The Southern Hemisphere Asteroid Program

Professor Ed Kruzins and Dr Edwin Peters

Personalise
Large planetoid in empty space

UNSW is playing a key part within a consortium of Universities and Agencies to characterise near-Earth asteroids and objects of a potentially hazardous nature. Viewed from the southern hemisphere these Apollo and Aten class asteroids repeatedly cross Earth’s orbit and represent a dangerous form of natural deep space debris.

In 2015 the Southern Hemisphere Asteroid Radar Program (SHARP) [2] began its first radar observations using available antenna time on the 70m and 34m beam waveguide antennas located at the Canberra Deep Space Communication Complex (CDSCC). This was soon joined by the University of Tasmania (UTAS) in 2021 bringing their array of 12m, 26m and 30m radio telescopes. In 2022 SHARP was joined by the optical telescopes of the University of New South Wales (Viper and Falcon) and University of Western Australia (Falcon and Zadko) with their group of 0.3-1.0m optical telescopes extending the geographic observation capability from the east to west coasts of Australia. The Falcon telescope is a USAFA network managed by the respective universities.

Figure 1. Radar and Optical Telescopes of the Southern Hemisphere Asteroid Radar/Optical Program.

Asteroid Target Observations

The intent of the Southern Hemisphere Asteroid Program is to observe asteroids simultaneously in both radar and optical telescopes. Earth orbit crossing asteroids can range from 10m to 5000m in diameter. Whilst smaller asteroids <1m collide with Earth a few times per year with little damaging effect, a collision with a larger asteroid is much rarer but potentially capable of catastrophic damage to us.

Our work is providing analysis of asteroid radar and optical data contributing to international databases such as the Minor Planets Centre Catalogue to refine orbits, characterize their size, spin and composition thus inferring conjunction risk levels.

Table 1. Selection of asteroid targets observed by Southern Hemisphere Asteroid Program 2022-2024.

Asteroid Target Analysis

We utilise simultaneous observation of asteroids in bi-static radar and optical telescopes to compare the centre frequency (A) shift of the echo spectrum and optical range rate to obtain insights into asteroid position and velocity. The broadening of the radar echo spectral peak (B) and the polarisation ratio μc =Sc/Oc (D/C), offers insights into rotation period, axis of rotation, size and surface roughness of the asteroid when combined with optical observations light curves.

Figure 2. Example refined radar echo spectra of asteroid 2003 SD220 to demonstrate the anatomy of the signal and parameters measured such as centre frequency shift (A), doppler broadening (B) and polarisation ratio (D/C) whilst the shape of the peak offers potential insights into the irregularity of the asteroid from a spherical shape. Courtesy S. Darwell UNSW.

Figure 3. Falcon telescope optical asteroid image showing trajectory, object profile and short-term light curve of asteroid 2012 KY3 observed 16 April 2023 exposure 25sec at siderial rate.

STEM Education

The Southern Hemisphere Asteroid Research student program includes graduate and post graduate students under a program of research supported by supervisors and mentor groups located at UNSW, UWA, CSIRO and NASA JPL.

Figure 4. Simulated radar echo waterfall diagrams from a model illuminated within an anechoic chamber compared to the digital spherical model with a small orbiting companion. Courtesy C. Workman UNSW.

Student projects currently include optimising the processing of asteroid radar echoes, examining asteroid polarisations through Stokes Vector Analysis and comparing simulated asteroid echo signals with hard models in an anechoic chamber to digital models and real echo data from radar observations.

Figure 5. STEM Education Students (Aakash Joshi, Callum Workman, Asha Wiltshier and Tom Riddell (UNSW) and Supervisors (Dr Shinji Horiuchi CSIRO, Dr Edwin Peters UNSW).

