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.

27 April 2009

2009 IAA Planetary Defense Conference: Day 1 (Session 1 - Part 2/2)

- Session 1 Discovery, Tracking, Characterization (Part 2)
Session Chairs: Don Yeomans, Lindley Johnson, Dave Lynch

- Other posters: Some interesting poster:
Canadian NEEOSAT, DLR AsteroidFinder is pat loaf on frsit compact satellite platform, Ball Aerospace, single spacecraft in Venus-like orbit (90% of all diameter objects within 7 years), Halo observatory for IEO (Interior Earth Objects) from KientX and NASA Ames.

- Asteroid Potential Impact Warnings
Chesley, S.R. (Jet Propulsion Laboratory, United States)

Potential warning times: unavoidable consequence of search programs, Pan-STARRS 1 (PS 1) impact warning forecasts, Astrometric errors and star catalog errors,
Warnings are unavoidable, initial probability will rise then drop as orbit is refined, certain number of impact warnings, at some point information becomes good enough for drop off, for Apophis highest peak was 2.7% impact probability - if continued without march 2004 observations - impact probability would have gone to 10%,

Pan-STARRS forecast, a simulation of 4 years PS1 survey (PS1 discovered 6500 NEAs, 1500 per year), 1557 sentry runs on 1135 objects, 17% of discoveries run, 45 days of CPU time (8 cores LINUX workstation, 1 week), 237 Sentry runs returned potential impacts (15%), 12 Torino Scale 1, 12 Palermo larger than -2)

Discovery rate has been declining, TS =1 about 1 per year now, PanSTARRS 1 will not create a little more TS = 1 events,

For 6-8 years seeing problems with astronomy, seeing a persistent problem with declination orbits (declination residuals), two possible causes (problem with asteroid dynamical model, problem with observations), Measurements are all pushed up in celestial frame, systematic errors in star catalogs

By 2008, 58M CCD based asteroid orbits observations (sources are different catalogs), compare to 2MASS catalogs (500 M stars), correct the astronomy from the MPC, take known catalog and apply to fit,

Apophis: Tholen/Nernardi released 33 observations, bias in data, adding de-biased pushes plane beyond the 2036 current keyhole, 2036 impact probability drops by a factor of 5 using approach, greatest shift in inclination, smaller along track shift, perhaps shift impact probability to less than 1 in million, Yarkovsky effect now getting important, starting to become important, detectable in 2011/2012 timeframe

Is PANStarrs 1 able to process data for 2008 TC3s?, operating in different mode, covers sky much less frequently, will not get 1-5 day warning, could see far enough to find them earlier, will not get orbit in 8 days,

- Impact Warning Times for the Next Generation of Asteroid Surveys
Chodas, P.W.; (Jet Propulsion Laboratory, United States)

How much warning time do we have? Define warning time as time at which impact probability goes past 50%, depend upon orbit uncertainties, many factors that affect IP (number/accuracy, geometry, apparitions, length of data arc, time of last observation before impact, close approaches, availability of radar observations), Use 1000 simulated impacts, numerically integrate over 50 year period, in study use various tools (PanSTARRS 1 model/LSST model, follow-up), long term discovery efficiency LSST should find about 90% of objects (after 10 years), Short term discovery efficiency also looked at (H = 20, 85% of objects found 1 year before impact, H=26, much smaller number), how long it would be between mean intervals, approximately internal of 300 years for H=26, Long term warnings (10 years) for H=26 only as 25-33%, at the large and medium sizes, long term warning point is keyed to discovery time, warning point is issued at object’s second apparition, LSST1 generated warning times 10-20% faster than PS 1. PS 1 and LSST not to be run concurrently, from Clark Chapman – suggest running with less than 50% chance (maybe 10% or 15), need to look at the costs for using these systems, if your goal is to find meteorites then meteorite surveys are more efficient, Alan Harris: follow-up is important - how does it work (amateurs?), Alan Harris: follow-up from PanSTARRs.

