An optical survey for space debris on highly eccentric and inclined MEO orbits

Optical surveys for space debris in high-altitude orbits have been conducted since more than ten years. Originally these efforts concentrated mainly on the geostationary region (GEO). Corresponding observation strategies, processing techniques and cataloguing approaches have been developed and successfully applied. The ESA GEO surveys, e.g., resulted in the detection of a significant population of small-size debris and later in the discovery of high area-to-mass ratio objects in GEO-like orbits. Comparably less experience (both, in terms of practical observation and strategy definition) is available for eccentric orbits that (at least partly) are in the MEO region, in particular for the Molniya-type orbits. Different survey and follow-up strategies for searching space debris objects in highly-eccentric MEO orbits, and to acquire orbits which are sufficiently accurate to catalog such objects and to maintain their orbits over longer time spans were developed. Simulations were performed to compare the performance of different survey and cataloguing strategies. Eventually, optical observations were conducted in the framework of an ESA study using ESA’s Space Debris Telescope (ESASDT) the 1-m Zeiss telescope located at the Optical Ground Station (OGS) at the Teide Observatory at Tenerife, Spain. Thirteen nights of surveys of Molniya-type orbits were performed between January and August 2013. Eventually 255 surveys were performed during these thirteen nights corresponding to about 47 h of observations. In total 30 uncorrelated faint objects were discov- ered. On average one uncorrelated object was found every 100 min of observations. Some of these objects show a considerable brightness variation and have a high area-to-mass ratio as determined in the orbit estimation process

An optical survey for space debris on highly eccentric and inclined MEO orbits

Optical surveys for space debris in high-altitude orbits have been conducted since more than ten years. Originally these efforts concentrated mainly on the geostationary region (GEO). Corresponding observation strategies, processing techniques and cataloguing approaches have been developed and successfully applied. The ESA GEO surveys, e.g., resulted in the detection of a significant population of small-size debris and later in the discovery of high area-to-mass ratio objects in GEO-like orbits. Comparably less experience (both, in terms of practical observation and strategy definition) is available for eccentric orbits that (at least partly) are in the MEO region, in particular for the Molniya-type orbits. Different survey and follow-up strategies for searching space debris objects in highly-eccentric MEO orbits, and to acquire orbits which are sufficiently accurate to catalog such objects and to maintain their orbits over longer time spans were developed. Simulations were performed to compare the performance of different survey and cataloguing strategies. Eventually, optical observations were conducted in the framework of an ESA study using ESA’s Space Debris Telescope (ESASDT) the 1-m Zeiss telescope located at the Optical Ground Station (OGS) at the Teide Observatory at Tenerife, Spain. Thirteen nights of surveys of Molniya-type orbits were performed between January and August 2013. Eventually 255 surveys were performed during these thirteen nights corresponding to about 47 h of observations. In total 30 uncorrelated faint objects were discov- ered. On average one uncorrelated object was found every 100 min of observations. Some of these objects show a considerable brightness variation and have a high area-to-mass ratio as determined in the orbit estimation process

Assessment of post-manoeuvre observation correlation using short-arc tracklets

Satellites maintain or establish their operational orbit by performing impulsive or continuous thrust maneuvers. When cataloging resident space objects, these rapid or slow orbital changes complicate a successful correlation. The new orbit remains uncertain and cannot be used for operations such as conjunction detection. This work outlines and assesses a method for the correlation of optical tracklets to already cataloged objects and the following orbit recovery. For that purpose, historic orbital data is analyzed to predict possible states after the maneuver using kernel density estimation. The resulting probability density function also provides a measure for the association likelihood of a new tracklet. The methods are tested with optical observations from the Zimmerwald observatory. Maneuver information and ephemerides are reported by the satellite operator and used as a reference

Improved Space Object Orbit Determination Using CMOS Detectors

CMOS-sensors, or in general Active Pixel Sensors (APS), are rapidly replacing CCDs in the consumer camera market. Due to significant technological advances during the past years these devices start to compete with CCDs also for demanding scientific imaging applications, in particular in the astronomy community. CMOS detectors offer a series of inherent advantages compared to CCDs, due to the structure of their basic pixel cells, which each contains their own amplifier and readout electronics. The most prominent advantages for space object observations are the extremely fast and flexible readout capabilities, feasibility for electronic shuttering and precise epoch registration,and the potential to perform image processing operations on-chip and in real-time. Here, the major challenges and design drivers for ground-based and space-based optical observation strategies for objects in Earth orbit have been analyzed. CMOS detector characteristics were critically evaluated and compared with the established CCD technology, especially with respect to the above mentioned observations. Finally, we simulated several observation scenarios for ground- and space-based sensor by assuming different observation and sensor properties. We will introduce the analyzed end-to-end simulations of the ground- and spacebased strategies in order to investigate the orbit determination accuracy and its sensitivity which may result from different values for the frame-rate, pixel scale, astrometric and epoch registration accuracies. Two cases were simulated, a survey assuming a ground-based sensor to observe objects in LEO for surveillance applications, and a statistical survey with a space-based sensor orbiting in LEO observing small-size debris in LEO. The ground-based LEO survey uses a dynamical fence close to the Earth shadow a few hours after sunset. For the space-based scenario a sensor in a sun-synchronous LEO orbit, always pointing in the anti-sun direction to achieve optimum illumination conditions for small LEO debris was simulated

Assessment of post-maneuver observation correlation using short-arc tracklets

Satellites maintain or establish their operational orbit by performing impulsive or continuous thrust maneuvers. When cataloging resident space objects, these rapid or slow orbital changes complicate a successful correlation. The new orbit remains uncertain and cannot be used for operations such as conjunction detection. This work outlines and assesses a method for the correlation of optical tracklets to already cataloged objects and the following orbit recovery. For that purpose, historic orbital data is analyzed to predict possible states after the maneuver using kernel density estimation. The resulting probability density function also provides a measure for the association likelihood of a new tracklet. The methods are tested with optical observations from the Zimmerwald observatory. Maneuver information and ephemerides are reported by the satellite operator and used as a reference

ESA optical surveys to characterize recent fragmentation events in GEO and HEO

Two major fragmentation events in GEO and HEO were observed in 2018. Based on measurements of the International Scientific Optical Network (ISON) and the Roscosmos Automated Warning System on Hazardous Situations in Outer Space (ASPOS OKP) a fragmentation of the Titan 3C Transtage 1969-013B, SSN #3692 on February 28, 2018 was identified. More than 150 objects detected by optical instruments operated by ASPOS OKP, the Astronomical Scientific Center, ISON, ISTP RAS and other Russian scientific and research organizations could be clearly identified as fragmentation debris related to this event. Another massive fragmentation event in HEO related to the Atlas Centaur upper stage 2014-055B, SSN #40209, which occurred on August 30, was identified based on the same data sources. Many of the fragment of this event are crossing the operational GEO region. ESA performed a coordinated survey campaign in October 2018 using its 1-m telescope at the OGS, Tenerife, complemented by sensors of the Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald, Switzerland. The paper will describe the development of the survey strategy to search for additional fragments of the two mentioned events, the execution of the actual observation campaign including the handover of newly discovered objects to other sensors and the subsequent follow-up observations, and the main results of and lessons learned from this campaign