Astrobiology: Do you believe the introduction of air-based probes will supersede the traditional slower land probes and rovers, considering that there are (or were) plans to send an aircraft or balloon to Mars?
Dr. Lorenz: I think they are a supplement, rather than a replacement, for landers and rovers. Of course, that distinction isn't meaningful for the outer solar system, where we have one mission a decade, roughly.
"It is important that all safety measures are rigorously followed."
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Astrobiology: There was a notable amount of opposition to the presence of an RTG on Cassini - you propose to use one on your helicopter. How would you respond to claims that RTGs are potentially very hazardous?
Dr. Lorenz: The Cassini RTG issue raised a lot of discussion, little of it rational. I believe they are quite safe. That said, it is important that all safety measures are rigorously followed, and the public scrutiny of the issue helps in that regard. What little hazard there is can be reduced somewhat by using more efficient converters, and hence less radioactive material, which is what I advocate.
Astrobiology: How would the helicopter communicate with Earth?
Dr. Lorenz: It would need a large (>1m) dish to communicate directly with Earth, and that might be difficult to accommodate on a helicopter. Maybe it could have a deployable dish that it uses only on the ground. But a better idea might be to use a relay satellite in orbit around Titan
Astrobiology: Since there is a significant communications lag-time with Earth, would the helicopter be at least semi-autonomous and capable of making snap judgements or even conducting its own exploration?
Dr. Lorenz: Certainly it would handle low-level tasks like hazard avoidance, landing, etc. It could prioritize data for downlink (images with little contrast can be rejected, for example). But scientific interpretation should be in the hands of people.
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"Titan's landscape is the largest unmapped single area in the solar system."
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Astrobiology: What is the attraction of Titan to scientists, compared to the other moons of Saturn?
Dr. Lorenz: Titan is unique in two large respects - its dense nitrogen atmosphere (the only other significant nitrogen atmosphere in the solar system is the Earth's), and the organic chemistry that takes place there.
It is likely Titan's landscape is one of the solar system's most interesting, with river and shoreline processes shaping it. Titan represents the largest unmapped (at 1km resolution) single area in the solar system.
Astrobiology: What are the main advantages - and disadvantages - of a helicopter compared to a rover or probe?
Dr. Lorenz: The main advantage is mobility. The main disadvantage is complexity.
Astrobiology: Since a helicopter is arguably an order of magnitude more complex than rovers or simple probes, is it reasonable to expect that it will have a greater chance of failing?
Dr. Lorenz: Than a simple probe, perhaps. That's an issue of risk vs. return. After ESA's Huygens probe, the incremental value of a single probe is modest, unless it lands at a remarkable spot.
Than a rover, I don't think the risks are much greater. We don't know enough about the surface to design a rover that won't get stuck
Astrobiology: If NASA approves the concept, when might the helicopter be launched and reach Titan?
Dr. Lorenz: Probably not until the end of the decade
Astrobiology: How is CMU's autonomous helicopter different from the one you are proposing?
Dr. Lorenz: My idea is science-driven - there are a set of important things to do, and it appears a helicopter is the best way to do them. The CMU helicopter is a technology exercise, for which they have found one small scientific application. The technologies they develop will be important for Titan exploration, but it's not really comparable.
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