II. User's Guide to the WISE Preliminary Data Release


4. Ancillary Products

i. Known Solar System Object Possible Association List Format

The Known Solar System Object Possible Associations List is a compendium of asteroids, comets, planets or planetary satellites, with orbits known at the time of WISE first-pass data processing, that were predicted to be within the field-of-view at the time of individual WISE exposures. Individual objects were observed multiple times, so may have multiple entries in the list. When the predicted position of a solar system object is in proximity to a detection in the WISE single-exposures, the WISE source position and brightness information are also provided.

CAUTION: This is not a vetted list of solar system object detections. For a reliable, well-vetted list of WISE solar system object detections, please use the Moving Object Tracklets.

Users are strongly encouraged to read the Cautionary Notes to understand the limitations of the Known Solar System Object Possible Associations List.

i. Table Format Description

The following table contains brief descriptions of the parameters provided for each record the WISE Preliminary Data Release Known Solar System Object Possible Association List.

The columns in the following table are:

Column NameFormatUnitsnullsDescription 
cntr%10d----no Unique identification number for the Atlas Image Frame Cross Reference table entry created sequentially in the order of the Archive load processing.  
objid%36s----yesSolar System Object (SSO) identifier. The identifier field may contain any combination of MPC number, object name (e.g., Ceres), and (provisional-)designation; comets and planets have no MPC numbers.  
t%1s----yes Type of Solar System object:
  • A - Asteroid, numbered
  • U - Asteroid, unnumbered
  • C - Comet, periodic
  • N - Comet, non-periodic
  • P - Planet
  • S - Planetary Satellite
  • X - Unknown
 
ra%10.6fdegyesPredicted Right Ascension (J2000) of SSO at time of WISE observation.  
dec%10.6fdegyesPredicted Declination (J2000) of SSO at time of WISE observation.  
mu%7.3farcsec/secyesPredicted proper motion of SSO at time of WISE observation.  
theta%5.1fdegyesDirection of predicted proper motion (E of N) of SSO at time of WISE observation.  
emj%4.1fsrcsecyesSemimajor axis of the error ellipse of the SSO predicted position.  
emn %4.1farcsecyesSemiminor axis of error ellipse of the SSO predicted position.  
erang%5.1fdegyesPosition angle of emj axis (E of N).  
rhelio%9.5fAUyesSSO heliocentric distance at the time of the WISE observation.  
rtopo%9.5fAUyesSSO Topocentric (spacecraft) distance at the time of the WISE observation.  
phase%7.3fdegyesSSO phase angle at the time of the WISE observation.  
amag%5.2fmagyesSSO absolute magnitude.  
vmag%6.3fmagyesSSO predicted visual magnitude at the time of the WISE observation.  
slope%5.2f----yesSlope parameter for computing phase-dependent term in visual mag  
perdist%10.7fAUyesSSO perihelion distance at the time of the WISE observation.  
ecc%9.7f----yesSSO orbital eccentricity  
incl%12.8fdegyesSSO orbital inclination  
pv1%11.8s----yesSSO orbit P vector (unit vector of Sun toward perihelion) X component  
pv2%11.8f----yesSSO orbit P vector (unit vector of Sun toward perihelion) Y component  
pv3%11.8f----yesSSO orbit P vector (unit vector of Sun toward perihelion) Z component  
qv1%11.8f----yesSSO orbit Q vector (unit vector orthogonal to P in orbit plane, right-handed about orbital angular momentum vector) X component  
qv2%11.8f----yesSSO orbit Q vector (unit vector orthogonal to P in orbit plane, right-handed about orbital angular momentum vector) Y component  
qv3%11.8f----yesSSO orbit Q vector (unit vector orthogonal to P in orbit plane, right-handed about orbital angular momentum vector) Z component  
pertime%13.5mjdateyesSSO orbit perihelion passage time, modified Julian date  
err%4.1f----yesSSO orbital element quality estimate  
mjd%12.6fmjdateyesModified Julian date of the mid-point of the observation of the frameset within which the FOV the SSO is predicted to fall.  
scan_id%6s----no Identifier of the WISE survey scan in which the predicted position of this SSO was was observed.

