Wednesday, October 10, 2012

Too Exciting to Die? And Good Reads

Probably a couple dozen times a year or so, I come across a talk or a paper proposing a new planetary mission concept.  If the idea is truly novel, or just really intrigues me, I’ll write about it in this blog.  Usually, these ideas die as nothing more than paperware, victims of the winnowing of the many, many ideas proposed and the very few planetary missions that actually fly.

Recently, though, one concept mission received coverage in a number of blogs and news outlets.  Interestingly, the mission is new only in proposing a twist on a mission that has been proposed and considered seriously several times before.

I’m talking about the TALISE Titan lake and shore probe presented atthe recent European Planetary Science Congress.  At the time of the presentation, the concept remained in the early conceptual phase where many basic tradeoffs such as the instrument compliment remain to be decided.  What was novel about this proposal was the idea of attaching paddles, wheels, or screws to the lander so that after a period floating on a Titan lake, the probe could haul itself onto “dry” land to measure a different surface.

Titan lake missions have been proposed several times.  The first was a short-lived, battery powered probe that would be one element (along with a Flagship orbiter and a long-lived Titan balloon) in the Titan Saturn System Mission.  Unfortunately, the technology to carry out the overall mission required considerable technology development and the price tag of several billion dollars proved too dear.  The second set of proposals were conducted for the Decadal Survey and included short and long-lived lake landers and versions that would dive to the lake bottoms as submersibles.  The price tags for these concepts were a bit north of one billion dollars, and the Decadal Survey committee determined that the science to be returned was too low for the cost.  The third proposal was the TiME proposal for the recent Discovery mission competition that lost out to the InSight Mars geophysical station.  We don’t know why TiME wasn’t selected – costs too high for the Discovery budget cap or a technical issue or something else.

The attention given to the TALISE concept, which is in the very early assessment stage, shows how the idea of a mission to float on the lakes of the only other world in the solar system with liquid seas captures the public imagination.  I’m not immune to this call.  I’m in my mid-fifties, and if a mission to follow on to the discoveries of the Cassini mission is to fly in my lifetime, it will be based on concepts developed in the next few years.  A return to Titan and Enceladus rank very high in the short list of missions I really want to see flown. 

Whether it is TALISE or another concept, I suspect that the challenge will be less technical than fiscal.  Landing on Titan and orbiting Saturn to provide the data relay is not hard technically, as several studies have shown.  However, Cassini has proven so successful that it has raised the bar on what a follow on mission must do to be scientifically competitive.  I suspect that the cost of such a mission is at least a billion dollars and may be closer to two billion.  (TiME would have taken advantage of an alignment of Titan’s northern lakes and Earth to not need a relay spacecraft.  With the onset of winter in Titan’s north, that alignment won’t be available again for decades and now missions will need a relay craft.)  I believe that the challenge for Titan mission proposers will be to find the funding and that the engineering challenges will be comparatively straightforward.


Future exoplanetmissions: NASA and the world (part 1) - Phil has written several times for this blog and continues his excellent work on The Space Review

The telescopes thatcame in from the cold - NASA considers how to make use of the gift of the core hardware for two Hubble-class telescopes

Reality TrumpsPolitics On Space Policy Debate - This article discusses how little attention NASA and its issues has gained in the Presidential election.  (And I am so glad that I don't live in one of the nine states where the Presidential election is up for grabs -- the advertising volume is reportedly insane.)