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Myung Cho - One of the best experts on this subject based on the ideXlab platform.

  • Control modeling of the fast-steering Secondary Mirror for GMT
    Modeling Systems Engineering and Project Management for Astronomy VIII, 2018
    Co-Authors: Christoph Dribusch, Myung Cho, Youra Jun, Jieun Ryu, Gary Poczulp, Ming Liang, Sungho Lee, Jeong-yeol Han, Ueejeong Jeong, Sanghyuk Kim
    Abstract:

    The Giant Magellan Telescope (GMT) will feature two Gregorian Secondary Mirrors, an adaptive Secondary Mirror (ASM) and a fast-steering Secondary Mirror (FSM). The FSM has an effective diameter of 3.2 m and consists of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fast guiding to attenuate telescope wind shake and mount control jitter. This tiptilt capability thus enhances performance of the telescope in the seeing limited observation mode. The tip-tilt motion of the Mirror is produced by three piezo actuators. In this paper we present a simulation model of the tip-tilt system which focuses on the piezo-actuators. The model includes hysteresis effects in the piezo elements and the position feedback control loop.

  • Development status of the fast-steering Secondary Mirror of GMT
    Ground-based and Airborne Telescopes VII, 2018
    Co-Authors: Sungho Lee, Jeong-yeol Han, Ueejeong Jeong, Sanghyuk Kim, Bongkon Moon, Chang-hee Kim, Yunjong Kim, Chan Park, Byeong-gon Park, Myung Cho
    Abstract:

    The Giant Magellan Telescope (GMT) will be equipped with two Gregorian Secondary Mirrors; a fast-steering Secondary Mirror (FSM) for seeing-limited operations and an adaptive Secondary Mirror (ASM) for adaptive optics observing modes. The FSM has an effective diameter of 3.2 m and is comprised of seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary Mirror. Each FSM segment has a tip-tilt capability for fast guiding to attenuate telescope wind shake and jitter. The FSM is mounted on a two-stage positioning system; a macro-cell that positions the entire FSM segments as an assembly and seven hexapod actuators that position and drive the individual FSM segments. In this paper, we present a technical overview of the FSM development status. More details in each area of development will be presented in other papers by the FSM team.

  • Development of the fast steering Secondary Mirror assembly of GMT
    Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 2016
    Co-Authors: Sungho Lee, Myung Cho, Christoph Dribusch, Jeong-yeol Han, Ueejeong Jeong, Chan Park, Byeong-gon Park, Yang Noh Yoon, Je Heon Song, Won Hyun Park
    Abstract:

    The Giant Magellan Telescope (GMT) will be featured with two Gregorian Secondary Mirrors, an adaptive Secondary Mirror (ASM) and a fast-steering Secondary Mirror (FSM). The FSM has an effective diameter of 3.2 m and built as seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope sub-apertures and fast guiding to attenuate telescope wind shake and mount control jitter. This tip-tilt capability thus enhances performance of the telescope in the seeing limited observation mode. As the first stage of the FSM development, Phase 0 study was conducted to develop a program plan detailing the design and manufacturing process for the seven FSM segments. The FSM development plan has been matured through an internal review by the GMTO-KASI team in May 2016 and fully assessed by an external review in June 2016. In this paper, we present the technical aspects of the FSM development plan.

  • Development of GMT Fast Steering Secondary Mirror Assembly
    Ground-based and Airborne Telescopes V, 2014
    Co-Authors: Myung Cho, Christoph Dribusch, Won Hyun Park, Andrew Corredor, Gary Muller, Matt Johns, Charlie Hull, J. Kern, Young-soo Kim
    Abstract:

    The Giant Magellan Telescope (GMT) is one of Extremely large telescopes, which is 25m in diameter featured with two Gregorian Secondary Mirrors, an adaptive Secondary Mirror (ASM) and a fast-steering Secondary Mirror (FSM). The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The guiding philosophy in the design of the FSM segment Mirror is to minimize development and fabrication risks ensuring a set of Secondary Mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter, thus optimizing the seeing limited performance of the telescope. The final design of the FSM Mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The optical surface deformations, image qualities, and structure functions for the gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM Mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy (EE80) in the focal plane. The Mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of tip-tilt operation.

