Characterizing Reentry using NEXRAD Doppler Radar

Dr. Vishnu Reddy, Assistant Professor, University of Arizona Mike Hankey, Hankey LLC Dr. Richard Linares, Assistant Professor, University of Minnesota

NEXRAD Doppler Radar

• 160 high-resoluon S-band radars operated by Naonal Weather Service. • Covers most of the United States, South Korea including the DMZ, Puerto Rico, Guam, Okinawa and the Azores. • Doppler reflecvity data to 400 km and range data to 230 km available online in near real me. Why Radar?

• Locaon of incoming debris (even when observed by mulple opcal staons) is highly uncertain during dark flight and strongly affected by prevailing wind.

• Doppler radar can track incoming debris during dark flight down to an altude of 4000 feet and enable rapid recovery of both natural and arficial debris. Proof of Concept

Video shot by Pokémon Go players out at night.

Chinese rocket launched on June 25, 2016 Expected to be the workhorse with 70% of future launches Second stage reentered over on June 28, 2016 Several thousand eyewitness accounts and videos Proof of Concept

• Eyewitness reports to the American Meteor Society online reporng tool developed by Co-I Hankey showing the direcon of the incoming debris cloud from Long March 7 second stage. • The inial me and heading from these accounts enabled us to extract the appropriate NEXRAD Doppler radar data from KCIX staon in Cedar City, UT. • Doppler Reflecvity data showing the debris fragments from the event as they rained down over central around 4:41 Zulu on 28th June 2016. • Debris field stretches 120 miles from West to East at an angle of 73 deg. If we assume mass sorng of individual debris fragments, the heaviest fragments would be to the far upper right (YF-11 engines) and the lightest fragments (aluminum HAMR fragments) would be to the le. • Due to lack of funds to recover any fragments, Doppler data were shared to meteorite hunters who went to the field to search for debris. • They recovered two helium COPV (Composite overwrapped pressure vessel) tanks below the radar returns within hours aer reaching the locaon. Long March 7 second stage showing the locaon of four COPV helium tanks.

• Picture of the COPV tank from Long March 7 second stage recovered below our Doppler radar signatures. • Two of the four COPV tanks were recovered and each is about 24 inches across. • The tanks have been handed over to federal authories by the collectors. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 PredictionFigure 1: Concept of behind Reentries an object-oriented tool [Lips and Fritsche (2005)]. 25 •26 NORAD TLEs and re-entry 27 dynamic can be used to 28 29 predict where S/C is expect 30 to re-enter 31 •32 With predicon re-entry 33 locaon the right Doppler 34 35 radar data can be used to 36 find object 37 •38 Trajectory esmaon 39 Kalman filter can be used 40 41 to improve predicon 42 43 Monte Carlo analysis and the concept behind Figure 2: Monte Carlo analysis and the concept behind an object-oriented tool [Parigini 44 an object-oriented tool 45 et al. (2015)]. fpa = flight-path angle. 46 47 48 49 50 51 52 53 54 55 56 57 58 59 27 60 61 62 63 64 65 Development of a prediction tool • Orbital propagaon tool to predict re-entry locaon uncertainty and debris field • Esmated locaon used to determine which radar sites to use along with any eyewitness reports • Re-entry data can be used to update models and physics and to recover space objects