Global Ionospheric and Thermospheric Effects of the June 2015 Geomagnetic Disturbances: Multi-Instrumental Observations and Modeling

By using data from multiple instruments, we investigate ionospheric/thermospheric behavior during the period from 21 to 23 June 2015, when three interplanetary shocks (IS) of different intensities arrived at Earth. The first IS was registered at 16:45 UT on 21 June and caused ~50 nT increase in the SYM-H index. The second IS arrived at 5:45...

Gravity field models derived from Swarm GPS data

It is of great interest to numerous geophysical studies that the time series of global gravity field models derived from Gravity Recovery and Climate Experiment (GRACE) data remains uninterrupted after the end of this mission. With this in mind, some institutes have been spending efforts to estimate gravity field models from alternative...

Impact of Swarm GPS receiver updates on POD performance

The Swarm satellites are equipped with state-of-the-art Global Positioning System (GPS) receivers, which are used for the precise geolocation of the magnetic and electric field instruments, as well as for the determination of the Earth's gravity field, the total electron content and low-frequency thermospheric neutral densities. The onboard...

Swarm accelerometer data processing from raw accelerations to thermospheric neutral densities

The Swarm satellites were launched on November 22, 2013, and carry accelerometers and GPS receivers as part of their scientific payload. The GPS receivers do not only provide the position and time for the magnetic field measurements, but are also used for determining non-gravitational forces like drag and radiation pressure acting on the...

The flyby anomaly: An investigation into potential causes

Since December 1990, a number of spacecraft have performed a flyby around Earth in which an unexpected change in velocity has been observed, which has not been explained so far: the so-called flyby anomaly. The effect on the excess velocity has been expressed in an empirical relation by Anderson, which was based on data on 6 such flybys. However...

Calibration and validation of individual GOCE accelerometers by precise orbit determination

The European Space Agency Gravity field and steady-state Ocean Circular Explorer (GOCE) carries a gradiometer consisting of three pairs of accelerometers in an orthogonal triad. Precise GOCE science orbit solutions (PSO), which are based on satellite-to-satellite tracking observations by the Global Positioning System and which are claimed to be...

GPS-based precise orbit determination and accelerometry for low flying satellites

Atmospheric density models are currently the limiting factor in the accuracy of the dynamic orbit determination and prediction of satellites in a low Earth orbit. Any improvement in these models would greatly aid in applications such as re-entry prediction, ground-track maintenance of Earth observation satellites and forecast of possible...

GPS-derived orbits for the GOCE satellite

The first ESA (European Space Agency) Earth explorer core mission GOCE (Gravity field and steady-state Ocean Circulation Explorer) was launched on 17 March 2009 into a sun-synchronous dusk–dawn orbit with an exceptionally low initial altitude of about 280 km. The onboard 12-channel dual-frequency GPS (Global Positioning System) receiver delivers...

GOCE SSTI L2 tracking losses and their impact on POD performance

The state-of-the-art GOCE Satellite-to-Satellite Tracking Instrument (SSTI) delivers high-quality GPS data with an almost continuous 1 Hz data rate, which allows for very Precise Orbit Determination (POD). Despite this good performance, the GPS receiver shows occasional unexpected L2 tracking losses, which mainly occur close to the geomagnetic...