Radar detection of the nucleus and coma of comet hyakutake (C/1996 B2)

Science

Volumn 278, Issue 5345, 1997, Pages 1921-1924

  Harmon, J K ^a   Ostro, S J ^b   Benner, L A M ^b   Rosema, K D ^b   Jurgens, R F ^b   Winkler, R ^b   Yeomans, D K ^b   Choate, D ^b   Cormier, R ^b   Giorgini, J D ^b   Mitchell, D L ^b,c   Chodas, P W ^b   Rose, R ^b   Kelley, D ^b   Slade, M A ^b   Thomas, M L ^b  

^a Arecibo Observatory   (United States)

^b CALIFORNIA INSTITUTE OF TECHNOLOGY   (United States)

^c UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

COMET HYAKUTAKE; RADAR OBSERVATION;

ARTICLE; ASTRONOMY; GEOMETRY; PRIORITY JOURNAL; TELECOMMUNICATION; UNITED STATES;

EID: 0031453892     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.278.5345.1921     Document Type: Article

References (40)

1. P. G. Kamoun, D. B. Campbell, S. J. Ostro, G. H. Pettengill, I. I. Shapiro, Science 216, 293 (1982).
2. P. G. D. Kamoun, thesis, Massachusetts Institute of Technology (1983).
3. I. I. Shapiro et al., Bull. Am. Astron. Soc. 15, 800 (1983); J. K. Harmon, unpublished results.
4. I. I. Shapiro et al., Bull. Am. Astron. Soc. 15, 800 (1983); J. K. Harmon, unpublished results.
5. R. M. Goldstein, R. F. Jurgens, Z. Sekanina, Astron. J. 80, 1745 (1984).
6. J. K. Harmon, D. B. Campbell, A. A. Hine, I. I. Shapiro, B. G. Marsden, Astrophys. J. 338, 1071 (1989).
7. D. B. Campbell, J. K. Harmon, I. I. Shapiro, ibid., p. 1094.
8. A CW experiment involves transmission of a monochromatic (unmodulated) wave and reception of an echo that has been Doppler-broadened by rotation of the target object. Unlike the CW case, an experiment with a modulated (pulsed or coded) transmission can discriminate in echo delay and hence provide a direct nucleus size estimate if the delay resolution is finer than the nucleus' delay depth.
9. The OC echo is the echo component in the circular polarization sense that is opposite the transmitted sense. This is the expected polarization sense for scattering from smooth surfaces or small particles. The SC echo is the component of the echo received in the same circular polarization sense as the transmitted wave. This echo can be produced by scattering from wavelength-scale surface structure or multiple scattering from a collection of particles.
10. We calibrated the spectrum in the standard fashion, using the system temperature to set the absolute noise background level. The calibrated spectrum gives a radar cross section per frequency bin, although here we display the spectra in units of the noise standard deviation. For the radar cross section we use the standard convention, which references to a perfect isotropic reflector.
11. The quoted errors are two standard deviations. Roughly half the variance is random statistical error and the remainder allows for errors in calibration and pointing.
12. S. J. Ostro et al., Astron. J. 102, 1490 (1991); L. A. M. Benner et al., Icarus, in press.
13. S. J. Ostro et al., Astron. J. 102, 1490 (1991); L. A. M. Benner et al., Icarus, in press.
14. E. Kührt, J. Knollenberg, H. U. Keller, Planet. Space Sci. 45, 665 (1997).
15. 2 value measured for comet Sugano-Saigusa-Fujikawa (3). Infrared observations indicate a diameter of less than 1 km for this comet [M. S. Hanner, R. L. Newburn, H. Spinrad, G. J. Veeder, Astron. J. 94, 1081 (1987)].
16. 2 at the time of the 1983 radar observations. Dividing the IAA radar cross section (4, 5) by this area gives the 0.039 value for the albedo. Of those comet nuclei that have been detected by radar, IAA has the best size estimate, which is the reason we adopt it for our reference albedo.
17. D. G. Schleicher, R. L. Millis, D. J. Osip, S. Lederer, Bull. Am. Astron. Soc. 28, 926 (1996).
18. S. Larson, J. Brandt, C. Randall, M. Niedner, ibid., p. 1088.
19. H. U. Keller et al. [Astron. Astrophys. 187, 807 (1987)] estimated dimensions of 15 km by 8 km for the Halley nucleus.
20. Hyakutake nucleus diameter estimates based on infrared observations are 4.2 ± 0.8 km [J. Sarmecanic, M. Fomenkova, B. Jones, T. Lavezzi, Astrophys. J. 483, L69 (1997)] and 4.8 ± 1.0 km [Y. R. Fernandez et al., Bull. Am. Astron. Soc. 28, 1088 (1996)]. The infrared diameters, if correct, tower the radar albedo to 0.012, implying a surface with the consistency of loosely packed snow. Diameter upper limits based on radio continuum measurements are 5.0 km [I. de Pater et al., Planet. Space Sci. 45, 731 (1997); W. J. Altenhoff et al., Bull. Am. Astron. Soc. 28, 928 (1996)], km [Y. R. Fernandez, A. Kundu, C. M. Lisse, M. F. A'Hearn, Planet. Space Sci. 45, 735 (1997)], and 5.7 km (28).
