New astrometric reduction of old photographic observations of Saturn’s moons based on digitizing of astronegatives

Narizhnaya

et al. 2021

A&A

Context. We present a remeasurement of old photographic plates, providing important raw data for dynamical studies of the Saturnian satellite system. The unprecedentedly accurate realization of the Gaia reference frame allows us to make a precise calibration of digitized astronegatives of the Saturnian satellite images. Aims. We reprocessed 357 astronegatives taken with the 26-inch refractor and the normal astrograph of the Pulkovo Observatory between 1972 and 2007 to obtain the positions of the main Saturnian moons in the second Gaia data release (Gaia DR2) system. Methods. Photographic plates were digitized with the Pulkovo Mobile Digitizing Device scanner. The New Astrometric Reduction of Old Observations digitizer at the Paris Observatory was used to calibrate the scanned images. Satellite image centering and astrometric reduction were performed. Results. In total, 6487 positions (equatorial coordinates) have been determined with an accuracy of 50 mas. This is confirmed by a comparison of our data with modern ephemerides. The verification of the results was performed using data from past close approaches by Saturnian satellites to Gaia reference stars, showing the adequacy of the current residual analysis. A joint review of the Pulkovo and the United States Naval Observatory intersatellite positions allows us to conclude about the existence of faint systematic effects in the satellite theories of motions at the 10 mas level.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Astrometric measurement and reduction of Pulkovo photographic observations of the main Saturnian satellites from 1972 to 2007 in the Gaia reference frame

Khovritchev

Narizhnaya

et al. 2021

A&A

“…The USNO photographic observations, taken with the 26-inch refractor, ended in 1999 when Kodak ceased making the necessary plates, while Pulkovo continued their photographic program for a few more years using ORWO plates (Kiseleva & Khrutskaya 2007;Kiseleva et al 2015).…”

Section: Usno Photographic Observationsmentioning

confidence: 99%

New astrometric measurement and reduction of USNO photographic observations of the main Saturnian satellites: 1974−1998

Pascu

Lainey

et al. 2016

A&A

Context. Accurate positional measurements of planets and satellites are used to improve our knowledge of their orbits and dynamics, and to infer the accuracy of the planet and satellite ephemerides. Aims. In the framework of the European FP7 ESPaCE program, we provide the positions of Saturn and its main satellites taken with the US Naval Observatory 26-inch refractor from 1974 to 1998. Methods. We measured 526 astrophotographic plates with the digitizer of the Royal Observatory of Belgium and reduced them through an optimal process that includes image, instrumental, and spherical corrections using the UCAC4 catalog to provide the most accurate equatorial (RA, Dec) positions. Results. We compared the observed positions of the satellites with the theoretical positions from INPOP13c and DE432 planetary ephemerides and from NOE-6-2015-SAT and SAT375 satellite ephemerides. The mean post-fit rms residuals in equatorial positions range from ±68 mas for the Titan observations or 400 km at Saturn, to ±100 mas for the Hyperion observations or 600 km at Saturn. The mean post-fit rms intersatellite residuals range from ±46 mas for the Rhea-Titan observations or 280 km at Saturn, to ±72 mas for the Hyperion-Titan observations or 430 km at Saturn.

“…Observations were realized for proper motion surveys of selected sky areas and open clusters (Bobylev et al 2004), astrometric observations of the Solar System bodies (Kiseleva et al 2015), and photographic surveys used to construct astrometric catalogs (Khrutskaya et al 2004). One of the primary goals was to determine the orbital parameters and masses of binary stars, therefore the archive is half composed of the 26-inch refractor plates (Izmailov et al 2016).…”

Section: Pulkovo Archivementioning

confidence: 99%

The NAROO digitization center

Desmars²,

Lainey³

et al. 2021

A&A

The New Astrometric Reduction of Old Observations (NAROO) center can be found at the Paris Observatory in Meudon, and it is dedicated to the measurement of astrophotographic plates and the analysis of old observations. The NAROO digitizer consists of a granite-based Newport-Microcontrol open-frame air-bearing XY positioning table, a scientific sCMOS camera, and a telecentric optical system. The plate holder assembly is suited for mounting glass plates up to 350 mm squared. The machine positioning stability is better than 15 nm, and its repeatability is better than 40 nm. With real photographic plate data, we were able to produce measurements with an accuracy better than 65 nm. The renewed interest about photographic plates concerns the expansion of the database of transient objects evolving in time, since digitization now makes it possible to measure images with a high level of accuracy and to identify all the available objects. The information extracted from such materials can be of an astrometric, photometric, and spectroscopic nature, when not purely imaging, with consequences in planetology, near-Earth asteroid risk assessment, astrophysical phenomena, and general relativity, to mention but a few. Through our scientific program in the Gaia era, we detail examples of current and upcoming uses for the community. We invite researchers to use our facilities and digitize their collection by answering our call for proposals.