The space solar observation equipment takes the spacecraft as the platform, and the vibration of spacecraft will have influence over the observation. Therefore, we need to develop the image stabilization system to ensure the imaging resolution. In this paper, a method for detecting the centroid deviation of solar facula is proposed. A photodiode-based deviation detector was designed based on the requirements of the image stabilization system for the Full-disc vector Magneto Graph. Compared with the traditional method of deviation detecting, it has faster response rate, lower power consumption. Backup design is added to improve the reliability of the work on orbit. According to the test results, a resolution of 5 μm is achieved within the working range. It can cooperate with the steering mirror mechanism to form the image stabilization system and serve the Full-disc vector Magneto Graph.
A new type Stressed Mirror Polishing method using annular polishing machine is developed in NIAOT. It provides good efficiency for the massive production of off-axis segments for the extremely large telescope because 3 or more pieces of segment can be polished simultaneously on a AP machine. With an annular polishing machine with 3.6m diameter, two scale-down TMT segments have been polished. Both 2 segments are Φ1100mm in diameter, with the vertex radius of curvature of 60m and aspheric constant K=-1.000953. The off-axis distances (OAD) are 8m and 12m respectively. After SMAP process, the acceptable surface accuracy can be reached, which is 1.12μm/0.23μm of PV/RMS value for the segment with 8m OAD, and 1.22 μm/0.26 μm for another one.
ASO-S is a mission proposed for the 25th solar maximum by the Chinese solar community. The scientific objectives are to study the relationships among solar magnetic field, solar flares, and coronal mass ejections (CMEs). ASO-S consists of three payloads: Full-disk Magnetograph (FMG), Lyman-alpha Solar Telescope (LST), and Hard X-ray Imager (HXI), to measure solar magnetic field, to observe CMEs and solar flares, respectively. ASO-S is now under the phase-B studies. This paper makes a brief introduction to the mission.
The Coronal Solar Magnetism Observatory (COSMO) is a facility dedicated to measuring magnetic
fields in the corona and chromosphere of the Sun. It will be located on a mountaintop in the Hawaiian
Islands and will replace the current Mauna Loa Solar Observatory (MLSO). COSMO will employ a
suite of instruments to determine the magnetic field and plasma conditions in the solar atmosphere and
will enhance the value of data collected by other observatories on the ground (SOLIS, ATST, FASR)
and in space (SDO, Hinode, SOHO, GOES, STEREO, DSCOVR, Solar Probe+, Solar Orbiter). The
dynamics and energy flow in the corona are dominated by magnetic fields. To understand the
formation of Coronal Mass Ejections (CMEs), their relation to other forms of solar activity, and their
progression out into the solar wind requires measurements of coronal magnetic fields. The COSMO
suite includes the Large Coronagraph (LC), the Chromosphere and Prominence Magnetometer
(ChroMag) and the K-Coronagraph. The Large Coronagraph will employ a 1.5 meter fuse silica singlet
lens and birefringent filters to measure magnetic fields out to two solar radii. It will observe over a
wide range of wavelengths from 500 to 1100 nm providing the capability of observing a number of
coronal, chromospheric, and photospheric emission lines. Of particular importance to measuring
coronal magnetic fields are the forbidden emission lines of Fe XIII at 1074.7 nm and 1079.8 nm. These
lines are faint and require the very large aperture. NCAR and NSF have provided funding to bring the
COSMO Large Coronagraph to a preliminary design review (PDR) state by the end of 2013.
To obtain high resolution infrared image, both low photon efficiency and long wavelength of infrared light requires
enough large aperture telescope, but large aperture vacuum windows can hardly achieve high optical quality, so open
structure becomes the only viable choice for large infrared solar telescope. In addition to the effects of atmospheric
turbulence, open solar telescopes suffer from the heating of the optics by sunlight, especially primary mirror heating.
