Archive Pipeline Products

Bit definition for IRAC pmask

Bit #    Condition
---      --------------------------------------------
  0      Not set
  1      Not set
  2      Not set
  3      Not set
  4      Not set
  5      Not set
  6      Not set
  7      Dark current too variable (dark calibration accuracy will be unacceptably low)
  8      Response to light too variable (photometric accuracy will be unacceptably low)
  9      Pixel response to light is too high (unacceptably fast saturation)
 10      Pixel dark current is too excessive (pixel is hot)
 11      Not set
 12      Not set
 13      Not set
 14      Pixel's response to light is too low (pixel is dead)
 15      Reserved: sign bit

IRAC pmasks

Pmasks were made at intervals of a few weeks to months, with reduced frequency later in the mission as the variation in bad pixels is seen to be small.

The masks were created by taking darks and flats from five campaigns close to the epoch indicated in the mask name (the exception to this are the January 2005 and February 2005 mask sets which were made from data either side of a solar storm at the end of January 2005). Noise (RMS) images were made from the data in each dark and flat AOR. Pixels with values more than twice the median in the RMS images, or which were dead (<0.01 times the median noise) were flagged. If these pixels were flagged consistently in each of the dark or flat AORs they appeared in the pmask. Images of persistently saturated pixels in the darks were also made (though in practice none have been found so far), along with masks for the amplifier glow in channels 3 and 4 (derived from pre-flight data).

Other keywords in the header give the exact timeranges over which the pmasks are valid both in spacecraft clock time (SCLKSTRT and SCLKEND) and in UT (STRTDATE, ENDDATE).

Note that these pmask sets supercede previous versions, which were typically more aggressive (but also less consistent), in this set only bad pixels persistent over five or more campaigns are masked.

Supermasks
-----------------

In addition to the epochal pmask sets, we have constructed two sets of pmasks based on all the epochs. The "ormasks" consist of all the bad pixels ever recorded in a given channel throughout the mission flagged with bits 7,8,9,10 or 14. The "andmasks" consist of only those pixels present in all the pmasks in a given channel flagged with 7,8,9,10 or 14. Only bit 0 is used for these masks as the bad pixels are combined irrespective of their origin.

Download IRAC pmasks (updated 21 Mar 08)
Please read the included `README' file carefully and note which set of pmasks to use so that you use the set that is applicable to the date when your observations were taken.

Spitzer Post-BCD Mosaicer: Input parameter for Pmasks

PMask_Fatal_BitPattern = 32767 (take into account all set bits)

If you have high background observations (probably all 30 second and higher frametimes, and shorter frametimes close to the Ecliptic plane), you probably do not need to mask the amplifier glow (bit 10) in channel 3 and 4 pmasks, giving a fatal bit pattern of 17280.

NOTE: All the pmasks given in this new package are in BCD orientation and therefore no flipping is required:

USE_FLIPPED_PMASK = 0 (for all channels)

Go back to IRAC Data Products page