SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
The toxicological assessments of 2 grab sample canisters (GSCs) from the Shuttle are reported in a table. Based on the end-of-mission sample, the Shuttle atmosphere was acceptable for human respiration.
Following a failure in side 1 of the HST SI C&DH in September 2008, HST Servicing Mission 4 (SM-4) was delayed so that a SI C&DH Orbital Replacement Unit (ORU) could be qualified for flight. This second generation SI C&DH (SI C&DH-2) included several enhancements which increased its thermal dissipation near critical components. In order to maintain the SI C&DH-2 within its operational temperature limits, several thermal modifications were installed prior to its final qualification testing. This paper presents the thermal modifications performed on the SI C&DH-2, as well as the thermal ground test results and a correlation of the SI C&DH-2 thermal design to flight telemetry.
Multi-Layer Insulation (MLI) returned during Servicing Mission 4 are still being analyzed. Analysis has revealed degradation of optical, thermal, and mechanical properties, increased crystallinity, and reduction in fluorine/carbon ratio of aluminized-Teflon fluorinated ethylene propylene (Al-FEP) FEP. These material properties can be affected by high temperatures on orbit, increased radiation exposure, and in some cases contamination from materials in close proximity to the insulation on orbit. Preliminary results support conclusions of previous studies: areas of Al-FEP that received higher levels of solar exposure show more degradation (high temperatures and radiation combined).
Despite more than a decade of coronagraphic imaging of debris disk candidate stars, only 16 have been imaged in scattered light. Since imaged disks provide our best insight into processes which sculpt disks, and can provide signposts of the presence of giant planets at distances which would elude radial velocity and transit surveys, we need to understand under what conditions we detect the disks in scattered light, how these disks differ from the majority of debris disks, and how to increase the yield of disks which are imaged with 0.1" angular resolution. In this talk, I will review what we have learned from a shallow HSTINICMOS NIR survey of debris disks, and present first results from our on-going HST /STIS optical imaging of bright scattered-light disks.
No abstract available
No abstract available
No abstract available
No abstract available
Slitless grism spectroscopy from space offers dramatic advantages for studying high redshift galaxies: high spatial resolution to match the compact sizes of the targets, a dark and uniform sky background, and simultaneous observation over fields ranging from five square arcminutes (HST) to over 1000 square arcminutes (Euclid). Here we present observations of a galaxy at z = 6.57 the end of the reioinization epoch identified using slitless HST grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically) and reconfirmed with Keck + DEIMOS. This high redshift identification is enabled by the depth of the PEARS survey. Substantially higher redshifts are precluded for PEARS data by the declining sensitivity of the ACS grism at greater than lambda 0.95 micrometers. Spectra of Lyman breaks at yet higher redshifts will be possible using comparably deep observations with IR-sensitive grisms.
No abstract available
Using Spitzer observations of classical Cepheids we have measured the true average distance modulus of the Small Magellanic Cloud (SMC) to be18.96 +/- 0.01 stat +/- 0.03sys mag (corresponding to 62+/- 0.3kpc), which is 0.48 +/- 0.01 mag more distant than the LMC. This is in agreement with previous results from Cepheid observations, as well as with measurements from other indicators such as RR Lyrae stars and the tip of the red giant branch. Utilizing the properties of the mid-infrared Leavitt Law we measured precise distances to individual Cepheids in the SMC, and have confirmed that the galaxy is tilted and elongated such that its eastern side is up to20 kpc closer than its western side. This is in agreement with the results from red clump stars and dynamical simulations of the Magellanic Clouds and Stream.
We compare mid-infrared (IR) 3.6 and 4.5 micron Warm Spitzer observations for Cepheids in the Milky Way and the Large and Small Magellanic Clouds. Using models, we explore in detail the effect of the CO rotation-vibration band-head at 4.6 micron on the mid-IR photometry. We confirm the temperature sensitivity of the CO band-head at 4.6 micron and find no evidence for an effect at 3.6 micron. We compare the ([3.6]-[4.5]) period-colour relations in the MW, LMC and SMC. The slopes of the period-colour relations for the three galaxies are in good agreement, but there is a trend in zero-point with metallicity, with the lowest metallicity Cepheids having redder mid-IR colours. Finally, we present a colour-[Fe/H] relation based on published spectroscopic metallicities. This empirical relation, calibrated to the metallicity system of Genovali et al., demonstrates that the ([3.6]-[4.5]) colour provides a reliable metallicity indicator for Cepheids, with a precision comparable to current spectroscopic determinations.
No abstract available
No abstract available
In the field of planet and proto-planetary disk detection, achieving high angular resolution and high dynamic range is a necessity. Ground images are blurred by atmospheric turbulence and therefore adaptive optics is necessary to achieve sub-arcsecond images.
We summarize the specifications for the UVIS filters derived through interaction with the Science Oversight Committee (SOC). A detailed characterization of the 48 UVIS filters will be presented.