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Optics
The instrument will be an efficient NIR multi-object spectrograph which will work at cryogenic temperatures of
less than 77 K. As LUCIFER is designed as a multi-mode instrument for seeing limited as well as for diffractionlimited
conditions, the following observing modes are provided:
- Direct imaging over a 4x4 arcmin2 FOV (seeing limited)
- Longslit spectroscopy (seeing and diffraction limited)
- Multi-object spectroscopy with slit masks (seeing limited)
- Diffraction-limited imaging over a 0.5x0.5 arcmin2 field FOV
- add-on capability for an integral field unit (IFU) spectroscopy and imaging with OH-avoidance
| Mode |
Seeing Limited | Diffraction Limited | |
|---|---|---|---|
| Camera | N3.75 | N1.8 | N30 |
| FOV | 4 x 4 arcmin | 4 x 4 arcmin | 0.5 x 0.5 arcmin |
| fColl | 1500 mm | 1500 mm | 1500 mm |
| fCam | 375 mm | 180 mm | 3000 mm |
| NCam | 3.75 | 1.80 | 30 |
| feff | 30940 mm | 14850 mm | 247540 mm |
| Scale | 0.12 arcsec/pixel | 0.25 arcsec/pixel | 0.015 arcsec/pixel |
| Beam diameter | 102 mm | 102 mm | 102 mm |
| Slit length | up to 4 arcmin | up to 4 arcmin | <=0.5 arcmin |
| Rlim | 10000 (0.24 arcsec slit) | 5000 (0.50 arcsec slit) | |
| FSR (K band) | 0.22 microns | 0.46 microns | |
| Rlim (K) | 28200 (0.10 arcsec slit) | ||
| Rlim (H) | 28200 (0.10 arcsec slit) | ||
| Rlim (J) | 37100 (0.08 arcsec slit) | ||
| Parameter | Imaging | Spectroscopy |
|---|---|---|
Scale |
0.25 arcsec/pixel | 0.25 arcsec/pixel |
| FOV | 4 x 4 arcmin^2 | 4 x 3 arcmin^2 |
| Resolution | 500...5000 | |
| Comments | aquisition |
full band coverage Longslit and MOS |
Scale |
0.12 arcsec/pixel | 0.12 arcsec/pixel |
| FOV | 4 x 4 arcmin^2 | 4 x 3 arcmin^2 |
| Resolution | 1000....10000 | |
| Comments | broad and narrow band | Longslit and MOS |
Scale |
0.015 arcsec/pixel | 0.015 arcsec/pixel |
| FOV | 0.5 x 0.5 arcmin^2 | 0.5 x 0.5 arcmin^2 |
| Resolution | 4000....40000 | |
| Comments | FOV limited by isoplanatism | Longslit |
The optomechanical components and the complete optics are three dimensionally folded, mounted in a very stiff truss cage and consists of the following units:
- Dichroitic window tilted by 15 degree
- Folded collimator which consists of a complex system of three lenses and four mirrors. Two of the mirrors will be motorized for the final optical alignment and for compensation of image movement on the detector. The collimator produces a pupil image where a mirror/grating-turret with cold stop is placed.
- Mirror/grating-turret with three gratings and one mirror, driven by a cryogenic PHYTRON stepper-motor. The position of each optical element will be detected via microswitches and can be fixed with a snap-in mechanism. The mirror is mounted in a fixed position and the gratings can be tilted by +/- 5
- Camera wheel with three cameras (N1.8, N3.75 and N30) mounted on a common base plate in a pivoted bearing. Additionally to the three camera positions a fourth safety position will be used during MOS mask exchanges and movements of the mask-handling robot. For the rotation drive a cryogenic PHYTRON stepper-motor will be used with a modified belt drive. In this case the belt is replaced by a thin steel cable. The lenses of the different cameras are integrated in individual camera tubes. Two of the cameras are using additional field lenses which are connected with spacers to the base-plate. These field lenses are placed directly in front of the detector. The double filter wheel rotates in the gap between field lens and camera tube.
- The double filter wheel consists of two individual wheels which holds up to 15 filters each, and is driven by a cryogenic PHYTRON stepper-motor. For reduction of it's diameter all filters are placed in inclined mountings. The positioning of the filters is realized with snap-in mechanisms, using the same principle like the grating unit.
- Detector mount and focus drive.
An atmospheric dispersion corrector, a NIR tip-tilt sensor and a slitviewer will be inserted in front of the telesope focal plane which is located 150 mm inside the instrument. The slitviewer and the NIR tip-tilt sensor were not part of our original offer and up to now the financing of four additional detectors (2 PICNIC arrays and 2 HAWAII I-chips) is not solved. However the design work has been carried out by the LUCIFER group for these components. Up to now most of the optomechanical components and drive mechanisms for the 1st LUCIFER instrument are built.