The first release of SDSSMOC included all data obtained up to Dec 15, 2001. The catalog includes data for 58,117 moving objects from 87 observing runs that roughly cover the area included in the SDSS Data Release 1 (January 1, 2003).
The second release of SDSSMOC includes 134,335 moving objects from 194 observing runs obtained up to March 11, 2003. Objects from the first release are included in the second release because the photometric pipeline and flatfield vectors changed a bit between the two releases.
The third release of SDSSMOC includes 204,305 moving objects from 301 observing runs obtained up to June 2004. Objects from the first two releases are included in the third release.
This fourth release of SDSSMOC includes 471,569 moving objects from 519 observing runs obtained up to March 2007. This is a cumulative release and includes objects from the first three releases. The sample completeness and contamination in the fourth release are expected to be unchanged since the third release, and are estimated to be ~95% and ~6%, respectively (estimated with an accuracy of 1-2%). These values are somewhat different than ~90% and ~3%, respectively, that were reported by Ivezic et al. (2001): the sample completeness slightly increased, with a corresponding increase of sample contamination.
Unlike the first three releases, this fourth release includes SDSS-II data obtained in non-photometric conditions. For this reason, photometric accuracy may be substandard for some equatorial, so-called supernovae, runs (defined by |Dec| < 1.26 deg. and negative galactic latitude). Also, some of SDSS-II runs cross the Galactic plane. Due to high source density and the resulting confusion, both photometry and astrometry may be substandard for regions within about 15 deg. from the Galactic plane. These problems are especially important when looking for objects with peculiar colors. Please take extra care in your data analysis! For an example of the use of the fourth release catalog, please see Parker et al. (2008, astro-ph/0807.3762).
SDSSMOC is updated about once for every major SDSS Data Release. We plan one more final release, after the above calibration and other issues are sorted out (probably during Spring 2009).
The catalogs include various identification parameters, SDSS astrometric measurements (position and velocity, with errors), SDSS photometric measurements (five SDSS magnitudes and their errors), and orbital information for previously cataloged asteroids.
WHERE (
(objFlags & (OBJECT_SATUR | OBJECT_BRIGHT | OBJECT_BLENDED)) == 0
&&
(objFlags & OBJECT_DEBLENDED_AS_MOVING) > 0
&&
(objc_type == 6)
&&
(psfCounts[2] > 14.5) && (psfCounts[2] < 21.5)
&&
(rowv*rowv + colv*colv > 0.0025)
&&
(rowv*rowv + colv*colv < 0.25)
)
The first line excludes all saturated and "bright" objects (the latter are always
duplicates of physical objects produced by processing software), and the second line
requires that the object was recognized as a moving object by SDSS photometric
pipeline (Lupton et al. 2005, in prep; see also a paper about SDSS moving objects by
Ivezic et al. 2001, hereafter Paper I). The third and fourth lines require that
the object is unresolved and brighter than r=21.5, and the last two conditions require
that the magnitude of the object's velocity vector is larger than 0.05 deg/day and
smaller than 0.5 deg/day. Note that some of these entries are multiple observations
of the same objects (see Section 3.3. in Paper I).
The completeness (number of moving objects detected by the software that are included in the catalog, divided by the total number of moving objects recorded in the images, for details see Juric et al. 2001, hereafter Paper II) of the third release catalog is about 95%, and its contamination rate is about 6% (the number of entries that are not moving objects, but rather instrumental artifacts, for details see Paper I). For example, in the third release catalog, about 10,000 observed moving objects were missed by the processing software, and about 12,000 catalog entries are instrumental and software artifacts.
Using these supplemental orbital data, the SDSS colors can be used to produce informative plots of asteroid distribution in orbital parameter space; e.g. see a "colorful" plot of asteroid distribution in the proper inclination vs. semi-major axis plane. Details about this plot can be found in Ivezic et al. 2002, Paper III (pdf).
