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NASA NTRS2009

Mid-Infrared Reflectance Imaging of Thermal-Barrier Coatings

An apparatus for mid-infrared reflectance imaging has been developed as means of inspecting for subsurface damage in thermal-barrier coatings (TBCs). The apparatus is designed, more specifically, for imaging the progression of buried delamination cracks in plasma-sprayed yttria-stabilized zirconia coatings on turbine-engine components. Progression of TBC delamination occurs by the formation of buried cracks that grow and then link together to produce eventual TBC spallation. The mid-infrared reflectance imaging system described here makes it possible to see delamination progression that is invisible to the unaided eye, and therefore give sufficiently advanced warning before delamination progression adversely affects engine performance and safety. The apparatus (see figure) includes a commercial mid-infrared camera that contains a liquid-nitrogen-cooled focal plane indium antimonide photodetector array, and imaging is restricted by a narrow bandpass centered at wavelength of 4 microns. This narrow wavelength range centered at 4 microns was chosen because (1) it enables avoidance of interfering absorptions by atmospheric OH and CO2 at 3 and 4.25 microns, respectively; and (2) the coating material exhibits maximum transparency in this wavelength range. Delamination contrast is produced in the midinfrared reflectance images because the introduction of cracks into the TBC creates an internal TBC/air-gap interface with a high diffuse reflectivity of 0.81, resulting in substantially higher reflectance of mid-infrared radiation in regions that contain buried delamination cracks. The camera is positioned a short distance (.12 cm) from the specimen. The mid-infrared illumination is generated by a 50-watt silicon carbide source positioned to the side of the mid-infrared camera, and the illumination is collimated and reflected onto the specimen by a 6.35-cm-diameter off-axis paraboloidal mirror. Because the collected images are of a steady-state reflected intensity (in contrast to the transient thermal response observed in infrared thermography), collection times can be lengthened to whatever extent needed to achieve desired signal-to-noise ratios. Each image is digitized, and the resulting data are processed in several steps to obtain a true mid-infrared reflectance image. The raw image includes thermal radiation emitted by the specimen in addition to the desired reflected radiation. The thermal-radiation contribution is eliminated by subtracting the image obtained with the illumination off from the image obtained with the illumination on. A flat-field correction is then made to remove the effects of non-uniformities in the illumination level and pixel-to-pixel variations in sensitivity. This correction is performed by normalizing to an image of a standard object that has a known reflectance at a wavelength of 4 microns. After correction, each pixel value is proportional to the reflectance (at a wavelength of 4-microns) at the corresponding location on the specimen. Mid-infrared reflectance imaging of specimens that were thermally cyc led for different numbers of cycles was performed and demonstrated t hat mid-infrared reflectance imaging was able to monitor the gradual delamination progression that occurs with continued thermal cycling . Reproducible values were obtained for the reflectance associated w ith an attached and fully delaminated TBC, so that intermediate refle ctance values could be interpreted to successfully predict the numbe r of thermal cycles to failure.

Edlridge, Jeffrey I.↗
NASA NTRS2000

The Stuff of Other Worlds

Extraterrestrial material eternally rains down on Earth. Meteorites flare in the night sky. Cosmic rays plow into Earth's atmosphere, creating invisible bursts of secondary particles. These processes began when the Earth formed in the primordial solar system and have continued ever since, indifferent to the exceedingly recent presence of human intelligence. For us to seek out stuff of other worlds, in contrast, takes a great deal of determined ingenuity. First we have to send a spacecraft somewhere else in the solar system. Indigenous material has to be collected and then brought back to Earth without exposure to conditions that might significantly alter it. The material must undergo meaningful scientific analysis. Most important, part of the material is preserved intact for future investigations. Beginning with bringing back Moon rocks, and now moving onward in the form of new missions to capture the hot thin solar wind and cold thin atmosphere of comets, extraterrestrial sample return takes place on the cutting edge of scientific technology. Sample return is also the fulcrum of an energetic debate about how to do planetary science missions. Scientists and engineers are debating whether to rely on remote sensing and in situ analysis, or to plan missions to undertake sample return. The latter is definitely more expensive on a per mission basis, and is usually technologically more challenging. But for an initially high investment of money and technology, bringing the stuff of other worlds back to Earth yields an incomparable return in scientific results.

