[P-CG20] Future missions and instrumentation for space and planetary science

[PCG20-P01] Linearity error evaluation of the Ultra Fine Sun Sensor (UFSS) onboard SOLAR-C

*Yuto Kondo¹, Daiki Yamasaki², Minami Yoshida¹, Kouhei Teraoka¹, Akiko Tei³, Mizuho Uchiyama², Toshifumi Shimizu² (1.The University of Tokyo, 2.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3.National Astronomical Observatory of Japan National Institutes of Natural Sciences)

Keywords:Sun Sensor, CCD, Testing facility, High-precision pointing, SOLAR-C

SOLAR-C is a next-generation solar observation satellite mission led by Japan with significant contributions from the US and European countries. The mission aims to understand the coronal heating mechanism and the onset of solar flares. SOLAR-C can perform spectroscopic observations over a wide temperature range from the chromospheric to the coronal temperature with a high spatial resolution of 0.4” and a high temporal resolution of 1 sec. To achieve these science objectives, it is necessary to maintain high pointing accuracy. This study evaluates the Ultra Fine Sun Sensor (UFSS) performance, which is critical in achieving this pointing accuracy. The UFSS is a non-image focusing instrument with two sets of reticle-linear CCD devices, which are orthogonally arranged and obtain solar angles when the Sun is located in the UFSS’s FOV (1x1 deg^2). One of the essential items for characterizing the UFSS performance is "linearity error". Linearity error refers to the deviation of the output angle from the proper angle within the UFSS’s FOV, and it is required to be less than 2 arcseconds (p-p) after characterization. We newly developed a measurement system to evaluate the linearity error for a breadboard model of the UFSS. We assessed the accuracy of the measurement system and, by implementing several procedures, successfully established the measurement system that achieves a measurement accuracy of less than 1”. Using this system, we performed the linearity error measurements several times. The measurements allowed us to derive a correction function to characterize the sensor outputs and to confirm that the linearity error is smaller than 2 arcsec (p-p) in most datasets. Our presentation discusses the cause of large linearity errors and introduces required verification items in an engineering model.