The catalog is distributed as uncompressed ASCII file (291 MB), and a gzip compressed file (64 MB), with one record (line) per object observation (see below for file links). Each record contains:
| Field | Columns [start, end) |
Field | Description | ||
|---|---|---|---|---|---|
| -- SDSS identification -- | |||||
| 1 | 1 - 7 | moID | Unique SDSS moving-object ID | ||
| 2 | 8 - 13 | Run | SDSS object IDs, for details see SDSS EDR paper | ||
| 3 | 14 - 15 | Col | |||
| 4 | 16 - 20 | Field | |||
| 5 | 21 - 26 | Object | |||
| 6 | 27 - 35 | rowc | Pixel row | ||
| 7 | 36 - 44 | colc | Pixel col | ||
| -- Astrometry -- | |||||
| 8 | 47 - 59 | Time (MJD) | Modified Julian Day for the mean observation time | ||
| 9 | 60 - 70 | R.A. | J2000 right ascension of the object at the time of the (r band) SDSS observation | ||
| 10 | 71 - 81 | Dec | J2000 declination of the object at the time of the (r band) SDSS observation | ||
| 11 | 82 - 92 | Lambda | Ecliptic longitude at the time of observation | ||
| 12 | 93 - 103 | Beta | Ecliptic latitude at the time of observation | ||
| 13 | 104 - 115 | Phi | Distance from the opposition at the time of observation | ||
| 14 | 117 - 124 | vMu | The velocity component parallel to the SDSS scanning direction, and its error (deg/day) | ||
| 15 | 125 - 131 | vMu Error | |||
| 16 | 132 - 139 | vNu | The velocity component perpendicular to the SDSS scanning direction, and its error (deg/day) | ||
| 17 | 140 - 146 | vNu Error | |||
| 18 | 147 - 154 |
vLambda |
The velocity component parallel to the Ecliptic
(deg/day) |
||
| 19 | 155 - 162 |
vBeta |
The velocity component perpendicular to the Ecliptic
(deg/day) |
||
| -- Photometry -- | |||||
| 20 | 164 - 169 | u | SDSS u'g'r'i'z' psf magnitudes and corresponding errors | ||
| 21 | 170 - 174 | uErr | |||
| 22 | 175 - 180 | g | |||
| 23 | 181 - 185 | gErr | |||
| 24 | 186 - 191 | r | |||
| 25 | 192 - 196 | rErr | |||
| 26 | 197 - 202 | i | |||
| 27 | 203 - 207 | iErr | |||
| 28 | 208 - 213 | z | |||
| 29 | 214 - 218 | zErr | |||
| 30 | 219 - 224 | a | a* color = 0.89 (g - r) + 0.45 (r - i) - 0.57 (see Paper I) | ||
| 31 | 225 - 229 | aErr | |||
| 32 | 231 - 236 | V | Johnson-V band magnitude, synthetized from SDSS magnitudes | ||
| 33 | 237 - 242 | B | Johnson-B band magnitude, synthetized from SDSS magnitudes | ||
| -- Identification -- | |||||
| 34 | 243 - 244 | Identification flag | Has this moving object been linked to a known asteroid (0/1)? See Paper II. | ||
| 35 | 245 - 252 | Numeration | Numeration of the asteroid. If the asteroid is not numbered, or this moving object has not yet been linked to a known asteroid, it's 0. | ||
| 36 | 253 - 273 | Designation | Asteroid designation or name. If this moving object has not yet been linked to a known asteroid, it's '-' | ||
| 37 | 274 - 276 |
Detection Counter |
Detection counter of this object in SDSS data |
||
| 38 | 277 - 279 | Total Detection Count | Total number of SDSS observations of this asteroid | ||
| 39 | 280 - 288 | Flags | Flags that encode SDSSMOC processing information (internal) |
||
| -- Matching information -- | |||||
| 40 | 290 - 300 | Computed R.A. | Predicted position and magnitude at the time of SDSS observation for an associated known object computed using ASTORB data See a note about an error in the first three releases | ||
| 41 | 301 - 311 | Computed Dec | |||
| 42 | 312 - 317 | Computed App. Mag. | |||
| 43 | 319 - 326 | R | Heliocentric distance at the time of observation | ||
| 44 | 327 - 334 | Geocentric | Geocentric distance at the time of observation | ||
| 45 | 335 - 340 | Phase | Phase angle at the time of observation | ||
| -- Osculating elements -- | |||||
| 46 | 342 - 352 | Catalog ID | Identification of the catalog from which the osculating elements and (H, G) values were extracted | ||
