Astrometric observations of outer Jovian satellites with the `Saturn' telescope. First results

TL;DR

This paper reports initial astrometric observations of outer Jovian satellites using the renovated `Saturn' telescope, achieving positional accuracy of 20-100 mas to improve satellite ephemerides.

Contribution

First results from astrometric measurements of Jovian satellites with the `Saturn' telescope after its partial renovation and equipment upgrade.

Findings

Achieved positional accuracy of 20-100 mas.

Residuals mostly do not exceed 100 mas.

Comparison with Himalia observations showed differences up to 113 mas.

Abstract

The one-meter telescope-reflector `Saturn' (D=1 m, F = 4 m) was partially renovated at the Pulkovo observatory at the end of 2014. The telescope was equipped by CCD camera S2C with 14x14 arcmin field of view and 824 mas per pix scale. The observations of outer Jovian satellites have been performed in a test mode since January 2015. The exposure time of 30 seconds allows us to obtain images of stars up to magnitude 19.5 with the present state of the mirror and the equipment. The observations of outer Jovian satellites have been performed during testing period. These objects are interesting targets because their astrometric observations required to improve ephemeris and dynamic studies. Satellites positions have been determined on the basis of CCD images obtained within 6 nights. Astrometric reduction is performed by linear method using HCRF/UCAC4 and HCRF/URAT1. Internal accuracy of satellites positions has been estimated as 20 - 100 mas. The absolute values of residuals O-C do not exceed 100 mas in most cases. The independent tests have been carried out by the direct comparison with the results of observations of the Jovian satellite Himalia performed simultaneously by the Normal astrograph (the largest difference was 113 mas). This work has been partially supported by RFBR (12-02-00675-a) and the 22 Program of RAS Praesidium.