s vicinity, knowing we could use Earth’s gravity to sling-shot off to another target, should we be funded to do that. At that point we put the spacecraft into hibernation mode and we all went off and celebrated the success of the Tempel impact. Since then, NASA has awarded the EPOXI mission and we’ve all come back on the job. We’ve done our necessary course corrections to bring us on course for the Hartley 2 encounter.
Roz: So you’re currently imaging the comet every four hours. How long has that been going on?
Tom: We started looking for the comet mid-September 2010, and since then we’ve been observing it about every four hours first to determine the trajectory relative to the spacecraft and second to determine the light curve to determine if the nucleus is rotating.
Roz: So the DIXI mission is going to observe Hartley 2. How did we select Hartley 2?
Tom: It was determined primarily by how much fuel we had left on the spacecraft.
Roz: So primarily because of the amount of fuel we had left, but is there anything special about Hartley 2?
Tom: Hartley 2 is dramatically different than Tempel 1. Tempel 1 is a rather dormant comet, not terribly active, and it’s very old. Hartley 2 is a very active comet and we expect to see some very different characteristics as we fly by in November.
Roz: This is the third mission for the Deep Impact spacecraft, and we love to call it NASA’s green spacecraft, NASA’s recycled spacecraft. Talk about that.
Tom: The spacecraft is a perfectly functioning asset. All the instruments, all the systems are operating nominally. We don’t have any problems with the spacecraft right now. Of course the fuel is very low. We launched with about 85 kilograms of fuel and have six kilograms left and after the Hartley 2 flyby we expect to be down to four kilograms or less – that’s not an awful lot.
Roz: But still – there are a lot of firsts here – this is very unique.
Tom: That is correct. This is the first spacecraft to visit two comets.
Roz: Despite the fact that NASA has been around for more than 50 years, we still don’t know that much about comets. This is only the fifth comet in history to be viewed close-up.
Tom: That’s correct. This will be the fifth comet, the fourth was Temple 1 and the fifth will be Hartley 2. And one of the special things about this is that we have exactly the same the spacecraft with exactly the same instruments visiting two comets. That allows the scientists to really compare and contrast these two comets in a way that has never been done before. We won’t have a dramatic impact with a huge dust plume coming off Hartley-2 like we did with Tempel 1. But we expect Hartley 2 to be quite different because it’s a much more active comet. If you look at the recent images of Hartley 2 you can clearly see the tail. You can clearly see that the brightness varies as it appears to be rotating and it’s likely we’ll see a much more active comet as we fly by and it will be interesting to see how that differs from Tempel 1.
Roz: And it won’t just be the flyby that’s looking at this event. There will be people on the ground, other telescopes looking at this, right?
Tom: Certainly. If you go on YouTube you can already see videos of Hartley 2 flying against the background of stars and it’s only going to get brighter as November approaches and the flyby approaches.
Roz: This event is coming up shortly. Can you give us a timeline?
Tom: As I’ve said, we’re currently imaging the comet every four hours and sending those images down to the ground for both science and navigation. We’re making sure we’re on the right course to go flying by on the right side of the sun at the right distance. As we get closer we’ll be doing some course corrections. We have two planned right now. The imaging rates will start ramping up in the final hours before the closest approach. At 18 hours out we’re still more than a million kilometers from the comet. And that this point we will go into a continuous point mode where the instruments will stay on the nucleus. Unfortunately we won’t be able to point the high-gain antenna at the ground during this imaging. And all those images, from 18 hours before closest approach to just after closet approach will be stored in memory. And then shortly after closet approach, early on the morning of November 4, 2010, we will then turn the spacecraft, continue imaging the nucleus and then point the high gain at Earth and start downlinking those images.
Roz: The spacecraft has been used for not only the Deep Impact mission, but also the EPOCh mission and now this third mission, DIXI. For the taxpayer – we really designed this for one mission – we get three missions – that’s a lot of bang for the buck!
Tom: Absolutely. The vast majority of mission costs are the initial design, testing and launch. Once you get the spacecraft up there, a relatively small operations crew can maintain a spacecraft like this and continue to do very, very beneficial science. And we’ve demonstrated that with the follow-missions, EPOCH and DIXI.
Roz: What happens to the spacecraft next? Could it be used again?
Tom: Absolutely. We fully expect NASA to release a request for proposals shortly after the Hartley 2 flyby for future extended missions. But remember the fuel is extremely limited. We’ve only got about four kilograms of the original 85 kilograms remaining. We can’t put the spacecraft on a new trajectory. We’re limited to the orbit it’s in right now. But we’re free to observe almost anywhere in the sky.
Roz: When you say low on fuel, does that mean the spacecraft can be up there for three months, four months?
Tom: We think we have sufficient fuel for the spacecraft to last at least another year. But again, we won’t be able to change the course or the orbit of the spacecraft. We’ll just be able to maintain it in this orbit.
Roz: How excited are you about this?
Tom: I’m very excited. I really like sitting in the control room and watching the real-time images come down and knowing that no one has ever seen them before!
Roz: And all of those missions have been very unique.
Tom: It surprises even me, and the rest of the design team, how many different things we’ve been able to do with this spacecraft.
Roz: So, on November 4, where will you be?
Tom: I’ll be with the rest of the team at the Jet Propulsion Laboratory in the mission operations center. We’ll be sitting in a dark room looking at computer terminals to make sure the spacecraft is operating as planned. But we’ll be able to look up once in a while at those big screens as the real-time images come in.
Thank you Tom. Thank you very much, Roz.
End of podcast:
365 Days of Astronomy
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