Meeting highest performance requirements for lowest price and mass for the M1 segment support unit for E-ELT

The largest optical telescope in the world will be the E-ELT. Its primary mirror will be 42m in diameter. This mirror will consist of 984 hexagonal segments that are all individually supported. Each mirror will be controlled in six DOF while local shaping of the segments is provided by so called warping harnesses. These will correct for focus, astigmatism and trefoil. Hence a mirror with an extreme diameter to thickness ratio of almost 30 is obtained. Its support structure must guarantee a maximum surface form error of 30 nm rms independent of the segment attitude. Furthermore its stiffness to mass ratio must allow natural frequencies of 50Hz or higher to obtain sufficient bandwidth for the actuators that control the piston and tip/tilt of the segment. Designing such structure is a challenge that has been successfully completed. Three prototypes have been built and are about to be delivered to ESO. This paper discusses the main performance requirements and how they could be transferred into an elegant structure design. Furthermore an overview will be given on the main performance parameters in order to see whether the present design can be further optimized. © 2010 SPIE

The ESA GAIA mission ; Designing in Silicon Carbide and related issues

TNO is developing the Basic Angle Monitoring Opto-Mechanical Assembly for the GAIA mission of ESA, a space telescope that will create a map of the universe including distant stars and planets. GAIA is being built by EADS Astrium and scheduled for launch in 2011. Due to its stability and hardness properties, Silicon Carbide has been chosen for the structure, payload mirrors and most components of GAIA. The Basic Angle Monitoring subsystem was developed by TNO and is a metrology system for monitoring the angle between the two GAIA telescopes. With the Basic Angle Monitoring an Optical Path Difference as small as 1.5 picometers RMS can be measured. During the design phase of the Basic Angle Monitoring subsystem, TNO also developed solutions for ultra stable mounting of non-Silicon Carbide optical components. These components have to withstand launch with preservation of the alignment and retain optical properties from ambient to 100 K in vacuum. The manufacturing of off-axis Silicon Carbide mirrors of the Basic Angle Monitoring down to nm-level represented another challenge. A comprehensive program was conducted on SiC manufacturing of freeform optics. Status: the Basic Angle Monitoring has past the Critical Design Review

SPICA/SAFARI fourier transform spectrometer mechanism evolutionary design

TNO, together with its partners, have designed a cryogenic scanning mechanism for use in the SAFARI Fourier Transform Spectrometer (FTS) on board of the SPICA mission. SPICA is one of the M-class missions competing to be launched in ESA's Cosmic Vision Programme in 2022. JAXA leads the development of the SPICA satellite and SRON is the prime investigator of the Safari instrument. The FTS scanning mechanism (FTSM) has to meet a 35 mm stroke requirement with an Optical Path Difference resolution of less then 15 nm and must fit in a small volume. It consists of two back-to-back roof-top mirrors mounted on a small carriage, which is moved using a magnetic bearing linear guiding system in combination with a magnetic linear motor serving as the OPD actuator. The FTSM will be used at cryogenic temperatures of 4 Kelvin inducing challenging requirements on the thermal power dissipation and heat leak. The magnetic bearing enables movements over a scanning stroke of 35.5 mm in a small volume. It supports the optics in a free-floating way with no friction, or other non-linearities, with sub-nanometer accuracy. This solution is based on the design of the breadboard ODL (Optical Delay Line) developed for the ESA Darwin mission and the MABE mechanism developed by Micromega Dynamics. During the last couple of years the initial design of the SAFARI instrument, as described in an earlier SPIE 2010 paper, was adapted by the SAFARI team in an evolutionary way to meet the changing requirements of the SPICA payload module. This presentation will focus on the evolution of the FTSM to meet these changing requirements. This work is supported by the Netherlands Space Office (NSO). © 2012 SPIE

The development of a breadboard Cryogenic Optical Delay Line for DARWIN

TNO has developed a compact BreadBoard (BB) cryogenic Optical Delay Line (ODL) for use in future space interferometry missions such as ESA's Darwin and NASA's TPF-I. The breadboard delay line is representative of a flight mechanism. The optical design is a two-mirror cat's-eye. A linear guiding system based on magnetic bearings provides frictionless and wear free operation with zero hysteresis. The delay line has a voice coil actuator for single stage Optical Path Difference (OPD) control. The verification program, including functional testing at 40K, has been completed succesfully

Cryogenic magnetic bearing scanning mechanism design for the SPICA/SAFARI Fourier Transform Spectrometer

TNO, together with its partners Micromega and SRON, have designed a cryogenic scanning mechanism for use in the SAFARI Fourier Transform Spectrometer (FTS) on board of the SPICA mission. The optics of the FTS scanning mechanism (FTSM) consists of two back-to-back cat's-eyes. The optics are mounted on a central "back-bone" tube which houses all the important mechatronic parts: the magnetic bearing linear guiding system, a magnetic linear motor serving as the OPD actuator, internal metrology with nanometer resolution, and a launch lock. A magnetic bearing is employed to enable a large scanning stroke in a small volume. It supports the optics in a freefloating way with no friction, or other non-linearities, enabling sub-nanometer accuracy within a single stage with a stroke of -4 mm to +31.5 mm. Because the FTSM will be used at cryogenic temperatures of 4 Kelvin, the main structure and optics are all constructed from 6061 Aluminum. The overall outside dimensions of the FTSM are: 393 × 130 × 125 mm, and the mass is 2.2 kg. © 2010 SPIE

Coevolution in management fashions: The case of self-managing teams in the Netherlands

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