Two designs for outer planet exploration probes are currently under consideration by ESA and NASA, with the aim of following up the highly successful missions of Galileo and Cassini/Huygens.

They are the Europa Jupiter System Mission (aka Laplace) and the Titan Saturn System Mission (aka Tandem). But despite their obvious similarities, only one will be approved, according to BBC news.

The winner is to be announced this month (February). But the BBC reporter, Jonathan Amos, cautions: "The mission [...] may never fly if the agencies decide there are other space missions in their future portfolios that they consider to be a higher research priority." Meanwhile, at the IAC in Glasgow, ESA science chief David Southwood described the competing mission plans as being engaged in a "fight to the death" (Spaceflight, Dec. 2008, p.461).

Surely this is another case of spending money first, exploring the planets last?

Surely the first criterion that any credible outer planets design should satisfy is that the same basic system must be versatile enough to support missions to all four giant planets, as well as to other targets in the outer Solar System? Otherwise follow-on missions will require expensive redevelopment, greatly reducing the value for public money they represent.

As with Mars, the list of interesting targets is a long one. For a start, we should place orbiters around all four giant planets and their six major satellites, plus Titania, plus Pluto, and in addition send probes to rendezvous with both groups of Jupiter trojan asteroids, adding up to a total of 14 initial missions. Smaller moons such as Enceladus, Iapetus and Miranda would also repay closer study, not to mention Kuiper Belt Objects beyond Pluto. And we need to add in atmospheric probes for the giants and landers for the major moons before this phase of the reconnaissance is complete.

At the current rate of one outer planets probe per decade (Galileo in the 1990s, Cassini in the 2000s, Juno for the 2010s, Laplace or Tandem for the 2020s), these worlds would take a couple of centuries to explore with just one dedicated probe each.

But does exploration of our Solar System have to proceed at such a snail's pace?

Suppose that probes were launched more frequently, say one every two years? We could envisage an international consortium building the probes to a standard design on a continuous production line and selling them to NASA, ESA, Roskosmos and other agencies as required. Such commonality of design would keep the cost per probe low. By avoiding the temptation to optimise each spacecraft for each mission, the amount of science done per mission is reduced, but the amount of science done per dollar or euro -- and especially per year -- is surely greatly increased (though it would be nice to have further analysis to quantify this tradeoff).

The amazing thing is that NASA seems to have arrived at a concept similar to this (though not internationalised) in its 1983 Mariner Mark II programme.

According to Wikipedia, the intention was to have a series of space probes to follow up the very successful Mariner series. They were specifically for the outer Solar System, therefore technologically compatible. The first two missions planned in the series were Cassini and CRAF (Comet Rendezvous - Asteroid Flyby). The costs were supposed to be kept down to $400 million through commonality. Presumably missions to the other outer planets would have followed, instead of today's irrational strategy of playing off expensive one-off Jupiter probes against expensive one-off Saturn probes.

Then Congress cut the funding, and CRAF was sacrificed. In order to save Cassini, it was (according to Wikipedia, which is not always accurate) significantly redesigned in order to reduce total programme cost. As a result Cassini was slimmed down from a $400 million mission to ... a $3.4 Billion one !!! (total programme cost given by Astronautix.com).

In other words, it's the same story as with the Mars rovers: costs rocketing up out of control, exploration going ahead at a crawl, if at all. Clearly the story of Mariner Mark II's transmogrification into Cassini sets the scene for today's planetary exploration landscape.

One can only wonder in amazement whether these programmes are managed by the same people who flew men to the Moon in the 1960s!

Mariner Mark II was replaced (says Wikipedia) with the Discovery programme, and an article in the Dec. 2008 Spaceflight magazine (p.467) puts the cost of Discovery missions at $400 million (i.e. lower cost than the same figure in 1980s dollars). Current Discovery probes are Dawn (to Ceres and Vesta) and Grail (lunar gravity probe, launch in 2011).

Please visit Stephen Ashworth website too: http://www.astronist.demon.co.uk