Lowell Derived Data Product Collection

Data Abstract
=============
We obtained images of the (65803) Didymos system and supporting calibration
images with the Lowell Discovery Telescope (LDT) through a VR filter. These 
images were taken in order to determine the orbit period of Dimorphos, the 
satellite of Didymos. This collection consists of the photometry summary tables,
which are a PDS4 derived product.


Data Set Overview
=================

The photometry of Didymos is measured using the open source PHOTOMETRYPIPELINE 
package (Momert, M., 2017. PHOTOMETRYPIPELINE: An automated pipeline for 
calibrated photometry. Astronomy and Computing, 18, pp.47–53). This pipeline 
astrometrically registers images based on the measured position of Gaia DR2 
stars in the field, photometrically calibrates the zero point of the images 
based on the measured flux of field stars that have known catalog magnitudes 
(typically from the PanSTARRS catalog), and then using these astrometric and 
photometric solutions derives a calibrated magnitude for Didymos. The PNG 
files and photometry tables included in this dataset are outputs of this 
pipeline. The pipeline is built upon the tools SExtractor and SCAMP (E. Bertin 
and S. Arnouts. SExtractor: Software for source extraction. A&AS, 117:393–404, 
June 1996. doi:10.1051/aas:1996164). 

The photometry summary table is named according to the following convention: 
ldt_<YYYYMMDD>_didymos_photometry.dat
where:
ldt – refers to the Lowell Discovery Telescope
<YYYYMMDD> is the year, month, day of the observing session in UTC.
Ex. ldt_20201215_didymos_photometry.dat

Photometry data are stored as a PDS4 ASCII fixed-width table according to the 
following format. 

file: file name of the calibrated image where data were measured
julian date: Julian date of the exposure midtime
mag: Calibrated PanSTARRS r-band apparent magnitude of Didymos
sig: 1-sigma error on the apparent magnitude 
ZP: Calibrated zero point magnitude in PanSTARRS r-band
ZP_sig: 1-sigma error on the zero point magnitude
inst_mag:  Instrumental magnitude of Didymos 
in_sig: 1-sigma error on the instrumental magnitude
SExtractor_flag: Flags associated with the Source Extractor photometry 
measurements, see source_extractor_flags .txt in the documents folder for this 
archive for more detailed description.
aprad: Radius in pixels of the aperture used for the photometry measurement


References
=================
Momert, M., 2017. PHOTOMETRYPIPELINE: An automated pipeline for calibrated photometry. Astronomy and Computing, 18, pp.47–53. doi:10.48550/arXiv.1702.00834
E. Bertin; S. Arnouts. SExtractor: Software for source extraction. Astronomy and Astrophysics Supplement, 117:393–404, June 1996. doi:10.1051/aas:1996164