This paper describes the main thermo-mechanical design features and performances of the Co-Alignment Sensor (CAS) developed by LIDAX and CRISA under ESA program with AIRBUS Defence and Space as industry prime.
The Meteosat Third Generation (MTG) Programme is being realised through the well established and successful Cooperation between EUMETSAT and ESA. It will ensure the future continuity of MSG with the capabilities to enhance nowcasting, global and regional numerical weather prediction, climate and atmospheric chemistry monitoring data from Geostationary Orbit.
The instrumentation of many space missions requires operation in cryogenic temperatures. In all the cases, the use of
mechanisms in this environment is a matter of concern, especially when long lifetime is required.
With the aim of removing lifetime concerns and to benefit from the cryogenic environment, a cryogenic contactless
linear mechanism has been developed. It is based on the levitation of a permanent magnet over superconductor disks.
The mechanism has been designed, built, and tested to assess the performances of such technology.
The levitation system solves the mechanical contact problems due to cold-welding effects, material degradation by
fatigue, wearing, backlash, lubrication...etc, at cryogenic temperatures. In fact, the lower is the temperature the better the
superconductor levitation systems work.
The mechanism provides a wide stroke (18mm) and high resolution motion (1μm), where position is controlled by
changing the magnetic field of its environment using electric-magnets.
During the motion, the moving part of the mechanism levitates supported by the magnetic interaction with the high
temperature type II superconductors after reaching the superconductor state down to 90K.
This paper describes the results of the complete levitation system development, including extensive cryogenic testing to
measure optically the motion range, resolution, run-outs and rotations in order to characterize the levitation mechanism
and to verify its performance in a cryogenic environment.
IACATS is an atmospheric turbulence, stars and telescope simulator for the evaluation of on ground
telescopes instrumentation developed by INTA (optics) and LIDAX
(opto-mechanics) for the IAC (Instituto
de Astrofísica de Canarias).
Three telescopes have been simulated, matching the f number, focal plane, and optical interface of the
actual telescopes. An optical breadboard was designed and built containing the required opto-mechanics for
simulating the telescopes, and various levels of turbulence required.
In addition to the telescope simulator optics, a set of three phase plates have been procured and
conveniently combined in order to reproduce the atmospheric turbulence required by the IAC. A wave front
sensor has been also included in order to evaluate the deformation that the phase plates, or the simulated
turbulence, produce in the wave front coming from the illumination system and star simulator. Finally, a
specific illumination system was developed including different working wavelengths in order to fulfil the
requirements. The description of the illumination system itself has been done in a separate publication.. In the
following lines, the characteristics of the IACATS instrument as well as the results obtained from the AIV
(Assembly and Integration Verification) process are reported on.
A LED based illumination system in which five Galilean collimation systems have been used is reported
on. It is part of a turbulence simulator for the evaluation of on ground telescopes instrumentation developed
by INTA (optics) and LIDAX (opto-mechanics) for the IAC called IACATS. The illumination requirements
(some visible and infrared lines) allow the use of five different LEDs (red, green, blue and two infrareds). In
order to optimize the illumination level of each wavelength, a Galilean collimating optical configuration was
constructed for each wavelength channel.
The IACATS instrument simulates a scene consisting of a set of different binary stars simulating the
required angular separation between them, ant their spectral characteristics. As a result, a visible and infrared
multi-spectral illumination system has been integrated as a part of the turbulence simulator, and the features
(opto-mechanical) and illumination characteristics are described in the following lines.
The IACAT (IAC Atmosphere and Telescope) Simulator is an Optical Ground Support Equipment which simulates
atmospheric turbulence and reproduces the performance of three very different telescopes: GTC and WHT, located at
the Observatorio Del Roque de los Muchachos in La Palma (Canary Islands), and OGS which is located at the
Observatorio Del Teide in Tenerife (Canary Islands). Its mission is to provide Scientists with the same measurement
conditions as the real telescope but in a friendly laboratory environment, to assist in the development of new adaptive
optics methods based on FPGAs.
The most important telescope characteristics are simulated, such as f number, pupil size and position, magnification,
central obscuration, etc. Up to 13 stellar objects can be created, individually or as binary stars with specific angular
separations down to miliarcseconds.
