The Solar System Processing (SSP) Pipeline#

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Solar System Prompt Processing#

The goal of the nightly Solar System Processing pipeline is to link (identify) previously unknown SSObjects, given an additional night of observing, and report the discoveries to the Minor Planet Center (MPC), as well as to compute physical (e.g., absolute magnitudes) and other auxiliary properties (e.g., predicted apparent magnitudes and coordinates in various coordinate systems) for known Solar System objects and their LSST observations. The majority of the pipeline’s processing occurs in daytime, after a night of observing. The pipeline will deliver Daily Data Products for Solar System objects in the form of four catalogs: SSObject, SSSource, DIASource, and MPCORB, which are described in the DP0.3 Data Products documentation and the Data Products Definition Document (DPDD). The Solar System Processing pipeline is illustrated in the infographic provided above. For more information on the moving object tracklet linking and orbit fitting algorithm, see the HelioLinC3D Tracklet Linking and Orbit Fitting software package page.

The Solar System Processing pipeline steps#

During operations, the pipeline will consist of the following steps that will repeat every 24 hours:

During nightly observing:

  1. Known Solar System objects are associated with difference image detections in real-time. Alerts are produced within 60 seconds for all signal-to-noise ratio (SNR)>=5 DIASources. The Alert Production pipeline attempts association of DIASources with known Solar System objects in real-time, and if a match is found then the alert includes the corresponding SSObject catalog.

During the day following nightly observing:

  1. All DIASources detected on the previous night that have not been matched at a high confidence level (SNR>=5) to a known Object, DIAObject, SSObject, or an artifact, are analyzed by the HelioLinC3D moving object linking algorithm for potential pairs that form tracklets (consisting of detections in three pairs of images for a given visit within 15 days) that are consistent with being on the same Keplerian orbit around the Sun. For more information on this algorithm, see the HelioLinC3D Tracklet Linking and Orbit Fitting software package page.

  2. Measurements of known objects and new discoveries are submitted to the Minor Planet Center (MPC) using the standard data-exchange protocols (e.g., the ADES format). The measurements of all DIASources detected on the previous night that have been matched at a high level of confidence (SNR>=5) to a known SSObject are also submitted to the MPC.

During the day before the coming night’s observing:

  1. The most up-to-date MPCORB catalog is downloaded from the Minor Planet Center (MPC) and ingested into the Prompt Products database to obtain all previously submitted LSST discoveries and detections as well as discoveries and detections by other contemporaneous programs made during the past 24 hours.

  2. The Daily Data Product catalogs are updated to include the new Solar System object discoveries included in the ingested MPCORB catalog. In particular, the SSObject catalog is updated to include the new discoveries from the ingested MPCORB catalog, and the SSSource and DIASource catalogs are updated to point to the relevant SSObject records for the new discoveries. In addition, the physical properties of all known SSObjects (e.g., absolute magnitudes, predicted apparent magnitudes, extendedness estimates, and light curve characteristics), as defined by the orbit catalog, are recomputed. Updated data are entered into the relevant tables.

  3. The Solar System Daily Data Products (MPCORB, SSObject, DIASource, & SSSource tables) are released.

  4. Precovery linking is attempted for all SSObjects whose orbits were updated in the above process (or are new). Where successful, newly discovered observations are queued up for submission to the Minor Planet Center.

Solar System Data Release Processing#

In addition to the prompt processing that will be performed on a daily basis, re-processing of the data will be performed annually to produce the Data Release Data Products; an exception to the annual re-processing timeline will be the first two Data Releases that will be created six months apart. As described above, the Daily (Prompt) Data Products for Solar System objects will include single visit images, difference images, catalogs of sources detected in difference images (DIASources) and detected objects that are associated with Solar System objects (SSObjects), which will include all data collected by the survey to date and will be entered into the Prompt Products database and made available in near real time. One expection to the use of all survey data to date for the near real time data releases, however, is the Alert Production pipeline that limits the DIASource history for all variability parameters within the alert packets to a 12-month period.

The roughly annual Data Release Data Products for Solar System objects will include high-fidelity re-processing of all catalogs derived from re-reductions of all survey data using improved calibrations and a single, well-characterized, software release. In addition, the Data Release Data Products will include a LSST Catalog of Solar System Objects that will be suitable for population studies of objects detected by LSST with orbits estimated using only LSST data; this catalog will not rely on association of known objects using MPC orbit predictions. In contrast to the Prompt Products database, which is updated continuously during observing, the Data Release database is static and will not change after release. In general, the Data Release Data Products are best for purposes such as large-scale Solar System population studies and model debiasing, while the Daily (Prompt) Data Products are most useful for efforts such as follow-up and characterization of Solar System objects as they are detected by the survey.

Acronym definitions:

  • MPC = Minor Planet Center

  • SS = Solar System

  • DIA = difference image analysis

  • SNR = signal-to-noise ratio

More information#