Results for “infrared light” — Page 3

NASA NTRS1988

Supernova 1987A

Supernova 1987A (February 23, 1987) in the Large Magellanic Cloud is the brightest supernova to be observed since SN 1604 AD (Kepler). Detection of a burst of neutrinos indicates that a neutron star was formed. Radioactive decay of about 0.07 solar mass of Co-56 is responsible for the observed optical light as well as hard X-rays and gamma-ray lines. Ultraviolet, optical, and infrared 'light echoes' and soft X-rays provide information on the distribution of circumstellar matter and the evolution of the progenitor star.

Mccray, Richard↗

NASA NTRS2003

Infrared Spectroscopy as a Chemical Fingerprinting Tool

Infrared (IR) spectroscopy is a powerful analytical tool in the chemical fingerprinting of materials. Any sample material that will interact with infrared light produces a spectrum and, although normally associated with organic materials, inorganic compounds may also be infrared active. The technique is rapid, reproducible and usually non-invasive to the sample. That it is non-invasive allows for additional characterization of the original material using other analytical techniques including thermal analysis and RAMAN spectroscopic techniques. With the appropriate accessories, the technique can be used to examine samples in liquid, solid or gas phase. Both aqueous and non-aqueous free-flowing solutions can be analyzed, as can viscous liquids such as heavy oils and greases. Solid samples of varying sizes and shapes may also be examined and with the addition of microscopic IR (microspectroscopy) capabilities, minute materials such as single fibers and threads may be analyzed. With the addition of appropriate software, microspectroscopy can be used for automated discrete point or compositional surface area mapping, with the latter providing a means to record changes in the chemical composition of a material surface over a defined area. Due to the ability to characterize gaseous samples, IR spectroscopy can also be coupled with thermal processes such as thermogravimetric (TG) analyses to provide both thermal and chemical data in a single run. In this configuration, solids (or liquids) heated in a TG analyzer undergo decomposition, with the evolving gases directed into the IR spectrometer. Thus, information is provided on the thermal properties of a material and the order in which its chemical constituents are broken down during incremental heating. Specific examples of these varied applications will be cited, with data interpretation and method limitations further discussed.

Huff, Timothy L.↗

NASA NTRSDate not supplied

Low-Earth Flight Test of an Inflatable Decelerator (LOFTID) Aeroshell Flight Performance

On November 10, 2022, NASA launched the Low-earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) vehicle as a secondary payload mounted inside the launch vehicle adaptor on an Atlas V 401 out of the Vandenburg Space Force Base (VSFB). The primary payload, Joint Polar Satellite System-2 (JPSS-2), was delivered successfully to a sun synchronous trajectory shortly after launch, at which point the Centaur upper stage performed a burn to de-orbit the system. Once on the desired trajectory to enter the atmosphere the top of the payload adaptor was ejected to expose the LOFTID vehicle, then the LOFTID aeroshell, a Hypersonic Inflatable Aerodynamic Decelerator (HIAD), was deployed and inflated without issue. The Centaur pointed the LOFTID to the desired attitude to enter the atmosphere, spun the assembly to three rpm, separated the reentry vehicle, and finally performed a collision avoidance maneuver to prevent the Centaur from re-contacting the LOFTID after atmospheric entry. The LOFTID vehicle maintained the design attitude and spin rate from separation to atmospheric entry, roughly 30 minutes, demonstrating the aeroshell did not experience any energy damping from inflatable structure flexibility. The LOFTID vehicle entered the atmosphere over Alaska at >8km/sec and decelerated as designed demonstrating stable flight from hypersonic entry through subsonic parachute deployment. On-board visible light cameras captured the reactions of the heatshield through all phases of flight and co-located infrared light cameras captured the temperature distribution of the aft side of the heat shield anchored to a distribution of thermocouples on the inflatable structure (IS) in the field of view. Thermocouples were also embedded in the forward side of the aeroshell both in the Flexible Thermal Protection System (FTPS) as well as the IS. This presentation will discuss aeroshell response to the atmospheric entry. The visible light cameras captured mechanical response of the IS to the loads applied in the different phases of entry. Events seen on the visible light cameras correlate with the response of the load cell pins on webbing elements that attach the aeroshell to the centerbody structure. Thermocouple data captured verifies the aerothermal response of the aeroshell was in-kind with pre-flight analysis predictions although some-what lower in most locations. This data will allow the improvement of the aeroshell modeling tools predictive capability. Post-flight inspection of the aeroshell after splash down and ocean recovery shows that all the aeroshell materials and manufacturing techniques developed over the past 15 years of HIAD technology development performed as de-signed at large scale, a scale which cannot be replicated in ground test facilities. The HIAD supported the LOFTID vehicle high in the water after touching down under parachute and maintained buoyancy and integrity for the hour it took to position the recovery vessel near the LOFTID after splash down. There was no indication the HIAD would have experienced an issue maintaining buoyancy for many more hours after water impact as the component maintained adequate inflation pressure more than 12 hours after water extraction with no additional inflation gas in tanks, as the inflation gas remaining in the tank was vented prior to impact. The LOFTID aeroshell was an unqualified success and has opened up opportunities for commercial application.

LOFTID Aeroshell Flight Performance↗

NASA NTRSDate not supplied

Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) Aeroshell Performance

On November 10, 2022, NASA launched the Low-earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) vehicle as a secondary payload mounted inside the launch vehicle adaptor on an Atlas V 401 out of the Vandenburg Space Force Base (VSFB). The primary payload, Joint Polar Satellite System-2 (JPSS-2), was delivered successfully to a sun synchronous trajectory shortly after launch, at which point the Centaur upper stage performed a burn to de-orbit the system. Once on the desired trajectory to enter the atmosphere the top of the payload adaptor was ejected to expose the LOFTID vehicle, then the LOFTID aeroshell, a Hypersonic Inflatable Aerodynamic Decelerator (HIAD), was deployed and inflated without issue. The Centaur pointed the LOFTID to the desired attitude to enter the atmosphere, spun the assembly to three rpm, separated the reentry vehicle, and finally performed a collision avoidance maneuver to prevent the Centaur from re-contacting the LOFTID after atmospheric entry. The LOFTID vehicle maintained the design attitude and spin rate from separation to atmospheric entry, roughly 30 minutes, demonstrating the aeroshell did not experience any energy damping from inflatable structure flexibility. The LOFTID vehicle entered the atmosphere over Alaska at >8km/sec and decelerated as designed demonstrating stable flight from hypersonic entry through subsonic parachute deployment. On-board visible light cameras captured the reactions of the heatshield through all phases of flight, and co-located infrared light cameras captured the temperature distribution of the aft side of the heat shield anchored to a distribution of thermocouples on the inflatable structure (IS) in the field of view. Thermocouples were also embedded in the forward side of the aeroshell both in the Flexible Thermal Protection System (FTPS) as well as the IS. This paper will discuss aeroshell response to the atmospheric entry. The visible light cameras captured mechanical response of the deployable aeroshell to the loads applied in the different phases of entry. Events seen on the visible light cameras correlate with the response of the load cell pins on webbing elements that attach the aeroshell to the centerbody structure. Thermocouple data captured verifies the aerothermal response of the aeroshell was in-kind with pre-flight analysis predictions although somewhat lower in most locations. This data will allow the improvement of the aeroshell modeling tools predictive capability. Post-flight inspection of the aeroshell after splash down and ocean recovery shows that all the aeroshell materials and manufacturing techniques developed over the past 15 years of HIAD technology development performed as designed at large scale, a scale which cannot be replicated in ground test facilities. The HIAD supported the LOFTID vehicle high in the water after touching down under parachute and maintained buoyancy and integrity for the hour it took to position the recovery vessel near the LOFTID after splash down. There was no indication the HIAD would have experienced an issue maintaining buoyancy for many more hours after water impact as the component maintained adequate inflation pressure more than 24 hours after water extraction with no additional inflation gas in tanks, as the inflation gas remaining in the tank was vented prior to impact.

Entry Descent Landing Atmospheric Entry Deployable↗

NASA NTRSDate not supplied

Overview and Performance of the LOFTID Instrumentation Suite

On November 10, 2022, NASA launched the Low-earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) vehicle as a secondary payload mounted inside the launch vehicle adaptor on an Atlas V out of the Vandenburg Space Force Base (VSFB). The primary payload, Joint Polar Satellite System-2 (JPSS-2), was delivered successfully to a sun synchronous trajectory shortly after launch, at which point the Centaur upper stage performed a burn to de-orbit the system. Once on the desired trajectory to enter the atmosphere the payload adaptor canister was ejected by the payload adapter separation system to expose the packed LOFTID vehicle, then the LOFTID aeroshell, a Hypersonic Inflatable Aerodynamic Decelerator (HIAD), was deployed and inflated as planned. The Centaur pointed the LOFTID vehicle to the desired attitude to enter the atmosphere, spun the assembly to roughly three rpm, and separated the reentry vehicle. The LOFTID vehicle entered the atmosphere over Alaska at >8km/sec and decelerated as designed demonstrating stable flight from hypersonic entry through subsonic parachute deployment. On-board visible light cameras captured the reactions of the heatshield through all phases of flight, and co-located infrared light cameras captured the temperature distribution of the aft side of the heat shield anchored to a distribution of thermocouples on the inflatable structure (IS) in the field of view. Thermocouples were also embedded in the forward side of the aeroshell both in the Flexible Thermal Protection System (FTPS) as well as the IS. Heat Flux Gages and Pressure Transducers measured the heating rate and surface pressure experienced by the rigid nose of the reentry vehicle. Loadcells measured the interface loads between the IS and the rigid centerbody. This paper will discuss many of the key instruments flown on the successful LOFTID technology demonstration mission and will provide some high level results, while pointing to more detailed papers on the post-flight analyses.

Gregory T Swanson↗

NASA NTRSDate not supplied

Overview and Performance of the LOFTID Instrumentation Suite

On November 10, 2022, NASA launched the Low-earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) vehicle as a secondary payload mounted inside the launch vehicle adaptor on an Atlas V out of the Vandenburg Space Force Base (VSFB). The primary payload, Joint Polar Satellite System-2 (JPSS-2), was delivered successfully to a sun synchronous trajectory shortly after launch, at which point the Centaur upper stage performed a burn to de-orbit the system. Once on the desired trajectory to enter the atmosphere the payload adaptor canister was ejected by the payload adapter separation system to expose the packed LOFTID vehicle, then the LOFTID aeroshell, a Hypersonic Inflatable Aerodynamic Decelerator (HIAD), was deployed and inflated as planned. The Centaur pointed the LOFTID vehicle to the desired attitude to enter the atmosphere, spun the assembly to roughly three rpm, and separated the reentry vehicle. The LOFTID vehicle entered the atmosphere over Alaska at >8km/sec and decelerated as designed demonstrating stable flight from hypersonic entry through subsonic parachute deployment. On-board visible light cameras captured the reactions of the heatshield through all phases of flight, and co-located infrared light cameras captured the temperature distribution of the aft side of the heat shield anchored to a distribution of thermocouples on the inflatable structure (IS) in the field of view. Thermocouples were also embedded in the forward side of the aeroshell both in the Flexible Thermal Protection System (FTPS) as well as the IS. Heat Flux Gages and Pressure Transducers measured the heating rate and surface pressure experienced by the rigid nose of the reentry vehicle. Loadcells measured the interface loads between the IS and the rigid centerbody. This paper will discuss many of the key instruments flown on the successful LOFTID technology demonstration mission and will provide some high level results, while pointing to more detailed papers on the post-flight analyses.

