Publisher source
The NOIRLab Source Catalog (NSC) is built from public imaging in NOIRLab’s Astro Data Archive. NSC DR2 includes imaging primarily from CTIO-4m/DECam, KPNO-4m/Mosaic3, and Bok-2.3m/90Prime.
The publisher describes DR2 as covering about 35,273 square degrees with 412,116 exposures, 3.9 billion unique objects, and 67.8 billion individual measurements. Source extraction, calibration, combination, quality assurance, and reported photometric and astrometric performance are described in the NSC Data Lab documentation and NSC DR2 paper.
What AIMS selects
AIMS queries NSC DR2 through NOIRLab Data Lab services and joins:
nsc_dr2.objectfor object-level motion and detection-count fields;nsc_dr2.measfor individual source measurements;nsc_dr2.exposurefor timing, duration, filter, and instrument metadata.
AIMS retains measurements satisfying at least one of these conditions:
- total catalog proper motion is at least 0.3 arcsec/day after conversion from milliarcseconds per year;
ndet == 1, meaning the catalog object has only one detection and no useful motion estimate;deltamjd <= 1day, so a short observing interval does not cause a potentially useful source to be rejected solely by its fitted proper motion.
This is a moving-source search selection, not a solar-system classification. It excludes most static sources while retaining some high-proper-motion stars and other contaminants.
Coverage and observatories
AIMS treats NSC DR2 as a frozen historical source covering 2012-09-23 through 2019-11-16, inclusive.
| NSC instrument | AIMS/MPC observatory code |
|---|---|
c4d | W84 |
ksb | V00 |
k4m | 695 |
Rows from an unmapped instrument cannot be published as normalized AIMS observations until an observatory mapping is defined.
Normalization into AIMS
| AIMS field | NSC source or derivation |
|---|---|
observation_id | meas.measid converted to string. |
exposure_id | meas.exposure. |
dataset_id | Constant nsc. |
observatory_code | Derived from NSC instrument using the mapping above. |
| Observation time | Exposure midpoint, computed as exposure.mjd + exposure.exptime / 2 / 86400. |
ra_deg, dec_deg | meas.ra, meas.dec. |
ra_sigma_deg, dec_sigma_deg | meas.raerr, meas.decerr converted from arcseconds to degrees. |
mag, mag_sigma | meas.mag_auto, meas.magerr_auto. |
filter | meas.filter. |
healpixel | Derived from RA/Dec at nside=128 NESTED. |
Published AIMS products
In the AIMS BigQuery dataset, normalized NSC rows are written to aims_nsc, copied into aims_detections_hot, and exposed through the aims_detections_unified view with dataset_id = nsc.
The same normalized rows are exported to Google Cloud Storage through the daily aims_detections_parquet product. AIMS also derives aims_frames_unified BigQuery rows and aims_frames_parquet search indexes grouped by NSC exposure and HEALPix. Complete detection/frame pairs are listed in aims_unified_parquet_catalog/catalog.json for consumers such as Precovery. The frame rows are derived search indexes, not copies of all NSC exposure metadata.
Scientific validity and limitations
- Source positions, photometry, filters, and reported uncertainties retain NSC meaning apart from documented unit and time conversions; AIMS does not cross-calibrate them onto a shared survey system.
- The selection is scientifically useful for archival moving-source search, but it is neither complete nor pure. It depends on NSC object association, fitted motion, detection count, and observing interval.
- NSC is object-centric while AIMS is detection-centric: AIMS publishes individual
measrows but uses object-level properties to decide which rows enter the catalog. - Proper motion is a selection variable, not proof that a retained detection is a solar-system object.
- AIMS maps
raerranddecerrinto east/north uncertainty fields but does not preserve an NSC cross-axis correlation or full covariance. Downstream use is therefore limited to a diagonal approximation. - AIMS treats this source as frozen DR2. A later NSC release would require separate selection, normalization, and provenance review.