Las Cumbres Observatory FLI Raw Data Collection Overview

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 raw images.

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

This collection consists of raw images of the (65803) Didymos system
taken by the Las Cumbres Observatory 1-meter telescope network through
Sloan/PanSTARRS  g' and i' filters plus a broad band clear filter. Note in the
FITS headers, the prime (') is replaced with a ASCII lower case 'p'
e.g. observations in a g' filter will appear as 'gp').

These observations were taken with the FLI instruments which are the 
visible- wavelength, direct-imaging CCD cameras that are normally used 
as autoguiders for the main LCOGT 1-meter Sinistro imagers. Since they 
have a smaller number of pixels and can be readout much faster than the 
Sinistro imagers, the FLI instruments are occasionally used as science 
instruments to capture fast, dynamic phenomena such as that predicted 
for the DART impact event. The FLI imager is a 1k x 1k CCD that images 
a 5.8 arc minute square field of view. The device is back illuminated 
and has 13-micron pixels. The unbinned detector provides a pixel scale 
of 0.340 arcsec/pixel. The instrument can be operated in 1x1 or 2x2 
pixel binning, giving 0.680 arcsec/pixel. The chip is linear up to 65k 
ADU and has dual amplifiers which can readout at either 500 kHz or 
2MHz. Read noise is typically 7.5 electrons with 500 kHz readout and 
16.3 electrons in 2 MHz readout. The readout and processing time is 2.1 
seconds for unbinned images, and 1.78 seconds for the binned 2x2 mode. 
The CCD quantum efficiency is 15% for 300-350 nm, 50% at 400, 90% at 
500 nm, rising to 90-95% over 500-700 nm and declining smoothly to 12% 
at 1000 nm.

The FLI imagers on the Las Cumbres Observatory 1-meter telescope
network acquire data in FITS format. Raw image data includes the
science sky frames, bias and dark frames, and flat fields. Bias and
dark frames are taken during the local site afternoon before sunset and
flat fields were manually scheduled in the days before impact for
those filters that were going to be used for the impact observations. Flat
fields are obtained by taking dithered images of the twilight sky with the
telescope pointed at the point opposite the Sun which minimizes sky
curvature.

Naming Convention
=================

Raw FLI images consist of a single FITS file containing a primary
header and the image data
They are named according to the following LCOGT-wide convention:
<site><tel. class><tel. #>-<instrument>-<yyyymmdd>-<iiii>-<type><red. level>.<extn>
where:

filename section Description
---------------- --------------------------------------------------------------
<site>           LCOGT site code (one from {ogg, coj, lsc, cpt, elp, tfn, ngq})
<tel. class>     Size/class of telescope (one from {2m0, 1m0, 0m4})
<tel. #>         telescope serial number within size class
<instrument>     LCOGT instrument code e.g. ‘ef15’ where the first letter
indicates CCD manufacturer (e=e2v), second letter indicates controller
manufacturer (f=FLI) and the 2 digits indicate serial number.
<yyyymmdd>       UTC date of the start of the night (defined to be UTC
date at 1600 local time at the site). Does not change if the site
observes through UTC midnight.
<iiii>           four digit image counter for that instrument, resets
at start of new night (defined as above). Counter starts at 0001
<type>           Type of file. One of {a=arc, b=bias, d=dark, e=exposure,
s=standard, f=sky flat, l=lambert flat, w=lamp flat, x=experimental})
<red level>      Reduction level from 00-99 with higher numbers
indicating higher levels of data processing. In practice, one of
{00=raw, 91=BANZAI processed, 92=NEOexchange processed}
<extn>           the file extension. ".fits" for fits file format,
".xml" for the PDS label.

e.g. cpt1m013-ef03-20220926-0176-e91.fits is a processed expose(sky)
data product from the SAAO Sutherland Observatory (cpt), from 1-meter
telescope #13 and the ef03 FLI instrument from the night of
2022-09-26. It is the 176th image taken by that instrument on that
night.

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