Learn More
Pluto's first known satellite, Charon, was discovered in 1978. It has a diameter (approximately 1,200 km) about half that of Pluto, which makes it larger, relative to its primary, than any other moon in the Solar System. Previous searches for other satellites around Pluto have been unsuccessful, but they were not sensitive to objects less, similar150 km in(More)
The two newly discovered satellites of Pluto (P1 and P2) have masses that are small compared to both Pluto and Charon-that is, between 5 x 10(-4) and 1 x 10(-5) of Pluto's mass, and between 5 x 10(-3) and 1 x 10(-4) of Charon's mass. This discovery, combined with the constraints on the absence of more distant satellites of Pluto, reveal that Pluto and its(More)
Observations of Pluto and its solar-tidal stability zone were made using the as discussed by Weaver et al. (2006) and Stern et al. (2006a). Confirming observations of the newly discovered moons were obtained using the ACS in the High Resolution Channel (HRC) mode on 2006 Feb 15 (Mutchler et al. 2006). Both sets of observations provide strong constraints on(More)
We present an improved characterization of the so-called " long vs. short " anomaly, a non-linear behavior of the WFPC2 chips which results in a decrease of the measured count rate with decreasing exposure time. We demonstrate that: 1) this non-linearity depends strictly on total counts in a stellar image, and is independent of exposure time; 2) the effect(More)
We present a set of tasks developed to process dithered undersampled images. These procedures allow one to easily determine the offsets between images and then combine the images using Variable-Pixel Linear Reconstruction, otherwise know as " drizzle ". This algorithm, originally developed for the combination of the images in the Hubble Deep Field(Williams(More)
We obtained Hubble Space Telescope images of 2 Pallas in September 2007 that reveal distinct color and albedo variations across the surface of this large asteroid. Pallas's shape is an ellipsoid with radii of 291 (+/-9), 278 (+/-9), and 250 (+/-9) kilometers, implying a density of 2400 (+/-250) kilograms per cubic meter-a value consistent with a body that(More)
A moon or natural satellite is a celestial body that orbits a planetary body such as a planet, dwarf planet, or an asteroid. Scientists seek understanding the origin and evolution of our solar system by studying moons of these bodies. Additionally, searches for satellites of planetary bodies can be important to protect the safety of a spacecraft as it(More)
We provide some background on pointing ACS, and present the dither and mosaic patterns that will be provided as a convenience for HST Cycle 11 Phase II proposal writers. This report supersedes any previous documents which describe specific ACS dither and mosaic patterns-namely, ACS Instrument Science Report 98-02 by Stiavelli, and the engineering versions(More)