Engineering topics

Roellig, Thomas L.

Publications and source records attributed to Roellig, Thomas L..

At least 19 records

NASA NTRS2020

The Infrared Spectrograph on the Spitzer Space Telescope

The Infrared Spectrograph (IRS) instrument on the Spitzer Space Telescope covered the 5 to 38 micron wavelength range at low and medium spectral resolutions. The instrument was very popular during Spitzer’s 5.7 year-long cold mission. Every year it attracted the most proposals, and garnered more observing hours, of any of the science instruments. This success was the culmination of a very long development period, where the instrument design changed radically. When the instrument was first selected by NASA in 1984 it was very complicated. As part of the overall reduction of the size of the SIRTF Observatory following its recovery from the mission’s cancellation in 1991 the IRS became smaller and much, much simpler. The only aspect of the instrument that increased from the original design was the pixel count of the detectors. The new, lean, IRS based on eight axioms: (1) SIRTF is a cost-driven mission; (2) Only Boeing Si:As and Si:Sb 128x128 BIB arrays shall be used; (3) The IRS has all Aluminum housing and optics; (4) Simple optics consisting of surfaces of revolution, flat gratings, and “bolt-and-go” tolerances; (5) No moving parts; (6) Redundancy only for credible single-point failures; (7) Strive for an observing efficiency of 80%; (8) The IRS shall be capable of internal health assessment. This led to a simple, robust, but still extremely powerful final instrument composed of four distinct modules. Many of the features developed for the IRS were subsequently employed in other spacecraft and SOFIA science instrumentation. This presentation will cover the developmental history of the IRS instrument, its final design and performance, and will especially highlight the sage decisions that Jim Houck made along the way that led to its highly successful career on the Spitzer Space Telescope.

Roellig, Thomas L.↗

NASA NTRS2018

Overview of the Origins Space Telescope: Science Drivers to Observatory Requirements

e Origins Space Telescope (OST) mission concept study is the subject of one of the four science and technology definition studies supported by NASA Headquarters to prepare for the 2020 Astronomy and Astrophysics Decadal Survey. OST will survey the most distant galaxies to discern the rise of metals and dust and to unveil the co-evolution of galaxy and blackhole formation, study the Milky Way to follow the path of water from the interstellar medium to habitable worlds in planetary systems, and measure biosignatures from exoplanets. This paper describes the science drivers and how they drove key requirements for OST Mission Concept 2, which will operate between ~5 and ~600 microns with a JWST sized telescope. Mission Concept 2 for the OST study optimizes the engineering for the key science cases into a powerful and more economical observatory compared to Mission Concept 1.

Meixner, Margaret↗

NASA NTRS2017

The Stratospheric Observatory for Infrared Astronomy (SOFIA) - Current Status, Recent Results, Future Plans, and Synergies with the AKARI Archive

The Stratospheric Observatory for Infrared Astronomy comprises a 2.7m diameter telescope mounted in a heavily modified B747SP aircraft. The SOFIA program is a joint US NASA and German DLR program, with the development and operations costs split roughly 80%:20%, respectively. Although the observatory is funded by these two nations, its observing time is open to proposals from astronomers of any nationality. The observatory has been flying and taking scientific data since 2010 and currently observes astronomical targets from the stratosphere for approximately 800 research flight hours per year. Seven science instruments (with an eighth coming online in 2020) cover the visible to sub-millimeter wavelengths with a variety of spectral resolutions ranging up to 1e8. The AKARI Archive with its 1.7 to 180 micron wavelength coverage is a natural complementary source for follow-up observations with SOFIA. This presentation will cover the current SOFIA technical capabilities and will present a few recent science highlights that demonstrate the SOFIA/AKARI complementarity. The presentation will also cover the SOFIA proposal process and will summarize other partnership opportunities for additional observing time on SOFIA.

Astronomy↗

NASA NTRS2017

The Infrared Spectrograph on the Spitzer Space Telescope

SIRTF↗

NASA NTRS2017

NASA's Orgins Space Telescope Mission and Its Synergies with SOFIA

The Origins Space Telescope (OST) is the mission concept for the Far Infrared Surveyor, a study in development by NASA in preparation for the 2020 Astronomy and Astrophysics Decadal Survey. The science program that has been selected to drive the OST performance requirements is broad, covering four main themes: Charting the Rise of Metals, Dust, and the First Galaxies; Unveiling the Growth of Black Holes and Galaxies Over Cosmic Time; Tracing the Signatures of Life and the Ingredients of Habitable Worlds; and Characterizing Small Bodies in the Solar System. The OST telescope itself will have a primary mirror diameter of 8-15 m (depending on the launch vehicle that is selected), will be diffraction-limited at 40m, and will be actively cooled to approximately 5K. Five science instruments have been base-lined for the observatory: a heterodyne instrument covering 150-500 m with a spectral resolving power of R1e7; a low-spectral resolution (R500) spectrometer covering 35-500 m; a high-spectral resolution (R1e5) spectrometer covering 50-500 m; a far-infrared imager (R15) covering 35-500m; and a mid-infrared imagerspectrometer (R15-500) covering 6-40m. In addition to having a vastly higher sensitivity than the corresponding SOFIA instrumentation that will allow more detailed follow-up of SOFIAs discoveries, the OST mission will be configured to provide efficient large-area mapping, which will further complement SOFIAs science capabilities by providing new targets for study by SOFIA. Furthermore, new SOFIA instruments can provide an excellent testbed for the advanced far-infrared detector technologies what will be required to achieve the anticipated OST performance.

Mission↗

NASA NTRS2016

Studies of the Coldest Brown Dwarfs with the James Webb Space Telescope

The coolest T and Y-class Brown Dwarf objects are very faint and are therefore very poorly understood, since they are barely detectable with the current astronomical instrumentation. The upcoming James Webb Space Telescope now in development for a launch in the Fall of 2018 will have vastly increased sensitivity in the near and mid-infrared compared to any current facilities and will not be affected by telluric absorption over its entire wavelength range of operations. As a result it will be an ideal tool to obtain information about the composition and temperature-pressure structure in these objects' atmospheres. This presentation will outline the JWST guaranteed time observing plans for these studies.

Dwarf Objects↗

NASA NTRS2015

Status of the SOFIA Observatory

The SOFIA observatory has been in routine science operations since returning in January from a 6 month-long heavy maintenance period for the aircraft and the telescope assembly. These operations include a successful 6 week deployment to the Southern hemisphere. This presentation will provide an update to the current operational status of the SOFIA observatory, concentrating on the improvements and upgrades that have been implemented since the heavy maintenance period.

Infrared astronomy↗

NASA NTRS2013

Capabilities, Performance, and Status of the SOFIA Science Instrument Suite

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying a 2.5 m telescope onboard a heavily modified Boeing 747SP aircraft. SOFIA is optimized for operation at infrared wavelengths, much of which is obscured for ground-based observatories by atmospheric water vapor. The SOFIA science instrument complement consists of seven instruments: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), GREAT (German Receiver for Astronomy at Terahertz Frequencies), HIPO (High-speed Imaging Photometer for Occultations), FLITECAM (First Light Infrared Test Experiment CAMera), FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), EXES (Echelon-Cross-Echelle Spectrograph), and HAWC (High-resolution Airborne Wideband Camera). FORCAST is a 540 m imager with grism spectroscopy, developed at Cornell University. GREAT is a heterodyne spectrometer providing high-resolution spectroscopy in several bands from 60240 m, developed at the Max Planck Institute for Radio Astronomy. HIPO is a 0.31.1 m imager, developed at Lowell Observatory. FLITECAM is a 15 m wide-field imager with grism spectroscopy, developed at UCLA. FIFI-LS is a 42210 m integral field imaging grating spectrometer, developed at the University of Stuttgart. EXES is a 528 m high-resolution spectrograph, developed at UC Davis and NASA ARC. HAWC is a 50240 m imager, developed at the University of Chicago, and undergoing an upgrade at JPL to add polarimetry capability and substantially larger GSFC detectors. We describe the capabilities, performance, and status of each instrument, highlighting science results obtained using FORCAST, GREAT, and HIPO during SOFIA Early Science observations conducted in 2011.