Stansbery, EIleen K.↗
NASA NTRS2011

What Dominates the Coronal Emission Spectrum During the Cycle of Impulsive Heating and Cooling?

The smoking gun of small-scale, impulsive events heating the solar corona is expected to be the presence of a hot ( > 5 MK) plasma component. Evidence for this has been scarce, but has gradually begun to accumulate due to recent studies designed to constrain the high temperature part of the emission measure distribution. However, the detected hot component is often weaker than models predict and this is due in part to the common modeling assumption that the ionization balance remains in equilibrium. The launch of the latest generation of space-based observing instrumentation aboard Hinode and the Solar Dynamics Observatory (SDO) has brought the matter of the ionization state of the plasma firmly to the forefront. It is timely to consider exactly what emission current instruments would detect when observing a corona heated impulsively on small-scales by nanoflares. Only after we understand the full effects of nonequilibrium ionization can we draw meaningful conclusions about the plasma that is (or is not) present. We have therefore performed a series of hydrodynamic simulations for a variety of different nanoflare properties and initial conditions. Our study has led to several key conclusions. 1. Deviations from equilibrium are greatest for short-duration nanoflares at low initial coronal densities. 2. Hot emission lines are the most affected and are suppressed sometimes to the point of being invisible. 3. The emission detected in all of the SDO-AIA channels is generally dominated by warm, over-dense, cooling plasma. 4. It is difficult not to create coronal loops that emit strongly at 1.5 MK and in the range 2 to 5 MK, which are the most commonly observed kind, for a broad range of nanoflare scenarios. 5. The Fe XV (284.16 ) emission in most of our models is about 10 times brighter than the Ca XVII (192.82 ) emission, consistent with observations. Our overarching conclusion is that small-scale, impulsive heating inducing a nonequilibrium ionization state leads to predictions for observable quantities that are entirely consistent with what is actually observed.

Bradshaw, Stephen J.↗
NASA NTRS2011

The Impact of Nonequilibrium Ionization on SDO/AIA and Hinode/EIS Observations of Impulsively Heated Plasmas

Most plasma diagnostics assume the emitting material is in a state of ionization equilibrium. For example, the AIA temperature response functions have been derived on this basis. The assumption is reasonable whenever the plasma is evolving slowly or is very dense, but these are not the conditions that apply during impulsive heating events. It is now widely believed that many coronal loops are bundles of unresolved strands that are heated quasi-randomly by nanoflares. Full blown flares are thought to have similar sub-structure. We have studied the importance of nonequilibrium effects in these circumstances by modeling nanoflare-heated loops and simulating their observation by AIA and the EIS spectrometer on Hinode. We find that the intensities of hot emission lines can be highly suppressed and that the net emission from the loop tends to be dominated by strands that have entered a slow cooling phase, well after the impulsive energy release has ended. The hottest strands are relatively invisible, both because they are tenuous and because they cool rapidly by thermal conduction. Thus, AIA channels that are normally thought of as being sensitive to hot plasma, such 131 and 94, are in fact frequently not able to detect the hot plasma that is present. The magnitude of the effect is case dependent. Great care must be exercised when using the standard temperature response functions in situations where nonequilibrium ionization is likely to be important.

Klimchuk, James A.↗
NASA NTRS2009

Heliophysics: The Solar and Space Physics of a New Era. Recommended Roadmap for Science and Technology 2009-2030

Our planet is immersed in a seemingly invisible yet exotic and inherently dangerous environment. Above the protective cocoon of Earth's lower atmosphere is a plasma soup composed of electrified and magnetized matter entwined with penetrating radiation and energetic particles. The Earth's magnetic field interacts with the Sun's outer atmosphere to create this extraordinary environment.

