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II. NEOWISE Single-exposure Source Database

II.3. Advice for Using the Single-exposure Source Database


The NEOWISE Single-exposure Source Database contains multiple, independent detections of solar system, galactic and extragalactic sources made on all Single-exposure images taken during the first seven years of survey operations. All detections are included from all images, regardless of the quality of the image, and the quality of the detections.

II.3.a. Selecting Detections from Good Quality Framesets

The NEOWISE Single-exposure Source Database contains all detections made on all of the Single-exposure images, regardless of the quality of those images. Some of the individual Single-exposure framesets are degraded by image smearing due to spacecraft motion, electronic noise, scattered light from the moon or other very bright objects near the field-of-view (e.g. III.2.c). The most reliable detections, and those with the least likelihood of contamination, can be identified using scores assigned during the Quality Assurance process in the Scan/frame Pipeline processing, or other metadata that is provided with each Database record.


Figure 1 - 10'x10' sections of three NEOWISE W1 Single-exposure images centered on α,δ=139.1192°,-26.0819° taken at different times. (left) Nominal. (center) Smeared image due to spacecraft jitter. (right) Image taken when the spacecraft was within the SAA.

Figure 2 - 15'x15' sections of two NEOWISE W1 Single-exposure images centered on α,δ=326.8107°,-0.4080° taken at different times. (left) Nominal. (right) Image that is contaminated by a diffraction spike from the moon.

II.3.b. Selecting Reliable Detections

The NEOWISE Single-exposure Source Database contains all source extractions from all Single-exposure images produced during Scan/frame processing regardless of their reliability. In addition to detections of real solar system, galactic and extragalactic sources, the Database contains spurious detections of noise excursions, transient events such as hot pixels, charged particle strikes, and satellite streaks, and image artifacts caused by bright sources such as latent images, diffraction spikes, and optical ghosts. In this section, we present suggestions on how to use the flags and metadata available with the Single-exposure Source Database entries to select extractions that are preferentially reliable source detections.

Most but not all of these tips pertain to both stationary background sources and moving solar system sources. Suggestions specific to identifying reliable solar system object detections are given in II.3.c.

One of the best ways to verify the reliability of a Single-exposure Source Database detection is to examine it on the NEOWISE Single-exposure Images. For stationary sources, it is also valuable to examine the position on the AllWISE Atlas Images that are both deeper than the Single-exposure images and benefit from pixel outlier rejection that suppresses transient pixel events.

In addition to visually examining their images, reliable detections in the Single-exposure Source Database can be selected preferentially using some or all of the following criteria:


II.3.c. Identifying Reliable Solar System Object Detections

First, read sections II.3.a and II.3.b above to familiarize yourself with identifying reliable source detections in general.

The best way to identify Single-exposure Source Database entries that are reliable detections of solar system objects is to select entries that are part of a Moving Object Tracklet that was vetted by the IAU Minor Planet Center (MPC). The procedure for retrieving confirmed NEOWISE small body detections from the MPC Observations Database and then searching for them in the NEOWISE Single-exposure Source Database is described in IV.3.c.iii.

NEOWISE Single-exposure Source Database entries that are in close proximity to the predicted position of a known solar system object at the time of the Single-exposure may be flagged as a solar system object association (sso_flg=1). These are not confirmed solar system object detections. The majority of such flagged Database entries are either a chance association with a stationary background source or spurious detection of noise or other artifacts. There are over 13 million entries in the Source Database with sso_flg=1, but only ~1.1 million NEOWISE solar system object detections have been confirmed by the MPC during the first seven years of survey operations.

The Single-exposure Source database contains a small number of real solar system object detections that either were not reported to the MPC as part of Moving Object Tracklets, or that are not flagged with sso_flg=1. The automated moving object detection system will not link detections of very fast moving objects that were in the NEOWISE field-of-view fewer than five times, or objects whose apparent acceleration and change in direction exceeds the rate parameters allowed by the system. Solar system objects that were discovered after the epoch of the orbital elements file used for the known object searching during NEOWISE data processing (IV.2.e.ii) will not be flagged as possible solar system object associations.

Recovery of solar system object detections not associated with Moving Object Tracklets and/or not flagged as known objects can be done using the Solar System Object search facilities of the IRSA WISE/NEOWISE image and database search interfaces. Searches may be executed using object names or orbital elements.

Care must still be taken when interpreting Single-exposure Source Database entries that are returned by queries using the Solar System Object search capabilities. Reliable solar system object detections should satisfy most of the following criteria:

Masiero et al. 2020 (PSJ 1, 9) illustrate how detections of NEOs manually-recovered from NEOWISE Single-exposures should be vetted.


Last update: 22 March 2021


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