Spitzer Documentation & Tools
Rogue Pixel Masks

A rogue pixel is a pixel with abnormally high dark current and/or photon responsivity (a "hot" pixel) that manifests as pattern noise in an IRS BCD image. We identify rogue pixels using the dark current measurements taken for calibration of the IRS arrays (observations of a very dark spot in the sky). The rogues are chosen by thresholding a high spatial frequency "component" of the dark current image. All pixels in the high frequency image with dark current greater than 4-sigma are labeled rogue.

A rogue mask is a fits file containing a 128 x 128 image with all detected rogue pixels set to 1, and all other pixels set to 0. Since rogue pixels are a time-dependent phenomenon, rogue masks are available for every IRS channel and campaign starting from IRS nominal operations campaign 1 (IRS1) and extending to the end of the Spitzer cold mission. Observers who need to correct for the effects of rogue pixels on their data should use a rogue mask developed as close in time to the date of observation as possible. Campaign-dependent rogue masks are available from the table below. Alternatively, all masks from all campaigns are available as a single tar file (TGZ, 363 KB). The mask file names are of the format b?_rmask_IRS?[?].fits, where the first ? is the channel number (SL=0, SH=1, LL=2, LH=3) and the second ?[?] is the campaign number.

The file campaigns.txt (Plain Text, 1 KB) campaigns.txt provides the translation between IRS campaign number (starting at 1) and the SSC campaign label given in the FITS header keyword CAMPAIGN in your data (starting at IRSX002500).

After downloading the appropriate masks, users should consult the Data Analysis and Tools section of the Spitzer Heritage Archive for advice on how to use these rogue files. In particular, see the IRSCLEAN_MASK software page and the Data Analysis Cookbook.

SL module SH module LL module LH module
Campaign1SL_C1SH_C1LL_C1LH_C1
Campaign2SL_C2SH_C2LL_C2LH_C2
Campaign3SL_C3SH_C3LL_C3LH_C3
Campaign4SL_C4SH_C4LL_C4LH_C4
Campaign5SL_C5SH_C5LL_C5LH_C5
Campaign6SL_C6SH_C6LL_C6LH_C6
Campaign7SL_C7SH_C7LL_C7LH_C7
Campaign8SL_C8SH_C8LL_C8LH_C8
Campaign9SL_C9SH_C9LL_C9LH_C9
Campaign10SL_C10SH_C10LL_C10LH_C10
Campaign11SL_C11SH_C11LL_C11LH_C11
Campaign12SL_C12SH_C12LL_C12LH_C12
Campaign13SL_C13SH_C13LL_C13LH_C13
Campaign14SL_C14SH_C14LL_C14LH_C14
Campaign15SL_C15SH_C15LL_C15LH_C15
Campaign16SL_C16SH_C16LL_C16LH_C16
Campaign17SL_C17SH_C17LL_C17LH_C17
Campaign18SL_C18SH_C18LL_C18LH_C18
Campaign19SL_C19SH_C19LL_C19LH_C19
Campaign20SL_C20SH_C20LL_C20LH_C20
1Campaign21.1SL_C21.1SH_C21.1LL_C21.1LH_C21.1
1Campaign21.2SL_C21.2SH_C21.2LL_C21.2LH_C21.2
1Campaign21.3SL_C21.3SH_C21.3LL_C21.3LH_C21.3
1Campaign21.4SL_C21.4SH_C21.4LL_C21.4LH_C21.4
Campaign22SL_C22SH_C22LL_C22LH_C22
1Campaign23.1SL_C23.1SH_C23.1LL_C23.1LH_C23.1
1Campaign23.2SL_C23.2SH_C23.2LL_C23.2LH_C23.2
Campaign24SL_C24SH_C24LL_C24LH_C24
Campaign25SL_C25SH_C25LL_C252,4LH_C25
Campaign26SL_C26SH_C26LL_C264LH_C26
Campaign27SL_C27SH_C27LL_C274LH_C27
Campaign28SL_C28SH_C28LL_C28LH_C28
Campaign29SL_C29SH_C29LL_C29LH_C29
Campaign30SL_C30SH_C30LL_C30LH_C30
Campaign31SL_C31SH_C31LL_C31LH_C31
Campaign32SL_C32SH_C32LL_C32LH_C32
Campaign33SL_C33SH_C33LL_C33LH_C33
Campaign34SL_C34SH_C34LL_C34LH_C34
Campaign35SL_C35SH_C35LL_C35LH_C35
Campaign36SL_C36SH_C36LL_C36LH_C36
Campaign37SL_C37SH_C37LL_C37LH_C37
Campaign38SL_C38SH_C38LL_C38LH_C38
Campaign39SL_C39SH_C39LL_C39LH_C39
Campaign40SL_C40SH_C40LL_C40LH_C40
Campaign41SL_C41SH_C41LL_C41LH_C41
Campaign42SL_C42SH_C42LL_C42LH_C42
Campaign43SL_C43SH_C43LL_C43LH_C43
Campaign44SL_C44SH_C44LL_C44LH_C44
Campaign45SL_C45SH_C453LL_C45LH_C45
Campaign46SL_C46SH_C46LL_C46LH_C46
Campaign47SL_C47SH_C47LL_C47LH_C47
Campaign48SL_C48SH_C48LL_C48LH_C48
Campaign49SL_C49SH_C49LL_C49LH_C49
Campaign50SL_C50SH_C50LL_C50LH_C50
1Campaign51.1SL_C51.1SH_C51.1LL_C51.1LH_C51.1
1Campaign51.2SL_C51.2SH_C51.2LL_C51.2LH_C51.2
Campaign52SL_C52SH_C52LL_C52LH_C52
Campaign53SL_C53SH_C53LL_C53LH_C53
Campaign54SL_C54SH_C54LL_C54LH_C54
Campaign55SL_C55SH_C55LL_C55LH_C55
Campaign56SL_C56SH_C56LL_C56LH_C56
1Campaign57.1SL_C57.1SH_C57.1LL_C57.1LH_C57.1
1Campaign57.2SL_C57.2SH_C57.2LL_C57.2LH_C57.2
1Campaign58.1SL_C58.1SH_C58.1LL_C58.1LH_C58.1
1Campaign58.2SL_C58.2SH_C58.2LL_C58.2LH_C58.2
1Campaign58.3SL_C58.3SH_C58.3LL_C58.3LH_C58.3
1Campaign59.1SL_C59.1SH_C59.1LL_C59.1LH_C59.1
1Campaign59.2SL_C59.2SH_C59.2LL_C59.2LH_C59.2
Campaign60SL_C60SH_C60LL_C60LH_C60
1Campaign61.1SL_C61.1SH_C61.1LL_C61.1LH_C61.1
1Campaign61.2SL_C61.2SH_C61.2LL_C61.2LH_C61.2

