GRACE and GRACE-FO Level-1 V04 Data Processing Status

2020 ◽  
Author(s):  
Christopher Mccullough ◽  
Tamara Bandikova ◽  
William Bertiger ◽  
Carmen Boening ◽  
Sung Byun ◽  
...  
Keyword(s):  
Data Processing ◽  
Attitude Determination ◽  
Precise Orbit Determination ◽  
Mass Change ◽  
Sensor Data ◽  
The Earth ◽  
Analysis Center ◽  
Level 1 ◽  
Gravity Recovery

<p>The Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), launched in May 2018, provides invaluable information about mass change in the Earth system, continuing the legacy of GRACE. Fundamental requirements for successful mass change recovery are precise orbit determination and inter-satellite ranging, determination of the relative clock alignment of the ultra-stable oscillators (USOs), precise attitude determination, and accelerometry. NASA/Caltech Jet Propulsion Laboratory is the official Level-1 data processing and analysis center, and is currently processing software version 04. Here we present analysis of the aforementioned GRACE-FO sensor data, as well a preview of an upcoming GRACE reprocessing, and a discussion of measurement performance.</p>

V04 Level-1 data processing status for GRACE and GRACE Follow-On

2020 ◽  
Author(s):  
Tamara Bandikova ◽  
Hui Ying Wen ◽  
Meegyeong Paik ◽  
William Bertiger ◽  
Mark Miller ◽  
...  
Keyword(s):  
Data Processing ◽  
Gravity Field ◽  
Attitude Determination ◽  
Precise Orbit Determination ◽  
Sensor Data ◽  
Satellite Mission ◽  
Gravity Field Recovery ◽  
Grace Data ◽  
Level 1 ◽  
Gravity Recovery

<p>On May 22, 2020, the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO), will celebrate two years of successful in-orbit operation. The primary goal of this satellite mission is to provide information about time variations of the Earth’s gravity field. This is possible due to precise orbit determination and inter-satellite ranging by determining the relative clock alignment of the USOs, precise attitude determination and accelerometry. High quality satellite observations are one of the fundamental requirements for successful gravity field recovery. NASA/Caltech Jet Propulsion Laboratory is the official Level-1 data processing and analysis center. The GRACE-FO Level-1 data are currently being processed with software version V04. This software will be used also for final reprocessing of the GRACE (2002-2017) Level-1 data. Here we present the analysis of two years of GRACE-FO sensor data as well as a preview of the reprocessed GRACE data, and discuss the measurement performance.</p>

The Galileo satellites DORESA and MILENA and their goals in the field of Fundamental Physics within the Galileo for Science (G4S_2.0) project

2021 ◽  
Author(s):  
David Lucchesi ◽  
Emiliano Fiorenza ◽  
Carlo Lefevre ◽  
Marco Lucente ◽  
Carmelo Magnafico ◽  
...  
Keyword(s):  
Precise Orbit Determination ◽  
General Introduction ◽  
High Eccentricity ◽  
Accurate Analysis ◽  
Fundamental Physics ◽  
The Earth ◽  
Space Agency ◽  
Italian Space Agency ◽  
Project Objectives

<p>The G4S_2.0 (Galileo for Science) project is a new proposal funded by the Italian Space Agency (ASI) and aims to perform a set of measurements in the field of Fundamental Physics with the two Galileo satellites DORESA and MILENA. Indeed, the accurate analysis of the orbits of these satellites — characterized by a relatively high eccentricity of about 0.16 — and of their clocks — the most accurate orbiting the Earth — allows to test relativistic gravity by comparing the predictions of Einstein's theory of General Relativity with those of other theories of gravitation. After a general introduction to the project objectives, we will present the preliminary activities of G4S_2.0 which are being developed by IAPS-INAF in Rome. The results of G4S_2.0 will be particularly useful for the applications of the Galileo FOC satellites in the fields of space geodesy and geophysics as some of these activities will concern the improvement of the precise orbit determination of the satellites through an enhancement of the dynamic model of their orbits, analyzing, in particular, the modelling of non-conservative forces.</p>

scholarly journals In-Orbit Attitude Determination of the UVSQ-SAT CubeSat Using TRIAD and MEKF Methods