For the atmosphere simulation, it allows the creation of three different turbulence layers concurrently with different
altitude and wind speed ranges.
The Cryogenic Submicron Linear Actuator (CSA) is a medium range (±5 mm) submicron resolution linear actuator
suitable to be used at cryogenic temperature (12K). The unit has been developed for fine positioning use.
The unit is based on classic motor-gear concept with nut and screw; different materials and lubrications have been tested
for the same design configuration to compare performances. Load capability is above 20N.
This paper describes main design features, results of different lubrications tested, tested performances, and main lessons
The CTU (Cryogenics Translation Unit) is a low range (±1 mm) high resolution (<50 nm) translation unit to be used at
cryogenic temperature (20K). The unit is a multipurpose device capable of fine closed loop positioning. This device can
be used as active element in IR Instrumentation for compensating thermo-elastic deformation moving optical elements
CTU motion system is based in thin flexures deformation to assure repeatability and moves in closed loop mode by
means of a fine linear actuator and a calibrated non contact capacitive sensor.
This paper describes main design features, how cryogenic testing of main requirements was carried out (including
methodologies used for calibration and submicron verification), tested performances, and main lesson learned during the
This paper describes the conceptual thermo-mechanical design of the MIXS (Mercury Imaging X-ray Spectrometer)
Focal Plane Assembly (FPA). This design is mainly driven by thermal requirements: The Detector is required to operate
below -45 ºC, while the Detector and proximity electronics dissipate more than 2 W, which the passive cooling system
can not handle at the required temperature.
In order to get rid of this cross-constraint, the Detector was separated from the Proximity electronics board, which in turn
has introduced a new dimension of mechanical requirements, as the 370+ bond wires that interconnect both are
extremely delicate and have a high thermal conductivity.
The MTS Folding Mirror Subsystem is part of the MIRI Telescope Simulator, which is an Optical Ground Support
Equipment for ESA MIRI (Medium Infrared Instrument) Qualification, in the frame of the James Webb Space
Telescope Program. The program prime contractor is INTA (Spanish National Aerospace Centre).
The Subsystem consists of four different mirrors assemblies to adapt the optical path to the available envelope; the
mirrors are placed between exit pupil and image plane with suitable orientation to reproduce specific chief ray deviation.
Remote adjustment for image compensation at cryogenic conditions is available for two mirror assemblies, by means of
two independent rotation mechanisms. A manual tip-tilt system is also provided for system adjusting at ambient
conditions in all four mirror assemblies.
The GTC Dome is entering into manufacture. Once the design has been frozen, it is time to expose the main features of the Dome and to exhibit the key aspects that will introduce an improvement on the GTC performance with respect to existing telescopes. The implementation of the natural ventilation for the telescope chamber, the use of an improved classical up-and-over shutter or the use of dome shell ventilation are described along the paper, as well as other features that have been laid-out to be absolutely ready to be `switch-on' after day one.
The maximum exploitation of the excellent astronomical quality of the `Roque de los Muchachos' Observatory is one of the most important design criteria for the GTC Project. The installations of the GTC are being designed in such a way as to minimize local seeing degradation while providing adequate support for the operation and maintenance of the facility. The paper will firstly describe the options that have been adopted as a solution for specific subsystems of the installations, such as: the dome, the auxiliary service areas or the thermal control, with special attention to the environmental conditions in the telescope chamber. Other subjects discussed are: the solutions proposed to minimize the possibility of turbulent surface-layer air negatively affecting astronomical observations; the minimization of wind-induced telescope vibrations and transmission of vibrations between the separate foundations of the buildings and the telescope pier through the ground; the guidelines to carry out the tasks of operating and maintaining the GTC and of course, the solutions for protection against adverse weather conditions.
Several options for the GTC (Gran Telescopio Canarias) installations have been evaluated. In particular, different dome types and distribution schemes for the support areas to be incorporated in the installation have been assessed. In order to select the dome type, a technical-economic study has been carried out, in which the most important parameters that determine the efficiency of the dome during its life- cycle have been qualitatively and in some cases quantitatively evaluated. This paper presents a compilation of the evaluation process followed for the selection of the GTC dome and the establishment of a general layout for the location of the support areas.