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For those listening to archives using live365.com and rating the programs, please email me as to why you assign a specific rating to the show. This will help me bring better programming to the audience. We welcomed Brent Sherwood back to the show to discuss NASA planetary science missions and in particular the Discovery class missions. During our nearly two hour discussion without a break, Brent started out by telling us how NASA selects Discovery class missions. He talked about the two kinds of science but focused on the Discovery missions which have a $500 million budget not including launch or operating costs. He said it was open season on the solar system other than the sun or Earth as they were covered by other NASA programs. In speaking about the history of Discovery missions, he named a few that we are all familiar with such as Kepler, Grail, Deep Impact, Stardust, the Phoenix Mission, Dawn and the upcoming Insight Mission to Mars. Brent then explained the proposed missions under the auspices of his team. These proposed missions include VERITAS, BASiX, CORE, Pandora, Proteus, Psyche, Kuiper, and ELF. Brent explained each proposed mission to us, talked about the P.I. for each mission, and the science to be gained from the mission. Listeners had many questions for him including how the principal investigator (PI) was selected. Brent explained the process, where the PIs come from, how a mission is proposed, is it coming from a university or academic setting, has it been proposed before, or is it coming from JPL or another NASA center or the Applied Physics Lab (APL). Brent was clear that Discovery missions, given their limited resources, were not about developing and proving out new technology so in answer to my question about the TRL of completing these missions, he said they were all coming in with very high TRLs though the missions sound very futuristic, even bordering on science fiction. As for timelines, Discovery missions approved now would fly in 2021 so they have about a six year time frame to be developed and flown. In response to questions, our guest addressed this six year time line in some detail. All of these missions sounded very exciting but as Brent said, it is a very competitive process and only one or two if any of them may be selected as other teams are proposing their Discovery projects as well and they are equally exciting. Later in the segment, Brent was asked about the choice of launch vehicle for each project. This was a very interesting discussion, don't miss it as our guest explained in detail the role of the PI regarding the launch vehicle and how NASA actually selects a rocket for the mission. In response to BJohn's question about launch costs, they certainly factor into the mission planning. Doug asked a question about the Photos-Deimos mission and if the mission could identify a favorable small crater which could later be the site for a covered habitat and if it could identify frozen volatiles in the polar craters of those moons if they exist. Brent said it might have such capabilities but that these missions only do the work specific to their actual project. He had more to say on this so don't miss all his comments. BJohn asked why not a Uranus mission. Brent said Uranus was too far out and too costly for a Discovery class project. Near the end of the segment, BJohn also asked about the importance of miniaturization now and for the future with NASA and these missions. Brent said it was very important and then updated us on all the cubesat opportunities and uses being integrated into NASA missions. He spoke about the significance of cubesats for several minutes so don't miss what he had to say about them. Doug asked a question about realizing economic value from these missions or at least what was the rationalization behind these purely science missions. Brent provided an excellent answer to Doug's questions so don't miss it. We ended the show after Brent's response. See what you think of it and post your comments on TSS blog. Doug sent in a final note saying "I agree with his answer re: the value of science. I believe that it is worth a certain amount of our money to increase our knowledge for its own value." Please post your comments/questions on The Space Show blog above. You can reach Brent Sherwood through me at drspace@thespaceshow.com.