Heliophysics↗
NASA NTRS2005

Jet Propulsion Laboratory: Annual Report 2004

Once or twice in an age, a year comes along that the historians proclaim as an Annus Mirabilis - a year of wonders. For the Jet Propulsion Laboratory, 2004 was just that sort of time. From beginning to end, it was a nonstop experience of wondrous events in space. Imagine that two robot rovers embark on cross-country rambles across Mars, scrutinizing rocks for signs of past water on the now-arid world. A flagship spacecraft brakes into orbit at Saturn to begin longterm surveillance of the ringed world, preparing to drop a sophisticated probe to the surface of its haze-shrouded largest moon. Another craft makes the closest-ever pass by the nucleus of a comet, collecting sample particles as it goes. Two new space telescopes peer into the depths of the universe far beyond our solar system, viewing stars, nebulas and galaxies in invisible light beyond the spectrum our eyes can see. A pair of instruments is lofted on a NASA Earth-orbiting satellite to monitor air quality and the protective layer of ozone blanketing our home planet. A small probe brings samples of the solar wind to Earth for in-depth study. While JPL was absorbed with all of these ventures on other worlds, NASA and the White House unveiled an ambitious new plan of space exploration. The Vision for Space Exploration announced in January foresees a program of robotic and astronaut missions leading to a human return to the Moon by 2020, and eventual crewed expeditions to Mars. The vision also calls for more robotic missions to the moons of the outer planets; spaceborne observatories that will search for Earth-like planets around other stars and explore the formation and evolution of the universe; and continued study of our home planet. In order to accomplish all of this, NASA must perfect many as-yet-uninvented technologies and space transportation capabilities. JPL has a great deal to bring to this vision. Robotic exploration of Mars will lead the way for missions that will carry women and men to the red planet. Our engineers and scientists are formulating spacecraft that could use nuclear power to enable exploration missions of the future. And even now we are designing formations of space telescopes that will capture family portraits of the planets around neighboring stars. Those are only some of the ways that the Laboratory is contributing to NASA's broader goals. During 2004, JPL made a distinctive contribution to agencywide initiatives in areas such as safety, NASA transformation, the agency's Internet portal and NASA's Explorer Schools programs. Years like 2004 pose a special challenge for us. It would be easy to say that this was a once-in-a-decade high point of mission activities, but I believe that this would miss an opportunity. We are fortunate to have many space projects in the works that have the promise of being just as exhilarating as the great mission successes that we celebrated this year. The challenge and opportunity for us now is to make every year like this one.

National Aeronautics and Space Administration (NAS↗
NASA NTRS2011

The Hazards of Our Star

The Sun's magnetic field permeates its atmosphere - ranging from the solar photosphere (the visible "surface") to the corona above. Think of this field as a collection of invisible rubber bands that are slowly stretched and twisted until they eventually reach a breaking point, When the field breaks, it releases a small amount of energy, known as a nanoflare. Millions of nanoflares occur every second, and the combined effect heats the solar corona to more than 1 million kelvins, hundreds of times hotter than the photosphere. The super-heated gas emits X-ray and ultraviolet radiation; Earth's upper atmosphere absorbs it, which changes our atmosphere's properties. This can disrupt communication, navigation, and surveillance systems, and also alter the orbits of satellites. On much larger scales, huge sections of the corona explosively erupt in coronal mass ejections (CMEs) and solar flares. CMEs directed toward Earth cause geomagnetic storms, which can wreck havoc on electrical power grids and produce widespread blackouts. Highly energetic particles can damage or even disable critical spacecraft components. Intense radiation from flares has the same effects as nanoflares, but to a greater degree. The need to understand how solar phenomena impact Earth has led to an important science field called space weather.

Klimchuk, James A.↗
NASA NTRS2012

Listen; There's a Hell of a Good Universe Next Door; Let's Go

Scientific research is key to our nation's technological and economic development. One can attempt to focus research toward specific applications, but science has a way of surprising us. Think for example of the "charge-couple device", which was originally invented for memory storage, but became the modern digital camera that is used everywhere from camera phones to the Hubble Space Telescope. Using digital cameras, Hubble has taken pictures that reach back 12 billion light-years into the past, when the Universe was only 1-2 billion years old. Such results would never have been possible with the film cameras Hubble was originally supposed to use. Over the past two decades, Hubble and other telescopes have shown us much about the Universe -- many of these results are shocking. Our galaxy is swarming with planets; most of the mass in the Universe is invisible; and our Universe is accelerating ever faster and faster for unknown reasons. Thus, we live in a "hell of a good universe", to quote e.e. cummings, that we fundamentally don't understand. This means that you, as young scientists, have many worlds to discover

