Close pass by XP14: On July 3, 2006, our planet will receive a close visit by Near Earth Asteroid (NEA) 2004 XP14, which will pass by at 1.1 times the distance to the Moon (a little more than 400,000 km). This NEA was discovered in 2004 but was only recovered last week. There is no risk of its hitting either the Earth or the Moon, but it is unusually well placed for study, especially by radar. The asteroid will swing past us at a relative speed of 17 km/s.
While XP14 will not be visible to the unaided eye, its relatively large size (estimated at roughly half a kilometer) combined with its closeness makes it one of the best-placed targets for study in the history of planetary radar. Extensive observations are planned with the NASA 70-m radar at Goldstone, California, which is part of the NASA Deep Space communications network. It is anticipated that these radar studies will yield detailed images of the asteroid, as well as highly precise values for its orbit and spin state. Many NEAs have recently been found to have satellites, and the presence of a satellite will also be looked for with the radar.
This close pass by such a large asteroid has little historical precedent, but calculations show that a NEA this large comes this close about once per decade on the average. However, similar close passes in the past were not observed, since it is only in the past decade that the Spaceguard Survey has begun to inventory NEAs in this size range.
NASA NEO Workshop: On June 26-29, nearly one hundred scientists, engineers, astronauts, and managers from NASA, industry, and academia met in Colorado for an informal workshop to discuss how best to respond to NASAŭs new Congressional mandate to survey and characterize sub-km-diameter NEAs in order to understand and mitigate the threat of impacts by such objects. Following the model of the current Spaceguard Survey, which has a goal to discover 90 percent of NEAs larger than 1 km by the end of 2008, the new requests from Congress are for NASA to develop a program to discover 90 percent of the NEAs larger than 140 m by 2020. The value of 140 m was derived in a 2003 NASA study that estimated that 90 percent of the risk of unpredicted impacts from sub-km NEAs could be eliminated (or retired) by extending the Spaceguard Survey down to 140 m diameter. (Full Congressional text is at end of this report).
Discussions at the NEO Workshop were grouped into three general topics: Discovery, Characterization, and Hazard Mitigation. In the areas of Discovery and Characterization, the presentations were about equally divided between techniques involving ground-based astronomy and those that required access to space. For example, both ground-based telescopes and space-based telescopes were described that suggested they could meet the 90 percent goal of 140 m and larger NEAs. In the area of characterization, suggestions were made for broadly-based surveys that could provide some additional information for a substantial fraction of the newly discovered NEAs, for surveys to characterize a small subset of these, and for approaches to be used for intense investigation any NEA that might appear to be a real hazard. The techniques included ground-based telescopes, space-based telescopes, and missions to visit individual NEAs with spacecraft to orbit or land on the surface. Prominently discussed were recent results from the Japanese Hayabusa mission to asteroid Itokawa, the first sub-km NEA to be visited by spacecraft. (A series of technical papers describing Itokawa were just published in the June 6 issue of Science). Under Hazard Mitigation, almost all discussions assumed the requirement to actually deflect an asteroid on a collision course with Earth. Also receiving attention were issues of how much lead time we are likely to have, and under what circumstances different deflection techniques might be used. Prominent were the cases of Apophis, which has a low-probability of impacting in 2036, and 2004 VD17, with a low-probability impact in 2102 (see the NASA NEO Program webpage http://neo.jpl.nasa.gov for current information on these and the other 4000+ known NEAs)
The shift from emphasis on the NEAs larger than 1 km to the sub-km NEAs is a major one. The Spaceguard Survey has already discovered more than 75 percent of those larger than 1 km, and none is on a collision course. However, there are only about 1100 NEAs this large. In contrast, the number of NEAs larger than 140 m is approximately 100,000, and there may be as many as a million that are as large as the object that produced the Tunguska explosion in 1908. Discovery rates in the new surveys will have to be 100 times faster than the current Spaceguard System, and the orbit calculations and archiving of data will scale in the same way. As the survey progresses, many more potential targets for spacecraft missions will also be identified. However, these are at present just hopes and plans; a new survey has not yet been approved, nor any funds appropriated to support it. A formal report from NASA to the Congress will be made later this year.
Press Report: ASTEROID DEFENSE: NASA TO FORMULATE PLANETARY PROTECTION PLAN
By Leonard David
Senior Space Writer
Space.com, 28 June 2006
NASA has begun a fact-finding appraisal of how best to detect, track, catalogue and characterize near-Earth asteroids and comets -- and what can be done to deflect an object found on course to strike our planet. The need to prepare is highlighted this week as astronomers watch a large asteroid that will pass close to Earth on July 3.
