one of the difficulties in using absolute altitudes is the separation between the mean open sealevel and geoid. theoretically, geoid is the base level in absolute altitudes, but practically, the mean open sealevel is used as a base level for absolute altitudes. the difference between these two levels is called as the seasurface topography. in this research, it is dealt the mean sea level modeli...

High-data-rate ground-to-space optical links are envisioned to be an alternative and more probably a next step to radio-frequency links, after the Q/V band still under development [1] for the feeder links of next generation high throughput satellites. Indeed, optical links allow a significant increase of the available spectral resources per link. This enables a drastic reduction of the number o...

In the present work a new concept of satellite-based navigation system, which does not require on-board atomic references, is presented. This novel concept consists of a constellation of compact low-earth orbit positioning satellites that are equipped with on-board steerable clocks, i.e. voltage controlled crystal oscillator (VCXO). An appropriate ground-satellite synchronization network is res...

To reduce the sampling rate in global navigation satellite system (GNSS)-radio occultation receivers, it is essential to establish a suitable estimation of Doppler frequency from the received signal in the satellite onboard receiver. This receiver is usually located on low earth orbit satellite and receives GNSS satellites signal in the occultation situation. The occurred Doppler on the signal ...

In this paper we analyze in detail some aspects of the proposed use of Ajisai and Jason-1, together with the LAGEOS satellites, in order to measure the general relativistic Lense-Thirring effect in the gravitational field of the Earth. A suitably designed linear combination of the nodes of such satellites which cancels out, by construction, the first three even zonal harmonics of the Newtonian ...