Observation of artificial satellites and space debris

Since the 1950s, humanity has sent thousands of satellites into space. However, they remain in orbit at the end of their lifetime and thus become space junk. And these are not only retired satellites, but also their launch vehicles, fragments and pieces of equipment. The number of space debris objects larger than 1 cm is estimated to be around 750,000. All these objects are a risk to active satellites.
The European Space Agency (ESA) launched the SST (Space Surveillance and Tracking) project just to observe space debris. In this project, data is collected from terrestrial observers, both optical, radio and laser, and their subsequent processing and calculation of trajectories.

Technical equipment of the observatory

Observations are made with the Planewave CDK17 telescope, which is located in the southeast dome. With focal ratio of f/6.8, the telescope has a focal length of 2939 mm, which is usually shortened to 1980 mm with a 0.66× focus reducer, thus achieving a ratio of f/4.6. There is a focuser on the telescope that allows us to focus remotely using a computer.

The telescope is mounted on a 2EL DDF2-EQ-600 fork mount. The assembly was custom made to achieve maximum performance when tracking objects in orbit and can thus capture even the fastest satellites.

In addition, the southeast dome is equipped with a MaxDome device that allows you to control its rotation with a computer.

The KL4040 scientific camera, which has the same resolution and display area as the popular CCD KAF-16803, is used for imaging. The KL4040 camera has one-third the noise and 40% higher efficiency compared to the aforementioned KAF-16803. The cooled camera provides ultra-high sensing sensitivity, low noise and the possibility of very fast sensing. The KL4040 camera is equipped with a GPixel GSense4040 sensor and a “Front Illuminated CMOS” chip. It has 4096 x 4096 active pixels with a size of 9 x 9 μm. The displayed area is 36.8 x 36.8 mm, the total frame rate is 23 fps (QSFP V2).

The control computer is able to synchronize the movement of the telescope and the dome so that the shutter and the telescope always point in the same direction. It is also able to control the mount so that it moves with the satellite and the images in the sequence overlap. The images have high demands on accuracy: 3.6 seconds of arc and 1 millisecond. A local NTP server helps us with time accuracy.

Objects are divided into several categories according to their orbit. These are mainly objects in low Earth orbit (LEO), objects in medium orbits (Medium Earth Orbit, MEO) and geostationary satellites (geostationary Earth orbit, GEO). MEO and GEO type objects move more slowly, so it is possible to capture one object repeatedly at least five times in our CCD camera’s field of view over 1 degree wide, and still track that object as a point. In addition, one “static” reference image of the star field is taken. We can process such measurements automatically with the programme ASAP (Asteroid and Satellite Automatic Processor), which was supplied to us by the Czech company Iguassu Software Systems as part of the project collaboration.

LEO-type objects are very fast and cannot be observed other than as line segments, because even during a short exposure they manage to move through many points of the matrix of our CMOS camera. To measure these objects, we have prepared a computer program, with which the observer individually measures the images on which LEO-type satellites are detected. After measuring the exact positions of the satellites in the sky (equatorial coordinates, i.e. right ascension and declination), it is necessary to combine several measurements of one object in a certain shorter period of time into one file and create a so-called tracklet. These tracklets form separate files in an agreed standard format (TDM) and thus constitute individual concrete results of our efforts. The observation and subsequent processing of one tracklet takes an average of 10 to 20 minutes of one worker’s time.

Results

 

SSA P2-SST-X Support Observations and Sensor Qualification

We participated in this project in the years 2015 – 2017 as a subcontractor for the Italian consortium eGeos. Our goal was the qualification of our telescope, which enables further participation in similar projects.
In 2016, we measured 718 positions of LEO (low orbit) objects and 11,588 positions of MEO and GEO (intermediate and geostationary orbit) objects.
In 2017, we then continued and acquired 318 LEO positions and 3,173 MEO and GEO positions.
By analyzing the measured data, it was found that the average error of our satellite measurements in higher orbits (MEO and GEO) are around 1 arc second, which is sufficient for ESA’s needs. The average errors of our low earth orbit (LEO) satellite measurements are around 5 arcseconds, which is again sufficient for ESA’s needs. Based on this data, ESA has qualified our SHOT telescope as suitable for observing artificial satellites and space debris.

SSA P3-SST-III Robotic Telescopes Demonstration

In 2018, we joined this ESA contract as a subcontractor, which was won by the Czech company Iguassu, with whom we started cooperation under the previous contract. The main goal of this activity was the commissioning of two TBT (Test-Bed Telescope) robotic telescopes owned by ESA and their connection to the network of other robotic telescopes. Our task was to automate our SHOT telescope as much as possible and contribute joint observations within this network in coordinated campaigns that will meet the requirements and goals of ESA. The contract started in May 2018.
Our activities included, in particular, putting the SHOT telescope back into operation after the reconstruction of the observatory, verifying the functionality of all components of our sensor (mounting, telescope, CCD camera, focusing, mirror heating, dome rotation, local NTP server, cloud and weather sensor), increasing the accuracy of observations, creating a new observation automation software. Furthermore, the opening control of the dome slot was motorized.

The observation campaign ran from March to May 2021.

P3-SST-XXII Polish SST Small Telescope Assessment and Prototyped Operations

In 2020, we joined the network of small Polish telescopes in cooperation with the Czech company Iguassu, the test observation campaign took place in November and December 2020. The second observation campaign took place in November and December 2021.

P3-SST-XIX SST Sensor Data Acquisition for Endurance Tests and Validation – Phase 2

A new project launched in 2020 by which ESA verifies the functionality and performance of its systems and involves observatories in test campaigns. We were involved as one of the observatories that observed satellites mainly in geostationary orbit. The project was led by the Institute of Astronomy at the Swiss University of Bern. The calibration campaign took place in January and February, the observation campaign took place in October 2021.

S2P S1-SC-09 – Support of the Development of Sensors, Joint Test and Operation of a European Optical Network

The project, which is being led by the Slovak company Astros Solutions s.r.o. This project joins ESA Slovakia, which is not yet a member of ESA. The project follows on from the aforementioned P3-SST-III Robotic Telescope Demonstration project. November and December saw the calibration of our sensor for this project, which will continue into 2022.

EU SST

Since 2020, we have been actively involved in the new European Union program called EU SST (https://www.eusst.eu/), which is again dedicated to monitoring man-made objects and waste around the Earth. In doing so, we work closely with the Department of Intelligent Transport Systems, Space Activities and R&D of the Ministry of Transport of the Czech Republic. The European Union is interested in the safe operation of its satellites and is therefore creating a program to protect its assets and help the safe use of outer space, thus ensuring the operation of important systems on Earth. The Czech Republic, through the Ministry of Transport of the Czech Republic, is interested in joining the Teplice observatory in the EU SST consortium. The planned start of our contractual cooperation is July 1, 2023.