  • Optomechanical analysis and testing of a fast steering Secondary Mirror prototype for the Giant Magellan Telescope
    Optomechanical Engineering 2013, 2013
    Co-Authors: Andrew Corredor, Myung Cho, Won Hyun Park, Young-soo Kim
    Abstract:

    The Giant Magellan Telescope (GMT) will be one of the next class of extremely large segmented Mirror telescopes. The GMT will utilize two Gregorian Secondary Mirrors, and Adaptive Secondary Mirror (ASM) and a Fast-steering Secondary Mirror (FSM). The FSM consists of six off-axis Mirrors surrounding a central on-axis circular segment. The segments are 1.1 m in diameter and conjugated 1:1 to the seven 8.4 m segments of the primary. A prototype of the FSM Mirror (FSMP) has been developed, analyzed and tested in order to demonstrate the mechanical and optical responses of the Mirror assembly when subjected to structural and thermal loadings. In this paper, the mechanical and thermal performances of the FSMP were evaluated by performing finite element analyses (FEA) in NX Nastran. The deformation of the Mirror’s lateral flexure was measured when the FSMP was axially loaded and the temperature response of the Mirror assembly was measured when exposed to a sample thermal environment. In order to validate the Mirror/lateral flexure design concept, the mechanical, optical and thermal measurements obtained from the tests conducted on Mirrors having two different lateral flexures were compared to the responses calculated by FEA.

Young-soo Kim - One of the best experts on this subject based on the ideXlab platform.

  • Development of GMT Fast Steering Secondary Mirror Assembly
    Ground-based and Airborne Telescopes V, 2014
    Co-Authors: Myung Cho, Christoph Dribusch, Won Hyun Park, Andrew Corredor, Gary Muller, Matt Johns, Charlie Hull, J. Kern, Young-soo Kim
    Abstract:

    The Giant Magellan Telescope (GMT) is one of Extremely large telescopes, which is 25m in diameter featured with two Gregorian Secondary Mirrors, an adaptive Secondary Mirror (ASM) and a fast-steering Secondary Mirror (FSM). The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The guiding philosophy in the design of the FSM segment Mirror is to minimize development and fabrication risks ensuring a set of Secondary Mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter, thus optimizing the seeing limited performance of the telescope. The final design of the FSM Mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The optical surface deformations, image qualities, and structure functions for the gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM Mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy (EE80) in the focal plane. The Mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of tip-tilt operation.

  • performance evaluation of the tip tilt actuator in fast steering Secondary Mirror for large telescope
    Journal of the Korean Society for Precision Engineering, 2014
    Co-Authors: Ho Sang Kim, Kyoung Don Lee, Dongchan Lee, Young-soo Kim
    Abstract:

    For ground-based telescope application, the performance assessment of tip-tilt actuator is important because the optical quality of telescope depends upon the windshake compensation ability of the fast steering Secondary Mirror. But it is difficult to measure the performance characteristics of the actuators due to the large size Mirror and test facilities including the vacuum support and structural frame. In this paper, the full-scale tip-tilt test bed for the large size Secondary Mirror with diameter of 1m is built and the several tests are performed including the range, resolution and frequency response function. From the measurement results, it is shown that the tip-tilt actuator can successfully compensate the windshake with frequency of maximum 12 Hz and be a candidate for the Giant Magellan Telescope.

  • Optomechanical analysis and testing of a fast steering Secondary Mirror prototype for the Giant Magellan Telescope
    Optomechanical Engineering 2013, 2013
    Co-Authors: Andrew Corredor, Myung Cho, Won Hyun Park, Young-soo Kim
    Abstract:

    The Giant Magellan Telescope (GMT) will be one of the next class of extremely large segmented Mirror telescopes. The GMT will utilize two Gregorian Secondary Mirrors, and Adaptive Secondary Mirror (ASM) and a Fast-steering Secondary Mirror (FSM). The FSM consists of six off-axis Mirrors surrounding a central on-axis circular segment. The segments are 1.1 m in diameter and conjugated 1:1 to the seven 8.4 m segments of the primary. A prototype of the FSM Mirror (FSMP) has been developed, analyzed and tested in order to demonstrate the mechanical and optical responses of the Mirror assembly when subjected to structural and thermal loadings. In this paper, the mechanical and thermal performances of the FSMP were evaluated by performing finite element analyses (FEA) in NX Nastran. The deformation of the Mirror’s lateral flexure was measured when the FSMP was axially loaded and the temperature response of the Mirror assembly was measured when exposed to a sample thermal environment. In order to validate the Mirror/lateral flexure design concept, the mechanical, optical and thermal measurements obtained from the tests conducted on Mirrors having two different lateral flexures were compared to the responses calculated by FEA.

