The NBS Boulder Laboratory is in the process of assembling a very high accuracy time transfer system. The system includes a 6.1 meter Ku-band satellite earth station, two transportable earth stations each with a 1.8 meter dish, and commercial modems designed for two-way timing. Elements of the facilities are described in this paper. High-accuracy timing with this equipment using the two-way tim...

In the multi-satellite and multi-ground station downlink task scheduling problem, waiting time from proposal of to execution will affect its validity. If satellite has multiple communicable ground stations when is proposed, selection problem needs be solved first. After selection, since available conflict between tasks different satellites for same station, specific start should determined. To ...

This paper summarizes the use of Software Defined Radio (SDR) technology for space applications by installing a low-cost VHF/UHF ground receiving station to assist existing and future mission universities. The intended solution is based upon utilization RTL-SDR, which are commercial off-the-shelf components available on market.

Stratospheric O3 profiles obtained by the satellite limb sounders Aura/MLS, ENVISAT/MIPAS, ENVISAT/GOMOS, SAGE-II, SAGE-III, UARS/HALOE are compared to coincident O3 profiles of the ground-based microwave radiometer SOMORA in Switzerland. Data from the various measurement techniques are within 10% at altitudes below 45 km. At altitudes 45–60 km, the relative O3 differences are within a range of...

Low Earth Orbit (LEO) satellites are used for public networking and for scientific purposes. Communication via satellite begins when the satellite is positioned in its orbital position. Ground stations can communicate with LEO satellites only when the satellite is in their visibility region. The duration of the visibility and the communication vary for each LEO satellite pass over the station, ...

Near real-time data downlinks from aircrafts, satellites and high altitude platforms via high-speed laser communication links is an important research topic at the Institute of Communications and Navigation of the German Aerospace Center (DLR). Ground stations for such scenarios are usually fixed at a certain location. With a motivation to provide a ground station that is quickly and easily dep...

If multiple-input multiple-output (MIMO) satellite communications (SATCOM) systems use spatial multiplexing, the channel capacity depends on the geometrical conditions of the antenna setup. This theoretical result is proven and confirmed for the first time by a true-MIMO test campaign. To this end, we utilize two Ku-band satellites and a ground station with two antennas as a 2× 2 MIMO SATCOM me...

Dear Reviewer, Please find bellow our responses to your valuable comments regarding the manuscript entitled “TEMIS UV product validation using NILU-UV ground-based measurements in Thessaloniki, Greece”. Sincerely, Dr. Melina Zempila. âĂČ -Some rationale should be provided why TEMIS data were evaluated with NILU-UV measurements and not directly with Brewer measurements, which should be the most ...

Ionospheric perturbations by natural geophysical activity, such as volcanic eruptions and earthquakes, have been studied since the great Alaskan earthquake in 1964. Measurements made from the ground show a variation of the critical frequency of the ionosphere layers before and after the shock. In this paper, we present an experimental investigation of the electron density variations around the ...