Astro Data Lab

DECam Asteroid Database (DAD)

The DECam Asteroid Database contains a list of candidate asteroids (moving objects) from archival Dark Energy Camera (DECam) images.

The DECam NEO Survey (P.I. Lori Allen) used DECam to measure the size distribution of Near-Earth Objects (NEOs) from 1 km to 10 m. The survey has measured 235 unique NEOs, implying the existence of 4 million NEOs larger than 10 m (Allen 2016). For more information on the NEO survey, see the presentation from the 2015 "Science with DECam meeting".

Database Tables

The fundamental organization and linkage between tables is the dataset. A dataset is a pointing on the sky from which multiple exposures were used to search for asteroid tracklets. This field is common to all tables and is a primary key for joining.
 The database is organized around tracklets. A tracklet is some number of measurements from individual exposures that are identified as moving in the field and are celestial sources (i.e. not junk). A tracklet has an identification (movid) which is uniquely derived from the exposure and detection number (groupid). When known, tracklets will have IDs from the Minor Planet Center (mpcid) which may then link multiple tracklets from different nights.
 The first data release was only for the DECam NEO Survey (P.I. Allen). The second release supersedes the first release, and added tracklets derived from all public DECam data that are suitable for the Moving Object Detection System (MODS) algorithm (Valdes et al. 2017). This version is still an early release with some database records having incomplete fields. Both releases of objects and measurements are available through Data Lab. The database and list of tables can be browsed using Data Lab's table browser.
 The following is a brief overview of the logical organization of the entities that make up the database tables. A dataset consists of a number of exposures (> 2). An exposure is characterized by an exposure ID (a filename) and parameters of the exposure such as time and length of the exposure. A group is a set of observations of an object in some or all of the exposures identified as forming a moving object tracklet. A tracklet is characterized by an ID and parameters such as the rate of motion and magnitude. An observation is an individual detection of a moving object in a CCD of an exposure. It is characterized by positions in three coordinate systems (equitorial on the sky, CCD image pixel, and cutout image pixel). A filename for a cutout image is also given. Related is a table giving the MPC formated record for the observation. The set of records for a particular tracklet is what was submitted as a detection to the MPC.

Table MOVDS

This table describes the characteristics of the datasets (pointings). The time and position fields are for the start of the first observation exposure in the set. Position fields are for the center of the field. See the MOVDS table for column names, descriptions, and datatypes.

Table MOVEXP

The exposure table provides details of each exposure. The expname is a way to link to the image data in the Astro Data Archive. The expid is the sequential count of the exposures in a dataset. The separation time is a relative time for the middle of each exposure with an origin at the start of the first exposure. See the MOVEXP table for column names, descriptions, and datatypes.

Table MOVGRP

This is the main tracklet table. It provides information about each connected set of observations corresponding to a moving object. See the MOVGRP table for column names, descriptions, and datatypes.

Tables MOVOBS and MOVMPC

These tables provide information for each separate detection of a moving object. They provide links to associated files (see below) and to what was reported to the MPC. (The MPC records are sometimes the only way to find information from the MPC website). Note that the MPC records are basically an encoding of the information in the exposure and observation tables in a specific format for reporting the time, position, and estimated magnitude for an observation. See the MOVOBS table for column names, descriptions, and datatypes. See the MOVMPC table for column names, descriptions, and datatypes.

Data Products

At this time, Astro Data Lab only provides the DAD DR1 and DAD DR2 catalog tables.

Survey Statistics