• Near- Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

The 2012 TC4 Observing Campaign: The First Planetary Defense Exercise… with a Real

Michael Kelley Planetary Defense Coordination Office NASA HQ

Workshop for Meteorologists, NASA HQ, Thursday, March 15, 2018 www..gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

Goal: Exercise the Planetary Defense system

Test the ability to quickly assemble a large observing campaign to reacquire, track, and characterize a potentially hazardous asteroid, to rapidly produce and share accurate data across institutions and international borders, and to exercise emergency communication channels up through the Agency and Executive Branch, across government agencies, and to the public.

Why 2012 TC4?

Wanted a NEA that did NOT pose a real threat, but had enough uncertainty in its orbit to provide at least a little challenge to reacquire it, and one that had a relatively short timeline to closest

approach. 2 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

3 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

2012 TC4 Observing Campaign Timeline

First suggested: NEOO Program review, January 9-10, 2017 in Tucson, AZ

Kickoff telecon: Early March 2017

Telecons: Monthly to start, more frequently around closest approach

Recovery: July 27 (confirmed August 5)

Closest Approach: October 12, 2017

4 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

2012 TC4 Observing Campaign Participation

Number of non-NASA-HQ participants on e-mail distribution: ~50

Number of institutions/facilities: >35

Countries represented: 14 (Australia, Canada, Chile, Columbia, Germany, Hungary, Israel, Italy, Japan, Korea, Netherlands, Russia, South Africa, and USA)

Both ground- and space-based assets were used

5 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

Types of Data Used to Reacquire, Track and Characterize 2012 TC4

• Visible images

• Photometric measurements

• Radar images

• Visible and near-infrared spectroscopy

6 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research Visible Images ESO VLT 8-meter “Unit Telescopes” • Orbit tracking UT1 or “Antu” • Brightness over time

Reacquisition of 2012 TC4 at the European Southern Observatory • Expected in mid-August based on orbit from 2012 observations • First attempt to recover in late July • Successful recovery in early August, and confirmation of July observations

7 First attempt (left) on July 27, 2017. Second attempt and confirmation (in blue circle, right) on August 5, 2017. www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research Photometry • Lightcurve • Nature of rotational motion • and size constraints

8 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

2012 TC4 has two components to its lightcurve, indicating non-principle-axis rotation (i.e. it’s a tumbler)

P1 = 0.2036 h ± 0.0005 (~12.2 min) P2 = 0.1416 h ± 0.0005 (~8.50 min)

9 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research Photometry • Lightcurve • Nature of rotational motion • Albedo and size constraints Results: • Primary period and amplitude indicate 2012 TC4 is an elongated, tumbling object of non-negligible strength • Second period confirms NPA rotation • Phase behavior indicates high albedo object, which constrains size

10 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research Orbit and tracking • Approximately 700 observations were made between recovery and close approach • Campaign was successful from orbit determination perspective: recovery at first attempt and stable orbit solution • Benefited from remeasurements of older data, and from frequent, direct communication between observers and the orbit analysts • Discovery and correction of clock errors at some observatories • If 2012 TC4 had not been discovered in 2012, it would have been discovered in 2017 by Pan- STARRS two weeks prior to close approach

Significant along-track errors and biases around close approach.

Clock errors are relevant Before campaign, possible impact solutions with probability of 5 in a million.

After recovery, an impact in 2050 became more likely. Peak impact probability of 1 in 180 (Sep 24). Ruled out on Sep 28.

All impact solutions ruled out by the end of the observation campaign. 11 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

12 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

• Close approach at 0.3 LD • E-type asteroid, albedo ~60% • Diameter ~2 m • ~2 min • Potential impacts after 2070 2012: semimajor axis from 1.28 au to 1.41 au 2017: semimajor axis from 1.41 au to 1.62 au

Credit: Marina Brozovic, JPL/Caltech 13 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research Radar Observations Goldstone 70 m • Size • Shape • Rotation Period • Porosity • Metal Content

First detection at Goldstone (middle top) on October 9, 2017 was much weaker than expected, suggesting that the object was significantly smaller than 20 m in size. Bistatic DSS13/Green Bank Images (middle Green Bank 100 m bottom): 20-second intergrations at 13:09:44- 13:56:24 UTC on October 12, 2017.

Arecibo Observatory

14 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

Oct. 12 DSS-13/Green Bank Images Oct. 12: DSS-13/Green Bank Images 13:10-19:10 UTC, 0.50 – 0.86 lunar 03:14-03:22 UT, before closest approach distances, after closest approach

Extremely strong radar target, and one of the closest NEAs ever observed by radar.