- Predicting the Apophis Earth Encounters in 2029 and 2036
Giorgini, J.1; Benner, L.A.M.1; Ostro, S.J.1; Nolan, M.C.2; Busch, M.W.3
1Jet Propulsion Laboratory/California Institute of Technology (United States); 2Arecibo Observatory (United States); 3California Institute of Technology (United States)

From Paper in Icarus in 2008, Apophis: albedo (0.33 +/- 0.08), diameter (270 m +/- 60 m), rotation (30.4 hours), 2011: next meaningful optical, 2013 next radar opportunity, 2021 another radar opportunity, 5.6 - 6.3 Earth radaii in 2029,

3 Arecibo campaigns, 18 months (2005-2006), small size, large distance - weak echos (0.19-0.27 AU), next image is 2-3 pixels, orbit solution improvement, 2029 (predicted encounter is 28,000 km closer to earth), using Standard Dynamical Model (SDM), for Apophis consider 6 systematic error sources in SDM for min/mass effects, SDM error (2029: 1600 km, 2036: 65 M km), Yarkovsky (-740 km in 2029, 30M km in 2036), solar radiation pressure error is similar magnitude as Yarkovsky, by 2013 should get the impact of the unmeasured parameters, 22 Earth radii alternation by all these other errors (by 2036), Predictability (mass, spin-pole, etc.) unkwnown,

SDM tends to mis-estimate impact risk, use a min/max effect to exclude threat, future mitigation must make change to account for all uncertainties.

- Panel Discussion

Alan Harris (the elder): Radar confirms Apophis is a slow rotator
David Morrison: thermal infrared impact?
Question from Russian researcher: What level should we get excited about (if anything is higher than 1 in million), what about rendezvous mission (probability more than 1%)
Question on how many current PHSs, within the next 200 years, have resonant returns? (Don Yeomans will answer in a later session)
How about deformation during a close approach)?

- Additional Poster Papers:
Some selected poster papers:
GRAVMOD: ESA Gravity Model for Asteroids and Comets, initiated in 2004 to develop models for gravitational modeling, Spitzer study for low perihelion NEAs, AsteroidFinder/SSB (DLR): first payload on SSB satellite platform, Comet Tempel 1 agrees with lab experiments (Comet Tempel 1 being as fully as Talcum power),

- Minor Planet Center Activities in the Next Generation of Search
Tim Spahr, (Smithsonian Astrophysical Observatory, United States)
Presented by Don Yeomans

6 people at MPC, Tim Spahr (management),
Duty of the MPS is to process every single provisional measurement of small bodies, 63 M observations, 460 k objects, 2 night objects (no orbit) and single night observations (10 M observations)

Most observations arrive as unidentified tracklets (2+ positions), all orbits are improved daily, new objects linked with other objects
All orbits, changed daily, NEOs > 24 hours, comets weekely, 6200 NEO objects, 937 NEOS H<18 (17.75), easily handle 25,000 objects per day, JPL/PISA use data for , NEO probability code (hybrid code), New Possible NEOs (50% score or higher), NEO confirmation pages for observers to look at (also uncertainty paths), NEOCP is 98% automatic, Pan-STARRS will be proving most data in batches or properly 2+ nights, DIGEST2, the probability code, being rewritten in C++ for distribution, WISE spacecraft source: 40 cm IR telescope, ~1000 NEOs, Main challenge is transitioning software to modern OS and database structure, MPC itself is in better shape with support from NASA, still a single center, potential a need for somewhere a center that is shadowing to main continuity in database,

- The Pan-STARRS Survey for Near Earth Objects
Granvik, M.; Wainscoat, R.; Jedicke, R.; Denneau, L. University of Hawaii (United States)

From the Institute of Hawaii, 4x1.8 m R-C teelscoprs, 7 degree FOV, 1.4 Gpixel camera, 700 square deg/night, automated data processing pipeline, first order correction for atmosphere, pushes 4 areas of technology, functional prototype (Ps1) PS1 will be operations in May 2009 on Hawaii, PS1 science consortium, NASA NEO program funds 15% of PS1 operations and MOPS, PS1 NEO survey (morning and evening sweet spot, Moving Object Processing System (MOPS) fully automated to MPC. Intital idea: take existing software, 4 images combined, remove static sky and obtain transients, MOPs 10 M objects. MOPS freely available, shared development with l LSST. Simulated 4 years PS1 survey (results in about 8k NEOs and 1900 PHOs, results in a t least 1 tracklet (24k NEOs, 6. 9 NEOs, ran 130,000 impactors over 100 year (2010-2110), PS1 starting in spring 2009, PS2: starting 2010, Ps4 construction to being after PS2 is ready, build 4 PS1 telescopes per year, PS16 ~ LSST, but /4th the cost, PS1 CCD has problem with the field factor – CCD only a few percent of field factor (88-89%), will attempt to , ~$260M (PS) / $320M (LSST)