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7361
Author(s):  
Adrien Finance ◽  
Christophe Dufour ◽  
Thomas Boutéraon ◽  
Alain Sarkissian ◽  
Antoine Mangin ◽  
...  
Keyword(s):  
Attitude Determination ◽  
Spacecraft Attitude ◽  
Small Satellite ◽  
Infrared Sensors ◽  
High Quantum Efficiency ◽  
Small Satellites ◽  
The Earth ◽  
Spatio Temporal ◽  
Better Than

Ultraviolet and infrared sensors at high quantum efficiency on-board a small satellite (UVSQ-SAT) is a CubeSat dedicated to the observation of the Earth and the Sun. This satellite has been in orbit since January 2021. It measures the Earth’s outgoing shortwave and longwave radiations. The satellite does not have an active pointing system. To improve the accuracy of the Earth’s radiative measurements and to resolve spatio-temporal fluctuations as much as possible, it is necessary to have a good knowledge of the attitude of the UVSQ-SAT CubeSat. The attitude determination of small satellites remains a challenge, and UVSQ-SAT represents a real and unique example to date for testing and validating different methods to improve the in-orbit attitude determination of a CubeSat. This paper presents the flight results of the UVSQ-SAT’s attitude determination. The Tri-Axial Attitude Determination (TRIAD) method was used, which represents one of the simplest solutions to the spacecraft attitude determination problem. Another method based on the Multiplicative Extended Kalman Filter (MEKF) was used to improve the results obtained with the TRIAD method. In sunlight, the CubeSat attitude is determined at an accuracy better than 3° (at one σ) for both methods. During eclipses, the accuracy of the TRIAD method is 14°, while it reaches 10° (at one σ) for the recursive MEKF method. Many future satellites could benefit from these studies in order to validate methods and configurations before launch.

scholarly journals Comparison of accelerometer data calibration methods used in thermospheric neutral density estimation

2018 ◽  
Vol 36 (3) ◽  
pp. 761-779 ◽  
Author(s):  
Kristin Vielberg ◽  
Ehsan Forootan ◽  
Christina Lück ◽  
Anno Löcher ◽  
Jürgen Kusche ◽  
...  
Keyword(s):  
Solar Activity ◽  
Radiation Pressure ◽  
Precise Orbit Determination ◽  
High Solar Activity ◽  
Neutral Density ◽  
Accelerometer Data ◽  
The Earth ◽  
Calibration Methods ◽  
Leo Satellites ◽  
Gravity Recovery

Abstract. Ultra-sensitive space-borne accelerometers on board of low Earth orbit (LEO) satellites are used to measure non-gravitational forces acting on the surface of these satellites. These forces consist of the Earth radiation pressure, the solar radiation pressure and the atmospheric drag, where the first two are caused by the radiation emitted from the Earth and the Sun, respectively, and the latter is related to the thermospheric density. On-board accelerometer measurements contain systematic errors, which need to be mitigated by applying a calibration before their use in gravity recovery or thermospheric neutral density estimations. Therefore, we improve, apply and compare three calibration procedures: (1) a multi-step numerical estimation approach, which is based on the numerical differentiation of the kinematic orbits of LEO satellites; (2) a calibration of accelerometer observations within the dynamic precise orbit determination procedure and (3) a comparison of observed to modeled forces acting on the surface of LEO satellites. Here, accelerometer measurements obtained by the Gravity Recovery And Climate Experiment (GRACE) are used. Time series of bias and scale factor derived from the three calibration procedures are found to be different in timescales of a few days to months. Results are more similar (statistically significant) when considering longer timescales, from which the results of approach (1) and (2) show better agreement to those of approach (3) during medium and high solar activity. Calibrated accelerometer observations are then applied to estimate thermospheric neutral densities. Differences between accelerometer-based density estimations and those from empirical neutral density models, e.g., NRLMSISE-00, are observed to be significant during quiet periods, on average 22 % of the simulated densities (during low solar activity), and up to 28 % during high solar activity. Therefore, daily corrections are estimated for neutral densities derived from NRLMSISE-00. Our results indicate that these corrections improve model-based density simulations in order to provide density estimates at locations outside the vicinity of the GRACE satellites, in particular during the period of high solar/magnetic activity, e.g., during the St. Patrick's Day storm on 17 March 2015.

