For decades, the U.S. Department ofDefense has operated classified spacecraft loaded with high-tech gear to carryout a range of reconnaissance duties. But the satellites have also spotted thehigh-altitude explosions of natural fireballs that routinely dive into theEarth?s atmosphere, and talks are under way to offer scientists access to thatdata.
In the past, the data on the fireballs, causedby small asteroids called bolides, was shared with the near-Earth object (NEO) sciencecommunity, information deemed ideal for understanding the size of small NEOsand the hazardthey pose.
On the other hand, the message from U.S.military and intelligence officials is that they worry about release ofsensitive data gleaned by secretsatellites.
?The bolide thing?
A delicate dance is under way between theU.S. military and scientists to put in place a partnership focused on fireballs? but there are a number of thorny issues on the table.
?We are working it,? said Robert Rego, now chief of Spaceand Cyberspace Operational Integration at Peterson Air Force Base in ColoradoSprings, home of the Air Force Space Command.?
?I would say that we?re working it, not from the perspectiveof ?no and how we can?t do it??but from ?yes, and how wecan do it? and make it beneficial while still protecting a spacecapability,? Rego told SPACE.com in an exclusive interview.
A former brigadier general, Rego transitioned last Octoberto a U.S. Air Force civilian position. Since that time, ?we?ve re-energizedwhat we?re thinking here,? Rego said, noting that it?s still referred to ?as the bolidething.??
Rego said that from the sensor development communityperspective, ?there?s a wide variety of folks that play in that ? some that wecan talk about, some that we can?t.?
The thinking today centers on figuring out the what,in terms of data release, Rego said. ?That?s been a tad contentious,? he said,?but we think we?ve got a data set now that?s valuable, as well as agreed uponin terms of releasability.?
Following an observed incoming bolide by a space-basedasset, date and time of the event, location, altitude, the estimated velocityof the object, as well as the approximate total radiated energy would be madeavailable, Rego said.
Furthermore, an assessment of the type of event ? whether ornot the activity is based upon a comet or an asteroid ? can be provided, hesaid.
?We think that [these factors] give a good balance betweenwhat?s valuable for the researchers and what protects the capabilityof our space systems,? Rego added. This policy would be put in place, hesaid, from a U.S. Air Force perspective.
Fireball data dictionary
But still to be settled is the how the military willdistribute the data.
?Sort of who does it, how do we do it?? Rego pointed out.?How do you make data available for a variety of users, for a variety ofreasons? That data exposure is something that we?re wrestling with here.?
Rego said that a ?data dictionary? ? agreement on terms,methods, the meaning of words ? is also part of the dialogue on data exposure.
In looking for models to push forward on bolide data-sharingwith scientists, Rego pointed to the government?s SpaceSituational Awareness Sharing Program. It provides tracking data on thewhereabouts of space objects with various entities ? including commercial spaceplayers? to help prevent satellite collisions and from trashing the Earth?sorbit even more.
Another possible model, Rego said, is the Civil ApplicationsCommittee (CAC), an interagency committee that coordinates and oversees the federaluse of classified collections.
In recent years, CAC activities have expanded beyondtraditional mapping applications to a broad range of environmental and remotesensing applications central to federal agency missions.
Examples include monitoring volcanoes; detecting wildland fires;coordinating emergencyresponse to natural disasters, such as hurricanes, earthquakes, and floods;monitoring ecosystems, and mapping wetlands.
?So we?re looking there,? Rego said. ?I?d be the last guy onthe planet to put a clock on this thing,? admitting that he was ?dramaticallyoptimistic? when interviewed last year for SPACE.com.
Migration to newer systems
Yet another piece of Rego?s on-going look into bolide data-sharingis resources.
?This would be a new effort,? he said, although not likely somethingthat breaks the bank.
?But it will take an amount of resources, either dollars orpeople to set it up and make sure that the outcome is not unduly biased by apoor set-up,? Rego said.
Given that space-based assets used to support scientificbolide investigations are aging, is migration of this data sharing to newerspace systems in the cards?
?The fundamental answer is yes, Rego said. ?We don?tanticipate putting this effort in place and then have it dwindle to nothing asvehicles age out.?
Studyrecommends NEO data dumps
Mark Boslough, a physicist at Sandia NationalLaboratories in Albuquerque, N. M., served on the mitigation panel of aNational Research Council ?committee that reviewed NEO surveys and hazardmitigation strategies.
The NRC report, called "Defending Planet Earth:Near-Earth Object Surveys and Hazard Mitigation Strategies," was issuedlast January. It outlined options NASA could follow to detect more NEOs, asteroidsand comets that could pose a hazard if they cross Earth?s orbit.
That NRC assessment made a number of high-levelrecommendations.
?Data from NEOairburst events observed by the U.S. Department of Defense satellites shouldbe made available to the scientific community to allow it to improveunderstanding of the NEO hazards to Earth,? the report stated.
Boslough said that being a member of the scientific andnational security communities, he felt he could offer both perspectives, as heviews them.
Impact risk to Earth
?There are legitimate national security reasons for somerestrictions on data release, but these data are extremely valuable to thescientific community in our effort to understand and quantify the impact riskand to develop the most effective mitigation plan against airbursts,? Bosloughtold SPACE.com.
Boslough said that another airburst likethe 1908 Tunguska event is, by far, the most likely threat from asteroidsin our lifetimes.
?Satellite-based observations allow us to better understandthe physics and damage potential of dangerous airbursts, and to better estimatetheir likelihood and risk,? Boslough said. ?Even if the raw data remainclassified at a higher level than scientists want, I hope that there will be amechanism that will allow us to release other information based on theclassified data.?
Longer observation times will provide more statistics, Bosloughadded, allowing researchers to refine the power-law size distribution ? whichby itself is immensely useful for both risk assessment and basic science, hesaid, but doesn?t necessarily require open release of the raw data for everybolide detection.
?It is always better for science when data are openlyavailable for independent scrutiny, but sometimes a balance must be struck betweenopenness and security. I would like to see the balance account for thescientific value of the data,? Boslough concluded.
Unmatched data source
Bolide experts also covet the sheer wealth of data on NEOairbursts that are routinely recorded by military assets in orbit.
?From past experience working with U.S. government satellitedata, the information provided is unmatched by any other data source and allowsscientific analyses which are otherwise impossible,? said Peter Brown, aresearch scientist specializing in meteors, meteorites, meteoroids andasteroids at the University of Western Ontario in London, Ontario, Canada.
Brown is also a core faculty member of the university?s meteorphysics group within the department of physics and astronomy. On the group?swebsite there?s an archive of past fireball measurements with sources to theU.S. Department of Defense, the U.S. Air Force and Sandia National Laboratories? data derived from optical and infrared sensors aboard U.S. satellites.
But the list ends with a U.S. report of a bolide detonatingat 23 statute miles (37 kilometers) over Africa on Oct. 7, 2008.
?The science community remains eager to get thisinformation,? Brown told SPACE.com.
With NEO airburst data, he said, it allows scientists toadvance the understanding of NEO hazards to our planet.
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Leonard David has been reporting on the space industryfor more than five decades. He is past editor-in-chief of the National SpaceSociety's Ad Astra and Space World magazines and has written for SPACE.comsince 1999.