21. Hyakutake nucleus diameter estimates based on infrared observations are 4.2 ± 0.8 km [J. Sarmecanic, M. Fomenkova, B. Jones, T. Lavezzi, Astrophys. J. 483, L69 (1997)] and 4.8 ± 1.0 km [Y. R. Fernandez et al., Bull. Am. Astron. Soc. 28, 1088 (1996)]. The infrared diameters, if correct, tower the radar albedo to 0.012, implying a surface with the consistency of loosely packed snow. Diameter upper limits based on radio continuum measurements are 5.0 km [I. de Pater et al., Planet. Space Sci. 45, 731 (1997); W. J. Altenhoff et al., Bull. Am. Astron. Soc. 28, 928 (1996)], km [Y. R. Fernandez, A. Kundu, C. M. Lisse, M. F. A'Hearn, Planet. Space Sci. 45, 735 (1997)], and 5.7 km (28).
22. Hyakutake nucleus diameter estimates based on infrared observations are 4.2 ± 0.8 km [J. Sarmecanic, M. Fomenkova, B. Jones, T. Lavezzi, Astrophys. J. 483, L69 (1997)] and 4.8 ± 1.0 km [Y. R. Fernandez et al., Bull. Am. Astron. Soc. 28, 1088 (1996)]. The infrared diameters, if correct, tower the radar albedo to 0.012, implying a surface with the consistency of loosely packed snow. Diameter upper limits based on radio continuum measurements are 5.0 km [I. de Pater et al., Planet. Space Sci. 45, 731 (1997); W. J. Altenhoff et al., Bull. Am. Astron. Soc. 28, 928 (1996)], km [Y. R. Fernandez, A. Kundu, C. M. Lisse, M. F. A'Hearn, Planet. Space Sci. 45, 735 (1997)], and 5.7 km (28).
23. Hyakutake nucleus diameter estimates based on infrared observations are 4.2 ± 0.8 km [J. Sarmecanic, M. Fomenkova, B. Jones, T. Lavezzi, Astrophys. J. 483, L69 (1997)] and 4.8 ± 1.0 km [Y. R. Fernandez et al., Bull. Am. Astron. Soc. 28, 1088 (1996)]. The infrared diameters, if correct, tower the radar albedo to 0.012, implying a surface with the consistency of loosely packed snow. Diameter upper limits based on radio continuum measurements are 5.0 km [I. de Pater et al., Planet. Space Sci. 45, 731 (1997); W. J. Altenhoff et al., Bull. Am. Astron. Soc. 28, 928 (1996)], km [Y. R. Fernandez, A. Kundu, C. M. Lisse, M. F. A'Hearn, Planet. Space Sci. 45, 735 (1997)], and 5.7 km (28).
24. Hyakutake nucleus diameter estimates based on infrared observations are 4.2 ± 0.8 km [J. Sarmecanic, M. Fomenkova, B. Jones, T. Lavezzi, Astrophys. J. 483, L69 (1997)] and 4.8 ± 1.0 km [Y. R. Fernandez et al., Bull. Am. Astron. Soc. 28, 1088 (1996)]. The infrared diameters, if correct, tower the radar albedo to 0.012, implying a surface with the consistency of loosely packed snow. Diameter upper limits based on radio continuum measurements are 5.0 km [I. de Pater et al., Planet. Space Sci. 45, 731 (1997); W. J. Altenhoff et al., Bull. Am. Astron. Soc. 28, 928 (1996)], 6.0 km [Y. R. Fernandez, A. Kundu, C. M. Lisse, M. F. A'Hearn, Planet. Space Sci. 45, 735 (1997)], and 5.7 km (28).
25. D. K. Yeomans, personal communication.
26. n and ρ are the nucleus and grain densities, and G is the gravitational constant.
27. ν better than 1.08. These include some antisolar directions, some directions opposite the orbital angular momentum vector, and a band that crosses the comet orbit plane at an azimuth angle of -40° to the sun direction.
28. R. M. West, Int. Astron. Union Circ. 6343 (1996).
29. L. Jorda, J. Lecacheux, F. Colas, Int. Astron. Union Circ. 6344 (1996).
30. W. M. Harris, M. R. Combi, R. K. Honeycutt, B. E. A. Mueller, F. Scherb, Science 277, 676 (1997).
31. m is likely to be very large (∼10 m).
32. D. Schleicher, Int. Astron. Union Circ. 6372 (1996); M. J. Mumma, M. A. Di Santi, N. Dello Russo, D. X. Xie, Int. Astron. Union Circ. 6366 (1996).
33. D. Schleicher, Int. Astron. Union Circ. 6372 (1996); M. J. Mumma, M. A. Di Santi, N. Dello Russo, D. X. Xie, Int. Astron. Union Circ. 6366 (1996).
34. J. Sarmecanic, M. Fomenkova, B. Jones, Bull. Am. Astron. Soc. 28, 1089 (1996).
35. D. C. Jewitt and H. E. Matthews, Astron. J. 113, 1145 (1997).
36. E. L. Wright, Astrophys. J. 346, L89 (1989); D. C. Jewitt and J. X. Luu, Icarus 100, 187 (1992).
37. E. L. Wright, Astrophys. J. 346, L89 (1989); D. C. Jewitt and J. X. Luu, Icarus 100, 187 (1992).
38. J. I. Hage and J. M. Greenberg, Astrophys. J. 361, 251 (1990).
39. D [H. U. Keller and W. J. Markiewicz, Geophys. Res. Lett. 18, 249 (1991)]. However, ρ̇ could also be higher than the steady sublimation value if the gas release is explosive or jetlike.
40. We thank the AlliedSignal Technical Support Corporation personnel who operate the antennas and support facilities at the Goldstone Deep Space Communications Complex under contract with the Jet Propulsion Laboratory. L.A.M.B. was supported as a research associate of the National Research Council. Part of this research was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. The remainder of the work was done at the National Astronomy and Ionosphere Center (Arecibo Observatory), which is operated by Cornell University under a cooperative agreement with NSF and with support from NASA.