Guest: Dr. Marc Rayman. Topics: The Dawn Mission spacecraft, Ceres news & updates, plus much more. Please direct all comments and questions regarding Space Show programs/guest(s) to the Space Show blog, http://thespaceshow.wordpress.com. Comments and questions should be relevant to the specific Space Show program. Written Transcripts of Space Show programs are a violation of our copyright and are not permitted without prior written consent, even if for your own use. We do not permit the commercial use of Space Show programs or any part thereof, nor do we permit editing, YouTube clips, or clips placed on other private channels & websites. Space Show programs can be quoted, but the quote must be cited or referenced using the proper citation format. Contact The Space Show for further information. In addition, please remember that your Amazon purchases can help support The Space Show/OGLF. See www.onegiantleapfoundation.org/amazon.htm. 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 back Dr. Marc Rayman to the show to discuss the Dawn Mission and Ceres updates. During the first segment of our 1 hour 25 minute discussion, Dr. Rayman said that Dawn was as close to Ceres as it would ever be & that it was in a stable orbit that would last a very long time as they need to avoid having the spacecraft crash into the surface of Ceres. Dawn is approximately 240 miles above Ceres and its orbital velocity to maintain this orbit is around 600 mph. It takes about 30 minutes for a radio signal to travel one way between Ceres and Earth for a one hour round trip time. He discussed this Ceres stable orbit in some detail. We talked about the mission end for Dawn which will likely happen sometime in 2016 as the thruster hydrazine fuel runs out. He described the failure to us and why they cannot predict with certainty the end date an time. Marc also talked about the reaction wheels (gyros), the fact they lost two but had one spare to use. He explained how they have been operating the spacecraft with just two gyros instead of the required three. We talked about some of the new information coming back, exciting findings by Dawn and of course the mysterious bright spots. Marc commented about the mountain Ahuna Mans which rises to about 20,000 feet above the surface. Doug called to ask about the water ice and the dark cracks he saw in the photos of the bright spots. He also inquired about a human mission to Ceres. Listeners brought up private human missions, including the possibility of a private human mission to Mars. Don't miss what Dr. Rayman said about these potential missions. In response to a question about what would humans do on Ceres, our guest said EXPLORE! BJohn wanted to know if Vesta and Ceres had a special alignment making the mission possible or if we could pretty much visit any two asteroids as we did with these two (dwarf planets). Doug emailed in asking how the astronauts would actually get around on the surface of Ceres, a question which led to discussing Ceres gravity. In the second segment, I asked Marc how he and the others associated with these very long term planetary missions develop the patience to wait years and years for the spacecraft to arrive at the destination and start doing what it was designed to do. Marc had some interesting comments and observations about this. Jerry asked if nuclear propulsion would benefit missions such as Dawn and planetary science in general. Helen wanted to know what was the most disappointing thing about Dawn. The reaction wheel failure was a big item but Marc had interesting things to say about defining something related to a mission as a disappointment. Another listener asked if JPL tracked the general population popularity of its planetary missions. Later in the segment we discussed robots vs. humans for some missions, then Jane asked about public school text books containing this cutting edge planetary science information. Both Marc and I offered comments on this subject. Marc also suggested we visit www.spaceplace.nasa.gov. Another listener asked for the best school study path to pursue to be able to do what Marc does today at JPL. Marc had lots of interesting things to say about this so if you want to do planetary science, note what he said. There are multiple study paths to take that can lead you to this kind of work at JPL & other centers/institutions. He also noted that JPL has lots of non-technical people doing key things in the planetary science department with missions so the path is not always science and engineering. Paul offered up the last question inquiring about the volume of data to be studied from Dawn. Marc directed our attention the JPL Planetary Data System Repository which is where this information ends up and anyone can access and research it. There are years if not decades of research awaiting for the Dawn Mission data. Please post your comments/questions on TSS blog above. You can reach Dr. Rayman through JPL or me.