Wyniki wyszukiwania - BazTech

1

Piecewise acceleration orbital modeling: a GOCE satellite case study

Bobojć Andrzej, Cellmer Sławomir

Acta Geophysica

|

2022

|

Vol. 70, no 1

399--413

EN

In this work, the Precise Science Orbit (PSO) of the Gravity Field and Steady-State Ocean Circulation Explorer Mission (GOCE) satellite, acquired via the European Space Agency, served as the reference orbit for the testing various variants of the GOCE satellite orbit modeling. The GOCE satellite positions along the reduced-dynamic PSO orbit were treated as pseudo-observations in the satellite orbit improvement process in the least squares sense. This process was realized using dedicated extended Toruń Orbit Processor software which enabled determining corrections to the orbital initial conditions and the set of parameters, necessary to determine additional empirical accelerations of the satellite in the radial-track, along track and cross-track directions. These piecewise accelerations were determined in successive equal intervals (pieces) into which the processed orbital arcs were divided. For modeling the accelerations, polynomials of different degrees were used. The obtained RMS differences between the improved orbits and the reference PSO orbit were determined for various orbital arc lengths up to 1-day. The best RMS of the fts for the 1-day arcs was in the range from 2.0 to 3.2 mm with significantly worst results for along-track direction. Based on the set of solutions determined, the number of orbital parameters for adopted accuracy thresholds and the upper limit of their number, that can be estimated depending on the length of the orbital arc, under given numerical conditions were obtained. The optimal form of the polynomial modeling of the estimated accelerations also depends partly on the length of the processed orbital arc. For shorter arcs (45 min and less), the second- third- and fourth-order polynomial gives the best results, while for longer arcs (90, 180, 360, 720 and 1440 min), zero- and first-degree polynomials are the most effective. A very promising solution with the RMS of the ft of 0.1 mm for a 1-min arc using the fourth-order polynomial was obtained in a perspective of the future use of the short arc approach to the ft of 1-day arcs. Additionally, solution variants with non-equal numbers of orbital pieces for the radial-along-and cross-track directions were obtained. In the case of the solution for an arc length of 1-day, the distribution of residuals and their statistics in the aforementioned radial-, along-and cross-track directions are presented.

2

Validation of recent geopotential models in Tierra Del Fuego

Gomez M. E., Perdomo R., Cogliano D.

Acta Geophysica

|

2017

|

Vol. 65, no. 5

931--943

EN

This work presents a validation study of global geopotential models (GGM) in the region of Fagnano Lake, located in the southern Andes. This is an excellent area for this type of validation because it is surrounded by the Andes Mountains, and there is no terrestrial gravity or GNSS/levelling data. However, there are mean lake level (MLL) observations, and its surface is assumed to be almost equipotential. Further-more, in this article, we propose improved geoid solutions through the Residual Terrain Modelling (RTM) approach. Using a global geopotential model, the results achieved allow us to conclude that it is possible to use this technique to extend an existing geoid model to those regions that lack any information (neither gravimetric nor GNSS/levelling observations). As GGMs have evolved, our results have improved progressively. While the validation of EGM2008 with MLL data shows a standard de-viation of 35 cm, GOCO05C shows a deviation of 13 cm, similar to the results obtained on land.

3

Accurate Establishment of Error Models for the Satellite Gravity Gradiometry Recovery and Requirements Analysis for the Future GOCE Follow-On Mission

Zheng W., Wang Z., Ding Y., Li Z.

Acta Geophysica

|

2016

|

Vol. 64, no. 3

732--754

EN

Firstly, the new single and combined error models applied to estimate the cumulative geoid height error are efficiently produced by the dominating error sources consisting of the gravity gradient of the satellite-equipped gradiometer and the orbital position of the space-borne GPS/GLONASS receiver using the power spectral principle. At degree 250, the cumulative geoid height error is 1.769 × 10–1 m based on the new combined error model, which preferably accords with a recovery accuracy of 1.760 × 10–1 m from the GOCE-only Earth gravity field model GO_CONS_GCF_2_TIM_R2 released in Germany. Therefore, the new combined error model of the cumulative geoid height is correct and reliable in this study. Secondly, the requirements analysis for the future GOCE Follow-On satellite system is carried out in respect of the preferred design of the matching measurement accuracy of key payloads comprising the gravity gradient and orbital position and the optimal selection of the orbital altitude of the satellite. We recommend the gravity gradient with an accuracy of 10–13-10–15 /s2 , the orbital position with a precision of 1-0.1 cm and the orbital altitude of 200-250 km in the future GOCE Follow-On mission.

4

Accuracy assessment of GOCE-based geopotential models and their use for modelling the gravimetric quasigeoid - A case study for Poland

Godah W., Szelachowska M., Krynski J.

Geodesy and Cartography

|

2014

|

Vol. 63, no. 1

3--24

EN

The GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) has significantly upgraded the knowledge on the Earth gravity field. In this contribution the accuracy of height anomalies determined from Global Geopotential Models (GGMs) based on approximately 27 months GOCE satellite gravity gradiometry (SGG) data have been assessed over Poland using three sets of precise GNSS/levelling data. The fits of height anomalies obtained from 4th release GOCE-based GGMs to GNSS/levelling data were discussed and compared with the respective ones of 3rd release GOCE-based GGMs and the EGM08. Furthermore, two highly accurate gravimetric quasigeoid models were developed over the area of Poland using high resolution Faye gravity anomalies. In the first, the GOCE-based GGM was used as a reference geopotential model, and in the second – the EGM08. They were evaluated with GNSS/levelling data and their accuracy performance was assessed. The use of GOCE-based GGMs for recovering the long-wavelength gravity signal in gravimetric quasigeoid modelling was discussed.

