Jet Propulsion Laboratory

About: Jet Propulsion Laboratory is a facility organization based out in La Cañada Flintridge, California, United States. It is known for research contribution in the topics: Mars Exploration Program & Telescope. The organization has 8801 authors who have published 14333 publications receiving 548163 citations. The organization is also known as: JPL & NASA JPL.

New Infrared Emission Features and Spectral Variations in NGC 7023

Abstract: We observed the reflection nebula NGC 7023, with the Short-High module and the long-slit Short-Low and Long-Low modules of the Infrared Spectrograph on the Spitzer Space Telescope. We also present Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) images of NGC 7023 at 3.6, 4.5, 8.0, and 24 m. We observe the aromatic emission features (AEFs) at 6.2, 7.7, 8.6, 11.3, and 12.7 m, plus a wealth of weaker features. We find new unidentified interstellar emission features at 6.7, 10.1, 15.8, 17.4, and 19.0 m. Possible identifications include aromatic hydrocarbons or nanoparticles of unknown mineralogy. We see variations in relative feature strengths, central wavelengths, and feature widths, in the AEFs and weaker emission features, depending on both distance from the star and nebular position (southeast vs. northwest).

Active dust devils in Gusev crater, Mars: Observations from the Mars Exploration Rover Spirit

Abstract: [1] A full dust devil “season” was observed from Spirit from 10 March 2005 (sol 421, first active dust devil observed) to 12 December 2005 (sol 691, last dust devil seen); this corresponds to the period Ls 173.2° to 339.5°, or the southern spring and summer on Mars. Thermal Emission Spectrometer data suggest a correlation between high surface temperatures and a positive thermal gradient with active dust devils in Gusev and that Spirit landed in the waning stages of a dust devil season as temperatures decreased. 533 active dust devils were observed, enabling new characterizations; they ranged in diameter from 2 to 276 m, with most in the range of 10–20 m in diameter, and occurred from about 0930 to 1630 hours local true solar time (with the maximum forming around 1300 hours) and a peak occurrence in southern late spring (Ls ∼ 250°). Horizontal speeds of the dust devils ranged from <1 to 21 m/s, while vertical wind speeds within the dust devils ranged from 0.2 to 8.8 m/s. These data, when combined with estimates of the dust content within the dust devils, yield dust fluxes of 3.95 × 10−9 to 4.59−4 kg/m2/s. Analysis of the dust devil frequency distribution over the inferred dust devil zone within Gusev crater yields ∼50 active dust devils/km2/sol, suggesting a dust loading into the atmosphere of ∼19 kg/km2/sol. This value is less than one tenth the estimates by Cantor et al. (2001) for regional dust storms on Mars.

Implementation of a Low-Thrust Trajectory Optimization Algorithm for Preliminary Design

Abstract: A tool developed for the preliminary design of low-thrust trajectories is described. The trajectory is discretized into segments and a nonlinear programming method is used for optimization. The tool is easy to use, has robust convergence, and can handle many intermediate encounters. In addition, the tool has a wide variety of features, including several options for objective function and different low-thrust propulsion models (e.g., solar electric propulsion, nuclear electric propulsion, and solar sail). High-thrust, impulsive trajectories can also be optimized.

Survey observations of c-C2H4O and CH3CHO toward massive star-forming regions

Abstract: In order to clarify the formation mechanisms of ethylene oxide (cyclic-C2H4O, hereafter c-C2H4O) and its structural isomer acetaldehyde (CH3CHO), we carried out survey observations of these two molecules toward 20 massive star-forming regions and two dark clouds CH3CHO and c-C2H4O were detected in 10 massive star-forming regions, and CH3CHO was also detected in five others The column densities and the rotational temperatures were derived using the rotation diagram method The column densities of these molecules were derived to be (01-33) × 1014 and (02-50) × 1014 cm-2 for c-C2H4O and CH3CHO, respectively The fractional abundances with respect to H2 are X(c-C2H4O) = 4 × 10-11 to 6 × 10-10 and X(CH3CHO) = 7 × 10-12 to 3 × 10-9 We also detected several transitions of methanol (CH3OH), ethanol (C2H5OH), dimethyl ether [(CH3)2O], methyl formate (HCOOCH3), formic acid (HCOOH), vinyl cyanide (C2H3CN), and ethyl cyanide (C2H5CN) Comparing the abundances of the detected molecules with physical conditions of each source, we found that the abundances of most of the molecules except for c-C2H4O and CH3CHO increase along with the dust temperature of each source On the other hand, the abundances of c-C2H4O and CH3CHO show little correlation with the dust temperature The rotation temperatures of c-C2H4O, CH3CHO, and HCOOH are low (10-40 K) in all sources in spite of the fact that the gas kinetic temperature greatly varies from cloud to cloud This may indicate that the line emission from each molecular species is excited in regions with different physical conditions We performed pseudo-time-dependent chemical reaction simulations based on pure gas-phase reactions and found that the calculated abundances of observed molecules decreased when the gas kinetic temperature was raised We investigated the relationship between the column density of C2H5OH and that of the C2H4O group (c-C2H4O + CH3CHO) because C2H5OH is believed to be a precursor of c-C2H4O and CH3CHO in the gas-phase chemistry scheme If this hypothesis is correct, it is expected that the column density of C2H5OH is related to that of the C2H4O group We found that the column density of the C2H4O group is high in sources where the column density of C2H5OH is high This result is consistent with the above-mentioned hypothesis We also investigated the relationships between the column densities of several organic species [CH3OH, C2H5OH, (CH3)2O, HCOOCH3, C2H3CN, and C2H5CN] and the luminosity-to-mass ratio, LIR/M, in OMC-1, W51A, and Sgr B2(N) We found that the column densities of these molecules are high in sources where LIR/M is high Since LIR/M is believed to be a measure of the star formation rate per unit mass, it indicates that the column densities of these molecules become higher in sources where high star formation activity leads to a higher dust temperature This strongly suggests that the formation of these molecules involves processes on the dust grains and subsequent sublimation to the gas phase, where they can be observed