For its compact size and light weight, space telescope with deployable support structure for its secondary mirror is very
suitable as an optical payload for a nanosatellite or a cubesat. Firstly the realization of a prototype deployable space
telescope based on tape springs is introduced in this paper. The deployable telescope is composed of primary mirror
assembly, secondary mirror assembly, 6 foldable tape springs to support the secondary mirror assembly, deployable
baffle, aft optic components, and a set of lock-released devices based on shape memory alloy, etc. Then the deployment
errors of the secondary mirror are measured with three-coordinate measuring machine to examine the alignment accuracy
between the primary mirror and the deployed secondary mirror. Finally modal identification is completed for the
telescope in deployment state to investigate its dynamic behavior with impact hammer testing. The results of the
experimental modal identification agree with those from finite element analysis well.
In this paper, a new type of calibration mechanism based on worm drive is presented for a space telescope. This calibration
mechanism based on worm drive has the advantages of compact size and self-lock. The mechanism mainly consists of
thirty-six LEDs as the light source for flat calibration, a diffuse plate, a step motor, a worm gear reducer and a
potentiometer. As the main part of the diffuse plate, a PTFE tablet is mounted in an aluminum alloy frame. The frame is
fixed on the shaft of the worm gear, which is driven by the step motor through the worm. The shaft of the potentiometer is
connected to that of the worm gear to measure the rotation angle of the diffuse plate through a flexible coupler. Firstly, the
calibration mechanism is designed, which includes the LEDs assembly design, the worm gear reducer design and the
diffuse plate assembly design. The counterweight blocks and two end stops are also designed for the diffuse plate assembly.
Then a modal analysis with finite element method for the diffuse plate assembly is completed.
Ground-based optical detection of low-dynamic vehicles in near-space is analyzed to detect, identify, and track high-altitude balloons and airships. The spectral irradiance of a representative vehicle on the entrance pupil plane of ground-based optoelectronic equipment was obtained by analyzing the influence of its geometry, surface material characteristics, infrared self-radiation, and the reflected background radiation. Spectral radiation characteristics of the target in both clear weather and complex meteorological weather were simulated. The simulation results show the potential feasibility of using visible–near-infrared (VNIR) equipment to detect objects in clear weather and long-wave infrared (LWIR) equipment to detect objects in complex meteorological weather. A ground-based VNIR and LWIR optoelectronic experimental setup is built to detect low-dynamic vehicles in different weather. A series of experiments in different weather are carried out. The experiment results validate the correctness of the simulation results.
In this paper, a new type of lightweight passive deployment mechanism based on the tape spring and the shape memory alloy is presented for the secondary mirror of a deployable space telescope. In this passive deployment mechanism for the secondary mirror, the high elastic potential energy of the folded tape springs is used as driving force when the support structure is extended, and the high stiffness characteristics of the circular arc cross section of the tape spring can be used to achieve structure self-locking after deployment. Then a deployable space telescope combined with lightweight passive deployable mechanism for the secondary mirror is designed for applying to nanosatellite imaging. Furthermore, a lock-release device is designed to achieve the function of locking the folded structure and releasing on orbit by taking advantage of the phase transformation characteristics of shape memory alloy with temperature changing. Finally, the correction method for the deployment error of secondary mirror is discussed. The temperature of the tape springs is controlled respectively to make a required length change. This can achieve the purpose of adjusting the position of the secondary mirror and improve the deployment accuracy.
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