- Detecting NEOs using LSST
Zeljko Ivezic (University of Washington, United States)

Need to go to H=24 for 90% completeness of NEOs under 140m in diameter, need to have larger telescopes, 1: 140m V ~25 in 15 sec (10 m class), Field of view of 5-10 degrees, data rate of 30 terabytes/night on the LSST, LSST in Chile - 8.4m, 3200 megapixle, large field of view of 3.5 degrees, 3 mirrors focusing into camera (need for $400M for development and $400 for operations for 10 years), Science drivers for LSST: dark energy/dark matter (10B galaxies), NEOs, time domain (gamma ray), and Milky Way (10B stars), LSST PHA survey - find 80% of NEO > 140m, 15% of time for PHA, PHA completeness reached 90% in 12 years for diameter > 140 m, LSST generates colors of objects, provides additional information than simple magnitude, correlation between color and albedo can be used to estimate size, LSST IOC by 2015, PHA objective met by 2027, effective cost of optimized NEO survey would be $120M, once per year there is a call to become partner organizations with LSST - open project that is open to involvement from international groups/individuals

Chapman: 30% chance of LSST catching 2008 TC3-like objects

- AsteroidFinder/SSB: A German Mission for the Search of IEOs
Mottola, S.1; Behrens, J.1; Börner, A.1; Gerene, S.2; Grundmann, J.T.1; Hahn, G.1; Hallmann, M.1; Kührt, E.1; Michaelis, H.1; Scheibe, K.1; Schmitz, N.1; Spietz, P.1; 1DLR (Germany); 2JAQAR (Netherlands)

Inner region of solar system is largely unexplored, IEO (Inner Earth Orbits ) or Atiras (10^3 have diameter > 100m), only 10 known IEOs (discovery about 1.2/year), why do this mission: inner region exploration, record of inner planets, small observatory in a cost effective platform, above atmosphere of ionosphere, AsteroidFinder is a response to DLR call for proposals for the national compact satellite program (#, orbits, size of NEOs/IEOs, detect space debris from LEO - secondary objective), compact satellite based on DLRSSB, quasi-polar low earth/sunsynch orbit - 650-700 km altitude), 25cm wide telescope, body mounted, no consumables, looked between Earth and Venus, dual launch configuration, focal length of 760 mm, aperture >400 cm^2, EMCCD image stabilization system, 4M pixel array, modeling the survey though the MISKA survey simulator - very conservative scanerio of around 10 discoveries per year (not full-time observation), international team going to Phase B (2013 launch, 1 year mission)

- IR Techniques to Detect and Characterize NEOs
Mainzer, A.1; Wright, E.2; McMillan, R.3; Eisenhardt, P.1; Trilling, D.4; Walker, R.5; 1Jet Propulsion Laboratory (United States); 2UCLA (United States); 3University of Arizona (United States); 4Northern Arizona University (United States); 5MIRA (United States)

- Remote Characterization of NEOs
Rick Binzel (MIT, United States / Paris Observatory, France)

Colors and related to NEOs, may help in develop correct albedo assumptions, asteroids grouped by color, Paper coming out new taxonomy extends from the visible region to 2.5 microns, asteroid taxonomy decoder ring, 42 spectral channels, colrs can also suggest albedo, strong correlation between color group and albedo, direct measurement of low albedo NEOs (so dark, at 1 AU become wamr enough to become visible in near IR, determine bulk physical properties, most meteorites are chondrite or stony iron,

Case study: Apophis: results are in current Issue of Icarus, data indicate that it is LL Chondrites meteorite due to matching, grain density 3.5 +/- 0.1 gcm^-3, 3.2 +/- 0.2 gcm^-3, porosity: 7.9 +/- 4.2%, for 270 m, mass estimate 3.3 +/-1.5, Look at pyramid, net stage of data comes from radar or spacecraft, assumed same overall porosity as Itokowa

2009 DD45: 30-50 m wide asteroid, obtained spectrum, Albedo 0.36, size was really 19 +/- 4 meters,

2008 TC3: F-type spectrum (carbon-rich object, low density, primitive if low albedo and hydrated), 2008 Tc3: carbon-rich anomalous, ureilite (new type of meteorite)
Lessons 1: basic characterization such as color and albedo, lesson 2: correlation between NEO and meteorite, nature holds surprises (2008 TC3)

