This directory contains the calibration data (i.e., captures) for each station of the network, in the format of FITS files automatically acquired by FreeTure each 10 minutes during day- and night-time.
This directory is organized as follows:
captures/
↳ CODE/
↳ YYYYMM/
↳ CODE_YYYYMMDDTHHMMSS_UT-0.fit
[...]
The dataset is subdivided as one directory per each camera, named by the camera CODE (e.g., ITPI01).
Within each one of those, data are organized with one directory for each month of acquisition in the format YYYYMM
(e.g., 201903).
Each capture is named after the station code and the acquisition date-time, in the following convention:
CODE_YYYYMMDDTHHMMSS_UT-0.fit
(e.g., ITPI01_20180100T001054_UT-0.fit).
Captures format
Each capture is saved as a FITS file (or compressed .fit.gz
to save some disk space), enclosing the image itself (grey-scale) and a header with relevant metadata, also automatically produced by the Freeture software.
Captures can be open, visualized and saved as bitmap images with the PRISMA Widget.
An example of capture acquired by the ITPI01 - Pino Torinese camera is given below.
Captures are usually oriented with the North direction corresponding to the negative ordinate axis (downwards, -y) and the East direction to the positive ordinate axis (rightward, +x). In the analysis process, captures are rotated counterclockwise by 90°, to match the reference frame with the North direction corresponding to the positive abscissa axis (+x) and the East direction to the positive ordinate axis (+y).
The FITS header enclosed in each capture file lists the relevant metadata of the acquisition, such as time, coordinates, exposure time and others. An example of such header for the example capture by the ITPI01 - Pino Torinese camera is given below. Among all these keywords, the ones that are mandatory for the PRISMA pipeline are:
-
DATE-OBS
: the acquisition date and time (UTC) in the FITS format; -
EXPOSURE
: the exposure time of the capture (s); -
TELESCOP
: the name of the station.
SIMPLE = T / file does conform to FITS standard
BITPIX = 16 / number of bits per data pixel
NAXIS = 2 / number of data axes
NAXIS1 = 1280 / length of data axis 1
NAXIS2 = 960 / length of data axis 2
EXTEND = T / FITS dataset may contain extensions
FILENAME= 'ITPI01_20200101T000515_UT-0.fit' / name of the fits file
DATE = '2020-01-01T00:05:17.239408' / date of the creation of the fits file
DATE-OBS= '2020-01-01T00:05:15.6125' / acquisition date of the first frame
OBS_MODE= 'SINGLE ' / 'SINGLE' 'SUM' 'AVERAGE' ('MEDIAN')
ELAPTIME= 5. / end obs. date - start obs. date (sec.)
EXPOSURE= 5. / frame exp (sec). 999999 if different exposure.
ONTIME = 5. / total integration time, sum of each frame exp (
FILTER = ' '
TELESCOP= 'Pinotorinese' / station station
OBSERVER= 'd.gardiol'
INSTRUME= 'FRIPON-CAM'
CAMERA = 'DMK23G445'
FOCAL = 1.25
APERTURE= 2.
SITELONG= 7.764939 / geodetic WGS84 longitude (DD)
SITELAT = 45.04124 / geodetic WGS84 latitude (DD)
SITEELEV= 620. / geodetic WGS84 elevation (m)
XPIXEL = 0.
YPIXEL = 0.
GAINDB = 15 / detector gain
SATURATE= 0. / saturated value
PROGRAM = 'FreeTure' / name of the acquisition software
CREATOR = 'FRIPON ' / http://fripon.org
BZERO = 0 /
BSCALE = 1.
RADESYS = 'ICRS '
TIMESYS = 'UTC '
EQUINOX = 2000. / equinox of equatorial coordinates
CTYPE1 = 'RA---ARC' / projection and reference system
CTYPE2 = 'DEC--ARC' / projection and reference system
TIMEUNIT= 's '
CD1_1 = 0. / deg/px
CD1_2 = 0. / deg/px
CD2_1 = 0. / deg/px
CD2_2 = 0. / deg/px
CD3_3 = 0. / fps
CRPIX1 = 640
CRPIX2 = 480
CRVAL1 = 109.202853596831 / sidereal time (decimal degree)
CRVAL2 = 45.04124 / geodetic WGS84 latitude (DD)
K1 = 0. / R = K1 * f * sin(theta/K2)
K2 = 0. / R = K1 * f * sin(theta/K2)
O_BZERO = 32768.0 / Original BZERO Value
END