Rigby, Jane R.↗
NASA NTRS2010

Electrostatic Evaluation of the ARES I FTS Antenna Materials

Surface resistivity and volume resistivity data show all the tested non-metallic materials of the Ares I FTS antenna assembly to be insulative. The external materials (White foam, phenolic) should be able to develop a large surface charge density upon tribocharging with ice crystal impingement. Dielectric breakdown tests on the FTS antenna housing materials show that each of the insulative materials are very resistive to electrical breakdown. The thicknesses of these materials in a nominal housing should protect the antenna from direct breakdown from external triboelectric charging potentials. Per data from the Air Force study, a maximum external electric potential in the range of 100kV can be developed on surfaces tribocharged by ice crystal impingement. Testing showed that under operational pressure ranges, this level of exterior voltage can result in a potential of about 6 kV induced on the electrically floating interior antenna vanes. Testing the vanes up to this voltage level showed that electrostatic discharges can occur between the electrically floating vanes and the center, grounded screw heads. Repeated tests with multiple invisible and visible discharges caused only superficial physical damage to the vanes. Fourier analysis of the discharge signals showed that the frequency range of credible discharges would not interfere with the nominal operation of the FTS antenna. However, due to the limited scope, short timetable, and limited funding of this study, a direct measurement of the triboelectric charge that could be generated on the Ares I antenna housing when the rocket traverses an ice cloud at supersonic speeds was not performed. Instead, data for the limited Air Force study [3] was used as input for our experiments. The Air Force data used was not collected with a sensor located to provide us with the best approximation at the geometry of the Ares I rocket, namely that of the windshield electrometer, because brush discharges to the metal frame of the windshield periodically depleted any charge accumulated. The configuration of the Ares I antenna assembly does not include any exposed metals in the vicinity and the windshield data could not be used. Since the windshield sensor data was unusable, we decided that the Patch 2 location would provide us with a rough approximation to the Ares I antenna configuration and would give us an indication of the possible charging levels that would develop. This was the data that we used in this study. Whether these charging levels would be of the same order of magnitude as the actual charges developed by the Ares I traversing a cloud with ice particles is at this point unknown. An actual experimental test, requiring the acquisition of additional instrumentation, is strongly advised before a final recommendation can be formulated regarding the safe levels of electrostatic charging on the antenna housing. Thus the results of this study should be considered to be preliminary.

Hogue, Michael D.↗
NASA NTRS2012

Cold Brown Dwarfs with WISE: Y Dwarfs and the Field Mass Function

Why study Brown Dwarf stars? They re the lowest mass byproducts of star formation.. They provide time capsules across the age of the Galaxy.. They show what low-T(sub eff) atmospheres look like.. They may be some of our closest neighbors in space..WISE is a 40cm Earth-orbiting telescope. There are 211 stars and only 33 brown dwarfs in this volume.. This means that stars outnumber brown dwarfs by a factor of 6:1 currently.. The number of brown dwarfs will continue to increase if:: (a) more nearby Y dwarf candidates are confirmed, or (b) our distances to known Y s are overestimated, or (c) there are colder BDs invisible to WISE..

stars↗
NASA NTRS2007

Effect of PdO on TiO(sub2) Loading on Chemochromic Detection of Hydrogen

Safety is always a concern in all applications that utilize hydrogen (H(sub2)) in one form or the other. Hydrogen leaks are invisible and odorless. In addition, blending odorants or additives into hydrogen in a manner similar to natural gas is generally undesirable for certain applications including proton exchange membrane fuel cells. To facilitate detection of the location of hydrogen leaks, a special chemochromic H(sub2) sensing material that employs titania (Ti0(sub2)) supported palladium oxide (PdO) pigments encapsulated within a special silicone matrix has been developed at the Florida Solar Energy Center (FSEC). Several batches of PdO H(sub2) sensing pigments were synthesized using various Ti0(sub2) supports and their hydrogen detection activity determined. TEM and Particle size distribution analysis showed that smaller particles with hemispherical crystalline structure produced faster coloration kinetics when exposed to H(sub2) gas. However, uniformly distributed PdO particles on the Ti0(sub2) surface displayed greater color contrast, quantified by delta epsilon measurements. XRD analysis indicated that the crystalline phase of Ti0(sub2) had no effect on the chemochromic performance of the pigments in laboratory environment.

