# Updates since DR9

This page documents some of the main updates to the Legacy Surveys since Data Release 9.

## General changes

• DR10 only contains updates for the south part of the Legacy Surveys from new imaging with DECam. Northern areas can be obtained from DR9 (see, e.g., the status page).

• The sweep files are now partitioned into 5° x 5° areas rather than 10° x 5° areas.

## Changes for optical data

• Multiple $i\hbox{-}\mathrm{band}$ quantities have been added to the Tractor catalogs and the sweep files.

• Gaia quantities included in files and catalogs are now drawn from Gaia EDR3.

• Note, though, that the astrometric solution for DR10 was still calculated using positions and proper motions from Gaia DR2.

• The MASKBITS bitmask is now 32-bit rather than 16-bit, as a new bit called SUB_BLOB was added. This bit is described on the DR10 bitmasks page under MASKBITS.

• The CCD_CUTS bitmask is now 64-bit rather than 32-bit, as two new bits called PHRMS_S7 and DEPTH_CUT_2 were added. These bits are described on the DR10 bitmasks page under CCD_CUTS.

• The Tractor catalogs contain a new per-band quantity called ngood_x where x is one of $g$, $r$, $i$ or $z$. These quantities record the number of good (unmasked) images that contribute to a source in a particular band at a particular pixel-location. Prior to DR9, only nobs_x (the total number of images that contributed to a source in each band) were recorded in the Tractor catalogs, which created an inconsistency with the "nexp" pixel-maps in the image stacks (which only record the number of good images). So, ngood_x is recorded to allow a direct mapping between the number of good images in the Tractor catalogs and image stacks.

• As an example of the difference, for saturated sources one would expect ngood_x and the "nexp" pixel maps to be zero, but nobs_x to correspond to the total number of exposures that contributed to the source.

• The addition of ngood_x fixes a known issue from DR9.

## Changes for WISE data

• The WISE imaging has been updated to include observations through the 7th year of the NEOWISE W1/W2 data.

• The potential number of unWISE epochs has been expanded for the WISE light curves (e.g. columns such as lc_flux_w1 in the Tractor catalogs can now have up to 17 entries).