Marcus Jütte

LUCIFER1: performance results

LUCIFER1 is a NIR camera and spectrograph installed at the Large Binocular Telescope (LBT). Working in the wavelength range of 0.9-2.5micron, the instrument is designed for direct imaging and spectroscopy with 3 different cameras. A set of longslit masks as well as up to 23 user defined (MOS) masks are available. The set of user defined masks can be exchanged while the instrument is at operating temperature. Extensive tests have been done on the electro-mechanical functions, image motion due to flexure, optical quality, instrument software, calibration and especially on the multi-object spectroscopy. Also a detailed characterization of the instruments properties in the different observing modes has been carried out. Results are presented and compared to the specifications.

LUCIFER status report: summer 2008

LUCIFER is a NIR spectrograph and imager (wavelength range 0.9 to 2.5 micron) for the Large Binocular Telescope (LBT) on Mt. Graham, Arizona, working at cryogenic temperatures of less than 70K. Two instruments are built by a consortium of five German institutes and will be mounted at the bent Gregorian foci of the two individual telescope mirrors. Three exchangable cameras are available for imaging and spectroscopy: two of them are optimized for seeing-limited conditions, a third camera for the diffraction limited case will be used with the LBT adaptive secondary mirror working. Up to 33 exchangeable masks are available for longslit or multi-object spectroscopy (MOS) over the full field of view (FOV). Both MOS-units (LUCIFER 1 and LUCIFER 2) and the auxiliary cryostats together with the control electronics have been completed. The observational software-package is in its final stage of preparation. After the total integration of LUCIFER 1 extensive tests were done for all electro-mechanical functions and the verification of the instrument started. The results of the tests are presented in detail and are compared with the specifications.

The cryogenic MOS unit for LUCIFER

The LUCIFER MOS unit has been designed to exchange long-slit and multi-slit masks between two mask storage cabinets and the focal plane area. In combination with auxiliary cryostats, the MOS unit also permits the exchange of cold mask cabinets between LUCIFER and the auxiliary cryostats. Main functional components of the MOS unit are: a focal plane interface accepting the active mask, a mask handling unit transporting the masks between the focal plane mount and their storage locations, a stationary and an exchangeable cabinet holding 10 longslit and 23 multi-slit masks respectively, the translation drives for the exchangeable cabinet and the mask handling unit, and the mask locking unit securing the masks in their cabinets. For mask cabinet exchange, the LUCIFER cryostat as well as the auxiliary cryostats are equipped with 32 cm clear diameter gate valves. A test cryostat has been built to test all MOS unit functions at LN2 temperature. Most of the MOS unit components have been completed. System tests at ambient have started. First results are presented.

Lucifer VR: a virtual instrument for the LBT

Lucifer VR is a virtually realized instrument that was build in order to allow improved pre-integration software tests, training of observers as well as providing educational access. Beside testing the instrument hardware in combination with e.g. a telescope simulator, software tests need to be done. A virtual instrument closes the gap between regression tests and testing the control software with the integrated instrument. Lucifer VR allows much earlier tests and reduces the amount of time needed to combine the software with the hardware. By modeling the instrument in a simulator, motion times can be calculated very easily and the position of all instrument units can be traced. Especially when using complex mechanisms like a MOS unit a virtual instrument makes software development less time consuming. Lucifer VR consists of three parts; one for handling the communication, another to simulate the hardware and finally a part to visualize the whole instrument in three dimensions.

The LUCIFER control software

The successful roll-out of the control software for a complex NIR imager/spectrograph with MOS calls for flexible development strategies due to changing requirements during different phases of the project. A waterfall strategy used in the beginning has to change to a more iterative and agile process in the later stages. The choice of an appropriate program language as well as suitable software layout is crucial. For example the software has to accomplish multiple demands of different user groups, including a high level of flexibility for later changes and extensions. Different access levels to the instrument are mandatory to afford direct control mechanisms for lab operations and inspections of the instrument as well as tools to accomplish efficient science observations. Our hierarchical software structure with four layers of increasing abstract levels and the use of an object oriented language ideally supports these requirements. Here we describe our software architecture, the software development process, the different access levels and our commissioning experiences with LUCIFER 1.

Evolution and Star Formation of Dwarf Galaxies

We currently investigate several samples of dwarf galaxies (BCDs, Irr, dE) by means of a multi–wavlengths study including optical/NIR imaging as well as CO line and 1300µm dust continuum observations. Here we present the status of this project and preliminary results: i) From the mm data we find that the metallicity of the cold interstellar medium is normal in Sm types while heavy elements are significantly deficient in Im types. ii) The FIR colours of the various groups indicate that most Sm types have properties like normal giant spirals whereas most Im types resemble large starburst galaxies. iii) The optical and NIR studies corroborate previous suggestions that there are no morphological differences at different wavelengths. iv) The objects in our sample follow the NIR Tully–Fisher relation.