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All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Planetary Aeronomy and Related Studies

Mercury atmosphere - Sprague and Hunten, in collaboration with Katharina Lodders of Washington University, proposed, mainly on cosmochemical grounds, that S atoms are an important constituent of the atmosphere (30 times more abundant than sodium). This paper has appeared in Icarus. We also suggest that condensed sulfur is an excellent candidate for the radar-bright polar caps, more plausible than water ice because the latter is only barely stable even in permanently-shadowed craters. The best prospect for detection of the vapor is through its resonance lines, a triplet near 1814 A. Mercury is too close to the Sun to be observed by any existing space telescope, but there is some prospect that the search could be made from a Shuttle-based spectrograph such as Lyle Broadfoot's USTAR. Sprague and Hunten have completed an elaborate data analysis of over 100 measurements of the Na D lines, obtained with the 61-inch telescope and our echelle spectrograph. Full account has been taken of the radiative-transfer problem that arises because the Na atmosphere is not optically thin. The output of this code is used in another program that makes an elaborate inverse interpolation in two angles and optical depth and computes the effect of the seeing (always bad for Mercury). The seeing is determined by fitting cuts across a computed image to part of the spectrum adjacent to the sodium lines, and typically ranges from slightly less than 4 arcsec to worse than 6 (diameter at l/e of a Gaussian). The final result is a list of Na abundances, with some information on spatial distribution. One particularly interesting result of further analysis is a strong abundance maximum in the morning relative to the afternoon, confirming an earlier result for potassium, based on much fewer measurements. The analysis are completed during the extension of the present grant. This work depends heavily on the Hapke parameters used to estimate the reflectance of Mercury's surface. The paper by Domingue et al. examines the credibility of the available parameters, which are derived from disk-unresolved photometry, and concludes that errors in the derived Na abundances could be as great as 30%.

Hunten, D. M.↗
NASA NTRS1986

Examples of mesoscale structures and short-term wind variations detected by VHF Doppler radar

The first of three wind profilers planned for operation in central and western Pennsylvania began full-time, high-quality operation during July 1985. It is located about 20 km south-southeast of University Park and operates at 50 MHz. Another 50-MHz radar and a 400-MHz radar are to be installed over the next few months, to complete a mesoscale triangle with sides of 120 to 160 km. During the period since early July, a number of weather systems have passed over the wind profiler. Those accompanied by thunderstorms caused data losses either because the Department computer system lost power or because power went out at the profiler site. A backup power supply and an automatic re-start program will be added to the profiler system to minimize such future losses. Data have normally been averaged over a one-hour period, although there have been some investigations of shorter-period averaging. In each case, preliminary examinations reveal that the profiler winds are indicative of meteorological phenomena. The only occasions of bad or missing data are obtained when airplane noise is occasionally experienced and when the returned power is nearly at the noise level, at the upper few gates, where a consensus wind cannot be determined. Jets streams, clouds, and diurnal variations of winds are discussed.

Forbes, G. S.↗
NASA NTRS1990

Procedural error monitoring and smart checklists

Human beings make and usually detect errors routinely. The same mental processes that allow humans to cope with novel problems can also lead to error. Bill Rouse has argued that errors are not inherently bad but their consequences may be. He proposes the development of error-tolerant systems that detect errors and take steps to prevent the consequences of the error from occurring. Research should be done on self and automatic detection of random and unanticipated errors. For self detection, displays should be developed that make the consequences of errors immediately apparent. For example, electronic map displays graphically show the consequences of horizontal flight plan entry errors. Vertical profile displays should be developed to make apparent vertical flight planning errors. Other concepts such as energy circles could also help the crew detect gross flight planning errors. For automatic detection, systems should be developed that can track pilot activity, infer pilot intent and inform the crew of potential errors before their consequences are realized. Systems that perform a reasonableness check on flight plan modifications by checking route length and magnitude of course changes are simple examples. Another example would be a system that checked the aircraft's planned altitude against a data base of world terrain elevations. Information is given in viewgraph form.

Palmer, Everett↗
NASA NTRS2002

The Star Formation History of Orion and its Environs

During the Winter and Fall 2001 observing campaigns, we obtained multifilter photometry using the Quest camera on the 1mt Schmidt of the Venezuelan National Observatory, to continue the survey of the Orion clouds. In the Winter 2001 season, we obtained photometry for 9 scans at DEC=+5, 3 scans at DEC=-5, and 2 scans at DEC=-3, while 2 additional scans at DEC=-3 were obtained during the Fall 2001 observing campaign (the width of each scan is 2.3 arc minutes). The photometric survey has not been completed this season because the instrument was damaged by lightening on Sep 2001 and operations were suspended until Dec 2001. Observations are still under way. Nonetheless, we have enough scans at -3 and +5 to start selecting candidates for spectroscopic follow up on the next season. Spectra of more than 300 objects was obtained with the FAST spectrograph on the Mt Hopkins 48 inch telescope during observing campaigns Jan-March 2001, and Oct-Dec 2001. Bad weather prevented observations with Hydra on the WIYN telescope on KPNO in Jan 2001. The FAST spectra are been analyzed to select the young population of the regions. Observations in the JHKL bands were obtained for a sample of 20-30 objects in Ori Ia and Ib from scan centered at DEC=-l, with the StellIRCam on the Mt Hopkins 48 inch telescope on Nov 2001. L band observations will be effective for picking up objects surrounded by accretion disks, in which inner disk holes prevent having any excess at shorter wavelength bands. Observations at 10 micrometers and 18 micrometers were obtained in que mode for a sample of 20 objects in Ori Ia and Ib in the same regions as the near IR photometry with the Gemini-South telescope. These new data is presently been reduced and analyzed, together with data from the observing campaigns of 2000. Analysis of Hydra fields at strips centered at DEC=-1 and +1 have confirmed 105 more candidates as low mass pre-main sequence objects. In addition, every target was detected at 10 micrometers and a few at 18 micrometers. With these data, combined with our optical and JHKL photometry, we will construct spectral energy distributions. This will allow us to begin studying the structure of disks around low mass T Tauri stars in the distributed population of the Orion clouds, for direct comparison with that of Taurus. Ours is the first determination of the infrared emission of protoplanetary disks around low mass stars in the Orion region.

Calvet, Nuria↗