Recorders

The VLBA records on Mark 5A recording systems, also in use at the VLA and the GBT. Each unit records on two removable modules, sequentially in most cases, but in parallel at the 512-Mbps data rate that is the highest currently supported. Each module comprises eight commercial disk drives. The current VLBA complement of modules is based primarily on 250 or 300 Gbyte disks, for a total of 2-2.4 Terabytes of recording capacity.³ Presently, a few modules with eight 500-750-Gbyte disks (4-6 Terabyte total capacity) are available. Thus, a single module lasts for approximately 17-52 hours if recorded continuously at 256 Mbps, or commensurately shorter periods for recording at 512 Mbps.⁴ More details on Mark 5 systems may be found at http://web.haystack.mit.edu/mark5/Mark5.htm .

As part of the VLBA sensitivity upgrade, we have a goal to convert the VLBA to Mark 5C recording systems, capable of recording data at 4 Gbps, by 2010. See VLBA Sensitivity Upgrade Memo No. 12 (MIT-Haystack and NRAO 2008) for more details about the Mark 5C system.