Notes about the ROACH1 backend¶
The ROACH1 has the capability to process 32 x 16 MHz bands = 512 MHz of bandwidth, therefore the entire L-band and P-bands. It is not adequate for observing in C-band or K-band unless one wants to observe a smaller portion of the total bandwidth. With the current setup of being linked to an 8-node CPU cluster (the “LEAP cluster”), it can only process 8 x 16 MHz bands = 128 MHz of bandwidth. It is therefore adequate for LEAP observations, which observe only a portion of the total L-band, or for the entire P-band. In the near future (later part of 2019), a second ROACH1 board (ROACH1_GPU) will be linked to the SARDARA GPU cluster and will be able to process the entire L-band (512 MHz).
We have two sets of instructions. The main set of instructions includes the use of the SEADAS sofware tool, which controls both the antenna and the backends, while the second set includes manual instructions (useful for using the ROACH1 in “piggy-back mode”).
With regard to the manual instructions: in this configuration, where the ROACH1 is used in piggy-back mode, the ROACH1 is not “integrated” into the DISCOS antenna control system. DISCOS is used only to point at the sources, while with the use of the externalClient, the ROACH1 follows the antenna in an automated way. To tell DISCOS to track sources, the observer can use manual instructions or load a standard DISCOS schedule. To tell the ROACH1 to start/stop data acquisition, the observer can launch the automated system on the LEAP cluster which follows what the antenna is doing (start of data acquisition when the antenna is TRACKING and stop when the antenna is SLEWING). In case of problems with the externalClient, the start and stop of data acquisition can also be done manually on the LEAP cluster.
For more information, contact D. Perrodin.