[Yokozawa, Yuzu]

As an irregular maintenance of TCam for ETMY, we performed the visual inspection this afternoon. During O4a and the commissioning period, the TCam for ETMX showed a problem with the beam appearance (Fig1). We suspected it was due to the problem with the mirror surface in the TCam system or the objective lens of the telescope. For example, it could be moldy. We compared the conditions between TCam of ETMX and ETMY.

• We opened one of the side walls of the TCam (Fig2). However, the mirror in front of the telescope blocked to see the surface objective lens.
• Next, we opened the top side wall and checked the surface objective lens. We noticed that the surface of the objective lens was found to be contaminated (Fig3). It does not appear to be an obvious mold, but I am not sure what it is. We want to clean it next time with ethanol and a cotton swab.
• We checked the mirror in the EYA chamber, which reflects the incident light from the ETMY to the telescope (Fig4). We saw something like white dust on the surface of the mirror. We think this could be a cause of the problem with the ETMY images, which causes the scattering on the ETMY image.
• Concerns
  • Is it possible to clean the mirror in EYA in a safe way?
  • GreenY is needed to see if the problem has been solved after the cleaning. Is it possible for the schedule?