Accuracy of Satellite Optical Observations and Precise Orbit Determination

Abstract

ABSTRACT. The monitoring of low-orbit space objects (LEO-objects) is performed in the Astronomical Observatory of Odessa I.I. Mechnikov National University (Ukraine) for many years. Decades-long arсhives of these observations are accessible within Ukrainian network of optical observers (UMOS). In this work, we give an example of orbit determination for the satellite with the 1500-km height of orbit based on angular observations in our observatory (Int. No. 086). For estimation of the measurement accuracy and accuracy of determination and propagation of satellite position, we analyze the observations of Ajisai satellite with the well-determined orbit. This allows making justified conclusions not only about random errors of separate measurements, but also to analyze the presence of systematic errors, including external ones to the measurement process. We have shown that the accuracy of one measurement has the standard deviation about 1 arcsec across the track and 1.4 arcsec along the track and systematical shifts in measurements of one track do not exceed 0.45 arcsec. Ajisai position in the interval of the orbit fitting is predicted with accuracy better than 30 m along the orbit and better than 10 m across the orbit for any its point.

Observation of LEO Objects Using Optical Surveillance Facilities: The Geographic Aspect

“…We will further consider angle D as the difference between the RAAN of the satellite's orbit and the relevant right ascension of the Sun: D = RAANSat -RASun. The observability of the given LEO spacecrafts at the equatorial OSF during 2017 was inferred by direct computation of the ephemerides with standard software, which is usually deployed to schedule and perform observations of LEO objects at AO ONU (Shakun et al, 2014(Shakun et al, , 2016(Shakun et al, , 2017. Orbital elements of LEO spacecrafts were updated fortnightly (if they were available online in the CSpOC/USStratCom catalogue or on the Mike McCants Satellite Tracking web pages [see Mike McCants' website]).…”

“…Not only is the number of optical devices growing, but also they are found to be increasingly more capable; research, development and engineering activities are well underway aiming at making such devices more versatile and useful, as is the case, for instance, for optical sensors for tracking objects in LEO (Lal et al, 2018). Optical sensors are certainly trail the radar ranging systems in respect of the scope of observations and capability to conduct survey irrespective of the weather conditions and the time of day; on the other hand, they have a significant advantage in their efficiency in terms of the development and maintenance costs, ensuring at that high accuracy of both estimated positions of LEO objects (Sánchez-Ortiz, 2018;Shakun et al, 2017) and assessment of their current status from the photometric observations (Koshkin et al, 2018;Shakun et al, 2014;Silha et al, 2018) or dynamic parameters (Friedman & Frueh, 2018). Besides, at relatively low costs (as compared with the costs of radar ranging systems), the OSF enable conducting observations of extremely small LEO objects, such as nanosatellites (Gasdia et al, 2017), using new detectors among others (Schildknecht et al, 2014).…”