The ability to rapidly assess damage to military infrastructure after an attack is the object of ongoing research. In the case
of runways, sensor systems capable of detecting and locating craters, spall, unexploded ordinance, and debris are necessary
to quickly and efficiently deploy assets to restore a minimum airfield operating surface. We describe measurements
performed using two commercial, robotic scanning LiDAR systems during a round of testing at an airfield. The LiDARs
were used to acquire baseline data and to conduct scans after two rounds of demolition and placement of artifacts for the
entire runway. Configuration of the LiDAR systems was sub-optimal due to availability of only two platforms for
placement of sensors on the same side of the runway. Nevertheless, results prove that the spatial resolution, accuracy, and
cadence of the sensors is sufficient to develop point cloud representations of the runway sufficient to distinguish craters,
debris and most UXO. Location of a complementary set of sensors on the opposite side of the runway would alleviate the
observed shadowing, increase the density of the registered point cloud, and likely allow detection of smaller artifacts.
Importantly, the synoptic data acquired by these static LiDAR sensors is dense enough to allow registration (fusion) with
the smaller, denser, targeted point cloud data acquired at close range by unmanned aerial systems. The paper will also
discuss point cloud manipulation and 3D object recognition algorithms that the team is developing for automatic detection
and geolocation of damage and objects of interest.
A new, economical, lenslet-array-based imaging sensor design is proposed, simulated, and analyzed. In this investigation a bare lenslet array model is first developed in Code V®. The results show that, as expected, intolerable optical cross-talk is present in this simple system. This problem has been addressed in previous systems via the inclusion of a physical image separation layer. The alternative system proposed here to alleviate crosstalk involves the introduction of both polarizers and spectral filters. As a consequence this simple system design also provides spectro-polarimetric resolution. Simulations were developed in order to analyze the system performance of two designs. The simulation results were analyzed in terms of a measure of signal-to-noise ratio (SNR) and in terms of an en-squared energy that includes all subimages. The results show that a design employing only a few spectral filters suppresses crosstalk for objects of small angular extent but does not suppress crosstalk to a tolerable level for 2π steradian illumination, as evidenced by SNR less than one. However, the inclusion of more spectral filters results in a spectro-polarimetric thin imager design that suppresses crosstalk and provides finer spectral resolution without the inclusion of a signal separation layer.
The Marshall Grazing Incidence X-ray Spectrograph (MaGIXS) is a proposed sounding rocket experiment designed to observe
spatially resolved soft X-ray spectra of the solar corona for the first time. The instrument is a purely grazing-incidence
design, consisting of aWolter Type-1 sector telescope and a slit spectrograph. The telescope mirror is a monolithic Zerodur
mirror with both the parabolic and hyperbolic surfaces. The spectrograph comprises a pair of paraboloid mirrors acting as
a collimator and reimaging mirror, and a planar varied-line-space grating, with reflective surfaces operate at a graze angle
of 2 degrees. This produces a flat spectrum on a detector covering a wavelength range of 6-24Å (0.5-1.2 keV). The design
achieves 20 mÅ spectral resolution (10 mÅ /pixel) and 5 arcsec spatial resolution (2.5 arcsec / pixel) over an 8-arcminute
long slit. The spectrograph is currently being fabricated as a laboratory prototype. A flight candidate telescope mirror is
also under development.
This paper will describe a new Extreme Ultraviolet (EUV) test facility that is being developed at the Marshall Space
Flight Center (MSFC) to test EUV telescopes. Two flight programs, Hi-C, the high resolution coronal imager (a
sounding rocket program), and SUVI, the Solar Ultraviolet Imager (GOES-R), set the requirements for this new facility.
This paper will discuss those requirements, the EUV source characteristics, the wavelength resolution that is expected
and the vacuum chambers (Stray Light Facility, Xray Calibration Facility and the NSSTC EUV test chamber) where this
facility will be used.
We present the methods and results for the figure testing and spectral calibration of the narrow- and wide-band etalons
for the Improved Solar Observing Optical Network's dual-etalon tunable imaging filters. The ISOON system comprises a
distributed network of ground-based patrol telescopes that gather full-disk data for the monitoring of solar activity and
for the development of more reliable space weather models. The etalon figure testing consists mainly of testing the
cavity flatness and coating uniformity of each etalon. For this testing a series of exposures is taken as the etalon is tuned
through a stable spectral line and a full-aperture line profile correlation method is employed to map the variations in the
effective cavity thickness. Calibration of the etalons includes absolute calibration of the cavity mean spacing change
corresponding to a controller step and calibration of plate parallelism and spacing settings for each spectral region of
interest. Developmental acceptance testing and calibration procedures were performed in a laboratory environment using
a HeNe laser source. A calibration method that uses illumination in the telluric lines is also described. This latter method
could be used to conduct calibration in the field without the use of an artificial light source.