  • Development of a prototype off-axis Secondary Mirror for GMT
    Renewable Energy and the Environment: Postdeadline Papers, 2013
    Co-Authors: Young-soo Kim, Myung Cho, Ju Heon Koh, Hwa Kyoung Jung, Ho June Jung, Ho Soon Yang, Ho Sang Kim, Kyoung Don Lee, Hyo-sung Ahn, Won Hyun Park
    Abstract:

    The Fast Steering Mirror (FSM) of the GMT is going to be the first-light Secondary Mirror system. An FSM prototype has been developed which consists of 1 m off-axis aspheric Mirror and tip-tilt test-beds. The successful development results are presented.

  • development of a fast steering Secondary Mirror prototype for the giant magellan telescope
    Proceedings of SPIE, 2012
    Co-Authors: Myung Cho, Christoph Dribusch, Young-soo Kim, Andrew Corredor, Kwijong Park, Ilkweon Moon, Won Hyun Park
    Abstract:

    The Giant Magellan Telescope (GMT) will be a 25m class telescope currently in the design and development phase. The GMT will be a Gregorian telescope and equipped with a fast-steering Secondary Mirror (FSM). This Secondary Mirror is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The prototype of FSM (FSMP) development effort is led by the Korea Astronomy and Space Science Institute (KASI) with several collaborators in Korea, and the National Optical Astronomy Observatory (NOAO) in USA. The FSM has a tip-tilt feature to compensate image motions from the telescope structure jitters and the wind buffeting. For its dynamic performance, each of the FSM segments is designed in a lightweight Mirror. Support system of the lightweight Mirror consists of three axial actuators, one lateral support at the center, and a vacuum system. A parametric design study to optimize the FSM Mirror configuration was performed. In this trade study, the optical image qualities and structure functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic performances will be discussed.

Won Hyun Park - One of the best experts on this subject based on the ideXlab platform.

  • Development of the fast steering Secondary Mirror assembly of GMT
    Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation II, 2016
    Co-Authors: Sungho Lee, Myung Cho, Christoph Dribusch, Jeong-yeol Han, Ueejeong Jeong, Chan Park, Byeong-gon Park, Yang Noh Yoon, Je Heon Song, Won Hyun Park
    Abstract:

    The Giant Magellan Telescope (GMT) will be featured with two Gregorian Secondary Mirrors, an adaptive Secondary Mirror (ASM) and a fast-steering Secondary Mirror (FSM). The FSM has an effective diameter of 3.2 m and built as seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope sub-apertures and fast guiding to attenuate telescope wind shake and mount control jitter. This tip-tilt capability thus enhances performance of the telescope in the seeing limited observation mode. As the first stage of the FSM development, Phase 0 study was conducted to develop a program plan detailing the design and manufacturing process for the seven FSM segments. The FSM development plan has been matured through an internal review by the GMTO-KASI team in May 2016 and fully assessed by an external review in June 2016. In this paper, we present the technical aspects of the FSM development plan.

  • Development of GMT Fast Steering Secondary Mirror Assembly
    Ground-based and Airborne Telescopes V, 2014
    Co-Authors: Myung Cho, Christoph Dribusch, Won Hyun Park, Andrew Corredor, Gary Muller, Matt Johns, Charlie Hull, J. Kern, Young-soo Kim
    Abstract:

    The Giant Magellan Telescope (GMT) is one of Extremely large telescopes, which is 25m in diameter featured with two Gregorian Secondary Mirrors, an adaptive Secondary Mirror (ASM) and a fast-steering Secondary Mirror (FSM). The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The guiding philosophy in the design of the FSM segment Mirror is to minimize development and fabrication risks ensuring a set of Secondary Mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter, thus optimizing the seeing limited performance of the telescope. The final design of the FSM Mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The optical surface deformations, image qualities, and structure functions for the gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM Mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy (EE80) in the focal plane. The Mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of tip-tilt operation.

  • Optomechanical analysis and testing of a fast steering Secondary Mirror prototype for the Giant Magellan Telescope
    Optomechanical Engineering 2013, 2013
    Co-Authors: Andrew Corredor, Myung Cho, Won Hyun Park, Young-soo Kim
    Abstract:

    The Giant Magellan Telescope (GMT) will be one of the next class of extremely large segmented Mirror telescopes. The GMT will utilize two Gregorian Secondary Mirrors, and Adaptive Secondary Mirror (ASM) and a Fast-steering Secondary Mirror (FSM). The FSM consists of six off-axis Mirrors surrounding a central on-axis circular segment. The segments are 1.1 m in diameter and conjugated 1:1 to the seven 8.4 m segments of the primary. A prototype of the FSM Mirror (FSMP) has been developed, analyzed and tested in order to demonstrate the mechanical and optical responses of the Mirror assembly when subjected to structural and thermal loadings. In this paper, the mechanical and thermal performances of the FSMP were evaluated by performing finite element analyses (FEA) in NX Nastran. The deformation of the Mirror’s lateral flexure was measured when the FSMP was axially loaded and the temperature response of the Mirror assembly was measured when exposed to a sample thermal environment. In order to validate the Mirror/lateral flexure design concept, the mechanical, optical and thermal measurements obtained from the tests conducted on Mirrors having two different lateral flexures were compared to the responses calculated by FEA.