spacecraft design↗

NASA NTRS2005

Sol-Gel Glass Holographic Light-Shaping Diffusers

Holographic glass light-shaping diffusers (GLSDs) are optical components for use in special-purpose illumination systems (see figure). When properly positioned with respect to lamps and areas to be illuminated, holographic GLSDs efficiently channel light from the lamps onto specified areas with specified distributions of illumination for example, uniform or nearly uniform irradiance can be concentrated with intensity confined to a peak a few degrees wide about normal incidence, over a circular or elliptical area. Holographic light diffusers were developed during the 1990s. The development of the present holographic GLSDs extends the prior development to incorporate sol-gel optical glass. To fabricate a holographic GLSD, one records a hologram on a sol-gel silica film formulated specially for this purpose. The hologram is a quasi-random, micro-sculpted pattern of smoothly varying changes in the index of refraction of the glass. The structures in this pattern act as an array of numerous miniature lenses that refract light passing through the GLSD, such that the transmitted light beam exhibits a precisely tailored energy distribution. In comparison with other light diffusers, holographic GLSDs function with remarkably high efficiency: they typically transmit 90 percent or more of the incident lamp light onto the designated areas. In addition, they can withstand temperatures in excess of 1,000 C. These characteristics make holographic GLSDs attractive for use in diverse lighting applications that involve high temperatures and/or requirements for high transmission efficiency for ultraviolet, visible, and near-infrared light. Examples include projectors, automobile headlights, aircraft landing lights, high-power laser illuminators, and industrial and scientific illuminators.

Yu, Kevin↗

NASA NTRS1994

Near-infrared imaging of Markarian 231: Evidence for a double nucleus

Near-infrared (1.2-2.4 micrometers) images are presented for the central 10 arcsec of the Seyfert 1 galaxy Markarian 231. We find a faint, but intrinsically luminous (M(sub k) approximately -20.7) secondary peak in the near-infrared light distribution approximately 3.5 arcsec (2.7 kpc) south of the primary Seyfert 1 nucleus. Since there is no optical or infrared evidence for ongoing star formation at the location of this secondary peak, and its near-infrared luminosity and color are comparable to slightly reddened spiral bulges or elliptical nuclei, we identify this peak with the stripped nucleus of the companion galaxy involved in the Mrk 231 merger event. Depending upon the exact ratio of the masses of the primary and secondary nucleus in the Mrk 231 system we estimate a merger time scale of less than or equal to 10(exp 9) yr. The morphology of the southern nucleus suggests that it may have recently survived a close passage (r less than 200 pc) with the Seyfert 1 nucleus on a highly elliptical orbit, in which case the merger time scale may be significantly shorter (approximately 10(exp 7) yr. We re-calculate the average merger time scale for the seven ultraluminous infrared galaxies with double nuclei in the Bright Galaxy Sample (the BGS) of Soifer et al. (AJ, 98, 766 (1989)) and derive a value of approximately 10(exp 8) yr. Since seven of ten of the ultraluminous infrared galaxies in the BGS are now known to be double, we estimate the ultraluminous 'phase' may be close to this value. Along with Arp 220 and Mrk 273, Mrk 231 is the third member of the class to possess a high brightness temperature non-thermal radio core and a double nucleus, suggesting the time scale for the generation or fueling of the active nucleus can be much less than the dynamical time scale for the merger of the progenitor nuclei.

Armus, L.↗

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 NTRS1985

Coordinated observations of X-ray bright BL lacertae objects

Simultaneous multifrequency observations of the BL Lac object Mkn421 covering radio through X-ray wavelengths were performed. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs after subtracting the optical and infrared light of the underlying galaxy. Physical parameters of Mkn421 are discussed in terms of the synchrotron self-Compton model. Taking the spectral turnover between infrared and radio for synchrotrom self absorption, the radio emmision originates in a more extended region than the infrared to X-ray emission, the source size of which should be less than .01 milliarcseconds. Relativistic beaming is required if the angular size is smaller than a few times .001 milliarcseconds. A possible explanation of the spectral change during the two epochs is also discussed.

Urry, C. M.↗

NASA NTRS1987

Simultaneous multifrequency observations of the BL Lacertae object Markarian 421

Simultaneous multifrequency observations of the BL Lac object Mrk 421 covering radio through X-ray wavelengths were performed on two occasions separated by 5 weeks in January and March 1984, and each observation was coordinated for about 1 week. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs after subtracting the optical and infrared light of the underlying galaxy. The spectra show the gradual steepening toward high frequency; the power law indices are about 0.1, about 0.6, and about 1.0 for radio, infrared-optical, and UV bands, respectively. The UV and optical-infrared fluxes decreased by about 20 percent in 5 weeks, while the radio flux remained stable. The X-ray flux decreased by a factor of about 2, and the change was more pronounced at hard X-rays, which suggest that X-ray emission possibly consists of two components. The degree of polarization at the optical band varied on the time scale of a few days, while the position angle remained unchanged. Physical parameters of Mrk 421 are discussed in terms of the synchrotron self-Compton model.

