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HST BVI Photometry of Triton and Proteus

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BVI photometry of Triton and Proteus was derived from HST images taken in 1997. The VEGAMAG photometric technique was used. Triton was found to be brighter by a few percent than observations of the 1970s and 1980s, as expected due to the increasingly greater exposure of the bright south polar region. The leading side was also found to be brighter than the trailing side by 0.09 mag in all filters 50 larger than reported by Franz Franz, O.G., 1981. Icarus 45, 602 606. Contrary to our previous results Pascu, D., et al., 1998. Bull. Am. Astron. Soc. 30, 1101, we found no episodic reddening. Our previous conclusions were based on an inaccurate early version of the Charge Transfer Efficiency CTE correction. The present result limits the start of the reddening event reported by Hicks and Buratti Hicks,M.D., Buratti, B.J., 2004. Icarus 171, 210 218. Our B-V result of 0.70 0.01 supports the global bluing described by Buratti et al. Buratti, B.J., Goguen, J.D., Gibson, J., Mosher, J., 1994. Icarus 110, 303 314. Our observations of July 1997 agree with the Voyager results and are among the bluest colors seen. We found Proteus somewhat brighter than earlier studies, but in good agreement with the recent value given by Karkoschka Karkoschka, E., 2003. Icarus 162, 400 407. A leadingtrailing brightness asymmetry was detected for Proteus, with the leading side 0.1 mag brighter. The unique differences in action of the endogenic and exogenic processes on Triton and Proteus provides an opportunity to separate the endogenic and exogenic effects on Triton.

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  • Unmanned Spacecraft

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