Multi Object Universal Spectrograph for Extragalactic Research
MOUSER Over View
The design of a new generation fast spectrograph MOUSER (Multi Object Universal Spectrograph for Extragalactic Research) to be installed at the 6 m telescope is proposed. The MOUSER is a multipurpose multimode device, intended for spectral and photometric study of faint extended and stellar-like objects in the spectral range 0.37-1.11mm.
Inspection of the observing schedule of the 6 m telescope shows that over 40% of the calender time is allotted to the programmes of broad-band CCD photometry and low and moderate resolution spectroscopy using the fast long-slit spectrograph, multipupil and multiobject spectrographs. The objective of the project is to devise a multipurpose instrument which will realize the stated procedures and be highly efficient in spectral observations of faint objects.
The spectrograph will be operated in six fundamental modes:
- photometric observations in broad and narrow spectral bands with a 6'x6' field of view and an image scale of 0".30/pixel;
- spectral observations with a long slit, 5.5' high, resolving power R~9500;
- spectral multiobject observations with a mask, R~10003000;
- two-dimensional spectroscopy with the lens array, the field of view 17"x 30" and 15"x15" with image sampling 1".0 and 0".5,
respectively, the number of independent spectral elements is 5001000, with R~9500;
- two-dimensional spectropolarimetry with the lens array with the 17"x 14" field of view, R~10003000;
- spectrophotometry in narrow spectral intervals with the scanning Fabry-Perot etalon, resolution R~15000.
Experience of over 15 years of investigations at the 6 m telescope in this field and the emergence of undated detectors allows the basic requirements to such a device to be stated:
- automatic guiding and compensation for telescope vibrations;
- automatic focusing during exposure;
- optics transmission in the range 0.33 -1.2mm;
- maximum quantum efficiency;
- the optics quality must ensure a point spread function of no more than 2 detector pixels throughout the spectral range;
- the calibration system must comply with the condition of telecentrism in all modes of operation;
- remote control and monitoring.
The spectrograph is to be installed on the field rotator of the 6 m telescope prime focus without a standard field corrector. A CCD chip of 2048x2048 pixels (EEV CCD42-40) developed at SAO RAS is used as the detector.
The optical scheme of the spectrograph relies on home-made types of glass, all the optics are spherical. The overall dimensions of the prime focus cage and the necessity of providing a high aperture ratio of the spectrograph at a maximum possible size of the collimated beam are taken into account. To achieve maximum quantum efficiency for a wide spectral range all optical surfaces are allowed to be coated by a untireflecting layers. The optical and ray diagram of the instrument with designations of main instrument blocks is shown in Fig.1.
The MOUSER is built up from a number of individual units mounted in a rigid construction with allowance made for it to be installed in the prime focus cage. The change of the different observational modes of the instrument is performed by turn-over of the diagonal mirrors, inserting of masks into the focal plane or by change of the diffraction grating or the mirror within a few minutes.
To compensate for the image tremor at frequences between 0.02 Hz and 5 Hz, which is caused by the telescope mounting vibration, a special corrector is proposed. The tilting afocal aplanatic lens incorporated in the MOUSER shifts the image within a required range at very small tilts. Such a lens also plays the part of the field corrector, correcting coma and astigmatism of the main mirror and providing flat field in the entrance focal plane of the spectrograph.
The spectrograph is controlled from the remote HOST computer, connected through the link interface to an IPC (Industrial Personal Computer) of the spectrograph, which is equipped by all necessary program drivers and interface cards for performing of commands, taken from the HOST computer. The HOST PC is provided with specialized software integrated into the supervising system of the experiment, which enables on-line control of the spectrograph, CCD detector and telescope.
By the end of 1997 the designing of the spectrograph was basically completed, principal optical elements and part of mechanical units were manufactured.
V. L. Afanasiev, Eh. B. Gazhur, S. N. Dodonov, S. V. Markelov, E. I. Perepelitsin
Optical diagram of the MOUSER .
MOUSER Discription (russian)