UFSS (ultra fine sun sensor): CCD sun sensor with sub-arc second accuracy for the next solar observing satellite SOLAR-C

The Ultra Fine Sun Sensor (UFSS) on board the HINODE solar observing satellite is one of the most successful sun sensors. It is the linear CCD sun sensor with a special detection method using multiple slits, called the periodic reticle. The angular resolution of 0.14 arcsec in the noise equivalent angle (NEA) and 1 arcsec stability were achieved by the sensor head, of 1.2 kg weight. The concept of the detection method and processing algorithm of the Sun’s direction is described. The system is modeled and the dynamic response of the system is characterized by the first-order lag system. By utilizing this characteristic, a resolution improvement three times higher can be expected by adjusting the parameters with a small modification to the HINODE UFSS processing algorithm. The design for a new UFSS for the next generation solar observation satellite, SOLAR-C, shall include these modifications. The thermomechanical design is also reviewed to improve stability and a design policy is obtained.