Makino, F.↗

NASA NTRS1973

Light reflectance of leaf constituents

It is shown how various leaf constituents differ in reflecting light over the 370- to 1100-nm wavelength interval. The premise tested is that refractive index discontinuities in leaves, other than air-cell interfaces, contribute to the reflectance of near-infrared light.-

Gausman, H. W.↗

NASA NTRS1998

1.54 micron Emission from Erbium implanted GaN for Photonic Applications

The development of efficient and compact light sources operating at 1.54 micron is of enormous importance for the advancement of new optical communication systems. Erbium (1%) doped fiber amplifiers (EDFA's) or semiconductor lasers are currently being employed as near infrared light sources. Both devices, however, have inherent limitations due to their mode of operation. EDFA's employ an elaborate optical pumping scheme, whereas diode lasers have a strongly temperature dependent lasing wavelength. Novel light emitters based on erbium doped III-V semiconductors could overcome these limitations. Er doped semiconductors combine the convenience of electrical excitation with the excellent luminescence properties of Er(3+) ions. Electrically pumped, compact, and temperature stable optoelectronic devices are envisioned from this new class of luminescent materials. In this paper we discuss the potential of Er doped GaN for optoelectronic applications based on temperature dependent photoluminescence excitation studies.

Thaik, Myo↗

NASA NTRS2014

SOFIA Science Instruments: Commissioning, Upgrades and Future Opportunities

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is the world's largest airborne observatory, featuring a 2.5 meter telescope housed in the aft section of a Boeing 747sp aircraft. SOFIA's current instrument suite includes: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), a 5-40 μm dual band imager/grism spectrometer developed at Cornell University; HIPO (High-speed Imaging Photometer for Occultations), a 0.3-1.1 micron imager built by Lowell Observatory; FLITECAM (First Light Infrared Test Experiment CAMera), a 1-5 micron wide-field imager/grism spectrometer developed at UCLA; FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), a 42-210 micron IFU grating spectrograph completed by University Stuttgart; and EXES (Echelon-Cross- Echelle Spectrograph), a 5-28 micron high-resolution spectrometer being completed by UC Davis and NASA Ames. A second generation instrument, HAWC+ (Highresolution Airborne Wideband Camera), is a 50-240 micron imager being upgraded at JPL to add polarimetry and new detectors developed at GSFC. SOFIA will continually update its instrument suite with new instrumentation, technology demonstration experiments and upgrades to the existing instrument suite. This paper details instrument capabilities and status as well as plans for future instrumentation, including the call for proposals for 3rd generation SOFIA science instruments.

FLITECAM↗

NASA NTRS2011

Analysis of Co-Located MODIS and CALIPSO Observations Near Clouds

The purpose of this paper is to help researchers combine data from different satellites and thus gain new insights into two critical yet poorly understood aspects of anthropogenic climate change, aerosol-cloud interactions and aerosol radiative effects, For this, the paper explores whether cloud information from the Aqua satellite's MODIS instrument can help characterize systematic aerosol changes near clouds by refining earlier perceptions of these changes that were based on the CALIPSO satellite's CALIOP instrument. Similar to a radar but using visible and ncar-infrared light, CALIOP sends out laser pulses and provides aerosol and cloud information along a single line that tracks the satellite orbit by measuring the reflection of its pulses. In contrast, MODIS takes images of reflected sunlight and emitted infrared radiation at several wavelengths, and covers wide areas around the satellite track. This paper analyzes a year-long global dataset covering all ice-free oceans, and finds that MODIS can greatly help the interpretation of CALIOP observations, especially by detecting clouds that lie outside the line observed by CALlPSO. The paper also finds that complications such as differences in view direction or clouds drifting in the 72 seconds that elapse between MODIS and CALIOP observations have only a minor impact. The study also finds that MODIS data helps refine but does not qualitatively alter perceptions of the systematic aerosol changes that were detected in earlier studies using only CALIOP data. It then proposes a statistical approach to account for clouds lying outside the CALIOP track even when MODIS cannot as reliably detect low clouds, for example at night or over ice. Finally, the paper finds that, because of variations in cloud amount and type, the typical distance to clouds in maritime clear areas varies with season and location. The overall median distance to clouds in maritime clear areas around 4-5 km. The fact that half of all clear areas is closer than 5 km to clouds implies that pronounced near-cloud changes in aerosol properties have significant implications for overall clear-sky characteristics, including the radiative impact of aerosols.

