The Space High-cadence Observing Telescope (SHOT) is proposed to operate at the frequency band of 1 ∼ 3 THz. It will have a wide field of view to achieve a large sky area imaging survey and gather more information about the dynamic universe. A prototype telescope with 500 mm aperture will be established and tested at the preliminary stage. The telescope adopts a dual-reflector system. Considering the lightweight design, topology optimization of three cases of reflectors with aluminum, SiC and CFRP are carried out to supply a reference of the initial structure design and material option. In the initial design, the aluminum secondary reflector is supported by a steel cylinder and connected to the support structure of the main reflector using steel tripods. The back side of the main reflector is mostly distributed with triangular holes and supported through three points. The main reflector adopts SiC. To further improve the performance, the multiple-objective size optimization is conducted according to the finite element analysis results. The total weight of the optimal structure is only 8.62 kg, 31% less than the initial design. The surface deformation rms is 2.18 μm by loading gravity and 50 K temperature difference. The stiffness of the structure is also sufficient.
The transition edge sensor (TES) bias waveform is the summation of carriers of equal, or similar, power. Because of the relative phases, the amplitude of the waveform at any given time sample will exceed the maximum range of the digital-toanalog converter (DAC). And this poses the problem of clipping buffer. Scale the waveform so that it fits within the DAC limits results in carrier and average powers that are reduced by the square of the scaling factor. Directly clip the waveform reduces the carrier power and introduces higher relative phase error. This work develops a clipping algorithm that can generate reliable buffer waveforms without affecting power in each carrier. In TES readout, we need to acquire the accurate initial phases of signals of interest. Coarse channelization followed by fine channelization can be adopted to achieve higher spectral resolution. In radio astronomy, the fast Fourier transform (FFT) is commonly used as channelization for signal processing, while it causes spectral leakage. And this problem can be greatly improved by the technique of polyphase filterbanks (PFB). The PFB consists of a polyphase FIR frontend and an FFT. In order to verify the effectiveness of PFB, we use FFT + FFT method and PFB + FFT method to acquire the initial phases and make a comparison.
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