NEO News (10/23/07) Marco Polo, Dawn, Workshop, Congress, DPS

ESA ANNOUNCES MARCO POLO SELECTION (October 21, 2007)

The European Space Agency has announced the results of its Cosmic Visions 2015-2025 call for proposals. Fifty space science missions for the next decade were proposed, with just seven selected. They range from X-ray and far-infrared observatories to planet finders and a near-earth asteroid sample return mission. These seven, together with the LISA gravitational wave observatory, will go ahead for further study in the next few years, and then two will be chosen for launch in 2015-2017. The asteroid mission, called Marco Polo, is a sample-return mission to a near-Earth object (NEO), Marco Polo would characterize a NEO at multiple scales and return a sample. If approved, the mission would study the origins and evolution of the Solar System, the role of minor bodies in the process, origins and evolution of Earth and of life itself. It would consist of a mother satellite which would carry a lander, sampling devices, reentry capsule as well as instruments. If approved, the mission would be implemented in collaboration with JAXA (perhaps combined with the Hayabusa Mark 2).

The ESA NEA mission Don Quijote, which has been studied for several years as a technology demonstration, is shifting to an orbiter mission called SANCHO, with Spain taking the lead in its development. It might be possible later, however, to restore the small surface package and/or the high-speed impactor originally proposed for Don Quijote through partnerships with other space agencies.

DAWN IS ON THE WAY TO VESTA AND CERES The Dawn spacecraft successfully launched at 7:34 am EDT on September 27, 2007. On October 9, it successfully tested its ion propulsion system. With its solar electric propulsion operating, Dawn is set to travel over the next 8 years to Vesta and Ceres, the two largest maIn belt asteroids,  orbiting each asteroid. Dawn is a NASA Discovery mission, with Chris Russell of UCLA as PI and JPL as managing NASA Center.

Dawn will begin its exploration of asteroid Vesta in 2011 and the dwarf planet Ceres in 2015. These two icons of the asteroid belt have been witness to much of our solar system’s history. By utilizing the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn’s science instrument suite will measure shape, surface topography, tectonic history, elemental and mineral composition, and will seek out water-bearing minerals. In addition, the Dawn spacecraft itself and how it orbits both Vesta and Ceres will be used to measure the celestial bodies’ masses and gravity fields.

Since Vesta and Ceres are not NEAs, we will not be covering this mission in any detail in NEO News. For regular updates, please check the Dawn homepage at (www.nasa.gov/mission_pages/news/dawn)

WORKSHOP AT NASA AMES ON LOW-COST MISSIONS TO NEOS

Summary from David Morrison, 22 October 2007 The past weekend (October 20-21) more than 40 NEO scientists and engineers met for informal discussions of the potential of low cost missions to characterize NEOs. This workshop was part of series of informal weekend workshops hosted by Ames Center Director Pete Worden. The organizers were David Morrison (Senior Scientist, NASA Astrobiology Institute) and Stephanie Langhoff (Ames Chief Scientist), assisted by Organizing Committee members Erik Asphaug, Dan Durda, Bob Farquhar, and Pete Klupar. The workshop agenda was structured to bring together science and engineering communities who have a common interest in small missions but rarely talk to each other.

The workshop agenda blended three major themes: (1) The importance of characterizing small NEOs and the kinds of science measurements that need to be made. (2) How to get to the targets: populations, orbital dynamics, direct vs. gravity-assist trajectories, opportunities for secondary payloads and missions of opportunity. (3) Low-cost missions: spacecraft, instruments, proximity operations, propulsion, landers, and impactors. Fifteen-minute papers covered the above topics, with plenty of time for discussion. The final afternoon was devoted to interactive discussions, organized around three key questions that the workshop participants could explore in smaller breakout sessions, on (1) impactors, (2) rendezvous and orbiter missions, and (3) landers. Sample return was considered outside the possible range for small missions, defined here as those costing under $100M.

The workshop consensus was that small (low cost) missions to NEOs make sense. Since a major objective is to sample the diversity of this population, multiple small missions are cost-effective. At this stage of our knowledge, we can select the most accessible targets, which can be reached with modest launch vehicles, or in many cases as secondary payloads or missions of opportunity. The most powerful general exploration approach is with orbiting or rendezvous spacecraft. Impactors used in cooperation with other missions are potentially able to explore interior structure, and it may also be possible to achieve simple landings within the “small mission” cost cap. In all these cases, a program of NEO missions can be developed using either secondary payload opportunities or Minotaur-class launch vehicles, so long as we select the targets (as opposed to the asteroids selecting us).

CONGRESSIONAL HEARING RESCHEDULED TO NOVEMBER 8

The Congressional hearing on NEO surveys (originally planned for October 11) has been rescheduled for November 8. The hearing before the House Subcommittee on Space and Aeronautics will tentatively include the following witnesses:  Jim Green (NASA HQ), Scott Pace (NASA HQ), Don Yeomans (JPL), Rusty Schweickart (B612), Don Campbell (Cornell/Arecibo), and Tony Tyson (LSST). Further information including opportunities to listen on-line will be found at the Committee website (http://science.house.gov/).

NEOS AT DPS MEETING

The 2007 meeting of the Division for Planetary Science of the American Astronomical Society was held in Orlando October 7-12, with about 800 planetary scientists attending. Asteroids and comets were remarkably prominent at this annual meeting. Not counting the Kuiper Belt, the program lists 171 papers (oral and poster) on comets and asteroids, rather evenly distributed among NEOs, Main Belt Asteroids, and Comets. Also, 10 out of 35 oral sessions were on comets and asteroids. These included two “special sessions” on the first day of the meeting dealing with NEAs: “What’s next with NEO searches” and “YORP Observed!”.

The session on “NEO Searches” was organized by Lindley Johnson (NASA HQ) and Don Yeomans (JPL). The program was:

– Lindley Johnson: The state and future of NASA’s NEO program

• – Robert Jedicke: The Pan-STARRS PS1 survey
• – Steven Chesley: Asteroid impact monitoring: Status and predictions
• – Paul Abell et al.: Piloted Missions to NEOs via the CEV
• – Donald Yeomans: NEO Lessons Learned
• – Steven Larson et al.: Current ground-based surveys for NEOs
• – Edward Wright: Space infrared observations of NEOs
• – Zelljko Ivezic: LSST’s NEO survey capabilities
• – David Morrison: Role of NEO characterization missions

The YORP (the Yarkovsky-O’Keefe-Radzievskii-Paddack) effect is a torque that can modify the rotation rates and axial tilt of small bodies via the combined effects of incident solar radiation pressure and the recoil effect from non-isotropic thermal radiation from the object. This effect can be seen in the alignments of spin vectors for members of asteroid families, and it is emerging as an important effect for spinning up asteroids to create binaries and for the long-terms evolution of asteroid orbits. While the YORP effect has been discussed theoretically for many decades, it had not been observed directly. The first clear detection is from optical monitoring of NEA 2000PH5, which has recently been given the name 54509 YORP. The Japanese Hayabusa mission has also observed this change in spin for the small NEA Itokawa.

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NEO News (now in its thirteenth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, the International Astronomical Union, or any other organization. To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov. For additional information, please see the website http://impact.arc.nasa.gov. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.