Multi-slit Spectrometer Research Articles

Earth observations from the Moon's surface: dependence on lunar libration

Abstract. Observing the Earth from the Moon's surface has important scientific advantages. The angular diameter of the Earth as seen from the Moon's surface is 1.8–2.0∘ (the angular size varies due to the change in the Earth–Moon distance). The libration of the Moon in latitude reaches an amplitude of 6.68∘ and has a main period of 27.21 d (or 653.1 h). The libration of the Moon in longitude, reaching an amplitude of 7.9∘, has a period of 27.55 d (or 661.3 h). This causes the center of the Earth to move in the Moon's sky in a rectangle measuring 13.4∘ × 15.8∘. The trajectory of the Earth's motion in this rectangle changes its shape within a period of 6 years. This apparent librational movement of the Earth in the Moon's sky complicates observations of the Earth. This paper proposes that this disadvantage be turned into an advantage and that a multi-slit spectrometer be placed on the Moon's surface on a fixed platform. The libration motion and the daily rotation of the Earth will act as a natural replacement for the scanning mechanism.

The Thirty-Meter Telescope: Science and Instrumentation for a Next-Generation Observatory

The Thirty-Meter Telescope international observatory will enable transformational observations over the full cosmic timeline all the way from the first luminous objects in the Universe to the planets and moons of our own solar system. To realize its full scientific potential, TMT will be equipped with a powerful suite of adaptive optics systems and science instruments. Three science instruments will be available at first light: an optical multi-object spectrometer, a near-infrared multi-slit spectrometer and a diffraction-limited near-infrared imager and integral field spectrometer. In addition to these three instruments, a diverse set of new instruments under study will bring additional workhorse capabilities to serve the science interests of a broad user community. The development of TMT instruments represents a large, long-term program that offers a wide range of opportunities to all TMT partners.

Wavelength Isolation Sequence Design

A recent paper by Jedwab and Wodlinger renewed interest in a problem of multislit spectrometer design first proposed by Golay in 1951 but subsequently forgotten. It is shown that Golay's formulation of the problem in terms of 0/1 binary sequences is unduly restrictive. By relaxing the restrictions, infinitely many spectrometer designs satisfying all the original physical criteria can be found. Three constructions for such spectrometer designs are presented, involving Golomb rulers and variants. These constructions explain all nontrivial examples involving at most 26 slits.

Static multislit dispersive optical spectrometer based on complementary Golay sequences

A high-transmission multislit spectrometer free of moving elements is described, the main parts of which are the multislit entrance aperture, collimator, dispersive element, objective, multichannel matrix detector, processor, and spectrum output device. The proposed instrument differs from the known analogs in that its operation is based on the use of complementary Golay sequences, which makes it possible to use a relatively simple multislit entrance aperture involving only four parallel horizontal rows of slits at an arbitrarily large length of these rows. In practice, this design provides a decrease in the level of optical losses on nontransparent bands separating the rows and simplifies manufacturing of the spectrometer.

Complementary Golay series in multislit dispersion optical spectroscopy

This paper proposes a new application of the complementary Golay series in multislit optical dispersion spectroscopy that differs from traditional dispersion optical spectroscopy in that it uses complex multislit apertures instead of ordinary slits in order to increase the speed. More precisely, based on the given series, new pairs of numerical series have been developed that have a single maximum of the correlation function and that can be used in multislit spectrometers to construct multislit apertures and to search for spectra. The series presented here differ from known analogs by greater simplicity for such a high speed. The possibility of implementing the proposed series is demonstrated using several spectrometer layouts as examples.

Science in the Era of TMT11Conference was held at the Arnold and Mabel Beckman Center of the National Academies in Irvine, California, 2007 July 23–25.

Science in the Era of TMT11Conference was held at the Arnold and Mabel Beckman Center of the National Academies in Irvine, California, 2007 July 23–25.

オフ・プレン・イーグル型多重スリット分光計

In case of the off-plane Eagle mounting multislit spectrometer, the perfect performance cannot be expected even with a properly designed holographic concave grating (HCG). Any imaging error of a HCG always leads to a decrease in the S/N of the spectrum. Such effects are discussed in detail and the following results are obtained. 1) A HCG which is designed to eliminate the astigmatism at 5890 Å in the first order can be effectively used over the wavelength range from 7000 Å down to the XUV region. 2) Full image width (FIW) depends on the position of point source, and not on the wavelength. 3) Therefore, any exit slot in the exit multislit mask has its own transmission factor (t-factor). 4) Taking the t-factor into account, the S/N of the spectrum obtained with our multislit spectrometer is found to be about 94% of that attainable with the ideal multislit spectrometer.

Golay-type Static Multi-slit Spectrometer

The factors which affect a static multi-slit spectrometer are discussed, and a simple method is presented for compensating for the variation of lateral magnification of the spectrometer. A description is also given of a Golay-type static multi-slit spectrometer which was constructed for the purpose of evaluating the effectiveness of our compensation method and the performance of the spectrometer for light sources of different types in the visible and the near-ultra-violet. The experimental results indicate that our compensation method provides a simple, yet very effective means of making a Golay-type static multi-slit spectrometer practicable in the visible and the near-ultra-violet.

Spectrometer with longitudinal dispersion

The publication covers a multi-slit spectrometer which makes use of the longitudinal dispersion characteristics of optical lenses. Slit function and resolution are being determined. The longitudinal spectrometer has approximately the same resolution as a conventional lateral spectrometer of the same dimensions, provided the slit widths of the first type of spectrometer are narrower by the aperture ratio than the slit widths of the latter type of spectrometer, whilst its radiant flux is far higher because of the slit multiplicity. The spectrometer can be realized in different versions. Contrary to the majority of known multi-slit spectrometers, it is insensitive to non-uniform illumination of the multi-slit plates. The fundamental operating characteristics of a longitudinal spectrometer have been proved experimentally by means of a simple breadboard set-up. Resolution obtained did not fully meet the theoretical value, as the technical set-up of the breadboard had not been optimized.

Sequential Encoding with Multislit Spectrometers

A new method for optically encoding the spectral output of multislit spectrometers is proposed. It is based on sequential measurements of the total intensity of light in combinations of selected spectral bands. The resulting encoded optical information is obtained as a set of simultaneous linear algebraic equations, and spectrum reconstruction is accomplished through the use of matrix inversion techniques. This encoding method avoids the problems associated with frequency transform encoding, because it is not based on the usual Fourier or Fresnel transforms. Rather, it makes use of the theory of simultaneous linear algebraic equations.