Previous Goldstone radar observations in 2012 were unsuccessful, probably due to pointing problems 15 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research Spectroscopy • Visible to near-infrared wavelength region • Compositional information from parameter analysis of spectral features: mineral types and abundances, olivine-pyroxene chemistry, hydration state • Campaign observations affected by weather and power outage • Featureless spectrum made sense when combined with the other datasets: E, M & P taxonomic classes

16 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research 2012 TC4 - Results of Exercise:

• Participation and interest were generated through the NASA-led International Asteroid Warning Network (IAWN) • Astronomers on 6 continents tracked 2012 TC4 • Closest approach occurred at about 27,200 miles (43,800 km), or a little less than 7 Earth radii over the Pacific Ocean south of Australia • Radar observations showed it to be oblong shaped and about 20 x 40 feet (6 x 12 meters) in size • Lightcurve and radar measurements showed it tumbling with a primary period of about a 12 minutes • Albedo calculations show it to be very reflective, which is compatible with spectroscopic measurements 17 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research 2012 TC4 - Results of Exercise (cont.):

• Real world events affected the campaign (Hurricane Maria, Maunakea power outage) • Aided some observatories in finding and correcting timing errors • Modeling efforts included orbit determination, threat assessment and impact effects using measured 2012 TC4 parameters • Events effectively communicated to NASA management, White House, and other federal agencies, as well as within the NEO community • Wide, positive public dissemination through online, print, radio and television media • Precision orbit determination was able to rule out any impact by TC4 for the foreseeable future 18 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

More information about the 2012 TC4 Observing Campaign:

http://2012tc4.astro.umd.edu/

19 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

Backup

20 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

The is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum. It is usually considered in relation to or small (about 10 cm to 10 km in diameter), as its influence is most significant for these bodies.

The Yarkovsky–O'Keefe–Radzievskii–Paddack effect, or YORP effect for short, changes the rotation state of a small astronomical body – that is, the body's spin rate and the obliquity of its pole(s) – due to the scattering of solar radiation off its surface and the emission of its own thermal radiation. The YORP effect is typically considered for asteroids with their heliocentric orbit in the Solar System. The effect is responsible for the creation of binary and tumbling asteroids as well as for changing an asteroid's pole towards 0°, 90°, or 180° relative to the ecliptic plane and so modifying its heliocentric radial drift rate due to the Yarkovsky effect.

21 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research

Mean Magnitudes • -Phase Curve derived from mean magnitudes

• 2012 TC4’s shallower slope indicative of higher albedo object

G Slope 31-70° (mag/°) C 0.09 0.030 S 0.23 0.028 E, V 0.4 0.026

22 www.nasa.gov/planetarydefense • Near-Earth Object Observations Program • Interagency and International Partnerships Planetary Defense Coordination Office • Mitigation Research 2012 TC4 Campaign Participants (not complete)

Last Name First Name Institution Country Reddy Vishnu U. of AZ, LPL USA Kelley Mike NASA-HQ USA Cantillo Laurie NASA-HQ USA Abbasi Viqar CSA Canada Bauer Gerbs UMD - PDS USA Benner Lance JPL USA Brozovic Marina JPL USA Brucker Melissa U. of AZ, LPL USA Bus Bobby NASA-IRTF USA Busch Michael SETI USA Chodas Paul JPL USA Christensen Eric U. of AZ, LPL USA Conrad Al LBTO USA Denneau Larry U. of HI, IfA USA Dotson Jessie NASA-ARC USA Farnham Tony UMD - PDS USA Farnocchia Davide JPL USA Hainaut Olivier ESO Germany Holman Matt MPC USA Koschny Detlef ESA Netherlands Kramer Emily JPL USA Laurin Denis CSA Canada Linder Tyler Astronomical Research Inst. USA Lister Tim LCO USA Micheli Marco ESA Italy Margot Jean-Luc UCLA USA McMillan Bob U. of AZ, LPL USA Mommert Michael NAU USA Moskovitz Nick Lowell Obs. USA Rayner John NASA-IRTF USA Ryan Bill MRO USA Ryan Eileen MRO USA

Scott Lauchie Ottawa Research Centre, Defence Research and Development Canada Canada Sergeev Aleksandr Tersol Observatory Deputy Director Russia Shustov Boris INASAN Director Russia Thirouin Audrey Lowell Obs. USA Tholen Dave U. of HI, IfA USA Thomas Cristina PSI USA Trilling David NAU USA Vlasjuk Valeriy BTA-6 Director Russia Vodniza Alberto Director, University of Narino Observatory Columbia Wainscoat Richard U. of HI, IfA USA Warner Elizabeth UMD - PDS USA Weryk Rob U. of HI, IfA USA Williams Gareth MPC USA Yoshikawa Makoto JAXA Japan 23 Тарадий Владимир Tersol Observatory Director (Vlad) Russia Sickafoose Amanda South African Astronomical Observatory South Africa Erasmus Nick South African Astronomical Observatory South Africa www.nasa.gov/planetarydefense