Wyniki wyszukiwania - BazTech

1

Neural network applied to telescope pointing inaccuracy model

Zhaborovskyy Vitaliy, Medvedsky Myhailo, Choliy Vasyl, Pap Victor, Semenenko Viachelsav

Artificial Satellites : Journal of Planetary Geodesy

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2024

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Vol. 59, No. 2

55--63

EN

In the course of satellite observations using satellite laser ranging (SLR), a key task is pointing the telescope with high precision. Positioning the steering system’s mechanical parts with zero error is impossible. Accordingly, we must analyze and account for pointing errors by incorporating the telescope mounting errors themselves into the modeling error. Such models are far from trivial owing to the factors such as satellite azimuth, altitude, perhaps distance, or meteorological data. In this article, we explain how the data for the telescope pointing inaccuracy model (TIM) was collected and how a neural network was used to build a very precise TIM for the Golisiiv 1824 SLR station in Kyiv. We have focused our efforts on the suggested approach’s positive aspects based on our experience of using it to find practical solutions. Our practical recommendations may also be interesting for anyone working with hardware, especially in analyzing their errors. The key proof of the effectiveness of the approach is the serious increase in the number of satellites successfully tracked, especially for “blind” paths, when the satellite is not visible to the observer through the telescope guide.

2

Close approaches of debris to LARES satellite during its first four years of operation

Paris C., Sindoni G., Sabato T.

Transactions on Environment and Electrical Engineering

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2017

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Vol. 2, No. 1

90--97

EN

Since its launch in February 2012, the LAser RElativity Satellite (LARES) of the Italian Space Agency experienced four close approaches with space debris. LARES orbits at an altitude of 1450 km, in a region where the density of space debris has a peak. However, the probability of an impact with a debris during the operational life of the satellite was reasonably low. The analysis of the close approaches identified three of the objects, that are from two peculiar population of objects. This paper discusses the problem of space debris in low orbit, the approaches occurred with LARES, and some possible scenarios related to space regulations and space law in case of an impact.

3

Determination of the SLR stations coordinates in 1994-2008

Schillak S.

Reports on Geodesy

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2012

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z. 1/92

227-236

EN

The paper presents results of the determination of SLR stations coordinates from the observations of LAGEOS-1 and LAGEOS-2 satellites for 5 years spans from 1994 until 2008. The computations of the station positions were performed by NASA Goddard’s GEODYN-II orbital program with a new models and parameters. The main purpose of this work is estimation of the SLR station position accuracy and its stability in the long time period. The accuracy is presented in the form of the station position stability, range biases and RMS of fit per station. The best results are for the span 1999-2003. In 2004-2008 the results show deterioration in the position accuracy of the several important stations. This effect can be explained by smaller number of normal points for some stations and jumps in the vertical component.

4

International SLR service

Schillak S.

Artificial Satellites : Journal of Planetary Geodesy

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2011

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Vol. 46, No. 4

119--126

EN

The paper presents the current state of the International Laser Ranging Service (ILRS): distribution of the SLR stations, data centers, analysis centers. The paper includes also the information about the last International Workshop on Laser Ranging in Bad Koetzting, 16-20 May, 2011. The problems of quality of the SLR data are presented. The list of parameters which can be used for estimation of the accuracy of the SLR data for each station is given. Results of determination of the station position stabilities over long term period (from 1994 up to 2008) for the selected few main stations are presented in the five years blocks. The results show slight deterioration of accuracy observed for the last several years and the reasons for this effect are indicated.

5

Porównanie wyników wyznaczania współrzędnych technikami GPS i SLR

Schillak S., Lehmann M.

Biuletyn Wojskowej Akademii Technicznej

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2010

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Vol. 59, nr 2

117-134

PL

Przedstawiono wyniki porównania współrzędnych stacji dla dwóch technik satelitarnych: laserowej i GPS. Współrzędne były wyznaczane dla wspólnych momentów w układzie współrzędnych ITRF2005. Porównanie wykonano dla wszystkich stacji wyposażonych w systemy SLR i GPS w okresie jedenastu lat od 1993.0 do 2004.0 bez uwzględnienia stacji laserowych, które zmieniły system w tym czasie. W sumie obliczenia wykonano dla 12 stacji. Współrzędne zostały obliczone dla okresów miesięcznych dla pierwszego dnia każdego miesiąca. Analiza wyników obejmowała ocenę stabilności pozycji stacji, różnice z ITRF2005, porównanie prędkości stacji dla obu technik. Prędkości porównano także z modelem ruchu płyt tektonicznych NNR-NUVEL1A i ITRF2005. Stwierdzono dobrą zgodność pozycji i prędkości stacji dla obu technik. Dla kilku stacji występują znaczne (1-3 cm) różnice w składowej pionowej.

EN

The paper presents results of the comparison of the station positions and velocities between two satellite techniques: Satellite Laser Ranging (SLR) and Global Positioning System (GPS). The coordinates were calculated for common epochs in the International Terrestrial Reference Frame 2005. The comparisons were performed for all stations equipped with the SLR and GPS systems in the period of time from 1993.0 to 2004.0 without SLR stations which changed the system in that time. Finally, calculations were performed for 12 stations. The coordinates were determined for epochs in the first day of each month. The analysis included estimation of the station positions stability, comparison with ITRF2005, station velocities comparison between both techniques. The tectonic plates model NNR-NUVEL1A and ITRF2005 velocities were used for verification of station velocities. Generally, with some exceptions, is a good agreement of the station positions and velocities between results for both techniques. For several stations, significant (1-3 cm) differences between vertical components were detected.

6

Overview and performance of the Ukrainian SLR station “Lviv-1831”

Blagodyr J., Bilinsky A., Martynyuk-Lototsky K., Lohvynenko O., Virun N.

Artificial Satellites : Journal of Planetary Geodesy

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2007

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Vol. 42, No. 1

9--15

EN

The paper presents the current status and performance of the SLR station “Lviv-1831”. The present equipment allows ranging of satellite not lower than 900 km with a single shot precision about 50 mm. The team works over system upgrade and performance improvement. It includes: neutral filters wheel developing for equilibration of the amplitude of reflected pulses from different satellites, building up the shutter in the face of PMT for the spurious light pulses blocking. Also the new adjusting of the telescope optical mechanical systems was made. After that investigation the new telescope error model was built with an accuracy 20arcsec that allowed at the first time test ranging of the “shadowed” satellite passes. In the near future the team will finish installation and testing of the new PMT Hamamatsu H6780. Maiden upgrades should better the performance and ranging accuracy by the factor of 2-3.

7

Construction of telescope inaccuracy model according to data of satellites laser ranging

Medvedsky M. M., Pap V. O.

Artificial Satellites : Journal of Planetary Geodesy

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2006

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Vol. 41, No. 3

105--114

EN

The method of constructing error model of pointing the telescope to the target is present in the article. It bases on using the angular encoders data (azimuth and elevation). This angles are fixed in time in the satellite laser ranging. The data is presented in the codes of angles (in inside frame) and the moments of time, in which they are fixed. The consistence of procedures and result of received model are presented in article. Also advantages and disadvantages of the new model are considered in comparison with the method of stars observers. The method tested on the 40 passes of the satellites. The model constructing in station “Kyiv-Golosiiv” in 2003 year is used for the comparison.[1]. The accuracy of this model is on the level 15 arcsec.