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Calibration Reference Data System
COS Reference Files

Reference files used by the COS calibration pipeline (CALCOS)) are updated on a regular basis. Current reference files files can be retrieved from the HST archive, or downloaded directly from the lref directory. Note that FTP access is browser dependent: Safari does not work; Firefox or Chrome may or may not work depending on the Operating System. If you cannot download the files via Firefox or Chrome, you can try using a standalone FTP tool or accessing the ftp site directly (ftp with 'anonymous' (without quotes) as your username and your email address as your password.

To retrieve a file from the archive, click in the file name. For details on how to correctly set up the Archive retrieval options for reference files, check our Help page.

To receive e-mail notifications of deliveries of new reference files, you can subscribe to instrument specific mailing lists. More.

New tools for exploring COS Reference Files are now available at https:/ To get a listing of the reference files you're interested in, click on 'cos' then select the filetype. Use the names below in the Header Keyword column as a guide.

Reference File Type Extension Header Keyword Detector
Flat Field Files
Accounts for pixel-to-pixel variations. More...
flat FLATFILE Both
Geometric Distortion Correction Images
Corrects for the intrinsic nonlinearity (INL) of the FUV detector. More...
Bad Time Interval Table
Lists the start and end times of known bad time intervals. More...
Baseline Reference Frame Table
Used when applying the thermal distortion correction. More...
Burst Parameters Table
Provides the parameters needed for deciding when the count rate in some time interval in FUV time-tag data is too high to be regarded as normal. More...
1-D Extraction Parameters Table
Gives the location of the spectrum to be extracted from a 2-D image. More...
Bad Pixel Table
Gives the locations of rectangular regions that cover portions of the detector that are known to be less than optimal. More...
bpix BPIXTAB Both
Deadtime Reference Table
Used to obtain the true number of events received compared to the number of events counted by the detector electronics. More...
dead DEADTAB Both
Dispersion Coefficients Table
Gives a set of polynomial coefficients for computing wavelength from pixel number. More...
disp DISPTAB Both
Calibration Lamp Spectra Table
Used to determine the pixel offset of the observed data. More...
lamp LAMPTAB Both
Pulse Height Parameters Table
Lists the lower and upper thresholds for valid individual pulse heights in TIME-TAG mode as well as the minimum and maximum values for the location of the mean value of the pulse height distribution used in ACCUM mode. More...
Photometric Sensitivity Reference Table
Provides the information needed to convert from corrected detector counts to flux units. More...
phot FLUXTAB Both
Spectroscopic WCS Parameters Table
The spectroscopic WCS parameters table gives values to be used for populating the world coordinate keywords. More...
Time Dependent Sensitivity Table
Gives information about the relative sensitivity as a function of time and wavelength. More...
tds TDSTAB Both
Wavecal Parameters Table
Gives information about the relative sensitivity as a function of time and wavelength. More...
wcp WCPTAB Both
High Voltage Reference Table
The high voltage reference table gives the times when the FUV high voltage was changed More...
Walk Correction Reference Table
The walk corection reference table gives parameters for correcting the pixel coordinates XCORR and YCORR of FUV TIME-TAG data More...
Gain Sag Reference Table
The gain sag reference table gives the locations of rectangular regions for portions of the FUV detector that have very low pulse height amplitude (PHA). More...