ALBERT

Description: This paper will describe the objectives of the Marshall Space Flight Center (MSFC) Solar Ultraviolet Magnetograph Investigation (SUMI) and the optical components that have been developed to meet those objectives. A sounding rocket payload is being developed to test the feasibility of magnetic field measurements in the Sun s transition region. This paper will review the scientific measurements that will be made by the SUMI sounding rocket program, and the optics have been optimized for simultaneous measurements of two magnetic lines formed in the transition region (CIV at 1550 A and MgII at 2800 A). Finally, this paper will concentrate on the polarization properties of the SUM1 polarimeter and toroidal varied-line-space gratings.

Description: A sounding rocket instrument consisting of two vacuum ultraviolet Fabry-Perot filters in series would allow high-spectral resolution over an extended field of view for solar observations of the transition region between the chromosphere and the corona.

Description: The characterization of the electromagnetic interaction for a solar sail in the solar wind environment and identification of viable charging mitigation strategies are critical solar sail mission design tasks. Spacecraft charging has important implications both for science applications and for lifetime and reliability issues of sail propulsion systems. To that end, surface charging calculations of a candidate 150-meter-class solar sail spacecraft for the 0.5 AU solar polar and 1.9 AU LI solar wind environments are performed. A model of the spacecraft with candidate materials having appropriate electrical properties is constructed using Object Toolkit. The spacecraft charging analysis is performed using Nascap-2k. the NASA/AFRL sponsored spacecraft charging analysis tool. Nominal and atypical solar wind environments appropriate for the 0.5 AU and 1.0 AU missions are used to establish current collection of solar wind ions and electrons. Finally, a geostationary orbit environment case is included to demonstrate a bounding example of extreme (negative) charging of a solar sail spacecraft. Results from the charging analyses demonstrate that minimal differential potentials (and resulting threat of electrostatic discharge) occur when the spacecraft is constructed entirely of conducting materials, as anticipated from standard guidelines for mitigation of spacecraft charging issues. Examples with dielectric materials exposed to the space environment exhibit differential potentials ranging from a few volts to extreme potentials in the kilovolt range.

Description: This paper will describe the objectives of the Marshall Space Flight Center (MSFC) Solar Ultraviolet Magnetograph Investigation (SUMI) and the unique optical components that have been developed to meet those objectives. A sounding rocket payload has been developed to test the feasibility of magnetic field measurements in the Sun's transition region. The optics have been optimized for simultaneous measurements of two magnetic sensitive lines formed in the transition region (CIV at 1550 A and MgII at 2800 A). This paper will concentrate on the polarization properties SUMI's toroidal varied-line-space (TVLS) gratings and its system level testing as we prepare to launch in the Summer of 2008.

Description: We present measurements of toroidal variable-line-space (TVLS) gratings for the Solar Ultraviolet Magnetograph Investigation (SUMI), currently being developed at the National Space Science and Technology Center (NSSTC). SUMI is a spectro-polarimeter designed to measure magnetic fields in the solar chromosphere by observing two UV emission lines sensitive to magnetic fields, the CIY line at 155nm and the MgII line at 280nm. The instrument uses a pair of TVLS gratings, to observe both linear polarizations simultaneously. Efficiency measurements were done on bare aluminum gratings and aluminum/MgF2 coated gratings, at both linear polarizations.

Description: Toroidal variable-line-space (VLS) gratings are an important factor in the design of an efficient VUV solar telescope that will measure the CIV (155nm) and MgII (280nm) emissions lines in the Sun's transition region. In 1983 Kita and Harada described spherical VLS gratings but the technology to commercially fabricate these devices is a recent development, especially for toroidal surfaces. This paper will describe why this technology is important in the development of the Solar Ultraviolet Magnetograph Investigation (SUMI) sounding rocket program (the good), the delays due to the conversion between the TVLS grating design and the optical fabrication (the bad), and finally the optical testing, alignment and tolerancing of the gratings (the ugly). The Solar Ultraviolet Magnetograph Investigation, SUMI, has been reported in several papers since this program began in 2000. The emphasis of this paper is to describe SUMI's Toroidal Variable-Line-Space (TVLS) gratings. These gratings help SUMI meet its scientific goals which require both high spectral resolution and high optical efficiency for magnetic field measurements in the vacuum ultraviolet wavelength band of the solar spectrum (the good). Unfortunately, the technology readiness level of these gratings has made their implementation difficult, especially for a sounding rocket payload (the bad). Therefore, this paper emphasizes the problems and solutions that were developed to use these gratings in SUMI (the ugly). Section 2 contains a short review of the scientific goals of SUMI and why this mission is important in the understanding of the 3D structure of the magnetic field on the Sun. The flight hardware that makes up the SUMI payload is described in Section 3 with emphasis on those components that affect the TVLS gratings. Section 4 emphasizes the alignment, testing and optical modeling that were developed to optimize the performance of these gratings.

Description: This paper describes the scientific goals of a sounding rocket program called the Solar Ultraviolet Magnetograph Investigation (SUMI), presents a brief description of the optics that were developed to meet those goals and discusses the spectral, spatial and polarization characteristics of SUMI's Toroidal Variable-Line-Space (TVLS) gratings; which are critical to SUMI's measurements of the magnetic field in the Sun's transition region.

Description: The condensation/sublimation front using a two dimensional model of the evolving solar system is investigated based on combined viscous and radiative heating. The snow line is shown to be a two-branched curve reflecting the competing effects of solar heating in the photosphere and internal heating at the center plane. The evolution of the icy region is described from a limited region early in the disk evolution to final positions near 1 AU. The snow line evolution predicted using two surface density models, a Hayashi minimum mass power law and an analytical solution of the nebula evolution equation. Possible effects of this dynamic motion on disk chemistry and organic molecule formation is also described.

Description: We report the discovery of energetic neutral hydrogen atoms emitted during the X9 solar event of December 5, 2006. Beginning ~1 hour following the onset of this E79 flare, the Low Energy Telescopes (LETs) on both the STEREO A and B spacecraft observed a sudden burst of 1.6 to 15 MeV protons beginning hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within 10 of the Sun, consistent with the measurement resolution. The derived emission profile at the Sun had onset and peak times remarkably similar to the GOES soft X-ray profile and continued for more than an hour. The observed arrival directions and energy spectrum argue strongly that the particle events less than 5 MeV were due to energetic neutral hydrogen atoms (ENAs). To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. Possible origins for the production of ENAs in a large solar event are considered. We conclude that the observed ENAs were most likely produced in the high corona and that charge-transfer reactions between accelerated protons and partially-stripped coronal ions are an important source of ENAs in solar events.

Description: Since the discovery of periodicity in the solar cycle, the historical record of sunspot number has been carefully examined, attempting to make predictions about the next cycle. Much emphasis has been on predicting the maximum amplitude and length of the next cycle. Because current space-based and suborbital instruments are designed to study active phenomena, there is considerable interest in estimating the length and depth of the current minimum. We have developed criteria for the definition of a minimum and applied it to the historical sunspot record starting in 1749. In doing so, we find that 1) the current minimum is not yet unusually long and 2) there is no obvious way of predicting when, using our definition, the current minimum may end. However, by grouping the data into 22- year cycles there is an interesting pattern of extended minima that recurs every fourth or fifth 22-year cycle. A preliminary comparison of this pattern with other records, suggests the possibility of a correlation between extended minima and lower levels of solar irradiance.