Dr. Tatsuhiro Sato Profile

Dr. Tatsuhiro Sato

at National Astronomical Observatory of Japan

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Publications (2)

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Proceedings Article | 13 December 2020 Poster + Paper

Prototyping of log analysis infrastructure for the Subaru telescope based on the ALMA experience

Kyoko Nakamura, George Kosugi, Tatsuhiro Sato, Eisuke Morita, Yohei Hayashi

Proceedings Volume 11449, 114492D (2020) https://doi.org/10.1117/12.2561190

KEYWORDS: Telescopes, Prototyping, Optical correlators, Databases, Data storage, Error analysis

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Elasticsearch is one of solutions to monitor and analyze logs. Even with ALMA∗, observation logs are stored and anyone can look into it according to their purpose. For example, Hastings, which is a tool discovers the root cause of the defect, is utilized for ACA Correlator subsystem†. It queries logs to an ALMA Elasticsearch storing operational logs, analyzes specific messages which infer troubles, then outputs a result. Before the ALMA Elasticsearch was deployed, logs should have been collected manually in advance. Now the ALMA Elasticsearch has become available and we’ve known: 1) Elasticsearch can directly configure and access features by using REST API, 2) Logs taken even years ago can also be retrieved easily, 3) Elasticsearch’s major update didn’t cause much loss of time to change Hastings, 4) Python has several methods to manage Elasticsearch so that we can choose a favorite one. Therefore, we thought to apply Elasticsearch to the Subaru telescope‡. Size of Subaru logs are quite large but they are not stored in any database yet and just archived. We created a cluster system with Elasticsearch for the evaluation purpose and found ways to store data in a short time. We estimated the total ingestion time for 20 years of telescope status data to be at most 5 months. Our goal is to find a feasible cause of any defects in near real time, to predict any errors that may occur in near future, and to analyze communication between the telescope and observational equipment to optimize observations.

Proceedings Article | 13 December 2020 Poster + Paper

In-situ monitoring of Subaru Telescope’s optical performance using a portable spectrophotometer

Hirofumi Okita, Hiroyuki Iwashita, Tatsuhiro Sato, Saeko Hayashi, Naruhisa Takato

Proceedings Volume 11451, 114515J (2020) https://doi.org/10.1117/12.2562057

KEYWORDS: Reflectivity, Telescopes, Spectrophotometry, Mirrors, Silver, Surface plasmons, Visible radiation, Reflector telescopes, Data modeling, Infrared radiation

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We report the reflectivity of the Subaru Telescope's mirrors and these time evolutions measured with the Subaru Portable Spectrophotometer (SPS). Thanks to the capability of SPS, the absolute, spectroscopic reflectivity has been measured in-situ on the telescope since October 2017, and it becomes possible to understand and forecast the time evolution of the reflectivity degradation. We established a simple two factor model for the reflectivity degradation of the primary mirror which has coated with aluminum in 2017. From a study of CO₂ cleaning with SPS, a part of dust on the mirror surface was found to be removed with CO₂ cleaning, on the other hand, the roughness of the surface was found to become larger than before cleaning. The time evolution of the reflectivity of the primary mirror is now able to be forecasted. In parallel, we have applied SPS measurement to the infrared secondary mirror of the Subaru Telescope (IR M2) and found a significant loss of reflectivity in the visible wavelength in November 2018. IR M2 had been coated with silver in 2008 and used for over ten years. Although the original reflectivity of silver mirror is ~98% at 589 nm, there was ~50% in November 2018, and it was ~30% at in November 2019. One of the causes of the significant loss could be due to volcanic gas from the explosion of Kilauea in May 2018; however, it was hard to explain the continuing degradation in reflectivity through the following year. The reflectivity could not be recovered by any quick cleanings. We carried out recoating of IR M2 in November 2019. A three-factor model to explain the reflectivity degradation of IR M2 was considered. The model would help us to understand what happens on silver mirrors. On the other hand, unknown localized phenomenon such as a white spot was seen on the IR M2 mirror surface.

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