This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

19 November 2007

Interesting Asteroid/Comet Abstracts from Seventh IAA International Conference on Low-Cost Planetary Missions

Here are some interesting abstracts from the recent Seventh IAA International Conference on Low-Cost Planetary Missions (12-14 September, 2007, Pasadena, California USA).

- An Approach To Minimum Cost NEO Characterization. R. Reinert , R. Dissly, and Scott Mitchell, Ball Aerospace & Technologies Corp.
Link: Abstract

This abstract details a few mission concepts including (from the abstract):

- NEO Scout Low-Cost Spacecraft Concept. The NEO Scout mission concept is designed to minimize mission cost by using a very low-cost spacecraft. The NEO Scout approach uses a basic single-string architecture and a simple hydrazine monopropellant propulsion approach to rendezvous with a single NEO after a launch to a C3 of 5-10 by a Taurus, Falcon-5, or Minotaur-V medium-cost LV.

- NEO Sentry Minimum Launch Cost Mission Concept. The NEO Sentry mission is aimed at minimizing mission cost by using the lowest cost launch vehicle. It uses a high performance dual-mode bipropellant propulsion approach and ultra-low mass to rendezvous with a single NEO after launch to a 185-km LEO by a bargain-basement Falcon-1 LV.

- NEO Explorer (NEOX) Solar Electric Propelled Spacecraft Concept. The NEOX mission concept minimizes mission cost by enabling a single spacecraft to rendezvous with multiple NEO’s and by allowing multiple S/C to be launched by a single LV. The NEOX mission profile takes advantage of the low-thrust mission designs described below to rendezvous with up to three separate NEO's, or to perform a single rendezvous with a NEO inaccessible to chemically propelled vehicles. SEP efficiency lowers the NEOX S/C mass sufficiently to allow 2 such S/C to be launched on a single Delta-II, or four to be launched on the smallest Delta

- Deep Interior: Radar Exploration of Asteroid Interiors. A. Safaeinili (1), E. Asphaug (2), Y. Gim (1), E. Heggy (2), 1.Jet Propulsion Laboratory, 2. UC Santa Cruz, 3. Lunar and Planetary Institute
Link: Abstract

From the abstract...

Our nominal mission design for a radar investigation at a typical km-sized asteroid utilizes a polar orbit, with a period of weeks, while the asteroid spins underneath with a period of hours. The result is to "peel the apple" with thousands of unique radar returns providing global coverage at the spatial requirements of tomographic reconstruction. Another alternative, appealing at small (sub-km) asteroids where orbiting can be a challenge (solar wind pressure becomes comparable to the asteroid gravity), or at binary asteroid systems, is to utilize a hovering mission approach (as was done by the Japanese Hayabusa mission) while, as before, the asteroid spins underneath. Optical imaging is sufficient for the a posteriori reconstruction of spacecraft position at the time of data acquisition, so the only instruments required for this mission is the radar hardware, the antenna, and a simple camera. At present, this mission fits inside of the Discovery cost parameters even if one flies to two or more asteroids. With further radar flight heritage, this radar reflection imaging technology can evolve into a very low cost mission that could be flown routinely to near-Earth objects and other small bodies.

- Triple F: A comet nucleus sample return mission for ESA’s Cosmic Vision program. M. KÜPPERS1, H. U. KELLER1, E. KÜHRT2, P. EHRENFREUND3 AND THE TRIPLE F TEAM, 1 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany, 2 Institut für Planetenforschung, DLR, Germany, 3 Leiden Institute of Chemistry, Leiden, The Netherlands
Link: Abstract

From the abstract...

A relatively small spacecraft will be launched into its interplanetary trajectory to a short period comet. After a short monitoring period near the cometary nucleus, needed to find suitable sampling spots, the spacecraft will touch down on the surface of the nucleus to collect samples. The sampling depth will be several decimeters. Finally the cooled samples will be returned to Earth. The mission is proposed to ESA’s Cosmic Vision and exploration programs, in co-operation with the Russian space agency.

- Hayabusa-2, The Next Asteroid Sample Return Mission of Japan. Makoto Yoshikawa, Hajime Yano, Junichiro Kawaguchi, Post-Hayabusa Mission WG, Japan Aerospace Exploration Agency.
Link: Abstract

From the abstract...

We have been considering post Hayabusa missions much before Hayabusa's arrival to the asteroid. This is because we think that asteroid is the key object to understand the origin and evolution of the solar system. Since the results of Hayabusa were very impressive and important from the point of the planetary science, we are now attempting to start next mission as soon as possible. We call the next mission as Hayabusa-2. The spacecraft is basically the same as Hayabusa. Of course we modify several points where there were problems. But the model is almost same, so we can save time to manufacture it, and we are hoping that we can launch it in 2011 or 2012. The target is again small near earth asteroid but C-type. So we are looking forward to seeing how the small C-type asteroid looks like. The current target of Hayabusa-2 is 1999 JU3.

Also, we are considering another sample return mission, which we call "Hayabusa-Mark2" tentatively. Hayabusa-Mark2 is not the copy of Hayabusa, but it is much-advanced mission both in the sampling and the remote sensing. For example, we want to challenge sampling with preserving depth profile and to get much more detailed data of the sampling sight. Hayabusa-Mark2 is also considered in the scheme of Cosmic Vision of ESA.

- Stand-off Estimation of Binary Asteroid Mass Distributions. D.J. Scheeres1,2 and E.G. Fahnestock1, 1The University of Michigan, Ann Arbor.
Link: Abstract

From the abstract...

Recent investigations of the dynamics and morphology of the binary asteroid system 1999 KW4 have revealed a complex and dynamic system that should be typical of binary asteroids. While investigation of the KW4 system is of intrinsic interest, methods we have developed to understand and characterize this system are also applicable to other NEA binaries with similar morphology. In this presentation we will detail an underlying dynamical theory we have developed and an accompanying procedure which allows one to estimate the mass distribution properties of a binary system without having to fly a spacecraft within the gravitational field of the system. Specifically, we show that in a system such as KW4 there is sufficient information in the dynamical oscillation of its components to estimate the second degree and order gravity field coefficients and moments of inertia of both bodies based on stand-off observations alone. This is significant when compared to the situation for solitary asteroids where the gravity field can only be determined by tracking the motion of a spacecraft perturbed by the higher order gravity coefficients. Also, the moments of inertia cannot be estimated for solitary asteroids, except if the body is in non-uniform rotation. For a binary system with an excitation level similar to KW4’s, it is possible to determine the total mass, mass fraction of the system, the J2 gravity coefficient of the primary, the principal moments of inertia of the secondary, and potentially the principal moments of inertia of the primary if it has a significant equatorial ellipticity. The moments of inertia contain significant information on how the mass is distributed within a body not available from the gravity coefficients alone. The placement of passive probes on the surface of the binary components with radio transmitters can yield significantly improved precision for these estimated quantities. The estimation of these quantities do not require the spacecraft to orbit the system closely, which can reduce a mission’s operational costs significantly.

Link: 7th Low-Cost Planetary Missions Conference Website

Link: 7th Low-Cost Planetary Missions Conference Website: Agenda

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