Plan for a High-rate Data Recorder and a New Data Acquisition Terminal

Hitoshi Kiuchi (kiuchi(AT), Michito Imae, Shin'ichi Hama, and Mizuhiko Hosokawa

Communications Research Laboratory
4-2-1 Nukui-kita, Koganei, Tokyo 184, Japan


At the Communications Research Laboratory (CRL), we have been developing VLBI data acquisition terminals (K series) for mainly geodetic purpose. The latest one is the K-4 system, which has a maximum recording rate of 256 Mbps. The high-end version of the K-4 system, which has fully automatic operation is utilized in the Key Stone Project and formal error of a few millimeter over 100 km baselines is performed in daily observation, which is published on the WWW ( Recently CRL has been developing a new VLBI recording system using a GBR recorder for a near-future system which is based on a data recorder that has a maimum recording rate of 1 Gps, which is the state of the art. Besides the development of the GBR system, CRL, as the IERS-VLBI Technical Development Center, is planning to construct a next-generation VLBI system which will have a maximum recording and data processing rate of 2048 Mbps in order to achieve highly sensitive and accurate VLBI. This system will be applicable to various fields of VLBI observation, such as the micro-arcsecond-order radio astrometry to investigate the whole image of our Galaxy using the apparent positional movement of quasars due to gravitational lensing effects [Hosokawa et al., 1997].

Concept of new system

The aim of this plan was not to develop a low-price system but to develop a pioneering technology system in order to comprehend the whole image of the Galaxy by detecting dark matter. A low-price system will be developed in another plan.

We are starting the design of the new system for discussion as follows;

  1. Phase and delay calibration system
  2. Video signal converter
    multi-channel and wide video bandwidth (32 MHz/ch * 32ch or 64 MHz/ch * 16ch),
  3. Input interface (or formatter)
    Using high-speed A/D converters which have maximum sampling rate of more than 150 Msps and 8-bit sampling in each channel. Using digital filtering to minimize the phase flatness,
  4. Data recorder
    Target maximum recording rate of 2048 Mbps, helical scan recording head (for long-term continuous integration), cassette tape, low bit error rate (better than 10-10), etc.
  5. Output interface
    Having modes comaptible with other VLBI acquisition systems,
  6. Correlation processor
    64 MHz clock 32 channels, using ASIC technology for flexibility, etc.
We welcome suggestions and comments about this development project from a wide range of VLBI users, especially concerning;
  1. high rate data recorder
    interface specifications, recording time per volume, bit error rate, etc.
  2. accurate instrumental delay calibration method for bandwidth synthesis method,
  3. input interface
    number of sampling bits, specifications of digital filter, sampling frequency, etc.
  4. compatibility with Mark-III, IV, VLBA, S-2, K-4, etc.
    We are planning that the output interface will have an output mode for all or several of the ones of the present VLBI acquisition systems.
Suggestions for applications and science targets of the new VLBI acquisition system are also requested.


Hosokawa, M., K. Ohnishi, and T. Fukushima, Fluctuation of extra galactic reference frame due to gravitational lensing in our Galaxy, to be published in the Astronomical Journal, 1997.

Figure 1. Concept of new system.

Updated on June 9, 1997. Return to CONTENTS