In SMA Tech Memo #99 (Masson 1996), the data rate and the backup storage for the SMA were discussed. Here we update the discussion based on the current specification of the SMA.
With the eight-element SMA in full operation, 2688 chips with 128 lags/chip (64 spectral channels), or 172032 channels are available. The maximum data rate will be 172032 x 8bytes (complex vis.) x2 (DSB) = 2.75 Mbytes per sampling. For a typical full track synthesis observation of 8 hours, assuming typical sampling rate of 10 seconds, 7.9 Gbytes of the data per each track or about 16 - 24 Gbytes per day will be produced. For high resolution array modes including SMA + JCMT + CSO combined array mode, higher sampling rates are expected if phase correction techniques are to be applied. If we accumulate the data with the above mentioned rate and assuming 256 observing days per year(assuming operational efficiency of 70%), about 4 - 6 Tbytes of data will be produced in one year. The data can be temporarily put into hard disks but it is apparent that we need massive storage spaces for more long-term data storage. Note that above discussion assumes that all the data are stored without any on-line calibration (e.g. on-line phase correction) which can reduce the data volume drastically. Also, it is likely that many projects (for example continuum observations) will produce much less data per unit time. In average, we expect that the data production rate would be 1 Tbyte per year.