Asteroid dreams, Part 6: Target NEO


On February 21, 2011, an open global community workshop on near-Earth objects (NEOs) took place in Washington, D.C. Now known as the Target NEO I workshop, it was convened “to bring together experts for a technical discussion of the key issues surrounding human exploration of near-Earth objects (NEOs).” The workshop attracted 200 participants.

This summer, on July 9, a “Target NEO II” workshop will convene at the National Academy of Sciences to take up the topic again. (A draft agenda is now available.) Given this upcoming event, I’m offering a brief summary of the findings (recommendations?) of Target NEO I, as detailed in the final report on that event.

The “key question” posed to drive Target NEO I discussion was this: “What information about NEOs is still needed to support a robust, sustainable human exploration program?”

A session on “NEO population knowns and unknowns” yielded these “key findings,” among others:

* “A more complete catalog of NEOs will expand the available NEO target catalog and help inform a robust and sustainable human exploration program. A space-based NEO search can provide such an expanded catalog far in advance of when it could be obtained by existing or planned ground-based surveys. Focused efforts with dedicated space-based assets could greatly reduce unknowns about the NEO population within 10 years.”

* “The sizes of known NEOs are, in the vast majority of cases, individually uncertain by about a factor of 2. This is a dominant contributor to the uncertainty in the estimated number of NEOs at a given size…. Small NEOs < 150 m in size are usually fast rotators, potentially making them inappropriate targets for human missions.”

* “The heliocentric orbits of many known NEOs are so uncertain that they are effectively lost (including most known objects under 100 m in size), meaning that they will need to be independently re-discovered in order to refine their orbits. Follow-up observations are needed after NEO discoveries to ensure sufficiently accurate orbit determination in support of human and robotic mission planning.”

“Findings” from a session on mission design (reading more like recommendations) include, for example:

* “Survey NEOs, particularly those with Earth-like orbits, from a deep space vantage to find the most appropriate HSF mission opportunities sufficiently in advance of their Earth departure seasons.”

* “Target initial HSF missions at the most accessible NEOs using conventional technology to the greatest extent possible.”

Among findings from a session on NEO characteristics “for safe and meaningful human exploration” were these:

* “Engineering, dynamical, and human factor constraints will limit the pool of viable NEOs for exploration by human crews. The size-frequency distribution of NEOs is such that as smaller object sizes are considered, the number of expected objects increases exponentially. However, smaller sizes are also much more likely to have rotation rates too fast to allow safe interaction. From a scientific point of view, in-depth exploration of any asteroid will represent a major leap in our understanding, and we are not likely to have a large enough pool of well-characterized targets to use science preferences as a discriminator between objects. Therefore, we expect non-scientific factors, such as crew safety and accessibility, to be the major criteria for target selection.”

* “Robotic precursor missions are required for detailed in situ physical characterization of candidate human spaceflight targets to reduce operational and budgetary risk.”

*( “Characterization of candidate NEO targets should include information applicable for human exploration needs, including rotation period and pole direction, size, shape, presence of satellites, composition, and internal structure. In addition, an understanding of regolith properties and dynamics will be critical.”

Among insights from a session entitled “mission duration: quantifying the risks” were that:

* “The lack of abort options [for human NEO missions] will require sufficient onboard medical capabilities and careful management of logistics and consumables.”

* “Deep space missions do not afford the abort opportunities and psychological comfort provided by rapid return to Earth that is a hallmark of missions in cislunar space.”

* “Public understanding and acceptance of mission risk, along with the risk/benefit relationship, [is] an important consideration in establishing sustained human presence beyond LEO.”

*  “The duration of the mission is the primary factor in risk management, and…the cumulative experience and knowledge base for human space missions beyond 6 months is severely limited.”

A session on “affordable options for increasing the accessible NEO catalog” concluded that:

* “Dedicated, affordable, highly capable survey concepts exist at varying degrees of maturity.”

* “Each of these concepts would dramatically increase the number of suitable NEO targets for future human exploration by at least on order of magnitude.”

* Cost estimates attached to many of these concepts “(i.e., the space-based solutions) fall within the current Discovery mission-class cost range.”

Following the Target NEO I workshop, a “Workshop on Future Small Bodies Missions: Discussing the Synergies Between Science, Planetary Defense, Exploration, and Commercial Interests” took place May 13, 2011, in Bucharest, Romania, in conjunction with the 2011 International Academy of Astronautics (IAA) Planetary Defense Conference. The purpose of this workshop was to discuss international coordination of NEO-related activities. Among the findings of this workshop were the following:

* “There is a clear overlap between scientific missions, missions to develop mitigation techniques, and exploration missions. The many synergies between these types of missions should be exploited.”

* “Only 1 ± 1 potential targets for HSF have been identified to date.”

* “The participants of the workshop encourage an effort to introduce a mitigation demonstration mission to the upcoming 2012 ESA Council Meeting at the Ministerial level.”

For more information on Target NEO I, see Johns Hopkins Applied Physics Laboratory NEO expert Cheryl Reed’s presentation to the “human community workshop on the Global Exploration Roadmap, November 14, 2011,” entitled “Target NEO: Forums Vested in Providing a Resilient NEO Accessibility Program for Human Exploration Beyond LEO.”

One topic that’s missing on the agendas of the two 2011 workshops and the draft agenda for the 2013 workshop – and in public discourse about NASA’s Asteroid Initiative – is the social costs and benefits – the ethics, as it were – of extending human presence beyond Earth orbit into deep space. I’ll hope that soon this topic will receive some serious consideration among humans-to-asteroids advocates. It’s all too common for human space flight programs to leave social and ethical considerations for others to address. These considerations need to be an integral part of mission planning.

Stay tuned to this site for a report on the proceedings of Target NEO II next month.


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