ZTF Metadata

Quick Links

The tables describing the metadata for ZTF products are:

The ZTF data products themselves are available here, for browsing or for retrieving with an API:

How to locate a ZTF file from its metadata

The path of a ZTF data product file can be deduced from its metadata according to the following rules, where the + signs indicate concatenation and the bolded strings represent metadata columns or strings derived from metadata columns.

Below, year is the first four characters of filefracday, month is characters 5--6 of filefracday, day is characters 7--8 of filefracday, and fracday is characters 9--14 of filefracday.

Science Exposures

File Path Pattern:

'https://irsa.ipac.caltech.edu/ibe/data/ztf/products/sci/'+year+'/'+month+day+'/'+fracday+'/ztf_'+filefracday+'_'+paddedfield+'_'+filtercode+'_c'+paddedccdid+'_'+imgtypecode+'_q'+qid+'_'+suffix

where paddedfield is the field padded with initial zeros to 6 characters, paddedccdid is the ccdid padded with an initial zero to 2 characters; suffix can be any of the following:

  • sciimg.fits (primary science image)
  • mskimg.fits (bit-mask image)
  • psfcat.fits (PSF-fit photometry catalog)
  • sexcat.fits (nested-aperture photometry catalog)
  • sciimgdao.psf (spatially varying PSF estimate in DAOPhot's lookup table format)
  • sciimgdaopsfcent.fits (PSF estimate at science image center as a FITS image)
  • sciimlog.txt (log output from instrumental calibration pipeline)
  • scimrefdiffimg.fits.fz (difference image: science minus reference; fpack-compressed)
  • diffimgpsf.fits (PSF estimate for difference image as a FITS image)
  • diffimlog.txt (log output from image subtraction and extraction pipeline)
  • log.txt (overall system summary log from realtime pipeline)

Example search (for proprietary data, can add --user myemail.astronomy.edu:mypassword after curl):

curl -o out.tbl "https://irsa.ipac.caltech.edu/ibe/search/ztf/products/sci?POS=255.57691,12.28378"

For one entry in the output, the metadata contains:

  • filefracday = '20180411467847'
  • year = '2018'
  • month = '04'
  • day = '11'
  • fracday = '467847'
  • paddedfield = '000535'
  • filtercode = 'zr'
  • paddedccdid = '11'
  • imgtypecode ='o'
  • qid = '3'

Therefore, the URL to the science exposure is:

https://irsa.ipac.caltech.edu/ibe/data/ztf/products/sci/2018/0411/467847/ztf_20180411467847_000535_zr_c11_o_q3_sciimg.fits

Calibration Bias

File Path Pattern:

'https://irsa.ipac.caltech.edu/ibe/data/ztf/products/cal/'+year+'/'+month+day+'/bias/'+filtercode+'ccd'+paddedccdid+'/q'+qid+'/ztf_'+filestartdate+'_'+filtercode+'_c'+paddedccdid+'_q'+qid+'_bias.fits'

Example:

Try the following search in your browser:

https://irsa.ipac.caltech.edu/ibe/search/ztf/products/cal?WHERE=ccdid=11+AND+caltype=%27bias%27&CT=html

The entry of interest has metadata:

  • ccdid = '11'
  • qid = '3'
  • nightdate = '20180411'
  • filtercode = '00'

Therefore, the URL to the bias frame is:

https://irsa.ipac.caltech.edu/ibe/data/ztf/products/cal/2018/0411/bias/00/ccd11/q3/ztf_20180411_00_c11_q3_bias.fits

Calibration High Frequency Flat

File Path Pattern:

'https://irsa.ipac.caltech.edu/ibe/data/ztf/products/cal/'+year+'/'+month+day+'/hifreqflat/'+filtercode+'/ccd'+paddedccdid+'/q'+qid+'/ztf_'+filestartdate+'_'+filtercode+'_c'+paddedccdid+'_q'+qid+'_hifreqflat.fits'

Example:

Try the following search in your browser:

https://irsa.ipac.caltech.edu/ibe/search/ztf/products/cal?WHERE=ccdid=11+AND+caltype=%27hifreqflat%27&CT=html

The entry of interest has metadata:

  • ccdid = '11'
  • qid = '3'
  • nightdate = '20180411'
  • filtercode = 'zr'

Therefore, the URL to the high frequency flat frame is:

https://irsa.ipac.caltech.edu/ibe/data/ztf/products/cal/2018/0411/hifreqflat/zr/ccd11/q3/ztf_20180411_zr_c11_q3_hifreqflat.fits

Raw

File Path Pattern:

'https://irsa.ipac.caltech.edu/ibe/data/ztf/products/raw/'+year+'/'+month+day+fracdate+'/ztf_'+filefracday+'_'+paddedfield+filtercode+'_c'+paddedccdid+'_'+imgtypecode+'.fits.fz'

Example:

Try the following search in your browser:

https://irsa.ipac.caltech.edu/ibe/search/ztf/products/raw?WHERE=ccdid=11+AND+imgtype='object'+AND+filefracday=20180411467847&CT=html

The first entry has metadata:

  • filefracday = '20180411467847'
  • filtercode = 'zr'
  • paddedccdid = '11'
  • paddedfield = '000535'
  • imgtypecode = 'o'

Therefore, the URL to the raw frame is:

https://irsa.ipac.caltech.edu/ibe/data/ztf/products/raw/2018/0411/467847/ztf_20180411467847_000535_zr_c11_o.fits.fz

Currently, the possible values for "imgtypecode" pertaining to raw image data files are:

  • o = science (on-sky); see example above.
  • b = bias calibration image
  • d = dark calibration image
  • f = dome/screen flatfield calibration image

Reference Images

File Path Pattern:

'https://irsa.ipac.caltech.edu/ibe/data/ztf/products/ref/'+fieldprefix+'/field'+paddedfield+'/'+filtercode+'/ccd'+paddedccdid+'/q'+qid+'/ztf_'+paddedfield+'_'+filtercode+'_c'+paddedccdid+'_q'+qid+'_refimg.fits'

Example:

Try the following search in your browser:

https://irsa.ipac.caltech.edu/ibe/search/ztf/products/ref?WHERE=field=000535+AND+ccdid=11+AND+qid=3

The entry of interest has metadata:

  • paddedfield = '000535' which has a field prefix of 000
  • filtercode = 'zr'
  • paddedccdid = '11'
  • qid = '3'

Therefore, the URL to the primary reference image is:

https://irsa.ipac.caltech.edu/ibe/data/ztf/products/ref/000/field000535/zr/ccd11/q3/ztf_000535_zr_c11_q3_refimg.fits

Deep Reference Images

File Path Pattern:

'https://irsa.ipac.caltech.edu/ibe/data/ztf/products/deep/'+fieldprefix+'/field'+paddedfield+'/'+filtercode+'/ccd'+paddedccdid+'/q'+qid+'/ztf_'+paddedfield+'_'+filtercode+'_c'+paddedccdid+'_q'+qid+'_refimg.fits'

Example:

Try the following search in your browser:

https://irsa.ipac.caltech.edu/ibe/search/ztf/products/deep?WHERE=field=000535+AND+ccdid=11+AND+qid=3

The entry of interest has metadata:

  • paddedfield = '000535' which has a field prefix of 000
  • filtercode = 'zr'
  • paddedccdid = '11'
  • qid = '3'

Therefore, the URL to the primary deep reference image is:

https://irsa.ipac.caltech.edu/ibe/data/ztf/products/deep/000/field000535/zr/ccd11/q3/ztf_000535_zr_c11_q3_refimg.fits