Excerpts from solar sail concepts and applications

Material applicable to Mars missions are excerpted from an earlier study covering a broader range of applications of solar sails. The basic principles of solar sail operation are provided, and the implications on trajectories and mission are discussed briefly. Concepts of solar sails and interplanetary vehicles are described and discussed. Some of the important solar sail material considerations are presented and some selections criteria are provided

Experimental Tests of the New Paradigm for Laser Filamentation in Gases

Since their discovery in the mid-1990s, ultrafast laser filaments in gases have been described as products of a dynamic balance between Kerr self-focusing and defocusing by free electric charges that are generated via multi-photon ionization on the beam axis. This established paradigm has been recently challenged by a suggestion that the Kerr effect saturates and even changes sign at high intensity of light, and that this sign reversal, not free-charge defocusing, is the dominant mechanism responsible for the extended propagation of laser filaments. We report qualitative tests of the new theory based on electrical and optical measurements of plasma density in femtosecond laser filaments in air and argon. Our results consistently support the established paradigm.Comment: 4 pages, 4 figure

Impact of Recent Tax Stimulants on Modest Enterprises

The recession year 1958 found Congress in a mood to aid and encourage small business through more favorable tax treatment. The thrust of the ensuing legislation touched in varying degrees the whole life span of a modest enterprise, from organization through liquidation. The focus here, however, will be confined to a consideration of the practical impact of the recent statutory changes on the organizational and ordinary operational phases of such a business

Strengthening mental health care in Southern Malawi: contested meanings and the search for culturally embedded approaches

Mental health problems represent a significant burden of disability worldwide and there is mounting attention on how best to develop health care responses that are acceptable, effective and deliverable to scale. Alongside resource constraints, concerns have been expressed about the extent to which Western biomedical models of healthcare are transferable to other cultural settings, especially in the Global South. This integrative chapter introduces a body of published work describing a task-shifting initiative in Malawi to test the feasibility and acceptability of health surveillance assistants (HSAs) delivering culturally appropriate mental health interventions across one district. With the overall aim of strengthening HSAs’ care responses, the four papers describe structured evaluations of the pilot and scaled-up interventions, a qualitative study of stakeholder perspectives and experiences and a further historical and socio-cultural analysis of the key findings. The bespoke mental health training initiative, delivered to scale, led HSAs to offer assessment, advice, counselling, practical support and signposting for people in distress and their families. The initiative also demonstrated a vast reach within communities. However, pluralistic and negotiated beliefs concerning mental health and illness, and its place within the sociocultural space and community mores, were evident and revealed the rich indigenous cultural philosophy of umunthu underpinning HSAs’ work. Navigating between biomedical understandings of mental illness and traditional African understandings, the HSAs fashioned supportive interventions attuned to cultural norms under both the gaze and guise of biomedicine. While HSAs responded therapeutically and strengthened support for people in distress, their efforts to do so typify wider tensions over the dominance of particular knowledge systems, such as biomedicine. These findings add to evidence signalling the importance that mental health care initiatives are co-created with respect for communities’ historical and contemporary sociocultural contexts through establishing collaborative partnerships respectful of social justice and culturally negotiated meaning

The Infrared Imaging Spectrograph (IRIS) for TMT: Volume phase holographic grating performance testing and discussion

