III. AllWISE Multiepoch Photometry Database

The cntr_mf value is formed by making the source_id_mf into an integer, in the format: RRRRsDDDtrevIIIIII, where

• RRRR = Tile center RA in deci-degrees, truncated not rounded (e.g. RRRR=int[10*ra]), as in the coadd_id.
• s = Tile center Declination sign translated from "p" or "m" into "1" or "0", respectively.
• DDD = Tile center Declination in deci-degrees, as in the coadd_id. For positive declinations, the tenths of a degree is truncated not rounded (e.g. DDD=int[10*dec]). For negative declinations, the tenths of a degree is always truncated leftward on the number line (e.g. DDD=ceil[10*abs(dec)].
• [trev] = Disambiguation string, translated where necessary into digits corresponding to the letters' places in the alphabet.
  • t - Tile type translated into two digits, zero-filled ("a" = "01").
  • r - Data Release identifier translated into a single digit (for AllWISE: "c" = "3").
  • e - Cryogenic Survey Phase ("5" = AllWISE [Full Cryogenic + 3-Band cryo + Post-Cryo]).
  • v - Processing version.

  The translated disambiguation string is always 01351 for Tiles in the AllWISE Catalog/Reject Table.

• IIIIII = six-digit, zero-filled, sequential extracted source number, src, within the Tile.

For example, a source in the Tile 3041m137_ac51, with a source_id_mf of '3041m137_ac51-012345', has a cntr_mf value of 3041013701351012345.

• RRRRsDDD_[trev] = the coadd_id
• IIIIII = six-digit, zero-filled, sequential extracted source number, src, within the Tile.

For example, the first source extracted in Tile 3041m137_ac51 has Catalog has a source_id_mf of 3041m137_ac51-000001.

• 0 - the source is not actively deblended.
• 1 - the source is actively deblended.

This is the same for all Multiepoch Source Database entries corresponding to the same object.

• D,d - Diffraction spike. Source may be a spurious detection of (D) or contaminated by (d) a diffraction spike from a nearby bright star on the same image, or
• P,p - Persistence. Source may be a spurious detection of (P) or contaminated by (p) a short-term latent image left by a bright source, or
• H,h - Halo. Source may be a spurious detection of (H) or contaminated by (h) the scattered light halo surrounding a nearby bright source, or
• O,o (letter "o") - Optical ghost. Source may be a spurious detection of (O) or contaminated by (o) an optical ghost image caused by a nearby bright source on the same image.
• 0 (number zero) - Source is unaffected by known artifacts.

A source extraction may be affected by more than one type of artifact or condition. In this event, the cc_flags value in each band is set in the following priority order: D,P,H,O,d,p,h,o,0. The full tally of artifacts affecting a source in each band is given in the w?cc_map and w?cc_map_str columns.

CAUTION: Non-zero cc_flags values in any band indicate that the measurement in that band may be contaminated and the photometry should be used with caution.

This is the same for all Multiepoch Source Database entries corresponding to the same object.

• "1" - The object is in the AllWISE Source Catalog.
• "0" - The object is in the AllWISE Reject Table.

This is the same for all Multiepoch Source Database entries corresponding to the same object.

The cntr value is an integer converted from the string: RRRRsDDDvIIIIINNNN as follows

• RRRR = Tile center RA in deci-degrees, truncated not rounded (e.g. RRRR=int[10*ra]), as in the coadd_id.
• s = Tile center Declination sign translated from "p" or "m" into "1" or "0", respectively.
• DDD = Tile center Declination in deci-degrees, as in the coadd_id. For positive declinations, the tenths of a degree is truncated not rounded (e.g. DDD=int[10*dec]). For negative declinations, the tenths of a degree is always truncated leftward on the number line (e.g. DDD=ceil[10*abs(dec)].
• v = Processing version number from the Tile disambiguation string.
• IIIIII = six-digit, zero-filled, sequential extracted source number, src, within the Tile.
• NNNN = four-digit, zero-filled, sequential number of the single-exposure frame measurement of the object. This number is in observation time order with each of the individual measurements having values of "0001", "0002", ....

For example, the 24 Multiepoch Photometry Database entries that correspond to the entry in the AllWISE Source Catalog with source_id_mf = '3041m137_ac51-000001' have cntr values of:

3041013710000010001,
3041013710000010002,
3041013710000010003,
...
3041013710000010024.

The frame_id has the general form SSSSSxMMM, where

• SSSSS is a zero-filled, five-digit integer that is twice the WISE orbit number. The orbit number increments each time the flight system passes the north ecliptic pole (NEP). Orbit number 1 was defined to start with the fictitious NEP passage immediately prior to WISE launch.
• x   is a letter assigned based on sequential count of scans started in a specific half-orbit. The first scan has x="a", the next x="b", up to a maximum of x="d".
• MMM is a zero-filled three-digit number that gives the individual frameset in the scan. The frameset number is computed based on time bins which count from the scan start time:
  fr_num = int[(((frame_utc - dt_beg) - scan_start_utc)/bin_size] + 1

  where

  • int[] means truncate to an integer
  • frame_utc is the nominal frame exposure center UTC (when the boresite crosses the image center) in seconds
  • dt_beg is 4.4s. This is a nominal offset to approximate when the exposure began
  • scan_start_utc is the scan start time in seconds
  • bin_size is 10s.

  For example, a frame with a start time 1234 secs after the scan start time would have a frame number of 124.

  N.B.

  • Frame_num is not a frameset sequence number
  • As a result of using a 10 sec bin, every 11th frame skips a number, so it is normal to see breaks in the frame numbering and it doesn't indicate missing data.
  • Because frameset numbering is based on the predicted scan start time from the survey plan, and because frameset data may not start being acquired until well after the start of the scan, frameset numbers often do not start at 1 for a scan.

The first frameset whose data are used in the AllWISE Multiepoch Source Database is frame 001 from scan 00712a, the first scan after the NEP crossing in the 356th WISE orbit. The final frameset included Database frame 216 from scan 12514a, the first scan after the NEP crossing in the 6257th WISE orbit.

CAUTION: Single-exposure source measurements from framesets having qi_fact<1.0 should be used with caution. They were extracted from framesets in which the images are smeared because of residual flight system motion. Position and and profile-fitting flux measurements may be degraded.

SAA separation. This column contains the angular separation on the sky, in degrees, between the apparent position of WISE and the boundary of the South Atlantic Anomaly (SAA) at the time of observation for the frameset on which this entry was extracted. Positive values indicate that WISE was outside of the SAA boundary. Negative values indicate that WISE was within the SAA boundary.

CAUTION: Single-exposure source measurements from framesets having negative or small positive (< 5.0) values of saa_sep should be used with caution. The flux of charged particles is very high within the SAA producing a very high incidence of radiation hits that can contaminate measurements on the individual exposures.

CAUTION: Single-exposure source measurements from framesets having moon_masked=1 in any band should be used with caution. Framesets in the moon mask areas may have large scale image artifacts that induce spurious detections or contaminate real source measurements.