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SPECIAL CO-ADDS, MOSAICS, and SKY TILING
Proposers may now request special co-added data sets, made using the GALEX pipeline software.
Special co-adds requested in Cycle 6 will not be delivered before GALEX GR-6, currently estimated for spring 2010. Special co-adds may be requested for any data that will be released in GR-6, although the maximum exposure time that can be guaranteed is that currently available in GR-5 (as listed in TOAST) ). Special co-adds requested as part of the Cycle 6 proposal process will be treated the same way as new observations - they will be proprietary to the proposer for 6 months after the proposer is notified of their availability in MAST, and will become public after that. Special co-adds will not become part of the regular GRs, but will continue to remain available as (publicly released) GI data at MAST. New + archival co-adds will become available to the GI's on the same schedule as the new observations. Special co-adds will have all the same data products as standard co-adds, and will be contained in standard (3840 x 3840 pixels, 1.6 x 1.6 degree) GALEX image.
Several combinations are possible:
- Combine observations from more than one data set at the same location. This could be new observations combined with archival observations, or two (or more) different archival data types (e.g., GI and MIS).
- Combine observations at different pointing centers but covering common regions of the sky. This could be where a GI observation partly overlaps a survey observation, with an object of interest in the common area.
- For deep fields or other very long integrations, co-adds may be requested on a specific time-spacing - e.g. monthly, or weekly.
Special co-adds should result in a significant increase in Signal-to-Noise ratio. Requests will not be accepted for combinations where the new co-add exposure time is less 125% of the deepest input coadd. [Thus, for example, DIS 14000s + MIS 2000s = coadd 16000s (less than 125% of 14000s) would not be allowed. However, DIS 14000 s + GI4000s = coadd 18000s (more than125% of 14000s) would be acceptable.]
Special co-adds should be entered in the ARK proposal form, and should be justified in the "Feasibility" section of the Scientific Justification. When combining new GI observations with archival data (GI or survey data), the new observations should be entered in the ARK proposal form, and the additional data sets should be indicated in the individual observation "Comments" form. When combining different archival data types (MIS with NGS, for example), or combinations of more than one archival GI data set, the single longest-integration data should be entered in the ARK form as an archival target, and additional shorter-integration data sets should be indicated in the individual observation "Comment" form. Proposers should indicate the center position desired (RA, dec) and indicate the diameter of the science target(s) and/or region of interest.
All GALEX users are, of course, welcome to use public data and their own software to produce their own coadds.
In this Cycle, we are unable to support requests for special sky mosaics, either from archival or new (or mixed) observations.
Proposers may request tiling a large area of the sky, if desired. Examples might be a proposal to map a 4 x 8 degree patch of sky that is the focus of a deep optical survey, or perhaps two 3 x 10 degree regions above and below the plane of the Galaxy. During Phase 2 review for accepted proposals, GALEX mission planning personnel will work with the proposer(s) to determine pointing centers for optimal tiling of the sky. It is not necessary for proposers to specify exact locations of all new observations in a large-area survey of a section (or sections) of the sky.
Proposers should fully specify the region to be tiled and the depth of exposure required, with any other pertinent info, in the "Any comments that apply to multiple observations?" field. (In the case of multiple regions to be tiled, use the "Comments" field on the Observation Form).In the ARK form, they should request a single observation at the approximate center of each contiguous survey region. Each placeholder observation should be entered with the total new observation time for that region, and the region's central coordinates. The total new observation exposure time should sum to the correct, estimated value, and the visibility information should be close to accurate. To estimate total required observing time, assume one tile per square degree and multiply area by required depth of exposure. The science target size entered in the ARK form will need to be set to a value less than 1.2 degrees so that the proposal will validate in ARK, but the true extent of the desired sky coverage should be clearly explained in the "Comments" field.
Responsible NASA Official:
Curator: