Team radar from across several institutions were busy this month observing many targets of interest, including Comet 46P/Wirtanen, near-Earth asteroid 2003 SD220, and 7 other NEAs. The cross-institution teams used the NASA-funded Arecibo S-band planetary radar to study these objects in order to measure their astrometry, size, and characterize their surfaces.
Arecibo radar was able to pierce through the dust and gases that surround Comet 46P/Wirtanen to reveal for the first time its diameter and shape. The observing campaign was led by Dr. Ellen Howell, researcher at the University of Arizona's Lunar and Planetary Laboratory (LPL). Dr. Howell was also a staff scientist at Arecibo for many years prior to moving to LPL. Her radar observing team included Dr. Mike Nolan, also from LPL, Drs. Edgard G. Rivera-Valentin and Patrick Taylor, USRA scientists at LPI, and members of the UCF/Arecibo planetary radar group, Drs. Anne Virkki, Sean Marshall, and Flaviane Venditti.
Range-Doppler image sequence of Comet 46P/Wirtanen taken on 17 December 2018 UT. Here the range (veritcal axis) resolution is 20 m/pxl and Doppler frequency (horizontal axis) resolution is 0.05 Hz/pxl. This set of images reveals the comet to be elongated, with a visible extent of some 540 m, which suggests a diameter > 1km. Several radar bright spots, which could be boulders or other structures, including one at the center of the image that barely moves, can be tracked as the body rotates.
To learn more about these comet observations, click here!
Arecibo also observed near-Earth asteroid (163899) 2003 SD220 using the largest radio telescopes in the nation. For these runs, Arecibo used its powerful transmitter while the echoes were received at the Green Bank Telescope in West Virginia. This observing campaign was co-led by Drs. Edgard G. Rivera-Valentin and Patrick Taylor, USRA scientists at LPI who both worked at Arecibo for many years. Arecibo observers included members of the UCF/Arecibo planetary radar group, Drs. Anne Virkki and Sean Marshall. Observers at Green Bank included Amber Bonsall and Drs. Frank Ghigo and Andrew Seymour. Another experiment, called speckle, was carried out where Arecibo transmited and several radio telescopes of the VLBA received the echoes. The speckle experiment was led by Dr. Michael Busch, SETI scientist.
To learn more about these asteroid observations, click here!
(left) Range-Doppler image of (163899) 2003 SD220 taken on 18 December 2018 UT using the NASA-funded, Arecibo S-band planetary radar and receiving at the Green Bank Telescope. Range resolution (vertical axis) is 7.5 m/pxl.
(left) Range-Doppler image of near-Earth asteroid 2012 MS4 taken on 21 December 2018 UT using the NASA-funded, Arecibo S-band planetary radar. Range resolution (vertical axis) is 7.5 m/pxl and the Doppler frequency (horizontal axis) resolution is 0.009 Hz/pxl. The visible extent of the asteroid is 240 m, suggesting a diameter on the order of 500 m; however, radar images suggest 2012 MS4 is elongated and potentially bilobed.
The Arecibo Planetary Radar Program is funded by NASA’s Near-Earth Object Observations Program. The Arecibo Observatory is a facility of the National Science Foundation operated under cooperative agreement by University of Central Florida, Yang Enterprises, and Universidad Metropolitana.