  • Development of a prototype off-axis Secondary Mirror for GMT
    Renewable Energy and the Environment: Postdeadline Papers, 2013
    Co-Authors: Young-soo Kim, Myung Cho, Ju Heon Koh, Hwa Kyoung Jung, Ho June Jung, Ho Soon Yang, Ho Sang Kim, Kyoung Don Lee, Hyo-sung Ahn, Won Hyun Park
    Abstract:

    The Fast Steering Mirror (FSM) of the GMT is going to be the first-light Secondary Mirror system. An FSM prototype has been developed which consists of 1 m off-axis aspheric Mirror and tip-tilt test-beds. The successful development results are presented.

  • development of a fast steering Secondary Mirror prototype for the giant magellan telescope
    Proceedings of SPIE, 2012
    Co-Authors: Myung Cho, Christoph Dribusch, Young-soo Kim, Andrew Corredor, Kwijong Park, Ilkweon Moon, Won Hyun Park
    Abstract:

    The Giant Magellan Telescope (GMT) will be a 25m class telescope currently in the design and development phase. The GMT will be a Gregorian telescope and equipped with a fast-steering Secondary Mirror (FSM). This Secondary Mirror is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The prototype of FSM (FSMP) development effort is led by the Korea Astronomy and Space Science Institute (KASI) with several collaborators in Korea, and the National Optical Astronomy Observatory (NOAO) in USA. The FSM has a tip-tilt feature to compensate image motions from the telescope structure jitters and the wind buffeting. For its dynamic performance, each of the FSM segments is designed in a lightweight Mirror. Support system of the lightweight Mirror consists of three axial actuators, one lateral support at the center, and a vacuum system. A parametric design study to optimize the FSM Mirror configuration was performed. In this trade study, the optical image qualities and structure functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic performances will be discussed.

Liang Tang - One of the best experts on this subject based on the ideXlab platform.

  • Development of an isotropic Stewart platform for telescope Secondary Mirror
    Mechanical Systems and Signal Processing, 2019
    Co-Authors: Hai Yun, Lei Liu, Liang Tang
    Abstract:

    Abstract For large aperture telescopes, active control of the Secondary Mirror is essential for correction of the aberrations. In this paper, an isotropic Stewart platform is developed for the telescope Secondary Mirror control system, providing 6-DOF high-precision pointing and positioning. The isotropic configuration is designed and one experimental prototype of the isotropic Stewart platform is constructed. Then, the isotropic characteristic is investigated through the verification experiments based on the statics principle. Furthermore, the dynamics model of the isotropic Stewart platform is established and the model properties are analyzed. Finally, the experimental prototype is developed and the decoupled controller is adopted. The experimental results demonstrate the effectiveness of the decoupled control strategy and further validate the proposed isotropic drive mechanism for the telescope Secondary Mirror.

Andreas Reinacher - One of the best experts on this subject based on the ideXlab platform.

  • SOFIA Secondary Mirror mechanism heavy maintenance and improvements
    Ground-based and Airborne Telescopes VI, 2016
    Co-Authors: Yannick Lammen, Michael Lachenmann, Andreas Reinacher, Ivar Kjelberg, Serge Droz, Holger Jakob, Friederike Graf, Alfred Krabbe
    Abstract:

