GPS-Antenna phase center measurements performed in an anechoic chamber

Tracking and orbit determination performance of the GRAS instrument on MetOp-A

The global navigation satellite system receiver for atmospheric sounding (GRAS) on MetOp-A is the first European GPS receiver providing dual-frequency navigation and occultation measurements from a spaceborne platform on a routine basis. The receiver is based on ESA’s AGGA-2 correlator chip, which implements a high-quality tracking scheme for...

Ultra -Wideband Leaky- Wave Antenna for Medical Imaging

Cancer can be viewed as a curse on life of any man or woman. Although some tumors that are malignant can be curable, it comes at a cost of unbearable pain and mental trauma. X-ray based techniques are being used for many decades for detecting tumors. These techniques are applied at the expense of exposure to high ionized radiation levels....

Sentinel-1A - First precise orbit determination results

Sentinel-1A is the first satellite of the European Copernicus programme. Equipped with a Synthetic Aperture Radar (SAR) instrument the satellite was launched on April 3, 2014. Operational since October 2014 the satellite delivers valuable data for more than two years. The orbit accuracy requirements are given as 5. cm in 3D. In order to...

High quality zenith tropospheric delay estimation using a low-cost dual-frequency receiver and relative antenna calibration

The recent release of consumer-grade dual-frequency receivers sparked scientific interest into use of these cost-efficient devices for high precision positioning and tropospheric delay estimations. Previous analyses with low-cost single-frequency receivers showed promising results for the estimation of Zenith Tropospheric Delays (ZTDs)....

The antenna phase center motion effect in high-accuracy spacecraft tracking experiments

We present an improved model for the antenna phase center motion effect for high-gain mechanically steerable ground-based and spacecraft-mounted antennas that takes into account non-perfect antenna pointing. Using tracking data of the RadioAstron spacecraft we show that our model can result in a correction of the computed value of the effect...

Perspectives of Cost-Efficient GNSS Equipment for Wide-Spread and High-Quality Meteorological and Positioning Applications

Whether in cars, smartphones, watches or fitness-trackers - the use of Global Navigation Satellite Systems (GNSS) has become a part of our daily life. Currently there are more than 100 GNSS satellites in orbit. They are routinely utilized for positioning and timing purposes, but their signals can also be used to monitor our environment. The...

A Field Calibration Solution to Achieve High-Grade-Level Performance for Low-Cost Dual-Frequency GNSS Receiver and Antennas

Low-cost dual-frequency receivers and antennas have created opportunities for a wide range of new applications, in regions and disciplines where traditional GNSS equipment is unaffordable. However, the major drawback of using low-cost antenna equipment is that antenna phase patterns are typically poorly defined. Therefore, the noise in...

On the Near-Field Spherical Wave Formation in Resonant Leaky-Wave Antennas: Application to Small Lens Design

In this work, we show that the near field of leaky-wave resonant antennas (LWAs) radiating into a dense medium can be locally represented as a spherical wave in a certain solid angle around broadside using an accurate definition of the phase center. The near field in this solid angle can be efficiently evaluated through the integration of the...