Neutral Density Measurements from the Gravity Recovery and Climate Experiment Accelerometers

2007 ◽  
Vol 44 (6) ◽  
pp. 1220-1225 ◽  
Author(s):  
Byron D. Tapley ◽  
John C. Ries ◽  
Srinivas Bettadpur ◽  
Minkang Cheng
Keyword(s):  
Neutral Density ◽  
Density Measurements ◽  
Gravity Recovery

Neutral Density Measurements by Charge Exchange Analysis on the Heliotron E Plasma

1983 ◽  
Vol 52 (12) ◽  
pp. 4166-4175 ◽  
Author(s):  
Yousuke Nakashima ◽  
Hideki Zushi ◽  
Kiyoshi Hanatani ◽  
Katsumi Kondo ◽  
Akihiko Sasaki ◽  
...  
Keyword(s):  
Charge Exchange ◽  
Neutral Density ◽  
Density Measurements

scholarly journals Outer midplane neutral density measurements and H-mode fueling studies in NSTX-U

2021 ◽  
Vol 61 (3) ◽  
pp. 036002
Author(s):  
F. Scotti ◽  
D.P. Stotler ◽  
R.E. Bell ◽  
B.P. LeBlanc ◽  
S.A. Sabbagh ◽  
...  
Keyword(s):  
Neutral Density ◽  
Density Measurements

Scale factors of the thermospheric neutral density – a comparison of SLR and accelerometer solutions

2021 ◽  
Author(s):  
Lea Zeitler ◽  
Armin Corbin ◽  
Kristin Vielberg ◽  
Sergei Rudenko ◽  
Anno Löcher ◽  
...  
Keyword(s):  
Time Resolution ◽  
Aerodynamic Drag ◽  
Precise Orbit Determination ◽  
Neutral Density ◽  
Observation Data ◽  
Accelerometer Data ◽  
Scale Factors ◽  
Weather Events ◽  
Leo Satellites ◽  
Gravity Recovery

<p>The aerodynamic drag depending on the neutral density of the thermosphere is the largest non-gravitational force that decelerates Low Earth Orbiting (LEO) satellites with altitudes lower than 1000 km.  Consequently, the knowledge of the thermospheric neutral density is of crucial importance for many applications in geo-scientific investigations, such as precise orbit determination (POD), re-entry prediction, manoeuvre planning or satellite lifetime predictions. The accuracy of existing thermosphere models depends on observation data of the thermosphere, which are quite sparse. Evaluations of different thermosphere models indicate considerable differences, especially for time epochs of severe space weather events. Hence, an improvement of thermosphere models is absolutely necessary.</p><p>In this study, discrepancies between the empirical thermosphere model NRLMSISE-00 and the results of two geodetic observation techniques are discussed. For this purpose, two approaches are applied to calculate scale factors between the modelled density from the NRLMSISE-00 model and those from geodetic techniques. The first approach applies the POD of LEO satellites to estimate scale factors with a time resolution of 12 hours derived from Satellite Laser Ranging (SLR) tracking measurements. The SLR missions used here include the spherical satellites Starlette, Westpac, Blits, Stella and Larets. As our second approach, scale factors are computed by evaluating the aerodynamic acceleration using the on-board accelerometer data of the Challenging Mini-satellite Payload (CHAMP) mission and the Gravity Recovery and Climate Experiment (GRACE) mission. Here, the time resolution of scale factors is fixed to be 12 hours to be comparable with the first approach. Finally, we investigate the resulting scale factors from the above mentioned satellites at various altitudes, e.g. 960 km for Starlette and 400 km for GRACE. Especially, the temporal variation as well as the altitude dependency of the scale factors will be discussed.</p>

scholarly journals Intercalibration of neutral density measurements for mapping the thermosphere

2016 ◽  
Vol 121 (6) ◽  
pp. 5975-5990 ◽  
Author(s):  
D. R. Weimer ◽  
E. K. Sutton ◽  
M. G. Mlynczak ◽  
L. A. Hunt
Keyword(s):  
Neutral Density ◽  
Density Measurements

Neutral density measurements in doublet III

1982 ◽  
Vol 20 (4) ◽  
pp. 1222-1225 ◽  
Author(s):  
J. S. deGrassie ◽  
J. C. DeBoo ◽  
M. A. Mahdavi ◽  
N. Ohyabu ◽  
M. Shimada
Keyword(s):  
Neutral Density ◽  
Density Measurements

A simultaneous calibration and data assimilation (C/DA) to improve NRLMSISE00 using thermospheric neutral density (TND) from space-borne accelerometer measurements

2020 ◽  
Vol 224 (2) ◽  
pp. 1096-1115
Author(s):  
E Forootan ◽  
S Farzaneh ◽  
M Kosary ◽  
M Schmidt ◽  
M Schumacher
Keyword(s):  
Kalman Filter ◽  
Data Assimilation ◽  
Precise Orbit Determination ◽  
Low Earth Orbit ◽  
Model Parameters ◽  
Neutral Density ◽  
Incoherent Scatter ◽  
Drag Forces ◽  
Gravity Recovery ◽  
Limited Accuracy

SUMMARY Improving thermospheric neutral density (TND) estimates is important for computing drag forces acting on low-Earth-orbit (LEO) satellites and debris. Empirical thermospheric models are often used to compute TNDs for the precise orbit determination experiments. However, it is known that simulating TNDs are of limited accuracy due to simplification of model structure, coarse sampling of model inputs and dependencies to the calibration period. Here, we apply TND estimates from accelerometer measurements of the Challenging Minisatellite Payload (CHAMP) and the Gravity Recovery and Climate Experiment (GRACE) missions as observations to improve the NRLMSISE-00 model, which belongs to the mass spectrometer and incoherent scatter family of models. For this, a novel simultaneous calibration and data assimilation (C/DA) technique is implemented that uses the ensemble Kalman filter and the ensemble square-root Kalman filter as merger. The application of C/DA is unique because it modifies both model-derived TNDs, as well as the selected model parameters. The calibrated parameters derived from C/DA are then used to predict TNDs in locations that are not covered by CHAMP and GRACE orbits, and forecasting TNDs of the next day. The C/DA is implemented using daily CHAMP- and/or GRACE-TNDs, for which compared to the original model, we find 27 per cent and 62 per cent reduction of misfit between model and observations in terms of root mean square error and Nash coefficient, respectively. These validations are performed using the observations along the orbital track of the other satellite that is not used in the C/DA during 2003 with various solar activity. Comparisons with another empirical model, that is, Jacchia-Bowman, indicate that the C/DA results improve these quality measurements on an average range of 50 per cent and 60 per cent, respectively.

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