scholarly journals Retrieval of vertical profiles of atmospheric refraction angles by inversion of optical dilution measurements

2015 ◽  
Vol 8 (8) ◽  
pp. 3135-3145 ◽  
Author(s):  
D. Fussen ◽  
C. Tétard ◽  
E. Dekemper ◽  
D. Pieroux ◽  
N. Mateshvili ◽  
...  
Keyword(s):  
Low Earth Orbit ◽  
Vertical Profiles ◽  
Atmospheric Refraction ◽  
Satellite Mission ◽  
Image Deformation ◽  
Satellite Attitude ◽  
Accurate Knowledge ◽  
Celestial Bodies ◽  
Low Earth Orbit Satellites ◽  
Absolute Knowledge

Abstract. In this paper, we consider occultations of celestial bodies through the atmospheric limb from low Earth orbit satellites and we show how the usual change of tangent altitude associated with atmospheric refraction is inseparably connected to a variation of the observed apparent intensity, for extended and pointlike sources. We demonstrate, in the regime of weak refraction angles, that atmospheric optical dilution and image deformation are strictly concomitant. The approach leads to the integration of a simple differential equation related to the observed transmittance in the absence of other absorbing molecules along the optical path. The algorithm does not rely on the absolute knowledge of the radiometer pointing angle that is related to the accurate knowledge of the satellite attitude. We successfully applied the proposed method to the measurements performed by two past occultation experiments: GOMOS for stellar and ORA for solar occultations. The developed algorithm (named ARID) will be applied to the imaging of solar occultations in a forthcoming pico-satellite mission.

scholarly journals Retrieval of vertical profiles of atmospheric refraction angles by inversion of optical dilution measurements

2015 ◽  
Vol 8 (4) ◽  
pp. 3571-3603
Author(s):  
D. Fussen ◽  
C. Tétard ◽  
E. Dekemper ◽  
D. Pieroux ◽  
N. Mateshvili ◽  
...  
Keyword(s):  
Differential Equation ◽  
Optical Path ◽  
Vertical Profiles ◽  
Atmospheric Refraction ◽  
Satellite Mission ◽  
Image Deformation

Abstract. In this paper, we show how the usual change of tangent altitude associated with atmospheric refraction is inseparably connected to a variation of the observed apparent intensity, for extended and pointlike sources. We demonstrate, in the regime of weak refraction angles, that atmospheric optical dilution and image deformation are strictly concomitant. The approach leads to the integration of a simple differential equation related to the observed transmittance in the absence of other absorbing molecules along the optical path. We successfully applied the proposed method to the measurements performed by two past occultation experiments: GOMOS for stellar and ORA for solar occultations. The developed algorithm (named ARID) will be applied to the imaging of solar occultations in a forthcoming pico-satellite mission.

scholarly journals Spatio-temporal development of large scale auroral electrojet currents relative to substorm onsets

2021 ◽  
Author(s):  
Sebastian Käki ◽  
Ari Viljanen ◽  
Liisa Juusola ◽  
Kirsti Kauristie
Keyword(s):  
Large Scale ◽  
Current System ◽  
Field Measurements ◽  
Low Earth Orbit ◽  
Satellite Mission ◽  
Low Earth Orbit Satellites ◽  
Spatio Temporal ◽  
Substorm Onsets ◽  
Auroral Current ◽  
Swarm Satellite

Abstract. During auroral substorms the electric currents flowing in the ionosphere change rapidly and a large amount of energy is dissipated in the auroral ionosphere. An important part of the auroral current system are the auroral electrojets whose profiles can be estimated from magnetic field measurements from Low Earth Orbit satellites. In this paper we combine electrojet data derived from the Swarm satellite mission of ESA with the substorm database derived from the SuperMAG ground magnetometer network data. We organize the electrojet data in relation to the location and time of the onset and obtain statistics for the development of the integrated current and latitudinal location for the auroral electrojets relative to the onset. The major features of the behaviour of the westward electrojet are found to be in accordance with earlier studies of field aligned currents and ground magnetometer observations of substorm time statistics. In addition we show that after the onset the latitudinal location of the maximum of the westward electrojet determined from Swarm satellite data is mostly located close to the SuperMAG onset latitude in the local time sector of the onset regardless of where the onset happens. We also show that the SuperMAG onset corresponds to a strengthening of the order of 100 kA in the amplitude of the median of the westward integrated current in the Swarm data from 15 minutes before to 15 minutes after the onset.

