In order to make small infrared cloud measuring device can be well in a wide temperature range and day-night environment, a design idea using catadioptric infrared panoramic imaging optical system and simple mechanical structure for realizing observation clode under all-weather conditions was proposed. Firstly, the optical system of cloud measuring device was designed. An easy-to-use numerical method was proposed to acquire the profile of a catadioptric mirror, which brought the property of equidistance projection and played the most important role in a catadioptric panoramic lens. Secondly, the mechanical structure was studied in detail. Overcoming the limitations of traditional primary mirror support structure, integrative design was used for refractor and mirror support structure. Lastly, temperature adaptability and modes of the mirror support structure were analyzed. Results show that the observation range of the cloud measuring device is wide and the structure is simple, the fundamental frequency of the structure is greater than 100 Hz, the surface precision of the system reflector reaches PV of λ/10 and RMS of λ/40under the load of temperature range - 40 ~ 60°C, it can meet the needs of existing meteorological observation.

Opto-mechanical design of small infrared cloud measuring device

With increasing size of the reflecting mirror apertures in telescopes, the lateral support is becoming more and more important. In order to find a setup satisfying the requirements for the TMT tertiary mirror, based on the classic three-point flexure support setup, a twelve-point lateral support setup was investigated its basic internal relations and properties were investigated. The virtual equivalent circle concept is then proposed to evaluate different potential setups. By studying the relationship between the virtual equivalent circle radius and the thermal deformation and resonant frequency, it can be concluded that a larger virtual equivalent circle radius results in a smaller the thermal deformation and a higher resonant frequency. Preliminary research results suggested that the TMT tertiary mirror surface figure error and thermal deformation requirements can easily be met. However, it was more difficult to obtain resonant frequencies higher than 15 Hz. Based on the virtual equivalent circle concept, the TMT tertiary mirror support setup was optimized, resulting in a resonant frequency of 17.7 Hz, which satisfies the requirements. The whiffletree lateral support setup can be applied to similar reflecting mirror support structures.

/pdf/kinematic-evaluation-of-the-whiffletree-lateral-support-4ywivx6vbp.pdf

Kinematic evaluation of the whiffletree lateral support setup and its application for the mirror support of the TMT tertiary mirror

In order to improve the dynamic rigidity of optical antennas of the laser communication system, a laser communication optical antenna with integrated optical hood is proposed. The integrated design of the primary mirror room and the hood was carried out, which improves the overall rigidity of the laser communication antenna and has the function of hood. The front surface of the primary mirror room is connected with disk type secondary mirror support to reduce the debugging difficulty of the optical system. The primary mirror is fixed in the primary mirror room by six bonding points. The back surface of the primary mirror room is connected with the primary mirror room backboard to provide a mounting interface for the lens assembly, the primary mirror auxiliary support and the back optical path assembly of laser communication system. The finite element analysis results showed that the first order modal frequency of the structure was 345 Hz, the root-mean-square (RMS) value of the primary mirror surface shape error is better than λ/ 28 in the ambient operating temperature range of 20±5 °C. The system wavefront aberration was tested using an 4D interferometer, test results showed that the RMS value of the system wavefront aberration is better than λ/14. It can satisfy the requirements of the laser communication system and provide the technical basis for the following works of the project.

A Laser Communication Antenna with Integrated Optical Hood

The Thirty Meter Telescope (TMT) is one of the largest ground-based telescopes currently under construction in the world. Changchun Institute of Optics, Fine Mechanics and Physics(CIOMP) took the task of design and manufacture Tertiary Mirror System (M3S), which is also named Giant Steerable Science Mirror(GSSM). CIOMP decided to design and manufacture a 1/4 scaled prototype of M3S(M3SP) to verify the technical feasibility of M3S design. The tertiary mirror was support by 18 points whiffletree structure along axial direction and 12 points whiffletree structure along lateral direction. Finite Element Model was built to evaluate the system performance. Based on the Finite Element Analysis, the SlopeRMS of tertiary mirror surface figure would be 1.9 μrad when the mirror was pointed vertical under gravity, and was 0.46μrad when the mirror was pointed horizontally. By applying adjust moment on the pivot of axial whiffletree system, the surface figure SlopeRMS when mirror was pointed vertically could be improve to 0.95μrad. The support system’s resonance frequency was 53.7Hz, which indicated that the system stiffness was high enough. Mirror and structure stress level and meet the requirement of system safety.

Thirty Meter Telescope tertiary mirror system prototype cell assembly analysis

To calibrate the tracing performance of the thirty meter telescope (TMT) tertiary mirror, for the special requirement of the TMT, the laser tracker is used to verify the motion. Firstly, the deviation is divided into two parts, namely, the repeatable error and the unrepeatable part. Then, based on the laser tracker, the mearturement and evalutation methods of the rigid body motion for the mirror are established, and the Monte Carol method is used to determine the accuracy of the mothod. Lastly, the mothod is applied to the turn table of a classical telescope and the residual error is about 4 arc second. The work of this paper will guide the next desgin and construction work of the thirty meter telescope tertiary mirror.

TMT tertiary mirror axis calibration with laser tracker

Progress in TMT M3 system

To increase the anti-torsion stiffness of secondary mirror support structure of a telescope and to reduces the obscuration from the support structure,an imposed preload of 8-vane spider was designed to replace the original 4-vane spider.According to the Euler-Bernoulli beam theory,the mirror support structure was simplified as a simple model consisting of a beam and a mass point,and then the simplified model was divided into two more simple kinetic models.By selecting the appropriate mode function,the numerical solution of the first order modal for the simplified model was deduced with Rayleigh and Dunkerley approaches.Obtained calculated results are in good agreement with that from Fnite Element Analysis(FEA).Moreover,in order to solve the impact of the preload on this structure,a coefficient was deduced in theory.Then,the model was simulated by FEM and the result obtained in FEM is the same as that calculatedone one in theory.The analysis results prove that the method is available for the calculation of the similar structural dynamics characteristics.The simulations show that the first order modal of the structure can change from 11.6 Hz to 23 Hz when the preload increases up to 20 kN,which proves that the preload can effectively impact on the anti-torsion stiffness and reduce the secondary mirror support weight and obscuration ratio.The results can give a reference for designing secondary mirror support structures.

Preloading eight-vane spider for supporting structure of secondary mirror

Status and Development of Tertiary Mirror Technology in Large Aperture Telescope

Passive support system of light-weighted SiC primary mirror

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Progress in TMT M3 system

Preloading eight-vane spider for supporting structure of secondary mirror

Status and Development of Tertiary Mirror Technology in Large Aperture Telescope

Passive support system of light-weighted SiC primary mirror