- Radar Reconnaissance of Near-Earth Asteroids
Benner, L.; Ostro, S.J. (Jet Propulsion Laboratory, United States)

Arecibo and Goldstone are two planetary radars, Goldstone is 350 m in diameter, Arecibo is 20 times more sensitive than Goldstone but fixed, Goldstone 70 m in diameter (slew south and north), different transmitter frequencies, doppler range range (routinely achieve 1000 meters in asteroid size), radar detection of PHA secures its orbit, of ~1000 objects, several hundred can be lost, multiple apparition radar may improve accuracy of orbits (without radar Apophis IP higher by 3-4), 13 comets observed by radar, radar goes past coma of comet, Comet Tuttle (Harmon at Arecibo), radar image different from optical, radar image is a different projection, Itokawa radar image image did not change very much - shape model did not have enough detail, there is no such thing as typical NEO, shape for 4660 Nereu (E-Class asteroid) - accessible NEO, making regular radar observations, by using Yarkovsky effect we can estimate of object's mass, YORP effect (acceleration in object's spin) - directly measured, contact-binary shapes (10% of population) - objects are touching, non principal axis rotations, Mithra (interested rotating case), abundance of binaries (1 in 6 objects seen by Arecibo since upgrade), first triple system (2001 SN263), Near Earth Asteroid Surface Roughness Depends on Compositional Class, 1998 CS 1 (from Jan. 2009) - 1.2 km in diameter - can see small surface features) radar synergies with NEO tracking, characterization and human exploration, do we want to maintain radar observations, funding for Arecibo is in jeopardy, Arecibo has funding thourhg this year, NSF has not announced budget for the future, white paper will have support to keep Arecibo.

Steve Ostro Memorial Symposium, June 4 2009, JPL Von Karman Auditorium

Crimea radar does some data (no real-time analysis capability), bi-static observation, some intercontinental work with other telescopes

- Physical Characterization of Sub-Km NEAs: Low cost Mission Approaches
Morrison, D.1; Chartres, J.1; Coloprete, A.1; Genova, A.1; Jaroux, B.1; Johnson, R.1; Lemke,L.1; Williams, B.2; Chesley, S.3 1NASA Ames Research Center (United States); 2KinetX (United States); 3Jet Propulsion Lab (United States)+

Philosophical and historic perspective and a specific study (NASA Ames Study)

At the beginning, 1990s, we had to understand that there was an impact hazard, these kind of assessments were done by scientific approaches, Clark Chapman and Dave Morrison initially developed consequence charts, must do these studies for mitigation studies,

Second level, deal with mitigation based upon hazard itself, leads to 1 km or larger asteroids, these are very rare, next impact would not be these at 1 km, next generation surveys are looking at the objects wqith the greatest risk, 1-2 km impact is rare, still individually more at risk from large objects than the small objects, this is where we have been until the last few months...

Change of emphasis from the greatest hazard to the most likely event, "what is the next event to happen: will come up with different approach, many more crashes of small planes than of big planes (concern is the big ones), we have the capability to deal with more frequent events - political events will push us to dealing with those...

Work with other communities, do both of these at once, deal with greatest threat and most likely event, can we optimize advanced surveys, public and media demand that we deal with the smaller objects, we mus retain our primary focus on the largest threat (greatest potential to kill people), "faced with a cloud of mosquitoes and a deadly venomous snake, you would swat mosquitoes, but ignore snake at your peril"

Size matters, Eros as a million times less mass then then moon, Apophis as a million less mass than Eros...

What is the minimum spacecraft observations will make a major step in understanding asteroids, looking for a rendezvous, different from our previous spacecraft tours, a flyby of asteroid lasts less than 1 second, flyby not a useful thing to do (less important than radar), key measurements require rendezvous, place spacecraft around object, NASA Ames looks at Apophis mission, require simple instrumentation, doe snot emphasize mineralogy from spectral characterization, only be done up close is size/shape geology, shape density..

Looked at minimum size mission, minimum science and minimum cost, Ames mission study looked at ESPA ring variant, worked about one year at Ames with some NASA HQ, 20 month development, Feb. 2012, 3 month physical characterization, secondary payload, launch along with someone else, spend several months in Earth-moon space, with direct launch one year later, Nav camera/mapping camera/MIR camera/LIDAR/DHU, worked on LCROSS, multiple science products (including mass, shape, density, surface reflectance/temperature, topography, etc.), science ops for one year, ESPA ring, cost is $100M-$200M depending on launch options, partnering with other agencies, concept complete in 2008.