1 This campaign was split into a number of mini-campaigns. We derived a single rogue mask per channel using dark calibration data for the entire campaign, and then copied the masks into multiple files (one per mini-camaign) per channel. All sub-campaign rogue masks are identical, but are associated with a different campaign label. Campaign IRS21 was split into four mini-campaigns due to intervening short IRAC and MIPS campaigns for Target of Opportunity observations. IRS23 was split into two campaigns due to an intervening short MIPS campaign. IRS51 was split into two campaigns to observe a gamma ray burst afterglow with IRAC. IRS57 was split into two campaigns to execute an 8-hour mini campaign with IRAC. IRS58 was split into three campaigns to execute two mini campaigns with IRAC. IRS59 was interrupted by an error causing the electronics to reset. IRS61 was split into two parts due to an IRAC 1-day mini campaign.

2The number of Long-High rogue pixels suddenly dropped in campaign 25. The bias voltage on the Long High array was reduced from 2.0 to 1.6 volts in IRS25, reducing the dark current and photon sensitivity of the array. The main reason for this change was to reduce the strength and number of rogue pixels and improve the signal to noise in observations of faint sources. For many purposes, the data and rogue pixel masks before and after the bias change should be treated as coming from two different instruments.

3The number of Long-Low rogue pixels suddenly dropped in campaign 45. For the same reason the bias was changed in Long High, in IRS45 the bias voltage on the Long Low array was reduced from 1.8 to 1.6 volts and the array temperature was reduced from 4.4 to 4.1 K. As for LH, this reduced the dark current and photon sensitivity of the array. In the case of Long Low, the number of detected rogue pixels decreased to 1/3 of its previous value. This combination of effects increased the overall signal-to-noise ratio in the LL array by up to 60%, depending on wavelength.

4The campaign 25-27 Long High rogue masks changed on 08 February 2006. All IRS data are processed such that certain "permanently bad" pixels are automatically excluded from consideration and set to the value NaN (not a number). Prior to February 8, the Long High dark measurements for all campaigns were processed using an old "permanently bad" mask, or "pmask", derived at the old Long High bias setting. Thus, many pixels that were actually well-behaved at the new bias were excluded from consideration. Using a new pmask, we were able to open up many pixels that had previously been designated NaN. Unfortunately, we also opened up a set of pixels that are rogues at the new bias, about 200 of the excluded pixels.