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VIII. Post-Cryo Data Release

2. Post-Cryo Data Products

b. Single-Exposure Images, Bit Masks, Uncertainty Maps

The following images highlight examples of anomalies specific to the Post-Cryo data. Anomalies and features seen in the All-Sky Release or specific to the 3-Band Cryo data are covered elsewhere.

i. Image Anomalies and Features

Each figure below shows one row of images per frameset. Each image is 47 arcmin square. From left to right are shown the full single-exposure frames for bands W1 and W2, broken icons for bands W3 and W4 (because these two bands are blank), and a three-color image comprised of blue (W1 only) + green (an average of W1 and W2) + red (W2 only) The frameset number is shown at far left. Readers are encouraged to use the WISE image service at IRSA to preview these same images and to download the FITS files for further study. To aid the reader, values of the frame_ID are provided in the caption of each figure.

Image examples below are divided into the following categories:

Effect from Bright Objects: The character of bright object artifacts in the Post-Cryo data is considerably different from that seen in earlier WISE data. Although most of these effects were seen in the four-band All-Sky data or the 3-band Cryo data, their frequency of occurrence and brightness noticeably increased during Post-Cryo.

Glints

Figure 1 - Single-exposure framesets 09461b060-061. The bright star in frameset 060 produces a large, fan-shaped glint in the following frameset, 061.

Figure 2 - Single-exposure framesets 11556a166-167. The bright star in frameset 166 leaves a nearly vertical glint (often with interesting substructure) in the following frame, 167. This glint is similar to, though less dramatic than, the fan-shaped glint noted above.

Figure 3 - Single-exposure framesets 09732a061-062 (top) and 10261b067-068 (bottom). In both cases, the bright star just off the edge of the preceding frameset has created a large, sickle-shaped glint in the following frameset.

Figure 4 - Single-exposure framesets 10536a043-045 (top) and 11278a091-092 (bottom). In both cases a prominent curved glint is seen preceding the frameset containing a bright star.

Figure 5 - Single-exposure framesets 09052a243-245 (top) and 09542a176-177 (bottom). In the first case, a W1-bright corkscrew-shaped artifact is seen in the frameset preceding a bright star. In the second case, a W1-bright corkscrew (which is more smeared in the vertical direction) follows the frameset containing the bright star L02 Lupi, a semi-regular pulsating star.

Figure 6 - Single-exposure framesets 12345a247-248. A rarely seen round, W1-only glint is seen in the frameset preceding one containing a bright star. This glint may be the collapsed version of the stretched corkscrew-shaped glint seen in the examples noted directly above.

Figure 7 - Single-exposure frameset 11134a139. A rarely seen upward/downward jet-like artifact is seen centered on the bright star at the frameset's edge in W1.

Figure 8 - Single-exposure framesets 09084a245-246. These images show a W2-bright, diagonal glint in the frameset preceding the bright star along with a W2-bright, horizontal corkscrew-shaped glint in the next frameset. The bright star itself just misses falling on either of these image sets.

Figure 9 - Single-exposure framesets 11985b105-107. These images show several different kinds of glints. In the image nearest the off-frame bright star (105), a W1-bright, horizontal corkscrew-shaped glint is seen along with a W2-bright jet emanating both upward and downward from the star's center. The next image (106) shows a fan-shaped glint already covered above. The image following this one (107) shows edge glow discussed here in a later section.

Figure 10 - Single-exposure framesets 11698b022-024 (top) and 12062b193-194 (bottom). The top set of images shows a W2-bright glint from a star falling well off the edge of the arrays. The bottom set of images shows the same type of glint, only less bright.

Figure 11 - Single-exposure framesets 10098a038-039 (top) and 10197b124-125 (bottom). In addition to a two-band glint seen directly below the position of the bright star, there is an additional W2-only banded glint radiating diagnonally from the star's position. This W2-only glint also exhibits a shadow (i.e., lack of flux) near the W2 array edge. The bright star in this case is RW Leonis Minoris, a semi-regular pulsating star.

Figure 12 - Single-exposure framesets 09705a145-148 (top) and 11666a101-102 (bottom). The first example shows a frame (147) impacted with a corkscrew-shaped artifact from a bright star in the following frameset and a fan-shaped glint from a bright star in the preceding frameset. The second example shows two bright stars, each of which throwing a glint on top of the other.

Figure 13 - Single-exposure framesets 10105b160-161 (top) and 10417a009 (bottom). Bright stars (and planets) are not the only sources to leave glint artifacts. As seen further below, the Moon also creates severe glints and, in the examples shows here, so does the occasional bright satellite passage. In the first example, the passage of a bright satellite leaves a W2-only glint in the frameset after the one in which the satellite appeared. In the second example, the glints appear in the same frameset in which the satellite is seen.

Figure 14 - Single-exposure framesets 09826a014-016. Frameset 015 shows what may be a glint artifact, but as the preceding and following framesets show, no bright source is obvious. This glint may have been caused by a bright satellite that passed just outside of the field of view of frameset 015 and was not captured in the images just before or after.

      Glow from off-frame bright star

Figure 15 - Single-exposure framesets 10113a074-076. The presence of a very bright object just outside the field of view can create a bright curtain of light across one or more framesets, as seen here in frameset 075.

Figure 16 - Single-exposure framesets 11350a025-027. The presence of a very bright object (R Doradus) just outside the field of view can also create glow with other morphologies, such as the triagnular shapes seen here in framesets 025 and 027.

Figure 17 - Single-exposure framesets 10869a123-125. The glow morphology seen here, although uncommon, is also caused by a very bright object (the planet Jupiter) just oustide the field of view.

Figure 18 - Single-exposure framesets 12404a150-152. The example shows another uncommon glow morphology, again from a bright object (W Hydrae) just outside the field of view.

Figure 19 - Single-exposure framesets 11334a024-028. The glow pattern from a bright object (R Doradus) just outside the field of view does not always show the symmetry seen in the examples above. Here, the glow of light shows little commonality from one frameset to the next.

      Latents

Figure 20 - Single-exposure framesets 12089a104-106. The bright star (Mira, also known as omicron Ceti) in frameset 104 leaves bright latents in 105 and 106 that are connected, at least in W1, by a vertical line. This vertical line is more prominent in Post-Cryo data than in earlier WISE data.

Figure 21 - Single-exposure framesets 11542a024-028. The bright star R Doradus in frameset 024 leaves latents in framesets 025 through 028. Each latent image has a vertical spike not commonly seen in earlier data sets.

      Unusual patterns in moon glow

Figure 22 - Single-exposure framesets 09166a149-151. Although many of the patterns created by stray moonlight were similar in Post-Cryo to earlier data, a few new effects were noted. Here, stray moonlight leaves an undulating pattern through these three framesets.

Figure 23 - Single-exposure framesets 09165a125-127. In this scan, which was taken one orbit earlier than the one above, the pattern left by stray moonlight in frameset 126 is less bright and less pervasive than that seen in the above example.

Figure 24 - Single-exposure framesets 11921a164-166. The unusual pattern on the W2 array in frameset 165 -- consisting of a bundle of vertical streaks -- is an uncommon moonlight artifact not noted in earlier data.

Figure 25 - Single-exposure framesets 09270a154-158. Although seen in earlier data sets, the presence of this W2-bright vertical stripe in some framesets impacted by moonlight was much more prominent during Post-Cryo.

      Unusual W1 halo around bright stars

Figure 26 - Single-exposure framesets 09342a085 (top), 09372a011 (one row down from top), 09729a138 (middle) 10012a051 (one row up from bottom), and 11701b018 (bottom). In each of these framesets, there is a bright star falling along the middle right of the field of view that has an unusual scattered light pattern in W1 only. Such stars fall at almost exactly the same pixel position, leading us to believe there may be a small surface deposit on the W1 array at that location that causes the asymmetrical halo. Although this effect and its unique location on the W1 array were noted in earlier data, the Quality Assurance reviewers did a more thorough job of noting the peculiarity in Post-Cryo reviewing.

Electronic Artifacts: Variations in the background levels for some of the readout channels were sometimes more obvious in Post-Cryo data than they had been before. Other electronic behavior, namely the "TV test" pattern phenomenon noted in earlier WISE data, appeared to happen with slightly higher frequency. One new phenomenon, called the "exploding" pixel effect here, has an unknown origin and is seen only in Post-Cryo data.

