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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Navier-Stokes Flowfield Simulation of Boeing 747-200 as Platform for SOFIA

Steady and unsteady viscous, three-dimensional flowfields are calculated using a thin layer approximation of Navier-Stokes equations in conjunction with Chimera overset grids. The finite-difference numerical scheme uses structured grids and a pentadiagonal flow solver called "OVERFLOW". The configuration of Boeing 747-200 has been chosen as one of configurations to be used as a platform for the SOFIA (Stratospheric Observatory For Infrared Astronomy). Initially, the steady flowfield of the full aircraft is calculated for the clean configuration (without a cavity to house telescope). This solution is then used to start the unsteady flowfield of a configuration containing cavity housing the observation telescope and its peripheral units. Analysis of unsteady flowfield in the cavity and its influence on the tail empennage, as well as the noise due to turbulence and optical quality of the flow are the main focus of this study. For the configuration considered here, the telescope housing cavity is located slightly downstream of the portwing. The entire flow-field is carefully constructed using 45 overset grids and consists of nearly 4 million grid points. All the computations axe done at one freestream flow condition of M(sub infinity) = 0.85, alpha = 2.5deg, and a Reynolds of Re = 1.85x10deg

Srinivasan, G.R.↗
NASA NTRS2002

The SOFIA Aircraft and its Modification

The primary focus of this paper is to describe the challenges involved in creating this highly modified aircraft that carries a twenty ton telescope to the Stratosphere and then loiters at this desired altitude to act as the observatory "dome" or platform. When the aircraft has reached its nominal cruise condition in the stratosphere of Mach 0.84, a large cavity door opens (the dome opens), exposing a large portion of the interior of the fuselage containing the telescope optics, directly to the Universe. The breadth of topics covered in this paper includes; the relevant criteria and the evaluation process that resulted in the selection of a Boeing 747-SP, the evolution of the design concept, a description of the structural modification including the analysis methods and tools, the aerodynamic issues associated with an open port cavity and how they were addressed, the aero-loads/disturbances imparted to the telescope and how they were measured in the wind tunnel and extrapolated to full size. For completeness, this paper also provides a brief overview of the SOFIA project including the joint project arrangement between NASA and DLR, a top level overview of the science objectives and the resulting requirements, and finally the current project status.

Kunz, Nans↗
NASA NTRS2003

Observations on SOFIA Observation Scheduling: Search and Inference in the Face of Discrete and Continuous Constraints

We did cool stuff to reduce the number of IVPs and BVPs needed to schedule SOFIA by restricting the problem. The restriction costs us little in terms of the value of the flight plans we can build. The restriction allowed us to reformulate part of the search problem as a zero-finding problem. The result is a simplified planning model and significant savings in computation time.

Frank, Jeremy↗
NASA NTRS2002

Submillimeter and Far Infrared Experiment for SOFIA (SAFIRE): Progress and Prospects

SAFIRE/SOFIA is a versatile imaging Fabry-Perot spectrograph covering 100 less than lambda less than 655 microns, with spectral resolving power of approx. l0(exp 3). Selected as a "PI" instrument for the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA), SAFIRE will apply two dimensional pop-up bolometer arrays to provide background limited imaging spectrometry. We describe the instrument design, its application to a range of astro- physical investigations, and current progress and results in the innovative detector and instrument design. SAFIRE/SOFIA is on track for availability in 2006.

Shafer, R. A.↗
NASA NTRS2004

THIS: A Next Generation Tuneable Heterodyne Infrared Spectrometer for SOFIA

A new infrared heterodyne instrument has been developed which allows the use of both tuneable diode lasers (TDL) and quantum cascade lasers (QCL) as local oscillators (LO). The current frequency tuning range of our system extends from 900 to 1100/cm depending on the availability of lasers but is planned to be extended to 600/cm soon. The IF-bandwidth is 1.4 GHz using an acousto-optical spectrometer (AOS). The frequency resolution and stability of the system is approximately 10(exp 7). Currently, mercury-cadmium-telluride (MCT) detectors are used as mixers while new devices like quantum-well-infrared-photodetectors (QWIP) and hot-electron-bolometers (HEB) are investigated. The IF-bandwidth can be extended to about 3 GHz by using a new broadband acousto-optical spectrometer presently under development. The instrument is fully transportable and can be attached to any infrared or optical telescope. The semiconductor laser is stabilized to a Fabry-Perot ring-resonator, which is also used as an efficient diplexer to superimpose the local-oscillator and the signal radiation. As a first step measurements of trace gases in Earth's atmosphere and non-LTE emission from Venus' atmosphere were carried out as well as observations of molecular features in sunspots. Further astronomical observations from ground-based telescopes and the airborne observatory SOFIA are planned for the future. Of particular interest are molecules without a permanent dipole moment like H2, CH4, C2H2 etc.

Sonnabend, Guido↗
NASA NTRS2007

SOFIA - Stratospheric Observatory for Infrared Astronomy

This viewgraph presentation reviews the Stratospheric Observatory for Infrared Astronomy (SOFIA). The contents include: 1) Heritage & History; 2) Level 1 Requirements; 3) Top Level Overview of the Observatory; 4) Development Challenges; and 5) Highlight Photos.

Kunz, Nans↗
NASA NTRS2007

SOFIA: Stratospheric Observatory for Infrared Astronomy

This viewgraph presentation reviews the Stratospheric Observatory for Infrared Astronomy (SOFIA). The contents include: 1) Heritage & History; 2) Level 1 Requirements; 3) Top Level Overview of the Observatory; 4) Development Challenges; and 5) Highlight Photos.