Acknowledgements

This research was partially conducted by the University of New South Wales Canberra Space and by the Jet Propulsion Laboratory, California Institute of Technology, the latter under a contract with the National Aeronautics and Space Administration. CDSCC is managed by CSIRO for the National Aeronautics and Space Administration. Murryang, the Parkes radio telescope and the ATCA are managed and operated by the CSIRO as part of the Australian Government. We are also grateful to the University of Tasmania for adding their radio antenna capabilities to the program and to the University of New South Wales and University of Western Australia for adding their optical telescopes to the Southern Hemisphere Radar/Optical asteroid program. We also thank and acknowledge the United States Airforce Academy for use of their Falcon Network and other associates whose facilities continue to contribute to our radio and optical observations. We especially acknowledge the contributions from students Blake Molyneux, Isabelle Saville-Brown, Emi Cashman ANU, Sam Darwell, Asha Wiltshier, Aakash Joshi, Callum Workman, Steve Guedon and Tom Riddell of UNSW ADFA and their supervisors and mentors.

We acknowledge the Traditional Owners of the lands in Australia on which our facilities are located.

References

  1. Near-Earth Object Observations Program | NASA
  2. “First Detection of Two Near Earth Asteroids with a Southern Hemisphere Planetary Radar System” Benson.C, Reynolds.J, Stacy.N, Benner.L, Edwards.P, Baines.G, Boyce.R, Giorgini.J, Jao.J, Martinez.G, Slade.M, Teitlebaum.L, Anabtawi.A, Kahan.D, Oudrhiri.K, Phillips.C, Stevens.J, Kruzins.E, Lazio.J. Radio Science52 (11), 1344-1351 2017
  3. “Improved impact hazard assessment with existing radar sites and a new 70-m southern hemisphere radar installation,” Giorgini, J. D., Slade, M. A., Silva, A., Preston, R. A., Brozovic, M., Taylor, P. A., & Magri, C. 2009, Jet Propulsion Laboratory, National Aeronautics and Space Administration, Pasadena, CA; http://hdl.handle.net/2014/45220
  4. “Capabilities of Earth-based radar facilities for near-Earth asteroid observations,” Naidu, S. P., Benner, L. A. M., Margot, J.-L., Busch, M. W., & Taylor, P. A. 2016, Astron. J., –16– Confidential manuscript submitted to Radio Science submitted; arXiv:1604.01080
  5. “Southern Hemisphere Asteroid Program (SHARP): Targets of Opportunity Observations of Near Earth Asteroids 2019 EA2, 2019 GC6, 2019 SP3 “ Molyneux.B, Horiuchi.S, Stevens.J, Baines.G, Benson.C, Abu Shaban.Z, Giorgini.J, Benner.L, Naidu.S, Phillips.C, Edwards.P, Kruzins.E, Stacy.N, Slade.M, Reynolds.J, Lazio.J, Proceedins of the 43rd COSPAR Scientific Assemply 2021, Sydney Australia.
  6. Final Student Symposium “Southern Hemisphere Asteroid Radar” Presentation by Emi Cashman ANU student intern to CSIRO. Feb 2021.
  7. “Near-Earth asteroid surface roughness depends on compositional class”. L..M. Benner et al.  In: Icarus 198 (2 Dec. 2008), pp. 294–304. issn: 00191035. doi: 10.1016/j.icarus.2008. 06.010.
  8. “Modeling Radar Albedos of Laboratory-Characterized Particles: Application to the Lunar Surface”. A.K. Virkki and S.S. Bhiravarasu. In: Journal of Geophysical Research: Planets 124 (11 Nov. 2019), pp. 3025–3040. issn: 2169-9097. doi: 10.1029/2019JE006006.
  9. “Icy Galilean Satellites: Modelling Radar Reflectivities as a Coherent Backscatter Effect”. G. Black. In: Icarus 151 (2 June 2001), pp. 167–180. issn: 00191035. doi: 10.1006/icar.2001. 6616.
  10. “Polarimetric Decomposition of Near-Earth Asteroids Using Arecibo Radar Observations”. Hickson D.C et al. In: The Planetary Science Journal 2 (1 Feb. 2021), p. 30. issn: 2632- 3338. doi: 10.3847/PSJ/abd846