      Increased channel noise

Figure 27 - Single-exposure framesets 10945b130-132. Increased backgrounds and noise are seen in three readout channels (which run vertically) in the W1 array in frameset 131.

Figure 28 - Single-exposure frameset 11305a150. Increased backgrounds and noise are seen in one W2 readout channel (which runs horizontally) here. Note that the backgrounds in this channel undulate in intensity left to right.

Figure 29 - Single-exposure framesets 11834a073-074. Not all noisy/elevated channels are anomalous for their entire length across the array. In frameset 073, note that four W1 channels are high relative to the rest of the array but that the problem area spans only about one quarter of each channel. Note also other channel noise at both W1 and W2 in this and the other frameset shown here.

      "TV test" patterns

Figure 30 - Single-exposure framesets 10141a233-235. A substantial fraction of both the W1 and W2 array shows elevated backgrounds in frameset 234 due to an electronic glitch of unknown origin.

Figure 31 - Single-exposure framesets 09469b048-050. The same effect as that shown above is seen in frameset 049 here, except that the background levels are far less elevated.

Figure 32 - Single-exposure framesets 11302a211-213. In this example, the background elevation in frameset 212 has the same overall pattern as the two examples above, but the levels are just barely detectable over the mean background levels of the adjacent framesets.

Figure 33 - Single-exposure framesets 10389a191-193. A single-frameset glitch has affected the background levels over part of 192.

Figure 34 - Single-exposure framesets 10906a113-115. The glitch here has affected the background levels over most of frameset 114.

Figure 35 - Single-exposure framesets 09576a257-259. The electronic glitch seen here adds noise across the arrays and increases the background primarily along one channel each in W1 and W2 in frameset 258.

Figure 36 - Single-exposure framesets 10792a043-045. The electronic glitch has increased the background and noise levels across the entire arrays in frameset 044.

      "Exploding" pixel effects in the W2 array

Figure 37 - Single-exposure framesets 10897b117-124. There are three known instances of the "exploding pixel" phenomenon. This is the first one in time. In frameset 118, background levels skyrocket and subsequent frames show an area on the W2 array where a transient event slowly decays. The pixel at the center of this "latent" is approximately the same as that in the next two examples.

Figure 38 - Single-exposure framesets 11984a146-154. This is the second instance of the "exploding pixel" effect. Frameset 147 failed processing but showed elevated background levels like those in frameset 118 in the example above.

Figure 39 - Single-exposure framesets 12125b146-153. This is the third and final (in time) instance of the "exploding pixel" effect. Frameset 148 shows the characteristic skyrocketing of the background levels, and subsequent framesets show the latent decay around the familiar spot on the W2 array.

Particle Hits: Particle hits were much more dramatic and more common in post-cryo data.

      Tadpole-shaped hits

Figure 40 - Six examples of single-exposure framesets showing tadpole-shaped particle hits. The first, 10842b063, shows a W1 particle hit with a large, round head and long, spotty tail. The second, 10033b076, shows the same effect in W2. The third example, 11125a073, shows a W1 particle hit with a large, elongated head and double tail. The fourth example, 10961a037, shows a large, elongated head with slender tail in W2. The last two examples, 11622a070 and 09561a045, show W2 particle hits with smaller heads and very straight, sharp-edged tails. The second of these even has a wide gap in the tail itself.

      Tail-less tadpoles

Figure 41 - Examples of single-exposure framesets showing particle hits with a prominent head only. The top example (09797b091) shows a large particle hit in W2. The middle example (08869a016) shows a particle hit in both bands. The bottom example (12462a271) shows an elongated hit in W1.

      Head-less tadpoles

Figure 42 - Single-exposure framesets 10413a074 (top) and 09109a224 (bottom). The top frameset shows a long tail of particle hits in W1, and the second shows the same effect in W2.

      Diffuse particle showers

Figure 43 - Single-exposure framesets, from top to bottom: 10174a084, 10338b106, 10338b057, and 10450b086. The top two show examples of diffuse particle showers in W1, and the bottom two show examples in W2.

