The data released in DR19 contain data observed both with plug plates (as in past SDSS surveys) and with the new Focal Plane System. Below are key differences in the observing strategies that affect the kind and quality of data obtained for MWM targets.
Additional targeting information can be found on the main Targeting webpage (for details on how the input catalogs were compiled and queried for targeting selection), the Science Programs page (for selection functions and observing requirements), and the Targeting Flags page (for information on how to access targeting information in the data products).
Observing Strategies
Plate Operations
During the plate operations, a particular field could be assigned one of nine possible cadence categories, defined by the lead science program’s cadence requirements. The cadence category defined the plate’s exposure time, number of epochs, and strategy for filling the fibers. MWM science programs defined the requirements for the first 5 cadences, which were observed during bright time. The Black Hole Mapper program defined the requirement for the remaining four cadences, which were observed during dark time.
| Plate Cadence Name | Exposure Time | Number of Epochs | Lead Science Program |
| GG | 33 min | 1 | Galactic Genesis |
| RV6 | 67 min | 6 | Binary Systems |
| RV12 | 67 min | 12 | Binary Systems |
| TESS | 67 min | 3 | Asteroseismic Red Giants |
| YSO | 67 min | 3 | Young Stellar Objects |
| AQMES-Medium | 60 min | 6 | AQMES |
| AQMES-Wide | 60 min | 1 | AQMES |
| eFeds | 120 min | 1 | SPIDERS |
| RM | 120 min | 5 per month | RM |
For each platerun, targets were assigned to fibers using an “order” file. These files simply listed the science programs that could be assigned to a given plate type, with the highest priority programs listed first. All targets associated with the highest priority program were assigned fibers before moving onto the next prioritized program in the order file and continuing until all 500 BOSS fibers and 300 APOGEE fibers were filled. The relative ranking of programs was manually set with consideration given both to the science goals of the program governing the cadence (as in the above table) and the relative ease or difficulty of observing different classes of targets. For example, programs with sparse sky density tended to be highly prioritized even on plates mismatched to ideal observing conditions. Most MWM programs were eligible for fiber assignment on most plate types. See cadence section on the individual MWM Program Pages for program-specific details.
FPS Operations
During FPS operations, a single exposure was fixed to a much shorter exposure time (~15 minutes) to accommodate a wide dynamic range of exposure depth and capitalize on the FPS’s ability to simultaneous support long (multi-exposure) observations while reconfiguring single exposures onto many different targets. Fiber resources to MWM targets during this era of observations were allocated with the robostrategy software. The cadences used for each MWM science program can be found on the carton description on the individual MWM Program pages.