Selected experts from a variety of fields are here this week at a NASA workshop on Near-Earth Object (NEO) Detection, Characterization and Threat Mitigation. The meeting is a unique, "idea gathering" event being carried out under direction of the U.S. Congress. The intent is to provide lawmakers with an "executable program" -- but also one that will clearly need funds to implement that program in an orderly and timely fashion.
NASA is on a fast-track to provide by year's end an initial report to Congress that includes an analysis of possible alternatives that might be employed to divert an object on a likely collision course with Earth.
The U.S. Congress has tagged NASA to use its "unique competence" to deal with the potential hazard faced by Earth from such celestial wanderers, in order to help establish a warning and mitigation strategy.
Another chief agenda item on the table is putting in place the survey skills to spot NEOs equal to or greater than 460 feet (140 meters) in diameter. In plotting out that survey program, the merits of ground-based and space-based equipment are to be mulled over to achieve 90 percent completion of a NEO catalogue within 15 years.
This week's gathering is viewed by many as a turning-point in shaping a NEO action plan. "It is historic in the sense that it's the first time the U.S. government has ever had a formal interest in the problem, in the global problem, that is, in the detection, tracking and beginning to look at the mitigation issues. I think that's very significant," said William Ailor of The Aerospace Corporation and on the workshop's mitigation working group.
Similar in view was Russell Schweickart, former Apollo astronaut and Chairman of the B612 Foundation. This group consists of scientists, technologists, astronomers, astronauts, and other specialists that want to significantly alter the orbit of an asteroid in a controlled manner by 2015.
"This is really the first time that NASA will have ever put the words NASA and asteroid deflection together internally ... so it's a very positive move," Schweickart told SPACE.com in a pre-workshop interview. He later advised workshop participants that "this isn't a national issue...this is a planetary issue." Schweickart added that, given the likely scenario of decades of warning time, "this is not a last minute search and destroy mission."
There's been no shortage of ideas how to fend off unfriendly fire from the cosmos: laser beams, space tugboats, gravity tractor, and solar sails for example, as well as using powerful anti-NEO bombs, conventional as well as nuclear.
Ailor, also Director of The Aerospace Corporation's Center for Orbital and Reentry Debris Studies, told SPACE.com that creative ways to deflect Earth-harming NEOs are far from being exhausted.
"People have put a lot of concepts on the table over time," Ailor said. "Now we're beginning to try and develop an organized way of looking at those things and finding out which ones are really viable in the short-term, medium-term, and what technologies do we need to protect and develop for the long-term as well."
A key message early in the workshop is that detection of NEOs is a first priority. The on-going, three-part mantra agreed to by attendees is simple and direct: "Find them early...and find them early...and find them early."
A likely setting is one where a modest Earth impact probability by a NEO is identified decades in advance, then, future mitigation technologies would be most appropriate. Furthermore, "opportunity science" could be derived from such a response. NASA has an interest in harvesting NEOs for their minerals as well as siphoning from them water to further long-range space exploration goals.
Former shuttle astronaut Tom Jones, taking part in the meeting, has had a long-standing interest in asteroids and told SPACE.com: "The NEO workshop this week is both informative -- with the latest NEO data presented by experts in the field -- and encouraging as the space agency seems intent on developing realistic alternatives for detecting most of the potentially hazardous NEOs. That's good ... Congress expects NASA to answer the mail on how to deal with NEOs. This meeting is an important move forward in beginning to materially address the hazard."
As if a warning shot of sorts, several workshop attendees made note of next week's close flyby of Earth of asteroid 2004 XP14. Discovered in late 2004, the space rock will slip by Earth on July 3, passing just beyond the Moon's average distance from Earth.
Congressional text: "The U.S. Congress has declared that the general welfare and security of the United States require that the unique competence of NASA be directed to detecting, tracking, cataloging, and characterizing near-Earth asteroids and comets in order to provide warning and mitigation of the potential hazard of such near-Earth objects to the Earth.
The NASA Administrator shall plan, develop, and implement a Near-Earth Object Survey program to detect, track, catalogue, and characterize the physical characteristics of near-Earth objects equal to or greater than 140 meters in diameter in order to assess the threat of such near-Earth objects to the Earth. It shall be the goal of the survey program to achieve 90 percent completion of its Near-Earth Object catalogue (based on statistically predicted populations of near-Earth objects) within 15 years after the date of enactment of this Act.
The NASA Administrator shall transmit to Congress not later than 1 year after the date of enactment of this Act an initial report that provides the following:
(A) An analysis of possible alternatives that NASA may employ to carry out the Survey program, including ground-based and space-based alternatives with technical descriptions.
(B) A recommended option and proposed budget to carry out the Survey program pursuant to the recommended option.
(C) Analysis of possibly alternatives that NASA could employ to divert an object on a likely collision course with Earth."