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ODell, S. L.

Publications and source records attributed to ODell, S. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Status of ART-XC/SRG Instrument

Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in March 2016 from Baikonur, by a Zenit rocket with a Fregat booster and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes - a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules. The NASA Marshall Space Flight Center (MSFC) is fabricating the flight mirror modules for the ART-XC/SRG. Each mirror module will be aligned with a focal plane CdTe double-sided strip detectors which will operate over the energy range of 6-30 keV, with an angular resolution of less than 1′, a field of view of approximately 34′ and an expected energy resolution of about 10 percent at 14 keV.

Pavlinsky, M.↗
NASA NTRS2012

The Marshall Space Flight Center Development of Mirror Modules for the ART-XC Instrument aboard the Spectrum-Roentgen-Gamma Mission

The Marshall Space Flight Center (MSFC) is developing x-ray mirror modules for the ART-XC instrument on board the Spectrum-Roentgen Gamma Mission under a Reimbursable Agreement between NASA and the Russian Space Research Institute (IKI.) ART-XC will consist of seven co-aligned x-ray mirror modules with seven corresponding CdTe focal plane detectors. Currently, four of the modules are being fabricated by the Marshall Space Flight Center (MSFC.) Each MSFC module consist of 28 nested Ni/Co thin shells giving an effective area of 65 sq cm at 8 keV, response out to 30 keV, and an angular resolution of 45 arcsec or better HPD. Delivery of these modules to the IKI is scheduled for summer 2013. We present a status of the ART x-ray modules development at the MSFC.

Gubarev, Mikhail V.↗
NASA NTRS2012

The Marshall Space Flight Center Development of Mirror Modules for the ART-XC Ins1rument Aboard the Spectrum-Roentgen-Gamma Mission

The Spectrum-Rontgen-Gamma (SRG) mission is a Russian-German X-ray astrophysical observatory that carries two co-aligned and complementary X-ray telescope systems. The primary instrument is the German-led extended ROentgen Survey with an Imaging Telescope Array (eROSITA), a 7-module X-ray telescope system that covers the energy range from 0.2-12 keV. The complementary instrument is the Russian-led Astronomical Roentgen Telescope -- X-ray Concentrator (ART-XC or ART), a 7-module X-ray telescope system that provides higher energy coverage, up to 30 keV (with limited sensitivity above 12 keV).

Gubarev, M.↗
NASA NTRS2012

The ART-XC Instrument on Board the SRG Mission

Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in 2014 from Baikonur, by a Zenit rocket with a Fregat booster and placed in a 6-month-period halo orbit around L2. The scientific payload consists of two independent telescopes . a soft-x-ray survey instrument, eROSITA, being provided by Germany and a medium-x-ray-energy survey instrument ART-XC being developed by Russia. ART-XC will consist of seven independent, but co-aligned, telescope modules with seven corresponding cadmium-telluride focal plane detectors. Each will operate over the approximate energy range of 6- 30 keV, with an angular resolution of <1 ', a field of view of ~30 ' and an energy resolution about 10% at 14 keV. The NASA Marshall Space Flight Center (MSFC) will fabricate some of the mirror modules, to complement others fabricated by VNIIEF in Russia.

Pavlinksy, M.↗
NASA NTRS2012

Using ACIS on the Chandra X-ray Observatory as a Particle Radiation Monitor II

The Advanced CCD Imaging Spectrometer is an instrument on the Chandra X-ray Observatory. CCDs are vulnerable to radiation damage, particularly by soft protons in the radiation belts and solar storms. The Chandra team has implemented procedures to protect ACIS during high-radiation events including autonomous protection triggered by an on-board radiation monitor. Elevated temperatures have reduced the effectiveness of the on-board monitor. The ACIS team has developed an algorithm which uses data from the CCDs themselves to detect periods of high radiation and a flight software patch to apply this algorithm is currently active on-board the instrument. In this paper, we explore the ACIS response to particle radiation through comparisons to a number of external measures of the radiation environment. We hope to better understand the efficiency of the algorithm as a function of the flux and spectrum of the particles and the time-profile of the radiation event.

Grant, C. E.↗
NASA NTRS2011

High Angular Resolution and Lightweight X-Ray Optics for Astronomical Missions

X-ray optics with both high angular resolution and lightweight is essential for further progress in x-ray astronomy. High angular resolution is important in avoiding source confusion and reducing background to enable the observation of the most distant objects of the early Universe. It is also important in enabling the use of gratings to achieve high spectral resolution to study, among other things, the myriad plasmas that exist in planetary, stellar, galactic environments, as well as interplanetary, inter-stellar, and inter-galactic media. Lightweight is important for further increase in effective photon collection area, because x-ray observations must take place on space platforms and the amount of mass that can be launched into space has always been very limited and is expected to continue to be very limited. This paper describes an x-ray optics development program and reports on its status that meets these two requirements. The objective of this program is to enable Explorer type missions in the near term and to enable flagship missions in the long term.