PL

Misja GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) przyczyniła się do znacznego poprawienia znajomości pola siły ciężkości Ziemi. W artykule przedstawiono wyniki oszacowania dokładności anomalii wysokości, wyznaczonych z globalnych modeli geopotencjału opracowanych na podstawie blisko 27 miesięcy pomiarów z satelitarnej misji gradiometrycznej GOCE. Do oszacowania wykorzystano trzy zbiory dokładnych danych satelitarno-niwelacyjnych z obszaru Polski. Omówiono wyniki wpasowania wartości anomalii wysokości otrzymanych z czwartej wersji globalnych modeli geopotencjału wyznaczonych na podstawie danych misji GOCE do danych satelitarno-niwelacyjnych oraz porównano je z wynikami odpowiedniego wpasowania trzeciej wersji globalnych modeli geopotencjału otrzymanych z GOCE oraz z modelu EGM08. Ponadto, wykorzystując wysokorozdzielczy zbiór grawimetrycznych anomalii Faye’a, wyznaczono dla obszaru Polski dwa grawimetryczne modele quasigeoidy o wysokiej dokładności. W pierwszym przypadku jako model referencyjny użyto model utworzony na podstawie danych z misji GOCE, w drugim – model EGM08. Wygenerowane modele quasigeoidy porównano z danymi satelitarno-niwelacyjnymi oraz oszacowano ich dokładność. Omówiono przydatność otrzymanych na podstawie danych z misji GOCE globalnych modeli geopotencjału do odtworzenia długofalowego sygnału grawimetrycznego przy modelowaniu grawimetrycznej quasigeoidy.

5

Rosborough formulation in satellite gravity gradiometry

Sharifi M. A., Safari A., Far K. G.

Artificial Satellites : Journal of Planetary Geodesy

|

2013

|

Vol. 48, No. 1

39--50

EN

Following the launch of CHAMP, a new era was born in the gravity field determination from satellite observations. Many methods have been proposed and applied for the recovery of the Earth’s gravity field from the observations of the satellite missions CHAMP, GRACE and GOCE. This paper deals with the Rosborough formulation in gravity field modelling. This formulation is derived from the transformation of time-wise representation from the orbital into the spherical coordinate systems. Base functions of the Rosborough formulation depend on the type of the functional of the gravity field and the inclination of the orbit. Unlike the space-wise approach, the Rosborough approach can easily deal with both isotropic and non-isotropic functionals. The proposed formulation is implemented on the GOCE data in order to show its efficiency. Numerical results show that the Rosborough formulation is a powerful and efficient tool in the case of GOCE gradiometry data processing.

6

Validation of GOCE gravity field models over Poland using the EGM2008 and GPS/levelling data

Godah W., Kryński J.

Geoinformation Issues

|

2011

|

Vol. 3, no. 1(3)

5-17

EN

Since the mid of 2010, global geopotential models based on GOCE mission data became available. The first two releases of GGMs contained four different solutions while in the third release only two solutions have been generated. In the presented study the available GOCE-derived gravity field models were evaluated in terms of height anomalies and gravity anomalies over Poland with the use of the respective functionals calculated from the EGM2008 geopotential model as well as height anomalies at 184 stations of high precision GPS/levelling control traverse. The fit of GOCE gravity field models with the EGM2008 in terms of height anomalies and gravity anomalies measured with a standard deviation is below 10 cm, and 3 mGal, respectively. Their fit with GPS/levelling height anomalies at the stations of GPS/levelling control traverse is at the level of 10 cm. The results obtained indicate some improvement of the consecutive releases of GOCE gravity field models.

PL

Od połowy 2010 roku są udostępnione globalne modele geopotencjału opracowane na podstawie danych z misji GOCE. Pierwsze dwie generacje modeli geopotencjału z misji GOCE zawierały cztery różne rozwiązania podczas gdy trzecia - składała się zaledwie z dwóch rozwiązań. Jakość dostępnych modeli pola siły ciężkości z misji GOCE została w niniejszym opracowaniu oceniona w wyniku porównania obliczonych z nich anomalii wysokości i anomalii grawimetrycznych z odpowiednimi funkcjonałami obliczonymi z modelu geopotencjału EGM2008 oraz z anomaliami wysokości 184 stacji precyzyjnego satelitarno-niwelacyjnego trawersu kontrolnego. Odchylenia standardowe różnic anomalii wysokości i anomalii grawimetrycznych pomiędzy uzyskanymi z opracowanych na podstawie danych z misji GOCE modeli geopotencjału i z modelu EGM2008 wynoszą odpowiednio 10 cm i 3 mGal. Dopasowanie modeli geopotencjału z misji GOCE do anomalii wysokości satelitarno- niwelacyjnego trawersu kontrolnego kształtuje się również na poziomie 10 cm. Uzyskane wyniki wskazują na poprawę w kolejnych generacjach modeli geopotencjału z misji GOCE.

7

GOCE

Królikowski J.

Geodeta : magazyn geoinformacyjny

|

2009

|

nr 4

8-9

8

Misja przyszłości - GOCE

Alberska A.

Przegląd Geodezyjny

|

2007

|

R. 79, nr 4

3-5

PL

W artykule opisana jest satelitarna misja GOCE (Gravity Field and Steady-State Ocean Circulation Explorer), zaprojektowana przez Europejską Agencję Kosmiczną ESA i przygotowana do realizacji w roku 2007. W artykule opisano eksperymenty naukowe, mające na celu badanie pola grawitacyjnego Ziemi metodami gradientometrycznymi.

EN

Satellite mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) designed and prepared by the European Space Agency ESA for launching in 2007 is described in the paper. Scientific experiments aiming at determination of the Earth gravity field by gradientometric methods are described in the paper.