William Ryan, New Mexico Institute of Mining and Technology, Eileen V. Ryan, New Mexico Institute of Mining and Technology
Keywords: Space situational awareness, spin rates, GEO-satellites
Abstract:
A satellites general characteristics can be substantially influenced by changes in the space environment. Rapidly spinning decommissioned satellites provide an excellent opportunity to study the rotation-dependent physical processes that affect a resident space objects (RSO) spin kinematics over time. Specifically, inactive satellites at or near geosynchronous Earth-orbit (GEO) provide easy targets for which high quality data can be collected and analyzed such that small differences can be detected under single-year or less time frames.
Previous workers have shown that the rotational periods of defunct GEOs have been changing over time [1]. Further, the Yarkovsky-OKeefe-Radzievskii-Paddak (YORP) effect, a phenomenon which has been well-studied in the context of the changing the spin states of asteroids, has recently been suggested to be the cause of secular alterations in the rotational period of inactive satellites [2]. Researchers at the Magdalena Ridge Observatory 2.4-meter telescope (operated by the New Mexico Institute of Mining and Technology) have been investigating the spins states of retired GEOs and other high altitude space debris since 2007 [3]. In this current work, the 2.4-meter telescope was used to track and observe the objects typically over a one- to two-hour period, repeated several times over the course of weeks. When feasible, this is then repeated on a yearly basis. Data is taken with a 1 second cadence, nominally in groups of three 600 second image sets. With the current equipment, the cadence of the image sequences is very precise while the start time is accurate only to the nearest second. Therefore, periods are determined individually using each image sequence. Repeatability of the period determination for each of these sequences is typically on the order of 0.01 second or better for objects where a single period is identified.
Spin rate periods determined from the GEO light curves collected thus far have been found to range from ~3 sec to many tens of seconds. Based on these observed rotational characteristics, results will be presented on both the long- and short-term spin-rate variations of selected targets. The objective was to study a variety of satellites for rotational stability over time, and to discern how physical effects (such as YORP) might be dependent on the optical, thermal and geometrical parameters of the object.
References:
[1] Papushev, P., Karavaev, Y., and Mishina, M., Investigations of the evolution of optical characteristics and dynamics of proper rotation of uncontrolled geostationary artificial satellites, Advances in Space Research, 416-1422, 2009.
[2] Albuja, A.A. and Scheeres, D.J., Defunct Satellites, Rotation Rates and the YORP Effect, Proceedings of the Advanced Maui Optical and Space Surveillance Technologies Conference, Wailea, Hawaii, 156-163, 2013.
[3] Romero, V., W.H. Ryan, and E.V. Ryan, Monitoring Variations to the Near-Earth Space Environment during High Solar Activity using Orbiting Rocket Bodies, Proceedings of the 2007 AMOS Technical Conference, Hawaii, 389-393, 2007.
Date of Conference: September 15-18, 2015
Track: Poster