SOFIA↗

NASA NTRS2012

In-Flight Performance of the Water Vapor Monitor Onboard the Sofia Observatory

NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne observatory flies in a modified B747-SP aircraft in the lower stratosphere above more than 99.9% of the Earth's water vapor. As low as this residual water vapor is, it will still affect SOFIA's infrared and sub-millimeter astronomical observations. As a result, a heterodyne instrument has been developed to observe the strength and shape of the 1830Hz rotational line of water, allowing measurements of the integrated water vapor overburden in flight. In order to be useful in correcting the astronomical signals, the required measured precipitable water vapor accuracy must be 2 microns or better, 3 sigma, and measured at least once a minute. The Water Vapor Monitor has flown 22 times during the SOFIA Early Science shared-risk period. The instrument water vapor overburden data obtained were then compared with concurrent data from GOES-V satellites to perform a preliminary calibration of the measurements. This presentation will cover the.results of these flights. The final flight calibration necessary to reach the required accuracy will await subsequent flights following the SOFIA observatory upgrade that is taking place during the spring and summer of 2012.

Roellig, Thomas L.↗

NASA NTRS2008

The SOFIA Mission - Development Status and Science Outreach Activities

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is nearing its first light obsetvations while in flight. This talk will present the current development status of the aircraft and its telescope, together with the plans for conducting its first science flights beginning in late spring, 2009. This presentation will also address the ongoing activities for SOFIA science outreach and will outline the different opportunities for participation in the Early Science program.

Roellig, Thomas L.↗

NASA NTRS2007

Moderate-Resolution Spitzer Infrared Spectrograph Observations of M, L, and T Dwarfs

We present 10-19 micrometers moderate-resolution spectra of 10 M dwarfs, one L dwarf, and two T dwarf systems obtained with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. The IRS allows us to examine molecular spectroscopic features/lines at moderate spectral resolution in a heretofore untapped wavelength regime. These R = (lamda)/(Delta)(lamda) approximately equal to 600 spectra allow for a more detailed examination of clouds and nonequilibrium chemistry, as well as the molecular features of H2O, NH3, and other trace molecular species that are the hallmarks of these objects. A cloud-free model best fits our mid-infrared spectrum of the T1 dwarf (Sigma) Indi Ba, and we find that the NH3 feature in (Sigma) Indi Bb is best explained by a nonequilibrium abundance due to vertical transport in its atmosphere.We examined a set of objects (mostly M dwarfs) in multiple systems to look for evidence of emission features, which might indicate an atmospheric temperature inversion, as well as trace molecular species; however, we found no evidence of either.

low mass brown dwarfs↗

NASA NTRS2006

Spitzer Spectroscopy of Low-Mass Dwarfs - Clouds and Chemistry at the Bottom of the IMF

Brown dwarfs and low-mass stars show evidence of complicated atmospheres, including a variety of molecular species and clouds. Infrared observations are one of the best probes of the physics of these objects, but up until recently these observations have been limited in studies from ground-based telescopes by atmospheric absorption and insufficient sensitivity. With the launch of the Spitzer Space Telescope with its Infrared Spectrograph (IRS) instrument we now have the capability to undertake a systematic study of the atmospheric structure and chemistry in these cool objects. The IRS Dim Suns team has compiled spectra from objects ranging from M1 dwarfs with effective temperatures 3,800K of down to T8 dwarfs with effective temperatures of 700. This talk will present these results and discuss their implications for our understanding of cool dwarf atmospheric physics and structure.

Roellig, Thomas L.↗

NASA NTRS2004

Spitzer Infrared Spectrograph Observations of L, M, and T Dwarfs

We present here the first mid-infriared spectra of brown dwarfs, together with observations of a low-mass star. Our targets are the M3.5 dwarf GJ 1001 A, the L8 dwarf DENIS-P JO255-4700, and the T1/T6 binary system epsilon Indi Ba/Bb. As expected, the mid- infrared spectral morphology of these objects changes rapidly with spectral class due to the changes in atmospheric chemistry resulting from their differing effective temperatures and atmospheric structures. By taking advantage of the unprecedented sensitivity of the Infrared Spectrograph instrument of the Spitzer Space Telescope we have detected for the first time the 7.6 micron methane band and confirmed the presence of ammonia in a T dwarf atmosphere.

