Max Planck Institute for Astronomy - Annual Report 2007

96 IV. Instrumental Developments and Projects
• Two gratings and a plane mirror are housed on the
grating exchange unit. The drive serves on the one
hand to change the grating or for the switch between
the camera mode and spectroscopy and, on the other
hand, to tune the central wavelength
• The two filter wheels provide room for 28 filters.
Currently 18 positions are occupied with filters. In
each wheel, an additional position is reserved for the
differential camera.
• In front of the camera wheel an additional lens can be
swiveled in to take an image of the pupil on the detector
with an f/1.8 camera. In this manner the alignment
of telescope and instrument can be controlled.
• The camera revolver houses the three f/1.8, f/3.75,
and f/30 camera systems. All three can be used both
as an imager and as a spectrograph. The f/30 camera
can also be used as a differential methane band camera
while the f/1.8 also serves with a fore-lens to take
images of the pupil.
• By correcting the focusing by up to 5 mm, differences
in the optic filter thickness can be offset.
The Mask Exchange Mechanism
Multi-object spectroscopy will likely be the most used
mode on Lucifer. Both Lucifer devices are equipped
with exchange loaders for the slit masks. Ten long-slit
and field masks are available as standard equipment. In
addition, 23 multi-slit masks (Mos masks) can be ex-
Fig. IV.1.6: Fan-out board and detector array in the test cryostat
during the first test of the detector.
Fig. IV.1.7: Lucifer on the telescope simulator. On the reverse
side, the flange for exchanging the mask loaders can be seen.
The cryostat was temporarily cabled and the detector is in
operation.
changed with the help of a cryogenic robot. The robot
guides the current focal mask back to its spot in the loader,
searches for the selected mask in the loader, and
brings it to the focal plane. The loader with 23 Mos
masks can be exchanged during the day as described
above (Fig. IV.1.5). The complex device for loader exchange
at low temperatures (Fig. IV.1.5) significantly
improves Lucifer’s observational readiness: Although
the process must take place during the day, this avoids
a warm-up cycle that would render Lucifer unusable
for six days.
The first Mos unit has already been finished and has
been tested successfully in a normal operating environment.
The second unit is currently being assembled at the
MPE for delivery to the MPIA in January 2008.
Read-out and Control Technology
The instrument’s control technology comprises the following
components which are housed in a temperatureregulated
rack: voltage supply, overvoltage protection
and instrument fuse; temperature regulator for the rack
and the detector; motor control electronics; and instrument
communications unit. The rack with its control
electronics will be fixed to the telescope and is connected
with the instrument via the cable twister. Read operation
and Mos control electronics are piggybacked to the
reverse side of the cryostat. 32 channels are read out
together with four additional reference channels. Tests
of the read-out noise revealed around 1 ADU per readout
which corresponds to about one third of the detector
read-out noise. In total, three read-out electronics systems
are being built, one for each of the two Lucifers
and one as an additional spare part.