Spatio-temporal development of large scale auroral electrojet currents relative to substorm onsets

2021 ◽  
Author(s):  
Sebastian Käki ◽  
Ari Viljanen ◽  
Liisa Juusola ◽  
Kirsti Kauristie
Keyword(s):  
Large Scale ◽  
Current System ◽  
Field Measurements ◽  
Low Earth Orbit ◽  
Satellite Mission ◽  
Low Earth Orbit Satellites ◽  
Spatio Temporal ◽  
Substorm Onsets ◽  
Auroral Current ◽  
Swarm Satellite

<p>The electric currents flowing in the ionosphere change rapidly and a large amount of energy is dissipated in the auroral ionosphere during auroral substorms. An important part of the auroral current system are the auroral electrojets whose profiles can be estimated from magnetic field measurements from low Earth orbit satellites. We have combined electrojet data derived from the Swarm satellite mission of ESA with the substorm database derived from the SuperMAG ground network data. We organize the electrojet data in relation to the location of the onset and obtain statistics for the development of the integrated current and latitudinal location for the auroral electrojets relative to the onset. Especially we show that just after the onset the latitudinal location of the maximum of the westward electrojet determined from Swarm satellite data is mostly located close to the onset latitude in the local time sector of the onset regardless of where the onset happens.</p>

scholarly journals From GPS Receiver to GNSS Reflectometry Payload Development for the Triton Satellite Mission

2021 ◽  
Vol 13 (5) ◽  
pp. 999
Author(s):  
Yung-Fu Tsai ◽  
Wen-Hao Yeh ◽  
Jyh-Ching Juang ◽  
Dian-Syuan Yang ◽  
Chen-Tsung Lin
Keyword(s):  
Satellite System ◽  
Low Earth Orbit ◽  
Export Control ◽  
Navigation Systems ◽  
Gps Receiver ◽  
Design Development ◽  
Satellite Mission ◽  
Essential Components ◽  
Gnss Reflectometry ◽  
Global Navigation Satellite

The global positioning system (GPS) receiver has been one of the most important navigation systems for more than two decades. Although the GPS system was originally designed for near-Earth navigation, currently it is widely used in highly dynamic environments (such as low Earth orbit (LEO)). A space-capable GPS receiver (GPSR) is capable of providing timing and navigation information for spacecraft to determine the orbit and synchronize the onboard timing; therefore, it is one of the essential components of modern spacecraft. However, a space-grade GPSR is technology-sensitive and under export control. In order to overcome export control, the National Space Organization (NSPO) in Taiwan completed the development of a self-reliant space-grade GPSR in 2014. The NSPO GPSR, built in-house, has passed its qualification tests and is ready to fly onboard the Triton satellite. In addition to providing navigation, the GPS/global navigation satellite system (GNSS) is facilitated to many remote sensing missions, such as GNSS radio occultation (GNSS-RO) and GNSS reflectometry (GNSS-R). Based on the design of the NSPO GPSR, the NSPO is actively engaged in the development of the Triton program (a GNSS reflectometry mission). In a GNSS-R mission, the reflected signals are processed to form delay Doppler maps (DDMs) so that various properties (including ocean surface roughness, vegetation, soil moisture, and so on) can be retrieved. This paper describes not only the development of the NSPO GPSR but also the design, development, and special features of the Triton’s GNSS-R mission. Moreover, in order to verify the NSPO GNSS-R receiver, ground/flight tests are deemed essential. Then, data analyses of the airborne GNSS-R tests are presented in this paper.

scholarly journals Toward More Integrated Utilizations of Geostationary Satellite Data for Disaster Management and Risk Mitigation

2021 ◽  
Vol 13 (8) ◽  
pp. 1553
Author(s):  
Atsushi Higuchi
Keyword(s):  
Risk Mitigation ◽  
Low Earth Orbit ◽  
Third Generation ◽  
Atmospheric Measurements ◽  
Terrestrial Environment ◽  
Fine Spatial Resolution ◽  
Terrestrial Environments ◽  
Disaster Monitoring ◽  
Low Earth Orbit Satellites

Third-generation geostationary meteorological satellites (GEOs), such as Himawari-8/9 Advanced Himawari Imager (AHI), Geostationary Operational Environmental Satellites (GOES)-R Series Advanced Baseline Imager (ABI), and Meteosat Third Generation (MTG) Flexible Combined Imager (FCI), provide advanced imagery and atmospheric measurements of the Earth’s weather, oceans, and terrestrial environments at high-frequency intervals. Third-generation GEOs also significantly improve capabilities by increasing the number of observation bands suitable for environmental change detection. This review focuses on the significantly enhanced contribution of third-generation GEOs for disaster monitoring and risk mitigation, focusing on atmospheric and terrestrial environment monitoring. In addition, to demonstrate the collaboration between GEOs and Low Earth orbit satellites (LEOs) as supporting information for fine-spatial-resolution observations required in the event of a disaster, the landfall of Typhoon No. 19 Hagibis in 2019, which caused tremendous damage to Japan, is used as a case study.

Dispersed and disparate sensor management for tracking low earth orbit satellites

2009 ◽  
Author(s):  
A. Zatezalo ◽  
A. El-Fallah ◽  
R. Mahler ◽  
R. K. Mehra ◽  
J. Brown
Keyword(s):  
Low Earth Orbit ◽  
Earth Orbit ◽  
Sensor Management ◽  
Low Earth Orbit Satellites
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