| 47 | 363 - 368 | H | Absolute magnitude and slope parameter | ||
| 48 | 369 - 373 | G | |||
| 49 | 374 - 379 | Arc | Arc of observations used to derive the elements | ||
| 50 | 380 - 393 | Epoch | Osculating elements | ||
| 51 | 394 - 406 | a | |||
| 52 | 407 - 417 | e | |||
| 53 | 418 - 428 | i | |||
| 54 | 429 - 439 | Lon. of asc. node | |||
| 55 | 440 - 450 | Arg. of perihelion | |||
| 56 | 451 - 461 | M | |||
| -- Proper elements -- | |||||
| 57 | 463 - 483 | Proper elements catalog ID | Identification of the catalog from which the proper elements were extracted | ||
| 58 | 484 - 496 | a' | Proper elements | ||
| 59 | 497 - 507 | e' | |||
| 60 | 508 - 518 | sin(i') | 61-124 | 519 - 646 | binary processing flags | Only since the 3rd release!! |
Unique SDSS moving-object ID (e.g. s0456d) is a coded representation (hash table) of an observation based on SDSS run number and equatorial position on a 1x1 arcsec grid (the limit of 6 digits is stipulated by the Minor Planet Center observation report form). Note that this ID describes SDSS observations, and not physical objects. Thus, the same object can be associated with multiple IDs; one for each SDSS observation.
MJD (TAI) of the mean time during the exposure. If using the first release of SDSS MOC, this record has a different definition.
Johnson V band magnitude is computed from SDSS photometry using
V = r + 0.44*(g-r) - 0.02
Johnson B band magnitude is computed from SDSS photometry using
B = V + 1.04*(g-r) + 0.19
The accuracy of these transformations is better than 0.05 mag (Fukugita et al.
1996, Astronomical Journal, 111, 1748). Recently, an improved set of photometric
transformations was made available at the
SDSS data release site
A minor error in the computed positions was present in the first three releases. SDSS quotes time in TAI, while we didn't realize that the time in the ASTORB catalog is quoted in TDT (the difference is TDT = TAI + 32.184 sec). This affected the computed positions (entries 40 and 41) of matched objects in the first three releases of the catalog, though not by much (typically by 0.3 arcsec).
Identification for ASTORB file A string of the form ASTORB_YYYYMMDD, where YYYYMMDD is the release date for ASTORB file used in matching.
Identification for file with proper orbital elements A string of the form ASTDYS_?_YYYYMMDD, where YYYYMMDD is the issue date of file used in matching, and ? can be either N (numbered objects) or U (unnumbered objects).
Processing flags set by photometric pipeline. These 64 flags are listed in binary format (0/1) and convey whether an object's detection and subsequent measurements are reliable. For details see Understanding the image processing flags document.
These flags are particularly important when selecting subsamples with peculiar colors, or other measured properties. For example, in a subsample of objects with (g-r) > 1, the MAYBE_CR flag is five times as likely to be set than in the full sample. In order to facilitate such analysis, we also list individual flag statistics for the full sample, and copy verbatim the most relevant portion of the flags document.
Additional Notes:
In all string field values blanks have been replaced with underscores. For example, the designation "1998 RH41" is encoded as "1998_RH41", This allows the record to be read as a series of blank-delimited fields.
All magnitudes that were not properly measured were replaced by 99.99, and all errors that were not properly measured were replaced by 9.99.
In the first version of SDSS MOC, MJD corresponds to the time when row 0 of the r frame was read. To get true mean observation time for an object, add (3.0471e-07 * rowc) days to mjd, where rowc is listed in the catalog (field 6) for each object.
