We describe first results from a new instrument-telescope configuration that combines all of the capabilities necessary to obtain high resolving power visible band spectra of diffuse targets from small aperture telescopes where significant observing time can be obtained. This instrument –Khayyam- is a tunable all-reflective spatial heterodyne spectrometer (SHS) that is mounted to a fixed focal plane shared by the 0.6m Coude auxiliary telescope and the 3m Shane telescope on Mt. Hamilton. Khayyam has an up to 78 arcmin input field of view, resolving power up to 176000, and a tunable bandpass from 350-700 nm. It is being field tested for initial use to study spatially extended solar system targets where high resolving power is necessary to separate multimodal signals, crowded molecular bands, and to sample low velocities (<10 km/s) and rapid temporal cadence is necessary to track physical evolution. Two of the best comet targets during next year is comet C/2011 L4 (PanSTARRS), and C/2011 F1 (LINEAR). Our goal is to sequentially measure isotopic ratios of 14N:15N and 12C:13C in CN, along with the production rate and the production rate ratios of varies daughter species, particularly C2, C3, NH2, OI, and CN, as a function of heliocentric distance and time.
Scattered solar and collisionally stimulated H Ly-α emission is a proven diagnostic for the study of the Sun, comets, the
interplanetary medium, planet atmospheres, and corona. Here we discuss the construction and testing of a narrow
bandpass instrument designed to observe H Ly-α emission at a resolving power of R~100,000 from targets with an
angular extent of ≤½ degree. The instrument is an all-reflective form of the spatial heterodyne spectrometer (SHS), a
self-scanning Fourier Transform Spectrometer. It will be incorporated into the focal plane of a suborbital telescope that
is scheduled for a March 2013 launch. Initial alignment and vibrational testing was performed with the instrument
aligned to a visible analog line. The results showed alignment stability under vibration, but revealed several
unacceptable resonances that have been corrected in the mechanical design.
Temperature and velocity-distribution remote-sensing of faint diffuse sources such as the interplanetary medium (IPM),
comets and planetary atmospheres, is an instrumental challenge that becomes more pronounced in the ultraviolet. All-reflective
Spatial-Heterodyne Spectrometers (SHS), an emerging new class of instruments that combines both high
étendue and high resolving power (greater than 105), are ideally suited to these types of observations. Their all-reflective
configuration and their self-compensating monolithic design enable them to operate under the tight tolerances of the
ultraviolet and to survive the rigors of space launch. An in-development sounding-rocket experiment, the Hydrogen
Polarimetric Explorer (HYPE), will merge an all-reflective SHS with a half-wave Brewster reflection polarimeter to
obtain the first interferometric polarimetry of an ultraviolet emission line source. Its initial flight will target the IPM at
the hydrogen Lyman-alpha transition (121.6nm). HYPE's novel optical configuration also combines several
improvements in reflective SHS design, including true zero-path interferometry, no aliasing, and one-dimensional
imaging. The optical layout and performance of the HYPE prototype will be described along with simulation results
from ray-tracing computations.
Ultraviolet astronomy is an important tool for the study of the interplanetary medium, comets, planetary upper atmospheres, and the near space environments planets and satellites. In addition to brightness distributions, emission line profiles offer insight into winds, atmospheric escape, energy balance, currents, and plasma properties. Unfortunately, the faintness of many target emissions and the volume limitations of small spacecraft and remote probes limit the opportunities for incorporating a high spectral resolution capability. An emerging technique to address this uses an all-reflective form of the spatial heterodyne spectrometer (SHS) that combines very high (R >105) spectral resolution and large étendue in a package small enough to fly as a component instrument on small spacecraft. The large étendue of SHS instruments makes them ideally suited for observations of extended, low surface brightness, isolated emission line sources, while their intrinsically high spectral resolution enables the study of the dynamical and spectral characteristics described above. We are developing three forms of the reflective SHS to observe single line shapes, multiple lines via bandpass scanning, and precision spectro-polarimetry. We describe the basic SHS approach, the three variations under development and their scientific potential for the exploration of the solar system and other faint extended targets.
Ultraviolet astronomy is an important tool for the study of the interplanetary medium and diffuse, angularly extended emissions in planetary/comet atmospheres and their near space environments. We describe a new technique for high étendue observations of emission lines at R > 105 with an all-reflective spatial heterodyne spectrometer and polarmetric sampling of these lines with an ultraviolet optimized waveplate-Brewster mirror combination. The resulting system is themo-mechanically stable, has light collecting power substantially greater than HST for extended emissions, despite having a volume of several x 10-3 m3. This makes the SHS polarimeter ideal for spacecraft applications. We describe the SHS and polarmetric optical techniques and provide a discussion of its planned development for studies of interplanetary hydrogen.
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