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The Planetary Society BlogBy Emily LakdawallaA launch to Neptune in 2019?Nov. 7, 2008 | 13:01 PST | 21:01 UTC
The Outer Planets Assessment Group, or OPAG, is meeting this week at Arizona State University, primarily to examine the progress of the two major Outer Planets flagship mission studies, one of which will be selected by NASA and ESA in January. The two missions that are being considered are a Europa Jupiter System Mission or EJSM and a Titan Saturn System Mission or TSSM. Not long after the meeting is over, the presentations on these proposals should be posted to the OPAG website, so if you're curious about them, go check those presentations out.
The next flagship mission to an outer planet will either be going to Jupiter or Saturn. That'll be active in the mid 2020s. There is some desire for the next flagship mission after that to go to the Neptune system. But, for a variety of reasons, it's not going to happen anytime soon -- not until the 2040s at least -- and there's no telling whether a compelling case will be made for the next flagship to go to the planet, Jupiter or Saturn, that didn't get a mission in the 2020s. So it could be a long, long, long time before we visit Neptune (nevermind Uranus).
What to do? Candy Hansen and Heidi Hammel are proposing a mission called Argo that could update our understanding of the Neptune mission at the much lower cost of a New Frontiers mission. But at that price, it would not be an orbiter; it would be a flyby mission. Would it really be worth sending just a flyby mission to Neptune? If a Neptune flyby was all that we would get out of a New Frontiers mission, the answer would probably be no. But Argo proposes to study Neptune and Triton in a flyby, then go on to a couple of Kuiper belt objects, just as New Horizons is going first to Pluto, then to a couple of Kuiper belt objects. In fact, to keep costs in line, Argo's design would borrow a lot from New Horizons.
Argo, on the other hand, would be flying by Neptune, which is the third-most-massive planet in the solar system. Flying by Neptune opens up a huge cone of opportunity; with a gravity assist from Neptune, Argo could choose a course into the Kuiper belt that lies anywhere within 60 degrees of its Neptune trajectory -- a total breadth of 120 degrees -- and that's without using any propulsive assistance at all. The Argo mission could choose to visit any one of nine large (400 kilometers in diameter or larger) Kuiper belt objects, some of which are binary (two for the price of one -- like Pluto and Charon), or any one of 40 objects between 200 and 400 kilometers in diameter. I assume that, if the mission were to be selected, they'd eventually settle on a course that could take it past two or more objects of diverse types, trading among all the variables of interest to the science team -- size, surface properties, number of companions, and so on.
It's a neat idea. It can't happen in the next New Frontiers opportunity because the U.S. doesn't have enough plutonium available for the next New Frontiers to be nuclear-powered. So it has to be New Frontiers 4, which implies a launch date in 2019 or 2020, with the Neptune flyby happening around 2027. Just to be clear, Argo hasn't been selected for New Frontiers 4; the announcement of opportunity for New Frontiers 4 won't happen until 2013, and then Argo will have to compete against all the other no doubt compelling proposals. It's not a done deal, just a neat idea. There was a funny moment in the presentation, when Hansen put up a grid identifying the positions on the science team that will eventually need to be filled. With the spacecraft not launching for a decade, and not reaching its first real science target for two decades, now might not be the best time to identify the science team. "It's not going to be any of us," joked someone from the audience. It's true; there will certainly be some people on that team who are now established researchers, but the majority would likely be people who are currently in graduate school or college. Maybe even high school. Are you in high school right now? Want to drive a spacecraft to Neptune? Argo might just be your chance.
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CommentsBallute lander
Flying so close to Triton presents the opportunity for a high-speed ballute-deccelerated lander mission. That should be investigated as part of ARGO too - a potential close up look at Triton, at least getting a closer look at its atmosphere and heat-flow, with geophysical data return if the lander lasts long enough to detect seismic activity.
#1 - Adam Crowl - 02/06/2010 - 16:12
Orbiter Preferred
I believe the Argo Neptune Mission would be a neater idea and more worthwhile IF it is made to do orbiting about Neptune & Triton akin to the Cassini spacecraft at Saturn. Consider a flyby to give good scientific data for most of a day, while an orbiter can return data once there for YEARS - a long enough time to reveal potential changes in Neptune's atmosphere (blue storms) and on Triton's geyser laced surface. Also, detailed maps of Proteus, Nereid, and other small moons could be made, with details of the planets rings. Truly, the orbiter is the way to go - hands down. Hope to live long enough to see some of the results!
#2 - Jay Brausch - 02/11/2010 - 23:21
Well, of course an orbiter is preferred! But that'd cost in the neighborhood of five billion bucks, which we don't have, and which is not going to magically appear. The beauty of Argo is that it can be done for about 700 million, within an existing program, the New Frontiers program. Argo is not blue-sky engineering; it is a real possibility. A Neptune Orbiter is not in the cards at present.
#3 - Emily Lakdawalla - 02/12/2010 - 13:52
Much Better Card
A 5-billion dollar orbiter to Neptune makes going there alone worth 2 bucks a mile; exploring, mapping, and studying Triton (a likely captured and geologically active Kuiper Belt Object) as such over years would be well worth it, not to mention doing the same with Neptune's other moons. A flyby would be too brief after going all that way, as New Horizons surely will be for much smaller Pluto in July, 2015. Also, so much more WOULD be learned from Neptune's atmosphere, rings, and internal heat source via an orbiter rather than mere flyby, which wouldn't be worth $700 million. After all, Voyager 2 already did that in Aug. 1989, which you would think we would like to much build upon, after 40 yrs then (2029). A subsequent mere flyby of another KBO beyond Neptune would be analogous to a flyby of Saturn's Hyperion or other small dead moon. Not worth the extra years in empty space! Logic speaks loudly for prioritizing the Neptune-Triton (etc.) Orbiter - hands down. Pass the words on.
#4 - Jay Brausch - 03/03/2010 - 23:52
Compareable Big Bucks
When considering another neat mission to the outer solar system, it should be a decision to prioritize either a flyby mission, orbiter mission, or (wishful thinking!) BOTH. Neptune and its system are too significant for a too-brief flyby mission - which was done already by Voyager 2. So, 5-6 billion bucks for an orbiter would be a much better quality scientific investment. And not so bad also, when the money is spread out over a decade. Compare this cost to that of the debatable Iraq War and Afghanistan quagmire. And can either of us forget so soon the $700 billion bailout of the Wall Street weasels? At, least with such a wonderful mission, the public would have transparency as to how and where the money would go.
#5 - Jay Brausch - 03/06/2010 - 21:47
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