The solar chromosphere is an important boundary, through which all of the plasma, magnetic fields and energy in the
corona and solar wind are supplied. Since the Zeeman splitting is typically smaller than the Doppler line broadening in
the chromosphere and transition region, it is not effective to explore weak magnetic fields. However, this is not the case
for the Hanle effect, when we have an instrument with high polarization sensitivity (~ 0.1%). "Chromospheric Lyman-
Alpha SpectroPolarimeter (CLASP)" is the sounding rocket experiment to detect linear polarization produced by the
Hanle effect in Lyman-alpha line (121.567 nm) and to make the first direct measurement of magnetic fields in the upper
chromosphere and lower transition region. To achieve the high sensitivity of ~ 0.1% within a rocket flight (5 minutes) in
Lyman-alpha line, which is easily absorbed by materials, we design the optical system mainly with reflections. The
CLASP consists of a classical Cassegrain telescope, a polarimeter and a spectrometer. The polarimeter consists of a
rotating 1/2-wave plate and two reflecting polarization analyzers. One of the analyzer also works as a polarization beam
splitter to give us two orthogonal linear polarizations simultaneously. The CLASP is planned to be launched in 2014
We use the two-dimensional Chebyshev polynomials as the basis for decomposition of test data over rectangular apertures, particularly for anamorphic optics. This includes simple optics such as cylindrical lenses and mirrors as well as complex optics, such as aspheric cylindrical optics. The new basis set is strictly orthogonal over rectangles of arbitrary aspect ratio and they correspond well with the aberrations of systems containing such type of optics. An example is given that applies the new basis set to study the surface figure error of a cylindrical Schmidt corrector plate. It is not only an excellent fitting basis but also can be used to flag misalignment errors that are critical to fabrication.
We describe an evolutionary algorithm for the design of an imaging triple-étalon Fabry-Perót interferometer (MFPI), which gives a solution to the multidimensional minimization process through a stochastic search method. The interactions between design variables (the étalon reflectances, interétalon ghost attenuator transmittances, and spacing ratios) are complex, resulting in a fitness landscape that is pitted with local optima. Traditional least-squares and gradient descent algorithms are not useful in such a situation. Instead, we employ a method called evolution strategies in which several preliminary designs are randomly generated subject to constraints. These designs are combined in pairs to produce offspring designs. The offspring population is mutated randomly, and only the fittest designs of the combined population are passed to the next iteration of the evolutionary process. We discuss the evolution strategies method itself, as well as its application to the specific problem of the design of an incoherently coupled triple-étalon interferometer intended for use as a focal plane instrument in the planned National Solar Observatory's Advanced Technology Solar Telescope (NSO's ATST). The algorithm converges quickly to a reasonable design that is well within the constraints imposed on the design variables, and which fulfills all resolution, signal-to-noise, throughput, and parasitic band suppression requirements.
We present four preliminary designs for a telecentric optical train supporting the Advanced Technology Solar Telescope (ATST) multiple Fabry-Pérot interferometer (MFPI), which is to be used as an imaging spectrometer and imaging spectropolarimeter. The point of departure for all three designs is the F/40 telecentric image at the Coudé focus of the ATST. The first design, representing the high-spectral-resolution mode of operation, produces an intermediate F/300 telecentric image within the triple étalon system and a 34-arcsec field of view (FOV). The second design, intermediate between high- and low-spectral-resolution modes of operation, produces an intermediate F/150 telecentric image at the étalons and a 1.1-arcmin FOV. The third and fourth designs each represent a low-resolution mode of operation, producing an F/82 telecentric image at the étalons and a 2-arcmin FOV. Each design results in good telecentricity and image quality. Departures from telecentricity at the intermediate image plane cause field-dependent shifts of the bandpass peak, which are negligible compared to the bandpass FWHM. The root mean square (rms) geometric spot sizes at the final image plane fit well within the area of a camera pixel, which is itself in accordance with the Nyquist criterion, half the width of the 28-µm-wide resolution element (as determined from the diffraction limit of the ATST). For each configuration, we also examine the impact that the Beckers effect (the pupil apodization caused by the angle-dependent amplitude transmittance of the MFPI) has on the image quality of the MFPI instrument.
This paper will describe the evolution of the Marshall Space Flight Center's (MSFC) electro-optical polarimeter with emphasis on the field-of-view characteristics of the KD*P modulator. Understanding those characteristics was essential to the success of the MSFC solar vector magnetograph. The paper will show how the field-of-view errors of KD*P look similar to the linear polarization patterns seen in simple sunspots and why the placement of the KD*P in a collimated beam was essential in separating the instrumental polarization from the solar signal. Finally, this paper will describe a modulator design which minimizes those field-of-view errors.
The successful augmentation of NASA's X-Ray Cryogenic Facility (XRCF) at the Marshall Space Flight Center (MSFC) to an optical metrology testing facility for the Sub-scale Beryllium Mirror Demonstrator (SBMD) and NGST Mirror Sub-scale Demonstrator (NMSD) programs required significant modifications and enhancements to achieve reliable data. In addition to building and integrating both a helium shroud and a rugged, stable platform to support a wavefront sensor, a custom sensor suite was assembled and integrated to meet the test requirements. The metrology suite consisted of a high-resolution Shack-Hartmann sensor, a point diffraction interferometer, a point spread function camera, and a radius of curvature measuring device.
The evolution from the SBMD and NMSD tests to the Advanced Mirror System Demonstrator (AMSD) program is less dramatic in some ways, such as the reutilization of the existing helium shroud and sensor support structure. However, significant modifications were required to meet the AMSD program's more stringent test requirements and conditions resulting in a substantial overhaul of the sensor suite and test plan. This paper will discuss the instrumentation changes made for AMSD, including the interferometer selection and null optics. The error budget for the tests will be presented using modeling and experimental data. We will show how the facility is ready to meet the test requirements.