Masking and Tracklet Building for Space Debris and NEO Observations: The Slovak Image Processing Pipeline

Masking and Tracklet Building for Space Debris and NEO Observations: The Slovak Image Processing Pipeline

Stanislav Krajčovič (Comenius University, Slovakia), Roman Ďurikovič (Comenius University, Slovakia) and Jiří Šilha (Comenius University, Slovakia)
DOI: 10.4018/978-1-7998-4444-0.ch003
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Abstract

The partial goal of the transformation of a newly acquired telescope into a professional observation device was a design and development of an image processing pipeline. The pipeline can process an acquired raw image of space debris into object observations in time (tracklets), and further correlate and identify them with selected catalogues. The system contains nine image processing elements (IPEs) in total that are further described in this chapter and have already been deployed and tested on real space debris data.
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Introduction

Comenius University in Bratislava has acquired a 70 cm Newton telescope (see Figure 1) to set up in its Astronomical and Geophysical Observatory in Modra, Slovakia (further AGO), to observe space debris and other near-Earth objects. The set-up of this observational device consisted of many critical steps such as transportation of the telescope, installation in the cupola, installation of the telescope, acquisition of the necessary computing hardware, such as control unit, encoders, and other equipment, and the development of software (Šilha et al., 2018). As of writing of this chapter, it contains 9 Image Processing Elements (further IPEs):

  • star field identification,

  • image reduction,

  • background estimation and subtraction,

  • objects search and centroiding,

  • astrometric reduction,

  • masking,

  • tracklet building,

  • object identification and

  • data transformation.

The focus of this chapter will be on the description of two specific IPEs – masking and tracklet building.

Figure 1.

AGO70 telescope set up in its dome at Astronomical and Geophysical Observatory in Modra, Slovakia, belonging to the Comenius University Bratislava

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Background

The term space debris encompasses all man-made objects which no longer serve any purpose on the Earth’s orbit (Klinkrad, 2006). Large objects orbiting around the Earth belong to this category, such as defunct satellites, rocket bodies used as heavy duty propellers, gloves lost by astronauts during planned spacewalks and other; small objects such as paint flakes, Westford needles, fuel slag, or other (Klinkrad, 2006).

The risk of space debris has risen the moment humanity has become active in space exploration.

The spacecrafts rarely returned back to the Earth. It was more cost-effective to provide fuel only for the outbound journey and leave the unmanned satellites on their former orbit or move them to farther orbits at the end of its life (such as the graveyard orbit). In the same manner, rocket bodies decoupled at higher altitudes are not being actively “cleaned up.” As a result, this led to the increase of space debris population which poses risk to the currently ran missions (ISS manoeuvres to move it out of the trajectory of incoming space debris) as well as for the future missions. Likewise, in the event of re-entry, a sufficiently large object which does not burn up in the atmosphere poses a danger to human lives – should it impact a populated area. Even though many objects are designed to burn up in the atmosphere or re-enter it at the end of their mission due to new regulations, the first step in understanding of the existing space debris is knowing where it comes from.

The biggest contributor of the space debris are fragmentation events which produce debris of various sizes (millimetres to metres). Reasons for fragmentation might be explosions of a satellite because of leftover fuel, damaged pressure tanks, collision with other satellite/debris or even deliberate destruction (Klinkrad, 2006). On the other side of the spectrum, each taking around 10% of the whole population, there is mission-related debris (such as the aforementioned gloves, a screwdriver, and other equipment) and the rocket bodies. An interesting, however small, subset of space debris population is anomalous debris – objects which usually have high area to mass ratio and their origin is not yet known.

Key Terms in this Chapter

AGO70: A 70-cm Newton mount telescope with a CCD camera and BVRI filters capable of deep sky as well as low-Earth orbit observations.

AGO: Astronomical and Geophysical Observatory in Modra, Slovakia, belonging to the Comenius University in Bratislava, Slovakia; it contains known telescopes such as All-Sky Meteor System (AMOS), AGO70, or a 60-cm telescope.

Tracklet: Collection of at least four consecutive observations in time.

IPS: Image processing system, the whole space debris observations processing software package uniting all IPEs to work in coordinated way.

NEA: Near-Earth asteroids; asteroids which have their orbits placed closed to Earth.

Molniya: A highly elliptical orbit used for telecommunication, weather monitoring, and other purposes used historically mainly by Russian Molniya satellites (hence the name).

GEO: Geostationary orbit; orbit on which the satellites match their orbit velocities with Earth’s rotation.

Astrometry: Scientific discipline to measure and compute celestial objects’ positions and movements.

IPE: Image processing module, a single self-sufficient and modular unit for partial space debris observations processing.

FITS: Flexible image transport system; an image format used to transfer images/data between different entities.

GNSS: Global navigation satellite system; an established orbit used for GPS satellites.

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