Magdalena Ridge Derived Data Product Collection

Data Abstract
=============
We obtained images of the (65803) Didymos system and supporting calibration 
images with the MRO2K CCD on the MRO 2.4m Telescope at the Magdalena Ridge 
Observatory (MRO). 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, as well as 
PNGs of reference stars used in the photometric reduction.

Data Set Overview
=================
The photometry of Didymos and comparison stars is performed using the IRAF 
phot package [1]. The instrumental magnitude of Didymos is measured in 
each field. In addition, an ensemble of stars in each comparison field, 
as identified by the PNG image file, are also measured. The comparison 
star field is observed multiple times in a night observing session and 
archived as raw image data. Note that after initial analysis, some stars 
are assessed as inappropriate to be used as comparison stars based on 
inherent variability, etc., and are not used in the final analysis.

A temporally interpolated average magnitude of the comparison star fields 
is subtracted from each Didymos instrumental magnitude resulting in a 
differential magnitude. If it is not feasible to perform further magnitude 
calibrations, the resulting magnitude is reported as "relative". Ideally, 
additional observations of Landolt standard stars [2, 3] are obtained to 
derive Johnson-Cousins R- and V-band magnitudes of the comparison stars 
allowing the reporting of standard R-band magnitudes of Didymos. In this 
case, the magnitude is reported as "absolute".

The photometry summary tables are named according to the following convention: 

mro_<yymmdd>_didymos_photometry.tab

where:
mro refers to the MRO 2.4-meter Telescope

<yymmdd> is the year, month, day of the observing session in UTC

Ex: mro_220813_didymos_photometry.tab

For each comparison field image there is an associated PNG image of 
comparison stars used for the photometric solution. A reference to the 
comparison star PNG is included in the XML label for the photometry table.
Comparison star PNGs are named according to the following convention:

comps_<yymmdd>.png

where: 
<yymmdd> is the year, month, day of the observing session in UT

Photometry data are reported in ASCII files with two sections – an 
informational header and the photometry data itself. Header lines are 
denoted with an ASCII '#' with entries specified as follows.

Header:
Observers - Observer names (string)
Facility - Facility name (string)
Instrument - Instrument name (string)
UTDate - UT Date (string)
Object - Object name (string)
CompField - Image file name identifying comparison stars measured (string)
CompStarsUsed - Comparison stars used in final computation (numeric list)
Filter - Filter used (V, R, g, r, etc)
Magband - Magnitude band of reported data (V, R, g, r, etc)
CIBand - Color index used in calibration (B-V, V-R, g-r, etc or None)
CITarget - Color index used for target (Float; 0 if CIBand = None)
LTCorrection - Light time correction (True/False)
ReducedMag - Magnitude corrected for distance (True/False)
MagType - Magnitude type reported (Absolute or Relative)
ExpJD - Exposure time reported (Start or Mid)

Records:
julian date - Julian date of the exposure midtime (string)
mag - Target magnitude, unitless (float)
sig - 1-sigma error on the apparent magnitude, unitless (float)

References
=================
[1] Tody, D., IRAF in the Nineties, in Astronomical Data Analysis Software 
    and Systems II, A.S.P. Conference Ser., Vol 52, eds. R.J. Hanisch, 
    R.J.V. Brissenden, & J. Barnes, 173, 1993.
[2] Landolt, A.U. 1992, Astronomical Journal vol. 104, p. 340
[3] Landolt, A.U. 2009, Astronomical Journal vol. 137, p. 4186.