- Panel Discussion

Mexican and Chinese radar efforts are probably long lead items if at all
Spanish researcher talking about new techniques about daylight cameras that are recording bright fireballs (Spanish fireball network)
System designed to optimize to find small objects, what would you know about large systems (largely uncoupled), (Dave M.) when you look at the little ones you find ones that are close - does not save the world from previous impacts,
largest NEOs from inner asteroid belt, 1 meter sized object Yarkovsky can move your throughout the asteroid belt, meteorites sample a larger sample of the asteroid belt then asteroids that we see,
Chesley on Dave M.'s point: very substantial analysis - nothing really concrete on warning and that it is a serious problem, if you set up a system to catalog then you need to operate for decades or centuries (during that time frame, you will cataloged all of your impacts)
Dave M.: if we were to play our odds we would not be in this room, don't bother about these little ones, we are here because of the unlikely events, we would be remiss if we did not look through our data set to find large objects
Alan Harris: a survey is like fishing 0 you catch small in trying to get large ones
Keith Holsapple: what has risen to the top, we need to know what are the physical strength characteristics (need to prod it etc.) - really way to do that is a Don Quixote type mission (some applause for this), one group observes - other impact it, (want to ring its bell/map interior structure? - no) do not need to ping it (seismic might be data to guess), need to do large deformation and large shearing - whack it and watch the pieces,
Peter G.: if you hack it very hard, how does that complicate future mitigation? Keith was talking about a sample asteroid not one that was on the way
Clark Chapman: next generation survey, did not hear about probability or schedule, is it reasonable to assume that in 5-10 years that we will have a bigger survey (how viable are these it)? answer: LSST probability is between 0-1. LSST needs to be prioritized with other contenders, no means that LSST will happen ($50M in private,m $30-40M in public, NSF or someone else needs to award $240M), not obvious that is will happen - NEO driver would help to support project (not suggest that you should assume probability is 1), WISE is happening with mid IR information, NEOCAM is proposed (encouraged to try again)- discovery route is only available NASA program, LSST/WISE - not being paid for entirely by NEO people (we are a small group) to spread costs and benefits, PanSTARRS (PS1 and PS2) - PS4 still depends on funding,
low albedo objects are more difficult to be confident in your match with meteorites,
emissivity has to do with thermal properties (another piece of the puzzle), no emissivity classes for asteroids (yet), the more regolith you have the more chance you have surface is weathered (regolith plays a role)
Wondering if any of the missions looking at long period comet threat
Don Yeomans: if there were no surveys at all, LPC would be 1% of threat), now that the first generation surveys are finishing - asteroid threat is being reduced - LPC somewhere between 1-10% now, NEA are much bigger problem, pushing LPC threat off to the future generations, the more sky you survey the more you pick up LPC, Chesley: all sky survey like LSST good, but still the problem of trajectory prediction for LPCs. IR is ggod for comets (low abledo objects)
Ikari data: Japanese IR telescope currently in orbit (any "Warm" mission)?

What we as a panel should say in our recommendations?
L. Johnson: two things that NASA is doing that would be helped by white paper input, would provide valuable inputs (last day on National Research Council study), Decadal survey (once a decade study by scientific community), difficult to prioritize NEO work/research, what the panel and conference should say to be valuable inputs?
D. Morrison: only first style was scientific, how do we approach the NASA system with anything that approaches mitigation and not science?
L. Johnson: response to question above - how to get support in the NASA system, really is not a constituency that is int he NASA process that is there to talk about mitigation, only strong constituents, only is science community- stems from planetary science community - emphasis has to come out of the planetary science community, no other group that stands a chance, NEO community needs to talk to fellow planetary scientists,
Clark Chapman: Third decadel survey on astrophysics? LSST for astrophysics?
L. Johnson: perhaps an opportunity there but that path is more difficult, planetary decadal survey is a little easier, perhaps a combination of focusing on both decadal surveys
European SSA initiative: European side want a surface (exclude science as user), warning system to inform decision makers, wondering can you also have SSA awareness,
L. Johnson: talking about front end, strong statements from NRC and Decadal survey will feed into policy process, and then what OSTP states, strong feed to OSTP will help broaden attention paid to other elements
P. Gatterson: SSA given to DoD, for them to listen to this would be a defense science board study (OSTP can influence that, they can influence Defense Science board)

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