    The Stratospheric Observatory For Infrared Astronomy (SOFIA) reached its full operational capability in 2014 and completed hundreds of observation flights. Since its installation in 2002, the Secondary Mirror Mechanism was subject to thousands of operating hours equivalent to millions of load cycles. During the aircraft heavy maintenance in fall 2014, a four month time window enabled the removal of the mechanism from the telescope structure for service and improvements. Next to visual corrosion- and crack-inspection of the flexures, critical electronic components (in particular the set of three eddy current position sensors that determine the Mirror tilt) were replaced. Moreover, a detailed temperature dependent position calibration of the system was performed in a cold chamber to improve the pointing accuracy. Until then, a simple temperature independent linear gain was used to translate the sensor output voltage into a position. For accurate positioning across the whole temperature range, a temperature dependent correction function had to be developed. This calibration would have cost hours of observing time when performed in flight which made it an essential goal for completion during the maintenance period. An autocollimator was used as optical reference camera to measure the tip-tilt position of the Secondary Mirror in the cold chamber. Using this calibration setup, a pattern of many Mirror positions in the tip-tilt domain was approached at several temperature points to provide a high resolution data set for the new multidimensional calibration function. Follow-up in-flight verification measurements confirmed a large improvement in pointing accuracy as soon as the temperature measurements were included into the position correction. Improvements of up to a factor of 10 were especially noticed in the lower temperature range. This contribution provides an insight into the work performed during the SOFIA - Secondary Mirror Mechanism maintenance with the focus on the temperature dependent position calibration.

  • Characterization of the mechanical properties of the SOFIA Secondary Mirror mechanism in a multi-stage approach
    Ground-based and Airborne Telescopes VI, 2016
    Co-Authors: Benjamin Greiner, Yannick Lammen, Andreas Reinacher, Alfred Krabbe, Jörg F. Wagner
    Abstract:

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) uses its compact and highly integrated Secondary Mirror Mechanism (SMM) to switch between target positions on the sky in a square wave pattern. This chopping motion excites eigenmodes of the mechanism structure, which limit controller and observatory performance. We present the setup and results of experimental modal tests performed on different building stages of a test-bench model as well as on the original flight hardware. Test results were correlated to simulations employing a finite element model in order to identify excited mode shapes and contributing flexible components of the Secondary Mirror Mechanism. It was possible to isolate the motion of the compensation ring and its elastic mounts as the vibration mode inducing the main disturbance at about 300 Hz, which is currently the main mode shape limiting the performance of the chopping controller.

  • Modeling of the SOFIA Secondary Mirror controller
    Integrated Modeling of Complex Optomechanical Systems, 2011
    Co-Authors: Andreas Reinacher, Hans-peter Roeser
    Abstract:

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.5m infrared telescope built into a Boeing 747SP. During observations the telescope will not only be subject to aircraft vibrations and maneuver loads - by opening a large door to give the observatory an unhindered view of the sky, there will also be aerodynamic and aeroacoustic disturbances. A critical factor in the overall telescope performance is the SOFIA Secondary Mirror Assembly (SMA). The 35cm silicon carbide Mirror is mounted on the Secondary Mirror Mechanism (SMM), which has five degrees-offreedom and consists of two parts: The slow moving base for focusing and centering, and on top of that the Tilt Chop Mechanism (TCM) for chopping with a frequency of up to 20Hz and a chop throw of up to 10arcmin. The development of the controller that is used to meet the stringent performance requirements relys heavily on a state space model of the system. A pole-placement controller is compared to an optimal LQG control approach which makes use of the model to calculate all required system states in real-time. The paper explains the modeling of the TCM with linear differential equations and the optimization via a grey-box model approach with system identification data. Simulated data is then compared to measurements taken on ground and in flight.

  • Improvement of the SOFIA Secondary Mirror Controller
    Ground-based and Airborne Telescopes III, 2010
    Co-Authors: Andreas Reinacher, E. Onillon, Hans-peter Roeser
    Abstract:

    The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a 2.5m infrared telescope build into a Boeing 747SP. During observations the telescope will not only be subject to aircraft vibrations and maneuver loads - by opening a large door to give the observatory an unhindered view of the sky, there will also be aerodynamic and aeroacoustic disturbances. A critical factor in the overall telescope performance is the SOFIA Secondary Mirror Assembly. The 35cm silicon carbide Mirror is mounted on the Secondary Mirror Mechanism, which has five degrees-of-freedom (rotation about line of sight is blocked) and consists of two parts: The slow moving base for focusing and centering, and on top of that the Tilt Chop Mechanism (TCM) for chopping with a frequency of up to 20Hz and a chop throw of up to 10arcmin. A new controller for the TCM is introduced in this paper in order to meet the stringent performance requirements for the chopper. A state space controller is chosen that combines a feedback path for steady state behavior with a model-based feed forward controller for improved settling time performance. The paper explains the modeling of the TCM via a grey box model approach optimized with system identification data and compares simulated with measured data. Then the structure of the controller is explained and Matlab/Simulink simulations are presented. The simulation results are compared to measurements taken with the real system on ground and finally flight test results with open and closed door are discussed.