Zhang, W. W.↗
NASA NTRS2007

The Prospects for X-ray Polarimetry and its Potential use for Understanding Neutron Stars

We review the state of the art for measuring the X-ray polarization of neutron stars. We discuss how valuable precision measurements of the degree and position angle of polarization as a function of energy and, where relevant, of pulse phase, would provide deeper insight into the details of the emission mechanisms. We then review the current state of instrumentation and its potential for obtaining relevant data. Finally, we conclude our discussion with some opinions as to future directions.

Weisskopf, M. C.↗
NASA NTRS2004

X-Ray Vision

We are fabricating optics for the hard-x-ray region using electroless nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently stable and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics (nickel has a relatively high density of 8.9 g/cu cm), and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength nickel alloys that permit very thin shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these and other hard-x-ray optics will be reviewed.

Ramsey, B. D.↗
NASA NTRS2003

Development of a Prototype Nickel Optic for the Constellation-X Hard-X-Ray Telescope

The Constellation-X mission, planned for launch in 2011, will feature an array of hard-x ray telescopes with a total collecting area goal of 1500 square centimeters at 40 keV. Various technologies are currently being investigated for the optics of these telescopes including multilayer-coated Eletroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the promise of good angular resolution and enhanced instrument sensitivity. The challenge for this process is to meet a relatively tight weight budget with a relatively dense material (rho nickel = 9 grams per cubic centimeters.) To demonstrate the viability of the ENR process we are fabricating a prototype HXT mirror module to be tested against a competing segmented-glass-shell optic. The ENR prototype will consist of 5 shells of diameters from 150 mm to 280 mm and of 426 mm total length. To meet the stringent weight budget for Con-X, the shells will be only 150 micron thick. The innermost of these will be coated with Iridium, while the remainder will be coated with graded-density multilayers. Mandrels for these shells are currently under fabrication (Jan 03), with the first shells scheduled for production in February 03. A tentative date of late Summer has been set for prototype testing. Issues currently being addressed are the control of stresses in the multiplayer coating and ways of mitigating their effects on the figure of the necessarily thin shells. Also, the fabrication, handling and mounting of these shells without inducing permanent figure distortions. A full status report on the prototype optic will be presented along with test results as available.

Basso, S.↗
NASA NTRS2002

The Development of Hard-X-Ray Optics at MSFC

We are fabricating optics for the hard-x-ray region using electroless nickel replication. The attraction of this process, which has been widely used elsewhere, is that the resulting full shell optics are inherently table and thus can have very good angular resolution. The challenge with this process is to develop lightweight optics (nickel has a relatively high density of 8.9 g / cu cm), and to keep down the costs of mandrel fabrication. We accomplished the former through the development of high-strength nickel alloys that permit very thin shells without fabrication- and handling-induced deformations. For the latter, we have utilized inexpensive grinding and diamond turning to figure the mandrels and then purpose-built polishing machines to finish the surface. In-house plating tanks and a simple water-bath separation system complete the process. To date we have built shells ranging in size from 5 cm diameter to 50 cm, and with thickness down to 100 micron. For our HERO (high energy replicated optics) balloon program, we are fabricating over 200 iridium-coated shells, 250 microns thick, for hard-x-ray imaging up to 75 keV. Early test results on these have indicated half-power-diameters of 15 arcsec. The status of these and other hard-x-ray optics will be reviewed.

Ramsey, Brian D.↗
NASA NTRS2001

HERO: Program Status and Fist Images from a Balloon-Borne Focusing Hard-X-ray Telescope

HERO is a balloon payload featuring shallow-graze angle replicated optics for hard-x-ray imaging. When completed, the instrument will offer unprecedented sensitivity in the hard-x-ray region, giving thousands of sources to choose from for detailed study on long flights. A recent proof-of-concept flight captured the first hard-x-ray focused images of the Crab Nebula, Cygnus X-1 and GRS 1915+105. Full details of the HERO program are presented, including the design and performance of the optics, the detectors and the gondola. Results from the recent proving flight are discussed together with expected future performance when the full science payload is completed.

Ramsey, B. D.↗
NASA NTRS2000

Measurements with the Chandra X-ray Observatory's Flight Contamination Monitor

NASA's Chandra X-ray Observatory includes a Flight Contamination Monitor (FCM), a system of 16 radioactive calibration sources mounted to the inside of the Observatory's forward contamination cover. The purpose of the FCM is to verify the ground-to-orbit transfer of the Chandra flux scale, through comparison of data acquired during the ground calibration with those obtained in orbit, immediately prior to opening the Observatory's sun-shade door. Here we report results of these measurements., which place limits on the change in the mirror-detector system response and, hence, on any accumulation of molecular contamination on the mirrors' iridium-coated surfaces between the two sets of measurements.

