A detection algorithm of frequency jumps for GNSS satellite clocks
As the frequency and time reference of space satellites, satellite clock has a direct influence on GNSS service performance. Any anomaly of the atomic clock behavior on board the satellites causes errors for user position. Therefore, it is necessary to detect clock anomaly. Frequency jumps are one of the most common anomalies in atomic clocks of on-board satellites, which appear due to space radiation, temperature change and other factors. In this paper, a detection algorithm of frequency jumps based on the batch least squares residues is proposed. Performance of the new algorithm is analyzed and verified by numerical simulation. The detection algorithm of frequency jumps for satellite clocks proposed in this paper is helpful to GNSS satellite clock autonomous integrity monitoring.
Update on the In-Orbit performances of GIOVE clocks
The Galileo In-Orbit Validation Element (GIOVE) is an experiment led by the European Space Agency (ESA) aimed at supporting the on-going implementation of Galileo, the European Global Navigation Satellite System (GNSS). Among others, the objectives of the GIOVE Mission are the validation and characterization of the on-board clock technologies. The today baseline technologies for on-board clocks are the Rubidium Atomic Frequency Standard (RAFS) and the Passive Hydrogen Maser (PHM). Both technologies have been validated and qualified on ground and are now being further validated in a representative in-orbit environment on-board two spacecrafts, GIOVE-A and GIOVE-B. This paper presents the results obtained on both spacecrafts, after more than three years (GIOVE-A) and almost one year (GIOVE-B) of operation.
Monte carlo simulation of events with Drell-Yan lepton pairs from antiproton-proton collisions
The complete knowledge of the nucleon spin structure at leading twist requires also addressing the transverse spin distribution of quarks, or transversity, which is yet unexplored because of its chiral-odd nature. Transversity can be best extracted from single-spin asymmetries in fully polarized Drell-Yan processes with antiprotons, where valence contributions are involved anyway. Alternatively, in single-polarized Drell-Yan the transversity happens convoluted with another chiral-odd function, which is likely to be responsible for the well known (and yet unexplained) violation of the Lam-Tung sum rule in the corresponding unpolarized cross section. We present Monte Carlo simulations for the unpolarized and single-polarized Drell-Yan pp{sup ({up_arrow}}{sup )}{yields}{mu}{sup +}{mu}{sup -}X at different center-of-mass energies in both configurations where the antiproton beam hits a fixed proton target or it collides on another proton beam. The goal is to estimate the minimum number of events needed to extract the above chiral-odd distributions from future measurements at the high energy storage ring (HESR) at GSI. It is important to study the feasibility of such experiments at HESR in order to demonstrate that interesting spin physics can be explored already using unpolarized antiprotons.