To this program, save it first in a file called sademo.c, then compile it as
cc sademo.c -o sademo
and run it as
./sademo filename
where "filename" stands for the catalog file name. The output for
file ADR1.dat should look like
> ./sademo ADR1.dat Parsed file ADR1.dat [58118 lines] Total moving objects : 58117 Blue : 22084 Red : 35974 Color unknown : 59 Identified : 12602
Funding for the creation and distribution of the SDSS Archive has been provided by
the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics
and Space Administration, the National Science Foundation, the U.S. Department of Energy,
the Japanese Monbukagakusho, and the Max Planck Society. The SDSS Web site is
http://www.sdss.org/.
The SDSS is managed by the Astrophysical Research Consortium (ARC) for the Participating
Institutions. The Participating Institutions are The University of Chicago, Fermilab, the
Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University,
the Korean Scientist Group, Los Alamos National Laboratory, the Max-Planck-Institute for
Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University,
University of Pittsburgh, University of Portsmouth, Princeton University, the United States
Naval Observatory, and the University of Washington.
If you write a paper based on this catalog, please let us know and we will add it to the list of other SDSS-based asteroid publications. This way we will minimize the chance for repeating someone else's work, and will also have a convenient way to access all related papers. The current list is available here.
Thank you very much,
Zeljko Ivezic (1) Mario Juric (2) Robert Lupton (2) Tom Quinn (1) and the SDSS Collaboration (1) The University of Washington (2) Princeton University
Each data file has identical format, as described above (apart from the last 64 columns with binary flags, that exist only since the 3rd release, and a longer entry number 35 since the 4th release). As the new data become available, we will update the list below with additional catalogs.
Due to a minor formatting bug, the above fourth release files were updated on Nov 2, 2009. The old files are still available as unzipped and gzipped versions.
Unlike the first three releases, this fourth release includes SDSS-II data obtained in non-photometric conditions. For this reason, photometric accuracy may be substandard for some equatorial, so-called supernovae, runs (defined by |Dec| < 1.26 deg. and negative galactic latitude). Also, some of SDSS-II runs cross the Galactic plane. Due to high source density and the resulting confusion, both photometry and astrometry may be substandard for regions within about 15 deg. from the Galactic plane. These problems are especially important when looking for objects with peculiar colors. Please take extra care in your data analysis!
If you need more information, please let us know!
The fourth release is a cumulative release, and it supersedes
Run Lists for Released Catalogs
The files linked below provide basic information about each SDSS observing run used in producing SDSSMOC files. The file names correspond to SDSSMOC file names, with suffix ".dat" replaced by ".runList". Each file has 8 columns that list the run number, run, the starting equatorial position of the (0,0) pixel in camera column 1 (in degrees, RA and Dec), the modified Julian Day for the beginning and the end of the run (MJDstart and MJDend), its node and inclination (in degrees, node and inclination) relative to the equatorial coordinate system (see SDSS EDR paper), and the starting great circle coordinates (so-called mu and nu coordinates, mu is measured along the scan, and nu perpendicularly to the scan) for the (0,0) pixel in camera column 1 (in degrees, mu0 and nu0). The last two quantities are redundant, and can be reproduced using RA, Dec, node, and inclination; they are added for testing coordinate transformations; for convenience, we provide relevant C functions used by SDSS software pipelines.
The sky region covered by a run can be obtained using the above information for the (0,0) pixel in camera column 1, and the layout of the SDSS imaging camera. The nu range spanned by the six camera columns, relative to the (0,0) pixel in camera column 1, is (in degrees):
column nuMin nuMax 1: 0.000000 0.225269 2: 0.419741 0.645077 3: 0.839260 1.064554 4: 1.258912 1.484212 5: 1.678480 1.903806 6: 2.098364 2.323656
ADR1.runList: the run list for ADR1.dat
ADR2.runList: the run list for ADR2.dat
ADR3.runList: the run list for ADR3.dat
ADR4.runList: the run list for ADR4.dat
Please send us your comments or suggestions.