These factors cause the image to shiver and become blurred, and increase infrared observing noise. Since blowing air
across the front surface of the primary mirror doesn't have the necessary heat transfer coefficient to remove the absorbed
heat load, it must be cooled down to maintained at a temperature between 0K and 2K below ambient air temperature to
reduce the effects of turbulence. This paper will introduce some cooling methods and simulation results of primary
mirror in large infrared solar telescope. On the other hand, mirror material with nice thermal conductivity can reduce the
temperature difference between mirror surface and air, and mirror surface polishing at infrared wavelength can be
comparatively easier than at visible wavelength, so it is possible to select low cost metal mirror as primary mirror of
infrared solar telescope. To analyze the technical feasibility of metal mirror serving as primary mirror, this paper also
give some polishing results of aluminum mirror with electroless nickel coating.
A new method, namely the closed-loop pipeline, is proposed for the detection and tracking of point targets in heavy cloudy background. At first, a preprocessing step, i.e., a local contrast threshold is used to remove slowly changing clutter, then the "and logical" pipeline consisting of three frames are used to filter out the noise based on the highly consistency and continuity of the targets in temporal-spatial domain. After the two steps, the sequence is projected into one frame and the trajectory of the target is accumulated in the test pipeline. The target trajectory is detected by cluster analysis and smoothed by finding zero-crossing points; moreover the next searching window is identified by the achieved trajectory segment. So compared with the old open form pipeline, the new structure can predict the tracking window and it is advantageous over the traditional one in terms of searching space, computational complexity and clutter resistance. The experiments show that the proposed method can detect and track dim point targets with arbitrary trajectories accurately, and can also predict the searching windows efficiently.
The main optical system of Space Solar Telescope is composed of primary mirror, collimating lenses and imaging lenses. To satisfy imaging demands of wide range of wavelength (393nm- 656nm), the collimating lenses are composed of five components of which decentering errors are extremely stringent. To satisfy above situation, elastomeric mounting of lens is introduced for each component. The basic centering principle is discussed, the subcell assembly is introduced for the elastomeric mounting. Two aligning methods of are introduced for the alignment of subcells. Athermalization formulation of subcells is given. Besides, finite element model of such mounting is established for analyzing temperature change and elastomer shrinkage effects to lens surfaces.
Balloon-borne Solar Telescope is an optical telescope with effective aperture of 80 cm. To reduce polarization effect to measuring of solar magnetic field, the optical system is specially designed and the collimating lens is special and difficult to calibrate. To reduce the gross weight of telescope, the primary mirror is lightweight with thickness- to-diameter ratio of 1/10. But the system must reach to its imaging quality of diffraction limit. So some special techniques are introduced to guarantee the optical imaging quality. First, lateral shearing interferometer is used to test every optical component after they are assembled in barrels or cells; then two visible points that can be seen through alignment telescope form the optical axis of every component. After system optical axis is established also by alignment telescope, those optical components can be calibrated precisely on it. Since lacking standard mirror that is the same size as primary mirror, some ground-base trial observations without vacuum tube were taken to test the imaging quality. According to astronomer's conclusion, the system can get high resolution solar image when in operation.
To eliminate the mounting stress of three flat reflective mirrors in Balloon-borne Solar Telescope, these optics were attached to their mounts with a thin adhesive layer. This method will also be used in Space Solar Telescope. The primary mirror will be attached to its mount with a thin adhesive layer after first procedure of polishing, then polished to its ultimate demand. In this paper, the theory of adhesive layer analysis is given, and FE model of mirror and its mount is established to analyze the behavior of adhesive layer and the mirror stress. Some experiments are taken to measure Young's modulus of adhesive layer. The possibility of this method in ground-based telescope is also analyzed.
In this system, the experiment mirror has 500 mm aperture and 6 mm thickness. There are 58 actuators and three fixed points in it. A Shack-Hartmann test apparatus is used for the measurement of wavefront aberration. In this apparatus an ingenious equivalent of lenslet array is used. All image points formed by it appear very clear theoretical diffraction pattern. And a CCD from a TV camera is used. Like European Southern Observatory, we use quasi-Zernike polynomial to fit the wavefront aberration for correcting. But in our work correction is to the whole wavefront aberration (except lateral focus and longitudinal focus). In our work, another important character is that the damp least square method is used for determining the forces. The correction results are the root mean square of wavefront aberration about 0.02 - 0.04 micrometers . A circle including measuring and correcting the wavefront aberration takes about 3.3 minutes. A more precise algorithm proposed by us is used for calculating the wavefront aberration for checking.