Roellig, Thomas L.↗

NASA NTRS2003

Science with the Space Infrared Telescope Facility

The Space Infrared Telescope Facility (SIRTF), the fourth and final member of NASA's series of Great Observatories, is scheduled to launch on April 15,2003. Together with the Hubbie Space Telescope, the Compton Gamma ray Telescope, and the Chandra X-Ray Telescope this series of observatories offers observational capabilities across the electromagnetic spectrum from the infrared to high-energy gamma rays. SIRTF is based on three focal plane instruments - an infrared spectrograph and two infrared imagers - coupled to a superfluid-helium cooled telescope to achieve unprecedented sensitivity from 3 to 180 microns. Although SIRTF is a powerful general-purpose infrared observatory, its design was based on the capability to address four broad science themes: (1) understanding the structure and composition of the early universe, (2) understanding the nature of brown dwarfs and super-planets, (3) probing protostellar, protoplanetary, and planetary debris disk systems, and (4) understanding the origin and structure of ultraluminous infrared galaxies and active galactic nuclei. This talk will address the design and capabilities of the SIRTF observatory, provide an overview of some of the initial science investigations planned by the SIRTF Guaranteed Time Observers, and give a brief overview of the General Observer proposal process.

Roellig, Thomas L.↗

NASA NTRS2000

The Infrared Telescope in Space Mission

The NASA/Japanese Space Agency Infrared Telescope in Space (IRTS) mission was one of seven experiments on the first Space Flyer Unit (SFU-1). This satellite was launched on a Japanese H-2 expendable launch vehicle from Tanegashima Space Center on March 18, 1995 and was retrieved by the NASA space shuttle the following January for refurbishment and reuse. The IRTS itself consisted of a super-fluid liquid helium-cooled telescope with four infrared focal plane science instruments that operated simultaneously. During its one-month lifetime before the liquid helium was exhausted the IRTS mapped 7% of the sky. These data are now being released to the general astronomical community through IPAC at the California Institute of Technology.

Roellig, Thomas L.↗

NASA NTRS1995

The Infrared Telescope in Space (IRTS) Mission

The Infrared Telescope in Space is a cryogenically-cooled NASA/ISAS space survey instrument scheduled for a February, 1995 launch. The telescope optical system is optimized for studies of extended low surface-brightness objects. Four focal-plane instruments cover wavelengths ranging form 1 to 800 microns.

Roellig, Thomas L.↗

NASA NTRS1994

The Mid-Infrared Spectrometer on the Infrared Telescope in Space (IRTS) mission

The Mid-Infrared Spectrometer (MIRS) is one of the four focal plane instruments on the Infrared Telescope in Space (IRTS) mission. The instrument has been constructed, tested, and calibrated in the laboratory and is presently scheduled to be launched by a Japanese expendable launch vehicle as part of the Space Flyer Unit-1 mission in early 1995. The wavelength coverage of the MIRS ranges from 4.5 to 11.7 microns, with a spectral resolution of 0.23 to 0.36 microns. With the cryogenically cooled optics of the IRTS telescope assembly, the MIRS will be able to make an extremely sensitive survey of both point-source and extended objects over an estimated 10% of the sky.

Roellig, Thomas L.↗

NASA NTRS1991

Telescope beam-profile diagnostics and the solar limb

The basic method is described for determining the solar limb brightness profile properly corrected for spurious limb darkening caused by the far wings of the resolving beams encountered in large far-infrared and radio telescopes. When the far wings of the beam can be independently measured this problem is usually amenable to standard deconvolution procedures. Under a broad range of well-defined cases, solutions to the deconvolution problem are unique to within the discrimination provided by the core of the beam profile. The theory is applied to solar limb scans made recently on the James Clerk Maxwell Telscope to show solar limb brightening in 850 micron radiation.

Lindsey, Charles A.↗