Stellar aberration correction and thermoelastic compensation of Swarm μASC attitude observationsA comment to the Express Letter “Mysterious misalignments between geomagnetic and stellar reference frames seen in CHAMP and Swarm satellite measurements”, by Stefan Maus

The features of reference frame, concomitant to the cosmic microwave background, immobile relatively cosmic microwave background, are considered. It is shown that the features of reference frame, concomitant to the cosmic microwave background (CMB), are determined by its properties. Any other object in the Universe and reference frame concomitant to it, is immersed in the CMB and moves relative to the reference frame concomitant to microwave background radiation. The zero pecular velocity of the reference frame concomitant to the microwave background radiation is analogous to the zero temperature on the Kelvin scale. Time in it is most rapid in relation to the time in any other reference frame, observable and measurable in any of them. The features of time, pecular speed, relative speed of two inertial RF, stellar aberration, and Doppler effect in the reference frame concomitant to the microwave background radiation are considered. According to the determined relative velocity of the two reference systems and the peculiar velocity of the reference system with the observer, the components of their relative velocity are determined. Determining the components of the relative velocity of the reference frames with determining the synchronous time for all points at any time in the reference frame concomitant to microwave background radiation, allows us to investigate the possibility of determining the speed of light "one way" and using it to navigate vehicles in distant space. Stability of angular location of heterogeneities of CMB in reference frame concomitant to CMB, allows us to use these heterogeneities for the increase of exactness of astronomic reference frames HCRF and ICRF.

Download Full-text

VirES for Swarm – Virtual Research Environment

10.5194/egusphere-egu2020-19908 ◽

2020 ◽

Author(s):

Martin Pačes ◽

Daniel Santillan Pedrosa ◽

Ashley Smith

Keyword(s):

Space Weather ◽

Satellite Orbit ◽

Weather Conditions ◽

Third Party ◽

Satellite Measurements ◽

Research Environment ◽

Original Product ◽

Virtual Research Environment ◽

Machine Interface ◽

Swarm Satellite

VirES for Swarm [1] is a data manipulation and retrieval interface for the ESA Swarm constellation mission data products. It includes tools for studying various geomagnetic models by comparing them to the Swarm satellite measurements at given space weather and ionospheric conditions.The list of the provided Swarm products is growing and it currently includes MAG (both, LR and HR), EFI, IBI, TEC, FAC, EEF, and IPD products as well as the collection of L2 SHA Swarm magnetic models, all synchronized to their latest available versions.VirES provides access to the Swarm measurements and models either through an interactive visual web user interface or through a Python-based API (machine-to-machine interface). The latter allows integration of the users' custom processing and visualization.The API allows easy extraction of data subsets of various Swarm products (temporal, spatial or filtered by ranges of other data parameters, such as, e.g., space weather conditions) without needing to handle the original product files. This includes evaluation of composed magnetic models (MCO, MLI, MMA, and MIO) and calculation of residuals along the satellite orbit.The Python API can be exploited in the recently opened Virtual Research Environment (VRE), a JupyterLab based web interface allowing writing of processing and visualization scripts without need for software installation. The VRE comes also with pre-installed third party software libraries (processors and models) as well as the generic Python data handling and visualization tools.A rich library of tutorial notebooks has been prepared to ease the first steps and make it a convenient tool for a broad audience ranging from students and enthusiasts to advanced scientists.Our presentation focuses on the introduction of the new Virtual Research Environment and recent VirES evolution.[1] https://vires.services

Download Full-text

Mysterious misalignments between geomagnetic and stellar reference frames seen in CHAMP and Swarm satellite measurements

Geophysical Journal International ◽

10.1093/gji/ggv409 ◽

2015 ◽

Vol 203 (3) ◽

pp. 1873-1876 ◽

Cited By ~ 7

Author(s):

Stefan Maus

Keyword(s):

Magnetic Field ◽

Reference Frames ◽

European Space Agency ◽

Processing System ◽

Field Measurements ◽

Low Earth Orbit ◽

Space Agency ◽

Order Of Magnitude ◽

Stellar Aberration ◽

Star Camera

AbstractThe orientation of a spacecraft in Low Earth Orbit can be determined accurately from either magnetic field measurements or star camera images. Ideally, the independently computed spacecraft attitudes should agree. However, we find that the German CHAMP and European Space Agency triple-satellite Swarm geomagnetic satellites exhibit consistent misalignments between the stellar and geomagnetic reference frames, which oscillate with the local time of the orbit. Having an amplitude of 20 arcsec, these oscillations are more than an order of magnitude larger than the stability of the optical bench, which cohosts the magnetometers and star cameras. The misalignments could originate either from the magnetometer or star camera measurements. On one hand, as-yet-unknown external magnetic field contributions could appear as a rotation of the geomagnetic reference frame. On the other hand, the observed misalignments agree in amplitude and phase with the effects of stellar aberration, caused by the movement of the star cameras relative to the light rays emitted by the stars. This is surprising because stellar aberration is allegedly already corrected for by the star image processing system. Resolving these mysterious misalignments is key to fulfilling the measurement accuracy requirements and science objectives of the ongoing Swarm mission. If caused by stellar aberration, fully correcting for this effect could significantly improve the attitude accuracy not only of CHAMP and Swarm, but also of several other past and ongoing scientific satellite missions.

Download Full-text