Asteroid Threat Discussed by U.S. Congress

The House Science Committee’s Subcommittee on Space and Aeronautics held a hearing yesterday to discuss Near Earth Objects (NEO). NEOs are asteroids and comets – objects that come close to Earth. This hearing addressed what the potential for impacts is, how the objects are being detected, and what could be done if a serious impact risk were detected.

In opening the hearing (one which would be interrupted several times for votes on Iraq policy) Subcommittee Chair Dana Rohrabacher made a point of mentioning Saddam Hussein and the threat posed by NEOs several a times in the same sentence.

Rohrabacher noted that three close approaches by Near Earth Asteroids had occurred this year and that they “missed us by a hair”. As such, he was seeking to understand the threat better and which agencies are – or should be concerned with understanding it. This is not the first time Rohrabacher has held hearing s on this topic – he has been concerned with it more or less throughout his time in Congress.

Ranking Minority Member Bart Gordon opened by echoing Rohrabacher’s comments and then noted, “Some have argued that the search should be extended to objects of a smaller size.” He also noted that ‘there is a class of objects – long-term comets – that also pose a threat. It is hard to detect them until they come near to Earth.”

Both Rohrabacher and Gordon mentioned the recent House passage of H.R. 5303, the “Charles “Pete” Conrad Astronomy Awards Act” this week. Gordon said, “This is his latest initiative in this regard. We hope that the Senate will pass it.” Rohrabacher later noted that he had spoken to Sen. Bill Nelson and that Nelson has expressed interest in offering this bill in the Senate.

David Morrison/NASA ARC opened his prepared comments by saying “We’re half way through the current Spaceguard survey and have discovered more than half of the 1km sized asteroids that could pose a risk to Earth.” I placing the risk of being hit into context Morrison said, “the chances are very small. However, since the results of being hit are so large it is worth considering.”

“If a NEA is large enough it has the potential to disrupt entire global climate and lead to mass extinction. These objects are 10 km or so in diameter.” He said. “We have surveyed all NEOs of this size and none of them pose a threat. The next level where the survey is concentrating is on NEOs 1 km or larger. 1,100 of them – or more than half of the population have been found. These would not pose extinction level hazard – but would cause massive disruption with a global effect. This is the greatest risk we face today. The objective is to meet the goal of finding 90% of these objects by 2008. ”

Morrison went on to say, “If we chose to expand the survey – we’d look for objects that [if they hit Earth] might not have a global impact but could have a large impact such as an ocean impact causing a tsunami. These objects are to 200-400 meters in size.”

Morrison concluded by saying “We are the first generation of humans to recognize this danger – the first with the technology to detect these asteroids – and we are on the way to being able to deal with the larger ones. This is like taking out fire insurance on your home. You do not expect your house to burn – yet we take out insurance because our homes are too valuable to lose.”

Ed Weiler, Associate Administrator for Space Science reiterated Morison’s concerns noting also that current search programs are “well on the way to identifying 90% of NEOs by 2008.” Weiler went on to say that “NASA also wants to learn more about these primitive bodies” and that it is doing so via $1.6 billion worth of missions.

In particular the NEAR-Shoemaker visited asteroids 253 Mathilde and 433 Eros. “It landed [on Eros] and provided close up descent images we never imagined. The smallest object in the last frame is 4 inches across. That is a NEO we are looking at.”

Weiler outlined current and future missions – Deep Impact, Stardust, Dawn, Muses-C – all of which “promise to increase exponentially our knowledge of these bodies. We may have future missions in the Discovery program as well.”

One focus of this hearing was to discuss which agencies should be involved in studying NEOs. Weiler said, “NASA is a space agency. Our involvement in future activity should be limited to space-based platforms.’ With regard to ground-based facilities (such as telescopes to search for NEOs) Weiler said “there are other entities in the government with greater expertise that should be given that responsibility”

As far as what future knowledge is needed regarding NEOs he said, “We need to know more than just their location. We need to understand their shape, size, and density. This is where NASA and its space missions can make the greatest contribution.”

NASA’s current Inspace Propulsion and the new Nuclear Initiative will allow greater opportunities to study NEOs in next decade. If we have something coming at us, we will want to get there fast.”

Joseph Burns, from Cornell University, representing the NRC Solar System Exploration Survey Committee spoke next. Referring to impacts events from NEOs as “inevitable’ He said “we need to have a census of these objects and an observations of surfaces of these objects so as to be able to mitigate the hazard once we decide to deflect these objects.”