Maximizing the grating efficiency is a key goal for the first light instrument IRIS (Infrared Imaging Spectrograph) currently being designed to sample the diffraction limit of the TMT (Thirty Meter Telescope). Volume Phase Holographic (VPH) gratings have been shown to offer extremely high efficiencies that approach 100% for high line frequencies (i.e., 600 to 6000l/mm), which has been applicable for astronomical optical spectrographs. However, VPH gratings have been less exploited in the near-infrared, particularly for gratings that have lower line frequencies. Given their potential to offer high throughputs and low scattered light, VPH gratings are being explored for IRIS as a potential dispersing element in the spectrograph. Our team has procured near-infrared gratings from two separate vendors. We have two gratings with the specifications needed for IRIS current design: 1.51-1.82{\mu}m (H-band) to produce a spectral resolution of 4000 and 1.19- 1.37 {\mu}m (J-band) to produce a spectral resolution of 8000. The center wavelengths for each grating are 1.629{\mu}m and 1.27{\mu}m, and the groove densities are 177l/mm and 440l/mm for H-band R=4000 and J-band R=8000, respectively. We directly measure the efficiencies in the lab and find that the peak efficiencies of these two types of gratings are quite good with a peak efficiency of ~88% at the Bragg angle in both TM and TE modes at H-band, and 90.23% in TM mode, 79.91% in TE mode at J-band for the best vendor. We determine the drop in efficiency off the Bragg angle, with a 20-23% decrease in efficiency at H-band when 2.5 degree deviation from the Bragg angle, and 25%-28% decrease at J-band when 5{\deg} deviation from the Bragg angle.Comment: Proceedings of the SPIE, 9147-33

OMV Servicing Missions from Space Station

\u27!he Orbital Maneuvering Vehicle (OMV) will provide a means of bringing large observatories to the Space station for servicing and redeployment to their operating altitudes. However, there are many constraints which must be met in mission planning. \u27!he missions must be designed so that propellant consumption is within the usable allowance, but contingency operations can still be accomplished. \u27!he vehicle was designed specifically to accommodate such missions, with emphasis upon servicing the Hubble Space Telescope. \u27!he OMV has been designed for operations from the Shuttle Orbiter and the Space Station. It will readily accommodate basing at the Space Station and executing observatory retrieval and redeployment missions. Mission profiles have been designed which allow retrieval with contengency hold before descent, and which allow contengency return of the observatory if it fails to reactivate properly. This capability will be a major addition to the Space Transportation System and will increase the utility of the Space Station

The InfraRed Imaging Spectrograph (IRIS) for TMT: Reflective ruled diffraction grating performance testing and discussion

We present the efficiency of near-infrared reflective ruled diffraction gratings designed for the InfraRed Imaging Spectrograph (IRIS). IRIS is a first light, integral field spectrograph and imager for the Thirty Meter Telescope (TMT) and narrow field infrared adaptive optics system (NFIRAOS). We present our experimental setup and analysis of the efficiency of selected reflective diffraction gratings. These measurements are used as a comparison sample against selected candidate Volume Phase Holographic (VPH) gratings (see Chen et al., this conference). We investigate the efficiencies of five ruled gratings designed for IRIS from two separate vendors. Three of the gratings accept a bandpass of 1.19-1.37 {\mu}m (J band) with ideal spectral resolutions of R=4000 and R=8000, groove densities of 249 and 516 lines/mm, and blaze angles of 9.86 and 20.54 degrees, respectively. The other two gratings accept a bandpass of 1.51-1.82 {\mu}m (H Band) with an ideal spectral resolution of R=4000, groove density of 141 lines/mm, and blaze angle of 9.86{\deg}. We measure the efficiencies off blaze angle for all gratings and the efficiencies between the polarization transverse magnetic (TM) and transverse electric (TE) states. The peak reflective efficiencies are 98.90 +/- 3.36% (TM) and 84.99 +/- 2.74% (TM) for the H-band R=4000 and J-band R=4000 respectively. The peak reflective efficiency for the J-band R=8000 grating is 78.78 +/- 2.54% (TE). We find that these ruled gratings do not exhibit a wide dependency on incident angle within +/-3{\deg}. Our best-manufactured gratings were found to exhibit a dependency on the polarization state of the incident beam with a ~10-20% deviation, consistent with the theoretical efficiency predictions.Comment: Proceedings of the SPIE, 9147-34

BIM for the sub-surface : challenges

Most existing BIM 3D models show the ground as a grey amorphous mass, if it is shown at all. The ground is inherently more variable than other construction materials and, in an integrated multidisciplinary BIM project, it is important that this can be appropriately conveyed in order to avoid poor decision making