Mohajeri, Nahid↗
NASA NTRS2013

SynGenics Optimization System (SynOptSys)

The SynGenics Optimization System (SynOptSys) software application optimizes a product with respect to multiple, competing criteria using statistical Design of Experiments, Response-Surface Methodology, and the Desirability Optimization Methodology. The user is not required to be skilled in the underlying math; thus, SynOptSys can help designers and product developers overcome the barriers that prevent them from using powerful techniques to develop better pro ducts in a less costly manner. SynOpt-Sys is applicable to the design of any product or process with multiple criteria to meet, and at least two factors that influence achievement of those criteria. The user begins with a selected solution principle or system concept and a set of criteria that needs to be satisfied. The criteria may be expressed in terms of documented desirements or defined responses that the future system needs to achieve. Documented desirements can be imported into SynOptSys or created and documented directly within SynOptSys. Subsequent steps include identifying factors, specifying model order for each response, designing the experiment, running the experiment and gathering the data, analyzing the results, and determining the specifications for the optimized system. The user may also enter textual information as the project progresses. Data is easily edited within SynOptSys, and the software design enables full traceability within any step in the process, and facilitates reporting as needed. SynOptSys is unique in the way responses are defined and the nuances of the goodness associated with changes in response values for each of the responses of interest. The Desirability Optimization Methodology provides the basis of this novel feature. Moreover, this is a complete, guided design and optimization process tool with embedded math that can remain invisible to the user. It is not a standalone statistical program; it is a design and optimization system.

Ventresca, Carol↗
NASA NTRS2012

Dirtier Air from a Weaker Monsoon

The level of air pollution in China has much increased in the past decades, causing serious health problems. Among the main pollutants are aerosols, also known as particulate matter: tiny, invisible particles that are suspended in the air. These particles contribute substantially to premature mortality associated with cardiopulmonary diseases and lung cancer1. The increase of the aerosol level in China has been commonly attributed to the fast rise in pollutant emissions from the rapid economic development in the region. However, writing in Geophysical Research Letters, Jianlei Zhu and colleagues2 tell a different side of the story: using a chemical transport model and observation data, they show that the decadal scale weakening of the East Asian summer monsoon has also contributed to the increase of aerosol concentrations in China. The life cycle of atmospheric aerosols starts with its emission or formation in the atmosphere. Some aerosol components such as dust, soot and sea salt are emitted directly as particles to the atmosphere, but others are formed there by way of photochemical reactions. For example, sulphate and nitrate aerosols are produced from their respective precursor gases, sulphur dioxide and nitrogen oxides. Aerosol particles can be transported away from their source locations by winds or vertical motion of the air. Eventually, they are removed from the atmosphere by means of dry deposition and wet scavenging by precipitation. Measurements generally show that aerosol concentrations over Asia are lowest during the summer monsoon season3, because intense rainfall efficiently removes them from the air. The East Asian summer monsoon extends over subtropics and mid-latitudes. Its rainfall tends to concentrate in rain belts that stretch out for many thousands of kilometres and affect China, Korea, Japan and the surrounding area. Observations suggest that the East Asian summer monsoon circulation and precipitation have been in decline since the 1970s4. In particular, a weaker East Asian summer monsoon is characterized by weaker southerly or southwesterly winds, a deficit in rainfall over northern China and larger rainfalls in southern China. By contrast, when the East Asian summer monsoon is strong, the southerly winds and strong rainfalls extend to northern China. The decadal scale decline in the strength of the East Asian summer monsoon since the 1970s would imply an increase in aerosol concentrations in northern China, north of 28deg N, and a decrease in southern China if emissions were kept the same. One obvious reason for this direction of aerosol change is that the reduction of monsoon rainfall in northern China would cause less wet scavenging of aerosols by precipitation. Zhu et al.2 investigated this relationship between aerosol concentrations and the strength of the East Asian summer monsoon and showed that the two parameters have strong negative correlations: the summer aerosol concentrations near the surface over eastern China.

Chin, Mian↗
NASA NTRS2013

Onset of a Solar Filament Eruption Without a Slow-Rise Phase

We observe a filament eruption of 23 Jan 2012 using Atmospheric Imaging Array (AIA) data from the Solar Dynamics Observatory (SDO) satellite. Relatively cool emissions (193 Ang. channel) show a filament with a rise-toward-eruption trajectory that is relatively smooth, without a distinct, linearly-increasing "slow rise" followed by an abrupt "fast rise," as is often seen in other events. Detailed investigations of some of those two-phase events suggested that they were triggered by magnetic flux cancellation. Here however, observations of hotter emissions (335 Ang. channel) show an adjacent eruption, invisible in 193 Ang., occurred just prior to the filament's eruption start. We surmise that the hotter eruption destabilized the 193 Ang. filament, triggering its eruption onset. In this way, the filament's smooth eruption trajectory is indicative of a non-tether-cutting eruption-onset mechanism for the filament.

