Las Cumbres Observatory FLI Derived Data Product Collection

Data Abstract
=============

We obtained images of the NEO (65803) Didymos binary asteroid and the resulting
plume of debris from the impact of the DART spacecraft with Dimorphos, along
with supporting calibration data, from the three 1 meter Las Cumbres 
Observatory (LCOGT) telescopes at the site in South Africa. These images were
obtained to supplement the NASA's Double Asteroid Redirection Test (DART)
mission. The DART mission was a planetary defense mission designed to
test and measure the deflection caused by a kinetic impactor (the
spacecraft) on the orbit of Dimorphos asteroid around its primary,
Didymos. These ground-based observations from the date of impact (2022-09-26 UTC)
were used to obtain three color measurements and light curves of Didymos and
the resulting debris plume after the impact of the DART spacecraft. 
This collection consists of the Las Cumbres Observatory multi-aperture
photometry summary tables, which are a PDS4 derived product.

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

The photometry of Didymos is measured from the calibrated frames (see 
data_lcogt_flical_fli collection) using the NEOexchange pipeline. This performs 
source detection in the images using SExtractor (Bertin, E and Arnouts, 
S. 1996. SExtractor: Software for source extraction. A&AS, 117, 393), 
astrometric fits to the detected sources based on the known positions 
of Gaia DR2 stars in the field using SCAMP (Bertin, E. 2006.  Automatic 
Astrometric and Photometric Calibration with SCAMP. ASPC, 351,112), 
photometrically calibrates the zero point of the images based on the 
measured flux of field stars that have known catalog magnitudes 
(from the Gaia-DR2 catalog), and then uses these astrometric and photometric
solutions to derive a calibrated magnitude in 11 apertures (1"..11") for Didymos.
Due to the small field of view and sometime use of short (2s) exposures,
some of the frames did not solve astrometrically. We used custom written
code to propogate the WCS fit and zeropoint by linear interpolation from 
adjacent good frames. The FITS binary table photometry tables included in 
this collection are the output of these pipelines and processing.


The photometry summary table is named according to the following convention: 
lcogt_<site>_<inst.>_<YYYYMMDD>_<request #>_<astname#>_photometry.fits
where:
* <site> is the LCOGT site code as defined in the table below,
* <inst.> is the LCOGT instrument code e.g. ‘ef03’ where the first letter
indicates CCD manufacturer (e=e2v), second letter indicates controller
manufacturer (f=FLI) and the 2 digits indicate serial number,
* <YYYYMMDD> is the date of the start of data collection for that night,
* <request number> is the unique LCOGT (integer) identifier assigned to the observation
request by the LCOGT Observing Portal
* <astname#> is the asteroid name and number in PDS-compatible identifier format i.e. all
lowercase

An example would be lcogt_cpt_ef03_20220926_2956963_65803didymos_photometry.fits
for a photometry file for (65803) Didymos from the ef03 FLI instrument at
Sutherland, South Africa (site code 'cpt') from 2022-09-26.

The LCOGT site codes (which are based on the IATA code of the nearest
airport) are defined as follows:

LCOGT     Site 
Site code location description
--------- -----------------------------------------------------------------
ogg       Haleakala, Maui, HI, USA
coj       Siding Spring Observatory, NSW, Australia
lsc       Cerro Tololo Inter-American Observatory, Chile
cpt       South African Astronomical Observatory, Sutherland, South Africa
elp       McDonald Observatory, Texas, USA
tfn       Teide Observatory, Tenerife, Canary Islands, Spain
ngq       Ali Observatory, western Tibet, China
sin       Meta site for all Sinistro cameras in the network

For these data, due to the time of the DART impact (2022-09-26 23:14 UTC), all
data is from the cpt site and the following telescopes and instruments:
* CPT 1m0 #10 (cpt1m010) telescope and ef02 instrument in Dome A
* CPT 1m0 #13 (cpt1m013) telescope and ef03 instrument in Dome B
* CPT 1m0 #12 (cpt1m012) telescope and ef04 instrument in Dome C

Photometry data are stored as a FITS binary table with the 
following columns:

filename: file name of the calibrated image where data were measured
mjd: Modified Julian Date of the exposure midtime
obs_midpoint: ISO8601 datetime string of the exposure midpoint
exptime: Exposure time (seconds)
filter: Name of the filter used
obs_ra: Observed right ascension of Didymos (degrees)
obs_dec: Observed declination of Didymos (degrees)
flux_radius: Radius of the aperture with 50% of the flux (pixels)
fwhm: Full Width Half Maximum of the frame (arcsec)
mag_aperture_<index>: Magnitude of Didymos in the <index>'th aperture (where <index>=0...10)
mag_err_aperture_<index>:Magnitude error of Didymos in the <index>'th aperture (where <index>=0...10)

References
==========

E. Bertin and S. Arnouts., 1996. SExtractor: Software for source
extraction. A&AS, 117:393–404, June 1996. doi:10.1051/aas:1996164.
E. Bertin., 2006.  Automatic Astrometric and Photometric Calibration
with SCAMP. ASPC, 351:112. 2006ASPC..351..112B
T. Lister, et al, 2021.  NEOExchange - an online portal for NEO and
Solar System science. Icarus, 364, 114387. doi:10.1117/12.2314340
Proceedings of the SPIE, 10707, 107070K. doi:10.1117/12.2314340