Becker, Eric↗
NASA NTRS2010

Characterization of Extrasolar Planets Using SOFIA

Topics include: the landscape of extrasolar planets, why focus on transiting planets, some history and Spitzer results, problems in atmospheric structure or hot Jupiters and hot super Earths, what observations are needed to make progress, and what SOFIA can currently do and comments on optimized instruments.

Deming, Drake↗
NASA NTRS2011

Thermostructural Analysis of the SOFIA Fine Field and Wide Field Imagers Subjected to Convective Thermal Shock

The originally designed SOFIA aircraft configuration included a system to pre-cool the telescope cavity on the ground before flight, however, due to various factors in the history of the project that system was not installed. This lack of ground pre-cooling was thus the source of the concern over whether or not the imagers would be exposed to a potentially unsafe thermostructural environment when the telescope cavity door was opened at altitude. This concern was in addition to the already existing concern that the air temperature rate of change during flight (both at the same altitude as well as ascent or descent) could cause the imagers to be exposed to an unsafe thermostructural environment. Four optical components were identified as the components of concern - two of higher concern (one in each imager) and two of lower concern (one in each imager). The requirement was to perform transient, coupled thermostructural analyses to determine whether the stress would ever achieve unsafe levels in these components. The analysis effort began by analyzing one component, after which the analyses for the other components was deemed unnecessary.

Kostyk, Chris↗
NASA NTRS2012

SOFIA Closed- and Open-Door Aerodynamic Analyses

Work to evaluate the aerodynamic characteristics and the cavity acoustic environment of the SOFIA (Stratospheric Observatory for Infrared Astronomy) airplane has been completed. The airplane has been evaluated in its closed-door configuration, as well as several open-door configurations. Work performed included: acoustic analysis tool development, cavity acoustic evaluation, stability and control parameter estimation, air data calibration, and external flow evaluation. Qualitative airflow data were obtained during the closed- and open-door flights using tufts on the aft portion of the fuselage. Video was taken from a chase plane. This video was analyzed for various flight conditions, and general flow descriptions of the aft fuselage of the 747SP were developed for the different closed and open door configurations.

Cumming, Stephen↗
NASA NTRS2012

NIMBUS: A Near-Infrared Multi-Band Ultraprecise Spectroimager for SOFIA

We present a new and innovative near-infrared multi-band ultraprecise spectroimager (NIMBUS) for SOFIA. This instrument will enable many exciting observations in the new age of precision astronomy. This optical design splits the beam into 8 separate spectral bandpasses, centered around key molecular bands from 1 to 4 microns. Each spectral channel has a wide field of view for simultaneous observations of a reference star that can decorrelate time-variable atmospheric and optical assembly effects, allowing the instrument to achieve ultraprecise photometry for a wide variety of astrophysical sources

McElwain, Michael W.↗
NASA NTRS2012

SOFIA Observations of S106: Dynamics of the Warm Gas

Context The H II region/PDR/molecular cloud complex S106 is excited by a single O-star. The full extent of the warm and dense gas close to the star has not been mapped in spectrally resolved high-J CO or [C II] lines, so the kinematics of the warm. partially ionized gas, are unknown. Whether the prominent dark lane bisecting the hourglass-shaped nebula is due solely to the shadow cast by a small disk around the exciting star or also to extinction in high column foreground gas was an open question until now. Aims. To disentangle the morphology and kinematics of warm neutral and ionized gas close to the star, study their relation to the bulk of the molecular gas. and to investigate the nature of the dark lane. Methods. We use the heterodyne receiver GREAT on board SOFIA to observe velocity resolved spectral lines of [C II] and CO 11 yields 10 in comparison with so far unpublished submm continuum data at 350 micron (8HARC-Il) and complementary molecular line data. Results. The high angular and spectral resolution observations show a very complex morphology and kinematics of the inner S106 region, with many different components at different excitation conditions contributing to the observed emission. The [C II] lines are found to be bright and very broad. tracing high velocity gas close to the interface of molecular cloud and H II region. CO 11 yields 10 emission is more confined.. both spatially and in velocity, to the immediate surroundings of S 106 IR showing the presence of warm, high density (clumpy) gas. Our high angular resolution submm continuum observations rule out the scenario where the dark lane separating the two lobes is due solely to the shadow cast by a small disk close to the star. The lane is clearly seen also as warm, high column density gas at the boundary of the molecular cloud and H II region.

Simon, R.↗
NASA NTRS2014

SOFIA FORCAST Far-IR Photometry of Comet ISON and Constraints on the Coma Grain Size Distribution

Comet C/2012 S1 (ISON) was unique in that it was a dynamically new comet derived from the nearly isotropic Oort cloud reservoir of comets with a sun-grazing orbit. Infrared (IR) observations were executed on NASA's Stratospheric Observatory For Infrared Astronomy (SOFIA) by the FORCAST instrument on 2013 October 25 UT (r(sub h)=1.18 AU, Delta=1.5AU). Photometry was obtained in FORCAST filters centered at 11.1, 19.7, and 31.5 micron. The observations compliment a large world-wide effort to observe and characterize comet ISON.

Comet dust properties↗
NASA NTRS2017

SOFIA Update and Science Vision

I will present an overview of the SOFIA program, its science vision and upcoming plans for the observatory. The talk will feature several scientific highlights since full operations, along with summaries of planned science observations for this coming year, platform enhancements and new instrumentation.

Smith, Kimberly↗