Hα birefringent filter design for the space solar telescope

The filter on the space solar telescope (SST) has to be compatible with the space environment. A filter was designed in which stepping motors and the transfer mechanism rotating the waveplate is eliminated to reduce the weight and increase the reliability. The actual working temperature in the filter was kept constant in the laboratory. The precise azimuth of the rotating half waveplate was measured and adjusted to the theoretical value. The wavelength is in the admissible range 656.3±0.2 nm so that the half waveplates in the optical system need not rotate. The structural design was validated in simulated space environment tests. The structure is compact and has no leakage with excellent temperature control.