      Latents from particle hits

Figure 44 - Single-exposure framesets 10365b088-089 (top) and 12017b053-054 (bottom). The saturated cores of the particle hits in W2 in 10365b088 and 12017b053 leave a W2-only latent on the array in the frame that follows.

Processing Features: In rare instances, anomalies were introduced into the data by the pipeline itself, either as a result of unintended consequences created when trying to mitigate another problem, or as a result of a processing step's inability to execute.

      Channel offsets

Figure 45 - Single-exposure framesets 10141a222 (top) and 11306b025-026 (bottom). Code intended to mitigate noise in array channels could, if conditions were right, introduce background offsets. In the top example, extended nebulosity has confused the code and as a result two channels in W1 (one high, one low) as well as one channel in W2 (high) have been badly corrected. In the bottom example the two rightmost channels of the W1 array have been similarly affected due to excessive edge glow from an off-frame bright star.

Figure 46 - Single-exposure frameset 09546a168, with an expanded view of the three-color image shown just below it. Here, the code was influenced by the presence of two similarly bright stars roughly one readout channel apart. In this case the background between the two stars has been badly corrected so that a small rectangle with higher counts results.

      Lack of dynacal corrections

Figure 47 - Single-exposure framesets 10681d018-022 (top) and 10678a217-221 (bottom). Framesets 019, 018, and earlier in scan 10681d as well as framesets 220, 221, and later in scan 10678a are noisy and non-flat, indicating that dynacal corrections were not applied to those framesets. This situation arose for science data just before or after a run of non-science test data (such as test data taken to judge image quality as a function of scan mirror rate). In these instances there are not enough historical framesets either before or after the science data, so a dynacal correction is not attempted.

Missing Data: The pipeline is robust against the occasional missing frame. Fortunately, this situation arose only once during the post-cryo period.

Figure 48 - Single-exposure frameset 11042a189. This is the only instance during post-cryo of a frameset missing one band of data. In this case, the W2 data were not successfully retrieved from the spacecraft (and as a result, a false color image could also not be created).

Passages of Nearby Objects: Passages of very nearby objects were generally less prominent in post-cryo data because these objects are brightest at the longer wavelength W3 and W4 bands. A few examples with out-of-focus, very nearby objects are shown to demonstrate their characteristics in post-cryo data, and one example of a more distant but very bright passage is also shown.

Figure 49 - Single-exposure frameset 12401a106. The very nearby object is out of focus and appears as a large washer-shaped object brighter in W2 than in W3.

Figure 50 - Single-exposure framesets 10141a240-246. Several close, out-of-focus objects pass through the field of view during this sequence of frames. The most obvious one is the more distant object seen in frameset 240. The framesets that follow show closer objects that fill or overfill the field of view.

Figure 51 - Single-exposure framesets 10552a186-189. A very bright object passes through the field of view while framset 187 is being read out. It leaves a W1-bright latent in the subsequent frameset.

Astrophysical Objects Possibly Mistaken for Artifacts: Certain astrophysical objects can mimic anomalies.

Figure 52 - Single-exposure framesets 09157b104 (top), 09554a134 (middle), and 11722a129 (bottom). In all three of these a W2-bright, extended source is seen but none of these is a latent artifact. Each is a known comet -- Comet McNaught 2009K5 (top), Comet Gunn 65P (middle), and Comet Tempel 10P (bottom).

Anomalies of Unknown Origin: Some oddities seen in the Post-Cryo data currently lack an explanation.

Figure 53 - Single-exposure framesets 10104a169-171. The W2-bright artifact in frameset 170 has unknown origin.

Figure 54 - Single-exposure framesets 10233b128-131. The artifact seen in frameset 129, which is similar to the one seen in the example directly above except that this one is bright in both W1 and W2, has unknown origin.

Figure 55 - Single-exposure framesets 10570b094 (top), 10573a070 (just below top), 10574a093-094 (just below bottom), and 10577a070 (bottom). The bright object in each of these framesets is the Mira variable star RR Phoenicis as seen on four consecutive WISE orbits. The large, scattered light halo around RR Phe seen only in the W1 band of 10573a070 is of unknown cause.


Last update: 2013 May 20

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