Knox, J. M.↗
NASA NTRS2013

Rapid Assessment of Contrast Sensitivity with Mobile Touch-screens

The availability of low-cost high-quality touch-screen displays in modern mobile devices has created opportunities for new approaches to routine visual measurements. Here we describe a novel method in which subjects use a finger swipe to indicate the transition from visible to invisible on a grating which is swept in both contrast and frequency. Because a single image can be swiped in about a second, it is practical to use a series of images to zoom in on particular ranges of contrast or frequency, both to increase the accuracy of the measurements and to obtain an estimate of the reliability of the subject. Sensitivities to chromatic and spatio-temporal modulations are easily measured using the same method. We will demonstrate a prototype for Apple Computer's iPad-iPod-iPhone family of devices, implemented using an open-source scripting environment known as QuIP (QUick Image Processing,

mobile devices↗
NASA NTRS2013

Book Review for Physics Today Ostriker and Mitton

Can anyone explain to a general audience how astronomers converged on such an astonishing story as the Big Bang, with large doses of Dark Matter and Dark Energy that only astronomers can “see” and most astronomers didn’t want? Might the reader believe the answer? And can the story keep the attention of professional physicists? The answer is yes for “Unraveling the Mysteries of the Invisible Universe” by Jeremiah Ostriker and Simon Mitton (Princeton University Press, 2013). Ostriker, a theorist, is one of the modern pioneers of the subject, and Mitton, a physicist-journalist, is an excellent storyteller as well.

Big Bang↗
NASA NTRS2011

The Necessity of Functional Analysis for Space Exploration Programs

As NASA moves toward expanded commercial spaceflight within its human exploration capability, there is increased emphasis on how to allocate responsibilities between government and commercial organizations to achieve coordinated program objectives. The practice of program-level functional analysis offers an opportunity for improved understanding of collaborative functions among heterogeneous partners. Functional analysis is contrasted with the physical analysis more commonly done at the program level, and is shown to provide theoretical performance, risk, and safety advantages beneficial to a government-commercial partnership. Performance advantages include faster convergence to acceptable system solutions; discovery of superior solutions with higher commonality, greater simplicity and greater parallelism by substituting functional for physical redundancy to achieve robustness and safety goals; and greater organizational cohesion around program objectives. Risk advantages include avoidance of rework by revelation of some kinds of architectural and contractual mismatches before systems are specified, designed, constructed, or integrated; avoidance of cost and schedule growth by more complete and precise specifications of cost and schedule estimates; and higher likelihood of successful integration on the first try. Safety advantages include effective delineation of must-work and must-not-work functions for integrated hazard analysis, the ability to formally demonstrate completeness of safety analyses, and provably correct logic for certification of flight readiness. The key mechanism for realizing these benefits is the development of an inter-functional architecture at the program level, which reveals relationships between top-level system requirements that would otherwise be invisible using only a physical architecture. This paper describes the advantages and pitfalls of functional analysis as a means of coordinating the actions of large heterogeneous organizations for space exploration programs.

program management↗
NASA NTRS2013

Scheduling Spitzer: The SIRPASS Story

NASA's Spitzer Space Telescope was launched on August 25, 2003 from Florida's Cape Canaveral Air Force Base. Drifting in a unique Earth-trailing orbit around the Sun, Spitzer sees an optically invisible universe dominated by dust and stars. Since 1997, the Spitzer Integrated Resource Planning and Scheduling System (SIRPASS) has helped produce spacecraft activity plans for the Spitzer Space Telescope. SIRPASS is used by members of the Observatory Planning and Scheduling Team to plan, schedule and sequence the Telescope from data made available to them from the science and engineering community. Because of the volume of data that needs to be scheduled, SIRPASS offers a variety of automated assistants to aid in this task. This paper will describe the functional elements of the SIRPASS software system -- emphasizing the role that automation plays in the system -- and will highlight lessons learned for the software developer from a decade of Spitzer Space Telescope operations experience.

flight systems↗