DAD (DECam Asteroid Database)
DECam Asteroid Database (DAD)
Description
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".
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 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 (equatorial 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 formatted record for the observation. The set of records for a particular tracklet is what was submitted as a detection to the MPC.
Data Releases
Second Data Release (DAD DR2)
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. The database and list of tables can be browsed using Data Lab's table browser.
| DAD DR2 Table Information | |||
|---|---|---|---|
| Table Name | Row Count | Total Exposures | Total Tracklets |
| movds | 5,335 | - | - |
| movexp | 23,622 | 20,001 | - |
| movgrp | 662,154 | - | 662,154 |
| movobs | 2,974,302 | - | - |
| movmpc | 2,974,297 | - | - |
| DAD DR2 Basic Statistics | ||
|---|---|---|
| P.I. | Pointings | Tracklets |
| Allen | 3,126 | 608,829 |
| Sheppard | 924 | 46,833 |
| Forster | 220 | 3,353 |
| Fuentes | 280 | 1,267 |
| Dell_Antonio | 28 | 433 |
| Munoz | 84 | 270 |
| French | 138 | 185 |
| Carlin | 37 | 140 |
| Vivas | 39 | 120 |
| Rich | 12 | 108 |
| Sullivan | 35 | 73 |
| Saha | 46 | 62 |
| Trilling | 47 | 59 |
| Yip | 12 | 46 |
| Frieman | 38 | 39 |
| Geha | 18 | 39 |
| Dai | 23 | 35 |
| Rest | 24 | 35 |
| Bonaca | 13 | 32 |
| Mamajek | 44 | 30 |
| Heinze | 3 | 27 |
| Crnojevic | 15 | 22 |
| Konstantopoulos | 4 | 21 |
| Hargis | 3 | 18 |
| Mackey | 20 | 16 |
| Taylor | 21 | 16 |
| McMonigal | 16 | 10 |
| Calamida | 4 | 7 |
| Walker | 5 | 7 |
| Sheen | 1 | 6 |
| Briceno | 12 | 3 |
| Curtin | 2 | 2 |
| McCleary | 7 | 2 |
| Penny | 2 | 2 |
| Rusu | 1 | 2 |
| Silva | 1 | 2 |
| Geisler | 1 | 1 |
| Schlegel | 1 | 1 |
| Yan | 3 | 1 |
First Data Release (DAD DR1)
The first data release was only for the DECam NEO Survey (P.I. Allen).
| DAD DR1 Table Information | |||
|---|---|---|---|
| Table Name | Row Count | Total Exposures | Total Tracklets |
| movds | 4,073 | - | - |
| movexp | 18,976 | 17,672 | - |
| movgrp | 660,539 | - | 660,539 |
| movobs | 2,968,831 | - | - |
| movmpc | 2,968,831 | - | - |
| DAD DR1 Basic Statistics | ||
|---|---|---|
| P.I. | Pointings | Tracklets |
| Allen | 3,126 | 608,829 |
| Sheppard | 366 | 46,345 |
| Forster | 220 | 3,730 |
| Fuentes | 132 | 1,088 |
| Rich | 9 | 89 |
| Sullivan | 33 | 72 |
| Saha | 24 | 53 |
| Geha | 9 | 39 |
| Frieman | 32 | 37 |
| Dai | 23 | 35 |
| Heinze | 3 | 27 |
| Bonaca | 3 | 25 |
| Rest | 15 | 24 |
| Konstantopoulos | 4 | 21 |
| Walker | 4 | 21 |
| Hargis | 3 | 18 |
| Taylor | 21 | 16 |
| Mackey | 9 | 15 |
| Munoz | 10 | 14 |
| Crnojevic | 9 | 13 |
| McMonigal | 6 | 10 |
| Sheen | 1 | 6 |
| Calamida | 2 | 4 |
| McCleary | 2 | 3 |
| Rusu | 1 | 2 |
| Geisler | 1 | 1 |
| Mamajek | 1 | 1 |
| Vivas | 1 | 1 |
Table Descriptions
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 Access
The DAD data are accessible by a variety of means:
Data Lab Table Access Protocol (TAP) service
TAP provides a convenient access layer to the DAD catalog database. TAP-aware clients (such as TOPCAT) can point to https://datalab.noirlab.edu/tap, select the dad_dr2 database, and see the database tables and descriptions. You can also view the DAD tables and descriptions in the Data Lab table browser.
Data Lab Query Client
The Query Client is available as part of the Data Lab software distribution. The Query Client provides a Python API to Data Lab database services. These services include anonymous and authenticated access through synchronous or asynchronous queries of the catalog made directly to the database. Additional Data Lab services for registered users include personal database storage and storage through the Data Lab VOSpace.
The Query Client can be called from a Jupyter Notebook on the Data Lab Notebook server. Example notebooks are provided to users upon creation of their user account (register here), and are also available to browse on GitHub at https://github.com/astro-datalab/notebooks-latest.