Varnai, Tamas↗

NASA NTRS2009

Light-Driven Polymeric Bimorph Actuators

Light-driven polymeric bimorph actuators are being developed as alternatives to prior electrically and optically driven actuators in advanced, highly miniaturized devices and systems exemplified by microelectromechanical systems (MEMS), micro-electro-optical-mechanical systems (MEOMS), and sensor and actuator arrays in smart structures. These light-driven polymeric bimorph actuators are intended to satisfy a need for actuators that (1) in comparison with the prior actuators, are simpler and less power-hungry; (2) can be driven by low-power visible or mid-infrared light delivered through conventional optic fibers; and (3) are suitable for integration with optical sensors and multiple actuators of the same or different type. The immediate predecessors of the present light-driven polymeric bimorph actuators are bimorph actuators that exploit a photorestrictive effect in lead lanthanum zirconate titanate (PLZT) ceramics. The disadvantages of the PLZT-based actuators are that (1) it is difficult to shape the PLZT ceramics, which are hard and brittle; (2) for actuation, it is necessary to use ultraviolet light (wavelengths < 380 nm), which must be generated by use of high-power, high-pressure arc lamps or lasers; (3) it is difficult to deliver sufficient ultraviolet light through conventional optical fibers because of significant losses in the fibers; (4) the response times of the PLZT actuators are of the order of several seconds unacceptably long for typical applications; and (5) the maximum mechanical displacements of the PLZT-based actuators are limited to those characterized by low strains beyond which PLZT ceramics disintegrate because of their brittleness. The basic element of a light-driven bimorph actuator of the present developmental type is a cantilever beam comprising two layers, at least one of which is a polymer that exhibits a photomechanical effect (see figure). The dominant mechanism of the photomechanical effect is a photothermal one: absorption of light energy causes heating, which, in turn, causes thermal expansion.

Adamovsky, Gregory↗

NASA NTRS2006

Measuring Extended Structure in Stars Using the Keck Interferometer Nuller

The Keck Interferometer Nuller is designed to detect faint off-axis mid-infrared light a few tens to a few hundreds of milliarcseconds from a bright central star. The starlight is suppressed by destructive combination along the long (85 m) baseline, which produces a fringe spacing of 25 mas at a wavelength of 10 m, with the central null crossing the position of the star. The strong, variable mid-infrared background is subtracted using interferometric phase chopping along the short (5 m) baseline. This paper presents an overview of the observing and data reduction strategies used to produce a calibrated measurement of the off-axis light. During the observations, the instrument cycles rapidly through several calibration and measurement steps, in order to monitor and stabilize the phases of the fringes produced by the various baselines, and to derive the fringe intensity at the constructive peak and destructive null along the long baseline. The data analysis involves removing biases and coherently demodulating the short-baseline fringe with the long-baseline fringe tuned to alternate between constructive and destructive phases, combining the results of many measurements to improve the sensitivity, and estimating the part of the null leakage signal which is associated with the finite angular size of the central star. Comparison of the results of null measurements on science target and calibrator stars permits the instrumental leakage - the "system null leakage" - to be removed and the off-axis light to be measured.

nulling interferometry↗

NASA NTRS1988

SN 1987A - Out on the tail

The expected light curve of Supernova 1987A is calculated for the next 10 yr based solely upon energy input from radioactive decay of Co-56 and Co-57. During the third year, energy input from Co-57 begins to dominate. How the bolometric (ultraviolet-optical-infrared) light curve deviates from that given by 100 percent deposition of the gamma-rays is a measure of the mixing that has gone on in the supernova. Current measurements favor a mixed model. The radioactive light curve decreases beneath 10 to the 39th ergs/s at an age of about 900 days, by which time the neutron star remnant should have made its presence known.

Pinto, Philip A.↗