Processing of GRACE-FO satellite-to-satellite tracking data using the GRACE-SIGMA software

2020 ◽  
Author(s):  
Igor Koch ◽  
Mathias Duwe ◽  
Jakob Flury ◽  
Akbar Shabanloui
Keyword(s):  
Laser Ranging ◽  
Satellite Measurements ◽  
Satellite Mission ◽  
The Earth ◽  
Gravity Fields ◽  
Data Products ◽  
Level 1 ◽  
Orbit Types ◽  
Gravity Recovery

<p>The dual-satellite mission GRACE Follow-On (GRACE-FO) was launched in May 2018 as the successor of the Gravity Recovery And Climate Experiment (GRACE). In May 2019 first level 1 data products were made available to the community and are now published regularly. These products, among others, include orbits, accelerometer measurements, star camera data and micron and sub-micron precise inter-satellite range measurements. The data products are used by different groups to compute estimates of monthly gravity fields of the Earth. The in-house developed GRACE-SIGMA software is used at the Institut of Geodesy/Leibniz University Hannover for the estimation of monthly gravity fields. Several parts of the software’s processing chain, such as background modeling, were updated recently and different parametrization scenarios were tested. First solutions were estimated based on laser ranging interferometer measurements. Moreover, different orbit types, such as reduced-dynamic and kinematic, were tested. In this contribution, we present the influence of these updates and tests on the quality of the gravity fields. The obtained solutions are assessed in terms of error degree standard deviations and post-fit residuals of the inter-satellite measurements.</p>

HADIS KURAIB DALAM KONSEP RUKYATUL HILAL

1970 ◽  
Vol 13 (2) ◽  
Author(s):  
Muslih Husein
Keyword(s):  
The West ◽  
The Earth ◽  
New Moon ◽  
The Republic

Hisab dan rukyat, hakikatnya, adalah cara untuk mengetahui pergantian bulan. Kajian ini memperlihatkan beberapa temuan. Pertama, korelasi antara hadis Kuraib dan terjadinya perbedaan penetapan awal Ramadan, Syawal, dan Dzul Hijjah di Indonesia. Kementerian Agama Republik Indonesia telah menetapkan bahwa Indonesia secara keseluruhan menjadi satu wilayah hukum (wilayatul hukmi). Kedua, tentang keberhasilan rukyat al-hilal di satu kawasan yang diberlakukan bagi kawasan lain di muka bumi. Perlu diketahui bersama bahwa visibilitas pertama hilal tidak meliputi seluruh muka bumi pada hari yang sama, melainkan membelahnya menjadi dua bagian: (1) bagian sebelah Barat yang dapat melihat hilal dan (2) bagian sebelah Timur yang tidak dapat melihat hilal.Hisab and rukyat is a way to know the turn of the month. This study shows several findings. First is the correlation between Kuraib traditions and differences in the determination of the beginning of Ramadan, Shawwal, and Dhul-Hijjah in Indonesia. Ministry of Religious Affairs of the Republic of Indonesia has stated that Indonesia as a whole into a single jurisdiction (wilayatul hukmi). Second, on the success rukyat alhilal in one area that applied to other regions of earth. Important to know that the first visibility of the new moon does not cover the entire face of the earth on the same day, but splitting it into two parts: (1) part of the West to see the new moon, and (2) part of the East were not able to see the new moon.

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