Next Generation VLBI Terminals (Should be) Planned at CRL

Tetsuro Kondo (kondo(AT)

Kashima Space Research Center
Communications Research Laboratory
893-1 Hirai, Kashima, Ibaraki 314, Japan

Generally speaking, a technical development is closely connected with scientific progress, and vice versa. We summarize this relation as follows.

Figure 1. Relation between technical development and scientific progress.

Two feedback loops are considered between their relations (Fig.1). One is an ``accuracy improvement'' loop. In this feedback loop, the observation system is designed to achieve the best measurement accuracy from the technical point of view. Cost-effectiveness is sometimes regarded as an unimportant factor in a system development. High-accuracy measurements will stimulate scientific study, while scientific result will stimulate more accurate system development.

The other one is a ``spread promotion'' loop. Being different from the previous one, this type of loop aims to reduce cost rather than to increase accuracy, in order to permit wide dissemination of the system in the VLBI community. Miniaturization of the system can also be a goal for portability. Even though accuracy of measurements is sacrificed, widely distributed VLBI terminals will produce new observational data which bring a new insights in science.

The former one, pursuing an accuracy improvement, can be divided into two types of terminal which are planned or almost developed at the Communications Research Laboratory (CRL) (Fig.2).

Figure 2. Next generation VLBI recorder system.

One is a multi-channel type mainly dedicated to geodetic rather than astronomical applications (see Kiuchi's report in this newsletter). Even though this system is still in the planning phase, almost all technical key items regarding this system are already or will soon be realized. The other type is one having fewer channels but wider bandwidth per channel ( Nakajima, 1996). The recording and reproducing part of this system has been already developed.

In addition to persuing accuracy we should be concerned about the distribution of terminals. If the price of VLBI terminal goes down with total performance being kept as accurate as current one, terminals will be easily distributed widely. Furthermore if it becomes compact in size, we will be able to bring it easily anywhere in the world.

CRL should proceed with both types of development if possible.


Kiuchi, H., Plan for a high-rate data recorder and a new data acquisition terminal, VLBI TDC News CRL, No.10 (this issue), pp.19-20,1997.

Nakajima, J., Current status of the gigabit VLBI recorder system, VLBI TDC News CRL, No.9, pp.17-18, 1996.

Updated on June 9, 1997. Return to CONTENTS