Elsner, R. F.↗
NASA NTRS2000

Modeling Chandra Space Environment

This paper describes the development of an environmental risk-mitigation tool for the Chandra X-ray Observatory's Advanced CCD Imaging Spectrometer (ACIS). Because exposure to 100-200 keV protons appears to have degraded the front-illuminated CCD's charge transfer inefficiency (CTI), an accurate tool for predicting encounters with magnetospheric regions rich in these particles is required. We implement standard models to predict bow-shock, magnetopause, and plasma-sheet boundaries. Using these models and solar-wind databases compiled from IMP-8 and ACE measurements, we then calculate the probability that Chandra is located in one of these regions, along with predicted particle flux, to arrive at appropriate safing times for the ACIS detector. Finally, we validate this tool by comparing the model's boundary-crossing and proton flux predictions with measurements from Chandra's on-board particle detector and with data from other spacecraft operating in the Earth's magnetosphere.

Blackwell, W. C.↗
NASA NTRS2000

Development of Constellation-X Optics Technologies at MSFC

One of the major technological challenges for the Constellation X-ray Mission is the development of light-weight, high-resolution, grazing-incidence optics. NASA's Marshall Space Flight Center is developing and evaluating candidate technologies, based upon full-shell replication off precision mandrels. Here we report on recent progress in meeting the weight and imaging-performance requirements, using very thin, high- strength electroformed nickel alloys, In addition, we briefly describe MSFC's optics fabrication, metrology, and x-ray test facilities.

Ramsey, B. D.↗
NASA NTRS2000

Ion Transmission to the Focal Plane of the Chandra X-Ray Observatory

The severe degradation in spectrometric performance observed by the AXAF CCD Imaging Spectrometer (ACIS) instrument on-board the Chandra X-ray Observatory (CXO) was associated with a sharp increase in charge transfer inefficiency combined with relatively constant dark current. It was also observed that damage occurred only during passage through the earth's radiation belts, and only when ACIS remained in the focal plane during the passage. Subsequent measurements and analyses support the conjecture that the damaging radiation entered through the Observatory's High-Resolution Mirror Assembly (HRMA) aperture. A mechanism whereby low energy magnetospheric protons and/or heavier ions are scattered through the HRMA and reach the focal plane with just enough energy to stop in the CCD's charge transfer region currently provides a reasonably consistent explanation of all observed phenomena. In this paper, we will describe analyses which support this conclusion. Simulations using standard ion transmission codes were used to generate a bi-directional response function (BDRF) for the mirror surfaces and transmission through the various path elements. The BDRF was convolved with the geometry via ray-trace. Damage estimates using measured proton fluence and ground measurements of ACIS- type CCD damage vs. proton energy will be presented and compared with observed on- orbit damage.

Kolodziejczak, J. J.↗
NASA NTRS2000

The Chandra X-Ray Observatory: First Year of Operation

The Chandra X-ray Observatory - formerly, the Advanced X-ray Astrophysics Facility (AXAF) - has now joined the Hubble Space Telescope and the Compton Gamma-Ray Observatory, as the third of NASA's "Great Observatories". Chandra provides unprecedented arcsecond imaging and spectrometric imaging and high-resolution dispersive spectroscopy, to address a large range of topics in x-ray astronomy and astrophysics. Here we provide an overview of the Observatory, its operation, and results obtained during its first year of operation.

Weisskopf, M. C.↗
NASA NTRS2000

New Alloys for Electroformed Replicated X-Ray Optics

The process of electroforming x-ray mirror shells off a superpolished mandrel has been widely used. The recently launched XMM mission is a good example of this, containing 174 such mirror shells of diameters ranging from 0.3-0.7 m and thicknesses of 0.47-1.07 mm. To continue to utilize this technique for the next generation of x-ray observatories, where ever-larger collecting areas will be required within the constraints of tight weight budgets, demands that new alloys be developed that can withstand the large stresses imposed on very thin shells by the replication and handling processes. Towards this end, we began a development program in late 1997 to produce a high-strength alloy suitable for electroforming very thin high-resolution x-ray optics. The requirements for this task are quite severe; not only must the electroformed deposit be very strong, it must also have extremely low residual stresses to prevent serious figure distortions in large thin-walled shells. Further, the electroforming must be performed at near room temperature, as large temperature changes will modify the figure of the mandrel, in an environment that is not corrosive for the mandrel. The figure of merit for the strength of the electroformed deposit is its Precision Elastic Limit (PEL). This is a measure of permanent strain, at the few parts per million level, under applied stress. Pure nickel is very ductile and will permanently deform, at the parts-per-million level under loads of a few x 10(exp 7) Pa. These stresses are easily exceeded when thin-walled shells (150 micron thick) are replicated. Our goal was to develop an alloy an order of magnitude stronger than this. We will present the results of our development program, showing the evolution of our plating baths through to our present 'glassy' nickel alloy that satisfies the goals above. For each we will show the electroforming characteristics of the bath and the PEL measurements for the resulting alloys. We estimate the ultimate limit on shell thickness and mass for x-ray mirrors produced in these baths.

Engelhaupt, D.↗