Cheat sheet for problems with parallel buffer dumps

These are some things to know that may be helpful resolving parallel buffer dumping issues:

Things to know:

  1. After the first ACS/WFC exposure, each exposure must be >= 339 sec in order for the dump of the previous exposure to be done in parallel to the current exposure. Shorter exposures results in dumps done in series and a significant loss of observing time. (This is because the ACS buffer can only hold one full frame image and it must be able to be dumped in its entirety during the next exposure to be dumped in parallel.)

  2. After the first WFC3/UVIS exposure, each exposure must be >= 348 sec, or after two short exposures, the next exposure must be >=664 sec. (This is because the WFC3 buffer can hold two full frame images, but when it dumps it must be able to dump both images in their entirety during the next exposure to be dumped in parallel.) A fuller explanation can be found in the : instrument handbook.

  3. These times assume that CR-Split=No. If not, the pieces of the split must meet these minimums.

  4. For WFC3/IR exposures the buffer can hold two full frame 15 sample exposures. As with the UVIS, dumping one exposure in parallel will require a >= 348 sec exposure and dumping two exposures in parallel require a >=664 sec exposure. But note that unlike UVIS the IR data can be partially dumped. A fuller explanation can be found in the instrument handbook: instrument handbook.

  5. When instruments are used in parallel it becomes more difficult to ensure that buffer dumps are done in parallel. This is because the instruments have to take turns dumping their buffers to the solid state recorder.

  6. You won't be able to get more than 4 full frame exposures in a normal orbit with ACS/WFC and WFC3/UVIS. You may be able to get more with WFC3/IR. Consider using subarrays if appropriate for your science.

  7. If there is a short exposure, put that one first (since nothing has to dump in parallel to it) or put it last.

  8. COS and STIS have pretty short dump times and adding them to the parallels does not make things significantly more complicated. But if TIME-TAG is being used only one TIME-TAG exposure can be in each Prime/Parallel group.

  9. If you are doing a CVZ observation, the final dump needs to be fit into the final orbit because there is no occultation in which to to bury it.

  10. The last exposure for a particular instrument in a visit will be dumped in series regardless of whether there is room to dump it in parallel to the prime observation. So if you are ending parallels for an instrument early in a visit, consider adding a short parallel with that instrument at the end of the visit to delay the serial dump until the end.

Example Proposals:

Note that you can also retrieve any of these example proposals into APT using File - Retrieve from STScI.