GUPPI Ready for Expert Users

Scott Ransom

Figure 1

Figure: A 3.5-minute GBT L-band observation of the original millisecond pulsar B1937+21 taken with the current "default" full-Stokes, 2048-channel, 40.96-us sampling mode. The white horizontal lines show where RFI has been removed, while the dark patches are "scintles" caused by diffractive scintillation in the interstellar medium. The pulse profile at top shows the total intensity (black) as well as the linear (red) and circularly (blue) polarized components.


Beginning September 30, the new pulsar backend called GUPPI (Green Bank Ultimate Pulsar Processing Instrument) will be available for GBT pulsar observations in a shared-risk, expert user mode. GUPPI can be used for wide bandwidth (800 MHz) observations in conjunction with other existing pulsar instruments.

GUPPI's development is proceeding rapidly, with the long-term goal of having wide-bandwidth coherent de-dispersion capabilities. Its current capabilities, though, are already far superior to those available for the wide-bandwidth Spigot modes. The system available at the end of September will have the following capabilities at a minimum:

Short-term development is focusing on a 4096-channel mode and digital down-conversion that will allow narrower bandwidth modes (initially 50 MHz, 80 MHz and 200 MHz).

It is likely that observations with this instrument will be limited by the rate at which data can be processed and removed from the data-taking computer, which has 15 TB of disk space. The nominal data rate of the full-Stokes search mode with no downsampling is 200 MB/s, 8 times the Spigot data rate! Therefore, potential users are highly encouraged to only record the data that they will actually need for their science and to utilize on-line folding, the total intensity mode, and downsampling whenever possible.

For more information about using GUPPI for your project, contact Scott Ransom.