Development of a New VLBI Sampler Unit Dedicated to e-VLBI for Near Real-Time Monitoring of Earth Rotation Tetsuro Kondo, Yasuhiro Koyama, Hiroshi Takeuchi, and Moritaka Kimura Kashima Space Research Center, National Institute of Information and Communications Technology, 893-1 Hirai, Kashima, Ibaraki 314-0012, Japan (e-mail: kondo@nict.go.jp) National Institute of Information and Communications Technology (NICT) has developed three models of VLBI samplers, ADS1000, ADS2000 and K5/VSSP, dedicated to near real-time VLBI observation (e-VLBI) through a high-speed network connection for monitoring earth orientation parameters. Among these three models, the K5/VSSP, which is designed to be a PCI bus board mountable on a general purpose PC, has broadened the base for VLBI users, i.e., any PC equipped with the K5/VSSP PCI-bus board can be a VLBI recorder, and the data transfer through the Internet is easily realized. With the advent of K5/VSSP the development of software correlator also greatly progressed. Recently we have developed a new VLBI sampler named K5/VSSP32 as a successor to the K5/VSSP. Maximum sampling frequency is increased up to 32MHz. When the number of quantization bit is limited to one, the sampling frequency of 64MHz is possible. Moreover USB 2.0 (Universal Serial Bus specification revision 2.0) is adopted as an interface to connect the sampler with a host PC. It is hence possible to use note book PCs for VLBI observations if it is desired. Specifications are summarized in Table 1. We will report the results of some test observations using K5/VSSP32 at the meeting. Table1. Specifications of VLBI samplers --------------------------------------------------------- model ADS1000 ADS2000 K5/VSSP K5/VSSP32 --------------------------------------------------------- # of CH 1 16 4 4 per unit Max sampling 1024MHz 64MHz 16MHz 32MHz frequency # of 1,2 2 1,2,4,8 1,2,4,8 AD bits Max data rate 2048Mbps 2048Mbps 64Mbps 256Mbps per unit Output VSI-H VSI-H PCI-bus USB 2.0 ---------------------------------------------------------