TY  - JOUR
A1  - Xiong, Chao
A1  - Stolle, Claudia
A1  - Park, Jaeheung
T1  - Climatology of GPS signal loss observed by Swarm satellites
JF  - Annales geophysicae
N2  - By using 3-year global positioning system (GPS) measurements from December 2013 to November 2016, we provide in this study a detailed survey on the climatology of the GPS signal loss of Swarm onboard receivers. Our results show that the GPS signal losses prefer to occur at both low latitudes between +/- 5 and +/- 20 degrees magnetic latitude (MLAT) and high latitudes above 60 degrees MLAT in both hemispheres. These events at all latitudes are observed mainly during equinoxes and December solstice months, while totally absent during June solstice months. At low latitudes the GPS signal losses are caused by the equatorial plasma irregularities shortly after sunset, and at high latitude they are also highly related to the large density gradients associated with ionospheric irregularities. Additionally, the high-latitude events are more often observed in the Southern Hemisphere, occurring mainly at the cusp region and along nightside auroral latitudes. The signal losses mainly happen for those GPS rays with elevation angles less than 20 degrees, and more commonly occur when the line of sight between GPS and Swarm satellites is aligned with the shell structure of plasma irregularities. Our results also confirm that the capability of the Swarm receiver has been improved after the bandwidth of the phase-locked loop (PLL) widened, but the updates cannot radically avoid the interruption in tracking GPS satellites caused by the ionospheric plasma irregularities. Additionally, after the PLL bandwidth increased larger than 0.5 Hz, some unexpected signal losses are observed even at middle latitudes, which are not related to the ionospheric plasma irregularities. Our results suggest that rather than 1.0 Hz, a PLL bandwidth of 0.5 Hz is a more suitable value for the Swarm receiver.
KW  - Ionosphere
KW  - equatorial ionosphere
KW  - ionospheric irregularities
KW  - radio science
KW  - radio wave propagation
Y1  - 2018
U6  - https://doi.org/10.5194/angeo-36-679-2018
SN  - 0992-7689
SN  - 1432-0576
VL  - 36
IS  - 2
SP  - 679
EP  - 693
PB  - Copernicus
CY  - Göttingen
ER  -