AMS-02 data flow allows for data recording on the AMS Laptop right on board the International Space Station (ISS) as well as for a direct transmission, by means of satellites, to Marshall Space Flight Center (MSFC) in Alabama. From MSFC, via internet, the bulk of the data flow to the Payload Operation Control Center (POCC), while critical health data (CHD) are directly transmitted from AMS-02 to the POCC in order to have a quick overview of the detector status. At POCC, beside the control activity during flight operations, online data monitoring is performed to verify the corect subdetectors operation. Then, the data are sent to the Science Operation Center (SOC) where they are processed and analyzed.
Subsequently, data are distributed from SOC to Regional Sites, which will store AMS-02 data and are Monte Carlo production facilities as well.
The Milano-Bicocca Data Transfer (DT) system overviews the overall data transfer from/to CERN, where the final POCC and SOC are located, to/from Regional Sites.
The Italian Ground Segment Data Storage (IGSDS), located at CNAF in Bologna (Italy), will host a master copy of the whole AMS-02 data sample: raw frames, reconstructed and simulated data. The corresponding data volume will be around 150 TB per year.
The IGSDS will act as a “distribution center”, in order to allow fast data access to the AMS collaborators, meanwhile avoiding interfering with SOC activities.
IGSDS will also provide computing power for Monte Carlo production and analysis facility, as a part of the network of AMS Regional Sites.
Data Transfer software was developed and is maintained by INFN Milano-Bicocca since 2004. Its core is a Multi-threaded finite state automa plus state transition jobs. It uses a database (Mysql/Oracle) for book-keeping and can work in GRID and non-GRID environments.
AMS-02 Milano-Bicocca DT system’s aim is to move data efficiently from SOC to IGSDS, without interfering with SOC activities and keeping track of what successfully or unsuccessfully has been moved. The minimum throughput required is 36 Mb/s, being three times the data rate foreseen: this makes possible, in case of DT malfunction, a fast recovery of data sets alignment (at CERN and at CNAF). The DT is also capable of moving data from remote locations to SOC, which can be useful for example in case of Monte Carlo production taking place in regional sites.
Thanks to its flexibility and implementation easyness, the data transfer system has been installed on the following locations:
– IGSDS at CNAF, Bologna
– ASI Science Data Center
– Beijing Univ. Aeronautics and Astronautics (BUAA/NLAA)
– South East University (SEU).