“We need a dedicated, large telescope 20 feet [6.9 meters] across, with a wide field, able to survey the entire night sky every few weeks.” Such a facility (Large-aperture Synoptic Survey Telescope
– LSST) “would be able to detect NEOs down to 300 meters in size, of which 50,000 objects are estimated to exist. We could also find 100,000 supernova, and Kuiper Belt objects at a cost of $125-150 million.”

Burns brought up the topic of why NSF and NASA should share in the cost of such a facility. “This would be an unusual – but not unprecedented arrangement. NSF has reputation of not being able to complete large projects – and has limited money for such projects. NASA’s charter calls for ground-based support. It is important for NASA to be involved in taking a census so that the appropriate space missions can be run.”

Brian Marsden, Director of the Minor Planet Center at the Smithsonian Astrophysical Observatory spoke next. Marsden went through a brief description of the process whereby NEOs are identified, characterized, and confirmed. Specifically, he mentioned The NEO Confirmation Page where such reports are collected, posted, and reviewed.

Marsden mentioned two dominant search activities LINEAR (Lincoln Near Earth Asteroid Research project) and NEAT (Near Earth Asteroid Tracking). He noted that the contribution of amateurs to these activities was mostly to make follow up observations. He suggested that a way needs to be found “to help them improve their equipment.”

While the Minor Planet Center has been able to cope with a surge in observational information – a surge that saw a doubling of information in the past 18 months, Marsden said that his staff of 3 “is not enough to handle the task.”

Brig. Gen. Simon “Pete” Worden, Deputy Director for Operations at the United States Strategic Command spoke next, noting that he was presenting his personal views – not those of the United States Air Force.

“The Department of Defense does not have a position on this [NEO] issue. Over past few years I have been a proponent of looking at the threat. Large objects are important ones to study. When I go to my leadership to discuss something that happens only once every 100 million years they tend to defer on dealing with this in the current budget.”

According to Worden smaller objects hit upper atmosphere every year at a rate of 30 or so. “This is at the nuclear weapons scale.” On 6 June 2002 an event occurred over the Mediterranean, which was observed by satellites. The event released around event 20-30 kilotons of energy – this was large than Hiroshima. “Had this occurred over India or Pakistan it could have triggered a nuclear war – something we have avoided for half a century,” Worden said.

“This might be a topic for ‘shared early warning,’ ” he suggested. “We have sensors that can identify these objects as being asteroids or missiles.”

The hazards from incoming objects occur at much smaller levels as well. Worden cited the Leonids meteor storm as an example. Every 33 years the Earth’s orbit and the cometary debris cloud that causes the Leonids intersect such that the greatest density of the cloud hits Earth. In 2001 and 2002 this lead to some spectacular fireworks in the sky.

“In the 1960’s there was a very large storm” Worden said. “Had it been as bad this time as that time would have lost satellites -including some that make up the GPS (Global Positioning System”.

These smaller objects have potential of producing levels of damage associated with nuclear weapons. Worden made not of an event in 1996 where an incoming object detonated over Greenland with 100 kilotons of explosive force. Had this occurred over a populated area sever damage could have resulted. In 1908, of course, there was the event at Tunguska (also an unpopulated area) where a megaton class explosion occurred causing widespread destruction

Worden said that some consideration is being given to a ‘next generation system that observes the entire sky.” Right now, according to Worden, there is one satellite in orbit – the NSX that can track objects in space, which is “better than ground-based systems. In the future we may have a network of satellites that could serve as an early warning system for small objects.” He suggested that such a system might be an opportunity to use ‘microsatellites’ – small, low cost satellites weighing only several hundred pounds.

Worden also echoed his strong support for HR 5303 and is delighted” that amateurs are becoming involved. In noting the sincerity and dedication of some amateurs, he said “some of them are not so ‘amateur’ – referring to a proposal he had seen recently for a rather large ‘amateur telescope.

Worden said that he is “interested in having the ability to have ‘situational awareness’ of objects not just in Earth orbit – but also in solar orbit.” He also spoke to the issue of mitigating the risk posed by potential impactors. As for dealing with specific threats – i.e. diverting or destroying them he said, “We should wait until threats are discovered.

Echoing statement by other panel members, Worden agreed that much more needs to be learned about NEOs. He suggested the use of space missions which cold be of “dual use”. The example – and precedent he cited – was the Clementine mission wherein Department of Defense objectives were pursed at the same time as lunar and asteroidal research was performed. Again, the use of microsatellites would allow many objects to be observed for a few million dollars per mission. Worden said that this topic is being discussed with NASA and that it is one of the agenda items on next week’s NASA/DoD partnership Council meeting.