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Processing and analysis of lunar laser ranging observations performed with Shajn telescope in Crimea in 1974–1984

Tryapitsyn V.N., Yagudina E.I., Pavlov D.A., Rumyantsev V.V.

Известия ГАО в Пулкове, № 225: Труды Всероссийской астрометрической конференции «Пулково-2018», Санкт-Петербург, 319–324 (2018)

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Analysis of lunar laser ranging (LLR) observational data since 1969 to present time has demonstrated that the LLR is an effective method of Solar System research. It has been proven by building the high-precision ephemeris of the Solar System: DE (USA), EPM (Russia), INPOP (France), and parameters of lunar orbital and rotational motion, as well as others (geodynamical, relativistic), determined with high accuracy by different authors. LLR observation database presently contains more than 24000 normal points. In USSR, LLR measurements were performed in CrAO (Crimea) on the Shajn 2.6 m telescope with an automated laser ranging system developed by the Lebedev Physical Institute, and in the time span of 1969 to 1984 there were obtained 1400 measurements. The accuracy of the measurements, according to literature was initially 3.0 m, then was gradually improved to 0.6 m by 1978. Those measurements are not part of the LLR observations database. Some of these observational data was found in a CrAO facility in Katsiveli. The main purpose of our work was to process the Crimean observations (previously unpublished) with ephemeris EPM2017, and to determine their place in the history of LLR. The real accuracy of these observations was estimated. The results of the processing and analysis are presented. A particularly interesting finding is related to the three normal points of Lunokhod 1 ranges obtained in 1974. Unfortunately, that was not enough to confirm the location of the rover at the McDonald observatory, and the rover was considered lost for 35 years.