Scan_id is a six character string that identifies a block of survey exposures that are acquired between two flight system maneuvers, such as reorientation of the instrument boresite near the ecliptic poles, or slews to acquire TDRSS for data downlink contacts. Because maneuvers often take place near the ecliptic poles, the scan number is roughly associated with a half-orbit's worth of images. However, scans can cover less or more than half of the arc between ecliptic poles.

The scan_id has the general form SSSSSx, 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" for scans in the Preliminary Release.

The first scan whose data are used in the Preliminary Data Release is scan 00936a. This was the first scan after the NEP crossing in the 468th WISE orbit. The final scan included in the Release is 04125a, the first scan after the SEP crossing in the 2062nd WISE orbit.

 
frame_num%3d----no Number of the Single-exposure frameset within which lies the predicted position of the SSO during the WISE observation.

Frame_num has the general form MMM, a zero-filled three-digit number.

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.
 
source_id%16s----yesIdentifier of the Single-exposure source extraction that is spatially associated with the SSO predicted position at the time of the WISE observation.

CAUTION: A spatial association between the predicted SSO position and the position of a WISE Single-exposure extraction does not necessarily mean that this is a WISE detection of the SSO. The Single-exposure Source Database contains a significant number of spurious detections of noise excursions, transient pixel events and image artifacts. Thus the spatial coincidence between the SSO position and WISE extraction may be a chance alignment with a spurious extraction or an inertial background astrophysical source. See IV.3.e.iv.1 for suggestions for identifying spurious associations.

This column is "null" if there is not a WISE Single-exposure extraction spatially associated with the predicted position of the SSO.

Source_id has the general form SSSSSxMMM-IIIIII, where

  • SSSSSx is the scan_id,
  • MMM is the frameset number within the scan, frame_num, and
  • IIIIII is the zero-filled, six-digit source number, src, within the frameset.
 
mconf%6.2f----yesSpatial association match confidence: 2-D chi-square parameter, max 99.99, -9.99 if no association  
n%1d----yesNumber of WISE Single-exposure extractions within association threshold (max 9), 0 if no association  
dra%6.1farcsecyesRA distance between associated WISE extraction and predicted SSO position (WISE - SSO).  
ddec%6.1farcsecyesDeclination distance between associated WISE extraction and predicted SSO position (WISE - SSO).  
w1mpro%7.3fmagyesSingle-exposure W1 profile-fit magnitude or magnitude upper limit for the WISE extraction spatially associated with the SSO. The column is null if there is no associated WISE extraction.  
w1sgmp%5.3fmagyesSingle-exposure W1 profile-fit photometric measurement uncertainty for the associated WISE extraction. This column is null if there is no associated WISE extraction, or the W1 profile-fit magnitude of an associated extraction is a 95% confidence upper limit.  
w2mpro%7.3fmagyesSingle-exposure W2 profile-fit magnitude or magnitude upper limit for the WISE extraction spatially associated with the SSO. The column is null if there is no associated WISE extraction.  
w2sgmp%5.3fmagyesSingle-exposure W1 profile-fit photometric measurement uncertainty for the associated WISE extraction. This column is null if there is no associated WISE extraction, or the W2 profile-fit magnitude of an associated extraction is a 95% confidence upper limit.  
w3mpro%7.3fmagyesSingle-exposure W3 profile-fit magnitude or magnitude upper limit for the WISE extraction spatially associated with the SSO. The column is null if there is no associated WISE extraction.  
w3sgmp%5.3f5.3fyesSingle-exposure W1 profile-fit photometric measurement uncertainty for the associated WISE extraction. This column is null if there is no associated WISE extraction, or the W3 profile-fit magnitude of an associated extraction is a 95% confidence upper limit.  
w4mpro%7.3fmagyesSingle-exposure W4 profile-fit magnitude or magnitude upper limit for the WISE extraction spatially associated with the SSO. The column is null if there is no associated WISE extraction.  
w4sgmp%5.3fmagyesSingle-exposure W1 profile-fit photometric measurement uncertainty for the associated WISE extraction. This column is null if there is no associated WISE extraction, or the W4 profile-fit magnitude of an associated extraction is a 95% confidence upper limit.  
x%19.16f----yes unit sphere (x,y,z) position x value  
y%19.16f----yesUnit sphere (x,y,z) position y value  
z%19.16f----yesUnit sphere (x,y,z) position z value  
spt_ind%9d----yesHTM spatial (x,y,z) index key  


Last Updated: 2011 April 26


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