Engineering topics
Publications and source records attributed to Simpson, David.
The book (ACS without an Attitude) is an introduction to spacecraft attitude control systems. It is based on a series of lectures that Dr. Hallock presented in the early 2000s to members of the GSFC flight software branch, the target audience being flight software engineers (developers and testers), fairly new to the field that desire an introductory understanding of spacecraft attitude determination and control.
Rapid thermospheric flows can significantly enhance the estimates of the atmospheric loss rate and the structure of the atmospheric corona of a planetary body. In particular, rapid horizontal flow at the exobase can increase the corresponding constituent escape rate. Here we show that such corrections, for both thermal and non-thermal escape, cannot be ignored when calculating the escape of methane from Titan, for which drastically different rates have been proposed. Such enhancements are also relevant to Pluto and exoplanets.
In a recent paper, Sittler et al., (2010) presented new results on the T9 encounter by the Cassini spacecraft when it passed through Titan s induced magnetotail. Two crossings were observed, but the first crossing, event 1, is thought to be out flowing ionosphere plasma. T9 is ideal for CAPS IMS probing of the ionosphere, since the ion densities at the higher altitudes of the T9 flyby approx. 10,000 km, allows measurements to be made down to 1 eV without saturating its detectors. Sittler et al., (2010) reported possible detection of NH4+ ions, but favored the detection of CH5+ and C2H5+ ions. In this report we investigate both the medium mass resolution (straight through (ST)) and high mass resolution (linear electric field (LEF)) composition data from the Cassini Plasma Spectrometer (CAPS) Ion Mass Spectrometer (IMS). We present a more in depth analysis of the composition data and make comparisons with ionospheric models including nitrogen chemistry such as that by Vuitton et al. (2007). The LEF data does not support NH4+ identification, but favors a CH5+ and C2H5+ identification, but also molecular ions C2N+ and CH2NH2+ are chemically allowed possibilities.
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