Think a billion dollars is a lot of money? It sure is, until you try to go somewhere in space. Then it seems like a pittance. Another sort of relativity, I suppose. In the sort of situation that only government can create, NASA has just announced that it will shortly announce a request for information regarding possible missions to Jupiter's moon Europa. The cost cap? You guessed it - $1 billion.
This puts proposed missions into NASA's mid-level spacecraft program. There are three main levels of mission, known as Discovery, New Frontiers, and Flagship. Discovery-class missions are designed for targeted studies to answer a specific set of science questions. They can usually spend up to about $650 million. Flagship missions, on the other hand, are designed to arrive prepared to study anything and everything they encounter. To do that requires a whole lot of additional equipment and that adds up quickly. Flagship missions generally start around $2 billion and can soar to twice that or more. NASA currently operates three Flagship missions: Cassini, Curiosity, and Voyager.
New Frontiers missions are kind of trapped in the middle. With a budget more than that allotted Discovery missions and far less than a Flagship, these missions are kind of uncertain in scope. An example of a current New Frontiers mission is New Horizons (confusing, I know!), which is currently on its way to Pluto and beyond.
In the inner solar system, money often isn't that big of a concern. Well-known missions like MESSENGER, MAVEN, and the Lunar Reconnaissance Orbiter were all Discovery-class missions. The pair of Mars rovers, Spirit and Opportunity, fit within the cost cap for New Frontiers. This works out because travel time in the inner solar system is short and this keeps mission length (and thus cost) down. The same just can't be said for going beyond Mars.
Let's take Europa, for example. One of the largest moons in the solar system, Europa is believed to have a liquid water ocean hidden beneath its surface. If we want to find life, this is exactly the sort of place we need to go. But simply getting there will take five years. Add another year or two of study at the moon and we're talking about a substantial chunk of a decade here.
Time adds up to money. The most recent concept for a Europa mission is called the Europa Clipper. Over the period of about a year, the Clipper would make a series of 50 or so flybys of Europa to map its surface, search for plumes, and study the environment around and within it. The cost: $2.2 billion. That might seem like a lot (and it is!), but that's less than half the cost proposed for a Flagship-class mission.
To get the mission down below the threshold of a billion dollars, significant reductions in the spacecraft's capabilities will be required. It'll have to carry fewer instruments, make fewer flybys, and collect less data. That's a shame.
A general rule of thumb in outer planets research is that you get to go to a given place about once a generation, if you're lucky. The Voyagers flew by Jupiter in the late 1970s and Saturn in the early 1980s. Our next mission to Jupiter, Galileo, didn't arrive until the end of 1995. Cassini didn't make it to Saturn until nearly a decade after that. We last visited Neptune in 1989 and there aren't even plans to go back.
This means that when we go to Europa, we've got to do it right. A second chance could be decades in coming. Hopefully NASA can make this happen.